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Presentation type:
GMPV – Geochemistry, Mineralogy, Petrology & Volcanology

EGU24-1663 | Orals | MAL22-GMPV | Robert Wilhelm Bunsen Medal Lecture

Exploring the deep Earth and planetary interiors by high-pressure experiments 

Kei Hirose

While the deep Earth is not directly accessible, it can be explored by laboratory experiments under high-pressure and -temperature (P-T) combined with geophysical observations and geodynamical modeling. We conduct experiments using a laser-heated diamond-anvil cell (DAC) which can generate static high P-T beyond conditions at the center of the Earth. Combining such DAC experiments with in-situ X-ray observations at synchrotron sources and thermal/electrical conductivity measurements and ex-situ textural and chemical characterizations of recovered samples, we have been trying to uncover the structures, chemical compositions, physical properties, dynamics, and evolution of the deep Earth and planetary interiors. The lowermost part of the Earth’s mantle, sometimes called the D” layer, have been the most enigmatic region inside our planet, but the discovery of its main constituent crystals of post-perovskite dramatically improved our understanding of this mysterious layer. Recent hot debates on the core include its thermal conductivity and the mechanism of its convection that have sustained the planetary magnetic field since early history of the Earth. In addition, the Earth’s core is known to include substantial amounts of light elements such as sulfur, silicon, oxygen, carbon, and hydrogen, but its exact chemical composition has been highly controversial since Birch (1952). Hydrogen could be one of the important core light elements when considering that a large amount of water may have been delivered to the growing Earth and hydrogen is strongly siderophile (iron-loving) under high pressure. Nevertheless, the phase diagram and properties of iron hydrides are little known since hydrogen is least soluble into iron at ambient conditions. I will introduce these high-pressure studies on the deep mantle and core materials including our recent work on iron hydrides and discuss the possible ranges of Earth’s core composition.

How to cite: Hirose, K.: Exploring the deep Earth and planetary interiors by high-pressure experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1663, https://doi.org/10.5194/egusphere-egu24-1663, 2024.

EGU24-4803 | ECS | Orals | MAL22-GMPV | Arne Richter Awards for Outstanding ECS Lecture

Effects of water on the evolution of the Early Moon and deep Earth investigated by experiments 

Yanhao Lin

The Moon is thought to have been covered initially by a deep magma ocean, its gradual solidification leading to the formation of the aluminium-rich plagioclase-bearing highland crust. We performed the first high-pressure, high-temperature experimental study of the mineralogical and geochemical evolution accompanying the full solidification of a lunar magma ocean (LMO) and provide new constraints on the presence of water in the early lunar interior. In a dry Moon, plagioclase appears after 68 per cent solidification and yields a crust with a thickness of ~68km1, well above the lunar crustal thickness suggested by recent GRAIL mission gravitational data (34–43 km). Water-bearing experiments show a delay in the start and lowering of the volume of plagioclase formed during LMO crystallization, as observed previously for terrestrial magma. Using crustal thickness as a hygrometer we conclude that at least ~800 ppm water was present in the Moon at the time of LMO crystallization, indicating the Earth-Moon system was water-rich from the start2,3.

Water does not only have remarkable effects on early LMO evolution, but also on the properties of Earth’s mantle rocks, however, how and how much transporting water into the deep Earth is still debated due to high mantle temperatures. Subduction of oceanic lithosphere transports surface H2O into the mantle. Recent studies proved that stishovite and post-stishovites as high-pressure phases of SiO2 have the potential to carry weight percent levels of water into the Earth’s interior along the geotherm of the subducting oceanic crust4. Regression of our experimental data indicates an H2O storage capacity in stishovite of ~3.5 wt% in the transition zone and shallow lower mantle, decreasing to about 0.8 wt% at the base of the mantle5. As slabs subducted to the deepmost mantle, dehydration of these dense hydrous silica phases (DHS) can potentially change physicochemical properties of the Earth’s mantle by reducing melting point, forming new high-pressure phases and enhancing the oxygen fugacity heterogeneity of lower mantle6.

References:

[1] Lin Y., Tronche E. J., Steenstra E. S., and van Westrenen W. Experimental constraints on the solidification of a nominally dry lunar magma ocean. Earth Planet. Sci. Lett. 471, 104–116 (2017).

[2] Lin Y., Tronche E. J., Steenstra E. S., and van Westrenen W. Evidence for an early wet Moon from experimental crystallization of the lunar magma ocean. Nat. Geosci. 10, 14–18 (2017).

[3] Lin Y., Hui H., Xia X., Shang S., and van Westrenen W. Experimental constraints on the solidification of a hydrous lunar magma ocean. Meteorit. Planet. Sci. 55, 207–230 (2020).

[4] Lin Y., Hu Q., Meng Y., Walter M. and Mao H.-K. Evidence for the stability of ultrahydrous stishovite in Earth’s lower mantle. Proc. Natl. Acad. Sci. U. S. A. 117, 184–189 (2020).

[5] Lin Y et al. Hydrous SiO2 in subducted oceanic crust and H2O transport to the core-mantle boundary. Earth Planet. Sci. Lett. 594, 117708 (2022).

[6] Lin Y. and Mao H. K. Dense hydrous silica carrying water to the deep Earth and promotion of oxygen fugacity heterogeneity. Matter Radiat. Extremes 7, 068101 (2022).

How to cite: Lin, Y.: Effects of water on the evolution of the Early Moon and deep Earth investigated by experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4803, https://doi.org/10.5194/egusphere-egu24-4803, 2024.

GMPV1 – New and interdisciplinary approaches and applications in geochemistry

Lake Tziscao is one of the water bodies belonging to Lagunas de Montebello National Park, located in the south-southeastern part of the state of Chiapas, Mexico. Its importance lies in its great tourist activity due to its size and nearby human settlement, which is why there are numerous anthropogenic factors that promote the transformation of natural areas within it.

In this work, PHREEQC software was used to perform inverse hydrogeochemical modeling, with which the predominant hydrogeochemical processes of the site were identified and estimated using 20 sampling points distributed along Lake Tziscao.

Prior to the execution of the model, a statistical analysis, simplification and graphic representation of samples, as well as a site analysis were carried out, whose comparison results coincide with the presence of calcic-magnesic bicarbonate type waters, suggesting the feasibility of the proposed model.

Modeling results indicate that the main processes present in the water-rock interaction in the area are: hydration of anhydrite and subsequent dissolution-precipitation of gypsum in large proportion, minimal transfer or equilibrium in carbonate minerals and halides such as calcite, dolomite, sylvite and halite, nonetheless, the concentrations of elements such as nitrogen and phosphorus within the water body suggest anthropogenic pollution sources, while the relatively low salinity indicates that the waters are poorly evolved or have been transported to a lesser extent.

How to cite: González Herrera, C. R. and García Villanueva, L. A.: Identification of hydrogeochemical processes through inverse modeling in PHREEQC in Lake Tziscao, belonging to the Montebello lagoon system in Chiapas, Mexico., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-26, https://doi.org/10.5194/egusphere-egu24-26, 2024.

EGU24-1348 | ECS | Orals | GMPV1.2

Inverse Radius Weighting (IRW) interpolation model: A new interpolation considering morphology 

Behnam Sadeghi, Shaunna Morrison, Ahmed Eleish, and Jens Klump

Geochemical sampling has limitations due to budget constraints and restricted access to certain areas. This results in some regions being unsampled, making it difficult to generate comprehensive geochemical anomaly maps and distinguish between background values and anomalies. To address this, different interpolation models have been developed, such as inverse distance weighting (IDW) and kriging techniques. However, both IDW and kriging only consider the horizontal distance between samples and ignore elevation changes, which is important in real-world terrains. This effect is most pronounced in mountainous terrains. To address this, we propose a new interpolation technique called Inverse Radius Weighting (IRW). IRW factors in both horizontal distance and elevation changes between sample pairs, resulting in more accurate predictions. Detailed elevation data is available for the entire globe in the form of digital elevation maps from the Shuttle Radar Topography Mission (SRTM) and other sources. In this research, both IDW and IRW models were applied to soil samples in Cyprus. A comparative analysis between IDW and IRW models showed that IRW gives more accurate predictions, especially in terrains with complex morphologies. IRW's ability to account for topographical influences makes it the preferred choice in such scenarios.

How to cite: Sadeghi, B., Morrison, S., Eleish, A., and Klump, J.: Inverse Radius Weighting (IRW) interpolation model: A new interpolation considering morphology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1348, https://doi.org/10.5194/egusphere-egu24-1348, 2024.

In regional or local scale geochemical mapping, the choice of sampling media and analytical methods will be influenced by the source, form, mobility and spatial distribution of elements being mapped. For environmental monitoring and mineral exploration there are potential advantages in using plant organs rather than regolith materials as the sampling media, including the capacity of plants to sample large volumes of underlying regolith and the averaging of their biogeochemical composition over timeframes extending from months to years. The limited use of plant organs in geochemical mapping relates partly to perceived complicating factors such as variability between plant species, seasonal variability in some plant organs and analytical costs.

 

Needle samples from over 4,000 cypress pines (C. glaucophylla) in the highly mineralised Cobar Basin in central New South Wales have been analysed by both ICPMS and pXRF. The study spanned regional mapping using samples collected adjacent to roads and tracks, and detailed grids and traverses across 36 mineral prospects and deposits. For various major and trace elements, there is strong correlation between results obtained by total digestion ICPMS and by portable XRF, including direct pXRF analysis of unprocessed samples in the field.

There are distinct lithological influences on variation in the background values for various elements, including Au and Pb, noting that the majority of mineral deposits are structurally hosted within the Devonian sandstone and siltstones regionally intruded by felsic intrusives. There is an extensive zone of elevated base and precious metal values in the needles between the Peak Au mine site and the city of Cobar which was the focus of mineral processing for many decades. Highly elevated values for Ag, Au, Pb, Zn, Ni, Co, W and/or REE occur above known mineral deposits, depending on deposit style, and commonly display more consistent geochemical spatial patterns than in regolith samples. Pines in general typically restrict uptake of Cu in the needles to within the range of 3–12 ppm due to its function as an important trace nutrient.

How to cite: Schifano, J., Cohen, D., and Rutherford, N.: Pining for an Anomaly: Exploration and environmental assessments using regional and local scale biogeochemical patterns in the Cobar Region, Australia., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1404, https://doi.org/10.5194/egusphere-egu24-1404, 2024.

EGU24-1715 | Posters on site | GMPV1.2

Nuclear Forensic of Uranium Ore Materials out of Regulatory Control: The Galaxy Serpent exercise v3 

Chiara Telloli, Giuseppe Ottaviano, Federico Rocchi, Franca Padoani, and Antonietta Rizzo

The nuclear forensics is one of the pillars in the architecture of nuclear security, as a response to criminal acts and illicit trafficking involving nuclear materials or other radioactive materials. ENEA is participating in international table-top exercises organized by the Nuclear Forensics International Technical Working Group (ITWG), a community whose aim is to advance the scientific discipline of nuclear forensics supporting the development of national capabilities. The “Galaxy Serpent” is a set of virtual international web-based exercises, focused on the development of National Nuclear Forensic Libraries (NNFLs). The aim is to increase national awareness of the technical challenges associated with the development of a National Nuclear Forensic Library (NNFL) and how it can be a valuable support for investigating crimes and/or illicit activities involving nuclear or radioactive materials.

The ENEA CBRN team participated in the Galaxy Serpent exercise, version 3, focused on the investigation on imported uranium ore concentrate materials. The used approach, the tools and the main outcomes will be presented. The scenario was dealing with the interception of a transport vehicle attempting to leave the country carrying radioactive materials out of regulatory control (MORC). In fact, further inspection revealed geological sources within some labelled containers and the isotopic analysis performed on these materials determined the sources to be uranium ore concentrate (UOC). The ENEA CBRN team was tasked to check whether this material was consistent with the material used within its country. The assessments have been carried out using Rare Earth Element (REE) patterns as main fingerprint of the geochemical affinity classes. REEs can be used to verify the origin of the samples and some process they have experienced as they are water insoluble and present in very low concentration in water, so they really reflect the original chemistry of the source. In addition, variations in their concentration could be indicative of technological processes aimed at the recovery of some elements that have different high technology applications. The use of statistical tools for the extrapolation of forensic information are presented and discussed.

The exercise had the dual purpose of testing, on the one hand the team’s skill level and the type of tools necessary for a response in the mitigation of chemical, biological, radiological, nuclear and risks (CBRN), and on the other hand, to prepare tools and procedures that may also involve other actors at national level, in particular in response to radiological risk.

How to cite: Telloli, C., Ottaviano, G., Rocchi, F., Padoani, F., and Rizzo, A.: Nuclear Forensic of Uranium Ore Materials out of Regulatory Control: The Galaxy Serpent exercise v3, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1715, https://doi.org/10.5194/egusphere-egu24-1715, 2024.

EGU24-1834 | Posters on site | GMPV1.2 | Highlight

Geochemical occurrence of Pb in soil and road dust from an industrialized urban environment: Fractionation, bioaccessibility and isotopic composition  

Efstratios Kelepertzis, Zacharenia Kypritidou, Vladislav Chrastný, and Michael Komárek

Anthropogenic Pb originated from leaded petrol and high temperature industrial activities is still a major contamination issue to various compartments in the urban environment, including soil and road dust. Human exposure to Pb near Pb-contaminated areas involves incidental ingestion of soil and road dust and inhalation of resuspended solid particles. Volos is a medium-sized industrialized city, located in central Greece, surrounded by steel and cement factories. The geochemical reactivity, fractionation and bioaccessibility (both oral and inhalable) of Pb in selected soil (n=10) and road dust (n=10) samples were investigated through a variety of laboratory chemical methods comprising the dilute HNO3 extraction, the BCR sequential extraction procedure, the simple bioaccessibility extraction test (SBET) and a simulated lung fluid (SLF solution, artificially lysosomal fluid). In addition, the Pb isotopic composition of both total and bioaccessible Pb was determined to identify the Pb sources and examine potential differences of Pb solubilization in terms of its origin when interacting with simulated human stomach and lung fluids.

Lead was found in highly reactive forms in both road dust and soil (medians 83% and 69% of total contents, respectively). The majority of Pb was found to be associated with the sum of the acid soluble (F1), reducible (F2) and oxidizable (F3) fractions (median 72% of total contents for both soil and road dust), indicating that Pb has a high remobilization potential from the solid matrix. The oral bioaccessibility (%) of Pb was higher than the inhalation one (medians 49% and 37% of the total content), respectively), highlighting the soil and dust ingestion as the primary route of Pb exposure. The isotopic analyses of total Pb in soil and road dust (206Pb/207Pb = 1.144 to 1.192) suggest that the predominant anthropogenic Pb source is industrial Pb from the steel plant, with minor contributions of Pb derived from vehicular emissions. Interestingly, we found significant differences in the isotopic ratios between total and bioaccessible Pb (206Pb/207Pb = 1.130 to 1.152), demonstrating that Pb solubilized by the simulated gastric and lung extractions is principally anthropogenic. High Pb bioaccessibilities (%) accompanied a shift towards lower 206Pb/207Pb ratios. Moreover, 206Pb/207Pb ratios of both total and bioaccessible Pb exhibited significantly negative correlations with Pb reactive fractions (%), showing that natural Pb is linked to low Pb release from the soil and road dust matrix. Overall, Pb isotopes provide deep insights into the connection between Pb bioaccessibility and reactivity with Pb sources in soil and road dust from industrial environments.

References

Kelepertzis, E., Chrastný, V., Botsou, F., Sigala, E., Kypritidou, Z., Komárek, M., Skordas, K., Argyraki, A. 2021. Tracing the sources of bioaccessible metal(loids) in urban environments: A multidisciplinary approach. Science of the Total Environment 771: 144827.

 

How to cite: Kelepertzis, E., Kypritidou, Z., Chrastný, V., and Komárek, M.: Geochemical occurrence of Pb in soil and road dust from an industrialized urban environment: Fractionation, bioaccessibility and isotopic composition , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1834, https://doi.org/10.5194/egusphere-egu24-1834, 2024.

EGU24-2817 | Orals | GMPV1.2

Recent advances in flint provenance studies in Israel developed by combining geochemical and statistical perspectives 

Yoav Ben Dor, Meir Finkel, Gonen Sharon, Ofir Tirosh, Oded Bar, and Erez Ben-Yosef

Provenance studies of flint artefacts provide important means for interpreting raw material procurement strategies, which testify to the level of expertise and environmental knowledge of prehistoric people. Due to its importance, different approaches and methods have been used in order to address this topic, which often makes it difficult to compare different studies. During the recent years we have been exploring the potential of bulk rock composition of flint measured using inductively coupled mass-spectrometry (ICP-MS) for provenance studies. Through the systematic sampling of flint from all across Israel (now archived at the Geological Survey of Israel, as part of the developing national flint collection) and the investigation of a large suite of trace elements, we have been developing a robust approach for determining the provenance of flint. By sampling several specimens from each locality and measuring a large array of elements, we additionally address the variability of compositional data in natural rock sources, and develop a statistical framework for evaluating the uncertainty involved in the provenancing of flint. These developments have been applied in recent case studies in key archaeological sites, and shed new light on the old question of flint provenance in prehistory.

How to cite: Ben Dor, Y., Finkel, M., Sharon, G., Tirosh, O., Bar, O., and Ben-Yosef, E.: Recent advances in flint provenance studies in Israel developed by combining geochemical and statistical perspectives, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2817, https://doi.org/10.5194/egusphere-egu24-2817, 2024.

EGU24-4005 | Orals | GMPV1.2 | Highlight

No evidence for large mercury release from the Greenland Ice Sheet: recent conclusions on global mercury budget invalidated.  

Christian Juncher Jørgensen, Jens Søndergaard, Martin Mørk Larsen, Kristian Kjellerup Kjeldsen, Diogo Rosa, Sarah Elise Sapper, Lars-Eric Heimbürger-Boavida, Stephen G. Kohler, Feiyue Wang, Zhiyuan Gao, Debbie Armstrong, and Christian Nyrop Albers

Local glaciers and ice caps in the Northern Hemisphere and the Greenland Ice Sheet (GrIS) have recently been suggested to be important parts of the Arctic mercury (Hg) budget. Based on ice-core data, the recently estimated total glacial Hg pool is approximately 2,400 tons, approximately 97% of which is in Greenland1. With Hg concentrations in pre-industrial ice being significantly lower than in ice formed during the 19th and 20th centuries, the dominating source of glacial Hg and input to the Arctic Hg budget is ascribed to long-range transport of anthropogenic Hg emissions2.

Alarming concentrations of Hg in meltwater from the western margin of the GrIS were recently reported3. With Hg concentrations reported as being 100 - 1000 times higher than what is known for other freshwater systems of Greenland and a postulated increase in Hg export to downstream environment following climate warming and asserted global importance of Hg fluxes from the GrIS, these extraordinary concentrations and conclusions calls for independent verification.

In our current study4, we expand the sampling of subglacial meltwater from 21 representative outlets at GrIS in 2021 and 2022 to get a better scientific basis for conclusions on the magnitude of glacial Hg sources in Greenland. Results from our study consistently show that both total and dissolved Hg concentrations in glacial meltwater over space and time are very low (generally <10 pM) and that an extremely elevated Hg concentration range (up to 4000 pM recently reported3) cannot be reproduced.

In contrast to what was previously reported3, we find that meltwater from below the GrIS is very low in Hg; has minor implications for the global Hg budget and pose only a very limited risk for local communities and the natural environment of Greenland.

 

References:

  • A. Dastoor, et al. (2022), Arctic Mercury Cycling. Nature Reviews Earth & Environment 3, 270–286 (2022). https://doi.org/10.1038/s43017-022-00269-w.
  • AMAP. AMAP Assessment 2021: Mercury in the Arctic. Arctic Monitoring and Assessment Programme (AMAP),1- 324.
  • J. R. Hawkings et al (2021) Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet. Nature Geoscience 14, 496–502 (2021). https://doi.org/10.1038/s41561-021-00753-w.
  • Jørgensen et al (2024) Large mercury release from the Greenland Ice Sheet invalidated. Science Advances, in press.

How to cite: Jørgensen, C. J., Søndergaard, J., Larsen, M. M., Kjeldsen, K. K., Rosa, D., Sapper, S. E., Heimbürger-Boavida, L.-E., Kohler, S. G., Wang, F., Gao, Z., Armstrong, D., and Albers, C. N.: No evidence for large mercury release from the Greenland Ice Sheet: recent conclusions on global mercury budget invalidated. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4005, https://doi.org/10.5194/egusphere-egu24-4005, 2024.

EGU24-4708 | Orals | GMPV1.2 | Highlight

Lessons learned from the maintenance of ancient aqueducts through their carbonate archives 

Gül Sürmelihindi and Cees Passchier

The study of ancient aqueducts shows us how past societies used water resources such as rivers, lakes, springs and groundwater. Such resources were tested for their quality, captured, sometimes diverted or abandoned, or supported by a new source. The efficient management of ancient water supply systems was adapted to societal needs, to the chosen environment and to change in climate and population dynamics, similar to factors shaping our modern water management. The in-situ carbonate deposits of ancient water supply systems reflect characteristics of the water resources and aquifers used, and therefore constitute an archive with considerable research potential, particularly for better understanding of ancient water management, palaeo-environment, and water scarcity.

            Ancient aqueducts were long-lived structures, with recorded operation periods of up to 800 years such as the more than 400 km long Valens aqueduct of Constantinople. However, carbonate sequences are often shorter because of cleaning. The Valens aqueduct has a double channel to allow cleaning without interruption of the water supply, and shows only 27 years of carbonate deposits. A carbonate sequence of 250 years is documented for the ancient city of Nemausus, which correlates with the actual documented years of operation. This is because some aqueducts were built wide enough to allow smooth operation without being cleaned of carbonate for most of their length. The aqueduct of Arelate was modified by reallocation of branches and expansion, probably in response to increasing and changing demand of water. In at least 50 years of carbonate stratigraphy, this aqueduct shows periodic variations in the aquifer.

            As the focus of this paper we discuss the Roman aqueduct of Divona, which shows evidence of regular cleaning, repairs, modifications and even timing of maintenance, captured in aqueduct carbonate. The d18O profile of the carbonate stratigraphy shows a cyclicity that is inferred to reflect annual water temperature variations in the channel. This cyclicity was used to determine the timing of maintenance. The aqueduct operated for centuries but the preserved profile shows 88 years of operation, interrupted by two plaster repair events, representing time breaks in water supply of at least several months. Not less than 14 carbonate removal events were recognized, which took place in fall, spring, or winter but never in summer, with an interval of 1 to 5 years. Carbonate removal from channels was done rapidly, in less than one month, since stable isotope cycles show no indication of a long-term interruption in the water supply. The last maintenance was done only three years before the final abandonment of the water supply, showing that continued operation of the aqueduct was planned but was not fulfilled. This micro-story shows how a historical water management operated and adapted to water scarcity and population growth and decline, similar to modern days. Frequent cleaning of aqueduct carbonate and repairs are examples of what we call today “sustainable” water management.  

Ancient aqueducts carbonates are models to study aspects of past water management and adaptations to crisis, and provide a vision for the future of water availability and climate change.

How to cite: Sürmelihindi, G. and Passchier, C.: Lessons learned from the maintenance of ancient aqueducts through their carbonate archives, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4708, https://doi.org/10.5194/egusphere-egu24-4708, 2024.

EGU24-5724 | ECS | Orals | GMPV1.2

Provenance Analysis of Zeus/Owl bronze Coins from Velia: A Comprehensive Study using ICP-MS and TIMS Techniques 

Isabella Ercoles, Francesca Castorina, Stefano Nisi, Federico Carbone, Giacomo Pardini, and Pier Renato Trincherini

The project focuses on a provenance study carried out on Zeus/Owl bronze coins, coming from the Greek colony of Velia in southern Italy, and dating back to the 3rd century BC. Chemical elemental composition and lead isotope analyses were carried out at the Laboratori Nazionali del Gran Sasso-INFN by using ICP-MS (Inductively Coupled Plasma Mass Spectrometry) and TIMS (Thermal Ionization Mass Spectrometry) techniques. Lead isotope ratios of the coin samples were compared with data from various ore deposits in the main Mediterranean areas documented in existing literature. Additionally, the elemental composition was examined to establish distinctive geological characteristics aiding in identifying the provenance sources of the studied coins. The majority of the coins exhibited an isotope signature of the lead, that makes up the alloy, overlapping with multiple clusters in the Aegean Greece area (Syros, Kea, Antiparos, Serifos and Sifnos) and the Spain South-East area (Cartagena-Mazarron and Almeria). Six coins displayed an uncertain provenance, suggesting the possibility of mixing and/or metal recycling. Notably, one coin demonstrated overlap with both Spain South-East and Tuscany clusters, indicating a shared provenance probability. Regarding the results of the elemental analysis, the main elements that make up the coins alloy are copper, lead and tin. The Pb content ranges considerably from a minimum of 0.5% to a maximum of 24.9%, while the concentration of Cu ranges from a minimum of 73.3% to a maximum of 93.5% and that of Sn ranges between 1.7% and 10.3%. This information contributes to the reconstruction of historical trade routes, enhancing our understanding of the dynamics of metal supply and socio-economic relationships in Velia.

Keywords: Provenance study; Isotopes; Ancient Coins; Ore Deposit; TIMS

How to cite: Ercoles, I., Castorina, F., Nisi, S., Carbone, F., Pardini, G., and Trincherini, P. R.: Provenance Analysis of Zeus/Owl bronze Coins from Velia: A Comprehensive Study using ICP-MS and TIMS Techniques, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5724, https://doi.org/10.5194/egusphere-egu24-5724, 2024.

EGU24-6499 | Posters on site | GMPV1.2

Isotopic and functional markers for the assessment of territoriality: the case study of Asparago di Altedo PGI in the province of Ferrara (NE Italy) 

Elena Marrocchino, Elisabetta Aliprandi, Angela Martina, Renzo Tassinari, and Lorenzo Ferroni

Consumers' growing attention on food composition, quality and origin has sparked a renewed interest in food traceability. The use of isotopic markers of territoriality helps emphasize the connection between agricultural products and their specific geographical area of origin, linked both to the soil-to-plant continuity of elemental composition and to contribution from airborne substances assimilated directly by the shoot. Asparago di Altedo PGI is an exclusive product of the Eastern area of Emilia-Romagna region, between Via Emilia and the Adriatic coast. Sandy-based territories favour the emergence of asparagus turions but include significant variations from sandy-clayey loam soils to lean sandy soils, forming a gradient from the inland to the coast. This research aims to detect a potential asparagus diversification driven by soil and environmental characteristics in the province of Ferrara, useful for further defining the product's typicality with respect to the area of origin. For the selected fields (Malborghetto, Mezzano, Bosco Mesola, Mesola, Lagosanto, Volania, Valli Basse), soil and plant sampling took place from May to the early days of June 2023. As an outgroup, samples of common green asparagus cultivated in Abruzzo region (Central Italy) were collected. The turions were transported to the laboratory for analyses of the fast chlorophyll fluorescence induction, a non-destructive near-instantaneous method for physiological plant assessment. Subsequently, soil and asparagus samples were dried and powdered for isotopic analyses. Soil diversification was characterized through pH and chemical analysis of major and trace elements using X-ray fluorescence. To assess the influence of the environment/soil on asparagus, δ13C and δ15N isotopic ratios, as well as the C/N ratio, were analyzed on soils and plants using an elemental analyzer associated with an IRMS spectrometer. PCA analysis showed that the soils could be distinguished based on geochemical factors and, for some fields, even at a resolution of a few tens of kilometres. For instance, the abundance of Na2O separated the coastal fields from those of inland, and the soil samples of the Malborghetto field stood out from the others due to a higher concentration of certain heavy metals (Cr, Ni, Pb). Soil diversification was also attributable to anthropic interventions in the reclamation of the lagoon areas in some parts of the Ferrara province. An interesting correspondence was found between soil diversity and chlorophyll fluorometric parameters. In particular, although the photosynthetic functionality of the plants was very good in all fields, it was possible to distinguish the asparagus samples based on their origin: for example, the most performing asparagus was from Mesola regardless of the cultivar. Work is still in progress to get a more complete picture of the soil-to-plant continuity in relation to the environmental characteristics of the examined fields.

How to cite: Marrocchino, E., Aliprandi, E., Martina, A., Tassinari, R., and Ferroni, L.: Isotopic and functional markers for the assessment of territoriality: the case study of Asparago di Altedo PGI in the province of Ferrara (NE Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6499, https://doi.org/10.5194/egusphere-egu24-6499, 2024.

EGU24-8265 | Orals | GMPV1.2

Deciphering Middle-Late Pleistocene environmental changes: a multidisciplinary approach to Middle Dnieper loess-palaeosol sequences 

Maria Łanczont, Przemysław Mroczek, Maryna Komar, Jerzy Nawrocki, and Karol Standzikowski

Our research presents a thorough analysis of climatic and environmental transformations in the Central Dnieper Basin (CDB) during the Middle and Late Pleistocene. It focuses on the study of glacial features left by the Dnieper lobe of the Saalian ice sheet and the co-occurring loess covers, as expressions of Pleistocene climatic fluctuations and landscape changes.
The research includes a detailed analysis of loess distribution, revealing a clear contrast between isolated loess patches in the northern lowlands and a continuous, thick loess cover in the south, especially from the latitude of Kyiv. These covers contain well-developed paleosols, reflecting interglacial changes, which form the basis for deep chronostratigraphic correlations on a regional and supra-regional scale. A key element of the study is resolving unresolved stratigraphic issues of the Pleistocene in Ukraine, with particular emphasis on the chronostratigraphic position of loess and paleosol units in the context of global climatic stages.
The main aim of the research is to identify local environmental influences on recorded Quaternary events following the deglaciation of the Dnieper lobe, to reconstruct the interactions between landscape changes post-glacial retreat and aeolian systems, and to establish a comprehensive and reliable stratigraphy for the Quaternary deposits of the Central Dnieper area. The methodology includes the application of a wide range of multidisciplinary techniques, including detailed grain size distribution and chemical composition analysis, advanced colourimetric measurements, paleomagnetic studies and luminescence dating. The research is based on original and older (palynological) studies on the Pleistocene, highlighting the importance of loess-palaeosol sequences in reconstructing the environmental history of the region.
The CDB, located at the juncture of the Dnieper Upland and Dnieper Lowland, provides unique insights into glacial, fluvial, and loess accumulation. Research includes detailed lithological and pedological sediment characterizations at key geological sites. Results of laboratory analysis clarify transport, deposition, and transformation processes of glacial and aeolian materials, indicating significant loess autochthony. Thermal and precipitation data from pollen analysis of mineral-soil sediments highlight the climatic condition's spatial and temporal variability in the CDB. Biome analysis shows varied landscape mosaics in each cycle, with no total deforestation in climatic pessima or complete afforestation in interglacial optima. These findings offer new insights into the CDB's complex Pleistocene stratigraphy, evidencing the last ice sheet's advance in the Dnieper valley during MIS8, and its link to ana- and kataglacial L3 loess sedimentation phases. They also emphasize the local variability and diversity of soil cover evolution and transformation after the glacial retreat, influenced by the post-glacial topography.
Our research significantly broadens the understanding of environmental changes in the Middle and Late Pleistocene in the CDB, contributing to the development of stratigraphic models and paleoenvironmental reconstructions on both regional and global scales.
Research carried out as part of the grant of National Science Centre, Poland as the project no. 2018/31/B/ST10/01507 entitled “Global, regional and local factors determining the palaeoclimatic and palaeoenvironmental record in the Ukrainian loess-soil sequences along the Dnieper River Valley – from the proximal areas to the distal periglacial zone”.

How to cite: Łanczont, M., Mroczek, P., Komar, M., Nawrocki, J., and Standzikowski, K.: Deciphering Middle-Late Pleistocene environmental changes: a multidisciplinary approach to Middle Dnieper loess-palaeosol sequences, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8265, https://doi.org/10.5194/egusphere-egu24-8265, 2024.

EGU24-9041 | ECS | Posters on site | GMPV1.2 | Highlight

Lithium geochemical traceability: development of a multi-criteria approach using on-site and laboratory technologies for the implementation of a battery digital product passeport 

Alban Moradell-Casellas, Anne-Marie Desaulty, Daniel Monfort-Climent, Sebastien Perret, Catherine Guerrot, Wolfram Kloppmann, Nicolas Lafaurie, Nicolas Gilardi, Sylvain Delchini, Nicolas Maubec, and Maria dezes

Transition from fossil fuels to renewable energies is key to reduce human CO2 emissions, in order to cope global warming. As well as the need of technological progress, this raise the needs for metal resources. Some commodities are likely to experience very strong growth of their demand over the coming decades such as Lithium (Li), Aluminum (Al), Cobalt (Co), Nickel (Ni), Copper (Cu), and Rare Earth Elements (“REE”), due to their uses in “green” energy technologies.

The EU-funded “MADITRACE” project aim for the development of traceability methods and certification systems for four critical raw material (CMR): lithium, graphite, cobalt and REEs, in order to integrate sustainable provenance of materials into a Digital Product Passport (DPP) for batteries and vehicles. In the particular case of lithium, a previous study has shown that the deposit type -‘Hard rock’ or Salar- origin of a lithium material can be tracked through the supply chain up to the battery using lithium isotopic analysis1. Nevertheless, some processes can affect this signature. In addition, these analyses requires high-cost instruments and are time-consuming. In order to verify in the future the provenance of a batch of raw material, traceability tools must be resilient to processes and mixing. They should also be more democratized and faster to set-up.

In this regard, the project focuses on the development of the combination of rapid and easy-to-use on-site analysis for routine screening as well as laboratory verification in case of anomalies during the provenance verification of a lithium product. This relies on conventional geo-physico-chemical analysis such as mineralogy, major and trace element compositions, as well as isotopic analysis. The methods investigated includes hyperspectral spectroscopy, IR spectroscopy, LUXREM (XRF-XRD coupling, in development) as well as conventional X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD), Laser Induced Breakdown Spectroscopy (LIBS), (Laser Ablation) Inductively Coupled Plasma Mass Spectrometry ((LA)-QQQ-ICP-MS), (Laser Ablation)  Multi-Collector Inductively Coupled Plasma Mass Spectrometry ((LA)-MC-ICP-MS) and Thermal Ionization Mass Spectrometry (TIMS).

 

  • Desaulty, A. M. et al. Tracing the origin of lithium in Li-ion batteries using lithium isotopes. Nat Commun 13, (2022).

 

How to cite: Moradell-Casellas, A., Desaulty, A.-M., Monfort-Climent, D., Perret, S., Guerrot, C., Kloppmann, W., Lafaurie, N., Gilardi, N., Delchini, S., Maubec, N., and dezes, M.: Lithium geochemical traceability: development of a multi-criteria approach using on-site and laboratory technologies for the implementation of a battery digital product passeport, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9041, https://doi.org/10.5194/egusphere-egu24-9041, 2024.

The Almadén mercury mining district, located in South-central Spain, has been the most important producer of this element worldwide, until the cessation of exploitations in year 2003. The environmental consequence of this activity affects an area of some 250 km2, coincident both with a geological structure (the Almadén syncline) and a river basin (the Valdeazogues river and tributaries). The old cinnabar (HgS) mines and mineral showings are scattered in the syncline and in the basin, favouring a wide distribution of the elements in the soils and sediments, as reported by previous publications from this research group and partners.

Crayfish (Procambarus clarkii) is an exotic river crab, with has replaced the autochthonous one  (Austropotamobius pallipes) due to its voracity. It is very common all along the Valdeazogues river and tributaries, and it is captured and consumed by local population in summertime, when it is easily captured in the ‘tablas’, water accumulated in river pods during the cessation of water running due the stational drought. Preliminary data on the Hg contents in this species, obtained in year 2005 reach up to 9,060 ng g-1 (in muscle) and 26,150 ng g-1 (in hepatopancreas), according to some previous publications of this research group.

In this communication we present new data on this issue, obtained during the year 2022 along the Valdeazogues river and in some of its tributaries. In this research, 330 crayfish (sizes between 7 and 12 mm) were captured from upstream of the El Entredicho open pit mine to downstream of the confluence with the Guadalmez river (about 36.3 km), as well as the Los Álamos stream, and the Azogado stream, both tributaries of the Valdeazogues. All specimens were analysed by Zeeman effect atomic absorption spectrometry.

The overall results showed maximum values of 3,567 ng g-1 of total Hg in muscle tissue, with a mean value for the district of 1,617 ± 920 ng g-1. In hepatopancreas which is an organ of the digestive tract with functions of absorption and storage of nutrients, as well as synthesis of digestive enzymes, the maximum value is very similar: a maximum of 3,590 ng g-1, while the mean is slightly lower, 1,025 ± 1,028 ng g-1. For the whole population, the relationship of Hg content in muscle tissue and hepatopancreas with size is not appreciable, probably because they are organisms of fast grown, and there is no general relationship between age and size. On the other hand, there is a relationship between Hg in hepatopancreas and salts contents and total Hg concentration in the nearby sediments.

How to cite: Higueras, P., Barquero, J. I., Bakale, F., Esbrí, J. M., and García Ordiales, E.: Bioaccumulation of mercury in muscle tissue and hepatopancreas in red crayfish (Procambarus clarkii) in a transect of the Valdeazogues river and tributaries, Almadén Hg mining district, south central Spain. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9369, https://doi.org/10.5194/egusphere-egu24-9369, 2024.

EGU24-9549 | ECS | Posters virtual | GMPV1.2

Remediation of mercury-polluted soil in a mining area using nanoscale zero-valent iron 

Diego Baragaño, Lucía López-Toyos, Laura Simonelli, Maria Antonia López-Antón, and Gildas Ratié

Asturias, located in northern Spain, is a region with a rich history of mining and metallurgical activities intertwined with coal and metals. The Hg-mining district situated in the centre of this region was the Spain’s second-largest Hg manufacturer from 60s to 70s. Several areas were affected by the presence of Hg, specifically in the “El Terronal” mine, which stands out as one of the most affected areas, primarily due to mining and subsequent pyrometallurgical processing.

A pilot-scale remediation using nanoscale zero-valent iron (nZVI) was conducted on a soil plot with a Hg concentration of 1500 mg/kg in “El Terronal”. The nZVI proved to be an exceptional amendment for Hg immobilization, revealing an 86% reduction in Hg mobility within 72 hours of applying the nZVI, sustained over a period of 32 months. Nevertheless, the long-term effects and mechanisms of Hg remediation remain not fully understood. In light of this, the present work focused on elucidating Hg speciation changes 6 years after the application of nZVI in a Hg-polluted soil under field conditions.

Soil samples were taken from both the treated plot and an adjacent untreated plot before nZVI application and after 6 years. Initially, a simplified USEPA Method 3200, involving sequential extraction, was used to evaluate the Hg mobility. Subsequently, the identification of Hg species was conducted using a mercury temperature programmed desorption (HgTPD) device. Based on preliminary results, the reference database for mercury compounds in this work were HgO, cinnabar (HgS), metacinnabar (HgS), HgCl2, HgSO4, corderoite (Hg3S2Cl2), Hg complexed to humic acid, and Hg adsorbed to goethite. Furthermore, X-ray absorption spectroscopy was employed to complement the study of mercury speciation. In this regard, soils and patterns were prepared as pellets from finely ground and homogenized powder. The Hg LIII-edge spectra XANES were collected in transmission and fluorescence modes at 70-80 K on CLAESS beamline (ALBA synchrotron).

The concentration of Hg in the mobile fraction was below detection limit in both samples, treated and untreated soils. However, a decrease on the semi-mobile fraction was found from 57% to 39% in the treated soil with nZVI respect to the untreated soil. This result is in accordance with the Hg immobilization reported at the beginning of the field remediation. With respect to HgTPD, the Hg species identified corresponds to Hg bound to S. On the other hand, the data treatment by linear combination fits of the Hg LIII-edge spectra XANES demonstrated that the Hg solid speciation in the treated and untreated soil samples is similar, mainly dominated by cinnabar, metacinnabar, and Hg adsorbed to goethite. This result, may indicate that the Hg mobile is associated to a minor phase, not quantifiable, or to a Hg immobilization from all phases without preference.

In summary, the mobility of Hg is linked to only a minor fraction of the total concentration of these elements in the soil, with this metal being predominantly associated with cinnabar, metacinnabar and goethite. Consequently, the complete observation of the effects of immobilization processes on Hg speciation was hindered by resolution limitations.

How to cite: Baragaño, D., López-Toyos, L., Simonelli, L., López-Antón, M. A., and Ratié, G.: Remediation of mercury-polluted soil in a mining area using nanoscale zero-valent iron, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9549, https://doi.org/10.5194/egusphere-egu24-9549, 2024.

EGU24-10434 | ECS | Orals | GMPV1.2

Mercury speciation in soils through thermo-desorption technique as a rapid screening tool for risk assessment procedure at mercury-contaminated sites 

Federico Floreani, Elena Pavoni, Elisa Petranich, Paolo Antonini, Mara Mauri, and Stefano Covelli

A key aspect for the evaluation of environmental and health risk associated with mercury (Hg) contamination is the assessment of its speciation, which can influence the mobility and bioavailability of this element in the environment. The evaluation of Hg speciation in soils and sediments of contaminated sites is commonly based on selective sequential extraction (SSE) methods, which, however, have certain disadvantages: they do not allow for a specific removal of Hg species, are generally time-consuming and characterised by a low reproducibility. An easy-to-use alternative to SSE may be represented by thermo-desorption (TD) technique, where different Hg species can be identified according to their specific release temperature during a gradual heating. The aim of this study was to evaluate the potential application of TD for the risk assessment associated with Hg occurrence in alluvial soils at some sites in the Friuli-Venezia Giulia Region (NE Italy) affected by past Hg inputs related to mining and, to a lesser extent, industrial activities. At each site, surface and deep soil samples (n≥12) were collected and analysed for total Hg concentration and Hg speciation through TD. Speciation analyses were performed by means of a Hg atomic absorption spectrometer (Lumex RA915M) coupled with a pyrolysis attachment (PYRO-915+). This setup allows for a continuous monitoring of Hg released during the sample heating. Calculations of risk associated to Hg volatilisation, leaching, and ingestion were performed using the relative amount of non-cinnabar (non-α-HgS) compounds determined through TD, considered as potentially mobile. Results were then compared with those obtained through the application of a SSE method commonly used for the assessment of Hg speciation in the investigated area. Almost all samples analysed through TD showed the occurrence of non-mobile red cinnabar (α-HgS), confirming the remarkable legacy of the mining source. Generally, although a slightly higher abundance of potentially mobile Hg forms was obtained through TD than SSE, the calculated risk resulted “acceptable” (hazard index < 1) using data from both techniques. Besides, it must be stressed that calculation performed through TD data are based on a larger number of samples, thus providing a greater representativeness of the mobility of the Hg species and associated risk in the investigated area. Considering also the good reproducibility of data obtained through TD and its celerity and accuracy in Hg species discrimination, the proposed approach could be considered as a valid and relatively low expensive tool for risk assessment at Hg contaminated sites. This is especially true for sites such as former Hg mining areas characterised by the occurrence of α-HgS, easily discriminable through TD.

How to cite: Floreani, F., Pavoni, E., Petranich, E., Antonini, P., Mauri, M., and Covelli, S.: Mercury speciation in soils through thermo-desorption technique as a rapid screening tool for risk assessment procedure at mercury-contaminated sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10434, https://doi.org/10.5194/egusphere-egu24-10434, 2024.

EGU24-10879 | Orals | GMPV1.2

Investigating the 3D distribution of GEM (Gaseous Elemental Mercury) in the lower atmosphere via a UAV (Unmanned Aerial Vehicle) - Lumex® assemblage 

Jacopo Cabassi, Marta Lazzaroni, Luciano Giannini, David Mariottini, Barbara Nisi, Federica Meloni, Daniele Rappuoli, and Orlando Vaselli

The occurrence of gaseous mercury pollution has to be identified and monitored through innovative methods and techniques, which would serve as a step toward strengthening the knowledge of the mechanisms of mercury dispersion in the atmosphere, in accordance with the provisions of the Minamata Convention on Mercury. Consequently, the aim of this work is to present the very first data obtained by directly and continuously measuring GEM (Mercury Elemental Gas) in the lower atmosphere through an original assembly of a UAV (Unmanned Aerial Vehicle, a heavy-lift octocopter) and a Lumex® RA-915M (a portable spectrometer for gaseous mercury). A few sites pertaining to both the mining facilities of the former Hg-mining area of Abbadia San Salvatore (Mt. Amiata, Italy) and the surrounding urban zones were selected to test the performance and effectiveness of the UAV-Lumex® combination at different heights. The octocopter agility and directional versatility, able to stop at selected altitudes, and the Lumex® great sensitivity made it possible to shed light on the variability of GEM concentrations and to represent its distribution via dot-map graphical visualization, providing a tridimensional picture of GEM profiling during the flights. This approach allows checking in near real-time whether the guideline concentrations are eventually exceeded. More specifically, the acquisition system was optimized through: i) the use of a stand-alone GPS as a synchronization tool for Lumex® and UAV GPS data; ii) the connection of a vertical sampling tube to the Lumex® inlet to overcome the strong airflows of the UAV rotors; iii) the use of batteries for power supply to avoid the release of exhaust gases. Moreover, all flights were standardized based on previously acquired data thanks to the method accuracy and the UAV pilot experience, allowing reprogramming and repeating the routes in different times. The results showed significant concentration variations between the urban and the most contaminated mining area, and highlighted the differences when the flight was repeated at a later date.

How to cite: Cabassi, J., Lazzaroni, M., Giannini, L., Mariottini, D., Nisi, B., Meloni, F., Rappuoli, D., and Vaselli, O.: Investigating the 3D distribution of GEM (Gaseous Elemental Mercury) in the lower atmosphere via a UAV (Unmanned Aerial Vehicle) - Lumex® assemblage, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10879, https://doi.org/10.5194/egusphere-egu24-10879, 2024.

EGU24-10952 | ECS | Posters on site | GMPV1.2

Geochemical-isotopic and fluorimetric analyses for the characterization of two red chicory varieties in sandy coastal soil of the Ferrara province (Italy) 

Angela Martina, Antonello Aquilano, Lorenzo Ferroni, and Elena Marrocchino

The concept of Terroir, developed with respect to grape and wine, can be generalized to define the inseparable link between an agri-food product and its territory of origin as a determining element for its economic valorisation. While the terroir certainly impacts on physiological and compositional aspects of a crop, an important influence is due to the species diversification in cultivars. Therefore, both environment/soil and cultivar participate in defining the geographical authenticity of crops.

Geochemical-isotopic techniques are a powerful tool to authenticate a crop with respect to its geographical origin. The integration of multi-elemental analyses with the determination of isotopes such as carbon (δ13C) and nitrogen (δ15N) can allow a detailed mapping of the geographical origin of agricultural products. The stable isotopes of light elements present in crops offer a unique form of ‘isotopic signature’ that reflects the geochemical conditions of the soil together with the metabolic specificity of the plants (photosynthesis, N assimilation). This is crucial not only to authenticate the plant provenance, but also to support protected designations of origin (PDOs) and geographical indications (PGIs), strengthening the consumer’s confidence in the authenticity and quality of products.

In this first report, we have combined geochemical-isotopic and chlorophyll fluorimetric analyses of two red chicory (“radicchio rosso”, cv. Chioggia and cv. Treviso) cultivars typical of the Emilian coastal environment, but not yet recognized as PGI, different from analogous crops in Veneto Region. An effort in this respect is motivated by the special geochemistry of sandy coastal soils, which tend to be dry and exposed to salinisation phenomena.

Soil was thoroughly characterized based on its chemical-physical properties, including XRF analysis of major elements. A detailed analysis of elements in soil and plants was performed by ICP-MS-QQQ down to ultra-trace elements, and EA-IRMS analysis was done for the evaluation of C and N isotopic ratios. Plant phenotyping, based on chlorophyl fluorescence indexes, was performed to highlight the physiological specificities of the two cultivars, to put in relation with the stable isotope profile of light atoms.

The comparative results of the geochemical composition of the plant organs evidenced a cultivar-specific fractionation of some elements: cv. Chioggia had higher element absorption capacity than cv. Treviso, and both cultivars share an attitude to concentrate P, Cu and Mo. Upon translocation of elements from roots to leaves, especially the rare earth elements showed the specificity of the two cultivars, which can be differentiated based on the concentration of lanthanides as compared to the soil. A better use of mineral nutrients could be supported by higher photosynthetic performance in cv. Treviso than cv. Chioggia.

This research, to be further implemented, can constitute a useful database for the reconstruction of the geochemical-isotope profile for the geographical traceability of “radicchio rosso” and the possible further promotion of this crop in Ferrara province.

 

This research was allowed by phD fellowship granted by EUROPEAN SOCIAL FUND P L U S - The ESF+ 2021-2027 Programme of the Regione Emilia Romagna

 

How to cite: Martina, A., Aquilano, A., Ferroni, L., and Marrocchino, E.: Geochemical-isotopic and fluorimetric analyses for the characterization of two red chicory varieties in sandy coastal soil of the Ferrara province (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10952, https://doi.org/10.5194/egusphere-egu24-10952, 2024.

EGU24-14481 | ECS | Posters on site | GMPV1.2

Experimental Investigation of Lithium Partitioning among Plagioclase, Rhyolitic Melt, and H2O Vapor 

Maylis Dupont de Dinechin, Caroline Martel, Hélène Balcone-Boissard, Monika Rusiecka, Remi Champallier, and Etienne Deloule

Volcanic eruptions are unpredictable and present a significant challenge for volcanic crisis management, primarily due to the variety of eruptive styles, ranging from effusive to explosive. By elucidating the dynamics of magma ascent, with a focus on degassing, we can better understand of the interconnections between petrological characteristics, geochemical and geophysical signals, volcanic hazards, and volcano monitoring. To this aim, lithium (Li), which has a high mobility in both silicate melts and crystals, has been used as a geospeedometer to monitor short-time processes, such as syn-eruptive magma ascent and degassing and post-eruptive processes (cooling). Yet, to appropriately interpret Li data in crystals from volcanic deposits, a clear understanding of the Li behavior and partitioning between the crystal-melt-fluid phases during an eruption is essential. Most of the Li partitioning data rely on glass inclusions and their host minerals, which do not always guarantee equilibrium conditions. Experimental data are largely missing, especially in the case of silica-rich hydrated magmas. Therefore, we provide Li contents and partitioning via phase-equilibrium experiments for analyzable-sized plagioclases crystallized from Li-bearing H2O-saturated rhyolitic melts at pressures from 50 to 150 MPa and temperatures of 800 and 875 °C. In addition to its applications in volcanology, this research could yield valuable information for assessing the economic viability of lithium in felsic deposits, specifically those with rhyolitic/granitic compositions (as highlighted by Benson et al., 2017), and in magmatic fluids. Moreover, it holds futuristic potential for extracting lithium directly from these fluids.

How to cite: Dupont de Dinechin, M., Martel, C., Balcone-Boissard, H., Rusiecka, M., Champallier, R., and Deloule, E.: Experimental Investigation of Lithium Partitioning among Plagioclase, Rhyolitic Melt, and H2O Vapor, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14481, https://doi.org/10.5194/egusphere-egu24-14481, 2024.

EGU24-15658 | ECS | Orals | GMPV1.2

Trace organic compounds in an Antarctic ice core: a high-resolution analysis to reconstruct the anthropogenic fingerprint 

Giulia Genuzio, Marco Vecchiato, Elena Argiriadis, Andrea Spolaor, Massimo Frezzotti, Carlo Barbante, and Gabriele Capodaglio

This research work focuses on reconstructing the anthropogenic fingerprint of the past 150 years through the high-resolution analysis of trace organic compounds preserved in Antarctic ice.

Over the decades, numerous persistent and semi-volatile organic pollutants were largely used in several industrial activities. Some of them proved to be highly toxic, posing a serious threat to human health and natural ecosystems. Consequently, international bans and agreements were established to reduce their industrial production. As a result, restrictions on one compound have led to increased emissions of other chemical substitutes. A rise-and-fall trend in the concentrations between well-established and emerging pollutants is expected in response to international legislative measures. High resistance to biodegradation and semi-volatility promote the long-range atmospheric transport of these molecules, which reach remote areas such as polar regions, where they accumulate as a result of cold condensation processes.

The extraction site GV7 (70°41' S, 158°51' E, 1950 m a.s.l.) is highly significant since it presents a high snow accumulation rate (241 ± 13 mm we yr-1). This feature, rare in recent archives, enables the analysis of trace organic compounds that would otherwise require considerably high amounts of matrix. The ice core (length: 50 m; diameter: 100 mm) is an ideal archive to investigate the “Great Acceleration” since it spans the last 150 years.

The novel analytical method specific for snow and ice applied in this work allows to recognize the evolution of a single compound over time in response to international bans and social changes. The multi-proxy approach adopted allows to identify trends in well-established and new generation organic pollutants as well as personal care products. More specifically, fragrances are compounds of increasing interest since they provide information on use and consumption related to changes in household and social habits.

Solid-phase extraction (SPE) combined with gas chromatography coupled with triple quadrupole mass spectrometry (GC-MS/MS) enable to significantly increase the analytical signal. In addition, samples were entirely processed in a stainless-steel clean room to reduce contamination, achieve low detection limits, and obtain high-resolution data.

Results show a change in the concentration of each compound on a time frame of 150 years. Since this is a pilot study, the processes involved in the transport and deposition of the analytes in deep ice are not yet fully understood and need further investigation. It is necessary to take into consideration possible changes in the use and consumption of organic molecules and potential variations in atmospheric transport.

Previous studies provide data on personal care products on surface snow, which are essential for a broader interpretation of the processes involved.

How to cite: Genuzio, G., Vecchiato, M., Argiriadis, E., Spolaor, A., Frezzotti, M., Barbante, C., and Capodaglio, G.: Trace organic compounds in an Antarctic ice core: a high-resolution analysis to reconstruct the anthropogenic fingerprint, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15658, https://doi.org/10.5194/egusphere-egu24-15658, 2024.

EGU24-15864 | Posters on site | GMPV1.2

Mercury contamination in a former mining plant of NW Tuscany (central Italy)   

Nisi Barbara, Federica Meloni, Jacopo Cabassi, and Orlando Vaselli

Mine dumps are man-made geological formations characterized by unique chemical, particle-size, bacterial, and physical and mechanical features, representing deposits or cumuli of crushed, grounded and roasted material. Processing plants of metallic poli-sulfide ore deposits have contributed to pollute soils and surface and ground waters in many areas worldwide. The southern sector of the Apuan Alps (northern Tuscany, Italy) hosts a number of small pyrite ± barite ± iron-oxide orebodies that have been exploited since at least the Middle Age, whose activity ceased at the end of the 20th century. The most important mining areas were those distributed along a 10 km-long NE-SW strip in high Hg contents the southern portion of the Apuan Alps. In this framework, the Rezzaio treatment plant (Valdicastello Carducci, Pietrasanta), dismissed since 1991, was the site where ore bodies hosted within the metamorphic rocks of the Apuane Unit, mainly from Monte Arsiccio, Pollone and Buca della Vena mines were treated. The materials extracted from these mines were barite and iron oxides (both hematite and magnetite) used as weighting agents as drilling mud during petroleum drilling wells. Abandoned mining tunnels and dumps and plants for mineral treatment are still present in the area, posing a series of environmental threats. Our study focused on assessing the impact due to mercury contamination released by the treatment plant of Rezzaio by the past-mining activity. The aims of this study were to (1) determine the concentration of Gaseous Elemental Mercury (GEM or Hg0) in air and interstitial soil inside and outside the plant, including the working areas and the edifices where the workers were operating (e.g., offices, laboratory, rock storage); (2) assess the total amount of Hg in the top- and sub-soils, mostly developed on a small mining dump and (3) quantify the release of Hg by soil leaching tests by Milli-Q water. According to WHO and the Italian Legislative Decrees, the GEM values in air and outside the plant and in the plant edifices and mining structure are below the Recommended Exposure Limit. The spatial distribution of Hg indicates that up to 88 mg/kg were recorded in the top- and sub-soils, the highest contents being found on the small mining dump that is partly the bank of a creek. However, in most cases the concentration of Hg leachate were < 1µg/L, suggesting that mercury is likely trapped within crystalline silicate structures recalcitrant to chemical weathering. These results suggest that despite the high contents, mercury is not apparently playing a critical role as a contaminant in the Rezzaio area, being hosted in relatively insoluble minerals.

How to cite: Barbara, N., Meloni, F., Cabassi, J., and Vaselli, O.: Mercury contamination in a former mining plant of NW Tuscany (central Italy)  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15864, https://doi.org/10.5194/egusphere-egu24-15864, 2024.

EGU24-16063 | ECS | Orals | GMPV1.2

Particle-bound mercury transport across a mine-polluted fluvial system: towards a simple method to measure Hg flux from the Monte Amiata Mining District (Southern Tuscany, Italy) 

Alessia Nannoni, Vito Annese, Silvia Fornasaro, Guia Morelli, Francesco Ciani, Alessio Monnanni, Pierfranco Lattanzi, Valentina Rimondi, Pilar Costagliola, and Cesare Fagotti

Mining activities have a severe impact on fluvial systems. The dispersion of huge amounts of heavily polluted wastes contribute to mining-related river pollution due to runoff. Pollutants distribution in fluvial systems is controlled by the interplay between weather conditions (e.g., flooding events), geomorphic processes, and anthropic activities affecting sediments supply, erosion, transport, and (re-) deposition. Mercury (Hg) is listed as a critical contaminant due to its high toxicity, mobility, and persistence in the environment. Its use is progressively banned. As a result, Hg mining is now limited to a few countries. However, legacy mine wastes are still releasing Hg into the environment, particularly to fluvial systems. The Monte Amiata Mining District (MAMD, Southern Tuscany) was the 3rd largest Hg producer worldwide. Four river basins drain the MAMD. Among them, the Paglia River (PR) basin drains the SE sector of the MAMD, covering an area of 1320 km2. The widespread Hg pollution and the low resilience to contamination of this river basin was demonstrated in previous studies. Extreme flooding events redistributed huge amounts of polluted sediments across the catchment. The Hg flux discharged by PR to the Tiber River, and ultimately to the Mediterranean Sea, was estimated around 11kg/y. However, this estimate is based on spot samplings. In this study, the relationship between Hg transported by particulate (Hgp), total suspended solids (TSS) and water turbidity (Tbw) for PR was investigated to set up a method for the calculation of Hg fluxes from TSS and Tbw monitoring. Water samples were collected in different hydrological conditions between 2022 and 2023. Samples were taken along the PR, upstream and downstream of the Elvella creek confluence (ECC), a tributary that is not polluted by Hg, to evaluate its effects on the Hg budget. The samples were filtered and the TSS collected on the filters were analyzed for Hg. Part of the samples were analyzed also for Tbw to investigate the relationship between TSS and Tbw. TSS ranged between 1.3 and 621.4 mg/L, whereas Hg varied between 0.8 and 321.8 ng/L. Tbw varied between 12.2 and 358 NTU and a linear relationship was found between TSS and Tbw. The highest Hg and TSS values were measured during the recession phase of flooding events, whereas the lowest ones were found during low flow conditions. A linear relationship was also found between Hg and TSS. Hg was higher in the upstream samples than in those collected downstream the ECC, confirming that Hg source is the heavily polluted PR basin. The relationship between the two parameters could be applied to the indirect, continuous measurement of Hg fluxes discharged by PR with an automated TSS/Tbw sensor. Such monitoring would allow assessing the variability of Hg pollution and transport across the PR basin in real time especially in case of flooding, that are expected to become more frequent due to climate change, leading to an increase of Hg delivery to the Mediterranean Sea.

How to cite: Nannoni, A., Annese, V., Fornasaro, S., Morelli, G., Ciani, F., Monnanni, A., Lattanzi, P., Rimondi, V., Costagliola, P., and Fagotti, C.: Particle-bound mercury transport across a mine-polluted fluvial system: towards a simple method to measure Hg flux from the Monte Amiata Mining District (Southern Tuscany, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16063, https://doi.org/10.5194/egusphere-egu24-16063, 2024.

EGU24-16836 | ECS | Orals | GMPV1.2 | Highlight

Can contamination indices performance be improved by accounting for the dilution effect when dealing with stream sediments? A case study from southern Italy. 

Antonio Iannone, Annalise Guarino, Lucia Rita Pacifico, and Stefano Albanese

Geochemical prospecting is a valuable tool for investigating the influence of the geological context on the composition of stream sediment and determining the existence of any natural or anthropogenic geochemical anomaly within a river catchment basin. Several indices have been proposed in scientific literature to assess sediment's environmental quality and the ecological condition of catchment basins. In environmental studies, these indices are usually based on applying ratios among the raw geochemical composition of the sediment at the sampling location and a value assumed as a reference for the undisturbed conditions (Background/baseline). However, the reference values are often determined while overlooking the potential influence of river dynamics on the variability of sediment composition, and this can compromise the robustness of the contamination assessment.

As a matter of fact, the chemical composition of a stream sediment sample is representative of the relative upstream catchment basin. The Sample Catchment Basin (SCB) method, which accounts for the dynamic nature of rivers, has been largely used in literature to correct the dilution effect impacting the composition of stream sediment, aiming at determining reliable geochemical background values to be used for mineral prospecting.

The main purpose of the study was to check if the use of the correction of the dilution effect to determine background values could also improve the performance of some contamination indices, favouring a more effective and accurate assessment of the environmental degradation affecting a river basin.

The Sarno River, known for its susceptibility to contamination from urban and industrial sources, served as a pertinent case study. A total of 96 samples were used to define the zone of influence of each sample through the elaboration of geomorphological and hydrological features; then, the background concentrations of each element were estimated by calculating the weighted average element content based on the areal proportions of lithologic units in each sample catchment basin. The values deriving from this step were then used as a reference to calculate the degree of contamination for each SCB.

The contamination indices were calculated and mapped by using both non-diluted and dilution-corrected background data.

A comparative analysis was performed among the results obtained to assess if sensitive changes occurred to the spatial and statistical distribution of used indices and to determine if an improvement in performance could be obtained.

 This study represents a methodological benchmark for future research focusing on environmental risk assessment of stream sediment.

How to cite: Iannone, A., Guarino, A., Pacifico, L. R., and Albanese, S.: Can contamination indices performance be improved by accounting for the dilution effect when dealing with stream sediments? A case study from southern Italy., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16836, https://doi.org/10.5194/egusphere-egu24-16836, 2024.

EGU24-17147 | ECS | Orals | GMPV1.2

Comprehensive analysis and multivariate statistical approach of Transfer Factors soil-to-plant estimated from bioavailable concentrations in agricultural products: the case study of the Campania region (Southern Italy) 

Lucia Rita Pacifico, Annalise Guarino, Antonio Iannone, Antonio Pizzolante, Mauro Esposito, Gianfranco Brambilla, and Stefano Albanese

Understanding the transfer of contaminants from soil to plants, especially agricultural products, is essential in environmental science, particularly in the context of risk assessment and the development of sustainable agricultural practices. The estimation of transfer factors (TFs) (Singh et al., 2011), which quantify the uptake of elements or pollutants by plants from the surrounding soil, serves as a crucial parameter in evaluating potential ecological and human health risks, as these elements could enter the food chain (Ozhovan and Kremenetskiy, 2018).

For this study, the Transfer Factors soil-to-plant were estimated using the bioavailable concentrations (Guarino et al., 2022) of Potentially Toxic Elements (PTEs) identified by Italian law (D.lgs. 152/2006) in the agricultural soils and the elemental concentration in the primary agricultural products (PAP). These latter are freshly harvested fruits and vegetables, which retain their integrity and freshness as they have not undergone significant processing, collected across the entire region through the Campania Trasparente project (www.campaniatrasparente.it).

The aim of this study was to compare various Transfer Factors (TFs) among the most numerous vegetal species and potentially highlight different behaviours. A robust multivariate statistical approach, such as Robust Principal Component Analysis (RPCA) was applied to the TFs, and a multiple regression, using the stepwise method, was performed, with Principal Components as dependent variables and soil physical parameters (grain size, organic matter, pH, cation exchange capacity, salinity, electrical conductivity) as independent variables.

Our findings reveal distinct patterns in the soil-to-plant transfer factors for various elements, emphasizing the role of soil properties, plant species, and environmental conditions. Results reveal that, within the Campania region, the highest TFs for the most vegetal species are associated with Zn and Cu. Specifically, RPCA indicates a positive correlation between Zn and Co TFs. In the end, the multiple regression analysis highlights that clay presence and cation exchange capacity are the primary soil physical factors influencing TFs across different plant species.

This integrated approach could provide a comprehensive understanding of soil-plant transfer processes and the impact of soil physical parameters on TFs in regional cultivations. The study helps better understand the impact of soil physical parameters, such as cation exchange capacity (CEC), grain size, organic matter, etc., on vegetal species growth. It can lead to well-informed decisions regarding crop selection, fertilizer application, irrigation, and other factors.

References:

Guarino, A., Albanese, S., Cicchella, D., Ebrahimi, P., Dominech, S., Pacifico, L.R., Rofrano, G., Nicodemo, F., Pizzolante, A., Allocca, C., Romano, N., De Vivo, B., Lima, A., (2022). Factors influencing the bioavailability of some selected elements in the agricultural soil of a geologically varied territory: the Campania region (Italy) case study. Geoderma 428, 116207.

Jaswant Singh, Suraj K. Upadhyay, Rajaneesh K. Pathak & Vidhu Gupta (2011). Accumulation of heavy metals in soil and paddy crop (Oryza sativa), irrigated with water of Ramgarh Lake, Gorakhpur, UP, India, Toxicological & Environmental Chemistry, 93:3, 462-473.

Ozhovan M, Kremenetskiy A. (2018). Transfer Factors: Concepts and Applications in Soil-Plant Systems. Boca Raton, FL: CRC Press.

How to cite: Pacifico, L. R., Guarino, A., Iannone, A., Pizzolante, A., Esposito, M., Brambilla, G., and Albanese, S.: Comprehensive analysis and multivariate statistical approach of Transfer Factors soil-to-plant estimated from bioavailable concentrations in agricultural products: the case study of the Campania region (Southern Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17147, https://doi.org/10.5194/egusphere-egu24-17147, 2024.

In the past 20 years, the occurrence of tungsten-related health and safety incidents has drawn the close attention of scholars to the toxicity of tungsten and its health and environmental effects. The upper limit of tungsten concentration in water, its mobility and toxicity are all closely related to its speciation. Although polytungstates have been proven to be more toxic and migratory than monomeric tungstates, there is limited information about their abundance in natural environments due to the lack of a reliable analytical approach for determination. In this study, we conducted a simultaneous analysis of monomeric and polymeric tungsten species in natural water using reverse-phase ion pair chromatography coupled with inductively coupled plasma mass spectrometry. Polytungstates and five monotungstates, including tungstate as well as mono, di, tri, and tetrathiotungstate, were chromatographically separated within 35 min of using ethanol (12 - 48% gradient) as the mobile phase. The detection limit of polytungstates was 1.50 µg/L. Although common for the analysis of metals, experimental studies based on electrospray ionization - high resolution mass spectrometry (ESI-HRMS) have indicated that samples containing polytungstates should not be acidified, as it could result in the transformation of monotungstates to artifact polytungstates. Overall, our study offers an effective method for the analysis of various tungsten species, especially polytungstates, at environmentally relevant concentrations.

How to cite: Zhao, Q. and Hu, S.: Reverse phase ion pair chromatography coupled with inductively coupled plasma mass spectrometry as a method for tungsten speciation in natural waters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17460, https://doi.org/10.5194/egusphere-egu24-17460, 2024.

EGU24-18436 | ECS | Posters on site | GMPV1.2

An updated database of mercury emissions based on remote sensing, geochemical surveys and laboratory experiments 

Federica Benedetti, Giulia Marras, Marco Brandano, Sergio Calabrese, Vittorio Bosi, Antonio Ricciardi, and Vincenzo Stagno

Mercury (Hg) represents one of the top ten chemical elements of significant public concern according to the World Health Organization. In 2013, the Minamata Convention was established aiming to reduce, control and possibly eliminate the use and release of mercury in the environment. The Global Mercury Assessment 2018 estimated annual global mercury anthropogenic emissions at around 2200 tons, while the contributions of primary natural sources (e.g., volcanic activity) appear significantly uncertain.

The aim of this study is to better constrain the origin and quantity of mantle-derived Hg by integrating the current available data from experimental petrology, geochemical analyses of sedimentary rocks the Hg anomaly of which is linked to large-scale magmatic events, chemical data of igneous rocks and Hg measurements from volcanoes and minerals by in situ and in satellite remote sensing.

The volcanic Hg is known to be characterized by an atmospheric residence period of 0.5-2 years (Bagnato et al., 2007) that allows it to distribute over the globe in the form of Hg0 and Hg2+.Inizio modulo The oxidation of Hg0 to Hg2+ causes mercury to dissolve into aqueous fluids. Part of Hg directly migrates to the atmosphere, precipitate into sedimentary basins and eventually long-term sequestrate in marine sediments (Grasby et al., 2019).

Sharp Hg anomalies have been detected in several stratigraphic layers with concentrations varying from 20 ppb (La Bédoule, France) to 90 ppm (Grane field, southern Viking Graben, Norwegian North Sea) to be representative of mass extinction anoxic and Large Igneous Province events (i.e. Greater Ontong Java and North Atlantic Igneous Province) such as Selli oceanic anoxic event and Palaeocene-Eocene Thermal Maximum, respectively (Grasby et al., 2019 and reference therein). The analyses of current Hg volcanic emissions along with stratigraphic geochemical anomalies highlight transport processes of deeply seated Hg of mantle origin (Shen et al., 2023). The interior of Earth is proposed to store about 10 ppb of Hg (BSE model, McDonough and Sun 1995) within a variety of igneous rocks both intrusive (peridotites, pyroxenites and gabbros) and effusive (basalts), the majority of which (about 5 ppb) is hosted by ophiolites (Canil et al., 2015).

Further, the current global volcanic Hg flux ranges from 0.6 ton·yr-1 to over 1000 ton·yr-1 (Edwards et al., 2021) pointing out the high volatility of mantle-derived Hg that is confirmed by the established link between volatile-driven LIP events and Hg anomalies distributed worldwide. Additional sources of natural Hg emissions are represented by hydrothermal mineralization (e.g. cinnabar) that testify the dominant role of SO2 and H2S emissions in volcanic and hydrothermal systems, respectively.

We will present a preliminary database of global Hg concentration that allows to model the deep Hg cycle based on the effect of magma-mineral element distribution and the role of pressure-temperature-mantle redox state through space and time.

How to cite: Benedetti, F., Marras, G., Brandano, M., Calabrese, S., Bosi, V., Ricciardi, A., and Stagno, V.: An updated database of mercury emissions based on remote sensing, geochemical surveys and laboratory experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18436, https://doi.org/10.5194/egusphere-egu24-18436, 2024.

EGU24-18537 | ECS | Posters on site | GMPV1.2

Gravity-driven drainage of a thin film on a stalagmite  

Justine Parmentier, Vincent Terrapon, and Tristan Gilet

Stalagmites in karstic caves may serve as paleoclimate proxies, especially in regions missing glacial ice cores or other continental proxies. Specifically, the laminae revealed in a stalagmite cross-sectional cut can be related to the past upstream flows and soil coverage above the cave. The shape of these laminae, and therefore of the stalagmite top surface, thus change over time in response to variable environmental conditions. However, the effect of the past flows on such shape variability remains poorly understood. Previous models describing stalagmite growth thus involved strong simplifying assumptions regarding the aerodynamics and hydrodynamics of drops impacting stalagmites in caves. For instance, drops were assumed to always land at the apex of the stalagmite, thereby feeding the thin residual film covering it in one central point, while it was recently shown that the drop impacting position is sometimes scattered over several centimeters, which may have a non-negligible effect on stalagmite width [1]. The concave shape exhibited by some stalagmites was also associated with drops splashing at impact, while most drop impacts in caves lead to splashing and cannot, therefore, be related to a particular stalagmite shape [2]. Another assumption of previous stalagmite growth models is that the thin residual film lying on top of the stalagmite remains uniform in time and space, which may not always be accurate.

We thus propose to study the evolution of this residual film in time and space. Starting from an initially dry stalagmite, the film thickens because of the liquid brought by the successive drops, until it reaches a steady state. The thickness of the film at steady-state results from the balance between the incoming flow of drops falling on the stalagmite, and the film depletion through gravity-driven drainage. If this drop inflow is interrupted, only the drainage remains. We are interested in assessing the effect of the main factors influencing the film thickness evolution during these three phases, namely: (i) the underneath stalagmite shape, and (ii) the drop dripping frequency, i.e., the amount of liquid brought over a certain time. To achieve this, we record film thickness measurements during the filling, stationary and sole drainage phases on actual stalagmites, both in caves and in a lab setting. The caves provide a great diversity of shapes while the lab measurements allow to systematically vary the drop dripping frequency. We complete these measurements by a reduced-order modeling of the film thickness in time and space, using Reynolds lubrication equation expressed in curvilinear coordinates to account for the various existing stalagmite profiles. We obtain a good agreement between the experimental measurements and the results provided by the model with a set of parameters representing adequately the stalagmites of our dataset. We finally show that, depending on the stalagmite shape, considering the film as uniform in time and space may remain a valid assumption, but this is not always the case.

[1] Parmentier J. et al, P. R. Soc. A. (2019), https://doi.org/10.1098/rspa.2019.0556
[2] Parmentier J., Terrapon V. and Gilet T., Phys. Rev. Fluids (2023), https://doi.org/10.1103/PhysRevFluids.8.053603

How to cite: Parmentier, J., Terrapon, V., and Gilet, T.: Gravity-driven drainage of a thin film on a stalagmite , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18537, https://doi.org/10.5194/egusphere-egu24-18537, 2024.

EGU24-18550 | Posters on site | GMPV1.2

Experiences in a full-scale cyclone plant treatment of Hg-contaminated port sediments. 

Efren garcia-Ordiales, JoseIgnacio Barquero Peralbo, Enol Navarro Murillo, Pelayo Rico Fernandez, and Pablo Cienfuegos Suarez

The present work is based on a full-scale project for the treatment of port sediments with high Hg concentrations. The port area of this work is located in the Principality of Asturias (northern Spain). Preliminary studies for the implementation of a dredging activity on the sediments of the Llanes port showed Hg concentrations in the sediments ranging from 0.19 to 1.13 µg g-1, with an average of 0.81 µg g-1. This Hg average concentrations exceeds the legal threshold in Spanish territory for returning dredged sediment to the sea, so that according to current legislation it must be extracted from the coastal system and managed on land, generating a substantial loss of a significant volume of sediment in the system. In order to improve a circular economy and to be able to manage these Hg-contaminated materials to be dredged more efficiently, laboratory-scale tests verified that the Hg contamination was mostly found in the finets fraction <63µm. With these previous results and with regional governmental support, the company EXCADE S.L. in collaboration with the University of Oviedo designed and built a full-scale plant based on the treatment of contaminated sediments by cyclone for the efficient removal of the fine contaminated fraction.  Between June and August 2023, a total of 8,000 m3 of contaminated sediments from this port area were processed in a first phase through this treatment plant. The particle size and the Hg concentrations in the treated material were monitored every two working days, and after the treatment of all the material, four representative samples of the total volume treated were sent to an external laboratory to validate the results obtained during the procedure. The monitoring results showed that the treated material had fine material concentrations of less than 5%, and that the Hg concentration ranged from 0.05 to 0.13 µg g-1, which resulted in a 7-fold reduction of the initial average Hg concentration in the sediments. The same occurred with the results from the external laboratory that showed that the treated material had fine material concentrations of less than 5%, and that the Hg concentration ranged from 0.13 to 0.17 µg g-1. These Hg concentrations in the treated material were within the legal range in Spanish territory, which is why the treated material was authorized for deposit at sea. Throughout 2024, the same procedure will be carried out on 12,000 m3 of new contaminated by Hg material to be dredged to validate the results of this first real-scale experience for the treatment of sediments contaminated by high Hg concentrations.

How to cite: garcia-Ordiales, E., Barquero Peralbo, J., Navarro Murillo, E., Rico Fernandez, P., and Cienfuegos Suarez, P.: Experiences in a full-scale cyclone plant treatment of Hg-contaminated port sediments., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18550, https://doi.org/10.5194/egusphere-egu24-18550, 2024.

Materials research applied to archaeological ceramic artefacts has garnered widespread interest among scientists, architects, engineers, and archaeologists focused on safeguarding architectural heritage. These ancient structures within historic city centers encapsulate the distinctive history and visual essence of each city across different eras. Assessing both old and new materials following damage to these historical edifices becomes crucial for predicting their behaviour during restoration. This endeavour not only aims to analyze and preserve these artifacts but also aims to explore the knowledge and craftsmanship involved in their creation and use. Characterizing building materials primarily targets preservation and restoration goals, encompassing the origins of historical raw materials, understanding archaeological artifact changes, determining original firing methods, and reconstructing manufacturing technologies. Bricks and ceramics, resembling fired artificial rocks, retain geological imprints from their claystone origins, impacted by local geological settings influencing material availability and building techniques. Take, for instance, Ferrara, a Medieval city in Northeast Italy, strategically positioned between the Adriatic Sea and the Po alluvial plain. Its prosperity during the Renaissance under the Estense family was bolstered by extensive modifications to the city, predominantly utilizing locally abundant silico-clastic sediments for construction.

The focus of this research on historical bricks and terracotta decorations from prominent Medieval and Renaissance buildings in Ferrara is to understand the composition of these ancient materials to aid in planning effective restoration treatments, identifying causes of decay, selecting suitable replacement materials, and avoiding incorrect restoration choices. Analyzing the chemical and geological attributes of these materials provides valuable insights into their manufacturing techniques and origins. Moreover, by comparing obtained data with regional sediment records, it has been possible to ascertain the nature and sources of the original raw materials.

How to cite: Marrocchino, E. and Vaccaro, C.: Geochemical characterization of bricks and terracottas used in historical monuments in Ferrara (Italy): Reference to raw materials and production technique, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19518, https://doi.org/10.5194/egusphere-egu24-19518, 2024.

EGU24-19595 | Posters on site | GMPV1.2 | Highlight

Quantification Of Mercury (Hg) In Riparian Trees Along The Paglia River, Monte Amiata Hg Mining District (Italy): Implications For A Sustainable Environmental Management And Risks 

Guia Morelli, Francesco Ciani, Pilar Costagliola, Cesare Fagotti, Pierfranco Lattanzi, Alessio Monnanni, Alessia Nannoni, and Valentina Rimondi

Riparian vegetation plays an important role in fluvial ecosystems. River drainage in abandoned mine sites is often source of heavy metals through transport of contaminated sediments. In those areas riparian vegetation may take up contaminants from riverbanks soil, acting as a temporary storage of metals. In this study, the potential mercury (Hg) in plants growing on soil anomalous in Hg was quantified to evaluate its storage effectiveness, and the potential as a secondary Hg source to the atmosphere in case of fire, or upon anthropic utilization as biomass.
Riparian trees along a section of the Paglia River (Tuscany, Italy), draining the abandoned Monte Amiata Hg mining district, the 3rd Hg producer worldwide in the past, were sampled from the riverbanks. The riparian vegetation is occasionally cut during bank maintenance, and the resulting wood may end up into wood chips for solid biofuel. Poplars (Populus spp.) are the most abundant species naturally widespread along the Paglia riverbanks, together with Robinia spp. and Quercus spp.. 
Cores of trunks (8/10 cm long, 0.5 cm diameter) from 50 trees were sampled from fives sites using a drill corer. At each site, a soil sample was collected. 
In soils, Hg ranged from 3.5 to 52.8 mg/kg, above the Italian limit for soil (1 mg/kg; D.Lgs.152/2006). Preliminary data in trees, show Hg ranges between 0.5 and 93 ug/kg. Anomalous Hg concentrations (195-353 ug/kg) in few samples are probably associated to soil particles trapped in the tree barks. Except for these values, Hg concentrations in trees are below the recommended Hg limit (100 ug/kg) for high quality solid biofuels (European EN ISO 17225, 2021), thus posing little to moderate impact on the value of the locally harvested wood chips and the potential health risk for Hg0 emissions. On the other hand, in case of wildfires, Hg stored in trees bole wood (about 0.6 kg estimated in the studied area) can be released from the burning trees and from the subjacent soil. Thus, vegetation represents a potential secondary source of Hg0 to the atmosphere. Results highlight the importance in similar contaminated areas of metals fate investigation in soil and plants to assess the actual risks to the surrounding environment (biota, human health, and animals) posed by Hg emissions in case of fire, or for example by biomass used for energy production. Remediation strategies in these areas should include a wise management of riparian vegetation as a tool for mitigation of Hg release in the environment.

How to cite: Morelli, G., Ciani, F., Costagliola, P., Fagotti, C., Lattanzi, P., Monnanni, A., Nannoni, A., and Rimondi, V.: Quantification Of Mercury (Hg) In Riparian Trees Along The Paglia River, Monte Amiata Hg Mining District (Italy): Implications For A Sustainable Environmental Management And Risks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19595, https://doi.org/10.5194/egusphere-egu24-19595, 2024.

EGU24-19791 | Orals | GMPV1.2 | Highlight

Critical raw materials from geothermal fluids: Potential in the North German Basin 

Simona Regenspurg, Anika Thomas, Jessica A. Stammeier, Ferry Schiepersky, Magdalena Scheck-Wenderoth, and Katrin Kieling

The EU-funded CRM-geothermal project aims to integrate the extraction of critical raw materials and geothermal heat from deep geothermal reservoirs. Within the project, extraction technologies and their economic and environmental feasibility are tested and evaluated across several geological regions in Europe and East Africa.

  The focus of this study is the North German Basin, a typical sedimentary basin that initiated rifting in the late Carboniferous period, accumulating various sediments to a thickness of up to 10–12 km. Located in central Europe it stretches over an area from Poland to the Netherlands, traversing across North Germany.

The succession is beginning with Permian volcanic rocks at the base, and overlain by alternating layers of mud-, silt- sandstones and evaporates; some of which have already been identified for geothermal energy extraction (e.g. Neustadt-Glewe, Schwerin, and Potsdam). Up to now, the extraction of lithium (Li) has not been explored, despite the existence of elevated Li concentrations occurring in formation fluids of the Rotliegend and Bunter sandstone.

In this study the potential content of selected critical and valuable elements (Li, Sr, Cu) and their availability in various formations of the North German Basin was assessed. For this purpose, cuttings from different formation rocks from one deep well (GrSk04/05; 4000 m depth) were first analyzed for bulk concentrations of these elements. Most promising samples (with Li up to 74 ppm, Cu up to 214 ppm, and Sr with up to 2334 ppm) were selected from Muschelkalk, Bunter sandstone (Dethfurt), Zechstein (Ohre), Permian Rotliegend sandstone (Hannover), and volcanic rocks)  for a sequential extraction. This method provides indication on the type of elemental bonding within minerals, allowing to estimate the availability and sustainability of the CRM in the respective formation fluids.

How to cite: Regenspurg, S., Thomas, A., Stammeier, J. A., Schiepersky, F., Scheck-Wenderoth, M., and Kieling, K.: Critical raw materials from geothermal fluids: Potential in the North German Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19791, https://doi.org/10.5194/egusphere-egu24-19791, 2024.

EGU24-20063 | Posters on site | GMPV1.2

Vertical concentration profile of mercury in a 476-cm sediment core from the Bohai Sea: Inferring anthropogenic influence 

Chunye Lin, Wei Ouyang, Mengchang He, Xitao Liu, and Jing Wang

Mercury is a worldwide contaminant, with a usual concentration range of 10 to 100 μg kg-1 in the marine/oceanic sediments. The Bohai Sea, the largest gulf in China, is nearly enclosed by densely populated and industrialized land and connects to the northwestern Pacific Ocean via the Bohai Strait. The sediment core (profile) may record anthropogenic mercury history. A 476-cm sediment core was collected and sectioned into 1-cm slices, which were analyzed for mercury and conservative tracer scandium. Mercury content ranged from 14.4 to 35.5 μg kg-1 while scandium content ranged from 9.57 to 13.1 μg kg-1. Overall, mercury content increased from the sediment profile base up to top while scandium content decreased, showing that anthropogenic activities around the bay led to mercury enrichment and accumulation in the sediment. In details, mercury content in the sediment ranged from 14.4 to 17.4 μg kg-1 and averaged 16.3 μg kg-1 from 476-cm depth up to 351-cm depth. This average mercury content is considered as its geochemical base level in the bay. From 351-cm depth up to 181-cm depth, mercury content in the sediment ranged from 16.6 to 20.1 μg kg-1 and averaged 18.4 μg kg-1. The fluctuations in mercury content in this period might be related to climate change. Mercury content in the sediment slowly increased from 16.9 μg kg-1 at 181-cm depth to 22.8 μg kg-1 at 38-cm depth, which is supposed to be related to anthropogenic activities. Afterwards, mercury content in the sediment rapidly increased from 22.8 μg kg-1 at 38-cm depth to 35.1 μg kg-1 at 21-cm depth and fluctuated between 33.4 and 35.5 μg kg-1 from 21-cm depth up to 9-cm depth. This rapid and high mercury enrichment and accumulation in the sediment is connected to the intensive anthropogenic activities around the bay. Subsequently, mercury content in the sediment decreased to 26.3 μg kg-1 at 5-cm depth and then increased to 29.0 μg kg-1 at the depth of 0-1 cm. Therefore, the mercury concentration profile in the 476-cm sediment core records the anthropogenic mercury pollution history in the Bohai Sea and can be used to estimate anthropogenic mercury mass and accumulation flux in the sediment.

This study was funded by the National Natural Science Foundation of China (42277366).  

How to cite: Lin, C., Ouyang, W., He, M., Liu, X., and Wang, J.: Vertical concentration profile of mercury in a 476-cm sediment core from the Bohai Sea: Inferring anthropogenic influence, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20063, https://doi.org/10.5194/egusphere-egu24-20063, 2024.

EGU24-20228 | ECS | Orals | GMPV1.2 | Highlight

Reactive transport model of an extreme acidic perched aquifer within roasted pyrite waste in a fully urbanized area (Zaragoza, Spain)  

Jon Jiménez, Miguel Ángel Marazuela, Carlos Baquedano, Jorge Martínez-León, Jose Ángel Sanchez Navarro, Noelia Cruz-Pérez, Juan C. Santamarta, and Alejandro García-Gil

The abandonment of industrial waste frequently leads to acid drainage affecting groundwater and severely impacting the environment or urban infrastructure. The severe impacts of the acid drainage are related, besides the extremely low pH reached in the affected waters, to the subsequent mobilization and spread of toxic heavy metals such as As, Fe, Cu, Cd, Ni, Pb, and Zn in highly oxidizing environments. The hydrogeology and hydrochemistry of an urban area in Al-Mozara (Zaragoza, Spain), built over an old industrial zone with pyrite roasting waste deposits that experienced acid drainage problems, has been investigated and modelled. Drilling and piezometer construction, and groundwater samples taken during the activities of the SAGE4CAN project, revealed the existence of a perched aquifer within old sulfide mill tailings, where the building basements interrupted the groundwater flow leading to a water stagnation zone that reached extreme acidity values (pH < 2), by drastically increasing the reaction times. A groundwater flow reactive transport model was developed with the software PHAST to reproduce flow and groundwater chemistry, to be used as a predictive tool for guiding and selecting the optimal remediation actions. The model reproduced the measured groundwater chemistry by simulating the kinetically controlled pyrite and portlandite dissolution. Further, the model predicts that an extreme acidity front (pH < 2), coincident with the Fe (III) pyrite oxidation mechanism taking dominance, is propagating by 30 m/year. The incomplete dissolution of residual pyrite (up to 18 % dissolved by the end of the simulations) predicted by the model indicates that the acid drainage in this aquifer is limited by the flow regime rather than by sulfide availability. The construction of additional water collectors between the recharge source and the stagnation zone has been proposed, together with periodical pumping out of acid water from the stagnation zone. The study findings are expected to serve as a useful background for the assessment of acid drainage and remediation techniques in urban areas by numerical modelling, since urbanization of old industrial land is rapidly increasing worldwide. 

How to cite: Jiménez, J., Marazuela, M. Á., Baquedano, C., Martínez-León, J., Sanchez Navarro, J. Á., Cruz-Pérez, N., Santamarta, J. C., and García-Gil, A.: Reactive transport model of an extreme acidic perched aquifer within roasted pyrite waste in a fully urbanized area (Zaragoza, Spain) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20228, https://doi.org/10.5194/egusphere-egu24-20228, 2024.

EGU24-20759 | ECS | Posters on site | GMPV1.2

Regional distribution of mercury in the leaves of Quercus ilex in the Almadén area (Spain) 

José Ignacio Barquero Peralbo, José María Esbrí Víctor, Domingo M. Ntutumu, Carmelo M. Minang, Saturnino Lorenzo Álvarez, Ana C. González Valoys, and Pablo Higueras

Quercus ilex is a vascular plant, a tree of large size, which is one of the most common species present in central Spain. Almadén (Ciudad Real province, South-central Spain) is the centre of a mining area active since prehistoric times, particularly for mercury, but also for others potentially toxic elements (PTEs: Pb, Zn, Ag, Cu), and in this area the Q. ilex constitutes woods, as well as the so called ‘dehesas’, a characteristic landscape with these trees scattered with variable density in pasture areas.

In this work we have sampled and analysed Hg and other PTEs (data not shown here) in the leaves from a wide area, of some 2,300 Km2, located around the Almadén mine and site. A total of 88 samples were taken, prepared, and analysed, using the Atomic Absorption Spectrometry with Zeeman effect combined with a process pyrolisation, with a LUMEX RA-915 series equipment.

The area corresponds to the southernmost Central Iberian Zone of the Iberian Hesperian Massif, characterized by Palaeozoic and Pre-Palaeozoic substrates. In particular, the samples are distributed in three geological subdomains: the Almadén syncline in the north, the Alcudia anticline in the centre and the Guadalmez syncline in the south. Siliciclastic Paleozoic detrital rocks are in the majority in both synclines, while the pre-Paleozoic rocks of the Alcudia anticline are mainly dominated by schists and greywackes. 

Mercury uptake by plants occur through their leaves, and it accumulates in these, as proven empirically and experimentally. Besides, the presence of Hg in the atmosphere depends on the eventual presence of discrete sources, such as mines or dumps, or on the Hg emissions from contaminated soils.

Our results show that Hg concentrations in Q. ilex leaves are conditioned by the presence of discrete sources in the Almadén syncline (the Hg mines present in this region), with a mean value of 197 ng/g ± 169, reaching even 1,000 ng/g in areas close to the main sources of atmospheric Hg. On the other hand, in the Alcudia Valley (99 ng/g ± 170) and the Guadalmez syncline (64 ng/g ± 192) the concentrations are lower and show a certain variability that may be related to the possible presence of the element in the soil in the form of anthropogenic contamination, as this research team has demonstrated in recent scientific publications.

How to cite: Barquero Peralbo, J. I., Esbrí Víctor, J. M., Ntutumu, D. M., Minang, C. M., Lorenzo Álvarez, S., González Valoys, A. C., and Higueras, P.: Regional distribution of mercury in the leaves of Quercus ilex in the Almadén area (Spain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20759, https://doi.org/10.5194/egusphere-egu24-20759, 2024.

EGU24-22463 | Orals | GMPV1.2

Mercury in the coastal pelagic food web: phytoplankton, zooplankton and jellyfish 

Jadran Faganeli, Kogovsek Tjasa, Mazej Darja, Malej Alenka, and Falnoga Ingrid

Four jellyfish species, ctenophoran Mnemiopsis leidyi and scyphozoan Cotylorhiza tuberculata, Chrysoara hysoscella and Rhizostoma pulmo were collected in summer of 2017 in the Gulf of Trieste (northern Adriatic Sea) and analysed for Hg and other metal(loid)s to assess their bioaccumulation and biomonitoring potential. No significant differences in Hg levels (0.06-0.22 µg/g dry mass) were observed between the studied species but all significantly concentrated Hg well above the dissolved Hg seawater levels (5 ng/L) of the gulf. The studied species have diverse diets consisting primarily of various plankton groups. C. hysoscella feeds mainly on mesozooplankton (>200 µm) R. pulmo and C. tuberculata mostly consume microzooplankton (50-200 µm) while M. leidyi preys on various organism (and particles) in the water column. In addition, C. tuberculata harbours autotrophic endosymbionts (microalgae). Considering their feeding behaviour, it appears that studied jellyfish species do not bioaccumulate Hg, nor other metal(loid)s, along the pelagic food web. Hence, the Hg levels in jellyfish are probably the consequence of the dissolved metal (passive and active) uptake. Moreover, the methodological approach analysing the jellyfish freeze-dried samples containing salt can distort the real picture and the Hg/Corg. ratio could better describe the metal level in the gelatinous organism. However, considering the high Hg bioconcentration factor (log BCF >5), jellyfish can be used aa a useful bioindicator for Hg, and other metal(loid)s, dissolved in seawater.     

Keywords: Jellyfish, coastal waters, mercury, bioconcentration, contamination, bioindicator

How to cite: Faganeli, J., Tjasa, K., Darja, M., Alenka, M., and Ingrid, F.: Mercury in the coastal pelagic food web: phytoplankton, zooplankton and jellyfish, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22463, https://doi.org/10.5194/egusphere-egu24-22463, 2024.

GMPV2 – Experimental and analytical advances in mineralogy and rock-forming processes

EGU24-176 | ECS | Posters on site | GMPV2.1

New insights on gypsum twinned crystals: mineralogical implications for natural gypsum deposits 

Andrea Cotellucci, Fermín Otálora, Àngels Canals, Joaquín Criado-Reyes, Luca Pellegrino, Marco Bruno, Dino Aquilano, Juan Manuel Garcia-Ruiz, Francesco Dela Pierre, and Linda Pastero

Identifying the impurities that promote the selection of specific twin laws of gypsum has relevant implications for the geological studies aimed at interpreting the gypsum depositional environments both in ancient and modern deposits, and overall, on Mars surface, where “swallowtail” gypsum twin habit has been recently observed. However, because of the limited knowledge of morphological, crystallographic, and optical characteristics of the five twin laws of gypsum, relatively little has been done to understand which impurities exert a critical role in the selection of different twin laws and how this may impact our awareness about their occurrence in nature. Typically, the 100-contact twin law has been the only twin law of gypsum known so far in nature. However, some sedimentological-stratigraphic studies suggested this might not be the only widespread one. In this work, we firstly provide a geometric-crystallographic background of the five twin laws of gypsum, allowing researchers to recognize the twin laws only by the measurement of i) their re-entrant angle value and ii) the extinction angle formed between the two individuals using crossed polarizers in optical microscopy. Moreover, we show specific crystal growth laboratory experiments designed to improve our understanding of different habits and twin laws of gypsum occurring with and without the addition of carbonate ions in solution. The main results suggest that the different orientation of primary fluid inclusions with respect to the twin plane, and the main elongation of the sub-crystals making the twin, are a useful tool to distinguish between 100 and -101 twin laws, whose geometry is otherwise very hard to distinguish, especially in rock samples. Moreover, gypsum twins obtained by crystal growth laboratory experiments are compared with those detected in natural environments and the occurrence of the -101 twin law is suggested occurring in evaporitic-sedimentary environments. These results provide new insights into the mineralogical implications of twinned gypsum crystals and their potential use as a tool for a deeper comprehension of the natural gypsum deposits.

How to cite: Cotellucci, A., Otálora, F., Canals, À., Criado-Reyes, J., Pellegrino, L., Bruno, M., Aquilano, D., Garcia-Ruiz, J. M., Dela Pierre, F., and Pastero, L.: New insights on gypsum twinned crystals: mineralogical implications for natural gypsum deposits, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-176, https://doi.org/10.5194/egusphere-egu24-176, 2024.

EGU24-565 | ECS | Orals | GMPV2.1

Decomposed zircons: A reliable geothermometer to identify impact and airburst glasses? 

Anna Musolino, Bertrand Devouard, Pierre Rochette, Pierrick Roperch, Pierre-Marie Zanetta, Anne-Magali Seydoux-Guillaume, Daniel Ferry, and Andrea Campos

When exposed to high-temperature conditions (~1670°C), zircon crystals (ZrSiO4) decompose according to the reaction: ZrSiO4→ZrO2+SiO2 [2,8]. Under optical and electron microscopes, decomposed zircons are easily identified by the presence of bright rims of baddeleyite (ZrO2) surrounding the unaltered primary crystal core (ZrSiO4). Due to the high temperatures needed for this reaction to occur (i.e., exceeding the highest temperatures normally reached by magmatic processes or wildfires on the Earth’s surface), finding decomposed zircons in natural glass has become a handy unequivocal way to relate natural glass to extreme processes like meteoritical impacts [1], airbursts [6], or lightning [3]. If recognizing fulgurites (i.e., products of lightning) is more easily done because of their morphology, the identification of impact glasses can be problematic, especially when they are not associated with a known impact crater. This work aims to demonstrate the reliability of zircon decomposition as a geothermometer, used to identify impact (or airbursts) glasses.

Through high-temperature experiments, we show that the decomposition of zircons can occur in natural systems at lower temperatures than the ones predicted by models. At T=900-1000°C (P=1 bar, exposed to air), in the presence of Ca-sulfates and NaCl-rich soil called ‘caliche’ (from the Atacama Desert, chosen for its relation with one of the most recent debated case, that of Pica glass – [4,5,6,7]), zircons decomposed forming the typical bright rims. Using FEG-SEM-EDS, Raman spectroscopy, and TEM (on thin foils prepared using FIB), however, we show that the Zr-rich rim mineralogy in our experiments differs from previous petrographic descriptions, with assemblages of baddeleyite, baddeleyite + Ca-Zr-oxide, or only Ca-Zr-oxide.

In conclusion, we demonstrate that decomposed zircons could also result from lower temperature processes than impacts or airbursts and should be used more carefully in assessing the origin of glasses. Also, we suggest that a more detailed mineralogical characterization of decomposed zircons (rarely done after their detection) is needed to correctly assess the formation conditions of samples containing such rims.  

References

[1] El Goresy A., 1965. Baddeleyite and its significance in impact glasses. Journal of Geophysical Research, 70:3453-3456.

[2] Kaiser A., et al., 2008. Thermal stability of zircon (ZrSiO4). Journal of the European Ceramic Society, 28:2199-2211.

[3] Kenny G.G. and Pasek M.A., 2021. The response of zircon to the extreme pressures and temperatures of a lightning strike. Scientific Reports, 11:1560.

[4] Roperch P., et al., 2017. Surface vitrification caused by natural fires in Late Pleistocene wetlands of the Atacama Desert. Earth and Planetary Science Letters, 469:15-26.

[5] Roperch P., et al., 2022. Widespread glasses generated by cometary fireballs during the late Pleistocene in the Atacama Desert, Chile: COMMENT. Geology, 50.5:e550.

[6] Schultz P.H., et al., 2022. Widespread glasses generated by cometary fireballs during the late Pleistocene in the Atacama Desert, Chile. Geology, 50.2:205-209.

[7] Schultz P.H., et al., 2022. Widespread glasses generated by cometary fireballs during the late Pleistocene in the Atacama Desert, Chile: REPLY. Geology, 50:e551.

[8] Timms N.E., et al., 2017. A pressure-temperature phase diagram for zircon at extreme conditions. Earth-Science Reviews, 165:185-202.

How to cite: Musolino, A., Devouard, B., Rochette, P., Roperch, P., Zanetta, P.-M., Seydoux-Guillaume, A.-M., Ferry, D., and Campos, A.: Decomposed zircons: A reliable geothermometer to identify impact and airburst glasses?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-565, https://doi.org/10.5194/egusphere-egu24-565, 2024.

EGU24-764 | ECS | Posters on site | GMPV2.1

Tin mineralization in post-magmatic processes: a case of post-magmatic activity in the Szklarska Poręba Huta quarry, Lower Silesia, SW Poland  

Karolina Mil, Bożena Gołębiowska, Adam Włodek, and Adam Pieczka

The Karkonosze granite (~320–312 Ma) is interpreted as a syn-collisional to magmatic arc intrusion. It is known for distinct symptoms of post-magmatic activity, including formation of intragranitic pegmatites observed in Szklarska Poręba quarry with overprinted W–Sn–Mo–Bi hydrothermal mineralization (e.g., Kozłowski et al., 1978; Pieczka & Gołębiowska, 2012).

Tin mineralization in the granite quarry at Szklarska Poreba is represented by cassiterite (Karwowski et al., 1972), Sn-rich titanite, malayaite, stokesite, and rare tin sorosilicates – kristiansenite, kozłowskiite and silesiaite (Evans et al., 2008;  Pieczka et al., 2022, 2023) The presence of all the above-mentioned mineral phases was confirmed by chemical microanalysis using the electron probe microanalyzer JEOL SuperProbe JXA-8230 and structure refinement. Cassiterite was recognized in an association mainly with scheelite, molybdenite, wolframite, chalcopyrite, and pyrite. These minerals crystallized from high-temperature aqueous fluids, subsequently followed by sulphide-rich stage (Karwowski et al., 1973). Sn-rich titanite, forming an isomorphic series with malayaite, CaTi[SiO4]O–CaSn[SiO4]O, shows chemical heterogeneity, with a maximum SnO2 content up to 15.88 wt% (32 mol% Sn end-member), and elevated Nb2O5 (up to 9.85 wt%), Ta2O5 (up to 7.88 wt%), and Sc2O3 (up to 1.90 wt%). Malayaite is close to the pure Sn end-member, it contains up to 97 mol% Sn end-member with minor Fe, Nb, Ta contents. Stokesite, CaSnSi3O9·2H2O, occurs as a rim grown around the outermost parts of Sn-rich titanite crystals, veinlets cutting cassiterite, and in direct contact with fluorite. Its crystals were also observed on surfaces or within fractures in bismuthinite.

The initial source of Sn was related to the final stage of pneumatolytic processes, in the granitic complex with successive development during hydrothermal activity. Fluid inclusion studies indicate that cassiterite crystalized at temperatures of 515–470ºC (Kozłowski et al., 2002).

The precipitation of Sn-rich titanite was likely initiated under elevated metal activities at slightly lower temperatures and high oxygen fugacity.

Stokesite, representing the final stage of the Sn assemblage, slowly crystallized in free spaces, was found in a direct contact with fluorite, which homogenization temperature in the Szklarska Poręba assemblage was estimated at 159-172 oC (Kozłowski & Matyszczak, 2022). Therefore, stokesite and fluorite may have formed during the same stage of hydrothermal processes. Since no alterations had been observed on the cassiterite grains, a secondary source of tin for later Sn-rich minerals was excluded.

 

How to cite: Mil, K., Gołębiowska, B., Włodek, A., and Pieczka, A.: Tin mineralization in post-magmatic processes: a case of post-magmatic activity in the Szklarska Poręba Huta quarry, Lower Silesia, SW Poland , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-764, https://doi.org/10.5194/egusphere-egu24-764, 2024.

EGU24-1209 | ECS | Posters on site | GMPV2.1

Understanding the flow dynamics of a Plagioclase Ultraphyric Basalt- a case study from the Westfjords, Iceland 

Patrícia Jones, Alberto Caracciolo, Edward W Marshall, and Elisa Johanna Piispa

The volcanic landscapes of Iceland's Westfjords are marked by the intriguing presence of Plagioclase Ultraphyric Basalts (PUBs), distinctive lava formations that are a focal point of this research. Characterized by plagioclase contents so high (up to 50-60%) that they approach the crystallinity of a crystal mush, these formations offer a unique opportunity to explore the extreme end of lava crystallinity and the influence of abundant large plagioclase crystals on lava viscosity and flow. The main aim of this research is to understand how the abundance of large plagioclase crystals influences the viscosity and flow of lavas at the extreme end of lava crystallinity, as well as better understand the origin of the crystal cargo. The interplay between the crystals and the magma is crucial for better understanding the origins and flow characteristics of these volcanic formations. This is achieved through an interdisciplinary approach, combining petrographical and geochemical analyses, including Inductively Coupled Plasma (ICP) for major element trace element analysis, with Anisotropy of Magnetic Susceptibility (AMS) to determine the flow direction within the lava. This comprehensive method provides insights into the crystallization conditions of magmas and minerals, as well as the textural and compositional characteristics of the plagioclase crystals. The outcomes of this research are not only crucial for understanding the unique aspects of the Westfjords’ volcanic regions but also have significant implications for predicting volcanic hazards and refining magma dynamics models, thereby enhancing our ability to mitigate the impacts of volcanic activity.

 

How to cite: Jones, P., Caracciolo, A., Marshall, E. W., and Piispa, E. J.: Understanding the flow dynamics of a Plagioclase Ultraphyric Basalt- a case study from the Westfjords, Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1209, https://doi.org/10.5194/egusphere-egu24-1209, 2024.

The study of iron-magnesium silicates within rocky planetary interiors has been a cornerstone of mineralogy, petrology and planetary science, offering insights into the composition and evolution of celestial bodies. The talk will present an exploration of the current understanding of these silicates and critically examines the question: Have we truly discovered them all?

Recent advancements in analytical techniques, including high-pressure experiments and computations, have challenged conventional assumptions about the ubiquity and diversity of iron-magnesium silicates. During the talk, key discoveries on Earth, Mars, and other celestial bodies will be reviewed revealing unexpected mineralogical variations and prompting a reevaluation of existing models.

How to cite: Bindi, L.: Iron-magnesium silicates in rocky planetary interiors: Have we really discovered them all?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1725, https://doi.org/10.5194/egusphere-egu24-1725, 2024.

EGU24-2001 | ECS | Posters on site | GMPV2.1

Complex Multi-Stage Replacement Reactions in the REE-CaCO3 System 

Melanie Maddin, Remi Rateau, Adrienn Marie Szucs, Luca Terribli, and Juan Diego Rodriguez-Blanco

Rare earth elements (REE) are essential in many green, modern technologies and play a critical role in a more sustainable future [1]. However, there is a substantial risk to their supply as the availability of REE deposits with minable concentrations are limited [2]. A better understanding of the mechanisms controlling REE concentration in minerals would have applications in more efficient practices as well as REE separation techniques and recycling.

Our study investigated the reaction of multi-component REE (La, Ce, Pr, Nd, and Dy) aqueous solutions with carbonate grains of dolomite, aragonite and calcite at hydrothermal conditions (21-210 °C). Two different solutions were prepared (i) a solution with equal concentrations of each of the five REE: (ii) a solution with the concentrations of the five REEs normalized to a Post Archean Shale standard (PAAS), to mimic the rare earth element concentrations in continental crust and natural fluids.

The interaction between the REE bearing fluids with each of the carbonate grains resulted in the replacement of the host carbonate grain with a series of REE minerals following a complex crystallization sequence (lanthanite → kozoite → bastnasite → cerianite). We have found that for most of the experiments at 165 °C, when using the equal concentration solutions, the crystallization of kozoite was promoted and the REE ratio in the newly formed solids was similar to the REE ratio in solution. In contrast, when PAAS solutions were used, REE-bearing crystals were zoned or had a heterogenous distribution of REEs, often coupled with the formation of discreet REE phases (e.g., cerianite). In addition, chemical signatures indicating the presence of metastable REE-bearing phases that transformed to more thermodynamically stable polymorphs were found in multiple samples as well as symplectite textures formed by the reaction of adjacent phases. Overall, our experiments demonstrate that the polymorph selection, crystallization pathway, the kinetics of mineral formation and the chemical texture of the newly formed rock during the mineral-fluid interaction process are dependent on the REE concentrations in solution, their ionic radii, temperature, time, and solubility of the host grains.

 

References

[1] Sinding-Larsen, R., Wellmer, F.W.,. Non-renewable resource issues: Geoscientific and societal challenges, Non-Renewable Resource Issues: Geoscientific and Societal Challenges 2012.

[2] Jordens, A., Cheng, Y.P., Waters, K.E.,. A review of the beneficiation of rare earth element bearing minerals. Miner. 2013 Eng. 41, 97-114.

How to cite: Maddin, M., Rateau, R., Szucs, A. M., Terribli, L., and Rodriguez-Blanco, J. D.: Complex Multi-Stage Replacement Reactions in the REE-CaCO3 System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2001, https://doi.org/10.5194/egusphere-egu24-2001, 2024.

Charnockite is an orthopyroxene-bearing felsic rock and an important constituent of the deep crust, thus, it holds significant importance in uncovering crustal growth and differentiation mechanisms. However, its generation and preservation remain debated. By focusing on mineral records, we here aim to provide a more detailed understanding of these issues. The Gaozhou charnockite in the Yunkai terrane of South China was chosen for extensive mineralogical studies and thermodynamic modeling. The Gaozhou charnockite contains granulitic enclaves, and mineral assemblages within charnockite can be divided into three phases, with the peak phase mainly composed of orthopyroxene, and minor biotite. Meanwhile, the charnockite and enclaves show comparable compositions of biotite and orthopyroxene. Embayed textures and high TiO2 content in biotite grains suggest high-temperature anatexis. On the other hand, the orthopyroxenes with inclusions and high Al2O3 content indicate peritectic origin. Moreover, reaction intergrowths of biotite with orthopyroxene grains have also been observed, suggesting that these grains were generated by the consumption of biotite. The Gaozhou charnockite has much lower zircon water content (135 ppm, median) as compared to that of the contemporary Opx-free granites (202-643 ppm, medians) in the Yunkai terrane, indicating dry primary parental melts. In addition, phase equilibria modeling constraints peak anatexis conditions at 860-870 ℃/6.2-7.0 kbar. Peritectic orthopyroxenes must have been generated by the incongruent melting of biotite under high-temperature granulitic facies in the lower crust. Subsequently, these grains were entrained and migrated by low water content melts to the upper crust. Therefore, overall observations favor a model of selective entrainment of source materials at a low magma water environment for the generation of the Gaozhou charnockite.

How to cite: yang, H. and Yao, J.: Generation of the charnockite by residua entrainment in water-deficient melts: insights from minerals composition and H2O-in-zircon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2231, https://doi.org/10.5194/egusphere-egu24-2231, 2024.

EGU24-2301 | ECS | Orals | GMPV2.1

What can we learn from X-ray diffraction and seismic velocities across the alpha-beta quartz transition at lower crust conditions?  

Giulia Mingardi, Julien Gasc, Matteo Ardit, Matteo Alvaro, and Alexandre Schubnel

Quartz, the most common mineral constituent of the Earth’s continental crust, undergoes the displacive α-β transformation at pressures and temperatures of the lower crustal conditions. This transition is associated with important variations in the thermodynamic properties (such as thermal expansion and isothermal bulk modulus) and is therefore thought to cause important seismic velocity contrasts that are distinguished by seismic tomography. The α-β transition is characterized by a non-linear increase in volume with temperature and an abrupt variation in bulk modulus, which, at the transition, drops from about 70 GPa to nearly zero within 10-15 K. Although well-known at room pressure, the behavior of quartz across the transition at high pressure, i.e., at Earth-relevant conditions, remains largely unexplored.

In this work, we have characterized this transition at high P-T conditions by means of X-ray diffraction and acoustic measurements. The experiments were performed at the European Synchrotron Radiation Facility (ESRF, beamline ID06) using a multi anvil press up to 3 GPa and 1400 °C. The measured velocities show a strong decrease of Vp toward the phase transition, followed by a steep increase in the β-field, reaching values higher than those in the α-field. In our data, this increase is not as large as that predicted by thermodynamic models using the known elastic properties of quartz (e.g., Abers and Hacker 2016). As anticipated, Vs is rather constant throughout the transition, resulting in major variations in the Vp/Vs ratio. The unit cell volume was calculated from the collected diffraction patterns. Contrary to the well-documented negative thermal expansion of quartz in the β-field at room pressure, the unit cell volumes obtained at high-pressure show a slight continuous volume increase during heating after the phase transition.

In conclusion, we document here that the behaviour of quartz across the α-β transition at high P-T is different from what has been previously predicted, which is likely a consequence of the poor knowledge of β-quartz thermo-elastic properties at high P-T. This could affect the interpretation of seismic data in the deep crust, which is currently based on extrapolations of the room-pressure behavior of the α-β quartz transition.

How to cite: Mingardi, G., Gasc, J., Ardit, M., Alvaro, M., and Schubnel, A.: What can we learn from X-ray diffraction and seismic velocities across the alpha-beta quartz transition at lower crust conditions? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2301, https://doi.org/10.5194/egusphere-egu24-2301, 2024.

In order to explore the favorable reservoir characteristics and diagenetic evolution laws of the Cretaceous Kukebai Formation in the Kekeya area of the southwestern Tarim Basin, and provide theoretical basis for oil and gas exploration and development in the study area, comprehensive data such as core, cast thin sections, and carbon and oxygen isotopes were used to carry out the classification of diagenetic facies types and the study of diagenetic evolution models. The results indicate that the reservoir of the Kukebai Formation in the study area is mainly composed of feldspar lithic sandstone and lithic feldspar sandstone, with mainly developed diagenetic processes such as compaction, cementation, and dissolution. The diagenetic stage is in the middle diagenetic stage A. The Kukebai Formation reservoir mainly develops four types of diagenetic facies: moderately compacted dissolution facies, moderately compacted cementation facies, strongly compacted compaction facies, and strongly cemented facies. Among them, the strong compacted phase becomes a dense reservoir due to mechanical compaction in the early stage of diagenesis, and is mainly distributed in the sand mud interbedded layers of sedimentary microfacies between river channels and estuarine dams; The strongly cemented phase is densified in the early diagenetic stage due to the precipitation of a large amount of carbonate cement, mainly developed in the sand mud interbedded layers near the mud end of underwater distributary channels and the sedimentary microfacies of estuarine dams; The dissolution effect of medium compacted dissolution phase sandstone is strong, and the reservoir properties are the best, mostly appearing in the upper part of distributary channel sand bodies with strong sedimentation and water accumulation dynamics; The medium compacted and cemented sandstone has moderate compaction, and the reservoir properties are relatively good. It mainly develops in the lower part of distributary channel sand bodies with strong hydrodynamics. There are two types of favorable reservoirs in the study area, namely the medium compacted cementation phase and the medium compacted dissolution phase sandstone.

How to cite: Wang, H. and Zhang, L.: Reservoir characteristics and diagenetic evolution of Kukebai Formation in Kekeya area, Southwest Depression of Tarim Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2730, https://doi.org/10.5194/egusphere-egu24-2730, 2024.

Serpentines are among the most abundant hydrous minerals in oceanic lithospheres formed by hydrothermal alteration of ultramafic mantle rocks (i.e. peridotites). Antigorite – the high temperature and pressure variety of serpentine – is considered to be the dominant water carrier within down-going oceanic slabs. The successive dehydration of antigorite during subduction of partially serpentinized oceanic lithospheres is strongly associated with the water cycle in the upper mantle and is expected to play an important role in the generation of arc magmatism (Ulmer & Trommsdorff, 1995; Schmidt & Poli, 1998), and influence rheological properties of oceanic slabs by processes such as dehydration embrittlement which is thought to trigger intermediate-to-deep focus earthquakes (Jung et al., 2004; Ferrand et al., 2017).

Antigorite is a hydrous phyllosilicate known for its polysomatism: The number of SiO4 tetrahedra m along its a-cell periodicity. Previous electron microscopy studies reported the existence of antigorite within a wide range of m values (~13-23) depending on the pressure (P) and temperature (T) conditions (Mellini et al., 1987; Wunder et al., 2001). However, there is a lack of the combined structural and thermodynamic evidence about the stability of the different antigorite polysomes along the P,T-paths of subducting oceanic lithospheres.

We use a theoretical mineral physics approach based on first principles density functional theory calculations to quantify the phase diagrams of the terminal dehydration reactions of antigorite with different m-values between 13-19 under subarc depth P,T conditions. Our results elucidate the significance of the compositional variations of antigorite on the dehydration of serpentinized oceanic slabs during the progressive stages of subduction.

How to cite: Ritterbex, S. and Plümper, O.: First principles investigation of the effect of compositional variations on the terminal breakdown of antigorite in subduction zones, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2878, https://doi.org/10.5194/egusphere-egu24-2878, 2024.

EGU24-2915 | ECS | Orals | GMPV2.1

Sustainable recovery of rare earth elements with eggshell waste calcite 

Rémi Rateau, Kerstin Drost, Melanie Maddin, Adrienn Szucs, Luca Terribili, Paul Guyett, and Juan Diego Rodriguez-Blanco

In November 2023, the European Union reached a provisional agreement on an European Critical Raw Materials Act, which encourages the local production, processing, and recycling of critical elements, notably the rare earth elements (REE). While indispensable for the green energy transition, their production is notoriously environmentally damaging, and efforts are being made to reduce this environmental footprint, for example via the use of secondary REE sources from waste or by the application of green chemistry and circular economy principles.

In this study, we investigated the potential of hen eggshell calcite waste to be recycled for the uptake of REE from industrial and waste streams. We interacted commercial eggshells with 50 mM multi-REE (La, Nd, Dy) solutions at 25 to 205 °C between three hours and three months. The resulting products were characterized by powder XRD and Rietveld refinement for quantitative phase identification; SEM electron imaging for structural characterization; SEM energy dispersive spectroscopy for elemental mapping and quantification of major and minor elements; and laser ablation ICP-MS for trace element mapping.

We observe a pervasive diffusion of the REE inside the eggshell calcite, along pathways formed by the intracrystalline organic matrix and calcite crystal boundaries, and without any partitioning of La, Nd and Dy. At 90 °C, calcite is observed dissolving and being replaced by kozoite spherulites, reminiscent of natural kozoite crystals. At 165 °C and 205 °C, an interface coupled dissolution-precipitation mechanism is observed, resulting in the complete dissolution of the calcite and its pseudomorphic replacement by polycrystalline kozoite. At 205 °C, kozoite itself is slowly replaced by hydroxylbastnäsite, the stable form of rare earth hydroxycarbonate, following a crystallization pathway previously established with inorganic calcite. Minor REE zoning at the eggshell grain scale is also observed, hinting at a potential use for REE separation.

Our results demonstrate two potential applications of eggshell waste for the sustainable recovery of REE from aqueous solutions: at low temperatures, as a mixed organic-inorganic adsorbent and absorbent; and at higher temperatures as an efficient sacrificial template for the precipitation of rare earth hydroxycarbonates.

How to cite: Rateau, R., Drost, K., Maddin, M., Szucs, A., Terribili, L., Guyett, P., and Rodriguez-Blanco, J. D.: Sustainable recovery of rare earth elements with eggshell waste calcite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2915, https://doi.org/10.5194/egusphere-egu24-2915, 2024.

EGU24-3030 | ECS | Posters on site | GMPV2.1

Differential adsorption of clay minerals: Implications for organic matter enrichment 

Tongxu Zhao, Shang Xu, and Qiyang Gou

The interactions between clay minerals and organic matter, specifically adsorption, are widely recognized as a crucial mechanism for promoting the preservation of organic matter within sedimentary environments. This paper discusses the genesis and adsorption of clay minerals, especially their influence on the process of organic matter enrichment in sedimentary environments. The composition of clay minerals found in sediments serves as an indicator of both the climatic and lithological characteristics of the provenance area. Smectite formation is favored in mafic provenance, while the coexistence of illite and chlorite suggests cold and arid conditions. Additionally, an abundance of kaolinite indicates intense chemical weathering of the provenance area. The physical and chemical properties of clay minerals and organic matter significantly influence adsorption. Smectite is thought to adsorb more organic matter due to its greater surface area. Selective adsorption of high molecular weight, aromatic, and aliphatic compounds dissolved organic matter onto mineral surfaces may have played a role in kerogen formation. Moreover, the preservation of organic matter via clay mineral adsorption is intricately linked to the sedimentary environment. Disparities in nutrient elements during the clay minerals synsedimentary period can impact biological productivity. Furthermore, the pH and solution metal ions of the water column influence the quantity and type of organic matter adsorbed. The contribution of adsorption to organic matter preservation is influenced by redox conditions, and this contribution can be observed through density separations. Additionally, we present several recommendations for future research. Firstly, diagenesis alters the clay mineral assemblage in sedimentary rocks. However, it may be possible to reconstruct the clay mineral assemblage based on morphological, mineralogical, and chemical composition characteristics. Secondly, studies have indicated that clay minerals can facilitate the precipitation of carbonate minerals, providing insights into the formation of abiotic carbonate minerals. Finally, the practical applications of clay minerals in shale oil and gas exploration are underscored, such as their ability to predict sweet-spot areas and control reservoir properties.

How to cite: Zhao, T., Xu, S., and Gou, Q.: Differential adsorption of clay minerals: Implications for organic matter enrichment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3030, https://doi.org/10.5194/egusphere-egu24-3030, 2024.

EGU24-4169 | ECS | Posters on site | GMPV2.1

Use of automated mineralogy for the quantification of pyrrhotite in concrete aggregates 

Bruno Titon, Josée Duchesne, and Benoît Fournier

Concrete is one of the most sought-after materials in our time, second only to water in importance to developed and emerging nations alike. It has been a crucial component of major infrastructure projects for thousands of years. In the year 2022 alone, China, the largest producer of concrete, manufactured approximately 2.1 million metric tons of cement, a key ingredient in modern concrete formulations. Various concrete mixes, tailored for specific applications, have been perfected and are widely used in the industry. In broad terms, concrete consists of about three-fifths sand and rock fragments (aggregates), one-fifth cement, and one-fifth water. This combination makes it the world's most widely used building material, particularly for large structures which are reinforced with steel rods. Aggregates can be sourced from crushed rock or naturally occurring sand and gravel, but the type of aggregate used significantly influences the overall properties and robustness of the final product. The mineralogical composition of the rock itself is closely related to the quality and resilience of the concrete. Understanding the mineralogy and chemistry of the lithotypes used allows for predicting their interaction with other concrete constituents, preventing undesirable chemical reactions. Such reactions can compromise the safety and resilience of the finished product, and ultimately prevent the use of materials that would otherwise perform poorly. Among the many concrete pathologies that may arise from the use of inadequate raw materials, internal sulfate attack (ISA) mainly occurs when sulfide-bearing aggregates are used. This leads to complex chemical reactions resulting in the oxidation of sulfide phases and the release of sulfur into the cement paste. Consequently, severe cracking and internal swelling significantly compromise concrete integrity. The European standard (EN 12620:2008) is a widely used guideline that recommends a total sulfur content in aggregates not exceeding 1.0 wt.%. This threshold is reduced to 0.1 wt.% when pyrrhotite is detected in the lithotype to be used as an aggregate. Given that pyrrhotite is the second most common sulfide found in nature, it is crucial to identify and quantify the various sulfide minerals that may be present and to understand how they can affect finished concrete structures. The use of automated mineralogy, represented by software systems such as QEMSCAN, emerges as a powerful solution for identifying and quantifying pyrrhotite and any other sulfide phases in aggregates for concrete. It is a scanning electron microscope (SEM)-based system that uses backscattered electron (BSE) image segmentation and simultaneous acquisition of energy-dispersive X-ray (EDS) spectra to classify mineral phases using a pre-defined list of mineral spectra. Preliminary results from QEMSCAN analysis of both thin sections and mounts comprised of ground rock of different grain sizes have been promising. This SEM-based system can analyze whole rock samples and crushed aggregates, providing accurate results over different size intervals. Despite the expected negative correlation between sample grain size and pyrrhotite content, the results vary from 2.71 to 5.59 wt.% for total pyrrhotite content in the analyzed samples. Moreover, when averaged over all grain sizes, these results align with those obtained through traditional optical petrography.

How to cite: Titon, B., Duchesne, J., and Fournier, B.: Use of automated mineralogy for the quantification of pyrrhotite in concrete aggregates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4169, https://doi.org/10.5194/egusphere-egu24-4169, 2024.

EGU24-4623 | Posters on site | GMPV2.1

Multi-spectroscopic detections of hydrated-silica in the Jezero crater    

Pierre Beck and the Supercam and M2020 team members

Introduction:  Hydrated silica has been detected from orbit in Jezero crater [Tarnas et al., 2019] and holds great promise for the astrobiology science goals of the M2020 mission and the MSR Program. Early entombment within an hydrated silica matrix has been shown to minimize the molecular degradation of microorganisms during advanced diagenesis [Alleon et al., 2016a,b; Alleon et al., 2018].

On sol 0910, a float rock was automatically selected by the AEGIS system after a rover drive when entering the margin unit from the Jezero delta top. The target is a light-toned partially buried float with lustrous appearance.

LIBS: The chemistry of 9/10 points reveal a homogeneous composition, enriched in SiO2. The average SiO2 for these 9 points is 75.0 wt.% while the average total of quantified oxides is 83.5 wt. %.  

VISIR reflectance: The reflectance spectra share an overall blue slope, and exhibit absorptions at 1.9 µm (H2O), 2.2 µm (X-OH) and 1.4 µm (OH & H2O). The chemistry derived from LIBS (mean Al2O3< 2 wt.%) leads to the attribution of the 2.2 µm band to Si-OH. All such absorptions are present within spectra of terrestrial hydrated silica.

What type of hydrated silica? The reflectance spectra show that this target contains both Si-OH and molecular water. The position of absorption bands departs from what is typically observed for opals and chalcedony is at present the closest spectral analogue in term of band depths and position.

What origin? A 2.2 µm band has been observed in the IR spectra from the fan top and the margin unit, together with carbonate signatures. The LIBS derived chemistry of the targets suggest that this 2.2 band is related to hydrated silica. This suggests that the formation of the hydrated silica is associated with carbonate formation (locally or in the catchment) and that AEGIS_0910A may have the same origin. One possible scenario that is being investigated is that this silica material could represent the precipitates from a fluid that dissolved the ubiquitous olivine found in Jezero floor and delta, and concomitantly precipitated carbonates that are abundant in delta-rocks and the marginal unit ([Calvé et al., LPSC 2024; Wiens et al., LPSC 2024]).

Here, IR spectroscopy reveals that this hydrated silica-rich material is more crystalline that the hydrated silica deposits previously reported on Mars from orbit and in situ at Marias Pass, Gale crater [Pan et al., 2021; Gabriel et al., 2022; Ruff et al., 2011; Rapin et al., 2018].

Summary: Two independent lines of evidence, IR and LIBS, reveal that the float rock analyzed on sol 910 is made of hydrated silica. This target is unique so far in the SuperCam dataset (> 500 targets), but may be linked to high SiO2 points observed in the carbonate-rich delta bedrock units. Based on IR, this rock seems more akin to a micro-crystalline type silica, in contrast to previous observations of silica from the ground. Such a target may have trapped and preserved biosignatures, together with unique information on the paleoenvironmental conditions of the Jezero crater.

How to cite: Beck, P. and the Supercam and M2020 team members: Multi-spectroscopic detections of hydrated-silica in the Jezero crater   , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4623, https://doi.org/10.5194/egusphere-egu24-4623, 2024.

EGU24-4658 | ECS | Posters on site | GMPV2.1

Carbonation experiment of basaltic crystals and glasses using supercritical CO2 under different PT conditions 

Andrea Pierozzi, Remi Rateau, Andrea Orlando, Daniele Borrini, and Juan Diego Rodriguez Blanco

Greenhouse gases, especially CO2, have been increasing worldwide. To address this issue, carbon capture and storage (CCS) technology has been researched and developed to decrease atmospheric CO2 concentrations. Among the various methods studied, mineral carbonation is an emerging technique that involves the reaction between Ca-Mg-Fe bearing basaltic rocks and CO2 to store it in the rocks through the formation of carbonate minerals. The CarbFix project in Iceland is an example of this method. However, there is still much to learn about the physicochemical relationships between water, dissolved ions, and growing crystals in complex multicomponent systems at the atomic and nanoscale, which are essential for the successful implementation of CCS in basaltic reservoirs.

One of the methods being explored in this study involves the utilization of supercritical CO2, which is achieved above the critical temperature and pressure of 30.97 °C and 73.773 bar, respectively. Under these conditions, CO2 exhibits both liquid and gaseous properties. This work shows the results of an experiment conducted in basaltic crystals and basaltic glasses at the temperature and pressure range of 100 and 200 ºC, and 64 to 79 bar, to investigate the reaction between CO2(sc), water, natural forsterite and basaltic glass, which have demonstrated that under these conditions we have the partial dissolution of the previous mineralogical phases, and the subsequent formation of new alteration phases, but also the precipitation of carbonates with Ca, Mg and Fe. We will compare our results with studies of carbonation of synthetic forsterite.  

How to cite: Pierozzi, A., Rateau, R., Orlando, A., Borrini, D., and Rodriguez Blanco, J. D.: Carbonation experiment of basaltic crystals and glasses using supercritical CO2 under different PT conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4658, https://doi.org/10.5194/egusphere-egu24-4658, 2024.

EGU24-4694 | Orals | GMPV2.1

Mechanistic insights into the fluorite-fluocerite-bastnasite transformation 

Luca Terribili and Juan Diego Rodriguez-Blanco

Fluocerite is a rare earth element (REE) fluoride mineral with chemical formula (REE)F3. It is found in nature as an accessory mineral in magmatic-hydrothermal REE ore deposits, including alkaline complexes and carbonatites, where is associated with REE fluorocarbonates (i.e. bastnasite, parisite, synchysite), REE-bearing fluorite, cerianite, monazite and xenotime. Due to its relatively scarcity in these deposits, fluocerite kinetics and mechanisms of crystallisation, its role in REE fractionation and as phase for the evolution of magmatic-hydrothermal REE mineralizing systems have not received a lot of attention in the past years. Recently instead, fluocerite is gaining interest as it was suggested to be a precursor phase of bastnasite. Bastnasite is one of the most important minerals for the extraction of REE, indispensable in modern world because of their wide range of hi-tech industry and in clean energy applications. For this reason, illuminating the mechanisms of fluocerite crystallization and its role in the evolution of REE deposits could significantly enhance our understanding of the genesis of REE fluorocarbonates. 
The present study has two main objectives: 1) To study the kinetics and mechanisms of the fluocerite formation at temperatures ranging from ambient to low hydrothermal (up to 200 °C) 2) To demonstrate in situ that fluocerite reacting in the presence of a CO3-rich solution can transform into REE fluorocarbonates in hydrothermal conditions. 
For the first purpose, fluocerite was synthesized by reacting pure fluorite (CaF2) powder with REE-bearing solutions at different temperatures. To achieve the second objective, synthetic fluocerite was reacted with Na2CO3 solutions at hydrothermal conditions up to 200 °C. Samples of solids were taken at specific time intervals to follow the ongoing of the crystallisation reactions. The nature of crystallising solids, their quantification and growth morphology were determined with a combination of powder X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive microscopy (SEM-EDS).
Our results showed that the fluocerite crystallisation rate decreases proportionally with the REE atomic number and increases with increasing T. The activation energy of crystallisation is similar irrespective of the REE used in the synthesis (~75 KJ/mol) while the activation energy of nucleation increases with the REE atomic number (80 - 96 KJ/mol). All fluocerites reacted with the CO3-bearing solutions transformed into bastnasite at all temperature, also forming cerianite in the Ce-bearing experiments. 

How to cite: Terribili, L. and Rodriguez-Blanco, J. D.: Mechanistic insights into the fluorite-fluocerite-bastnasite transformation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4694, https://doi.org/10.5194/egusphere-egu24-4694, 2024.

EGU24-4776 | Posters on site | GMPV2.1

Temporal growth of epitaxial layers in the CaCO3-REECO3OH system during mineral replacement processes 

Juan Rodriguez-Blanco, Adrienn Maria Szucs, Remi Rateau, Melanie Maddin, and Luca Terribili

Mineral replacement reactions are essential for the understanding of the genesis and chemistry of REE-bearing carbonatite deposits. Many of these reactions involve interaction of Ca-Mg and REE carbonate phases, leading to the formation of minerals with complex compositions and structures.

This study explores the oriented surface precipitation of REE carbonates during the interaction of individual and multiple REE-bearing aqueous solutions with calcite and aragonite (CaCO3) at low hydrothermal conditions (25-220 °C). This mineral-fluid interaction is translated into a temperature-dependent solvent-mediated surface precipitation and subsequent pseudomorphic mineral replacement of the CaCO3 seeds by newly formed REE carbonates. This complex replacement sequence includes the crystallisation of metastable kozoite (orthorhombic REECO3OH) via the formation of individual spindle-shaped crystals following a transient non-random orientation on the surface of the host grains, gradually covering their full surfaces.

Our experiments show that the likelihood of formation of the oriented overgrowth and its stability are controlled by structural constraints which in turn depend on four factors: temperature, ionic radii and ionic potential of the REE in the system, and dissolution rate of the host CaCO3 minerals. Also, we demonstrate that REE elements can be rapidly immobilized as REE hydroxicarbonates, even at low hydrothermal conditions. An explanation of the epitaxial overgrowth’s configuration and the atomic arrangement of the structures of the CaCO3 polymorphs and REE-kozoite will be discussed. 


[1] Szucs AM et al. Reaction Pathways toward the Formation of Bastnäsite: Replacement of Calcite by Rare Earth Carbonates. Crystal Growth & Design, 2021;21(1):512–527.
[2] Szucs AM et al. Targeted Crystallization of Rare Earth Carbonate Polymorphs at Hydrothermal Conditions via Mineral Replacement Reactions. Global Challenges. 2022;2200085.

How to cite: Rodriguez-Blanco, J., Szucs, A. M., Rateau, R., Maddin, M., and Terribili, L.: Temporal growth of epitaxial layers in the CaCO3-REECO3OH system during mineral replacement processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4776, https://doi.org/10.5194/egusphere-egu24-4776, 2024.

EGU24-5885 | ECS | Orals | GMPV2.1

Raman elastic geobarometry: investigating cation order in omphacitic clinopyroxenes 

Lisa Baratelli, Boriana Mihailova, Mauro Prencipe, Fernando Cámara, and Matteo Alvaro

Omphacitic clinopyroxenes exhibit widespread occurrence in various geological settings and rock types, making them promising candidates for Raman elastic geothermobarometry applications. Raman elastic geobarometry uses the deformation recorded by mineral inclusions to determine the pressure and temperature conditions under which they were entrapped. Raman scattering, which is highly sensitive to structural deformations, provides valuable insights into the variations in crystal structure that occur due to heating or compression. While several host-inclusion systems have been investigated, clinopyroxene inclusions have not been extensively studied. Therefore, the application of Raman elastic geobarometry to omphacites in different mineral hosts necessitates an accurate calibration of Raman-peak positions against hydrostatic pressure.

Natural omphacite crystals can exhibit cationic ordering associated with crystallization temperature, which affects their elastic behaviour. To address these aspects, we conducted a study on natural ordered (P2/n) and experimentally disordered (C2/c) omphacite crystals from Münchberg Massif (Germany). In situ high-pressure Raman spectroscopy measurements were performed using a diamond anvil cell. As expected, the frequencies of the modes increased with increasing pressure. By examining omphacite crystals with varying degrees of order obtained through isothermal annealing experiments, we observed that progressive cationic disorder primarily led to peak broadening, while changes in Raman peak positions were predominantly influenced by pressure variations.

Additionally, the chemical composition of omphacites influences the Raman-peak positions and their pressure evolution. Therefore, we analysed Fe3+-rich omphacites from Lugros and Camarate (Bétic Cordilleras, SE Spain), and Voltri (Italy) along with synthetic iron-free omphacites. This analysis is an initial step towards the chemical calibration of omphacites using Raman spectroscopy.

To gain a deeper understanding of the elastic behaviour of modes suitable for elastic geobarometry, we simulated the Raman spectrum of a fully ordered omphacite (Jd50Di50 composition) at different pressures using ab initio Hartree-Fock/Density Functional Theory simulations. The simulated data exhibited excellent agreement with experimental spectra, enabling us to comprehend the pressure dependence of specific modes. Leveraging these findings, we can calculate the entrapment pressure of omphacite inclusions still confined within their host rocks by determining Raman shifts of the main peaks alongside changes in cation order.

Our results provide valuable insights into the calibration and application of Raman elastic geobarometry for omphacitic clinopyroxenes. By considering the influence of chemical composition and cationic ordering, we have enhanced our understanding of the elastic behaviour of omphacite and its potential for geobarometric calculations. These findings offer a valuable tool for determining the pressure and temperature conditions of geological processes involving omphacitic clinopyroxenes.

How to cite: Baratelli, L., Mihailova, B., Prencipe, M., Cámara, F., and Alvaro, M.: Raman elastic geobarometry: investigating cation order in omphacitic clinopyroxenes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5885, https://doi.org/10.5194/egusphere-egu24-5885, 2024.

EGU24-5906 | ECS | Orals | GMPV2.1

Spectral characterization of organic matter is affected by polyvalent cations interaction 

Nisha Bhattarai and Ruth H. Ellerbrock

Abstract

Functional groups (e.g. alcohol, hydroxyl, carboxyl etc.) of soil organic matter are responsible for soil properties like cation exchange capacity or wettability. Functional groups can be characterized by spectroscopic procedures like Fourier transform infrared (FTIR) spectroscopy since the infrared light can introduce vibration modes within the groups. Only the light of an energy similar to the bonding energy of the C=O bond, for example, causes the absorption bands of the functional groups to show up at typical wavenumber (WN) regions in FTIR spectra. However, when the C=O group interacts with cations, the bonding energy may change thereby affecting the WN region of the absorption band. This change in WN (following organic matter (OM)-cation interaction) may limit procedures of automated spectral interpretation, which are mostly based on fixed ranges -determined from textbooks, or sets of single wave numbers determined by statistical approaches.

Our study aims to quantify the effect of OM-cation interactions on the spectral features (intensity and WN region of C=O absorption bands) in FTIR spectra. To quantify the effect of OM-cation interactions on defined functional groups as far as possible, we study mixtures of polygalacturonic acid (PGA; as a model substance for soil organic matter) with different polyvalent cations (Ca2+, Fe³+, Al³+) at different concentrations.

PGA-cation mixtures with different cation concentrations were prepared, freeze dried, and characterized using FTIR spectroscopy (KBr technique). A proton-cation exchange at the carboxylic acid groups during PGA-Cation interaction gives rise to a COO- band in FTIR. Since the cation effect is found in an earlier study to be stronger for the COO- band (1620-1550 cm-1) as compared to the C=O band, the interpretation of the FTIR spectra focuses on the COO- band. Compared to spectra of pure PGA, the spectra of all PGA-cation mixtures show a significant positive correlation between COO- band intensity and cation concentration. Additionally, a shift in the maximum of COO- band towards lower WN was observed for all cations, which depends on the kind of cations and increased with cation concentration.

Increase in intensity of the COO- band and the shift in WN region of COO- band maxima confirms changes in FTIR spectral features with cation addition and that those changes depend on the type of cation. The results suggest that type and concentration of cation should be considered when interpreting FTIR spectra of organic matter since both, change in intensity and shift in the WN of the band maxima, could restrict procedures of automated spectral interpretation, which mostly rely on fixed ranges (from textbooks), or sets of single wave numbers determined by statistical approaches. For a deeper understanding on the relation between OM-cation interactions, organic matter with increasing heterogeneity and complexity need to be studied.

How to cite: Bhattarai, N. and Ellerbrock, R. H.: Spectral characterization of organic matter is affected by polyvalent cations interaction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5906, https://doi.org/10.5194/egusphere-egu24-5906, 2024.

EGU24-8290 | ECS | Orals | GMPV2.1

First evidence of strong REE compatibility with pyromorphite Pb5(PO4)3Cl 

Kacper Staszel and Maciej Manecki

Constant development of high and green technologies makes rare earth elements (REE) more viable than ever. Relative scarcity of REE and lack of proper substitutes increase the demand for inexpensive and efficient methods of their recovery. Some new methods and technologies have been already proposed but their effectiveness leaves much to be desired. Most recently, precipitation in form of lead apatite has been proven to provide with very high levels of REE removal from aqueous solutions.

Substitution of REE in apatites has been broadly studied for calcium–phosphate apatite specimens, while lead–phosphates have been usually omitted. Recent studies suggested that precipitation of Pb and individual REE, induced by the presence of phosphates and Cl ions, results in near complete removal of cations from solutions in the form of REE-containing pyromorphite Pb5(PO4)3Cl. The goal of this study was to optimize the procedure. 

Pyromorphite (Pym) was precipitated from a solution of phosphoric acid (1:1) containing REE (each element at the concentration of 15 ppm) by addition of NaCl and Pb(NO3)2 (powder). The addition was conducted 5 times with very small amount of Pb relative to phosphates: 1/200, 1/100, 1/50, 1/20 and 1/10 of Pb needed for complete reaction with phosphoric acid. The amount of Cl was used in 1.5 times excess with respect to stoichiometric Pb. Each time solids and solutions were separated and sampled for the analysis.

The synthesis was carried out under atmospheric pressure, at an ambient temperature of about 21°C and at pH=3. Powder X-ray diffraction (XRPD) was used to identify the obtained phases, scanning electron microscopy (SEM) to examine the morphology of the crystals, energy-dispersive X-ray spectroscopy (EDS) for analysis of the elemental composition of solids, while solutions were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-OES).

Most REE are removed already at the first, lowest dose of Pb: more than 99% of La, Ce, Pr, Nd, Sm, Eu, and Gd; between 90 and 96% of Tb, Dy, Ho, and Er; between 80 and 50% of Tm, Yb, and Lu; 46% of Sc, 86% of Y, and 98% of Th disappear from the solution. After the third addition, REE are removed completely (except for Sc, which required 5 amendments). All these elements were removed from solution by precipitation of REE-containing Pym. An admixture of "phosphoschultenite" PbHPO4 also appears in the precipitate, which most likely does not contain REE (or contains much less than Pym).

These preliminary results indicate strong affinity of REE with Pym structure. In contrast to previous findings (Sordyl et al., 2023), a fractionation of REE was observed. Further analyses are in demand for better understanding of the mechanism of these processes which will allow for optimization of industrial applications.

This research was funded by National Science Centre research grant no. 2021/43/O/ST10/01282.

 

References:

Sordyl, J., Staszel, K., Leś, M., & Manecki, M. (2023). Removal of REE and Th from solution by co-precipitation with Pb-phosphates. Applied Geochemistry, 158, 105780. https://doi.org/10.1016/j.apgeochem.2023.105780

How to cite: Staszel, K. and Manecki, M.: First evidence of strong REE compatibility with pyromorphite Pb5(PO4)3Cl, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8290, https://doi.org/10.5194/egusphere-egu24-8290, 2024.

EGU24-8479 | Orals | GMPV2.1 | Highlight

Spectroscopy on Mars with NASA Perseverance rover 

Olivier Beyssac

The NASA Perseverance rover is exploring Jezero crater on Mars since february 2021 [1]. Perseverance’s main goal is to investigate the past geologic and environmental conditions of Jezero crater and seek evidence of past life. For this, the rover has characterized the local geology of the crater floor and is presently working in an ancient river delta. Then, Perseverance will explore the crater rim, and possibly some regions outside of the crater. In addition, the rover selects and collects the most compelling samples that will be retrieved and brought back to Earth by a future mission (NASA/ESA Mars Sample Return project) for more detailed study.

Perseverance uses a panel of spectroscopic tools based on the analysis of sunlight reflectance in the visible and near-infrared domains (MastcamZ, SuperCam), deep-UV (SHERLOC) and time-resolved (SuperCam) Raman, Laser Induced Breakdown Spectroscopy - LIBS (SuperCam) and X-ray fluorescence (PIXL). Some instruments can analyze the chemistry and mineralogy of rocks remotely up to several meters [2-3] while others work close to the rock for higher spatial resolution (~100 mm) and better textural control [4-5]. The rover is operated nearly every day and sends data almost immediately to Earth.

On the crater floor, Perseverance found igneous rocks: basaltic lava or pyroclastic flows [6] covering an olivine-rich cumulate [4,7]. The magmatic mineral assemblage, including the textural relationships, was carefully described: mostly Fe-rich pyroxenes in the basaltic flows, and a cumulate composed of dominant olivine with augite and pigeonite, as well as some phosphates and (Cr-)Ti-Fe-oxides in both units. The bulk of these rocks is weakly altered but Fe-Mg carbonates [8], sulfates [5] and various phyllosilicates [9] were detected showing that fluid-rock interactions locally occurred. After the crater floor, Perseverance began exploring the sedimentary rocks in the Jezero western fan, which is still in progress. On the fan, some float rocks show intense alteration to kaolinite followed by metamorphism [10].

Perseverance instruments which have an original design optimized for lightness, resistance to extreme conditions and performance will be introduced. Doing spectroscopy on Mars is challenging but these instruments have worked perfectly so far. A large amount of data, including some first-time achievements on Mars, have been collected and will be summarized with special emphasis on spectroscopic data.

[1] Farley et al., Science, 2022 ; [2] Bell et al., Science Advances, 2022 ; [3] Wiens et al., Sciences Advances, 2022 ; [4] Liu et al., Science, 2022 ; [5] Scheller et al., Science, 2022 ; [6] Udry et al., JGR Planets, 2023 ; [7] Beyssac et al., JGR Planets, 2023 ; [8] Clavé et al., JGR Planets, 2023 ; [9] Mandon et al., JGR Planets, 2023 ; [10] Royer et al., LPSC 2024.

How to cite: Beyssac, O.: Spectroscopy on Mars with NASA Perseverance rover, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8479, https://doi.org/10.5194/egusphere-egu24-8479, 2024.

EGU24-8723 | ECS | Posters on site | GMPV2.1

Quartz chemico-structural characterization: a tool for sediment source tracing 

Claire Aupart, Catherine Lerouge, Philippe Lach, Florian Trichard, Manon Boulay, Magali Rizza, Pierre Valla, Pierre Voinchet, Gilles Rixhon, and Hélène Tissoux

Quartz is ubiquitous within continental crust and can virtually be found within all rock types (plutonic, metamorphic and sedimentary). During erosion, weathering and sedimentation processes, it has a very high preservation potential and is often used to trace sediments production and transport dynamics. The QUARTZ project (Multi-methods characterization of quartz for source-to-sink tracing in alluvial sediment and dosimetry approaches – French ANR) aims to use quartz as a tracer for sediment sourcing river dynamics by combining conventional characterization method such as Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), Laser Induced Breakdown Spectroscopy (LIBS), and Cathodo-Luminescence (CL), with dosimetric methods, such as Electronic Spin Resonance (ESR) and Optically Stimulated Luminescence (OSL) which are more classically used for Quaternary sediment dating. To this end, one must define a robust quartz chemico-structural and dosimetric signature that can be compared from one sample to the other. We also aim to better understand ESR, OSL, and CL signals controlled by structural quartz defects. These can be either intrinsic (e.g. dislocations, missing/supplementary O or Si), or extrinsic (foreign atoms), each technique being more or less sensitive to these different defects.

In this study, we apply this multi-method approach to the various bedrock lithologies of the Strengbach catchment (ca.40 km²) draining a low mountain range located in the easternmost France (Vosges). These are largely dominated by crystalline metamorphic and plutonic rocks, with secondary Triassic sandstones (Buntsandstein). Bedrock samples have been treated mechanically and chemically to extract quartz grains. These grains have been analyzed using ESR and OSL techniques and mounted on thick sections (100 µm) for CL, LA-ICP-MS, and LIBS analyses. 100-µm thick-sections were used to prevent quartz tearing apart under LA-ICP-MS laser beam. Quartz characterization was completed by the study of whole-rock bedrock thick sections, analyzed with CL, LA-ICP-MS and LIBS approaches.

Preliminary results allow identifying specific quartz chemico-structural signatures not only depending on rock type (gneiss, granite, sandstone) but also on formation process (magmatic, recrystallized, metamorphic or sedimentary). Further comparison between quartz analysis in whole rock and in separated grains samples permit to assess the impact of the chemical treatment on the quartz signatures and to identify quartz populations likely to be more represented in the alluvial sediments produced by the different lithologies. Finally, ongoing analyses point out the complex contribution of trace elements to OSL, ESR and CL signals.

How to cite: Aupart, C., Lerouge, C., Lach, P., Trichard, F., Boulay, M., Rizza, M., Valla, P., Voinchet, P., Rixhon, G., and Tissoux, H.: Quartz chemico-structural characterization: a tool for sediment source tracing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8723, https://doi.org/10.5194/egusphere-egu24-8723, 2024.

EGU24-9462 | ECS | Orals | GMPV2.1

Petrography and Geochemistry of the North of Ilgin (Konya) Metavolcanic Rocks 

Oral Sarıkaya and Şenel Özdamar

In this study, investigated the geology, mineralogy, petrography and geochemistry of metavolcanic rocks in northern Ilgın (Konya). There are two Paleozoic and Mesozoic metamorphic rock groups in the study area. Alluvium and Neogene sediments are unconformably layered over these rocks. Paleozoic metamorphic group include metasediments and metacarbonates. This metamorphic group consist of metaconglomerate at their base and continue upward as metasandstone, metaquartzite, phyllite, schist, metachert, and metacarbonate at the top. Mesozoic metamorphic group consists of metasediments, metacarbonates, and metavolcanic rocks. There is metaconglomerate at the base and continue upward shale, metasandstone, and metacarbonate at the top. The main difference between the two groups is that the Mesozoic metamorphic group contains metavolcanic rocks. These metavolcanic rocks, which are the main subject of this study, occur at five different locations within the study area. These are Dereköy – Kurtlukaya Hill, Küçüktokmak Hill, Kocatokmak Hill, Göleç Hill, and Avdan Village. Metavolcanic rocks are commonly observed as massive metalavas, but in some areas they exhibit a significant degree of foliation. These rocks include quartz, feldspar, and muscovite. In some areas, quartz veins cut the rocks, and in others, iron oxides are observed. The metavolcanic rocks that are the main target of this study are metariolitic - alkaline metariolitic rocks. The rocks have undergone slight metamorphism, and foliation is clearly visible in some samples. The rocks consist of an average of 40-50% matrix and 50-60% quartz, alkali feldspar, muscovite and plagioclase minerals and exhibit a hemicrystalline porphyritic texture. The matrix of the rocks consists of fine-grained quartz, alkali feldspar and sericite minerals. These rocks’ SiO2 contents vary between 63.60-71.97%; K2O contents vary between 3.4-10.52%; Al2O3 contents vary between 15.78-18.56%; Fe2O3 contents vary between 0.94-4.26% and TiO2 contents vary between 0.02-0.57%. The rocks are calc-alkaline and shoshonitic in character. In addition, the rocks are peraluminous and silica-saturated. Trace element analysis shows that Ba is present in high concentrations (88–391 ppm) in  the rocks. Samples from Avdan and Dereköy have high Zr values (424–597 ppm) and Rb values (190–360 ppm). Eu values ​​(0.06–0.55) are low in all samples. Low Eu and high Ba are state that crustal contamination. The spider diagrams shows a decrease in Sr, Hf, and Ti elements, especially Eu, and an increase in other elements in the rocks. The negative anomalies observed in Sr and Eu elements indicate that fractional crystallization of feldspars. Enrichment of elements such as Th, Nb, and Zr indicate that crustal contamination. These rocks exhibit a relatively LREE-rich, HREE-poor composition, and show fractionation from LREEs to HREEs in normalized distribution pattern according to chondrite. The formation of the rocks includes fractional crystallization, assimilation-fractional crystallization, magma mixing and crustal contamination events. Ilgın metavolcanic rocks were formed as a result of magmatic activity that developed simultaneously with the collision after orogeny in the within plate environment.

Keywords: Geochemistry, Ilgın/Konya, metavolcanic rocks, petrography, Turkey.

How to cite: Sarıkaya, O. and Özdamar, Ş.: Petrography and Geochemistry of the North of Ilgin (Konya) Metavolcanic Rocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9462, https://doi.org/10.5194/egusphere-egu24-9462, 2024.

EGU24-9600 | ECS | Posters on site | GMPV2.1

Zn-Cr LDH/g-C3N4 heterostructure for estrone photodegradation: what is the effect of synthesis methods on materials’ properties and degradation efficiency? 

Anna Jędras, Jakub Matusik, Esakkinaveen Dhanaraman, Yen-Pei Fu, and Grzegorz Cempura

Photocatalysis is a promising water purification technology, that harnesses the power of light-induced reactions to degrade contaminants. Utilizing visible light in the reactions is imperative, as it comprises a significant portion of the solar spectrum, which aligns with sustainable practices. Graphitic carbon nitride (g-C3N4) is a photocatalyst active in visible light, characterized by high chemical and thermal stability, ease of synthesis, and relatively low cost. However, its performance is limited by charge carrier mobility and charge recombination. These limitations might be addressed by synthesizing heterostructures, i.e. composites containing two or more semiconductors. Heterojunctions between g-C3N4 and layered double hydroxides (LDH) have shown increased photocatalytic efficiency. LDH are crystalline, hydrotalcite-like materials that enhance the charge separation and light absorption by the heterostructure. These materials can be obtained through various synthesis methods, including coprecipitation and hydrothermal treatment, influencing their properties. Thus, this study aimed to compare heterostructures obtained by different synthesis routes and asses their photocatalytic efficiency.

Three synthesis methods were used to obtain Zn-Cr LDH/g-C3N4 heterostructures: coprecipitation, adsorption/coprecipitation, and hydrothermal treatment. For g-C3N4 preparation, melamine was heated at 550°C for 5 h. The coprecipitation method involved dissolving zinc and chromium nitrates in DI water, then adding it to a suspension of g-C3N4, while simultaneously adding a solution of NaOH and Na2CO3. The adsorption/coprecipitation method was based on adding zinc and chromium nitrates to a g-C3N4 suspension, then after 30 minutes adding a solution of NaOH and Na2CO3. The hydrothermal method included dissolving zinc and chromium nitrates in the g-C3N4 suspension, adding NaOH and Na2CO3, then placing the suspension in an oven for 24 h at 100°C. The obtained materials were characterized by XRD, SEM/TEM, XPS, TRFL, N2 adsorption/desorption, and photoelectrochemical measurements. The photocatalytic activity of heterostructures was assessed in batch experiments in aqueous solutions containing 1 ppm of estrone, with a 150 W LED lamp as a source of visible light.

The XRD patterns of obtained materials confirmed the formation of layered phases. The hydrothermal heterostructure was characterized by sharper reflections, which suggested higher structural order and/or larger crystallites. The average specific surface values (SBET) showed that the hydrothermal composite was characterized by the highest SBET - 124 m2/g. This indicated its higher porosity, compared to the materials obtained by other methods. The TRFL studies proved that the heterojunctions have lower recombination rates and longer lifetimes of charge carriers. The results of photochemical measurements suggested superior electronic conductivity and charge transfer efficiency for the hydrothermal heterostructure. The determined photoelectrochemical properties agreed well with the photocatalytic activity of heterostructures, which was the highest for the hydrothermal composite. This material led to a 99.5% estrone concentration loss after 60 minutes of reaction, in comparison to 49.9% and 75.8% loss assessed for the materials obtained by coprecipitation and adsorption/coprecipitation, respectively. The results of this study demonstrated the advantage of using the hydrothermal method to obtain LDH/g-C3N4 heterostructures with a high efficiency of pollutant photodegradation from aqueous solutions.

This research was funded by the AGH University of Science (Krakow, Poland), grant number 16.16.140.315.

How to cite: Jędras, A., Matusik, J., Dhanaraman, E., Fu, Y.-P., and Cempura, G.: Zn-Cr LDH/g-C3N4 heterostructure for estrone photodegradation: what is the effect of synthesis methods on materials’ properties and degradation efficiency?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9600, https://doi.org/10.5194/egusphere-egu24-9600, 2024.

EGU24-9623 | ECS | Posters on site | GMPV2.1

Efficient photodegradation of zearalenone: Unraveling the potential of photocatalysts based on kaolin group minerals 

Klaudia Dziewiątka, Jakub Matusik, and Grzegorz Cempura

The widespread occurrence of zearalenone (ZEN) in a variety of grain products and animal feed, coupled with its capacity to accumulate in the food chain, poses a significant health risk for both humans and animals. Its ability to induce estrogen-like effects may disrupt the body's estrogen levels, thereby contributing to reproductive system diseases, even at very low concentrations. The removal of ZEN from aqueous environment is predominantly challenging due to its weakly polar nature, compounded by its high thermal stability. Photodegradation, especially when applying mineral-based photocatalysts, stands out as a promising strategy for environmentally friendly mycotoxin removal. It not only demonstrates cost-effectiveness but also entails the production of negligible secondary pollutants.

Our research employed platy kaolinite (M), synthetic calcined kaolinite nanotubes (MNC), and halloysite purchased from Sigma-Aldrich (HS) as supports for TiO2, g-C3N4, or combination of TiO2/g-C3N4 semiconductors. Each synthesis was designed to consistently yield ~20 wt% of the semiconductor or its mixture in the samples, maintaining a TiO2 to g-C3N4 ratio of 1:1. The sol-gel method was used for TiO2 synthesis [1], while porous g-C3N4 nanosheets were prepared by heating melamine at 550°C, with the addition of ammonium chloride in a 1:1 ratio. The structural, textural, morphological, and light absorption properties of the obtained samples were characterized through XRD, N2 adsorption/desorption, UV-Vis DRS spectroscopy, Raman spectroscopy, SEM, and TEM..

The UV-induced photodegradation kinetics experiments (365 nm, 10 mW/cm2) were carried out at a consistent initial ZEN concentration of ~10 ppm. ZEN concentrations were determined with high-pressure liquid chromatography (HPLC). The TiO2-loaded photocatalysts exhibited the slowest photodegradation kinetics, resulting in the final removal of ~41.9% by the M-based sample, ~63.4% by the HS-based sample, and ~86.9% by the MNC-based sample. Conversely, the impregnation with g-C3N4 and TiO2/g-C3N4 led to materials exhibiting the fastest kinetics, effectively removing over ~99.9% of the initial ZEN concentration. Notably, the nanotubular-based photocatalysts demonstrated slightly faster kinetics than those observed for the M-based materials and were comparable to those noted for the pure g-C3N4. Analogous experiments under visible light irradiation highlighted the synergistic effect for the combination of  both semiconductors, characteristic of Z-scheme heterojunction structures. Among the MNC-based samples, the least efficient photodegradation was demonstrated by the g-C3N4-containing sample (~13.7%), slightly higher for the TiO2-containing sample (~20.3%), and the most efficient removal was observed for the sample containing both semiconductors (~36.6%).

The conducted experiments revealed a significant potential of kaolinite and halloysite nanotubes as carriers for semiconductors in the effective removal of ZEN from aqueous solutions. Future aspects of our research will involve detailed investigations into the degradation pathways of ZEN and the electrochemical characterization of the materials used.

This project was supported by the National Science Centre Poland, under a research project awarded by Decision No. 2021/43/B/ST10/00868.

References:
[1] Dziewiątka K., Matusik J., Trenczek-Zając A., Cempura G. (2023). TiO2-loaded nanotubular kaolin group minerals: The effect of mineral support on photodegradation of dyes as model pollutants. Applied Clay Science, Elsevier, volume 245, 107123. 

How to cite: Dziewiątka, K., Matusik, J., and Cempura, G.: Efficient photodegradation of zearalenone: Unraveling the potential of photocatalysts based on kaolin group minerals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9623, https://doi.org/10.5194/egusphere-egu24-9623, 2024.

EGU24-10421 | Posters on site | GMPV2.1

Effect of sample preparation on the FTIR DRIFT spectra in the case of soils with different organic material content 

Zoltán Szalai, Mate Karlik, Gergely Jakab, Anna Vancsik, István Gábor Hatvani, Dóra Cseresznyés, and Csilla Király

Diffuse Reflectance Infrared Fourier Transform Spectroscopy (FTIR DRIFT) is a widely used method for investigating soil organic materials. The existing literature suggests variations in sample preparation techniques for soil analysis. Notably, the powdering and drying method may influence the presence of organic materials, clay minerals, and carbonates. These minerals are occasionally found as coatings on different mineral surfaces and sometimes as part of the matrix within soil aggregates. This study examined four topsoils of distinct types from Hungary: Arenosol, Leptosol, Gleysol, and Phaeozem (WRB2022). The samples were pulverized both to < 250 µm and < 63 µmAnd also various procedures for drying were used: 1-hour drying sessions at 50 °C, 100 °C, 150 °C, 200 °C, and 250 °C, as well as overnight drying at 50 °C, 100 °C, and 150 °C. Additionally, samples were measured without undergoing extra drying at room temperature. This study aimed to focus on significant organic material bands.

Pulverization has a more pronounced effect on FTIR DRIFT spectra in soils with aggregates, furthermore, when the original soils contain a higher proportion of sand fraction. The drying method affects the measured absorbance values at the highlighted wavenumbers with an underlined influence on the aliphatic components range. Support of the National Research, Development, and Innovation Office (Hungary) under contract K142865, and Eötvös Loránd Research Network SA41/2021 are gratefully acknowledged.

How to cite: Szalai, Z., Karlik, M., Jakab, G., Vancsik, A., Hatvani, I. G., Cseresznyés, D., and Király, C.: Effect of sample preparation on the FTIR DRIFT spectra in the case of soils with different organic material content, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10421, https://doi.org/10.5194/egusphere-egu24-10421, 2024.

EGU24-11495 | ECS | Orals | GMPV2.1

Carbonates substitution in lead apatites – IR spectroscopic study 

Bartosz Puzio and Maciej Manecki

Similar to Ca-apatites, carbonate substitutions are also possible in Pb-apatites although they are still not fully characterized [1,2]. Therefore, for the first time, a comprehensive comparison of the IR spectra of synthetic Pb-apatite analogs has been carried out with a detailed examination of the rather often ignored carbonate substitutions. CO32- ions can be substituted in the apatite structure in two different positions: by substitution of an anion located in the X-position in the channel, such as OH- or halogen (A-type substitution), or by substitution of an anion in the tetrahedral position, such as PO43- or AsO43- (B-type carbonate substitution). This can be illustrated by the following chemical formula: Pb10-y(Na,K)y[(PO4)6-y(CO3)y][(X)2-2x(CO3)x], where x≈y. IR studies have shown that in apatites prepared at high temperature, most of the carbonates are located in the channel. Under low-temperature environmental conditions, the formation of AB-carbonated Pb apatites is much more plausible [3]. Some Pb apatites, such as fluoride apatites e.g. Pb10(AsO4)6F2, do not tend to incorporate carbonate at all, at least not during precipitation from solutions with CO32- concentrations similar to environmental (pCO2=10-3.5 atm). This is likely due to the greater ordering in apatite channels, where the fluoride anion occupies the mirror plane.

In the present work, various Pb-apatites containing As and V were prepared by precipitation from an aqueous solution in the presence of Na+ cations at room temperature and open to the air. The type of A- or B- carbonate substitution was determined in IR spectra collected at room temperature based on asymmetric stretching of the carbonate (ν3) and out-of-plane bending (ν2) modes. The high-frequency component of the ν3 region of the A-type carbonate for Pb apatites showed the greatest variability with chemical composition. For example, in Pb10(AsO4)6OH0.86(CO3)0.07 hydroxylmimetite, the bands at 1462 and 1421 cm-1 are attributed to A-type carbonate substitution, while the bands occurring at 1385 and 1348 cm-1 are associated with B-type. Compared to lead phosphates and vanadates, carbonate bending oscillations ν2 at 870 cm-1 are not apparent in arsenate Pb apatites due to overlap with the As-O stretching mode. In situ IR measurements were also carried out during temperature rise to 500 °C to determine the thermal stability of individual carbonate substitutions in the Pb-apatite structure. In general, most Pb-apatites begin to release carbonates around 300 °C. As the temperature increases, bands in the ν2 and ν3 carbonate regions begin to disappear until the apatite structure completely disintegrates.

 

References

[1] Yoder, C. H., Bollmeyer, M. M., Stepien, K. R., & Dudrick, R. N. (2019). The effect of incorporated carbonate and sodium on the IR spectra of A-and AB-type carbonated apatites. American Mineralogist: Journal of Earth and Planetary Materials, 104(6), 869-877.

[2] Kwaśniak-Kominek, M., Manecki, M., Matusik, J., & Lempart, M. (2017). Carbonate substitution in lead hydroxyapatite Pb5(PO4)3OH. Journal of Molecular Structure, 1147, 594-602.

[3] Lempart, M., Manecki, M., Kwaśniak-Kominek, M., Matusik, J., & Bajda, T. (2019). Accommodation of the carbonate ion in lead hydroxyl arsenate (hydroxylmimetite) Pb5(AsO4)3OH. Polyhedron, 161, 330-337.

How to cite: Puzio, B. and Manecki, M.: Carbonates substitution in lead apatites – IR spectroscopic study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11495, https://doi.org/10.5194/egusphere-egu24-11495, 2024.

EGU24-12017 | Posters on site | GMPV2.1

X-ray and Raman spectroscopy of jarosite and ammoniojarosite from several terrestrial localities 

Simon Bushmaker, William Nachlas, and Chloë Bonamici

Jarosite, a hydrous K-rich sulfate mineral, was found in fine-grain quantities on the Martian surface by the Opportunity rover in 2004. Jarosite found in some terrestrial settings can form a complete solid solution with ammoniojarosite through substitution of the ammonium ion (NH4+) which replaces K+ within its crystal structure. Requiring water and acidic conditions to form, jarosite stands as a potential indicator of ancient N-bearing environments on the Martian surface. The Mars Perseverance rover is currently exploring the Martian surface with analytical instrumentation that may be capable of detecting N-rich jarosite, including the SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) and the PIXL (Planetary Instrument for X-ray Lithochemistry) detectors. To investigate the detection of N in jarosite with Raman and X-ray spectroscopy, we analyzed several terrestrial samples of jarosite and ammoniojarosite using laser Raman spectroscopy and electron-excited Wavelength Dispersive X-ray Spectroscopy (WDS). Comparison of high wavenumber regions of Raman spectra with WDS spectra of N K-α X-rays on the same samples will be used to investigate detection and quantification of N as ammonium in jarosite.

How to cite: Bushmaker, S., Nachlas, W., and Bonamici, C.: X-ray and Raman spectroscopy of jarosite and ammoniojarosite from several terrestrial localities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12017, https://doi.org/10.5194/egusphere-egu24-12017, 2024.

EGU24-12115 | ECS | Posters on site | GMPV2.1

Apatite in the Sokli carbonatite complex, Finland 

Seppo Karvinen, Christoph Beier, and Aku Heinonen

Apatite is a ubiquitous mineral in plutonic carbonatites (magmatic carbonate-rich rocks) and associated rock types (Chakhmouradian et al., 2017). Carbonatites are enriched in incompatible elements such as P and rare earth elements (REE), which are accommodated into apatite structure among many other elements (e.g., Hughes and Rakovan, 2015), making apatite a suitable tracer for changes in magmatic-hydrothermal geochemistry.

Sokli carbonatite complex, located in eastern Lapland, Finland, is the westernmost intrusion of the Kola Alkaline Province (Vartiainen, 1980 and references therein). The Sokli complex encompasses multiple generations of carbonatite magmatism, which compositionally span from calcite carbonatite to dolomite carbonatite to late-stage Ba, Sr, REE-enriched dolomite-rich veins. Carbonatites are associated with several generations of phoscorites, exotic magnetite-apatite cumulates typically found in carbonatite complexes. Apatite is present in most rock types in the complex, from an accessory to a rock-forming mineral.

The Sokli complex has been studied for decades (O’Brien and Hyvönen, 2015), but the composition and role of magmatic apatite has not been discussed in detail outside of phosphorous mineralization studies. Previous studies indicate that with progressive fractionation the concentrations of Ba, Sr, REE, and F increase in whole-rock and mineral compositions (O’Brien and Hyvönen, 2015 and references therein). Questions that still remain open include whether apatite has recorded the proposed different magmatic and metasomatic stages and if apatite chemistry could provide arguments for the proposed liquid immiscibility relationship between carbonatites and phoscorites (Lee et al., 2004).

A variety of apatite-bearing rock types from the Sokli complex were sampled. The composition of apatite will be studied in situ for major and trace elements with electron microprobe analyzer (EPMA) and laser ablation inductively coupled mass spectrometry (LA-ICP-MS), respectively.

References cited:

Chakhmouradian, A.R., Reguir, E.P., Zaitsev, A.N., Couëslan, C., Xu, C., Kynický, J., Mumin, A.H., Yang, P., 2017. Apatite in carbonatitic rocks: Compositional variation, zoning, element partitioning and petrogenetic significance. Lithos 274–275, 188–213.

Hughes, J. M., Rakovan, J. F. 2015. Structurally robust, chemically diverse: apatite and apatite supergroup minerals. Elements 11, 165–170.

Vartiainen, H., 1980. The petrography, mineralogy and petrochemistry of the Sokli carbonatite massif northern Finland. Geological Survey of Finland, Bulletin 313.

O’Brien, H., E. Hyvönen. 2015. The Sokli carbonatite complex in Maier, W.D., Lahtinen, R., O’Brien, Hugh (Eds.), Mineral Deposits of Finland. Elsevier. 305–325.

Lee, M.J., Garcia, D., Moutte, J., et al., 2004. Carbonatites and phoscorites from the Sokli complex, Finland. In: Wall, F., Zaitsev, A.N. (Eds.), Phoscorites and Carbonatites from Mantle to Mine: The Key Example of the Kola Alkaline Province. The Mineralogical Society of Britain and Ireland, London, 133–162.

How to cite: Karvinen, S., Beier, C., and Heinonen, A.: Apatite in the Sokli carbonatite complex, Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12115, https://doi.org/10.5194/egusphere-egu24-12115, 2024.

EGU24-12281 | Posters on site | GMPV2.1

Exploring the Raman oxygen isotope signatures of calcite and vaterite 

Helen E. King and Aleks Živković

Exploring the Raman oxygen isotope signatures of calcite and vaterite

Oxygen isotope tracers have been increasingly used to differentiate between solid-state and fluid-mediated mineral transformation pathways (e.g., Julia et al. 2023). When 18O enrichment within oxyanion bearing minerals is analysed using Raman spectroscopy, the kinetically hindered formation of different isotopologues can also provide an in-situ timer for these processes (King et al. 2014). However, at present we assume that each isotopologue band in the vibrational spectrum has an equivalent intensity when present at the same concentration within the crystal structure. Here we test this hypothesis by exploring the vibrational spectra of two important oxyanion-bearing minerals, calcite and vaterite. These are polymorphs of CaCO3 and reflect a metastable, transition phase and the thermodynamically most stable mineral expected in many natural systems found at the Earth’s surface.

Here we have used a joint experimental and theoretical approach to demonstrate that isotopic substitution changes both band positions and band intensities to different extents, depending on the vibrational spectroscopy method used and the bands examined. Density functional theory simulations (King et al. 2022) show that for calcite, the most intense Raman bands, the υ1 symmetrical stretching, related to individual isotopologues are found to have very similar intensities and are not affected by changes in isotopologue distribution within the material. Splitting of some bands due to changes in symmetry correlate to observed effects in experimentally produced 18O enriched calcite.In contrast, vaterite vibrational bands were found to change more extensively upon isotope substitution, thus they can only be used to evaluate relative changes in the 18O concentration within the material. These results are expected to contribute to a deeper und less ambiguous understanding of evaluating isotopic enrichment effects in the vibrational spectra of calcium carbonates.

Julia et al. 2023 Chemical Geology, 621, 121364.

King et al. 2014 Crystal Growth & Design, 14, pp. 3910.

King et al. 2022 Crystals, 13, 48.

How to cite: King, H. E. and Živković, A.: Exploring the Raman oxygen isotope signatures of calcite and vaterite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12281, https://doi.org/10.5194/egusphere-egu24-12281, 2024.

EGU24-12774 | ECS | Orals | GMPV2.1

In-situ structural analysis of silicate supercooled liquids through deep-UV Raman spectroscopy  

Michele Cassetta, Francesco D'Amico, Barbara Rossi, Emanuele De Bona, Alessia Sambugaro, Mattia Biesuz, Renat Almeev, Francesco Vetere, Daniele Giordano, Francesco Enrichi, Nicola Daldosso, and Gino Mariotto

The understanding of the vitrification processes encompasses all the fields between geo- and material- sciences. Glass represents a non-equilibrium picture of its parental super-cooled liquid (SCL) and the last melt fraction quenched after a volcanic eruption. The SCL is usually read as a system that moves away from equilibrium without having enough time to explore the phase-space. In these conditions it is unable to find new configurations, causing a drop of the thermodynamic equilibrium and a glass is formed. This system is named non-ergodic and at eruptive temperatures represent a key component that may experiences fragmentation [1]. This particular state is generally referred to the thermal interval preceding the glass transition temperature (Tg, T at which the viscosity is 1012 Pa s) and the monitoring of its micro-structural evolution requires the less invasive experimental technique. With this regard we have used the deep UV-Raman spectroscopy to investigate a set of silicate model-glasses, loaded with different iron contents. This spectroscopic approach allows for the acquisition of fluorescence-free spectra with a maximized signal in the high-wavenumber region (between 850-1300 cm-1) thus providing the finest conditions for the assessment of the tetrahedral arrangement through the Qn deconvolution analysis (n represents the number of bridging oxygens) [2]. Here we correlate the trend of each Qn unit with temperature across the Tg-interval. Our results display a clear T-dependent rearrangement of the Qn distribution in function of iron content. Our finding, supported by differential scanning calorimetry, thermal dilatometry, Mössbauer, FTIR and ATR measurements, may deliver helpful insights into the thermal-dependent microstructural evolution through the Tg-interval and the viscous behavior of silicate SCLs.

  • [1] D. B. Dingwell, Science 273, 1054 (1996).
  • [2] M. Cassetta, B. Rossi, S. Mazzocato, F. Vetere, G. Iezzi, A. Pisello, M. Zanatta, N. Daldosso, M. Giarola, and G. Mariotto, Chem. Geol. 644, 121867 (2024).

How to cite: Cassetta, M., D'Amico, F., Rossi, B., De Bona, E., Sambugaro, A., Biesuz, M., Almeev, R., Vetere, F., Giordano, D., Enrichi, F., Daldosso, N., and Mariotto, G.: In-situ structural analysis of silicate supercooled liquids through deep-UV Raman spectroscopy , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12774, https://doi.org/10.5194/egusphere-egu24-12774, 2024.

EGU24-14196 | ECS | Orals | GMPV2.1

Characterizing life influence on Earth's mineralogy via mineral network analysis 

Shaunna Morrison, Anirudh Prabhu, Robert Hazen, Michael Wong, Donato Giovannelli, and Ahmed Eleish

Determining the habitability of planets remains a fundamental question in science and society. In this study, we harness network theory to explore the unique patterns exhibited by minerals and their mineralizing environments in both biotic and abiotic contexts throughout the evolution of Earth and other terrestrial bodies in our solar system [1-. By examining mineralogical networks across diverse planetary systems, including early solar system bodies, the early Hadean Earth (closely related to modern-day Mars), plate tectonics, and modern Earth, we gain valuable insights into Earth's history and the factors that have shaped the development and sustainability of life. Our investigation reveals distinct characteristics within biotic networks, setting them apart from their abiotic counterparts.

This research significantly advances our understanding of the intricate interplay between Earth and life. Network analysis offers deeper insights into the connections between minerals and living systems, providing invaluable perspectives on the emergence and co-evolution of life on our planet. Moreover, our findings contribute to identifying and characterizing planetary biosignatures, essential for the search for extraterrestrial life. Recognizing these unique patterns within biotic networks lays the groundwork for developing targeted exploration strategies for detecting potential biosignatures and interpreting the complexities of planetary environments.

Our innovative network analysis of minerals and mineralizing environments sheds new light on the relationships between Earth and life. By delving into the intricate connections within biotic and abiotic systems, we deepen our understanding of Earth's dynamic history and enhance our knowledge of potential habitats for life beyond our planet.

How to cite: Morrison, S., Prabhu, A., Hazen, R., Wong, M., Giovannelli, D., and Eleish, A.: Characterizing life influence on Earth's mineralogy via mineral network analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14196, https://doi.org/10.5194/egusphere-egu24-14196, 2024.

EGU24-14330 | Posters on site | GMPV2.1

Immobilization of radioactive Th by coprecipitation with lead apatites 

Maciej Manecki, Patrycja Wrona, Aleksandra Brzoska, and Kacper Staszel

There is a constant search for materials that could be used as geochemical barriers and fillers for radioactive waste storage containers. One of effective methods of immobilizing toxic elements is their precipitation in the form of sparingly soluble crystalline phases. The purpose of this study was to test the effectiveness of co-precipitation of Th from aqueous solutions in the form of crystalline lead phosphates. Such phases have high stability and low solubility and the presence of Pb has an additional effect on reducing the radiation.

Three sets of experiments were carried out by adding reagents into a solution containing non-radioactive Th at a concentration of 400 ppm:

(A) a solution containing PO43- ions (at a concentration of 1 g/L);

(B) a solution containing Pb2+ and a solution containing PO43- ions (at concentrations of 3.5 g/L and 1 g/L, respectively) added dropwise simultaneously;

(C) solutions containing Pb2+, PO43-, and Cl- ions (at concentrations of 3.5 g/L, 1.0 g/L, and 0.12 g/L, respectively) added dropwise simultaneously.

All experiments were repeated at pH = 3, 5 and 7. No reaction occurred in experiment (A), while in experiments (B) and (C) the solid phases crystallized, and the Th concentration dropped from 400 to about 0.05 ppm. In the absence of Cl (experiment B), the reaction at pH=3 led to the formation of "phosphoschultenite" PbHPO4 while at pH = 5 and 7 Th-bearing hydroxylpyromorphite Pb5(PO4)3OH was formed. In the presence of Cl ions (experiments C), Th-bearing pyromorphite Pb5(PO4)3Cl was formed over the entire pH range. Th was removed from solution by coprecipitation with Pb and incorporation of Th into lead phosphate structure.

The results showed that Pb must be present for Th to be effectively immobilized from solution in the form of phosphate phases. The presence of Cl is not as important as the presence of Pb in terms of removal efficiency, but it may be crucial for the long-term stability of the precipitated phases, since Pb5(PO4)3Cl has higher stability and lower solubility than Pb5(PO4)3OH. These findings pave the way for development of potential innovative techniques for immobilizing Th from waste and contaminated solutions, which could have implications for the safety and long-term viability of various nuclear waste disposal programs. This research was funded by National Science Center research grant no. 2021/43/O/ST10/01282.

How to cite: Manecki, M., Wrona, P., Brzoska, A., and Staszel, K.: Immobilization of radioactive Th by coprecipitation with lead apatites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14330, https://doi.org/10.5194/egusphere-egu24-14330, 2024.

EGU24-14683 | ECS | Posters on site | GMPV2.1

Mineralogy – the key to understanding and predicting the elution behavior of arsenic  

Donjá Aßbichler, Natalie Weichselgartner, Natalie Diesner, Melvin Kayalar, Carolin Otte, Soraya Heuss-Aßbichler, Saskia Tautenhahn, and Anke M. Friedrich

Arsenic is a world-wide serious health problem occurring in various types of rocks, soil, and contaminated water resources. However, it is not always an acute health problem, as concentrations are often comparably low. But recently, it gained increasing attention with the introduction of new laws in Germany (and the EU) regarding the deposition of excavated sediments, e.g., in the context of the construction of tunnels or the mining of gravel and sand etc. The decision on whether excavated material can be used as backfill or needs landfilling depends on the analysis and classification relative to specified limit values. In the latter scenario, this can result in a significant increase in costs. It is mandatory to determine the heavy metals and arsenic (among other parameters) in the solid sample and to produce and analyze an eluate of the sample to identify soluble harmful elements that could potentially contaminate the groundwater.

At a first glance, arsenic contents in solid and in eluate often show erratic patterns, which could not be explained. In clastic sediments, an often observed (weak) correlation between arsenic and iron in solid analyses led to the assumption that arsenic is bound in iron-hydroxides. However, a comprehensive examination of the chemistry and mineralogy of a large number of samples did not reveal any clear correlations. Therefore, we studied drill-core samples and sediment profiles of poorly consolidated Miocene clastic sediments, including gravel, sands, clay and silt from different areas of the Northern Alpine foreland basin (mostly from the Munich and Ingolstadt areas).

Based on geochemical analyses, we found different “arsenic-types”: Some samples show the expected correlation pattern for arsenic in the solid and the eluate. Some samples, however, show high arsenic in the solid and low arsenic concentrations in the eluate. Also, remarkably, samples with rather low arsenic contents in the solid and high arsenic in the eluate were observed. No systematic correlation with other chemical elements or with macroscopic characteristics, e.g. grain size, could be identified. Our detailed mineralogical investigation of more than 30 samples showed that XRD analysis, which is usually used to identify the mineralogy in the finest fraction, is not sufficient to explain this behavior. Therefore, we separated all mineral phases (also in the clay fraction) and analyzed their mineral chemistry (in particular their arsenic content) with SEM, their texture with high-resolution Keyence microscopy (2000x), and combined the results with extensive leaching experiments.

Our results imply that mineralogy is the key to understanding the elution behavior of arsenic. Regarding the binding characteristics of arsenic, three different mineral types can be distinguished: 1) Fe-, Si- and Al-Hydroxides (minor tourmaline, apatite and zircon) can bind arsenic relatively well (no arsenic in the eluate), 2) chlorite and mica can adsorb high amounts of arsenate but with a weak bond (high As in eluate) and 3) smectite which releases its arsenate step-by-step with the increasing degree of swelling. The study showed that only with a detailed mineralogical and mineral-chemical analysis profound predictions on the elution behavior of arsenic can be made.

How to cite: Aßbichler, D., Weichselgartner, N., Diesner, N., Kayalar, M., Otte, C., Heuss-Aßbichler, S., Tautenhahn, S., and Friedrich, A. M.: Mineralogy – the key to understanding and predicting the elution behavior of arsenic , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14683, https://doi.org/10.5194/egusphere-egu24-14683, 2024.

EGU24-14692 | ECS | Orals | GMPV2.1

Raman spectroscopy analysis of fluid inclusions as a tool in determination of origin of Colombian emeralds. 

Javier Garcia-Toloza, Camilo Betancur, Holman Alvarado, and Carlos Julio Cedeño

Gemological reports have gained a crucial role in today’s gemstone trading because they provide buyers and sellers with information regarding gem features, which in turn can be translated to monetary value. Although there is information about technics to separate Colombian emeralds from other countries, not much information is available about how to differentiate emeralds from the Western Belt (COC), and those from the Eastern Belt (COR), two main produced zones in Colombia, those districts more recognized are, Muzo and Chivor, respectively. This work aims to show the advances made in one of the techniques used in a gemological laboratory to determine the origin of emeralds.
The analysis of fluid inclusions via Raman spectroscopy can yield beneficial information regarding the chemical properties of mineral systems. Primary fluid inclusions trapped by emerald permit us to know the chemistry and the thermobarometric conditions of the mineralizing fluids. Fluid inclusions are usually three-phase inclusions with contain three or more phases including liquids, gases, and salt (halite). Sometimes they are multiphase with solids such as calcite. The gas phases are typically CO2, N2, and CH4 (Cheilletz et al., 1994; Giuliani et al., 1993; Giuliani et al., 1995; Romero & Hernandez, 1999; García-Toloza et al., 2017). Raman spectra of CO2 exhibit two bands near 1285 cm-1 and 1385 cm-1, this feature is well-known as the Fermi doublet (Fernandez, 1983; Howard-Locke, 1971); the distance between these bands is proportional to the fluid density (Rosso & Bodnar, 1995; Song Y. et al., 2003). 
The data of ∆ Fermi doublet suggest that values below 103.1 are exclusive from the COR, whereas there is an overlap from 103.1 to 103.4. Additionally, the position of the two main CO2 bands varies significantly between the two Colombian belts. The location of peaks from the COR are found at lower energy levels. Thus, this method may be used to estimate the provenance of some populations, the Fermi doublet is not only helpful to differentiate between the Colombian emerald belts but also between Colombian emeralds from samples from Brazil and Afghanistan.

How to cite: Garcia-Toloza, J., Betancur, C., Alvarado, H., and Cedeño, C. J.: Raman spectroscopy analysis of fluid inclusions as a tool in determination of origin of Colombian emeralds., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14692, https://doi.org/10.5194/egusphere-egu24-14692, 2024.

EGU24-16706 | ECS | Posters on site | GMPV2.1

Unravelling metasomatic agent in amphibole-rich upper mantle xenoliths from the Styrian Basin (W-Carpathian Pannonian Region): Insights from 3D Raman mapping of complex inclusions 

Justine L. Myovela, László E. Aradi, Tamás Spránitz, Máté Hegedűs, Patrik Konečný, János Kovács, and Márta Berkesi

The Styrian Basin, situated in the transition zone between the Pannonian Basin and the Eastern Alps, is believed to have formed above a lithospheric wedge, which have been affected by a subduction. The Late Miocene-Pliocene alkali basalts sampled the subcontinental lithospheric mantle beneath the area, bringing mantle xenoliths to the surface (e.g., [1] [2]). These xenoliths are amphibole-rich, indicating extensive modal metasomatism at mantle depth. Our goal is to better understand the possible fluid and melt-related processes in these xenoliths by studying fluid and melt inclusions in them. In the studied samples, one category of xenoliths contains both fluid and melt inclusions (co-entrapped), while the other contains only fluid inclusions. We carried out 3D confocal Raman mapping, Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM), Electron Microprobe Analysis (EMPA), and Scanning Electron Microscope with Energy Dispersive Spectroscopy (SEM-EDS). Our primary objectives are to 1) gain insights into the nature of metasomatic agents based on fluid and melt inclusions and 2) test the applicability of 3D Raman mapping on inclusions. The studied inclusions are primary (fluid inclusions) and pseudosecondary (fluid and melt inclusions), occurring in orthopyroxene, clinopyroxene, and amphibole. The fluid inclusions are irregular to negative crystal-shaped (3-100 μm), whereas melt inclusions are glass-rich with rounded to negative crystal shapes (4-15 μm).

A series of 3D Raman mapping on these fluid inclusions has revealed complex phase assemblages comprising fluid and solid phases (magnesite, silicate glass, pyrite, talc, anhydrite, and nahcolite). The fluid is dominated by CO2 (up to 99.3 mol%) and H2O (up to 8.7 mol%). EMPA indicates that the trapped silicate glass in the melt inclusions is H2O-bearing (up to 3.3 wt%) and exhibits an evolved composition (i.e., trachyandesitic composition with SiO2 between 54.31-60.65 wt%) relative to the host basalt of the studied xenoliths.

We discovered pargasitic amphiboles within SiO2-rich glass in the melt inclusion that co-entrapped with the CO2-H2O-rich fluid phase (where H2O content is likely high relative to mantle fluids). This strongly suggests that amphiboles were likely crystallized from an immiscible SiO2-rich melt and CO2-H2O-rich fluid that could have been circulating in the mantle wedge above a subducted slab. This immiscible component is suggested to be a metasomatic agent that modified this mantle portion beneath the Styrian Basin.  Furthermore, this study revealed that the laser-induced heating effect could overestimate sulfides in the 3D Raman models, while silicate glass could be underrepresented due to its low Raman scattering properties. However, complementary FIB-SEM serial slicing provides a clear outline of silicate glass in fluid inclusions. Despite these limitations, 3D Raman mapping has proven to be a powerful tool for unravelling complex phase assemblages in inclusions.

This research was supported by the NKFIH_FK research fund nr. 132418 to M. Berkesi. Part of this research was funded by the Doctoral School of Earth Sciences of the University of Pécs.

 

References:

[1]. Aradi et al., 2019; Földtani Közlöny, 149 (1). pp. 35-49.

[2]. Aradi et al., 2017; Tectonics, 36, 2987–3011.

Keywords: 3D Raman mapping, complex inclusions, mantle metasomatism, subduction zone, Styrian Basin.

 

How to cite: Myovela, J. L., Aradi, L. E., Spránitz, T., Hegedűs, M., Konečný, P., Kovács, J., and Berkesi, M.: Unravelling metasomatic agent in amphibole-rich upper mantle xenoliths from the Styrian Basin (W-Carpathian Pannonian Region): Insights from 3D Raman mapping of complex inclusions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16706, https://doi.org/10.5194/egusphere-egu24-16706, 2024.

EGU24-16793 | Orals | GMPV2.1

High-temperature Raman spectroscopy of quartz inclusions in garnet: a tool to investigate lower crustal rheology 

Mattia Gilio, Marta Morana, Ross J. Angel, Boriana Mihailova, and Matteo Alvaro

Earthquakes result from the brittle failure of rocks at depths and are primarily induced by far-field tectonic stresses. Despite this general understanding, the atomic-scale mechanisms triggering brittle failure in dry ductile crustal rocks remain elusive. Quartz, a widespread mineral in the lower crust, undergoes an instantaneous polymorphic transformation from the α to β phase under pressure and temperature conditions aligning with estimates for several lower-crustal paleo-earthquakes, recorded as pseudotachylytes. The α–β quartz transition is characterized by displacive reversibility. As α–quartz approaches the transition temperature (Tc = 847 K for a free quartz crystal at atmospheric pressure) under constant pressure, its volume increases nonlinearly without abrupt jumps. However, near the phase-transition temperature, the bulk modulus of quartz exhibits a notable drop from approximately 30 GPa to nearly zero, followed by an abrupt rise to over 70 GPa within 10 K temperature range (Lakshtanov et al., 2007).

Near the α–β transition, quartz inclusions within garnet hosts should develop substantial differential strain, thereby imposing strong differential stresses on the surrounding host crystal. We used in situ high-temperature Raman spectroscopy on quartz inclusions in garnet to monitor the structural deformation and atomic dynamics across the phase transition. The temperature-dependent behaviour of the phonon wavenumbers (ω) in quartz inclusions, particularly the hardening and disappearance of a minimum in ω(T) for A modes near 208 and 464 cm-1 (related to the α–β phase transition), along with the persistence of Raman activity at ~128 cm-1 and ~355 cm-1 above Tc, confirms the accumulation of abnormally high strain in confined quartz grains near the anticipated phase transition. The stored elastic energy in the inclusion is subsequently released through the inclusion-host boundary into the host during the α–β transition. This release causes the garnet around the quartz inclusion to fracture or, in some instances, shatter due to the significant differential stresses forming within the inclusion at its transition. Notably, inclusions of apatite and zircon within the same garnets remain unchanged under the same conditions, thereby excluding the possibility of fracturing being caused by the host garnet itself.

Our experiments show that the α–β transition of a single quartz inclusion in garnet is sufficient to fracture the host phase in a laboratory environment. This process can be upscaled to quartz-bearing rocks at lower crustal conditions and might provide the initial mechanical instabilities necessary to trigger ductile and/or brittle deformation in quartz-bearing rocks, eventually leading to earthquakes.

 

References

Lakshtanov, D.L., Sinogeikin, S.V., Bass, J.D., 2007. High-temperature phase transitions and elasticity of silica polymorphs. Physics and Chemistry of Minerals 34, 11-22.

How to cite: Gilio, M., Morana, M., Angel, R. J., Mihailova, B., and Alvaro, M.: High-temperature Raman spectroscopy of quartz inclusions in garnet: a tool to investigate lower crustal rheology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16793, https://doi.org/10.5194/egusphere-egu24-16793, 2024.

EGU24-17099 | Posters on site | GMPV2.1

Sulfuric acid speleogenetic by-products and secondary minerals in caves of the Mulapampa travertines (Western Cordillera, Andes, Peru) 

Andrzej Tyc, Justyna Ciesielczuk, Krzysztof Gaidzik, and Tomasz Powolny

Sulfuric acid speleogenesis (SAS) is a general cave formation process in carbonate rocks in the presence of sulfuric acid. Such caves are mainly formed at and above the water table by abiotic or/and biotic oxidation of hydrogen sulfide (H2S). One possible source of H2S may be volcanic activity. The oxidation of H2S produces sulfuric acid that immediately reacts with carbonate host rock, producing replacement gypsum and CO2.

The Western Cordillera in the Peruvian Andes, characterized by volcanic and tectonic activity, features substantial travertine deposits. Among the most interesting and, at the same time, less known are the Mulapampa travertines located in the vicinity of the active Ampato-Sabancaya Volcanic Complex (ASVC). There are numerous collapse sinkholes in the travertine cover, and within three of them, caves have been found. discovered in three of them. Particularly interesting is the Gruta con lago cave, the bottom of which is located at the level of the current water table (ca. 40 m below ground level). It does not have the characteristic morphology of active SAS caves, but several speleogenetic by-products – mainly thick gypsum deposits – are typical of such features.

Mineralogical studies of sediment samples from the lake at the bottom of Gruta con lago corroborated the sulfuric acid genesis of the cave. Native sulfur was detected in those samples, among others. Microscopic examination of native sulfur crystals reveals traces of substantial corrosion attributable to the activity of sulfur bacteria. In the same cave lake's bottom sediments, framboidal pyrites formed inside the biofilms (presumably of sulfate-reducing bacteria) were found. Common secondary minerals in SAS caves, such as barite or celestine, are present on the cave bottom and walls.

This research was funded by the National Science Centre (Poland), grant No 2020/39/B/ST10/00042, and the Institute of Earth Sciences, University of Silesia, Poland.

How to cite: Tyc, A., Ciesielczuk, J., Gaidzik, K., and Powolny, T.: Sulfuric acid speleogenetic by-products and secondary minerals in caves of the Mulapampa travertines (Western Cordillera, Andes, Peru), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17099, https://doi.org/10.5194/egusphere-egu24-17099, 2024.

EGU24-17632 | Posters on site | GMPV2.1

Dellen crater impact melt rock: pyroxenes as a proxy for melt thermal history and water content 

Sabrina Nazzareni, Gabriele Giuli, and Henrik Skogby

The Dellen impact structure is located in a ca. 20 km wide basin filled by two lakes in the east central Sweden. The complex structure is covered by a thick moraine deposit, and most impact melted material can be found as loose blocks and boulders scattered throughout the moraine. Geophysical measurements show the presence of a coherent impact melt body about 9 km wide and 200-500 m thick for which impact ages  between 90, 110, to 140 Ma were determined [1]-[2]. 

The impact melt glass (commonly referred as dellenite) consisting of phenocrysts of subhedral orthopyroxene (Wo4En63Fs33), skeletal plagioclase (average An59Ab38Or3), and euhedral magnetite within a glassy matrix of rhyolitic composition. MicroFTIR measurements performed in the glass matrix and euhedral glass blebs within the skeletal plagioclase show the presence of 1.4 wt% water in the rhyolitic glass. We estimated that the dellenite vitrified at ca. P=200-300 bar by comparing the glass water content  with the water solubility of a similar composition silicate melt following  Papale's model [3].

Dellenite orthopyroxene was studied by polarized FTIR spectroscopy, Mössbauer spectroscopy, single crystal X-ray diffraction and EMPA. They are iron rich enstatite (Wo4 En63 Fs33) with a Fe3+/Fetot ratio of 1.6%. They have very weak to absent OH vibrational bands in the IR spectra, corresponding to H2O contents ranging from 0 to 39 ppm H2O, a variability suggesting H loss during post-formation processes, which may occur via the relatively fast redox reaction Fe2+ +OH- =Fe3+ +O2- +½H2. 

In volcanic pyroxenes H loss may be a common process occurring at different moments from crystallization to post-eruption. However, H incorporation in pyroxene is associated with point defects governed by slow kinetics diffusion rates, which are retained in the structure when H is lost. By reversing the redox reaction the original H content of pyroxene can thus be recovered by thermal annealing experiments under reducing conditions [4]-[5].

In order to restore H that was possibly lost, dellenite pyroxenes were thermally annealed under hydrogen atmosphere (at 1 Atm) in a horizontal glass-tube furnace by thermal annealing experiments at 700°C for 17 hours. FTIR spectra were recorded after each heating step. All the samples increased their hydrogen content and the final average water content is 77 ppm. 

Cation partition as derived by the SC-XRD and EMPA were used to calculate the orthopyroxene closure temperature (Tc) which is expression of the cooling rate for the cpx-host rock. Preliminary results point to a high Tc (833°C) due to a quite fast host-rock cooling rate. 

A tentative model for the evolution of the rhyolitic portion of the Dellen impact melt is under development merging geophysical data with our experimental data on water content of pyroxene and glass, and pyroxene geospeedometry.  

References:

[1]Henkel H (1992) Tectonophysics 216, 31-40

[2]Mark DF Lindgren P Fallick AE (2014) Geological Society of London Special Publication 378, 349-366

[3]Papale P (1999) Am Mineral 84, 477-792

[4]Weis FA Skogby H Stalder R (2016)  Am Mineral 101(10): 2233-2247

[5]Nazzareni S Barbarossa V Skogby H Zanon V Petrelli M (2020)  CMP 175:87

How to cite: Nazzareni, S., Giuli, G., and Skogby, H.: Dellen crater impact melt rock: pyroxenes as a proxy for melt thermal history and water content, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17632, https://doi.org/10.5194/egusphere-egu24-17632, 2024.

EGU24-17688 | ECS | Posters on site | GMPV2.1

Are seismic waves robust enough to detect the presence of water in the lower part of the mantle transition zone? 

Rabindranath Mondal, Gaurav Shukla, and Swastika Chatterjee

The mantle transition zone (MTZ) is known to be potentially hydrated as laboratory
experiments have shown that the two major mineral phases namely wadsleyite (β-M2SiO4 ;
M: Mg, Fe) and ringwoodite (γ-M2SiO4; M: Mg, Fe) can accommodate significant amounts of
water in the form of hydroxyl ions in their crystal structure. Direct in-situ evidence of the
MTZ being (at least locally) hydrated has been derived from natural diamonds containing
hydrous ringwoodite inclusions (Pearson 2014, Nature). Hence, in this study, we have
investigated the crystal structure and the thermoelastic properties of Fe-bearing ringwoodite
as a function of temperature, pressure, and water content (0 wt%, 1.56 wt%, 3.3 wt%) using a
combination of first-principles density functional theory (DFT) and quasi-harmonic
approximation (QHA). Our calculation reveals that hydration in general causes a reduction in
the sound wave velocity of ringwoodite. However, the ‘reduction’ brought in by hydration is
significantly suppressed at pressures corresponding to the lower part of the MTZ.
Consequently, the sound wave velocities for the 1.56 wt% water-containing ringwoodite
model is found to become very similar to the sound wave velocities of the anhydrous
ringwoodite. However, when the water concentration is increased further to ~3.3 wt%, the pressure-induced
suppression at lower MTZ pressures though present is not significant. These findings indicate that though seismic
waves may not be able to precisely decipher the state of hydration of the lower part of MTZ
when the water concentration is less than 1.56 wt%, it is still robust enough to locate regions
of very high water concentration ~ 3.3 wt%.

How to cite: Mondal, R., Shukla, G., and Chatterjee, S.: Are seismic waves robust enough to detect the presence of water in the lower part of the mantle transition zone?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17688, https://doi.org/10.5194/egusphere-egu24-17688, 2024.

EGU24-18335 | ECS | Posters on site | GMPV2.1

The coherent solvus of disordered alkali feldspar determined with atom probe tomography 

David Heuser, Renelle Dubosq, Ge Bian, Elena Petrishcheva, Gerlinde Habler, Baptiste Gault, Christian Leopold Lengauer, Christian Rentenberger, and Rainer Abart

At high temperatures, alkali feldspar consists of a continuous solid-solution between the Na (albite) and K (K-feldspar) end members. Below about 600°C, a miscibility gap opens, the limits of which are determined by the so-called solvus. Alkali feldspar of intermediate composition tends to exsolve when cooled from temperatures of magmatic or metamorphic crystallization, forming an intergrowth of Na- and K-rich lamellae, a microstructure referred to as perthite. Initially, coherency is maintained across the lamellar interfaces and it may be preserved over geological times. Since the lattice parameters of alkali feldspars strongly depend on composition, the exsolution lamellae must be strained to maintain coherency at the interfaces. The elastic energy required to strain the lamellae counteracts exsolution and equilibrium compositions of coexisting coherent exsolution lamellae define a coherent solvus which lies below the solvus for strain-free phase equilibria. Segregation of Na and K and subsequent lamellar coarsening is achieved by thermally activated Na-K interdiffusion. Therefore, compositions and widths of the exsolution lamellae could be used to reconstruct cooling histories. Knowing the shape and position of the coherent solvus is key for the corresponding geo-speedometry applications.

To determine the coherent solvus, initially homogeneous disordered, gem-quality alkali feldspar was annealed at temperatures between 440°C and 560°C and at atmospheric pressure, which caused it to exsolve into coherently intergrown 10 to 20 nm wide lamellae, the compositions of which were directly determined with atom probe tomography.

The application of different annealing times showed that thermodynamic equilibrium was reached during the experiments. The obtained lamellar composition define points on the coherent solvus, which were for the first time measured directly for alkali feldspars.

Additionally, equilibrium Na-K partitioning experiments between NaCl-KCl melt and the same alkali feldspars as used for the exsolution experiments were performed at atmospheric pressure and at temperatures between 800°C and 1000°C to calibrate a thermodynamic mixing model supplemented by a model for the elastic energy required for coherent exsolution. The coherent solvus calculated from the thermodynamic model and the directly measured coherent solvus are in excellent agreement. This indicates that the developed models provide an adequate description of phase equilibria in coherent lamellar intergrowth. The directly measured coherent solvus and the models form a solid base for potential applications of geo-speedometry in coherently exsolved alkali feldspars.

How to cite: Heuser, D., Dubosq, R., Bian, G., Petrishcheva, E., Habler, G., Gault, B., Lengauer, C. L., Rentenberger, C., and Abart, R.: The coherent solvus of disordered alkali feldspar determined with atom probe tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18335, https://doi.org/10.5194/egusphere-egu24-18335, 2024.

EGU24-18687 | ECS | Posters on site | GMPV2.1

Differential scanning calorimetry measurements of mineral transformations at the extreme heating and cooling-rates experienced by mineral dusts ingested into aircraft engines 

Yike Bai, Stephen Covey-crump, Nicholas Bojdo, Merren Jones, and Alison Pawley

In the drive to develop more fuel-efficient aircraft engines to reduce the environmental impact of flying, engines are being designed to run much hotter. This is leading to a greater range of damaging interactions between the engine components and mineral dusts ingested into the engine during flight. To mitigate the effects of these interactions there is a critical need to understand mineral transformations (e.g., polymorphic changes, melting, glass transition), reactions, and mineral properties under much more extreme rates of heating and cooling than have been examined previously. Recent technological advances allow differential scanning calorimetry (Flash DSC) measurements to be made on small samples at temperatures of up to 1000 ℃, at heating/cooling rates of up to 50000 K/s, rates which comparable to those experienced by mineral dust particles inside a jet engine. Here we present two case studies, relevant in the engine context, that illustrate the capabilities of Flash DSC measurements.

A number of minerals ingested into aircraft engines undergo polymorphic transformations as they are rapidly heated inside the engine and these can have a profound effect on the accumulation rate of dust deposits on engine components. In our first case study we show the effect of heating/cooling-rate on the α - β-quartz transformation at rates between 10 to 10000 K/s (ambient pressures). During heating the temperature of the transformation increases from 573 to 608 ℃ over this heating-rate range, and the kinetics of the transformation are significantly modified.

Dust deposits may undergo melting inside an engine and infiltrate the porous coatings that are applied to engine components for thermal protection. This prevents the coatings expanding and contracting in response to temperature changes which, in turn, leads to their failure. Hence a knowledge of the viscosity of the melts (and hence infiltration-rate) and how this varies with temperature is important. Conventional methods of measuring viscosity are unable to access a considerable temperature range in which changes occur within the sample (e.g., crystallization) over the timescale of the measurement. The temperature dependence of viscosity may, however, be obtained from the heating-rate dependence of the glass transition temperature, and this is a measurement that can be made extremely rapidly by Flash DSC. In the second case study we show the temperature-dependence of viscosity over a temperature range previously inaccessible, for two CMAS melts that have compositions representative of those that are found in aircraft engines.

How to cite: Bai, Y., Covey-crump, S., Bojdo, N., Jones, M., and Pawley, A.: Differential scanning calorimetry measurements of mineral transformations at the extreme heating and cooling-rates experienced by mineral dusts ingested into aircraft engines, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18687, https://doi.org/10.5194/egusphere-egu24-18687, 2024.

EGU24-19040 | Orals | GMPV2.1

Mineralogical study of dedolomitization in cave environments –the Mravljetovo brezno v Gošarjevih rupah cave, central Slovenia 

Krzysztof Gaidzik, Filip Šarc, Justyna Ciesielczuk, Andrea Martín Pérez, Adrijan Košir, Bojan Otoničar, Tomasz Powolny, Andrzej Tyc, Vanessa Johnston, and Beata Gebus-Czupyt

Dedolomitization is a geological process where dolomite undergoes transformation into calcite via the influx of aggressive Ca-rich solutions derived from various sources (e.g., evaporite dissolution). This conversion can take place in diverse environments. Our study focuses on a unique occurrence of dedolomite within a cave environment in the Mravljetovo brezno v Gošarjevih rupah cave located in central Slovenia. The cave walls exhibit distinctive yellowish and reddish crusts and covers that originated from dedolomitization process developed within this cave system.

Macro- and microscopic observations reveal that yellowish lithologies are of sedimentary origin, where dominating dedolomite (i.e., replacive calcite) is associated by mainly detrital particles with a high content of quartz, muscovite, clay minerals, and lithoclasts. In contrast, red lithologies are associated with the transitional zone between sedimentary layers and the host rock dolomite, featuring peculiar calcite crystals with abundant pore space and intercrystalline iron oxides and clay. The transitional zone itself consists of a calcite mosaic with smaller dolomite remnant embedded within the calcite structure.

The primary objective of this study is to conduct a comprehensive mineralogical analysis (XRD, SEM-EDS, EMPA, μXRF, CL, and Raman spectroscopy), aiming to recognize their interrelationships and utilize them as proxies for understanding the processes leading to dedolomitization.

Dedolomitization is evidenced by the abundance of corroded dolomite rhombs infilled with calcite, coupled with the development of moldic (dissolution-related) porosity, and subsequent crystallization of vein calcite. Detrital quartz reveals embayed crystal boundaries, as well as rounded lithoclasts enriched in clay-group species (e.g., illite). Subordinate detrital apatite, rutile, and zircon were also recognized. Besides, some mineral phases of authigenic origin were detected based on their habits and textural relationships. These include clay-group species (i.e., kaolinite, illite, and/or possible mixed-layer clays), as well as S- and Na-rich apatite, and fluorite. The formation of dedolomite was followed by the decrease of Mg and increase of Fe as evidenced by elemental mapping. These changes can reflect oxidizing conditions and subsequent precipitation of Fe3+ in hematite or goethite/lepidocrocite mineral phases that stained dedolomitized regions red to yellow.

Furthermore, we seek to investigate the potential influence of these mineralogical dynamics on cave formation and speleogenesis. All these findings can contribute to a better understanding of geological and geochemical mechanisms governing dedolomitization processes within cave environments.

This work is funded by the Slovenian and Polish research agencies (ARRS and NCN) through the bilateral Polish-Slovenian research project CEUS (project code in Slovenia: N1-0226; project code in Poland: 2020/39/I/ST10/02357).

How to cite: Gaidzik, K., Šarc, F., Ciesielczuk, J., Martín Pérez, A., Košir, A., Otoničar, B., Powolny, T., Tyc, A., Johnston, V., and Gebus-Czupyt, B.: Mineralogical study of dedolomitization in cave environments –the Mravljetovo brezno v Gošarjevih rupah cave, central Slovenia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19040, https://doi.org/10.5194/egusphere-egu24-19040, 2024.

EGU24-20603 | Orals | GMPV2.1

Variation in Fe2+ / Fe3+ in hydrous silicates in subducted oceanic crust 

Donna Whitney, Sara Hanel, Max Wilke, and Angelika Rosa

A fundamental observation regarding oceanic subduction systems is that the starting material of subduction (MORB) is less oxidized than a major end-product (primitive magma in arcs), likely as a result of infiltration of mantle source regions by oxidized components from the subducted slab. Important redox-sensitive elements in slabs are S, C, H, and transition elements such as Fe and Mn. Fe is important because it is volumetrically significant, and release of other redox agents by dehydration reactions in subducted altered oceanic crust is controlled in part by Fe3+/∑Fe. Lawsonite (Lws) and epidote-group minerals (EGMs) are hydrous Ca-Al silicates that are key phases in subduction-zone H2O and element cycling owing to their composition and abundance, and the Lws-EGM transition has been linked to significant changes in fluid composition. Fe is a major component in most EGMs and a more minor but common component in Lws. Fe in Lws and metamorphic EGMs is generally assumed to be entirely Fe3+ that substitutes for Al in octahedral sites. However, results of Fe-XANES analyses for Lws and EGMs in blueschist and eclogite were acquired at the European Synchrotron Radiation Facility and show a wide range of Fe3+/∑Fe. Results for Lws appear robust because there are no signs of beam damage during analysis and there does not appear to be a strong orientation effect (linear dichroism). EGMs similarly show no beam damage effects but, in contrast to Lws, show significant variation in XANES spectra and resulting calculated Fe3+/∑Fe as a function of orientation. Although Fe in some Lws analyzed is entirely Fe3+, Lws and EGMs from New Caledonia blueschists contain substantial Fe2+. Work is in progress to determine what controls Fe3+/∑Fe in Lws and EGMs, but a preliminary conclusion is that Fe2+ in these phases in subducted oceanic crust may be greater than currently known, with implications for phase equilibria calculations and understanding of subduction redox conditions and processes.

How to cite: Whitney, D., Hanel, S., Wilke, M., and Rosa, A.: Variation in Fe2+ / Fe3+ in hydrous silicates in subducted oceanic crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20603, https://doi.org/10.5194/egusphere-egu24-20603, 2024.

EGU24-136 | ECS | Posters on site | GMPV2.3

Monazite age constraint on the Mahakoshal Supracrustal Belt, India 

Amit Mondal, Smruti Prakash Mallick, and Kamal Lochan Pruseth

The Mahakoshal Supracrustal Belt (MSB) marks the northern margin of the Central Indian Tectonic Zone (CITZ) along which are sutured the northern and southern crustal blocks of India. Monazite U-Th-Pb total ages in the Dudhi granite from a sample at the southern margin of the MSB are reported here. Although the age of the MSB was constrained between 1.8 and 2.2 Ga, a more precise upper age limit of ~2.1 Ga was proposed later. The present sample shows signatures of extensive hydrothermal alteration resulting in the replacement of orthoclase by oligoclase accompanied by precipitation of carbonate and microcrystalline silica. The monazites yield seven age peaks starting from 2053±65 Ma to 1457±39 Ma, suggesting multiple resetting of the ages. The most intense peaks are at 1951±19 Ma (n=29), 1851±20 Ma (n=20) and 1787±25 Ma (n=12), with only three points in the 2053±65 Ma population. Most likely, the Dudhi granite represents partial melting of the basement to the MSB at 2053±65 Ma and constrains the maximum age of the MSB, corroborating the upper age limit suggested earlier.

How to cite: Mondal, A., Mallick, S. P., and Pruseth, K. L.: Monazite age constraint on the Mahakoshal Supracrustal Belt, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-136, https://doi.org/10.5194/egusphere-egu24-136, 2024.

The behaviour of rare earth elements (REE), U-Pb, Sm-Nd, and Sr-Sr isotope compositions in accessory minerals provides a unique opportunity to track fluid sources and investigate trace element mobilization during fluid-assisted metamorphism. Metapelites of the Southern Marginal Zone (SMZ), Limpopo Belt (Bandelierkop formation), South Africa, experienced a ca. 2.7 Ga granulite-facies event in which the rocks underwent anatexis. The southern portion of the SMZ contains dispersed fragments of retrogressed metapelites with ubiquitous amphibolite facies assemblages including biotite, orthoamphibole, kyanite and a 2nd generation of garnet replacing cordierite, equilibrated under 660-600ºC and ≥ 0.6GPa. The hydrated metapelites contain graphite intergrown with the retrograde assemblages, indicating a mixed H2O-CO2 fluid and a rock-dominated system. However, the source of the fluids that caused the retrogression remains unclear. Previous studies suggested that hydrating fluids were originally internally derived from the crystallizing in-situ melts, in sediments containing biogenic graphite, or that an externally derived CO2 and H2O-bearing fluid infiltrated the metapelites through shear zone systems. For the latter, some studies have proposed that this occurred during uplift of the granulite directly after Neo-Archean peak metamorphism, while others have used rutile U-Pb ages of ca. 2.1 Ga to argue for Paleoproterozoic retrogression.

This study investigated the geochemistry of garnet, apatite, and monazite from the hydrated zone metapelites to understand the origin of the fluids. Garnet trace elements show two distinct populations described as Grt1 (Eu/Eu*=0.36) and Grt2 (Eu/Eu*=1.55). Monazite shows relatively homogeneous REE pattern for distinct samples with a slight variation in HREE and negative Eu anomaly (Eu/Eu*=0.20-0.38). As for apatite the REE pattern is variable and distinct within and between samples (Eu/Eu*=0.36-0.37). 2741 Ma to 2707 Ma U-Pb monazite ages suggest that the amphibolite-facies assemblages are mainly related to the ca. 2.7 Ga granulite-facies event. U-Pb apatite dating yielded younger ages ranging from ca. 2057 Ma to 2047 Ma. Sm-Nd isochron of apatite yielded an initial 143Nd/144Nd (0.50950 ± 0.00100; 2s; n = 21; MSWD = 4.6) equivalent, within uncertainties, to the monazite initial 143Nd/144Nd (0.50882 ± 0.00030; 2s; n = 30; MSWD = 0.81). Monazite and apatite preserved its primary 2.7 Ga Sm-Nd isotope signature, but the U-Pb apatite system was reset at ca. 2.05Ga by solid-state diffusion. Thus, apatite reacted in the presence of a disequilibrium fluid in the Neo-Archean, as evidenced by the REE chemical variation, but did not experience dissolution/reprecipitation processes.  

We propose that the retrogressed zone of the SMZ experienced a Neo-Archean peak granulite-facies followed by amphibolite-facies retrogression, in which an internally derived fluid interacted with the metapelites. This is supported by published Sm-Nd bulk rock compositions that follow the same evolution trend as these samples, indicating a closed system history in the retrogressed zone of the SMZ. The rocks also record a Paleoproterozoic, lower-temperature, amphibolite-facies re-heating event, responsible for the resetting of the apatite. Initial 87Sr/88Sr = 0.7130±0.0014 (2s; n = 19; MSWD = 13) indicates a continental origin for the fluids that crystallized the apatite.

How to cite: Mazoz, A., Stevens, G., Moyen, J.-F., Gonçalves, G., Ferreira, A., and Santos, R. V.: Unravelling fluid-rock interaction in the hydrated zone of the Southern Marginal Zone of the Limpopo Belt - South Africa: a geochemical investigation based on U-Pb geochronology and Sm-Nd isotope composition of monazite and apatite in metapelites , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-791, https://doi.org/10.5194/egusphere-egu24-791, 2024.

EGU24-1982 | ECS | Orals | GMPV2.3

The Isotope and REY geochemistry of fault-related calcites document syn-kinematic fluid distribution along the Val d’Agri faults (southern Italy) 

Giulia Schirripa Spagnolo, Stefano Bernasconi, Luca Aldega, Francesca Castorina, Fabrizio Agosta, Andrea Billi, Giacomo Prosser, Luca Smeraglia, and Eugenio Carminati

Calcite is a common syn-kinematic precipitate in upper crustal fault zones coating slickensides, forming slickenfibers, and infilling veins. Structural and geochemical analyses of fault-related calcites can be used to unravel the source, distribution, and mixing of parental fluids in association with past fault activity. Identifying deeply sourced fluids through syn-kinematic calcites is of paramount importance, as the correlation of the ascent of deep sourced fluids with strong earthquakes, may allow using hydrogeochemical modifications in groundwater as potential seismic precursors. In this study, we investigate the origin of syn-kinematic paleo-fluids that circulated along the Val d’Agri faults, in southern Italy. These faults bound an intermontane basin topping the largest onshore oil field in Western Europe. Since the Val d’Agri Basin is affected by natural seismicity and low magnitude oil production induced earthquakes, it is necessary to assess the potential threats of hydrocarbon fault leakage at shallow crustal levels. With this aim, we collected about 350 syn-tectonic calcites along high-angle extensional-transtensional fault zones. By combining macro- and micro- scale structural observations with carbonate isotopes (C, O, clumped, and Sr) and rare earth elements and yttrium (REY) geochemistry, we identified 5 fluid sources: (1) meteoric waters in geochemical and thermal disequilibrium with the host rocks, which interacted with superficial soil; (2) meteoric waters in geochemical disequilibrium and thermal equilibrium with the host rocks, which had limited interaction with the host rocks; (3) buffered fluids in geochemical and thermal equilibrium with the host rocks; (4) high temperature fluids in geochemical equilibrium and thermal disequilibrium with the host rocks, which ascended from the carbonate hydrocarbon reservoir; (5) hot meteoric waters in thermal and geochemical disequilibrium with the host rocks, which mixed with the deeply sourced fluids. The presence of multiple fluids is consistent with an open fault-related circulation system, which allowed mixing of shallow and deep fluids through the high-angle extensional-transtensional Val d’Agri faults. Given the societal and economic issues of this area, the recognized involvement of deep fluids during past fault activity is crucial for the context of oil exploration and production as well as for environmental monitoring. Furthermore, this suggests that the Val d’Agri Basin is an ideal region to explore fluid-fault relationships throughout the entire seismic cycle through local seismicity records and continuous groundwater monitoring.

How to cite: Schirripa Spagnolo, G., Bernasconi, S., Aldega, L., Castorina, F., Agosta, F., Billi, A., Prosser, G., Smeraglia, L., and Carminati, E.: The Isotope and REY geochemistry of fault-related calcites document syn-kinematic fluid distribution along the Val d’Agri faults (southern Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1982, https://doi.org/10.5194/egusphere-egu24-1982, 2024.

Magmatic activities in sedimentary basins provides abnormal heat sources and exert significant impact on the regional temperature field. In previous studies, the anomalous thermal effects of magmatic activities of multiple scales were studied. Small-scale intrusions (cm-m) can conduct high-temperature thermal baking of surrounding strata within tens to hundreds of meters. Basin-scale heat flow anomalies caused by mantle plume upwelling have also received increasing attention. In contrast, the thermal effects of large igneous plutons (several km to tens of km) have received little attention. A few studies have shown that the large intrusive bodies can affect the temperature field within a range of tens of kilometers. The Permian large igneous province is widely distributed in the Tarim Basin, forming several large plutons. The Manalik pluton is a large intrusive body in the northwestern Tarim, with a long diameter of up to 40 km. We have measured the clumped isotope of different calcite fabrics from the Ordovician carbonate intervals surrounding the contact aureoles of Manalik pluton. In-situ U-Pb dating will be applied to these fabrics to provide starting anchors for thermal history modeling using solid-state reordering models of carbonate clumped isotope. In addition, Silurian sandstones from the same area were collected for zircon (U-Th)/He age measurement and subsequent thermochronological thermal history inversion. Compared with conventional thermal indicators applied in deeply buried strata (e.g., vitrinite reflectance), the integration of the two thermochronological tools (Δ47/U-Pb and zircon U-TH/He) holds the advantage in more accurately quantifying the abnormal thermal effects of kilometer-scale intrusive bodies. The experimental results show that zircon (U-Th)/He and clumped isotope jointly constrain temperatures exceeding 200°C in Well Shengli 1 and Well Yingmai 35, which are closest to the Manalik pluton; the thermal anomalies identified in Well Yudong 2 are as high as 220°C; Well Yingmai 2 Well and Yingmai 34, which are far away from the igneous intrusion, were not affected by the thermal contact aureoles of Manalik pluton during the Permian period, and the current burial temperature is the highest paleogeothermal temperature experienced in historical periods. Based on the zircon (U-Th)/He and U-Pb/Δ47 simulation results, we reveal that the Manalik pluton has a significant thermal baking effect on the area within 20km, and the maximum temperature in the area close to the igneous pluton can exceed 220°C. The results of this study provide typical cases and inspiration for identifying and quantifying the thermal effects of contact aureoles in other basins where large igneous pluton are developed.

How to cite: Maimaiti, A., Tian, J., Cong, F., and Wang, Q.: Quantifying the anomalous thermal effects of contact aureoles of a large pluton in the Tarim Basin: Constraints from clumped isotope thermometry, in situ calcite U-Pb dating, and zircon U-Th/He thermochronology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2777, https://doi.org/10.5194/egusphere-egu24-2777, 2024.

EGU24-2875 | Orals | GMPV2.3

Petrographic and Geochemical Analysis of Upper Cretaceous Phosphorites in Şemikan, Turkey and Gusmari, Albania: Insights into Depositional Environments and Palaeoceanographic Conditions 

Ana Fociro, Hüseyin Öztürk, Agim Sinojmeri, Zeynep Cansu, Lavdie Moisiu, Yakup Çelik, Shaqir Nazaj, and Irakli Prifti

The Tethyan Phosphogenic Province is one of the widest of its kind, representing an outstanding period of phosphate deposition principally in the Upper Cretaceous-Eocene period. The main aim of this study is to compare the Turkish phosphorites occurring along the southern side of the Neo Tethyan Ocean due to suitable seawater temperature and upwelling oceanic currents with Albanian phosphorites were deposited in higher latitudes and colder climates, in the same ocean. The Şemikan (Türkiye) phosphorites consist mainly of cream-coloured (CCP) and locally reddish phosphorites (RP) occurring as lenses or concordant blankets within high-grade cream phosphorites. Based on microscopic examination, cream-coloured phosphorites consist of phosphatic pellets, intraclasts, bioclasts (fossilized shark teeth, ostracods etc.) and nonphosphatic components, with texture changing from wackestone to packstone, testifying shallow marine depositional environment. Whereas, Gusmari (Albania) phosphorites consist of laminated phosphorites (LP), of mudstone/wackestone texture, with planktonic foraminifera Globotruncanidae, where the phosphate is sedimentary, and alternating laminae of phosphate and pelagic carbonate. Besides this, under SEM-EDS, 5µm crystals of the major ore of uranium, UO2, were evidenced for the first time in LP. The mineralogical analyses showed that the CCP consisted of carbonate-rich fluorapatite, minor calcite and quartz. The RP consisted predominantly of carbonate-rich fluorapatite, hydroxyapatite, montmorillonite, and minor quartz. The LP consisted predominantly of calcite, carbonate-rich fluorapatite, hydroxyapatite, and traces of quartz. The mean P2O5 content of the CCP is 29%, RP and LP 14%, which is lower than that of other well-known global phosphorite deposits. The CaO content of the CCP, RP and LP ore is also higher than that of other global deposits because of a calcite matrix between phosphorite pellets. Based on preliminary results of trace elements CCP, RP and LP show a general trace element scarcity compared to the trace element averages of the world’s average phosphorites. The main reason for this deficiency is the rapid sedimentation or high burial rate in the sedimentary basin, which prevents the replacement of carbonate-rich fluorapatite by trace elements.

How to cite: Fociro, A., Öztürk, H., Sinojmeri, A., Cansu, Z., Moisiu, L., Çelik, Y., Nazaj, S., and Prifti, I.: Petrographic and Geochemical Analysis of Upper Cretaceous Phosphorites in Şemikan, Turkey and Gusmari, Albania: Insights into Depositional Environments and Palaeoceanographic Conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2875, https://doi.org/10.5194/egusphere-egu24-2875, 2024.

EGU24-3567 | Orals | GMPV2.3 | Highlight

Dissolution enables dolomite growth near ambient conditions 

Wenhao Sun

Crystals grow in supersaturated solutions. A mysterious counterexample is dolomite CaMg(CO3)2, a geologically-abundant sedimentary mineral that does not readily grow at ambient conditions, not even under highly supersaturated solutions. Using atomistic simulations, we show that dolomite initially precipitates a cation-disordered surface, where high surface strains inhibit further crystal growth. However, mild undersaturation will preferentially dissolve these disordered regions, enabling increased order upon reprecipitation. Our simulations predict that frequent cycling of a solution between supersaturation and undersaturation can accelerate dolomite growth by up to seven orders of magnitude. We validate our theory with in situ liquid cell TEM—directly observing bulk dolomite growth following pulses of dissolution. This mechanism explains why modern dolomite is primarily found in natural environments with pH or salinity fluctuations. More generally, it reveals that the growth and ripening of defect-free crystals can be facilitated by deliberate periods of mild dissolution. [Kim et al., Science: adi3690 (2023)]

How to cite: Sun, W.: Dissolution enables dolomite growth near ambient conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3567, https://doi.org/10.5194/egusphere-egu24-3567, 2024.

The Rb-Sr dating system has long been recognised as being susceptible to thermal perturbation. Its so-called closure temperature (TC) in biotite, the lowermost temperature at which interstitial diffusion of radiogenic 87Sr is no longer facilitated, is ca. 400 ˚C, much lower than e.g., the commonly used U-Pb system in zircon in excess of 900 ˚C. Newly developed in-situ analyses or Rb-Sr isotope systematics in biotite using a collision cell mass spectrometer (ICP-MS/MS) have now enabled rapid dating using multiple grains and with high spatial resolution (on a single grain scale). This now allows making use of the thermal characteristics of this dating tool. However, the modes and degrees of isotope reset are still poorly understood. Here, we analyse rocks from the Kohler Range in Antarctica for their Rb-Sr systematics in biotite. The plutonic rocks formed as part of the active Permian Gondwana margin (ca. 280-260 Ma). Whilst two samples record their original Permian age, two other samples yield cretaceous ages (~100 Ma), consistent with regional magmatic activity during the breakup of Gondwana. Two samples with mixed populations of micas confirmed a partial reset in this rock, and thereby the full reset for the Cretaceous ages. An intriguing aspect is that reset is predominant in spot analyses with higher Rb/Sr, making these sections apparently more prone to thermal reset, likely through higher diffusion potentials. We interpret the resetting of the system as a response to thermal perturbation of the igneous rocks with no apparent petrographic footprint. It is demonstrated that in-situ Rb-Sr dating of igneous micas in plutons can be used to date magmatic flare-ups in rocks that can be hundreds of millions of tears older. The technique thus holds immense potential to decipher the thermal histories of terranes that otherwise remain undetected and may be used to shed new light on a large number of suspect Rb-Sr (mixed?) ages with no apparent geologic meaning.

How to cite: Nebel, O., Ali, Z., and Raveggi, M.: Magmatic flare-up recorded in Rb-Sr reset-ages during Gondwana break-up, Kohler Range, Marie Byrd Land, Antarctica , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4508, https://doi.org/10.5194/egusphere-egu24-4508, 2024.

EGU24-5344 | Posters virtual | GMPV2.3

Preliminary insights on uranium-bearing Jurassic phosphorites of the Ionian zone, Albania, their distribution and genesis 

Agim Sinojmeri, Ana Fociro, Giovanna Della Porta, Giovanni Grieco, and Sajmir Beqiraj

Phosphorites are well-known, worldwide, for accommodating a significant amount of U relative to other sedimentary rocks, due to the crystal structure of apatite where U substitutes Ca. In Albania, uranium-bearing Lower Jurassic phosphorites form a distinctive horizon identified across the entire Ionian zone. Two different types of U-bearing phosphatic deposits are identified within the Lower Jurassic carbonate succession in Albania; one, stratigraphically younger, layered and parallel to carbonate strata and the other due to infiltration in older, brecciated carbonates. The first type consists of lenticular shape deposits of limited lateral extension intercalated in thin-shelled bivalve packstone/rudstone, possibly corresponding to the Toarcian Bositra-rich organic rich “Posidonia” shales of Austria and Germany. The phosphatic horizon is confined by dark gray J2 limestone on the top, while the bottom shows signs of an early erosion. Their extent varies from 5-10 m to 100-160 m, while their thickness varies from 0.3 to 6 m. The radioactivity measurements indicate that the intensity of gamma radiation varies from 0.6 to 1.66 µSv/h, while the uranium content varies from 50 to 230 ppm, the highest values corresponding to the P2O5 peak of 32.66%. The second type of phosphorite mineralization developed in a widespread horizon throughout the Ionian zone. Its extension varies from 1.5 to 8 km, composed of continuous zones up to 0.5-1 km with some small interruptions. Uranium-bearing phosphatic deposits occur as the infiltrated matrix of breccias (caused by hydraulic or tectonic stress, not of sedimentary origin) made of angular clasts of Pliensbachian inner carbonate platform facies of the J1 (peloidal and oncoidal packstone/grainstone with Siphovalvulina foraminifers and Palaeodasycladus mediterraneous dasyclad algae). The intensity of gamma radiation varies from 0.5 to 1.1 µSv/h, uranium content varies from 50 to 150 ppm and the P2O5 highest peak is 15%. In accordance to the first data achieved, the uranium-bearing phosphorites of Early Jurassic age in Albania formed in deep, oxygen-depleted marine conditions as suggested by the abundance of thin-shelled bivalves. The well-documented early Toarcian Oceanic Anoxic Event driven by an increase in nutrients linked to high volcanic emissions of CO2 may have favoured the formation of the phosphate deposits. The intensive tectonic events associated with the Alpine Tethys Ocean opening during the Early and Middle Jurassic should be the main factor causing the brecciation and controlling the formation of later infiltration mineralization.

How to cite: Sinojmeri, A., Fociro, A., Della Porta, G., Grieco, G., and Beqiraj, S.: Preliminary insights on uranium-bearing Jurassic phosphorites of the Ionian zone, Albania, their distribution and genesis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5344, https://doi.org/10.5194/egusphere-egu24-5344, 2024.

The Dizi series formed on the southern passive margin of a small oceanic basin on the Southern Slope of the Greater Caucasus and is exposed in the structural zone of the same name. The series is composed of metaterrigenous phyllite-like and volcanogenic rocks of the Devonian-Triassic age; marbles also are quite widespread in the series. During the Variscan orogeny, all rocks of the series underwent low-temperature regional metamorphism; later, in the Middle Jurassic time, intensive contact metamorphism took place. The object of presented research is marble, found in the rocks of the series both in the form of lenses and blocks. Interest in the study of marbles spread in the Dizi series is caused by several factors, namely, there is still no consensus on the position of marbles in the series, their detailed geochemical study has not been carried out, and the conditions of their formation have not been determined. There is an opinion that the Dizi series represents part of the Triassic Upper Karakaya complex, which was probably deposited in the forearc of the southern margin of Laurasia. The marbles are included in the series as exotic blocks of shallow marine Carboniferous and Permian limestone, most likely formed in Gondwana. During the study of the Dizi series marbles petrographic and geochemical research methods were applied. Petrographic characteristics of the marbles from all outcrops show a similar mineral composition, and structure and texture as well. The authors analyzed the main components, RE, and REE of the Dizi series marbles. The ratios Ca VS Mg, Mg/Ca VS SiO2, and Sr VS Mg/Ca show that the protolith of the marbles was pure limestone. The reconstruction   of the deposition conditions of the marble protolith, based on the concentrations of Sr, Rb, and Ba, indicates the formation of limestones in the conditions of the continental margin. The Ce-negative anomaly observed in the marble samples is possibly due to the existence of an oxygenated marine environment, probably of shallow water conditions. These conditions fully correspond to the tectonic interpretation of geochemical data from other metasedimentary rocks of the series. The results of the presented studies confirm that the marbles under consideration were formed in situ, together with the other rocks of the Dizi series in the conditions of the continental slope and its foot on the southern passive margin of a small oceanic basin of the Southern Slope of the Greater Caucasus.

How to cite: Javakhishvili, I., Tsutsunava, T., and Beridze, G.: About the marbles of the Dizi series (Greater Caucasus): geochemical features, the nature of the protolith, and paleoecological conditions of their formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5609, https://doi.org/10.5194/egusphere-egu24-5609, 2024.

Microbialite development in the Ediacaran Qigebrak Formation of the Tarim Basin, Northwest China: An examination of characteristics, distribution, and paleoceanographic reconstruction

Xudong Chen1,2, Qilu Xu1,2

  • National Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao 266580, China;
  • School of Geosciences, China University of Petroleum (East China), Qingdao, 266580, China

 

The Upper Ediacaran Qigebrak Formation in the Tarim Basin of NW China preserves abundant and well-preserved microbialites with primary textures. These provide valuable insights into Precambrian sedimentology and paleoceanography. Our study focuses on elucidating the relationship between paleoceanic conditions and the development of these microbialites to understand their Precambrian origin.

A comprehensive analysis of Ediacaran outcrops in the northwestern Tarim Basin identified 12 distinct microbialite types, ranging from mafic (F1) to flat-laminated stromatolite (F12). These comprise F2 (micrite dolomite), F3 (granular dolomite), F4 (bonded sand debris dolomite), and spongiomicrobialite variants (F5-F7). Additionally, we observed F8 (fenestral tectonic thrombolites), F9 (micrite thrombolites), and diverse stromatolite dolomites (F10-F12). Their occurrence is spatially distributed: F1 and F2 in the nearshore supratidal low-energy zone; F3, F4, and F7 in granular beach and microbial mound zones; F5 and F8 in the environmental transition zone; F6 and F11 in the lower intertidal high-energy zone; F10 predominantly in the upper subtidal high-energy zone; and F9 and F12 in both upper intertidal and lower subtidal low-energy zones.The shale-normalized REE patterns of these microbialites exhibit weak negative Ce anomalies, weak positive Eu anomalies, and positive La anomalies, suggestive of suboxic seawater deposition. Their chemical signatures, characterized by low V, Ni, and Co concentrations, high Sr content, and Sr/Cu ratios exceeding 50, collectively indicate warm and arid paleoclimatic conditions. Compared to F9, F6, F10, and F11 show lower V/(V+Ni) values, higher Mg/Ca ratios, and stronger LREE and MREE deficits, suggesting formation in shallower, more dynamic, saline, and oxygenated waters.

Our findings offer fresh perspectives on the formation mechanisms of Precambrian microbial rocks and paleo-oceanic reconstruction.

How to cite: Chen, X. and Xu, Q.: Microbialite development in the Ediacaran Qigebrak Formation of the Tarim Basin, Northwest China: An examination of characteristics, distribution, and paleoceanographic reconstruction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5704, https://doi.org/10.5194/egusphere-egu24-5704, 2024.

EGU24-5861 | ECS | Orals | GMPV2.3 | Highlight

U-Pb geochronology of Quaternary pedogenic carbonates and teeth from archaeological sites of Zarqa Valley, Jordan 

João Carlos Cerqueira, Nick M. W Roberts, Giancarlo Scardia, Fabio Parenti, Francisco Ladeira, and Walter Neves

Dating Quaternary carbonates and phosphates beyond the range of U-series geochronology is challenging, but recent studies have shown potential using the method of LA-ICP-MS U-Pb geochronology. Terrestrial materials altered and produced by pedogenic processes are particularly challenging, as they are usually rich in common Pb and poor in U; however, they provide some of the rare opportunities to directly date important archaeological artefacts. Our aim is to advance the age constraints of the hominin presence in the Zarqa Valley, Jordan, an important geomorphological feature with the oldest hominin artefact outside Africa. Along with new Ar-Ar geochronology of sequence-bounding basalts and new palaeomagnetic constraints, our approach is to: (1) review published U-Pb data of 2019; (2) conduct LA-ICP-MS U-Pb analyses in various pedogenic carbonates (calcrete) that cap the artefact-bearing deposits along with mammoth fossil remains; and (3) review the regional 234U/238U activity ratio estimate required for calculation of accurate U-Pb ages.

A previous attempt to date hominin artifacts in the valley yielded an age of 1.98 ± 0.20 Ma for calcrete material, which is a weighted mean of several individual U-Pb isochrons derived from laminated calcretes, cracks, pore spaces and cement, and corrected by an initial 234U/238U activity ratio of 1.5 ± 0.5. We calculated an alternative, statistically favourable, age based on pooling the data into a single Tera-Wasserburg regression, resulting in 1.93 ± 0.44 Ma.

Our LA-ICP-MS analysis thus far has not yielded a new significant age, but we have focussed on understanding the U and Pb compositions in a range of materials, including calcretes, rhizoliths, fossil coatings and Mammalian fossils. Biogenic spherulite laminae in laminar calcrete have higher U (0.56 ± 0.064 ppm) and lower Pb contents (0.61 ± 0.15 ppm) compared to abiogenic cracks and cement (0.33 ± 0.084 and 0.9 ± 2 ppm, respectively). Although far from desirable for U-Pb geochronology, for now, the spherulite laminae seems to be the most suitable micromorphology to date calcrete. Coarse spar of rhizoconcretions have very low U contents (0.07 ± 0.35 ppm), leading to unfavourable U/Pb ratios. Two fragments of a mammoth molar from an artefact-bearing deposit have been analysed; one is part of the crown having dentine and enamel, and the other one is dentine of the root. The crown and root fragments have high U concentrations of 33 ± 11 and 13.7 ± 9.9 ppm, respectively, but with their high Pb contents they still yield a low spread in U/Pb ratios and very imprecise lower intercept ages. Using LA-ICP-MS mapping to better identify areas of alteration, we pooled U-Th-Pb spot data from regions with low Y (<5 ppm), Mn (<50 ppm), Al (<100 ppm), Th (< 0.05 ppm) and high P (> 7200 ppm), which correlated with the central portion of the dentine. These data yielded an age, using the combined U-Pb and Th-Pb calculation, of 1.9 ± 1.1 Ma; although very imprecise, it shows potential for further refinement.

How to cite: Cerqueira, J. C., Roberts, N. M. W., Scardia, G., Parenti, F., Ladeira, F., and Neves, W.: U-Pb geochronology of Quaternary pedogenic carbonates and teeth from archaeological sites of Zarqa Valley, Jordan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5861, https://doi.org/10.5194/egusphere-egu24-5861, 2024.

EGU24-9818 | Orals | GMPV2.3 | Highlight

Mountains from sand grains: Advances in detrital provenance applied to orogens 

Chris Mark, Roland Neofitu, Gary O'Sullivan, Stijn Glorie, Thomas Zack, Delia Rösel, Dan Barfod, David Chew, J. Stephen Daly, Peter Clift, and Yani Najman

Detrital geochronology is a powerful tool to interrogate the sedimentary archive of (paleo-)hinterland tectonism, metamorphism, and exhumation, and can also be applied to modern river sediment as a first-pass tool to establish regional bedrock ages. The popular zircon U-Pb detrital geochronometer has seen widespread adoption for these tasks (4,173/5,100 results for the search term detrital geochronology also contain the term zircon U-Pb; Clarivate Analytics Web of Science). However, zircon fertility is strongly biased to intermediate to felsic source rocks. Moreover, zircon crystallization is volumetrically limited in metamorphic terranes which do not achieve anataxis (e.g., Moecher & Samson, 2006), and is typically restricted to rim overgrowths which are vulnerable to mechanical destruction during fluvial transport, and which are challenging to detect and analyse (e.g., Campbell et al., 2005).

Therefore, it is desirable to develop complementary provenance tools for sub-anatectic settings, as well as tools targeting more abundant rock-forming minerals for use with small-volume samples (e.g., drillcore). Established alternative detrital phases include the U-Pb system in apatite, monazite, titanite, and garnet. The advent of LA-ICPMS systems equipped with mass-filtered online reaction cells now also permits the routine use of β-decay systems by overcoming parent-daughter isobaric interferences. These include Lu-Hf in garnet and apatite, and Rb-Sr in K-phases including K-feldspar and mica (Rösel & Zack, 2022; Woods 2016). K-phases are also amenable to conventional Ar-Ar detrital geochronology.

Here, we present case studies of emerging detrital provenance techniques, with particular application to modern and past orogenic systems.

Campbell, I., et al., 2005. Earth Planet. Sci. Lett. 237, 402-432,  doi: 10.1016/j.epsl.2005.06.043

Moecher, D., & Samson, S., 2006, Earth Planet. Sci. Lett. 247, 252–266, doi: 10.1016/j.epsl.2006.04.035

Rösel, D., & T. Zack, 2022. Geostandards and Geoanalytical Research 46.2, 143-168, doi: 10.1111/ggr.12414.

Woods, G. 2016. Agilent Application Note. Agilent Technologies, Cheadle.

How to cite: Mark, C., Neofitu, R., O'Sullivan, G., Glorie, S., Zack, T., Rösel, D., Barfod, D., Chew, D., Daly, J. S., Clift, P., and Najman, Y.: Mountains from sand grains: Advances in detrital provenance applied to orogens, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9818, https://doi.org/10.5194/egusphere-egu24-9818, 2024.

The fault system within petroliferous basins plays a pivotal role in governing the migration, accumulation, and preservation of oil and gas resources. Accurate determination of the timing of fault activities is critical for reconstructing the history of tectonic evolution and for the analysis of hydrocarbon systems. Conventionally, this determination is achieved through the analysis and interpretation of seismic data. However, this method's effectiveness is often constrained by the quality of the seismic data, typically yielding only an approximate timeframe for fault activity. This limitation poses significant challenges in precisely identifying the periods of fault activity, which is essential for the analysis of their impact on hydrocarbon accumulation. Calcite, a commonly developed vein mineral in response to fault activities, is noteworthy in this context. The use of LA-ICP-MS U-Pb dating for fault vein calcite has been established as an effective technique to reveal time information of fault activity. The Tuoputai area, situated within the Tarim Basin, is recognized as one of the exploration hotspots with a complex tectonic evolution history. In particular, the strike-slip faults connecting Lower Cambrian source rocks with Ordovician carbonate reservoirs are instrumental in hydrocarbon migration and accumulation. In this study, the TP39 fault zone in the Tuoputai area, recognized for its rich hydrocarbon content, was selected for detailed analysis. We initially analyzed seismic data to obtain the approximate period of fault activity, followed by LA-ICP-MS U-Pb dating of calcite veins from core samples, to precisely determine the fault activity time. Additionally, the study incorporated the analysis of oil fluid inclusions in the calcite veins to comprehensively analysis the impact of fault activities on hydrocarbon accumulation. The seismic data indicated that the TP39 fault zone has mainly experienced three activity periods, including the Caledonian (542-416 Ma) to Hercynian (416-251 Ma), Indosinian (251-199.6Ma) and Himalayan (65.5 Ma-present) periods. In situ U-Pb dating of calcite veins from Ordovician reservoir cores in two wells within the fracture zone yielded ages of 446.79±2.67 Ma, 443.63±1.31 Ma, and 278.23±2.11 Ma, defining two significant active events in the TP39 fault zone during the Late Caledonian (~440 Ma) and Late Hercynian (~280 Ma), respectively. Furthermore, fluid inclusion analysis in calcite veins revealed a high prevalence of yellowish-green and bluish-green fluorescent oil inclusions, followed by blue fluorescent oil inclusions. The corresponding Th results from coexisting water inclusions indicated that the mainly phases of crude oil charging occurred during the Late Caledonian and Late Hercynian periods, followed by the Himalayan period, correlating well with the U-Pb dating results. This indicated that the fault activity during the Late Caledonian and Late Hercynian periods opened pathways for crude oil migration from the source rocks to the reservoirs. This study used the absolute dating method to constrain the activity time of the fault, demonstrating its impact on hydrocarbon accumulation, which is of great significance to basin structural research and oil and gas exploration.

How to cite: Xie, H. and Tian, J.: Fault activity history under absolute age constraints and its impact on hydrocarbon accumulation: A case study of the Tuoputai area in the Tarim Basin, China , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10059, https://doi.org/10.5194/egusphere-egu24-10059, 2024.

EGU24-11037 | ECS | Posters on site | GMPV2.3

Multistage carbonation of the Variscan ophiolite? Insights from geochemical and isotopic diversity of ophiolite-hosted carbonates 

Błażej Cieślik, Anna Pietranik, Jakub Kierczak, Alicja Lacinska, and Vojtěch Ettler

The mantle section of the ophiolite sequence is composed of ultramafic rocks, abundant in magnesium silicates. When exposed to crustal depths, these minerals become thermodynamically unstable and often interact with fluids of different provenance and chemistry. Ophiolite-hosted carbonates are one of the most widespread secondary phases resulting from interactions between silicates and CO2-rich fluids. There is ample evidence that carbonation of ultramafic rocks can occur in various geological settings and across a broad range of P-T conditions (Plümper & Matter, 2023). Therefore, accurately identifying the source of the fluids responsible for carbonation could contribute to a more comprehensive understanding of the long and complex evolution of the ophiolites.

In this study, we investigate carbonates hosted by the two ultramafic massifs (Szklary and Braszowice) of the Central Sudetic Ophiolite (CSO) (NE Bohemian Massif). This ophiolitic complex represents a late Devonian oceanic lithosphere formed in the slow-spreading regime. The complex story of the CSO includes prograde metamorphism, reaching its climax within the amphibolite facies, emplacement of syn- and post-Variscan magmas, as well as tropical weathering event(s) in the Cenozoic. Carbonate mineralization appears mostly as extensive veins and vein-like structures within partially serpentinized peridotites and serpentinites. The vast majority of veins in both localities exhibit a high modal abundance of cryptocrystalline magnesite accompanied by chalcedony or quartz. Field investigations revealed that carbonate veins containing magnesite-dolomite and calcite-dolomite are comparatively less common occurrences and they are mostly seen in the Braszowice ophiolitic fragment. In some samples, hydrous magnesium silicates co-occur with the studied carbonates. Based on both bulk and single-spot chemical composition (ICP-MS/ES and LA-ICP-MS) of carbonates, discrepancies and similarities have been observed between two ultramafic massifs. The concentrations of several trace elements (Ni, Al, Mn, Sr, Ba, Fe) noticeably vary between Szklary and Braszowice. Moreover, varied chemical compositions have been pinpointed among veins sampled at different depths. Strontium isotope composition was analyzed for fraction dissolved in HCl. At least two groups of carbonate veins can be distinguished based on their 87Sr/86Sr ratios. Veins sampled from the Braszowice pit floor, exhibiting Mgs or Mgs ± Dol or Cal ± Dol paragenesis, consistently display 0.7064 - 0.7065 values. Carbonate veins located at shallow depths in Braszowice and Szklary, primarily composed of cryptocrystalline Mgs or Mgs ± Qz, show 87Sr/86Sr values ranging from 0.7070 to 0.7113 suggesting input from fluids derived from the continental crust. Our research indicates a level of complexity in the formation of ophiolite-hosted carbonates including several stages of their formation as well as several sources of carbonating fluids.

Plümper, O., & Matter, J. (2023). Olivine—the alteration rock star. Elements, 19(3), 165-172.

Funding: Research financially supported by NCN PRELUDIUM project 2022/45/N/ST10/00879

 

How to cite: Cieślik, B., Pietranik, A., Kierczak, J., Lacinska, A., and Ettler, V.: Multistage carbonation of the Variscan ophiolite? Insights from geochemical and isotopic diversity of ophiolite-hosted carbonates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11037, https://doi.org/10.5194/egusphere-egu24-11037, 2024.

EGU24-11149 | ECS | Orals | GMPV2.3

Effect of tectonic stress on isotopic systems in dating minerals 

Xin Chen and Yu Wang

Temperature is recognized as the only dominant factor that affects the opening and closing of isotope system, based on which thermochronology has well developed. However, there are some research shows that stress could also matter. The muscovite K-Ar ages of Sanbagawa (Japan) schists are consistently younger with increasing deformation extent (Tetsumaru, 1988), which revealed that tectonic deformation can have influence on isotopic ages. On a microscopic scale, elements like Pb can redistribute in zircon lattice during dislocation (Piazolo,2015). The behaviors of isotopic systems in dating minerals under stress involve the fundamental problem of isotopic chronology. The application of it can be very wide, it allows us to get the deformation age directly if we choose the right deformed minerals in the right way. Some of the works such as fault, fold and ductile shear zone dating by our lab has been published (Yu Wang, 2010, 2016, 2020). What role does stress play in isotope diffusion which in turn affects ages is what we are eager to know. We designed a set of experiments using three axles press to work on undeformed K-feldspars with known age (126Ma) to test the effects. Rock mechanics experiments, field observation and isotopic dating are combined to give us an insight to it.

How to cite: Chen, X. and Wang, Y.: Effect of tectonic stress on isotopic systems in dating minerals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11149, https://doi.org/10.5194/egusphere-egu24-11149, 2024.

EGU24-11865 | Orals | GMPV2.3

Using U-Pb Carbonate Geochronology to constrain the timing of fault development and fluid source evolution in an inverted continental rift basin. 

Joe Connolly, Mark Anderson, Catherine Mottram, Gregory Price, and David Sanderson

The Bristol Channel Basin (BCB) is a small continental rift basin that developed along the eastern margin of the North-Atlantic during the Mesozoic. Relatively minor basin inversion occurred during the Cenozoic. It has been extensively studied due to the exceptional exposure of faults along both margins of the basin. Widespread calcite mineralisation of overprinting fracture networks documents fluid partitioning along these structures over time. However, the temporal evolution of deformation has been constrained solely from the relative timing of structures in the field and through comparisons with other basins in the region. This has made detailed modelling of how structures have evolved during basin development and later inversion problematic. In this study we succesfully use U-Pb carbonate geochronology on low U samples (<1ppm) to constrain the absolute timing of fault development, whilst also assessing fluid source evolution with stable isotope and fluid inclusion data. Absolute dating of calcite slickenfibres in the fault cores of extensional, thrust and strike-slip faults in the East-Quantoxhead - Kilve region reveals the precise timing of different phases of deformation within the BCB for the first time.

New age data show that extensional faulting occurred from ca. 154-118 Ma. Strike-slip faults formed ca. 47-21 Ma, with thrust faults forming ca. 46-35 Ma. The results show Late Jurassic – Early Cretaceous E-W extension with a vertical σ1, followed by Eocene – Miocene N-S contraction with σ1 now being ~horizontal. New age determinations provide much greater insight into the longevity of these structural phases, as well as how fluid nature and composition has evolved over time. Stable isotope data captures fluid source evolution, with δ13C & δ18O values being more negative in the older extensional faults, and becoming more positive over time in the later contractional features. Reactivated structures show evidence for deeper fluid sources, shown by relatively hotter fluid inclusion temperatures within these faults.

Constraining the development of different fault populations within the BCB increases our understanding of the evolution of regional stress within southern England and can be extrapolated to nearby basins. Understanding the historical partitioning of fluid flow through different fault populations has practical applications for understanding where produced and/or injected fluids will flow when a reservoir is exploited today, such as in an Enhanced Geothermal System (EGS).

How to cite: Connolly, J., Anderson, M., Mottram, C., Price, G., and Sanderson, D.: Using U-Pb Carbonate Geochronology to constrain the timing of fault development and fluid source evolution in an inverted continental rift basin., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11865, https://doi.org/10.5194/egusphere-egu24-11865, 2024.

EGU24-11910 | Posters on site | GMPV2.3 | Highlight

The thermal and aqueous evolution of CM carbonaceous chondrite meteorites revealed by triple oxygen and clumped isotope compositions of their carbonates 

Matthieu Clog, Paula Lindgren, Martin R Lee, and Sevasti Modestou

Carbonates (calcite, aragonite, dolomite) are a minor component (often below 4 vol. %) of CM carbonaceous chondrites and formed during the aqueous alteration of their asteroidal parent bodies in the first few million years of Solar System history. The chemical and isotopic composition of these minerals are a valuable source of information on the conditions of alteration, potentially providing information on the composition and temperature of asteroidal fluids.

We report the carbon triple oxygen and carbonate clumped isotope compositions of six CM chondrites (Allan Hills 83100, Cold Bokkeveld, LaPaz Icefield 031166, Lonewolf Nunataks 94101, Murchison, Scott Glacier 06043), which span a range of degrees of aqueous alteration. To avoid issues due to the brecciated nature of these meteorites, gas aliquots produced by a single acid digestion were used to measure both the clumped isotopes and the triple oxygen isotope compositions. Where both calcite and dolomite are present, stepped acid dissolution allows us to measure their isotopic compositions separately.

We found that the Δ17O values range from -1 to -2.6‰, with a 0.6‰ difference between coexisting calcite and dolomite that indicates precipitation from distinct fluids. Crystallization temperatures range from 5 to 50⁰C for calcite and 75 to 100⁰C for dolomite. CM chondrites often contain several generations of carbonates with ranges in isotopic compositions that can be determined by ion probe. Because our method relies on the bulk extraction of carbonate phases, the measured values are the modes of the distributions for each meteorite, which has to be considered carefully in their interpretation. The isotopic composition of the alteration fluids can also be calculated for each meteorite and carbonate phase. We find that their δ18OvsSMOW ranges from -6.6 to +2.3‰, with no clear relationship with temperature or the δ13C of the carbonates, indicating a variety of starting isotopic compositions for the alteration fluids.

The main pattern that emerges is that chondrites with a higher degree of alteration (based on their petrology) have carbonates with lower Δ17O and higher crystallization temperatures, which is consistent with a prograde reaction in a largely closed system, and with dolomite forming after calcite in our samples.

How to cite: Clog, M., Lindgren, P., Lee, M. R., and Modestou, S.: The thermal and aqueous evolution of CM carbonaceous chondrite meteorites revealed by triple oxygen and clumped isotope compositions of their carbonates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11910, https://doi.org/10.5194/egusphere-egu24-11910, 2024.

EGU24-13041 | Posters on site | GMPV2.3

Age and origin of quartz xenocrysts in a basaltic lava flow in Martinique  

Christoph Schmidt, Aurélie Germa, Xavier Quidelleur, Georgina King, and Rocío Jaimes Gutiérrez

In south-western Martinique (Lesser Antilles), the Pointe Burgos Basaltic monogenetic strombolian cone and lava flow cut through a porphyritic dacitic lava dome (Morne Champagne) dated at 617 ± 52 ka (Germa et al., 2011). An exceptional feature of the basaltic lava flow is the occurrence of about 4% of large (up to 2 cm) quartz crystals. Previous studies suggested that quartz xenocrysts had been added to the basaltic magma upon mechanical magma mixing with the cooled shallow dacitic reservoir, with a 9:1 ratio. Indeed, plagioclase phenocrysts (>1 cm) present resorbed surface and reaction rims, a well-known evidence of crystal remobilization. However, no other textural evidence of magma mixing is visible in the basaltic edifice. Moreover, the quartz crystals present unusual habits, are heavily cracked, and appear as filling voids in the basalt. This led us to investigate the age of the basaltic eruption and of the quartz crystals to propose a scenario for the xenocrysts’ origin.

The groundmass of the basaltic lava flow was K-Ar dated at 379 ± 25 ka, therefore ~240 ka after the eruption of the dacitic dome that it cuts through. Such a long time difference suggests that magma in the shallow reservoir was completely solidified when the basaltic magma ascended through it. Therefore, we would have expected to see also enclaves of dacite included in the basalt. Thermoluminescence (TL) dating allows for estimating the time since mineral formation or the last heating of a mineral above ~350 °C, thus representing an ideal tool to test whether the quartz xenocrysts formed synchronously with lava flow, or if they were formed later as substitutional minerals or void fillings. Here, we used red TL in combination with several protocols for dose determination, yielding consistent results. For assessing the dose rate, we took into account the quartz xenocrysts’ size distribution, the radioelement concentration of the basaltic matrix and the sites’ erosive evolution. The latter is particularly important because the basaltic matrix is comparatively poor in radioactivity so that the share of the cosmic dose rate becomes important. We obtain preliminary TL ages of 345 ka (with a total erosion of 20 m) and 377 ka (with an erosion of 50 m), each with a ~7% uncertainty. This result emphasizes the importance of reconstructing the lava flow geometry for answering the research question. As we believe that scenario (1) is more plausible, our results indicate the xenocrysts were likely formed post-eruption, challenging the initially suggested model of magma mixing and favouring secondary precipitation or mineral substitution. In case of TL resetting through geothermal activity, the age would represent the cooling following its cessation. However, given the xenocrysts’ pseudomorphic habit, it appears more likely that they represent secondary precipitates from hydrothermal fluids in voids left by strong geothermal alteration of the basaltic host rock.    

 

References

Germa, A., Quidelleur, X., Lahitte, P., Labanieh, S., Chauvel, C., 2011. The K–Ar Cassignol–Gillot technique applied to western Martinique lavas: a record of Lesser Antilles arc activity from 2 Ma to Mount Pelée volcanism. Quat. Geochronol. 6, 341-355.

 

How to cite: Schmidt, C., Germa, A., Quidelleur, X., King, G., and Jaimes Gutiérrez, R.: Age and origin of quartz xenocrysts in a basaltic lava flow in Martinique , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13041, https://doi.org/10.5194/egusphere-egu24-13041, 2024.

EGU24-13231 | ECS | Orals | GMPV2.3

Garnet, zircon and rutile U-Pb systematics of eclogite xenoliths from the Navajo Volcanic Field (USA) 

Johannes E. Pohlner, Siqi Hao, Richard Albert, Axel Gerdes, Daniel J. Schulze, Herwart Helmstaedt, and Sonja Aulbach

Intrusions of the Navajo Volcanic Field (NVF) contain eclogite xenoliths that record processes related to the subduction of the Farallon plate beneath the Colorado Plateau. Previous geochronological work sparked controversies about their origin, especially whether they are derived from oceanic crust of the Farallon plate, or from older continental lithosphere, based on occasional Proterozoic zircon U-Pb ages. Moreover, the mechanisms and timescales of the recorded high-pressure processes, including several stages of fluid metasomatism, are largely unknown. We study the U-Pb systematics of garnet, zircon and rutile by LA-ICP-MS in order to achieve a refined petrochronologic interpretation of the NVF eclogites.

The eclogite xenoliths are hosted by serpentinized ultramafic microbreccia (SUM) which intruded the Colorado Plateau at ~30 Ma as a consequence of extensive hydration of the lithospheric mantle by Farallon slab-derived fluids. In contrast to kimberlite-borne eclogite xenoliths, which often contain garnet and omphacite only, those of the NVF additionally contain ubiquitous rutile, and often pyrite, phengite, zoisite pseudomorphs after lawsonite (with rare lawsonite relics), accessory monazite, and rare coesite. Based on this assemblage, peak P-T conditions around 4 GPa and 600°C are estimated. Subsequent rapid uplift in the sub-solidus SUM is not thought to have caused significant further heating. Except for a few instances where a mid-ocean ridge basalt-like bulk chemical composition is essentially preserved, the xenoliths are strongly overprinted by several metasomatic events in the eclogite facies. Most notably, this involved interaction with a Na-Si-S-rich fluid, probably of crustal origin, and a later (just prior to exhumation) serpentinite-derived fluid.

All our U-Pb rutile data as well as published U-Pb monazite data (~29 Ma) agree with the ~30 Ma SUM formation age. The majority of the U-Pb zircon analyses predate the rutile data by not more than several Myr, with a minority of older ages forming a continuum to the late Cretaceous. Unlike some earlier studies, we did not obtain any Proterozoic U-Pb zircon ages. The garnet U-Pb dates, which are mostly from pre-metasomatic zones, partly agree with the zircon dates within uncertainty, but sometimes predate the zircon dates from the same sample by up to several tens of Myr.

Despite moderate peak metamorphic temperatures (~600°C), rutile remained an open system for Pb until exhumation. Garnet and zircon are resistant to Pb volume diffusion at these temperatures, however, the zircon ages appear to be largely reset during fluid metasomatism, as also indicated by often high common Pb contents. Due to the absence of preserved igneous zircon ages, the protolith origin remains uncertain. Garnet, which grew mostly before metasomatism, seems to provide robust ages of initial eclogitization, which may have been diachronous in our sample suite. Geochronological evidence implies that several tens of Myr passed between initial eclogitization and exhumation of the xenoliths.

How to cite: Pohlner, J. E., Hao, S., Albert, R., Gerdes, A., Schulze, D. J., Helmstaedt, H., and Aulbach, S.: Garnet, zircon and rutile U-Pb systematics of eclogite xenoliths from the Navajo Volcanic Field (USA), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13231, https://doi.org/10.5194/egusphere-egu24-13231, 2024.

EGU24-14298 | ECS | Orals | GMPV2.3

Direct dating of global Cryogenian sections by in situ U–Pb mapping of carbonates 

Darwinaji Subarkah, Alan Collins, Stefan Löhr, Angus Nixon, Morgan Blades, Juraj Farkas, Jarred Lloyd, Robert Klaebe, Sarah Gilbert, and Georgina Virgo

The Cryogenian period represents a critical interval in Earth’s history, characterized by drastic tectonic and environmental changes. Evidence of low-altitude glacial deposits from this time has been recognized globally, alluding to the most extensive icehouse regimes known on our planet. These conditions of successive global freezing and warming during the Neoproterozoic have been dubbed as ‘Snowball Earth’ events. Importantly, the Cryogenian may have played a key role in the accelerated evolution of early life, as microorganisms became more complex and abundant after this period. Consequently, it is important to constrain the absolute timing, duration, and termination of these glacial and interglacial events. Despite their significance, robust, direct dating of Cryogenian sections remains challenging. The most accurate way to constrain these units is through dating of interbedded volcanics. However, they are not present across all sections globally, making correlations difficult to establish.

As such, we present a novel strategy to address this issue by directly dating a broad array of Cryogenian carbonates through an in situ U-Pb mapping approach. Our case study includes inter-glacial and post-glacial carbonates from sections in Australia, Oman, and Greenland. We show that this method allows for the concurrent collection of geochemical, petrographic, and geochronological information at sufficient precision to address key geological questions. Geochemical proxies such as elevated Mn/Sr ratios and Al or Si can be used to filter areas affected by alteration or detrital input, respectively. Secondary phases such as veins and overgrowths can also be petrographically avoided as an advantage of the spatially coherent mapping technique. Regions that yield enrichment in U and best spread in U–Pb ratios can be preferentially selected. Triaging such datasets and spatial information can help identify subdomains within a sample that is most suitable for dating, maximizing the success rate of this approach. The technique is capable of yielding age precision of ±1% depending on the concentration of U, the range in radiogenic isotopes, and the number of pixels that make up an analytical point.  

How to cite: Subarkah, D., Collins, A., Löhr, S., Nixon, A., Blades, M., Farkas, J., Lloyd, J., Klaebe, R., Gilbert, S., and Virgo, G.: Direct dating of global Cryogenian sections by in situ U–Pb mapping of carbonates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14298, https://doi.org/10.5194/egusphere-egu24-14298, 2024.

EGU24-14613 | ECS | Orals | GMPV2.3

Unusual heavy rare earth elements enrichment and mineralization age in the Jialu deposit from the Qinling Orogen, central China 

Fengchun Li, Qingdong Zeng, Hongrui Fan, and Kuifeng Yang

Carbonatite has enormous potential for rare earth element resources, typically enriched in light rare earth elements, and has attracted increasing attention from geologists and economists. However, there are a small number of documented instances of carbonatite-related heavy rare earth elements enrichment. The Jialu carbonatites in the Qinling orogenic belt (central China) are characterized by the enrichment of heavy rare earth elements compared with typical global carbonatites. The carbonatites are dominantly comprised of calcite, quartz, sulfate, K-feldspar, minor sulfides, and rare earth minerals such as monazite, bastnäsite, parisite, and xenotime, with two mineralization stages including the early quartz-K-feldspar-calcite stage (Stage I) and the late sulfide-rare earth mineral-calcite stage (Stage II). The rare earth element contents of Stage I calcite are higher than those of the Stage II, especially heavy rare earth elements. Calcite from the different mineralization stages exhibits variable chondrite-normalized REE patterns, with the heavy rare earth elements and rare earth element abundances (134–1023 ppm) decreasing from the early to the late stage owing to the crystallization of xenotime. The δ13C (−5.39‰ to −6.68‰) and slightly higher δ18O (10.77‰ to 12.60‰) values for calcite from the Jialu carbonatites generally deviate from the values observed in the primary carbonatite field, which may be a result of Rayleigh-type fractionation. LA–ICP–MS U–Pb dating shows the lower-intercept ages of 243.8 ± 5 and 237.6 ± 1.3 Ma for the monazite and xenotime, respectively, with the weighted average 206Pb/238U ages of 240.9 ± 6 and 239.2 ± 1.3 Ma. These results indicate that the Jialu deposit was concurrent with Triassic carbonatite magmatism and rare earth element mineralization observed on the southern margin of the North China Craton. This implies that this region may have great rare earth element mineralization potential.

How to cite: Li, F., Zeng, Q., Fan, H., and Yang, K.: Unusual heavy rare earth elements enrichment and mineralization age in the Jialu deposit from the Qinling Orogen, central China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14613, https://doi.org/10.5194/egusphere-egu24-14613, 2024.

EGU24-14745 | ECS | Posters on site | GMPV2.3

Provenance of the North Eastern Carpathian thrust sheet deposits based on geochronology 

Constantin Lazar, Relu Dumitru Roban, and Mihai Ducea

In the northernmost part of the Romanian Carpathians, the Maramureș region exposes several tectonic units comprising remnants of the Mesozoic Ceahlău - Severin Ocean. The “Black Flysch” unit contains a mafic complex extended in the Middle – Late Jurassic interval. These are covered by Upper Jurassic–Lower Cretaceous sediments, which include deep-water carbonates and siliciclastic deposits in the “Black Flysch” Nappe and mainly turbidites in the Ceahlău unit, which belong to the Outer Dacide nappe system.

The U-Pb age distribution spectra of detrital zircons obtained from the samples collected from the “Black Flysch” and Ceahlău tectonic units exhibit similarities within the range of 180–3,000 Ma. Significant peaks have been noticed at around ~460, 580–620, ~320, 180–200, and 950–1,100 Ma. Within the ‘Black Flysch’ Nappe prevail Ordovician ages (~460 Ma) associated with the Bucovinian Nappe basement. Conversely, in the Ceahlău Nappe, the Late Neoproterozoic peak (~600 Ma) holds greater significance, corresponding to the sediments of the Eastern European Platform and the paragneiss of the Bucovinian Nappe. The East European Craton contributes insignificantly as source area, given the minimal percentage of inherited ages surpassing 1 Ga.

How to cite: Lazar, C., Roban, R. D., and Ducea, M.: Provenance of the North Eastern Carpathian thrust sheet deposits based on geochronology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14745, https://doi.org/10.5194/egusphere-egu24-14745, 2024.

Chemical composition heterogeneity in carbonate rocks ranging from the microscale to several meters preclude their direct age determination. Therefore, stepwise dissolution of several bulk rock samples or subsamples of an individual specimen can provide information on the primary composition of the carbonate material and refine the resulting Pb–Pb age. A millimetre-thick carbonate-rich (white) and shale-rich (black) layer from the Rohtas Formation, Lower Vindhyan Group, was divided into eight subsamples each and subjected to three leaching steps. The first leachate (L1) was discarded, and subsequent leachates, L2 and L3, were obtained after 24 hours of leaching in 0.6M HBr. A Pb-Pb isochron age of 1666±25 Ma (n=23, MSWD=13) is obtained by regressing L2 and L3 leachates from both layers. Since initial leachates (e.g., L2) contain epigenetically altered carbonate material, data points in the 207Pb/204Pb vs 206Pb/204Pb plot are well correlated but show a large scatter. In contrast, regressing only the L3 leachates of both layers yielded a Pb-Pb isochron age of 1644±49 Ma (n=12, MSWD=7), with a reduced scatter and comparable with earlier published work. Increasing the number of leaching steps minimizes the degree of scatter and significantly improves the precision of the obtained Pb-Pb age. Two subsamples from phosphoritic stromatolite-bearing carbonate rocks of the Tirohan Dolomite from the Jankikund river section, Lower Vindhyan Group, were subjected to seven leaching steps, of one hour each, in 0.5M HBr. The Pb isotopic composition of the carbonate material dissolved in five steps (L3 to L7) was regressed to yield an isochron age of 1579±16 Ma (n=10, MSWD=1.3). The Pb-Pb age of the Tirohan Dolomite Member obtained by multi-step leaching in this study is indistinguishable within error from an earlier reported age [1] of 1650±89 Ma (n=5, MSWD=89), moreover shows a better correlation of the 207Pb/204Pb vs 206Pb/204Pb data. All the analyses were performed in static mode on a Thermo-Fisher Neptune Plus MC-ICPMS. The instrumental mass fractionation was corrected using both thallium-spiking and sample-standard bracketing. Furthermore, a generalized power law correction was applied to the 204Pb-corrected ratios of unknown samples using the 205Tl/203Tl ratios of the bracketing NBS-981 standards. The two-stage mass bias corrected ratios were then normalized by the ratios of NBS-981 during each analytical session. The long-term isotopic ratios of NBS-981 standard (n=71) are 206Pb/204Pb= 16.9371±0.0026 (2σ), 207Pb/204Pb= 15.4906±0.0046 (2σ), 208Pb/204Pb= 36.7042±0.0113 (2σ).

 

[1] Bengtson, S., Belivanova, V., Rasmussen, B., Whitehouse, M. (2009). The controversial “Cambrian” fossils of the Vindhyan are real but more than a billion years older. Proceedings of the National Academy of Sciences, 106(19), 7729-7734.

How to cite: Nandi, A., Vadlamani, R., and Bera, M. K.: Improving the precision of Pb-Pb ages of carbonate rocks by implementing stepwise dissolution techniques: A case study from the Lower Vindhyan Group, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14937, https://doi.org/10.5194/egusphere-egu24-14937, 2024.

EGU24-14940 | ECS | Orals | GMPV2.3

Nano to milli scale characteristics of wolframite ([Fe,Mn]WO4)  and their implications for U-Pb geochronology of tungsten-bearing mineral deposits 

Patrick Carr, Rolf Romer, David Chew, Richard Wirth, and Julien Mercadier

Geochronological data on ore-bearing minerals can constrain the absolute ages and duration mineralising processes. Of the tungsten-bearing minerals, wolframite is the most promising geochronometer for these mineral systems, but high precision ages are hampered by common Pb and intra-grain heterogeneity. We present ID-TIMS and LA-ICP-MS U-Pb isotope data of wolframite , combined with milli scale (SEM-EDS) and microscale (LA-ICP-MS) element maps and nanoscale (FIB-TEM) chemical and structural images to elucidate the complex geochemical behaviour of this mineral and the implications for U-Pb geochronology.

During this study, three new U-Pb reference materials have been developed with ages of ca 158 Ma, 289 Ma and 325 Ma; these are available to interested laboratories. The best precision obtained by ID-TIMS was 1.24%, whilst we estimate the best possible precision for LA-ICP-MS ages to be ca 1.8%. Apart for analytical uncertainties, the main contributor to age uncertainty is the poor dispersion in U-Pb data (for Discordia fitting) and unknown common Pb composition for ID-TIMS data, and micron-scale heterogeneity for LA-ICP-MS data.

Microscale (LA-ICP-MS maps) to nanoscale (FIB-TEM) imaging techniques show large chemical and structural heterogeneity of wolframite related to the complex geological environments in which it is precipitated and altered. Trace element mapping highlights oscillatory and sector zoning not typically observed when using traditional SEM-based techniques. The variable distribution of the analysed elements (Fe, Mn, Sc, Nb, Ta, Y, Pb, Th and U for this study) can be explained both by coupled substitution and changing fluid chemistry recorded within a single wolframite crystal. The nano-scale structure of a strongly altered wolframite is characterised by rare ca 10x10 nm non-symmetric zones of amorphous crystal structure, and bands of elongate (ca 100 x 20 nm oval-shaped) low density zones that we consider representing porosity developed during rapid crystallisation of wolframite.

Although no real intra-grain age dispersion is observed in the analysed samples, the precision of U-Pb ages is strongly affected by the local chemical and structural characteristics of the wolframite. Most notably, the concentration of 238U and 238U/204Pb can vary by an order of magnitude within a zone smaller than a typically laser ablation spot (e.g., 100 µm).

 

How to cite: Carr, P., Romer, R., Chew, D., Wirth, R., and Mercadier, J.: Nano to milli scale characteristics of wolframite ([Fe,Mn]WO4)  and their implications for U-Pb geochronology of tungsten-bearing mineral deposits, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14940, https://doi.org/10.5194/egusphere-egu24-14940, 2024.

EGU24-15171 | ECS | Orals | GMPV2.3 | Highlight

Examining the behaviour of Sr and 40Ar in white mica in response to deformation and fluid-mediated chemical exchange 

Christopher Barnes, Thomas Zack, Axel Gerdes, Renelle Dubosq, Alfredo Camacho, Delia Rösel, and Michał Bukała

A schist and a marble are used to investigate 40Ar and Sr behaviour in white mica that show distinct records of deformation and fluid-mediated chemical exchange. The rocks were obtained from the upper level of the Middle Allochthon in the northern Scandinavian Caledonides. They underwent eclogite-facies metamorphism (2.4-2.6 GPa/590-660°C) at c. 486-481 Ma and were deformed during juxtaposition with the overlying Upper Allochthon in lower amphibolite/greenschist facies conditions at c. 430-420 Ma. Deformation of the schist is recorded by anastomosing shear bands that delimit polymineralic lenses of white mica, quartz, garnet, and apatite. White mica are only locally deformed along shear bands but show irregular zoning indicative of dissolution-reprecipitation, with high-celadonite zones (XCel: 0.22) generally enveloped by low-celadonite zones (XCel: 0.09). Fluid activity during rock deformation is evinced by the presence of chlorite in shear bands and surrounding partially retrogressed garnet, as well as dissolution-reprecipitation of plagioclase. Mobilization of trace elements is evident, with low-celadonite zones enriched in V, Sr, Nb, Ba and depleted in Li, Ti, Co, Zn relative to high-celadonite zones. The former also shows slight enrichment of average B (35.9 µg/g) compared to the latter (27.2 µg/g), but δ11B values are the same for both zones (-13.5 and -13.6 ‰), suggesting locally-derived fluids. Deformation and foliation development of the marble is characterized by shape preferred orientation of calcite and white mica. The mica show variable grain size and are all deformed, highlighted by electron channeling contrast imaging that reveals abundant µm-scale kink bands within individual grains, a feature that is significantly less apparent in the schist mica. The marble mica show uniform high-celadonite content (XCel: 0.28), representing preservation of high-pressure mica chemistry during deformation. They show no trace element variations, except for a decrease B content with δ11B values (36.3 µg/g and -18.1 ‰ to 15.5 µg/g and -22.0 ‰), which may be explained by heterogeneous devolatilization and preferential loss of 11B during high-grade metamorphism. Thus, it is evident the mica remained closed to chemical exchange during deformation. The white mica 40Ar/39Ar dates from the schist are dispersed (491 ± 4 Ma to 427 ± 4 Ma), with the older dates typically provided by high-celadonite zones, and vice versa. The marble mica yielded a similar range of dates (486 ± 4 Ma to 428 ± 4 Ma), with finer-grains yielding younger dates. Weighted averages of single-spot Rb/Sr dates show a similar pattern for the schist (high-celadonite: 485 ± 8 Ma; low-celadonite: 427 ± 15 Ma). However, Rb/Sr dates from the marble mica only reproduce the older population of dates (481 ± 4 Ma) regardless of grain size. These results demonstrate that loss of 40Ar from white mica can be facilitated by either fluid-mediated chemical exchange or deformation, but re-equilibration of Sr isotopes to reset Rb/Sr dates requires fluid-driven processes in lower amphibolite/upper greenschist facies conditions.

Research funded by NCN grant no. UMO-2021/40/C/ST10/00264 (C.J. Barnes), supported by “Juan de la Cierva” Fellowship JFJC2021-047505-I by MCIN/AEI/10.13039/501100011033 and CSIC (M. Bukała)

How to cite: Barnes, C., Zack, T., Gerdes, A., Dubosq, R., Camacho, A., Rösel, D., and Bukała, M.: Examining the behaviour of Sr and 40Ar in white mica in response to deformation and fluid-mediated chemical exchange, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15171, https://doi.org/10.5194/egusphere-egu24-15171, 2024.

EGU24-15293 | ECS | Orals | GMPV2.3

Carbonate U-Pb geochronology as a tool to unravel complex fault evolution: an example from the central Southern Alps (Italy) 

Martina Rocca, Stefano Zanchetta, Xavier Mangenot, Marta Gasparrini, Fabrizio Berra, Pierre Deschamps, Abel Guihou, and Andrea Zanchi

Faults and related fractures have been studied for decades due to their potential in providing insights into past and present crustal deformation processes, climate evolution, seismology, and hydrology among others. Carbonates are very common syn-tectonic minerals that occur along fault planes or in fault-related fractures forming slickenfibres and veins (Roberts and Holdsworth, 2022). The ability of carbonates to incorporate uranium during their precipitation allows the application of in-situ carbonate U-Pb radioisotopic dating via LA-ICP-MS (Roberts et al., 2020). The integration of this method with the more conventional petrography and biostratigraphy holds strong potential in resolving the timing of brittle structure development. A robust pre-dating screening protocol using a multi-disciplinary approach, including structural, microstructural, petrographic, and isotopic characterization has been implemented to link carbonate precipitation event to fault kinematics.

This approach has been applied to the central Southern Alps (Northern Italy), where Early Jurassic rift-related faults are preserved despite their later involvement in the Alpine orogeny. Fieldwork and sampling focused on the Amora Fault (Bergamo, Italy), a rift-related N-S normal fault of the Jurassic Lombardian basin. Structural and paleostress analysis led to the identification of several mesoscopic N-S trending normal faults and veins both in the hanging wall and footwall of the Amora Fault, indicating an E-W extension. The fault is cross-cut by middle Eocene E-W trending magmatic bodies, which, in turn, are cross-cut by Alpine thrust faults. The Amora Fault and related minor faults also show strike-slip reactivation related to N-S Alpine compression.  

Sampling focused on the Norian to Lower Jurassic succession in the hangingwall and footwall of the main fault plane, where carbonate syn-tectonic veins and slickenfibres are present. Structural analysis allowed relating the structures to either the rifting or the Alpine reactivation.

Microstructural and petrographic analyses assisted by cathodoluminescence on 21 samples revealed the occurrence of several carbonate phases. Elemental analyses (Ca, Mg, Fe, Sr) and O-C stable isotope analyses confirmed the circulation of different fluids. U-Pb dating on the carbonate phases provided four age clusters, each connected to a tectonic phase: (1) Early to Middle Jurassic carbonates precipitated in rift-related structures from a fluid with a δ13C buffered by the host-rock. (2) Early Cretaceous carbonates possibly related to the late stage of rifting activity. (3) Late Cretaceous carbonates precipitated from a meteoric fluid during the early stages of the Alpine orogeny. (4) Oligo-Miocene carbonates connected to the strike-slip reactivation of rift-related normal faults.

The integration of field-based and stratigraphic observations with carbonate geochemistry and geochronology allowed the recognition of a complex reactivation history for the Amora Fault.

References

Roberts, N.M.W., Drost, K., Horstwood, M.S., Condon, D.J., Chew, D., Drake, H., Milodowski, A.E., McLean, N.M., Smye, A.J., Walker, R.J., and Haslam, R., 2020. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb carbonate geochronology: strategies, progress, and limitations. Geochronology 2, 33–61.

Roberts, N.M.W, and Holdsworth, R.E., 2022. Timescales of faulting through calcite geochronology: A review. Journal of Structural Geology, 158, 104578.

How to cite: Rocca, M., Zanchetta, S., Mangenot, X., Gasparrini, M., Berra, F., Deschamps, P., Guihou, A., and Zanchi, A.: Carbonate U-Pb geochronology as a tool to unravel complex fault evolution: an example from the central Southern Alps (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15293, https://doi.org/10.5194/egusphere-egu24-15293, 2024.

EGU24-15680 | Posters on site | GMPV2.3

High precision isotope ratio analysis for Cosmochemistry applications using the Thermo Scientific Neoma MC-ICP-MS. 

Grant Craig, Markus Pfeifer, Neil Williams, Lionnel Mournier, Claudia Bouman, and Nicholas Lloyd

               Within the first five years of the initial introduction of multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) with the VG Elemental Plasma 54 the potential for the technique to be applied to Isotope Cosmochemistry applications had already been recognized1. Early work focused on the 182Hf-182W chronometer, which had up until the introduction of MC-ICP-MS, been extremely difficult to measure with existing thermal ionization mass spectrometry (TIMS) techniques due to the extremely high first ionization potential of W.

In the following 25 years the use of MC-ICP-MS for Isotope Cosmochemistry applications has expanded to numerous other isotopic systems, including, but not limited to 26Al-26Mg, 146Sm-142Nd and 60Fe-60Ni, not just 182Hf-182W.  A general feature of these measurements is typically a reliance on excellent precision, on the order of a few ppm, 2RSD [2]. The high count rates required to achieve such excellent precision take time in order to achieve. Excellent precision over such time scales require a high performance mass spectrometer, capable of high sensitivity, stable throughout the course of the measurement and equipped with a low-noise detection array.

For over 20 years Thermo Fisher Scientific has pioneered developments in multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). The latest generation Thermo Scientific™ Neoma™ MC-ICP-MS, blends cutting-edge and field proven technology from the Ultra™ HR-IRMS and iCAP Qnova™ Series ICP-MS [3] and has the capability to complement and enhance Isotope Cosmochemistry applications [4]. Here we report our investigations into using the Neoma MC-ICP-MS and Neoma MS/MS MC-ICP-MS for a selection of Isotope Cosmochemistry application, including high precision Mg, Fe, Cu, Zn and W measurements.

[1] A. Halliday, D. Lee, J. Christensen, M. Rehkämper, W. Yi, X. Luo, C. Hall, C. Ballentine, T. Pettke, C. Stirling, Geochimica et Cosmochimica Acta, 1998, 62, 919-940.

[2] S. Goderis, R. Chakrabarti, V. Debaille, J. Kodolányi, 2016, J. Anal. At. Spectrom., 2016, 31, 841-862.

[3] Thermo Fisher Scientific, 2020, BR30600-EN 0520C: Neoma Multicollector ICP-MS [pdf], Thermo Fisher Scientific.

[4] Z. Deng, M. Schiller, M. G. Jackson, M-A. Millet, L. Pan, K. Nikoljsen, N. S. Saji, D. Huang, M. Bizzarro, Nature, 2023, 621, 100-104

How to cite: Craig, G., Pfeifer, M., Williams, N., Mournier, L., Bouman, C., and Lloyd, N.: High precision isotope ratio analysis for Cosmochemistry applications using the Thermo Scientific Neoma MC-ICP-MS., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15680, https://doi.org/10.5194/egusphere-egu24-15680, 2024.

EGU24-15969 | ECS | Orals | GMPV2.3

Controls on high precision zircon U-Pb age spectra in magmatic systems 

Chetan Nathwani, Lorenzo Tavazzani, Dawid Szymanowski, Adrianna Virmond, Sava Markovic, and Cyril Chelle-Michou

U–Pb and U–Th geochronology of zircon in igneous rocks provides key information about the age, longevity, and assembly rates of magma reservoirs. Historically, the available analytical resolution limited these insights to an averaged “age” of a magmatic system. With dramatic improvements in analytical techniques over the last two decades, it has become possible to resolve extended records of zircon crystallisation within a single igneous sample, which can extend prior to its eruption or subsurface solidification by as much as a million years. In some magmatic systems these age spectra mirror those produced in zircon solubility models, reflecting monotonous cooling of a magma reservoir, whilst in others they may take other shapes indicative of a more complex interplay of processes [1,2]. Isolating the effect of these processes can be challenging since many analytical and geological factors also play a role. Such geological processes may include magma recharge or truncation of zircon crystallization by melt extraction.

In this study, we compiled high-precision zircon U-Pb dates from volcanic, plutonic and porphyry copper systems. We use the Wasserstein metric as a dissimilarity measure to compare distributions between all compiled age spectra. Dimensionality reduction of the resulting dissimilarity matrix reveals that plutonic systems have contrasting age spectra to volcanic and porphyry copper systems. Plutonic systems typically exhibit age spectra skewed towards older ages whereas volcanic and porphyry systems are skewed towards younger ages.

We adopt a bootstrap modelling approach to explain these differences, which allows the modelling of the effects of the number of sampled zircons, analytical uncertainties, magmatic recharge, mixed age domains and a truncation of crystallisation. The effects of multiple magmatic recharge events combined with truncation by volcanic eruption/dyke formation appear to be the most likely explanation for the young skew of volcanic and porphyry copper age spectra. Truncation of zircon crystallization alone appears to be incapable of explaining the full difference. Recognising the contrasting zircon age spectra between volcanic and plutonic systems is critical to improve eruption age estimation and interpretations of zircon compositions in petrological studies.

[1] Keller, C.B., et al., GPL, 2018. 31–35.

[2] Tavazzani, L., et al., EPSL, 2023. 623, 118432.

How to cite: Nathwani, C., Tavazzani, L., Szymanowski, D., Virmond, A., Markovic, S., and Chelle-Michou, C.: Controls on high precision zircon U-Pb age spectra in magmatic systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15969, https://doi.org/10.5194/egusphere-egu24-15969, 2024.

Geochronological methods play a pivotal role in unraveling the evolution of volcanic fields, providing insights into eruption timescales and recurrence. In the Quaternary Eifel volcanic field, with >300 maars and scoria cones, dating volcanic events remains challenging due to the scarcity of suitable materials for conventional dating methods. A promising approach to determine accurate eruption ages is to apply (U-Th)/He geochronology to zircon extracted from partially re-melted crustal xenoliths1,2, which in case of Eifel maars are co-deposited with country-rock derived lithics and juvenile lapilli. However, the reproducibility of the method, if applied to xenoliths of different origin, age, composition, and texture, has not been studied for a single explosive eruption.

We collected >250 crustal xenoliths from >35 centers of the East and West Eifel volcanic fields. Coupled petrological investigation and zircon geochronology (U-Pb and U-Th) of a subset of these xenoliths reveal their diversity regarding protolith types (plutonic vs. low- to high-grade metamorphic), zircon crystallization ages (200 ka to 3 Ga) and degree of pyrometamorphic overprint (variable abundances of glass and vesicles, and crystal breakdown reaction textures). (U-Th)/He dating of the previously U-Th-Pb dated crystals (zircon-double-dating, ZDD) was performed to determine eruption ages for these centers.

Here, we focus on a xenolith suite (n = 8) from the Gemündener Maar and E-Schalkenmehrener Maar, two vents within a maar cluster known as Dauner Maar group. Tentative eruption ages of 20 to 30 ka were estimated from considerations on paleoclimate and crater morphology3,4, and ESR xenolithic quartz dates of 30 ± 4 ka5. The pyroclastic deposits are rich in diverse zircon-bearing crustal xenoliths and thus, offer an ideal testbed to investigate how critical parameters such as xenolith rock type, zircon crystallization age, grain morphology, structure and chemical composition determined by Raman analysis and cathodoluminescence imaging, among others, could influence the measured (U-Th)/He ages. The investigated xenoliths comprise both magmatic and metamorphic protoliths with varying degree of pyrometamorphic overprint. Zircon U-Pb ages range from 115 ± 4 Ma to 2731 ± 66 Ma. Preliminary (U-Th)/He dates of individual xenoliths agree with the expected eruption age range, underscoring the feasibility of the method. A detailed analysis of parameters potentially affecting (U-Th)/He systematics in zircon ages is ongoing.

 

[1] Blondes, M.S., Reiners, P.W., Edwards, B.R., Biscontini, A., 2007, Dating young basalt eruptions by (U-Th)/He on xenolithic zircons: Geology, 35, 17–20.
[2] Ulusoy, İ., Sarıkaya, M.A., Schmitt, A.K., Şen, E., Danišík, M., Gümüş, E., 2019, Volcanic eruption eye-witnessed and recorded by prehistoric humans: Quat Sci Rev, 212, 187–198.
[3] Büchel, G., 1993, Maars of the Westeifel, Germany: Paleolimnology of European Maar Lakes, 49, 1–13.
[4] Lange, T., Cieslack, M., Lorenz, V., Büchel, G., 2022, Chronological sequence of volcanic eruptions in the SE part of the Westeifel Volcanic Field during the Weichselian Glaciation: Jber Mitt Oberrhein Geol Ver, 104, 313– 365.
[5] Woda, C., Mangini, A., A. Wagner, G., 2001, ESR dating of xenolithic quartz in volcanic rocks: Quat Sci Rev, 20, 993–998.

How to cite: Sturm, A., Schmitt, A. K., Danišík, M., and Dunkl, I.: Assessing the reproducibility of (U-Th)/He geochronology of xenolithic zircon: Insights from the Quaternary Eifel intraplate volcanic field, Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16158, https://doi.org/10.5194/egusphere-egu24-16158, 2024.

EGU24-16536 | ECS | Posters on site | GMPV2.3 | Highlight

Two new cassiterite reference materials for in-situ U-Pb dating from the European Variscan metallogenic belt 

Lorenzo Tavazzani, Dawid Szymanowski, Patrick Carr, Marcel Guillong, Yannick Buret, Edgar A. Cortes-Calderon, Julien Mercadier, and Cyril Chelle-Michou

Cassiterite (SnO2) is one of the dominant ore phases in tin-tungsten bearing magmatic-hydrothermal deposits. It can contain high uranium contents and usually hosts low levels of common Pb, making it one of the best U-Pb geochronometers among ore minerals [1]. The widespread use of in-situ techniques to obtain crystallization ages for cassiterite, however, is limited by a paucity of accurately characterized reference materials (RMs). Such shortage is mostly caused by the difficulty of achieving closed-system acid decomposition of this mineral, which represents the foundation of isotope dilution techniques, necessary for accurate and precise determination of U-Pb isotopic composition using thermal ionization mass spectrometry (TIMS) techniques.

In this contribution, we present a new set of U-Pb isotopic compositions of two cassiterite samples from the archetypal Variscan Sn-W greisen deposits of Panasqueira (Portugal) and Krasno (Czechia) obtained with an updated protocol of complete HBr decomposition of cassiterite in the presence of a U-Pb tracer, followed by U and Pb purification, and TIMS analyses. Previous to dissolution, the U-Pb isotopic compositions of the same cassiterite aliquots are characterized via laser-ablation-inductively coupled-mass spectrometry (LA-ICP-MS) and each cassiterite fragment is imaged with an ultra-fast washout laser ablation system to obtain high-resolution maps of the content and distribution of key trace elements (e.g. U, Pb, Fe, REE).

These two samples show variable but high U concentrations (2-20 ppm) and produce U-Pb isochron ages with 1% precision and low dispersion. We compare these new materials with established RMs (Yankee [2]; AY-4 [3]) and discuss their usability as primary reference materials for microbeam applications.

[1] Neymark, L. A., et al., Chemical Geology. 2018, 483, 410-425.

[2] Carr, P.A., et al., Chemical Geology. 2020, 539, 119539.

[3] Yuan, S., et al., Ore Geology Reviews. 2011, 43, 235–242.

How to cite: Tavazzani, L., Szymanowski, D., Carr, P., Guillong, M., Buret, Y., Cortes-Calderon, E. A., Mercadier, J., and Chelle-Michou, C.: Two new cassiterite reference materials for in-situ U-Pb dating from the European Variscan metallogenic belt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16536, https://doi.org/10.5194/egusphere-egu24-16536, 2024.

EGU24-16896 | ECS | Posters on site | GMPV2.3 | Highlight

Synthesising homogeneous carbonate reference materials for in situ U–Pb calcite geochronology 

Dawid Szymanowski, Nico Kueter, Marcel Guillong, Lorenzo Tavazzani, and Ismay Vénice Akker

Recent years have seen a rise in applications of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to elemental and isotopic analysis of a wide range of geological materials, with a true explosion of in situ geochronology. Standardising such analyses relies on a homogeneous matrix-matched primary reference material (RM) whose ablation, transport and ionisation characteristics will result in fractionating elements and isotopes in the same way as in the unknown of interest.

One of the current frontiers of LA-ICP-MS geochronology – U–Pb dating of carbonates – suffers from a lack of such a material. Because the currently used primary RMs (e.g. WC-1 [1]) are heterogeneous in both age and U/Pb ratio, isotopic ratios are corrected on an isochron (whole-sample) basis rather than for each individual analytical spot, which imposes excess uncertainty on all U–Pb ages obtained this way. The U–Pb carbonate geochronology community is thus in urgent need of homogeneous reference materials for wide distribution. Ideally, such a RM should match the ablation behaviour of the unknown carbonate and consequently all matrix effects, including the amount and depth progression of inter-element laser induced elemental fractionation (LIEF), can be corrected directly, as is standard in e.g. zircon U–Pb geochronology.

We present a method for preparing synthetic RMs that uses a natural rock starting material which is milled to nano-powder, homogenised, and recrystallised using high-pressure, high-temperature apparatuses. In this way, natural sample heterogeneity is removed through milling, while textural coarsening is aimed at generating ablation behaviour similar to that of routine unknown samples.

Initial tests of synthetic calcite materials demonstrate the ability to achieve homogeneity at the spatial scale of a typical LA-ICP-MS laser spot size (80–110 µm typical for calcite U–Pb), while the ablation rate and LIEF are comparable to those of a range of commonly used calcite RMs. This suggests that experimental manufacturing of recrystallised carbonate is a promising avenue to obtain primary RMs that will allow spot-by-spot correction of LIEF in U–Pb analyses, thereby significantly reducing the reliance on heterogenous natural calcite RMs and improving the precision and accuracy of this analytical method.

Finally, this approach may serve as a blueprint for larger-scale production of primary RMs for a variety of matrices and isotopic systems for which there are no natural RMs characterised by the necessary homogeneity or availability.

[1] Roberts, N.M.W., et al., Geochemistry Geophysics Geosystems, 2017, 18(7): 2807-2814.

How to cite: Szymanowski, D., Kueter, N., Guillong, M., Tavazzani, L., and Akker, I. V.: Synthesising homogeneous carbonate reference materials for in situ U–Pb calcite geochronology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16896, https://doi.org/10.5194/egusphere-egu24-16896, 2024.

EGU24-17149 | ECS | Orals | GMPV2.3

µID-TIMS: A Focused Ion Beam (FIB)–Femtosecond (Fs) Laser Microsampling Protocol for Spatially Resolved High-Precision Zircon Geochronology  

Sava Markovic, Jörn-Frederik Wotzlaw, Dawid Szymanowski, and Cyril Chelle-Michou

High-precision (CA-ID-TIMS) U-Pb geochronology of individual growth zones of zircon has been a long-awaited milestone in the geochronological community. Focused ion beam (FIB) and femtosecond (fs) laser machining monitored in real time by CL-SEM both show promise as techniques for physical extraction of target zircon domains in preparation for spatially resolved ID-TIMS dating. In this contribution, we test a novel laboratory protocol for zircon microsampling using an in-house multi-ion plasma (Ar-Xe) FIB and fs laser, and showcase first µID-TIMS zircon dates. We first examine the chemical impacts of protective metal coatings (Cr, Pt-Pd and C) used for ion milling on the U-Pb systematics of a low-Pb and a low-U zircon. We then present high-resolution transmission electron microscope (TEM) images of a zircon surface irradiated by ion and fs laser beams to show the contrasting extent of structural damage induced by the two techniques at standard microsampling conditions. Potential Pb-loss/U-gain in the nanometer-wide ion damaged layer in zircon is mapped by atom probe tomography (APT). Subsequently, we showcase the FIB workflow for extracting a number of microsamples of the Mud Tank and GZ-7 reference zircon spanning the sizes expected in future applications using natural zircon. We present first results of spatially resolved high resolution (µID-TIMS) dating of the Mud Tank and GZ-7 microsamples, and explore the achieved analytical accuracy and precision. Finally, we discuss the feasibility of conducting a µID-TIMS study on natural zircon given zircon features (i.e., age, U content, and volume of target domain) and research objective, and discuss benefits and limits to our approach.

How to cite: Markovic, S., Wotzlaw, J.-F., Szymanowski, D., and Chelle-Michou, C.: µID-TIMS: A Focused Ion Beam (FIB)–Femtosecond (Fs) Laser Microsampling Protocol for Spatially Resolved High-Precision Zircon Geochronology , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17149, https://doi.org/10.5194/egusphere-egu24-17149, 2024.

EGU24-17192 | Posters on site | GMPV2.3

Laser Ablation – Cavity Ring Down Spectrometry, a new method for the in-situ analysis of δ13C of organic and inorganic carbonates 

Ciprian Stremtan, Jan Wozniak, Cristina Montana Puscas, and Tudor Tamas

Elemental analyzers (EA) are the go-to sample introduction instrument for light stable isotope analyses of solid materials. Sample preparation is labor intensive and time consuming, with high associated consumable and equipment cost. Sample recovery is impossible in case of malfunctioning, i.e., no repeat analysis when sample amount is restricted.

In the same way, Laser ablation (LA) is traditionally considered a sample introduction technique for Inductively Coupled Plasma Mass Spectrometry (ICP MS) where plasma-based instrumentation will ionize and measure with a high degree of accuracy and precision the aerosol generated during the ablation process.

In this contribution we present an innovative method of measuring C stable isotopic ratios of carbonates by hyphening two instruments that are not usually found in the same lab. We coupled a laser ablation system (Teledyne Photon Machines Fusions CO2) equipped with a specially designed ablation chamber (Terra Analitic isoScell Δ100) to a Cavity Ring Down Spectrometer (Picarro G2201-i) to perform spatially resolved, highly accurate and precise measurements of both inorganic (stalagmite) and bioaccumulated (freshwater bivalve) carbonate samples. This novel system requires minimal sample preparation, allows for in-situ sequential and repeat sampling, all while eliminating the need to individually prepare samples.

How to cite: Stremtan, C., Wozniak, J., Puscas, C. M., and Tamas, T.: Laser Ablation – Cavity Ring Down Spectrometry, a new method for the in-situ analysis of δ13C of organic and inorganic carbonates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17192, https://doi.org/10.5194/egusphere-egu24-17192, 2024.

EGU24-18378 | Posters on site | GMPV2.3 | Highlight

Potential matrix-matched reference material for in-situ garnet U-Pb dating 

Aratz Beranoaguirre, Leo J. Millonig, Maria V. Stifeeva, Richard Albert, Horst Marschall, and Axel Gerdes

Well-characterized matrix-matched reference materials are an indispensable requisite for mineral dating by LA-ICPMS. Recently, the in-situ U-Pb dating of low-U minerals (<20 µg/g) has emerged as a cutting-edge technique in the field of geochronology. The methodology has especially been applied to carbonate and garnet, although other minerals such as sulfate, ilmenite, staurolite, etc., are likely dateable by the same technique. However, the ability to expand this technique to such phases is hampered by the scarcity of reliable reference materials, creating a strong need for investigating and developing appropriate materials with well-constraint ages and homogeneous isotopic compositions.

During the last few years, the FIERCE laboratory has been investigating reference materials for garnet dating. Analysing garnet crystals from different localities and of various U and Pb contents, we found that four garnet localities have the potential to become reference materials for in-situ U-Pb studies. On the one hand, the availability of garnet crystals is sufficient to be distributed to laboratories worldwide. On the other hand, the garnet crystals analysed at FIERCE are relatively homogeneous, except for specific domains like rims, which showed slightly different ages (Millonig et al., 2023). The studied specimens come from Balochistan, with an approximate age of 45 Ma; Mongolia (ca. 130 Ma); Mali (black variety, different to the popular “Red-Mali”, age of ca. 200 Ma) and the Lake Jaco district in Mexico (pink variety, ca. 35 Ma). For this contribution, we have done an intra-crystal, inter-crystal and inter-session comparative study of the different localities, analysing multiple crystals from each locality over multiple analytical sessions. The potential reference materials analyses have been cross-calibrated against garnet crystals of known age (ID-TIMS age) and yield reproducible ages between different analytical sessions. Furthermore, garnet from the four localities will also be analysed by TIMS to provide independent age constraints.

How to cite: Beranoaguirre, A., Millonig, L. J., Stifeeva, M. V., Albert, R., Marschall, H., and Gerdes, A.: Potential matrix-matched reference material for in-situ garnet U-Pb dating, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18378, https://doi.org/10.5194/egusphere-egu24-18378, 2024.

EGU24-18595 | ECS | Orals | GMPV2.3

Stability of magnesite (MgCO3) in the presence of a hydrous fluid in the upper mantle 

Melanie J. Sieber, Hans Josef Reichmann, Robert Farla, and Monika Koch-Müller

Understanding the stability of carbonates under high pressure and temperature is essential for modelling the carbon balance and cycle in the deep Earth. In the presence of an H2O-containing fluid, the melting curve of carbonates can be strongly reduced to a lower temperature. Since magnesite is an important carbonate host in the Earth's mantle, the melting curve of magnesite in the presence of an H2O-containing fluid is of particular interest.

Here we report results from in situ synchrotron energy dispersive X-ray diffraction experiments and use texture observations from ex situ falling sphere experiments in the brucite-magnesite system between 1 and 12 GPa. We define the dehydration and melting curve of brucite and elucidate the stability of magnesite in the presence of a liquid and periclase.

The observed liquidus provides information on the fate of magnesite-bearing rocks in subduction zones. Our results show that magnesite remains stable under typical subduction zone gradients even when infiltrated by hydrous fluids released by dehydration reactions during subduction. We conclude that magnesite can be subducted to depths below the arc and beyond. Our results therefore have important implications for the carbon budget of the Earth's mantle and its role in the regulation of the carbon cycle.

How to cite: Sieber, M. J., Reichmann, H. J., Farla, R., and Koch-Müller, M.: Stability of magnesite (MgCO3) in the presence of a hydrous fluid in the upper mantle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18595, https://doi.org/10.5194/egusphere-egu24-18595, 2024.

EGU24-19239 | ECS | Posters on site | GMPV2.3

Agulhas Plateau large igneous province emplacement and carbonation constrained by in-situ U-Pb dating, Sr isotope geochemistry and clumped isotope thermometry of calcite veins in basaltic basement at IODP Site U1582 

Derya Gürer, Matthew M. Jones, Steve M. Bohaty, Stefano M. Bernasconi, Lucien Nana Yobo, and Andrew P. Roberts

Continental breakup leads to formation of new oceanic gateways, evolution of ocean bathymetry, and, in many cases, emplacement of large igneous provinces (LIPs). Changes in ocean circulation, volcanic CO2 emissions, and alteration of freshly emplaced ocean crust associated with these events were likely drivers of global-scale Cretaceous climate change. Yet, the precise timing and nature of Cretaceous continental rifting and submarine LIP eruptions remain largely unconstrained. The Agulhas Plateau (AP), along with Maud Rise (MR) and Northeast Georgia Rise (NEGR), are thought to constitute a once contiguous submarine LIP that was emplaced in the gateway between the incipient South Atlantic, Southern Ocean, and Indian Ocean basins during the breakup of Africa and East Antarctica. International Ocean Discovery Program (IODP) Expedition 392 recovered sedimentary and igneous rocks from the Agulhas Plateau, southwest Indian Ocean, including basaltic pillow lavas at IODP Site U1582, located on the northernmost edge of the plateau. Calcite veins and infills hosted in pillow lavas can provide insights into the timing and chemical environment of post-magmatic fracturing, fluid circulation, submarine weathering and carbonation of the LIP. We present in-situ U/Pb ages (n=12) of the calcite veins determined via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), clumped isotope (Δ47) compositions (n=6) and 87Sr/86Sr ratios to investigate the timing and temperature of calcite precipitation. U/Pb geochronologic dates for vein calcite and infill are reproducible and yield Cenomanian to Turonian ages, consistent with shipboard nannofossil biostratigraphic age constraints for sediments intercalated between the pillows. Reproducible clumped isotopic paleotemperatures range from ~19 to 26°C, with a calculated δ18O value for precipitating fluids of ~-2 to +1‰ Vienna Standard Mean Ocean Water (VSMOW). The ranges of both these values are consistent with ambient mid-Cretaceous marine waters and, when combined with the age constraints for the basalt and sediments, support rapid weathering and carbonation of the submarine LIP following post-eruptive cooling. U/Pb geochronology of calcites at IODP Site U1582, refined by Sr isotope stratigraphy, provide a minimum age for the Agulhas Plateau. These data constrain the timing of the formation of a paleobathymetric restriction at the gateway between several incipient Cretaceous ocean basins, and have implications for geochemical interactions between mafic igneous rocks and seawater through the life cycle of a Cretaceous LIP.

How to cite: Gürer, D., Jones, M. M., Bohaty, S. M., Bernasconi, S. M., Nana Yobo, L., and Roberts, A. P.: Agulhas Plateau large igneous province emplacement and carbonation constrained by in-situ U-Pb dating, Sr isotope geochemistry and clumped isotope thermometry of calcite veins in basaltic basement at IODP Site U1582, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19239, https://doi.org/10.5194/egusphere-egu24-19239, 2024.

EGU24-19715 | Orals | GMPV2.3

In situ Lu-Hf dating of garnet and apatite as a means to understand fluid processes 

Kathryn Cutts, Krisztian Szentpeteri, Seppo Karvinen, Stijn Glorie, Asko Käpyaho, and Hugh O'Brien

Understanding fluid processes is crucial for understanding the magmatic and metamorphic evolution of rocks, as well as mineral transport and deposition. Targeted in situ geochronology of minerals which have interacted with fluids allow us to investigate the temporal evolution of these fluid systems. Combined with trace element analysis or stable isotope analysis it is possible to gain insight into the nature of source of mineralising fluids. These results contribute to modelling and understanding of mineral systems which can be used for targeting mineral deposits.

Early results of this work are presented based on situ Lu-Hf geochronology applied to garnet and apatite associated with a variety of mineral deposits from Finland. The mineral deposits are hosted in rocks are variable age (Archean to Proterozoic) and all were affected by the Svecofennian orogeny (1.92-1.78 Ga) causing deformation, metamorphism and/or remobilisation.

The Siilinjärvi P deposit hosted in a 2.61 Ga carbonatite (Karhu et al., 2001) presents apatite ages ranging from 2050 to 2260 Ma and calcite ages of 1800 to 1920 Ma indicating potentially several phases of fluid remobilisation which may be prior to or during the Svecofennian orogeny.

The Kiviniemi Sc deposit is hosted in a garnet bearing ferrodiorite (1857 ± 2 Ma, U-Pb zircon; Halkoaho et al 2020). In situ Lu-Hf analysis of garnet produces an age of 1824 ± 18 Ma and for apatite an age of 1835 ± 19 Ma.

Garnet and apatite geochronology has also been applied to Li bearing pegmatites in the Somera-Tammela pegmatite province in Southern Finland. Garnet gave an age of 1801 ± 53 Ma and apatite gives 1835 ± 26 Ma. A second sample produced a nearly identical apatite age of 1835 ± 15 Ma.

Two garnets were sampled from inferred Archean deposits, the Sotkamo silver Mine is hosted in the Tipasjärvi Greenstone Belt and the Hosko gold deposit hosted in the Ilomantsi Greenstone Belt. In Sotkamo garnet from a quartz vein hosting base metal mineralisation produced a Lu-Hf age of 1870 ± 27 Ma. Two garnet samples were dated from the Hosko gold deposit, in mineralised sediments, garnet associated with vein quartz produced an age of 1837 ± 4 Ma. A granitic vein cross-cutting the ore hosting sediments gave an age of 2620 ± 7 Ma, although this sample clearly recorded a resetting event with younger ages obtained from the rim.

Despite only have the age results so far, it is clear that the Svecofennian orogeny had a strong impact on mineral systems, reworking of deposits thought to be Archean.

 

Halkoaho, T., Ahven, M., Rämö, O.T., Hokka, J., Huhma, H., 2020, https://doi.org/10.1007/s00126-020-00952-2

Karhu, J.A., Mänttäri, I., Huhma, H., 2001. Radiometric ages and isotope systematic of some Finnish carbonatites. University Oulu, Res. Terrea, Ser. A. No. 19.8.

How to cite: Cutts, K., Szentpeteri, K., Karvinen, S., Glorie, S., Käpyaho, A., and O'Brien, H.: In situ Lu-Hf dating of garnet and apatite as a means to understand fluid processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19715, https://doi.org/10.5194/egusphere-egu24-19715, 2024.

GMPV3 – Low-temperature metamorphism and fluid-rock interaction

The Tabei uplift is located in the northern part of the Tarim Basin, while the Lunan area is in the eastern part of Tabei uplift. The dryness coefficients of natural gas range from 0.62 to 0.99 (average: 0.92), the methane contents range from 30.42% to 96.4% (average: 85.10%), and the methane carbon isotopes range from -47.30‰ to -33.80‰ (average: -36.96‰) in the Lunnan area. Compared with the actual regional thermal evolution of the source rock, the natural gas exhibits excessively heavy dryness coefficients and methane carbon isotope characteristics. To investigate the genesis of heavy methane carbon isotopes and dry gas in different areas of the Tabei Uplift. Natural gas chemical composition and carbon isotope were used to analyze the genesis of natural gas, basin modeling was conducted to reconstruct the natural gas generation process, and the geologic causes of this phenomenon are discussed. The results show that the natural gas is primary cracking gas and sourced from marine type II kerogen. The dryness coefficient, methane carbon isotopes, and source rock maturity gradually increases from the west to the east. Instantaneous effects led to the dry gas and relative heavy methane carbon isotopes generated at a low maturity level. The current natural gas in the Ordovician reservoirs was all generated during the Himalayan orogeny. Long period pause of the gas generation between the two hydrocarbon generation phases is the main cause for the instantaneous effects.

How to cite: Liu, X., Tian, J., Liu, Z., and Cong, F.: The generation mechanism of deep natural gas, Tabei uplift, Tarim Basin, Northwest China: insights from instantaneous and accumulative effects, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2342, https://doi.org/10.5194/egusphere-egu24-2342, 2024.

EGU24-5003 | ECS | Posters on site | GMPV3.2

Importance of mantle serpentinite carbonation in bending faults for the deep carbon cycle 

Yongsheng Huang, Satoshi Okumura, Kazuhisa Matsumoto, Naoko Takahashi, Hong Tang, Guoji Wu, Tatsumi Tsujimor, Michihiko Nakamura, Atsushi Okamoto, and Yuan Li

Serpentinite carbonation contributes to the deep carbon (C) cycle. Recently, geophysical and numerical studies have identified considerable hydrothermal alterations in deep bending faults beneath outer-rise regions, implying potentially significant C storage in the slab mantle. However, quantitative determination of C uptake in outer-rise regions is lacking. Here, we experimentally constrained the serpentinite carbonation in H2O–CO2–NaCl fluids under bending fault conditions to estimate C uptake in the slab mantle. We found that serpentinite carbonation produced talc and magnesite along the serpentinite surface. The porous reaction zones (49.2% porosity) promoted the progress of the carbonation reaction through a continuous supply of CO2-bearing fluids to the reaction front. Strikingly, NaCl effectively decreased the serpentinite carbonation efficiency, particularly at low salinities (< 5.0 wt%), which is likely attributed to the reduction in H2O and CO2 activities (aH2O and aCO2) and transport rate of reactants, the change in pH of fluids, and the enhancement of magnesite solubility. We fitted an empirical equation for the reaction rate of serpentinite carbonation in bending faults and found that this reaction could contribute to a flux of 25–100 Mt C/yr in subduction zones. Our results shed new light on the deep C cycle and the serpentinite carbonation in environments with high salinities.

How to cite: Huang, Y., Okumura, S., Matsumoto, K., Takahashi, N., Tang, H., Wu, G., Tsujimor, T., Nakamura, M., Okamoto, A., and Li, Y.: Importance of mantle serpentinite carbonation in bending faults for the deep carbon cycle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5003, https://doi.org/10.5194/egusphere-egu24-5003, 2024.

EGU24-5717 | ECS | Orals | GMPV3.2 | Highlight

Potential sequestration of toxic elements: the specific example of cadmium and carbonates 

Maude Julia, Christine V. Putnis, François Renard, and Oliver Plümper

Coupled dissolution-precipitation reactions have been studied extensively recently for their ability to retain elements of interest into a stable solid form that can sequester potentially toxic elements. This is achieved through the initial dissolution of a substrate mineral in a fluid containing the target (often toxic) element. The dissolution leads to the supersaturation of a boundary layer at the mineral surface with respect to another solid phase containing the element of interest1. When the relative solubilities of the different minerals (in the aqueous fluid at the reaction interface) and their molar volume difference allow it, a coupled dissolution-precipitation can lead to the pseudomorphic replacement of the original substrate2. We tested this reaction for CaCO3 and cadmium (Cd) containing solutions as calcite (CaCO3) and otavite (CdCO3) form an almost perfect solid solution. We compared the reaction in similar solutions with different types of CaCO3: calcite single crystal, Carrara marble (polycrystalline calcite) and aragonite single crystals. For single calcite crystals, the reaction in a Cd-solution passivates the crystal’s surface due to the epitaxial growth of a (Ca,Cd)CO3 solid solution layer of low solubility. However, the random orientation of the grains in the Carrara marble samples and the change of crystal structure for the aragonite crystals modified the mechanism and allow the replacement of CaCO3 by (Ca,Cd)CO3 to take place3. Hydrothermal experiments and in situ fluid-cell atomic force microscopy (AFM) were used to observe the reaction both at room temperature and high pressure and temperature (200°C). In addition to SEM, BSE and EDX observations, synchrotron X-ray microtomography images were acquired on Carrara marble and aragonite samples at different stages of the reaction in order to gather more information about the replacement mechanism and the extent of Cd-uptake achievable through this process. The extent of the reaction was shown to be similar for the different solution concentrations used and limited in the case of Carrara marble. The porosity closes fast after the start of the reaction blocking the fluid pathways necessary for the reaction to proceed. The reaction in the aragonite samples seems to progress mainly through a reaction-induced fracture network probably created by the stress caused by the crystallographic structural differences between parent and product phases. Overall, these results demonstrate the capacity of CaCO3 to trap and store cadmium into a solid phase by a mechanism of coupled dissolution-precipitation.

 

(1)        Putnis, C. V.; Putnis, A. A Mechanism of Ion Exchange by Interface-Coupled Dissolution-Precipitation in the Presence of an Aqueous Fluid. Journal of Crystal Growth 2022, 600, 126840. https://doi.org/10.1016/j.jcrysgro.2022.126840.

(2)        Pollok, K.; Putnis, C. V.; Putnis, A. Mineral Replacement Reactions in Solid Solution-Aqueous Solution Systems: Volume Changes, Reactions Paths and End-Points Using the Example of Model Salt Systems. American Journal of Science 2011, 311 (3), 211–236. https://doi.org/10.2475/03.2011.02.

(3)        Julia, M.; Putnis, C. V.; King, H. E.; Renard, F. Coupled Dissolution-Precipitation and Growth Processes on Calcite, Aragonite, and Carrara Marble Exposed to Cadmium-Rich Aqueous Solutions. Chemical Geology 2023, 621, 121364. https://doi.org/10.1016/j.chemgeo.2023.121364.

How to cite: Julia, M., Putnis, C. V., Renard, F., and Plümper, O.: Potential sequestration of toxic elements: the specific example of cadmium and carbonates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5717, https://doi.org/10.5194/egusphere-egu24-5717, 2024.

EGU24-8161 | ECS | Posters on site | GMPV3.2

Rodingite Occurrence in Ciletuh Ophiolitic Mélange Complex (Indonesia): Evidence of Fluid-Rock Interaction in Subducted Oceanic Crust 

Rinaldi Ikhram, Takashi Hoshide, Tsukasa Ohba, and Mega Fatimah Rosana

The presence of ophiolitic mélanges in the Indonesian archipelago has been acknowledged as pivotal for the paleo-tectonic reconstruction of the Southeast Asia Region (southwestern Sundaland). However, the occurrence of rodingite as an integral component of ophiolite in Indonesia has not been thoroughly documented. The rodingites within the Ciletuh Ophiolitic Mélanges in Western Java are notably fresh and widespread, providing a valuable opportunity to initiate comprehensive research on rodingites, particularly focusing on the interplay of metasomatism between serpentinite and meta-gabbro. These metasomatic processes can provide valuable insights into reconstructing the evolution of P-T conditions and elemental transfer involving fluids in a subduction zone. This study aims to focus on field occurrences, petrography, whole-rock geochemistry, with the application of P-T pseudosection modeling to describe their metamorphic conditions.

Rodingitized gabbro in Ciletuh occur as dykes intersecting serpentinized peridotite with sharp and diffuse contact. These dykes are controlled by faults in direction opposite perpendicular or diagonal to the shearing direction of serpentinites. Sheared-foliated rodingite and serpentinite are common, usually forming boudinages. Rodingites are classified into six types which are: (1) Fine to medium grain clinopyroxene rich, (2) Fine to medium grain hydrogarnet rich, (3) Coarse grain, (4) Schistose, (5) Diffused serpentinite-rodingite at peripheral dyke, and (6) Diffused serpentinite-rodingite embedded within serpentinite.  Type (1) to (3) are dykes which mostly composed by garnetized plagioclase (47-49%) and clinopyroxene (29-32%), orthopyroxene (20%), olivine (<3%), epidote (<5%), zoisite (<3%) with minor spinel and magnetite (2-4%). Type (4) is comprised of foliated mineralogical domains such as carbonate-rich and chlorite-rich domain. Types (5) and (6) are characterized with diffused contact of rodingite (hydrogarnets) and chloritized serpentinite. Chlorite reaction zones can be encountered at the contacts between rodingite and serpentinite, typically indicated by the presence of chloritized groundmass, chloritized serpentine mesh, chlorite and hydrogarnet veinlets, as well as partial clinopyroxene rim around hydrogarnet.

The general whole rock geochemical characteristics of rodingitized gabbro are indicated by low SiO2 content (34-42 wt%), high CaO (3-16 wt%), high MgO (17-32 wt%), medium Al2O3 (5-10 wt%), and FeOt (5-18 wt%), with high LOI (5-10 wt%). Significant whole rock geochemical variations characterize the serpentinite-rodingite reaction zones in both the sharp dykes (Type 1-3) and diffused (Type 5-6) contact. Serpentinite near the reaction zone exhibits enrichment in Al2O3, CaO, but depletion in MgO, FeO, and SiO2. Conversely, rodingitized gabbro experiences enrichment in MgO, slight enrichment in FeO, and depletion in CaO and Al2O3.  

P-T psedosection models show that rodingitization occured concurrently with serpentinization during medium to low-grade metamorphism at temperatures ranging from 200 to 490˚C. This process involved diffusional metasomatism with fluids derived from serpentinization and metamorphism of gabbro (e.g., Ca, Mg, and Al), considering the addition of H2O and other potential fluids during the exhumation of ophiolitic mélanges in the subduction slab.

How to cite: Ikhram, R., Hoshide, T., Ohba, T., and Rosana, M. F.: Rodingite Occurrence in Ciletuh Ophiolitic Mélange Complex (Indonesia): Evidence of Fluid-Rock Interaction in Subducted Oceanic Crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8161, https://doi.org/10.5194/egusphere-egu24-8161, 2024.

EGU24-9404 | ECS | Posters on site | GMPV3.2

Experimental insights into fluid and melt generation by dehydration reactions of micas with implications for crustal processes 

Maria M. Repczynska, Aitor Cambeses, Jose Francisco Molina, Pilar Montero, and Fernando Bea

It is now widely known that the fluids play a major role in the formation and evolution of the Earth´s crust. Fluids and melts formed by dehydration-melting reaction of muscovite, biotite and amphibole during prograde metamorphism can have a profound effect on the trace element and isotope composition on the crustal sources of magmas.

However, while the phase relations of these reactions as well as the textural and mineralogical evidence of fluid-rock interaction in high-grade metamorphic complexes are well studied, the mechanisms of the onset of fluid and melt generation by the dehydration melting along with the transport and geochemical impact of these mobile phases onto anhydrous minerals at the grain scale remain unclear.

We investigated the mechanisms of local reactions involved in the incipient dehydration/melting processes at different temperatures, the sequence of reactions and the interaction of the fluid and/or melt with the anhydrous mineral phases, by conducting analogue heating experiments of rock cylinders in a vertical furnace. The rock samples used in the experiments were granitoids and gneisses from the Iberian Massif (Spain) with variable content of biotite and muscovite. They were cut into cylinders with dimensions of about 3x20 cm and placed into a vertical furnace. The experiments were done under thermal gradient at sub- and supersolidus conditions (600-1200oC) at ambient pressure in an inert atmosphere of N2 and last up to 8 days.

First results show that significant compositional and textural changes in biotite and muscovite were produced in experimental runs at temperatures >850oC. Muscovite experienced dehydration melting breakdown to ultrabasic, very peraluminous melts with higher Na and lower K than the starting muscovite, small grains of aluminosilicates and large vesicles. Biotite underwent subsolidus dehydration, resulting in the formation of spinel and/or Fe-Ti oxides and alkali-rich aqueous fluid. Notably, K-feldspar did not nucleate at the dehydration site; instead, excess K and other incompatible elements (Li, Rb, Cs, Ba) were transported by fluids released from biotite and muscovite. These fluids subsequently induced metasomatic reactions in plagioclase, transforming it into K-feldspar. Additionally, Ca released from plagioclase contributed to the formation of titanite after ilmenite. The metasomatic changes were facilitated by fluid migration along micropores that were present in the starting plagioclase, highlighting the intricate processes involved in mica driven metamorphism and metasomatism. A second type of melt was generated with increasing temperature, characterized by higher silica and more granitic-like compositions, suggesting the involvement of quartz and feldspars in the melting reactions.

Although the experimental pressure conditions are much lower than those inside the crust, these analogous experiments allow us to investigate the mechanism by which fluids and melts are segregated from the reaction sites and the influence of rock texture. In these analogue experiments the breakdown of hydrous minerals is enhanced because they are outside their P-T stability fields. Besides, the formation of gas is maximized since its solubility in the melt is very low. Therefore, it allows us to investigate the importance of vesiculation in the creation of pathways for fluid and melt migration.

 

How to cite: Repczynska, M. M., Cambeses, A., Molina, J. F., Montero, P., and Bea, F.: Experimental insights into fluid and melt generation by dehydration reactions of micas with implications for crustal processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9404, https://doi.org/10.5194/egusphere-egu24-9404, 2024.

EGU24-11453 | ECS | Orals | GMPV3.2

Integrated Modeling of Cu-Rich Fluid Migration and Mineralization in the Katangan Basin, Central African Copperbelt: Insights from Numerical Experiments 

Meissam Bahlali, Julia Woitischek, Carl Jacquemyn, Martin Purkiss, and Matthew Jackson

Sediment-hosted Cu deposits are a significant global source of copper. This study employs a mineral system approach, focusing on basin-scale groundwater flow as a key mechanism for Cu transport from source to trap. Numerical experiments using the open-source IC-FERST code investigate the controls on Cu transport in the Katangan Basin, Central African Copperbelt. The models developed for early and late stages of basin evolution incorporate fluid flow, heat and solute transport, and dynamic mesh optimization to enhance computational efficiency.

The early-stage model, corresponding to the salt deposition period, attributes the formation of saline brine to a dense residual phase resulting from evaporite formation. In the late-stage model, corresponding to Cu mobilization and mineralization, Cu dissolution and mineralization are simulated using a partition coefficient informed by experimental data.

Results reveal that density gradients induced by salinity and temperature variations play a crucial role in initiating convective groundwater flow. Highly saline, dense brines generated during salt deposition or dissolution form complex, downward-propagating plumes influenced by flow instabilities and geologic heterogeneity. Permeable faults and fractures in basement rocks enable groundwater to percolate, potentially mobilizing Cu from intra- or extra-basinal source rocks. Salinity and temperature gradients drive upwelling plumes, transporting Cu from deeper source rocks to shallower, organic-rich sedimentary rocks where mineralization occurs.

How to cite: Bahlali, M., Woitischek, J., Jacquemyn, C., Purkiss, M., and Jackson, M.: Integrated Modeling of Cu-Rich Fluid Migration and Mineralization in the Katangan Basin, Central African Copperbelt: Insights from Numerical Experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11453, https://doi.org/10.5194/egusphere-egu24-11453, 2024.

EGU24-11520 | Orals | GMPV3.2

Complex metamorphic and metasomatic history recorded by REE-phosphates in apatite-iron oxide ores from Svalbard 

Jaroslaw Majka, Maria Maraszewska, Daniel E. Harlov, Maciej Manecki, David A. Schneider, Igor Broska, and Perle Inge Myhre

A set of small iron oxide-apatite (IOA) ore bodies have been discovered within polydeformed and polymetamorphosed metasedimentary rocks on Prins Karls Forland, Svalbard. A complex tectonothermal history resulted in the development of various ore structure, varying from brecciated to mylonitised. Generally, the IOA ores are divided into two major geochemical subtypes: (1) fluorapatite-bearing with predominant low-Th monazite, and (2) F-Cl apatite-bearing with predominant high-Th monazite. Initial alteration of the ores resulted in liberation of REE and P from the apatite and redeposition as small (<30 mm), rounded monazite and xenotime crystals. REE and P in solution were likely transported during deformation that probably enhanced the transportation process. In fact, both the iron oxides and phosphates in the intensively deformed ores show features characteristic of fluid-assisted dissolution-reprecipitation creep. Subsequent stages of alteration caused either Th-enrichment of the monazite or even full replacement of low-Th monazite by a high-Th variety. In some of the ore bodies the original fluorapatite incorporated Cl, Mn, and Sr likely due to interaction with a Cl-rich fluid from the surrounding gabbroic and metasedimentary host rocks. The huge variability in the textures and the mineral assemblages from the ore bodies most likely reflect interaction with compositionally variable fluids that were liberated during the protracted tectonothermal evolution of the entire metamorphic complex. Hence, it is concluded that the IOA ores formed as a product of Fe, P, Ca, and REE fractionation from hypersaline fluids associated with the surrounding gabbros and metasedimentary rocks indicating that the ores were subjected to fluid activity during at least one metamorphic event.

How to cite: Majka, J., Maraszewska, M., Harlov, D. E., Manecki, M., Schneider, D. A., Broska, I., and Myhre, P. I.: Complex metamorphic and metasomatic history recorded by REE-phosphates in apatite-iron oxide ores from Svalbard, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11520, https://doi.org/10.5194/egusphere-egu24-11520, 2024.

The circulation of toxic elements through soils, sediments and aquatic environments remains a significant environmental problem, which implies several, often unrecognized health risks. Dissolution and precipitation reactions that result in formation of sparingly soluble crystalline compounds containing toxic elements e.g. As, appear to be a promising strategy for reducing their chemical mobility and bioavailability (Magalhães, 2002; Wang et. al., 2013).

In this study, the processes occurring at the interface of anglesite and solutions containing AsO43- ions were investigated. The results provide insight into the mechanism of As immobilization on the mineral surface through transformation of labile form into less reactive and more thermodynamically stable phases. Synthetic anglesite powder and fragments of natural anglesite crystals (Tsumeb, Namibia) were reacted for up to 3 months with solutions containing AsO43- (50 mg As/l) in the presence of Cl- ions at pH range 2 - 8. The experiments were conducted at room temperature (20 oC) or in the autoclave (120 oC).

Rapid sequestration of As from the solution was associated with precipitation of mimetite Pb5(AsO4)3Cl: over 66% of As was removed within 24 hours. After 7 days of the reaction, the concentration of As decreased from 50 to less than 11 mg As/L. The concentration of Pb2+ ranged from 0.6 mg Pb/L at pH 8 to 20 mg Pb/L at pH 2. Both, homogeneous and heterogeneous precipitation of mimetite was observed, and some anglesite crystals were covered by incrustations. At pH=2, mimetite was associated with schultenite PbHAsO4.

Scanning Electron Microscopy observations of the natural crystals surface, indicated that the reaction of As-containing solutions with anglesite at pH 4-8, involves dissolution of PbSO4, resulting in formation of etch pits, followed by precipitation of randomly intergrown mimetite as a loosely bound crust. The crust was formed in the vicinity but is separated from anglesite surface. In contrary, at very acidic conditions (pH=2), anglesite is replaced by a secondary phase as a result of a coupled dissolution and precipitation, leading to formation of lead arsenate pseudomorph. Surprisingly, temperature had no significant effect on the reaction, while the pH control is of great importance and determines the mechanism.

References:

Magalhães, M. C. F. (2002). Arsenic. An environmental problem limited by solubility. Pure and Applied Chemistry, 74(10), 1843–1850.

Wang, L., Putnis, C. V., Ruiz-Agudo, E., King, H. E., & Putnis, A. (2013). Coupled dissolution and precipitation at the cerussite-phosphate solution interface: Implications for immobilization of lead in soils. Environmental science & technology, 47(23), 13502-13510.

This research was funded by AGH University of Kraków project No 16.16.140.315.  

How to cite: Stępień, E. and Manecki, M.: Arsenate aqueous solution – anglesite PbSO4 interface: dissolution, precipitation, and arsenic sequestration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11970, https://doi.org/10.5194/egusphere-egu24-11970, 2024.

EGU24-12279 | Orals | GMPV3.2 | Highlight

Nanopore Influence on the Geochemical Properties of Water in Earth's Lithosphere 

Oliver Plümper, Alireza Chogani, Helen E. King, and Benjamin Tutolo

Water, a principal component of Earth’s fluids, interacts with rocks in ways that profoundly influence lithospheric phenomena. These interactions are fundamental to both geochemical and geodynamic processes, extending their impact to areas of societal importance such as subsurface energy extraction and storage, and the formation of vital metal deposits for green energy technology. Additionally, the interplay between fluids and rocks significantly affects the Earth's carbon cycle, influencing atmospheric CO2 levels, climate, and overall planetary habitability. The traditional perspective suggests that fluids move through the lithosphere without being affected by the unique properties that emerge when matter is confined to the nanoscale. Contradicting this view, our research reveals that rocks involved in a variety of lithospheric processes consistently show nanoporosity, primarily with pores smaller than 100 nanometers. Within these small spaces, water behaves differently than it does in larger environments. Through molecular dynamics simulations, we have quantified water's relative permittivity—a critical factor in its geochemical behavior— when confined in natural nanopores. Our findings demonstrate that, under a wide range of lithospheric conditions, from ambient to extreme temperatures up to 700 °C and pressures up to 5 GPa, water's permittivity within these nanopores significantly deviates from that in its bulk state. Our thermodynamic equilibrium models indicate that this difference markedly reduces mineral solubility and alters ion speciation in natural settings. These pore-size-dependent properties may exert a primary influence on rock reactivity and the evolution of aqueous geochemistry during fluid-rock interactions.

How to cite: Plümper, O., Chogani, A., King, H. E., and Tutolo, B.: Nanopore Influence on the Geochemical Properties of Water in Earth's Lithosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12279, https://doi.org/10.5194/egusphere-egu24-12279, 2024.

EGU24-12899 | Posters on site | GMPV3.2

Porosity evolution determines available reaction mechanisms in water-rock interactions 

Wolf-Achim Kahl, Christian Hansen, M. Mangir Murshed, Wolfgang Bach, and Juan Manuel Garcia

Fluid-aided mineral replacement plays a key role in metamorphic reactions and metasomatic mass transfers. Within the scope of this study we investigate the role of pore space evolution in the hydrothermal phase transition from gypsum to bassanite. We monitored the partial dehydration of gypsum to bassanite in-situ using an X-ray-transparent flow-through reaction cell (Kahl et al., 2016) during long-term hydrothermal percolation experiments. By repeated, intermittent X-ray microtomography (µ-CT) scans, we surveyed the evolution of the porous system created by the dissolution-reprecipitation process. The quantitative 3D image analysis of the obtained 4D image material shows that incipient bassanite formation takes place in domains well within the interior of the gypsum crystal, presumably located along nano- or microcracks (i.e. at the scale of grain boundaries of the selenite host, and maybe enhanced due to the presence of fluid inclusions), and not directly at the gypsum – fluid interface. After larger volumes of interconnected pores have formed in later stages of the experiment, bassanite nucleation becomes insignificant and bassanite growth is now the dominant fixation mechanism of hemihydrate. The fabric of the final reaction product is controlled by these later-stage elongate bassanite crystals that are oriented along [001] of the former gypsum crystal. Careful data analysis reveals that processes which strongly depend on transient characteristics of the fluid-hosting fabric component are easily obliterated from the rock record. Concerning the predictive numerical simulation of mineral replacement processes in general, these results reveal that the boundary conditions underlying mineral nucleation may not be deduced from observations of the resulting fabric of mineral growth.

 

Kahl, W.-A., Hansen, C., and Bach, W. (2016) A new X-ray-transparent flow-through reaction cell for a mu-CT-based concomitant surveillance of the reaction progress of hydrothermal mineral-fluid interactions. Solid Earth, 7(2), 651-658.

How to cite: Kahl, W.-A., Hansen, C., Murshed, M. M., Bach, W., and Garcia, J. M.: Porosity evolution determines available reaction mechanisms in water-rock interactions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12899, https://doi.org/10.5194/egusphere-egu24-12899, 2024.

EGU24-13089 | ECS | Orals | GMPV3.2

Precipitation in fluid-mineral systems under differential stress investigated through molecular dynamics 

Mattia Luca Mazzucchelli, Evangelos Moulas, Stefan M. Schmalholz, Boris Kaus, and Thomas Speck

The interpretation of mineral equilibria and reactions in rocks assumes uniform hydrostatic pressure across all phases. However, such condition is typically not satisfied in geological systems that are composed of multiple phases that are in contact with one another.  Stress gradients and non-hydrostatic stresses are to be expected in rocks in the lithosphere, even in the presence of fluids. This complexity challenges the reliability of existing hydrostatic thermodynamic models, and, currently, there is still no accepted theory for evaluating the thermodynamic effect of non-hydrostatic stress on reactions [e.g. 1, 2, 3, 4].

Molecular dynamics (MD) allows us to investigate first-order phase transitions in solid-liquid systems under stress, without the a-priori assumption of a specific thermodynamic potential [5]. With MD simulations the energy of the system, the pressure of the fluid, the stress of the solid, as well as the overall melting and crystallization process can be monitored until the stressed system attains the equilibrium conditions. Our findings indicate that under differential stress, the mean stress of the solid deviates progressively from the pressure of the fluid with which it is in equilibrium. At low differential stresses, deviations from the reference hydrostatic equilibrium are small, allowing accurate phase equilibria predictions by considering the fluid pressure as a proxy for equilibration pressure, as suggested by previous experimental investigations [6].

In the presence of substantial non-hydrostatic stresses, equilibrium between solid and fluid occurs at a fluid pressure significantly higher than hydrostatic thermodynamics predicts. However, the stressed system becomes unstable and a rim of a quasi-hydrostatically stressed solid eventually crystallizes around the initial highly stressed solid core. During the crystallization, the total stress balance is preserved until the newly formed solid-solid-fluid system reaches again a stable equilibrium. At the final equilibrium conditions only the low-stressed solid is exposed to the fluid, bringing back the equilibrium fluid pressure close to the value expected for the equilibrium at homogeneous hydrostatic conditions. Therefore, our results suggest that models describing equilibria and reactions in minerals and rocks under stress can assume that phase equilibria are accurately predicted by using the fluid pressure as a proxy of the equilibration pressure.

References

[1] Frolov, T., & Mishin, Y. 2010: Effect of nonhydrostatic stresses on solid-fluid equilibrium. I. Bulk thermodynamics. Physical Review B - Condensed Matter and Materials Physics, 82(17), 1–14.

[2] Hobbs, B. E., & Ord, A. 2015: Dramatic effects of stress on metamorphic reactions. Geology, 43(11), e372.

[3] Tajčmanová, L., Vrijmoed, J., & Moulas, E. 2015: Grain-scale pressure variations in metamorphic rocks: Implications for the interpretation of petrographic observations. Lithos, 216–217, 338–351.

[4] Wheeler, J. 2014: Dramatic effects of stress on metamorphic reactions. Geology, 42(8), 647–650.

[5] Mazzucchelli M., Moulas E., Kaus, B., Speck T. submitted: Fluid-mineral equilibrium under stress: insight from molecular dynamics. American Journal of Science.

[6] Llana-Fúnez, S., Wheeler, J., & Faulkner, D. R. (2012). Metamorphic reaction rate controlled by fluid pressure not confining pressure: Implications of dehydration experiments with gypsum. Contributions to Mineralogy and Petrology, 164(1), 69–79.

 

How to cite: Mazzucchelli, M. L., Moulas, E., Schmalholz, S. M., Kaus, B., and Speck, T.: Precipitation in fluid-mineral systems under differential stress investigated through molecular dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13089, https://doi.org/10.5194/egusphere-egu24-13089, 2024.

Fluid flow within the continental crust, and the concomitant fluid-rock interactions, are likely responsible for mass transfer and significant change in bulk rock chemistry (i.e. metasomatism). Strain localization and formation of ore deposits are very commonly associated to metasomatism. Metasomatic processes are studied combining petrology, geochemistry, fluid inclusion analysis and/or thermodynamic modelling (P-T-X). To model and quantify the mass and fluid flux integrated with time, the driving forces and controlling factor, such as fluid chemistry (solubility, speciation, chlorinity …), P-T conditions and phase relations, the degree of disequilibrium between the fluid and the host-rock must be clearly identified.

This study focuses on phase relations modelling during metasomatic processes based on the mineralogical and chemical characterisation of metasomatic rocks from the Tauern Window. Samples are amphibole- and chlorite-bearing micaschists resulting from the transformation of a granodiorite under amphibolite conditions (550-570°C and 0.5-0.6 GPa). The studied outcrop is similar to some extent to Mg-metasomatic rocks reported in several localities in the Alps, including Dora Maira, Gran Paradiso or Monte Rosa and summarised in Ferrando (2012). Although all the localities reported in Ferrando (2012) and the Tauern window have their own characteristics (eg. different P-T conditions, fluid chemistry, mineralogy, age...), they also share similar features. For instance, the gain in Mg with respect to the protolith is systematically coupled with a gain in fluid, and a loss of Ca, Na and sometimes Si. This shared feature suggests that a unique and simple process must be involved in all these localities.

Thermodynamic models are developed using chemical potentials of perfectly mobile components of the system as variable (µi), following the definition of Korzhinskii (1959). It means that the chemical potential of the mobile component (MgO, CaO, Na2O, SiO2, H2O) is controlled by the environment, which we consider here as an externally-derived fluid. The computed projections and pseudo-sections show that the reequilibration of the granodiorite with the externally-derived fluid (high µMgO and low µCaO, µNa2O, µSiO2) induce a series of metasomatic reactions leading to the breakdown of the granodiorite assemblage into amphibole, then muscovite-chlorite and eventually talc. From these models, it is possible to quantify the amount of mass lost and gained along the defined reequilibration path and eventually estimated the required fluid flux.

How to cite: Amiot, M., Goncalves, P., and Choulet, F.: Phase relation modelling associated with metasomatic processes in open systems: application to an example of Mg-metasomatism from the Neves area, Tauern window, Eastern Alps., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14807, https://doi.org/10.5194/egusphere-egu24-14807, 2024.

EGU24-16710 | Posters on site | GMPV3.2

Nanoscale experiments of intergranular dissolution-precipitation to understand deformation mechanisms in the upper crust.   

Andrea Billarent-Cedillo, Mark Jefferd, Helen E. King, Suzanne Hangx, and Oliver Plümper

In the upper crust, rock deformation commonly occurs in the presence of aqueous fluids, which are known to alter the material's response to stress. These fluids facilitate dissolution and precipitation, driving changes in the mineral composition and texture. The interaction between dissolution-precipitation and deformation in the upper crust has been studied in various natural geological cases, through experimentation, and modeling. Recently, there has been increased emphasis on understanding the role of fluids in deformation at the nanoscale. This experimental study aims to comprehend the effects of deformation on dissolution and precipitation at the nanoscale, specifically at the boundary between individual mineral grains.

Our research has focused on understanding quartz dissolution and precipitation at the grain boundary scale at hydrostatic pressures and temperature conditions representative of the upper 5 km of the crust. We report preliminary findings from our experiments on nano-milled quartz crystals, representing natural grain boundary geometry, in contact with different aqueous solutions in a closed system. The pH, salinity, and concentration of Si in solution were systematically altered to assess their impact on dissolution rates. By using 18O-doped solutions, coupled with nanoscale secondary ion mass spectrometry and atomic force microscopy, we can track the dissolved and re-precipitated material, and monitor the changes in the geometry of the nano-milled quartz surface. This constitutes the initial step in our effort to further explore and quantify the effects of differential stress at the grain boundary. Additionally, we present results from a pilot study designed to test how differential normal stress impacts asperity dissolution within quartz-quartz contacts. These experiments aim to improve our understanding of dissolution rates in relation to pressure solution, a significant deformation mechanism in sedimentary and fault rocks.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie initial training network (FluidNET) grant agreement no. 956125.

 

How to cite: Billarent-Cedillo, A., Jefferd, M., King, H. E., Hangx, S., and Plümper, O.: Nanoscale experiments of intergranular dissolution-precipitation to understand deformation mechanisms in the upper crust.  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16710, https://doi.org/10.5194/egusphere-egu24-16710, 2024.

Reactive transport of solutes in porous media involving dissolution/precipitation reactions may alter the physical properties of intact rocks, such as porosity and permeability. Such processes are difficult to predict and characterize due to heterogeneity at the pore scale, caused by the intimate coupling of chemical and transport processes. So far, experimental studies have mainly focused either on chemical aspects, using short time batch or microfluidic experiments, or on transport, using a porous medium in classical counter diffusion cells. The former approach offers a large flexibility in selecting and modifying parameters like pH, ionic strength, and element concentrations, and thereby allows the systematic derivation of chemical data such as mineral precipitation and dissolution at ex-situ conditions. The latter approach allows studying changes of (bulk) rock transport properties under realistic (in-situ) conditions over longer times, with limited knowledge of pore scale physical and chemical parameters, which may vary in space and time. Therefore, each of these methods limits a full characterization of the evolution of chemistry and transport properties in a realistic porous medium, particularly near the clogging zones that may form due to precipitation.

In this study, we present a methodology that allows the full chemical and physical characterization of reactive transport processes within a porous medium at the microscopic scale (1-10 um). We present experimental datasets that record, the chemical and physical evolution in 300 mm tapered glass capillaries filled with silica gel, in which precipitation of CaCO3 polymorphs has been induced via counter diffusion of Na2CO3 and CaCl2 reservoir solutions. Two counter diffusion systems, one containing 1 mM ZnCl2 in the CaCl2 titrant, the other without Zn, were prepared and evolved for three years. Optical microscopy and synchrotron-based techniques (micro XRF/XRT/XRD, micro XANES and SAXS) were used to characterize the system at selected times (1, 6, 12, 24, 36 months). In both experiments the precipitation of several calcite and/or vaterite crystal aggregates collectively reduced the gel porosity and formed clogging zones in the central part of the capillary. The data obtained for the Zn-free system show that vaterite crystals formed in the calcium rich part of the capillary (i.e., on the side of the CaCl2 titrant) remain stable for the entire duration of the experiment without converting to the more stable calcite. In the Zn-doped system, the vaterite crystals remain stable for 1 year and start to dissolve afterwards. The carbonate ions released via vaterite dissolution did not lead to the formation of new CaCO3 precipitates in the Ca-rich part of the capillary. Instead, a zinc hydroxy carbonate phase is formed.

Through this study, we show for the first time the evolution of a clogging zone in a porous medium at the microscopic scale over an extended period and under truly undisturbed in-situ conditions. Our results show that small concentrations of Zn2+ ions in the pore water have a strong effect on the precipitation/dissolution kinetics of CaCO3 polymorphs, as well as on their crystal morphology.

How to cite: Rajyaguru, A., Curti, E., Ferreira Sanchez, D., Appel, C., and Grolimund, D.: Zinc(II) ions under diffusive regime controls the stability of vaterite: Derivation of pore scale chemical dynamics near CaCO3 clogging interface via coupled micro-XRF/XRD/XANES and SAXS imaging., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17340, https://doi.org/10.5194/egusphere-egu24-17340, 2024.

EGU24-19351 | Posters on site | GMPV3.2

From high-T Hydrothermal Alteration To Near-Surface Weathering – The Alteration History of the Rolvsnes Granodiorite, W Norway 

Kristian Drivenes, Jochen Knies, Tobias Kurz, Annina Margreth, and Jasmin Schonenberg

The Rolvsnes Granodiorite, comprising the major extent of the northern part of Bømlo Island, Western Norway, has been proposed to be an onshore analogue to the weathered basement rocks at Utsira High hosting significant petroleum resources. A total of 205 meters of core in three boreholes was collected crosscutting both fault zones and apparently tectonically undisturbed rocks. Four distinct lithologies were identified in the drillholes: A medium-grained (grano-)diorite, a range of biotite granites, a porphyritic granite, and aplites/pegmatites. All rock types display evidence of hydrothermal alteration as either pervasive discoloration or more localized veining. Early propylitic alteration of the granodiorite is easily observed macroscopically as distinct greening, caused by primary amphibole being replaced by epidote, and calcic plagioclase cores being altered to epidote+muscovite+quartz. The extent and transition of the alteration steps can be observed in the hyperspectral logs. A second generation of epidote can be observed as 1-2 mm veins crosscutting all lithologies. With decreasing temperature and/or higher fluid/rock ratio, biotite is altered to chlorite. Late infiltration of carbonic fluids is evident from calcite veins cutting former alteration types, and ankerite/Fe-rich dolomite + Fe-oxide veins associated with open fractures. 

The clay mineralogy is dominated by smectite and kaolinite, and several meter long sections of the drill cores are near or completely disintegrated from drilling and core handling due to the high smectite content. Kaolinite and smectite may occur together as alteration products, but in open fractures kaolinite is found as infilling in vugs and fractures lined with quartz or associated with the Fe-carbonates, with little or no smectite. This indicates that during late fluid circulation in the faults, kaolinite was precipitated directly from the fluid, and that smectite in the smectite-rich zones was a part of a low temperature pervasive alteration event.

K-Ar dating of the clay-rich alteration zones from this and former studies show a large range of ages, with the ages of the finest (<0.1 µm) fraction ranging from 31 Ma to 281 Ma. The oldest ages are likely mixed or inherited from early events, but apparent clusters around 30-50, 110-140, 200-210, and 265-280 Ma may provide indications of periods of low temperature alteration.   

How to cite: Drivenes, K., Knies, J., Kurz, T., Margreth, A., and Schonenberg, J.: From high-T Hydrothermal Alteration To Near-Surface Weathering – The Alteration History of the Rolvsnes Granodiorite, W Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19351, https://doi.org/10.5194/egusphere-egu24-19351, 2024.

EGU24-20271 | Orals | GMPV3.2 | Highlight

New thermodynamic and kinetic constraints on H2 production during ferroan brucite reaction at low temperature 

Benjamin Malvoisin, William Carlin, Fabrice Brunet, Bruno Lanson, Nathaniel Findling, Martine Lanson, Laurent Jeannin, Tiphaine Fargetton, and Olivier Lhote

The alteration of ferroan brucite, a common by-product of serpentinization, has been proposed as a H2 source at low temperature. Here, synthetic ferroan brucite with Fe/(Fe+Mg) = 0.2 was reacted with pure water at temperatures ranging from 348 to 573 K in 29 experiments either conducted in gold capsules or Ti-based reactors. H2 production monitoring with time and characterization of the reaction products revealed the occurrence of the following reaction: 3 Fe(OH)2brucite = Fe3O4 + H2 + 2 H2O. This reaction proceeds completely in ~ 2 months at 378 K and is thermally activated. The small grain size of the synthetic brucite (40-100 nm) is similar to observations in natural samples, and is probably responsible for the high reaction rate measured. H2 production reached a plateau and Fe-bearing brucite also precipitated as a reaction product, suggesting the achievement of equilibrium. The thermodynamic properties of Fe(OH)2 were refined based on the experimental dataset and differ by less than 5 % from previous estimates. However, ferroan brucite is predicted to be stable at an hydrogen activity one order of magnitude lower than previously calculated. As a result, significant H2 production during ferroan brucite alteration at low temperature requires efficient fluid renewal. Such a mechanism strongly differs from olivine serpentinization which can occur even at high activity in H2 and thus with limited water renewal.

How to cite: Malvoisin, B., Carlin, W., Brunet, F., Lanson, B., Findling, N., Lanson, M., Jeannin, L., Fargetton, T., and Lhote, O.: New thermodynamic and kinetic constraints on H2 production during ferroan brucite reaction at low temperature, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20271, https://doi.org/10.5194/egusphere-egu24-20271, 2024.

EGU24-20323 | ECS | Orals | GMPV3.2

Fluid pathways and metamorphic evolution in the northern part of the Bergen Arcs: the island of Krossøy 

Lorena Hernández Filiberto, Håkon Austrheim, and Andrew Putnis

Fluid migration within the Earth's crust significantly influences the development of shear zones. The Bergen Arcs have been a focal point for investigating the localization of rheologically weaker zones that facilitate shear zone formation, with various hypotheses proposed (Jamtveit et al. 2019; Incel et al. 2022). These zones may originate from seismic events, inducing brittle fracturing and creating pathways for mineral re-equilibration and ductile deformation.

This research concentrates on the island of Krossøy, located in the northernmost part of the Bergen Arcs, Western Norway, offering a unique perspective on deformation, textural evolution, and metamorphism compared to the extensively studied southern regions of Holsnøy and Radøy (Austrheim 1987; Mukai et al. 2014; Moore et al. 2020). Krossøy exposes anorthosites from the old granulitic basement, intruded by a series of subparallel mafic granulitic dykes forming a distinctive "dyke swarm," not documented elsewhere in the Bergen Arcs. We present our results on microstructural analysis through Electron Backscattered Diffraction (EBSD) and, mineral and chemical evolution using Electron Microprobe analysis (EMPA).

Given the plagioclase-rich nature of anorthosites, our results delineate the chemical and textural evolution of feldspars, tracing their journey from early-stage granulitic anorthosite formation approximately 930 Ma ago to the development of Caledonian mylonite (440-420 Ma) during shear zone activity under amphibolite facies conditions. By examining the fluid pathways, we seek to determine their relationship with the formation of rheologically weaker areas in the crust and how the dynamic interplay between fluid infiltration and deformation mechanisms may play an important role by changing the metamorphic conditions, textures and mineral assemblages in the rocks.

Austrheim, H. (1987). Eclogitization of lower crustal granulites by fluid migration through shear zones. Earth and Planetary Science Letters, 81(2–3), 221-232.

Incel, S., Labrousse, L., Hilairet, N. et al. (2022). Reaction-induced embrittlement of the lower continental crust. Geology, 47(3).

Jamtveit, B., Petley‐Ragan, A. et al. (2019). The Effects of Earthquakes and Fluids on the Metamorphism of the Lower Continental Crust. Journal of Geophysical Research: Solid Earth, 124(8), 7725-7755.

Moore J., Beinlich A., Piazolo S., Austrheim H. and Putnis A. Metamorphic differentiation via enhanced dissolution along high permeability zones. Journal of Petrology 61, 10, egaa096 (2020)

Mukai, H., Austrheim, H., Putnis, C. V., and Putnis, A. (2014). Textural Evolution of Plagioclase Feldspar across a Shear Zone: Implications for Deformation Mechanism and Rock Strength Journal of Petrology, 55(8), 1457-1477.

How to cite: Hernández Filiberto, L., Austrheim, H., and Putnis, A.: Fluid pathways and metamorphic evolution in the northern part of the Bergen Arcs: the island of Krossøy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20323, https://doi.org/10.5194/egusphere-egu24-20323, 2024.

EGU24-20669 | ECS | Posters on site | GMPV3.2

Magma Emplacement during active rifting in the upper crust: kinematics and petrology of diabase and host rocks 

Bernardo B. Khater, Renata S. Schmitt, Gustavo L. C. Pires, and Alessandro F. Palmeira

During active rifting, whenever magmatism is present, magma emplacement on the upper crust is usually controlled by brittle structures reactivating an inherited tectonic fabric. In the southeastern Brazilian margin, a Cretaceous NE-SW tholeiitic dyke swarm follows the trend of the Neoproterozoic Ribeira Belt. However, in the coastal area of Rio de Janeiro, it crosscuts orthogonally the Paleoproterozoic orthogneisses of the Cabo Frio Tectonic Domain. In order to investigate how these South Atlantic rift structures formed orthogonally to the inherited host fabric, detailed structural analysis on two key areas was performed, using geological mapping with high-resolution drone images, analyzing the relation of brittle structures, diabase dykes and host rocks. The main set of faults and fractures is oriented parallel to the NE-SW diabase dykes. Dykes bifurcate or change direction abruptly following faults and fractures. Three paleostresses regimes were characterized: (1) a strike-slip transtension with NNE-SSW and NE-SW strike-slip faults; (2) an extensional transtension with oblique NNE-SSW and ENE-WSW faults; and (3) a pure extension with NNE-SSW and ENE-WSW normal faults. The tholeiitic dykes were emplaced during phases 2 and 3 continuously. Syn-kinematic secondary minerals formed on the cataclasites and the host rocks by fluid interaction. Calcite, epidote, chlorite and iron oxide compose a low-grade metamorphism of Ca-, Fe- and Mg- assemblage. These minerals also registered different phases of deformation during paleostresses regimes, with crystallization/precipitation facilitated by thermal injection of the tholeiitic magmas. Increase in permeability of the host rocks by formation of faults and fractures also contributes for the fluid migration, thus contributing with hydrothermal alteration on the upper crust. These mineral reactions also corroborated with the weakening of the continental crust, allied with the increase of dilatant slip surfaces. The combination of these tectonic and hydrothermal processes enabled the emplacement of the NE-SW Serra do Mar Dyke Swarm into the Cabo Frio Tectonic Domain, disregarding the NW-SE inherited tectonic fabric.

How to cite: B. Khater, B., S. Schmitt, R., L. C. Pires, G., and F. Palmeira, A.: Magma Emplacement during active rifting in the upper crust: kinematics and petrology of diabase and host rocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20669, https://doi.org/10.5194/egusphere-egu24-20669, 2024.

GMPV4 – High-temperature metamorphism and orogenic processes

EGU24-14 | ECS | Orals | GMPV4.1

Unusually slow cooling of metamorphic rocks in an orogenic belt: A case from the Bolu Massif (NW Turkey)  

İnal Demirkaya, Gültekin Topuz, and Jia-Min Wang

In this study, we deal with the metamorphic evolution of the amphibolite-facies tectonometamorphic unit of the Bolu Massif, which forms part of the late Neoproterozoic basement of the Istanbul Zone within the Tethyan realm (NW Turkey). The amphibolite-facies tectonometamorphic unit occurs tectonically beneath a tectonometamorphic unit consisting of greenschist-facies metavolcanic rocks intruded by a late Neoproterozoic granitoid. It is ca. 50 km long and 7-8 km wide, and consists of migmatitic amphibolite (~79% of outcrop area), dikes/sill and stocks of trondhjemite (~20%) and minor serpentinite and metapyroxenite (~1%). Comparable amphibolite-facies rocks crop out in several isolated exposures in a narrow belt (~300 km long and up to 20 km wide) parallel to the Intra-Pontide suture which separates the Istanbul Zone from the Sakarya Zone. Amphibolite contains mineral assemblages involving hornblende, plagioclase, ±biotite, ±epidote and ±quartz. Rutile, titanite, apatite and zircon are common accessories. Zr-in-titanite thermometry after Hayden et al. (2008) yields temperatures of 727 ± 17 °C at assumed pressures of 0.7 GPa, while the Zr-in-rutile thermometer after Tomkins et al. (2007) gave significantly lower temperatures (643 ± 7 °C at 0.7 GPa). Because of the high-variance mineral assemblage, metamorphic pressures are difficult to constrain. The presence of igneous epidote in trondhjemite suggests pressures ≥ 0.7 GPa. The equilibration conditions (640-730 °C, 0.7-0.8 GPa) are close to the wet solidus of basalts, suggesting that the migmatization probably occurred by water-present melting. U-Pb dating on zircons from amphibolite and trondhjemitic veins yielded consistent age values of 260-255 Ma. On the other hand, titanite and rutile from the amphibolite yielded lower age values of 231 ± 6 and 181 ± 6 Ma (2σ), respectively. K-Ar hornblende and Rb-Sr biotite whole data from the literature are 222-205 ± 8 and 161-155 ± 2 Ma (2σ), respectively. The coeval nature of the U-Pb zircon dates from amphibolites and trondhjemitic leucosomes suggest that the peak of metamorphism occurred at 260-255 Ma. Given the commonly accepted closure temperatures of minerals for respective isotopic systems, these highly scattered dates suggest that the cooling from the metamorphic peak to 300 °C occurred over an extended period of time (ca. 100 Ma), corresponding to a cooling rate of 4-5 °C/Ma. The absence of marine sedimentary rocks of Late Triassic and latest Early Cretaceous age suggests that the Istanbul Zone was above sea level between Late Triassic and latest Early Cretaceous time (ca. 237 to 100 Ma), and there was no evidence for significant crustal-scale extension. Exhumation at the earth’s surface occurred during the Late Cretaceous, as deduced from unconformably overlying Campanian limestones and the development of Campanian to Ypressian marine sedimentary successions. We suggest that the late Permian metamorphism occurred in a geodynamic setting associated with magmatism in an extensional setting, and static relaxation of the perturbed geotherm between Late Triassic and Early Cretaceous, and exhumation occurred in an extensional setting during the development of sedimentary basin at Late Cretaceous. This study is supported by two grants (TUBITAK #122R002 and ITUBAP #42913). 

How to cite: Demirkaya, İ., Topuz, G., and Wang, J.-M.: Unusually slow cooling of metamorphic rocks in an orogenic belt: A case from the Bolu Massif (NW Turkey) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14, https://doi.org/10.5194/egusphere-egu24-14, 2024.

The pre-Pennsylvanian metasedimentary units (Cosoltepec Formation) of the Acatlán Complex in southern Mexico represent 70-90% of the exposed surface of this complex. The metasedimentary units mainly consist of metapelites, metapsammites and quartzites, as well as sparse pillow basalts and doleritic dikes (Ortega-Gutiérrez et al., 1978). The tectonostratigraphic evolution of these rocks remains a controversial issue in the pre- and post-Orogenic tectonics of the Acatlán Complex. As part of these units, this paper analyses El Pitayo Lithodeme, a low-grade metamorphic unit exposed at Guadalupe Allende (formerly El Pitayo) area, 20-25 km SE of Izúcar de Matamoros, Puebla State, which up to now has not been described in detail.

El Pitayo Lithodeme, located in the westernmost sector of the Complex, consists of fine-grained metapelites and metapsammites, quartzites, radiolarites, sericite-chlorite schist and interbedded metabasalts, which together suggest a deep-water depositional basin. Structurally, the sequence has a predominant N-S trending and penetrative axial plane foliation, associated with isoclinal folding, and it is bordered by faults. El Pitayo Lithodeme is overthrusted by blue schists (Casitas Lithodeme) and apparently it is juxtaposed by lateral faults with the eclogitic rocks of the Piaxtla Suite, in the westernmost sector of the Acatlán Complex.

By U-Pb geochronology of detrital zircons from metasediments, a maximal age of middle Cambrian (ca. 513 Ma, major peak age of the younger zircon grains) for the refilling of the “El Pitayo” basin was estimated, with detrital materials from Pan-African (ca. 500-605 Ma) and Grenvillian orogens (ca. 910-1325 Ma). On the other hand, a K-Ar (laser ablation) age of 234 ± 3 Ma was obtained for white micas from metasedimentary rocks, which can be interpreted as the age of low-grade metamorphism, or as a cooling age related to exhumation processes linked to the Late Triassic tectonic event during the break-up of western Pangea. Furthermore, thermobarometric analyses (chlorite geothermometer and pseudosection modelling) suggest that the greenschist facies metamorphism occurred at P-T conditions, for which no quantitative values have been estimated previously for the low-grade metamorphic rocks of the Acatlán Complex.

Thus, the El Pitayo Lithodeme, by its lithology and the structural position between high-pressure Mississippian rocks of the Piaxtla Suite at the westernmost sector the Acatlán Complex, is considered a key unit that with more detailed information will surely allow more robust correlations with other low-grade metamorphic units and will undoubtedly help to better understand about the pre- and post-Pangea tectonic evolution of the Acatlán Complex, southern Mexico.

How to cite: González-Ixta, Y. and Elías-Herrera, M.: Lithodeme El Pitayo, a Palaeozoic meta-volcanosedimentary unit of the Acatlán Complex, southern Mexico and its importance in pre- and post-Pangea tectonic evolution., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-368, https://doi.org/10.5194/egusphere-egu24-368, 2024.

EGU24-879 | Orals | GMPV4.1

Missing seawater in the hydration record of a peridotite massif from mid-ocean ridge to subduction (Monte Maggiore, Alpine Corsica, France) 

Veronica Peverelli, Orlando Sébastien Olivieri, Aratz Beranoaguirre, Enrico Cannaò, Francesco Ressico, Zeudia Pastore, Axel Gerdes, and Alberto Vitale Brovarone

Increasing evidence shows that, even where mid-ocean ridge serpentinization is widespread, significant volumes of fresh mantle are subducted. A part of these rocks may remain dry, or experienced subduction-related serpentinization. Once serpentinites are exhumed after a whole subduction cycle, it is challenging to determine timing and conditions of serpentinization. However, these may be constrained by investigating lithologies that are coupled with serpentinized peridotitic massifs from the mid-ocean ridge stage, such as gabbroic rocks. Here, we focus on variably transformed gabbroic rocks in the Monte Maggiore massif (Alpine Corsica, France). This body formed along a slow-spreading center of the Piemonte-Ligurian Basin in the Jurassic, and was subsequently subducted to blueschist-facies conditions. In the Monte Maggiore massif there is ample evidence for fluid–rock interaction processes. The most evident one is a serpentinization front of the peridotitic units where serpentinization degrees vary from < 10 to 100 %. Weakly serpentinized domains preserve rather fresh brown amphibole-bearing gabbroic rocks with only partial blueschist-facies metamorphic overprint. Instead, intensely serpentinized domains embed metasomatized gabbros such as rodingites.

To constrain timing and conditions of fluid circulation in the Monte Maggiore massif, we applied a multi-methodological approach to characterize the nature of metasomatic fluids and to date the timing of fluid–rock interaction in selected metasomatic and hydrated rocks. Low Cl contents (< 0.009 wt. %) measured by electron probe microanalyzer in late-magmatic brown and green amphibole in a Jurassic Ti-gabbro dike cutting the peridotitic units indicates that, after emplacement of the dike, this gabbro underwent alteration driven by magmatic water. This process was accompanied by titanite crystallization at the expenses of primary ilmenite and is dated at ca. 163 Ma by titanite LA-ICP-MS U–Pb geochronology. However, the formation of the Monte Maggiore serpentinization front recorded by rodingite-forming minerals and grossular-jadeite assemblage in partially re-equilibrated gabbros is dated at ca. 34 Ma and 47 Ma by LA-ICP-MS U–Pb geochronology of garnet.

Our data pinpoint at least two phases of fluid circulation in the Monte Maggiore unit, which span the entire evolution of the ophiolitic massif from rifting to high-pressure metamorphism during the Alpine orogeny. Notably, our geochemical and geochronological data rule out that any of these hydration phases were driven by seawater infiltrating the ocean floor, suggesting that mid-ocean ridge serpentinization contributed to a negligible extent to the overall hydration of the Monte Maggiore ophiolite. Conversely, our data suggest that serpentinization occurred primarily in subduction setting. Considering the role of subduction-derived serpentinization in transferring chemical species (e.g., C–O–H) feeding microbial activity in supra-subduction mantle regions, our evidence bears important implications for our understanding of the deep bio-geochemical cycle.

How to cite: Peverelli, V., Olivieri, O. S., Beranoaguirre, A., Cannaò, E., Ressico, F., Pastore, Z., Gerdes, A., and Vitale Brovarone, A.: Missing seawater in the hydration record of a peridotite massif from mid-ocean ridge to subduction (Monte Maggiore, Alpine Corsica, France), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-879, https://doi.org/10.5194/egusphere-egu24-879, 2024.

The Köli Nappe Complex in the Scandinavian Caledonides of Sweden originated as terranes within the Iapetus Ocean, derived from subduction-related magmatic and basin systems. The Krutfjellet Nappe in Västerbotten, Sweden and the Gasak Nappe in Nordland, Norway are both part of the Upper Kӧli Nappes. Siliclastic, carbonate and volcanic protoliths underwent metamorphism up to amphibolite facies, in places involving extensive migmatisation which is not found in other Kӧli Nappe units. Owing to a lack of previous studies, the exact age and origins of these migmatites is currently unknown. Foliations and early folds in the metasediments are cut by c. 445-434 Ma intrusions [1], followed by a regional metamorphic overprint which is assumed to be Scandian. Monazites and zircons from pelitic migmatites in the Norra Storfjället lens of the Krutfjellet Nappe, and monazites from pelitic schists and gneisses in the Sulitjelma area of the Gasak Nappe were dated in-situ using LA-ICP-MS.

Monazites yield Th-U-Pb concordia ages of between 428-424 Ma. Individual concordant analyses span between 443-416 Ma. The monazites yield a large proportion of discordant analyses which fall on discordia lines at high angles to the concordia curve, interpreted to be due to the presence of initial Pb in the monazites. Lower intercept ages range between 428-416 Ma. These isotopic monazite ages are younger than the majority of EPMA Th-U-total Pb ages obtained for the Krutfjellet Nappe in the same grains [2]. The monazites often have complex zoning patterns in Y and REEs, however this zoning appears to be decoupled from the Th-U-Pb isotopic systems. We suggest that the monazites from the Krutfjellet and Gasak Nappes underwent metamorphism and/or fluid-related alteration at between 428-416 Ma, associated with assembly of the Caledonian orogenic wedge. This may have involved pervasive resetting of older monazites through dissolution-reprecipitation, leading to contamination with initial Pb and decoupling of the Th-U-Pb system from Y and REE zoning. The actual age of migmatisation still remains uncertain.

Zircons yield a spectrum of U-Pb dates which appear to be predominantly detrital. The majority are Mesoproterozoic to earliest Neoproterozoic (1600-900 Ma) and a small number around 600-550 Ma. A significant proportion of dates are discordant. These discordant dates often occur in grains which have a spongey, mottled appearance, indicating that the zircons have also experienced some alteration (metamictisation?). Lower discordia intercepts are poorly constrained, but appear to be Ordovician to Silurian. A zircon included in kyanite produced a single concordant date of 440 Ma, which matches the age for nearby earliest-Silurian intrusions [1]. On the basis of this so-far limited zircon dataset we tentatively propose that these rocks underwent migmatisation at c. 440 Ma, perhaps associated with enhanced heat flow from rift-related magmatism, but the monazite age record has been severely overprinted during subsequent Scandian orogenic wedge assembly and translation and its associated lower-grade metamorphism.

Funded by the National Science Centre (Poland) grants no. 2021/41/N/ST10/04298 and 2021/41/B/ST10/03679.

[1] Stephens, M.B. 2020. GSL Memoirs, 50, 549–575.

[2] Carter, I. S. M., Cuthbert, S. & Walczak, K. 2023. EGU Gen. Assem.

How to cite: Carter, I., Cuthbert, S., and Walczak, K.: Enigmatic migmatites from the North Scandinavian Caledonides: Unpicking the metamorphic history of the Upper Kӧli Nappes using in-situ (Th)-U-Pb dating of monazite and zircon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-968, https://doi.org/10.5194/egusphere-egu24-968, 2024.

EGU24-1263 | ECS | Orals | GMPV4.1

Anisotropic host-inclusion systems: the role of symmetry breaking strains 

Mara Murri, Joseph P. Gonzalez, Mattia L. Mazzucchelli, Mauro Prencipe, Boriana Mihailova, Ross J. Angel, and Matteo Alvaro

Mineral host-inclusion systems can retain crucial information regarding their geologic history. For example, we can determine their formation conditions in terms of pressure (P) and temperature (T) from elastic geobarometry. In particular, it is possible to determine the strain acting on the inclusion when still entrapped in its host by measuring changes in the Raman-peak positions with respect to those of a free crystal, which are interpreted through the inclusion phonon-mode Grüneisen tensors (Grüneisen 1926).  The calculated inclusion strains can then be used in an elastic model to calculate the pressure and temperature conditions of entrapment. A simple case is when an anisotropic crystal is contained within a quasi-isotropic host, such as quartz in garnet. When this host-inclusion system is subjected to changes in P and T the host crystal will impose a uniform strain on the inclusion, which will in turn develop deviatoric stresses. In this scenario the symmetry of the inclusion mineral is preserved and the strains in the inclusion can be measured via Raman spectroscopy using the phonon-mode Grüneisen tensor approach.

             However, a more complex situation arises when the host-inclusion system is fully anisotropic, Such as when a quartz inclusion is entrapped in a zircon host, because symmetry breaking of the inclusion occurs as P and T change. In this case, the effect of symmetry breaking on the frequencies of phonon modes is not known and may be different from the case of structural phase transitions involving soft modes.

             Therefore, we calculated the expected deformations for a quartz inclusion in a zircon host in multiple orientations and at various geologically relevant P-T conditions. We then performed ab initio Hartee-Fock/Density Functional Theory simulations on α-quartz with the selected range of strains to (i) determine the role of the symmetry breaking strains in a completely anisotropic host-inclusion system and (ii) evaluate the possible application of the phonon-mode Grüneisen tensor when the symmetry is broken. Our results show the changes in the positions of the Raman modes produced by strains that are expected for symmetry broken quartz inclusions in zircon are generally similar to those that would be seen if the quartz inclusions remained truly trigonal in symmetry. Therefore, the Grüneisen components for trigonal alpha quartz can be used for Raman elastic geothermobarometry in anisotropic host-inclusion systems without introducing significant errors.

 Acknowledgements: This work has been partially supported by the PRIN-MUR project “THALES” Prot.2020WPMFE9_003 and the National Science Foundation under Award No. (1952698) to JPG.

References: Grüneisen, E., 1926. Zustand des festen K¨orpers. Handbuch der Physik 1, 1–52.

How to cite: Murri, M., Gonzalez, J. P., Mazzucchelli, M. L., Prencipe, M., Mihailova, B., Angel, R. J., and Alvaro, M.: Anisotropic host-inclusion systems: the role of symmetry breaking strains, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1263, https://doi.org/10.5194/egusphere-egu24-1263, 2024.

Triassic collisional assemblage between the North China Block (NCB) and South China Block (SCB) along the Qinling Orogen still remains controversy in timing and process. As an indicator, collision-type granulite well records textural evidences of orogenic crustal alteration induced by continental collision. Located at the narrowest part of the Qinling Orogen, the Foping gneiss dome exposed pelitic and mafic granulites, migmatite and granitoids, which are critical to understand the Triassic tectonic evolution history of the Qinling Orogen. Representative pelitic granulite, mafic granulite, and pelitic schist samples from the Foping dome were selected to obtain the P-T-t paths to reveal the collision timing and process, through an integrated study of petrography, mineral chemistry, estimation of P/T conditions and U-Pb geochronological dating. Our results indicate that these granulites experienced granulite facies peak metamorphism at 6.2-7.4 kbar/ 805-855 °C and followed by retrograde metamorphism at 3.4-4.7 kbar/ 605-715 °C with characteristic of clockwise P-T paths. The pelitic schist underwent peak and retrograde stages at P/T conditions of 4.9-5.1 kbar/ 590-605 °C and 3.5-3.7 kbar/ 510-520 °C, respectively, and consisting clockwise P-T paths. Zircon U-Pb dating gives an inherited age of ca.580-573 Ma, which indicates the protoliths of the Foping granulites probably derived from Neoproterozoic. In addition, it also generates a peak metamorphic age of ca.247-240 Ma, revealing the collision onset of the Qinling Orogen at Early-Middle Triassic. Integrated results of zircon and monazite U-Pb analyzing yield retrograde age at ca.208-198 Ma, constraining the collision termination at Late Triassic. Together with the previous studies in the Qinling-Dabie Orogen, we propose that the collision between the SCB and the NCB occurred in the Qinling Orogen, and it is coeval with the collision time of late Permian-Middle Triassic in the Dabie Orogen, and ends at ca.208-198 Ma. Then the > 70o main clockwise rotation occurred in Jurassic-Cretaceous probably.

How to cite: You, J. and Yang, Z.: Triassic collision of the Qinling Orogen: Evidence from granulite metamorphism of the Foping gneiss dome, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2977, https://doi.org/10.5194/egusphere-egu24-2977, 2024.

This study reports phase relations and U – Th – Pbtotalin-situ monazite geochronology of two-pyroxene granulite and high iron oxide bearing garnet-orthopyroxene granulite from the Karimnagar Granulite Belt, Eastern Dharwar Craton, India. The two-pyroxene granulite samples with granoblastic texture are composed of quartz, plagioclase, orthopyroxene, and clinopyroxene as major mineral phases, and biotite, zircon, ilmenite, and monazite occur as accessory phases. Small anhedral coronal orthopyroxenes surround the clinopyroxene megacryst and inclusions of clinopyroxene occur in orthopyroxene. Locally, biotites overgrow orthopyroxene and clinopyroxene along their rims. Garnet-orthopyroxene granulites are composed of orthopyroxene, garnet, spinel, quartz, plagioclase feldspar, hematite-magnetite, and ilmenite. Small, rounded orthopyroxene inclusions in garnet and anhedral coronal garnets surrounding orthopyroxene were observed. Spinels are hercynitic in composition. Ilmenite and tiny grains of spinel (~30 μm) occur as exsolve phases in magnetite. Magnetite separates spinel from garnet and orthopyroxene. The following metamorphic reactions can be proposed from the mineral assemblage:

  • Cpx megacryst + Pl = metamorphic Opx + Cpx (Two-pyroxene granulite)
  • (a) Opx ± Ilm + Pl → Coronal Grt + Qtz, (b) Al-rich magnetite→ Magnetite + Spinel (Hercynite), Ti-rich magnetite → Magnetite+ Ilmenite  (High iron oxide garnet-orthopyroxene granulite).

The result from petrography, phase equilibria, and thermometry of the two-pyroxene granulite predicts that metamorphic orthopyroxene becomes stable at 0.65 Gpa - 950oC along a cooling path, and biotites overgrow orthopyroxene at 650 oC (0.65 GPa). Similarly, the result from grt-opx granulite implies a cooling path where coronal garnet becomes stable at 800 oC-0.65 Gpa.

The U-Th-Pb analysis of monazite grains in pyroxene (38 analysis) and feldspar (25 analysis) from two-pyroxene granulite shows the oldest and youngest peak at 2635 ± 90 Ma and 2449 ± 44 Ma, respectively. The monazite in pyroxene (46 analysis) and quartz (14 analysis) from garnet-orthopyroxene granulite exhibits the oldest peak at 2449 ± 14 Ma and a tiny youngest peak at 1987 ± 29 Ma. Another sample of garnet-orthopyroxene (40 analyses) displays the oldest and youngest peaks at 2574 ± 32 Ma and 2448 ± 25 Ma, respectively.

The late Neoarchean peak at ~2600 Ma retrieved from the pyroxene granulite and high iron oxide bearing garnet-orthopyroxene granulite is probably the protolith emplacement age of granulite, correlated with the accretion of Eastern Dharwar Craton and Bastar Craton as a part of extended Ur assembly. The early Paleoproterozoic peak at ~2450 Ma implies the formation of coronal garnet and metamorphic orthopyroxene during a cooling path.

How to cite: Satpathi, K. and Nasipuri, P.: Phase relations and monazite geochronology of two-pyroxene granulite and high iron oxide bearing garnet-orthopyroxene granulite from Karimnagar Granulite Belt: its importance in Neoarchean-Paleoproterozoic metamorphism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3113, https://doi.org/10.5194/egusphere-egu24-3113, 2024.

EGU24-4159 | Posters on site | GMPV4.1

Significance of high-grade metamorphic events in the Tuareg Shield and its implication for evolution of the Columbia Supercontinent 

Delphine Bosch, Olivier Bruguier, Renaud Caby, Vincent Monchal, and Héloïse Pinon

Using innovative methodological developments applied to the geosciences, such as "split-stream" LASS-HR-MC-ICP-MS technique, we present new geochemical results focusing on high-grade granulite facies rocks from the Iforas Granulitic Unit (IGU, Hoggar Mountains, NE Mali). This unit represents a high grade metamorphic terrane that has been only poorly studied yet. The aim of this study is to understand how granulites provide information on crustal growth processes and, in the context of the IGU, to test whether the processes identified can be integrated into global geodynamic reconstructions during the Palaeoproterozoic. Granulites can contain various U-Pb datable minerals such as zircon, monazite, rutile or apatite. These minerals record, to varying degrees (influence of temperature and/or fluids, nature of the protolith), the events that the granulites have undergone. From a global point of view, the main results of this study show that the major events recorded within the IGU have affected this unit uniformly. Five major events were identified on the basis of the nine rocks studied in detail, and correspond respectively to the following periods: c. 2.06-1.99 Ga, c. 1.95-1.96 Ga, c. 1.86-1.90 Ga, c. 1.76 Ga and c. 1.70 Ga. Present results suggest that the basement is mostly formed by leptynite and orthogneiss of Late Rhyacian age at c. 2.05 Ga. This basement was affected by two major phases corresponding to two successive but distinct granulite facies events at c. 2.0 Ga and c. 1.90 Ga. The first high-grade event is followed by an exhumation event concomitant to erosional processes and sedimentary deposition. The second high-grade metamorphic event occurred at c. 1.90 Ga and is contemporaneous to gabbonoritic magma intrusion. A retrograde amphibolite/greenschist facies metamorphism followed at 1.76-1.78 Ga. This study also highlighted the influence of fluid phases in granulitic rocks and their potential importance in supercontinent break-up. The thermal evolution of the IGU ended with cooling until c. 1.7 Ga. Finally, the Pan-African event did not affect the U-Pb system of zircon, monazite and especially rutile and apatite in the granulitic rocks studied, suggesting that the IGU represents a preserved segment of Paleoproterozoic granulitic crust.

 

How to cite: Bosch, D., Bruguier, O., Caby, R., Monchal, V., and Pinon, H.: Significance of high-grade metamorphic events in the Tuareg Shield and its implication for evolution of the Columbia Supercontinent, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4159, https://doi.org/10.5194/egusphere-egu24-4159, 2024.

EGU24-4628 | Orals | GMPV4.1

Major- and trace-element zoning in garnet from mylonitic micaschists of NE Sardinia, Italy: implications for garnet growth and P-T history 

Gabriele Cruciani, Dario Fancello, Marcello Franceschelli, and Daniela Rubatto

Major- and trace-element zoning in metamorphic garnet can provide useful insights into the metamorphic evolution of the host rocks, in particular when it is coupled with microstructural investigation and thermodynamic modelling. Mylonitic micaschists along the Posada-Asinara Shear Zone in the Axial Zone of the Sardinia Variscan chain contain garnet porphyroblasts with four distinct growth zones (core, mantle, rim and outer rim). The porphyroblasts, enveloped by the S2 foliation, preserve an internal foliation defined by the orientation of the quartz, occasionally arranged in a sigmoidal pattern, suggesting rotation during growth. A large garnet porphyroblasts was investigated by laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) mapping. The major element compositional variation follows a bell-shaped zoning, with Ca and Mn contents progressively decreasing, and Fe and Mg increasing, from the core (Alm45Grs25 Prp1Sps29) to the outer rim (Alm86Grs3Prp11Sps1). The trace element compositional profiles show a central enrichment area for the heaviest REE (Tm, Yb, Lu), corresponding to the garnet core. Elements with lower atomic number (Er, Ho and Y) show a similar enrichment in the mantle. Elements with even lower atomic numbers (Tb, Gd, Eu and Sm) are depleted in the core and mantle, but their content increases in broad shoulders in the garnet rim. The outer rim of the garnet is depleted in all REE. Trace element mapping also shows an annular enrichment zone in Y, Sc, Dy, Ho, Er and Tm at the mantle-rim boundary superimposed on the general compositional zoning. The REE distribution in the garnet growth zones reflects continuous growth controlled by diffusion-limited REE uptake. The Y + HREE annular enrichment zone is interpreted as a decrease in growth rate and  represents a short-lived episode in the garnet growth history. The clockwise P-T path, reconstructed by isochemical P–T phase diagrams and refined by the CZGM software (Faryad and Ježek, 2019, Lithos 332-333, 297-295) is divided into two distinct stages. The first, prograde stage is recorded by the compositional variation of garnet core and mantle, while the second stage reflects rim growth during exhumation. The core + mantle and the rim growth are separated by a decrease in garnet growth rate. The last part of the P-T path has been reconstructed from the rock mineral assemblage, which includes staurolite + biotite.

How to cite: Cruciani, G., Fancello, D., Franceschelli, M., and Rubatto, D.: Major- and trace-element zoning in garnet from mylonitic micaschists of NE Sardinia, Italy: implications for garnet growth and P-T history, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4628, https://doi.org/10.5194/egusphere-egu24-4628, 2024.

EGU24-4756 | Posters on site | GMPV4.1

Timing and geodynamical setting of Paleoproterozoic events in the Birrimian of the West African Craton: Insights from the Hounde Greenstone Belt (SW Burkina Faso) 

Olivier Bruguier, Delphine Bosch, Renaud Caby, Lenka Baratoux, and Mark Jessell

This study presents geochemical (major and trace elements, Pb-Sr-Nd isotopes on whole rocks) and geochronological (U-Pb on zircon) analyses on granitoids and volcanics from the Hounde Greenstone Belt (HGB). The HGB is one of the three Greenstone Belts outcropping in the southwestern part of Burkina Faso with, from east to west, the Boromo, Houndé and Banfora Greenstone belts. All three greenstone belts are separated by granitic domains and are mined for gold. In the HGB, the preserved sequence is constituted by a 6 km thick basaltic and gabbroic pile followed upward by intermediate (andesite) to felsic (rhyolite) volcanics with intercalated volcaniclastic and sedimentary material. Fine-grained sediments are more and more abundant upward. The HGB is limited on the East by the N-S Boni shear zone, which controlled deposition of “Tarkwaian-type” detrital sediments (conglomerate, sandstones and phyllites).

Geochemical analyses indicate that the oldest dated plutonic samples (2195 ± 6 and 2183 ± 7 Ma) have a trondhjemitic affinity and metaluminous or peraluminous character. Similar ages at 2172 ± 5 and 2191 ± 5 Ma were also obtained on volcanics (andesite and rhyolite) from within the HGB indicating coeval development of GB and basement rocks. The trondhjemite have geochemical characteristics consistent with magma production in a convergent plate setting and the 2.20 – 2.17 Ga period is interpreted as corresponding to arc build-up and thickening of the arc crust. Cross-cutting leucocratic veins in the trondhjemite indicates partial melting of the arc crust at 2144 ± 6 Ma, which may be related either to a regional metamorphic event or triggered by the gradual thickening of the crustal section. Granites and granodiorites (and their volcanic equivalents) yield younger ages in the range 2132 ± 3 Ma to 2095 ± 9 Ma, and geochemical features typical of volcanic arc granites although the youngest granitoids, in the 2120 – 2100 Ma range, indicate a syn-collisional setting. Nd isotope data show large variations (eNd ranging from +0.7 to +14.5) and a broad general trend of increasing eNd values with decreasing ages. This trend may reflect increasing proportions of juvenile mantle-derived material to the source regions of the younger granitoids. However some samples have significantly older TDM model ages ranging from 2310 to 2430 Ma suggesting the involvement of early Birrimian components that could have been added to the source regions, either by assimilation at lower crustal levels or by sediment subduction.

How to cite: Bruguier, O., Bosch, D., Caby, R., Baratoux, L., and Jessell, M.: Timing and geodynamical setting of Paleoproterozoic events in the Birrimian of the West African Craton: Insights from the Hounde Greenstone Belt (SW Burkina Faso), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4756, https://doi.org/10.5194/egusphere-egu24-4756, 2024.

EGU24-4969 | Orals | GMPV4.1

In-situ garnet Lu-Hf geochronology from the contentious Belomorian high-pressure rocks. 

Martin Hand, Dillon Brown, Stijn Glorie, Xiaofang He, Sarah Gilbert, and Justin Payne

Eclogites are a characteristic product of subduction-driven metamorphism and generally regarded as mineralogical evidence for modern-style plate tectonics. Consequently considerable effort has been expended to determine when eclogite appeared in the geological record, including claims of Archaean-aged eclogite.  One area of such contention is the Belomorian Orogenic Belt in NW Russia.  There are two schools of thought regarding Belomorian high pressure metamorphism.  One is that metamorphism occurred at c. 2.7 Ga, representing potentially the oldest occurrence of eclogite (eg Volodichev et al 2021; Minerals, 11, 1029).  The other view is that high pressure metamorphism occurred at around 2 Ga, forming part of the global set of c. 2.Ga eclogites (eg Yu et al., 2017; Journal of Metamorphic Geology, 35, 855-869). 

A combination of sample-scale X-ray mapping, laser ablation ICPMS and Time-of-Flight mapping has been used to delineate two generations of garnet in a sample from the well-studied Stolbikha Island locality in the Belomorian Belt.  The sample contains voluminous diopside-plagioclase symplectites whose re-integrated composition is consistent with the former presence of pyroxene with Xjd ~ 0.26-0.3. The symplectites overprint hornblende that probably formed during melt crystallisation.  The cores of the older generation garnet are comparatively HREE rich, and give an in-situ laser ablation Lu-Hf age of 2490 ± 40 Ma.  The second generation garnet is comparatively HREE depleted, and gives a Lu-Hf age of 1875 ± 86 Ma.  The comparatively large uncertainties reflect low Lu concentrations in the analysed garnets.  Both generations of garnet preserve partially relaxed major element zoning, and given the apparent diffusivities of major elements relative to Lu and Hf, it is probable both derived ages are meaningful.  An important difference between the two garnet generations is the presence of rutile inclusions in younger garnet and their absence in older garnet.   P-T modelling suggests c. 2.5Ga metamorphism occurred at c. 6-8kbar at temperatures > 750°C. For the younger mineral assemblage, P-T modelling taking into account the presence of the older garnet as well as the inferred clinopyroxene composition, combined with Zr-in rutile thermometry from rutile-qtz-zircon clusters in c. 1875 Ma garnet, gives c. 1.5 GPa and 700°C.   

The results indicate Belomorian Orogen high pressure metamorphism occurred at c.1875 Ma, confirming the conclusions of other workers (eg Yu et al 2017) that high pressure metamorphism is Palaeoproterozoic in age.  However we find no evidence for notably elevated pressures (> 2GPa) for the metamorphism at c. 1875 Ma as suggested by some previous workers, or evidence for high pressure metamorphism at c. 2.7 Ga. The Belomorian high-P rocks belong to the now globally distributed suite that records the emergence of eclogite in the initial stages of Nuna assembly. The general emergence of eclogite in the geological record at around 2 Ga probably reflects a combination of subduction into a cooler mantle and continental processes that facilitated preservation. 

How to cite: Hand, M., Brown, D., Glorie, S., He, X., Gilbert, S., and Payne, J.: In-situ garnet Lu-Hf geochronology from the contentious Belomorian high-pressure rocks., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4969, https://doi.org/10.5194/egusphere-egu24-4969, 2024.

EGU24-5469 | ECS | Orals | GMPV4.1

The behavior of Li and B isotopes in high-T and low-T eclogites enclosed by phengite schists 

Dan Wang, Rolf Romer, Fulai Liu, and Johannes Glodny

Subduction zones are critical sites for recycling of Li and B into the mantle. The way of redistribution of Li and B and their isotopes in subduction settings is debated, and there is a lack of detailed studies on Li and B partitioning between minerals of different types of eclogites and their host rocks. We present Li and B concentration data of minerals and Li and B whole-rock isotope data for low-T and high-T eclogites and their phengite schist host rocks from the Changning–Menglian suture zone, SW China. Omphacite controls the Li budget in both the low-T and high-T eclogites. Low-T eclogites have Li and δ7Li values (8.4–27.0 ppm, –5.5 to +3.2 ‰) similar to their phengite schist host rocks (8.7–27.0 ppm, –3.8 to +3.0 ‰), suggesting that Li was added to low-T eclogites from the phengite schists. In contrast, high-T eclogites have much lower δ7Li values (–13.2 to –5.8 ‰) than the phengite schists, reflecting prograde loss of Li or exchange with wall rocks characterized by low δ7Li values. Phengite and retrograde amphibole/muscovite are the major B hosts for low-T and high-T eclogites, respectively. The budgets and isotopic compositions of B in eclogites are affected by the infiltration of fluids derived from phengite schists, as indicated by eclogite δ11B values (–15.1 to –8.1 ‰) overlapping with the values of the phengite schists (–22.8 to –9.5 ‰). Lithium and B in eclogites are hosted in different mineral phases that may have formed at different stages of metamorphism, implying that the contents and isotopic compositions of Li and B may become decoupled during subduction-related fluid-mediated redistribution. We suggest a mineralogical control on the redistribution of Li and B in eclogites during subduction and the exchange of Li and B with the immediate wall rocks. The observed contrasting Li and B isotopic signatures in eclogites are likely caused by a fluid-mediated exchange with different types of wall rocks during both prograde metamorphism and exhumation.

How to cite: Wang, D., Romer, R., Liu, F., and Glodny, J.: The behavior of Li and B isotopes in high-T and low-T eclogites enclosed by phengite schists, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5469, https://doi.org/10.5194/egusphere-egu24-5469, 2024.

EGU24-5883 | ECS | Posters on site | GMPV4.1

Metamorphic P–T-t path and tectonic implications of the eclogite from Changning–Menglian orogenic belt, southeastern Tibetan Plateau 

Ying Zhou, Hao Cheng, Zhimin Peng, Yuzhen Fu, and Kaiyang Du

Understanding the relationship between ultra-high-pressure (UHP) metamorphic rocks and their surrounding country rocks is crucial for interpreting the tectono-metamorphic dynamics within orogenic belts. This study focuses on the Changning–Menglian orogenic belt in Southeast Tibet to delineate the subduction history of the Paleo-Tethys Ocean. We integrate garnet Sm–Nd and Lu–Hf dating, rutile/zircon U–Pb geochronology, phase equilibria modeling, and thermobarometry to examine high-pressure eclogites and surrounding metasediments. Pseudosection modeling and conventional thermobarometry suggest a clockwise pressure-temperature (P–T) path for the eclogite, from ~1.4 GPa/~505–530 °C to ~2.4–2.8 GPa/~600–640 °C, followed by decompression to <~0.7 GPa. The micaschists reached peak conditions of 2.0–2.2 GPa and 570–620 °C. Lu–Hf dating yields ages of around 236–241 Ma for the eclogites and 249–251 Ma for the micaschists. Sm–Nd dating indicates a similar age range for the eclogites (236–242 Ma) but yields slightly younger ages for the micaschists (~240 Ma). These results imply a brief period of garnet growth in the eclogites, suggested by Rayleigh-fractionation-style Lu zoning and a rimward increase in Sm concentration within garnet. In contrast, the micaschists exhibit a more prolonged garnet growth period of approximately 10 Myr. The comparable peak metamorphic conditions and high-pressure metamorphic ages in both rock types suggest they underwent a concurrent subduction-exhumation cycle. Magmatic zircon U–Pb dating establishes the protolith age of the metabasaltic rocks at ca. 247 Ma. The multi-mineral geochronological data indicate a rapid transition from oceanic divergence to convergence within the orogenic belt around 250 Ma. These findings, along with previous geochronological data on continental subduction, point to a brief ~20 Myr cycle involving the formation, deep burial (exceeding 75 km), and subsequent ascent to the shallow crust of the Paleo-Tethys oceanic rocks. This evidence supports a continuous transition from oceanic to continental subduction within the region.

How to cite: Zhou, Y., Cheng, H., Peng, Z., Fu, Y., and Du, K.: Metamorphic P–T-t path and tectonic implications of the eclogite from Changning–Menglian orogenic belt, southeastern Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5883, https://doi.org/10.5194/egusphere-egu24-5883, 2024.

Corona textures in high-grade metamorphic rocks, characterized by specific mineral assemblages, have been extensively studied, yet their direct dating remains a challenge. In an effort to ascertain the formation time and duration of corona textures, we undertook a comprehensive petrochronological study, utilizing garnet Lu–Hf and Sm-Nd alongside zircon U–Pb dating, on a corona-bearing granulite from the Miyun area in the North China Craton. This region, situated at the intersection of the Archean Eastern Block and the Paleoproterozoic Trans-North China Orogen, provides valuable insights into polymetamorphic processes.

Through pseudosection modeling and conventional thermobarometry, we determined that the corona texture—predominantly garnet, with minor clinopyroxene and quartz—formed at approximately 0.9 GPa and 740 °C. This was followed by retrogression at ~0.5 GPa and 670 °C, leading to the growth of amphibole and biotite. Lu–Hf dating of garnet gave an age of 1864 ± 3 Ma, significantly younger than the metamorphic zircons' U–Pb age of ca. 2454 Ma. This discrepancy suggests a disequilibrium in rare earth elements (REE) between garnet and zircon. Comparative analysis of REE concentrations in zircon and garnet, along with experimental data and lattice strain modeling, indicated that zircons deviated from the equilibrium array, implying their (re)crystallization independent of garnet. The preservation of Lu zoning in garnet suggests that the Lu–Hf date reflects the period of garnet growth, approximating the time of anhydrous corona assembly formation.

The U–Pb zircon age of ca. 2454 Ma indicates an earlier, distinct Archean metamorphic event, which is a common feature in high-grade metamorphic rocks throughout the Eastern Block of the North China Craton. The garnet Sm–Nd dating, yielding an age of 1817 ± 6 Ma, aligns with the amphibole-biotite Lu–Hf date of 1819 ± 16 Ma, indicating a gap of approximately 47 Myr from the garnet Lu–Hf date. This suggests a phase of rapid growth followed by fast cooling. The coinciding ages of garnet Sm–Nd and amphibole-biotite Sm–Nd and Lu–Hf, given their different closure temperatures, point to more than mere cooling, indicating the formation of anhydrous coronae around 1.86 billion years ago, followed by hydrous retrogression ca. 1.82 Ga.

The presence of both Paleoproterozoic and Archean ages in the Miyun granulites correlates with significant tectonic episodes in the Trans-North China Orogen and the Eastern Block, respectively. This correlation suggests that the Miyun region experienced overlapping metamorphic events associated with both these tectonic units. Our approach, integrating Lu–Hf and Sm–Nd dating, is particularly effective for rocks with explicit textures, enabling precise extraction of temporal intervals in metamorphic processes.

How to cite: Du, K., Cheng, H., Dragovic, B., and Cao, C.: Integrated garnet and zircon petrochronology of corona formation in high‐grade rocks from granulite‐facies rocks in the North China Craton, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6042, https://doi.org/10.5194/egusphere-egu24-6042, 2024.

Plate tectonics represents a forefront of research in earth sciences, with the establishment of modern-style plate tectonics remaining one of the key unresolved issues. Debates continue about its initiation, with estimates ranging from the Hadean to the Neoproterozoic or Cambrian periods, spanning nearly Earth's entire history. The North China Craton (NCC), as one of the world's oldest cratons, encapsulates a geological history from 3.8 to 1.8 billion years ago, offering valuable insights into early Earth's evolution. Recent work by Ning et al. (2022) highlighted eclogite-facies garnet clinopyroxenite in the Eastern Hebei terrane of the NCC, dated at over 2.47 billion years, suggesting the presence of modern-style plate tectonics by the end of the Archean era.

To further investigate the timing and metamorphic processes of the garnet clinopyroxenite, we conducted a comprehensive garnet and zircon petrochronological study. The garnet clinopyroxenite is primarily composed of clinopyroxene and garnet, with accessory minerals including plagioclase, quartz, titanite, magnetite, and ilmenite. Garnet compositional profiles show minimal chemical zonation, with a gradual decrease in XPrp (0.27–0.23) from core to rim, indicative of diffusional resorption driven by retrogression. Conventional thermobarometric calculations suggest peak metamorphic conditions between 761–833°C and 1.0–1.1 GPa, not reaching eclogite-facies. Zircon analysis revealed depleted LREE, positive Ce, and negative Eu anomalies, with most zircons indicating a metamorphic age of 2478 ± 12 Ma. A subset of zircons provided a weighted mean 207Pb/206Pb age of 1770 ± 11 Ma, displaying flat HREE patterns potentially coexisting with garnet. U–Pb data suggest the Eastern Hebei terrane's garnet clinopyroxenite records Neoarchean (ca. 2.50 Ga) and Paleoproterozoic (ca. 1.8 Ga) metamorphic ages. However, the diverse range of zircon U–Pb ages and their ambiguous textural associations complicate the correlation of P–T conditions with specific timeframes. Thus, the peak metamorphic conditions of garnet clinopyroxenite, as estimated by conventional thermobarometry, cannot be conclusively dated to either ca. 2.50 Ga or ca. 1.8 Ga. This ambiguity limits the evidence for Archean eclogite-facies metamorphism. Future garnet-whole rock Sm–Nd/Lu–Hf isochron analysis may offer more definitive dating of metamorphic events and enhance understanding of the garnet clinopyroxenite's thermal history.

How to cite: Yang, R. and Cheng, H.: Garnet and zircon petrochronological study of the garnet clinopyroxenite from Eastern Hebei terrane,North China Craton——no evidence for Archean eclogite-facies metamorphism?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7780, https://doi.org/10.5194/egusphere-egu24-7780, 2024.

EGU24-9315 | ECS | Posters on site | GMPV4.1

Crustal transtension and associated high-T/low-P metamorphism in the North Tianshan Arc, NW China 

Xinghua Ni, Bo Wang, Mathieu Soret, Dominique Cluzel, Yan Chen, Jiashuo Liu, and Michel Faure

Crustal evolution of the North Tianshan during the late Paleozoic remains controversial due to the lack of structural and metamorphic constraints. We present new structural, petrological and geochronological data of the Xiaopu metamorphic complex (XMC) to address this issue. The XMC shows a well-preserved Buchan-type metamorphic sequence made of garnet, andalusite-staurolite and sillimanite zones. Structural observations indicate that garnet, sillimanite, andalusite and staurolite grew syn-kinematically during a transtensional event (D2). Inclusion trails in garnet cores oriented at high angle with the external foliation probably record an earlier deformation stage (D1). Synchronous ductile normal faults and thrusts (D3) overprinted previous structures and control the exhumation of the metamorphic complex. LA-ICP-MS zircon U-Pb ages of pre-D2 gneissic granodiorite, syn-D2 granitic dikes and post-D2 diorites constrain the occurrence of D2 between 332 and 305 Ma. Apatite U-Pb ages of mylonitic rocks from the ductile fault indicate that D3 occurred at ~285 Ma. Phase modelling and geothermobarometers were used to estimate the pressure-temperature (P-T) conditions of the XMC. Peak conditions show progressive temperature increase from andalusite-staurolite schists (~580 °C) to sillimanite migmatites (~680 °C) at nearly constant pressure (~4 kbar), suggesting a significant thermal effect of nearby large intrusive bodies. The schists display a pre-peak heating with slight decompression and the migmatites show retrograde cooling and decompression to ~600 °C and ~3 kbar. Their P-T paths and high/T and low/P thermal regimes are in line with an extensional setting. Monazite U/Th-Pb ages of 313-311 Ma for sillimanite-bearing schists and migmatites suggest monazite growth during the retrogression. 40Ar/39Ar ages of mica from sillimanite schists are in the range of 298-275 Ma, consistent with a later cooling and exhumation associated with D3. These data reveal the crustal transtension during the middle to late Carboniferous (~330-310 Ma) and cooling and exhumation during the early Permian (~285 Ma) of the North Tianshan arc. Such transtensional tectonics probably facilitated decompression melting of the lower crust and lithospheric mantle of the arc. Subsequent ascent and emplacement of the resulting melt could yield high thermal gradient, produce partial melting of the mid-crustal rocks and promote crustal exhumation. 

How to cite: Ni, X., Wang, B., Soret, M., Cluzel, D., Chen, Y., Liu, J., and Faure, M.: Crustal transtension and associated high-T/low-P metamorphism in the North Tianshan Arc, NW China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9315, https://doi.org/10.5194/egusphere-egu24-9315, 2024.

Eclogites have provided important constraints on the processes of plate subduction, collision and the overall tectonic evolution of orogens. The Gubaoquan eclogite is the only one identified in the Beishan Orogenic Belt, which constitutes the southernmost part of the Central Asian Orogenic Belt. The protolith age and tectonic setting of the eclogite and associated rock units remain ill-constrained. U–Pb dating of the eclogite indicates a Neoproterozoic age of 887 ± 7 Ma for its protolith age and an Ordovician age of 461 ± 15 Ma for the eclogite facies metamorphism. Detailed U-Pb ages of zircons, monazites, rutiles and apatites from the eclogite and country rocks suggest that they have experienced multiple metamorphic events in the Neoproterozoic and Paleozoic, which are inferred to correlate with retrograde metamorphism during the later exhumation. The protoliths of the Gubaoquan eclogite are of continental origin, and along with the extensive distribution of the Neoproterozoic arc-related rocks probably resulted from assembly of Rodinia. This work was financially supported by the National Natural Science Foundation of China (41730213 and 41890831), Hong Kong RGC GRF grants (17307918), HKU Internal Grants for Member of Chinese Academy of Sciences (102009906) and for Distinguished Research Achievement Award (102010100), Northwest University Excellent Doctoral Thesis Cultivation Program (YB2023003), and from the Australian Research Council (FL160100168).

How to cite: Wang, T., Cawood, P. A., Diwu, C., and Zhao, G.: Neoproterozoic-Early Paleozoic evolution of the southern Central Asian Orogenic Belt: constraints from eclogites in the Beishan Orogenic Belt (NW China), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9385, https://doi.org/10.5194/egusphere-egu24-9385, 2024.

EGU24-9918 | ECS | Posters on site | GMPV4.1

Early Mesozoic magma-induced mid-crustal flow and high-temperature metamorphism in the Yunkai massif, South China 

Jiashuo Liu, Bo Wang, Bryan Cochelin, Shenghua Lu, Liangshu Shu, Charles Gumiaux, Yan Chen, Hugues Raimbourg, Michel Faure, and Xinghua Ni

Early Mesozoic evolution and geodynamic processes of the South China Block remain controversial and its rheology is not well understood. The granites and migmatites exposed in the Yunkai massif preserve important records of middle crust mechanical behavior during Indosinian orogeny. They show a significant strength decreasing of the crust during this period, further affecting the rheological behavior of the entire lithosphere in South China. In order to better understand the Early Mesozoic evolution and geodynamic processes of the South China Block, we conducted detailed studies on structural geology, multi-minerals geochronology and P-T estimate on Mesozoic migmatites and granitoids in the Yunkai massif. Three tectonic/metamorphic events are identified. The main one corresponds to the development of a regional NE-SW extension. It constitutes a dome-like structure with amphibolite-facies metamorphism during 243–237 Ma (D1), followed by a rapid cooling to ~300 °C within ~20 Ma. Conventional mineral thermobarometers constrain the D1 metamorphism at 665–692 °C and 6.1–6.2 kbar, indicating an upper amphibolite – granulite facies metamorphism. Based on the phase equilibrium modelling, the grossular component (XGrs=0.12–0.13) in the garnet core, Ti content (XTi=0.15–0.17) of biotite and An value (An=0.84–0.86) of plagioclase in the matrix define a peak P–T condition at 780–810 °C and 6.8–7.0 kbar within the stability field of the observed assemblage, indicating a mid-crustal high-temperature metamorphism. Combined with the field structural relationships, geochemical similarity and inherited zircons, the protoliths of the D1 amphibolite-facies metamorphism are of Silurian (<427 Ma) greywacke and magmatic rocks. Due to the strong reworking during the Early Mesozoic and only a few of these previous records were preserved in the metamorphic rocks by the zircon cores and several monazites. Thereafter, the D1-deformed granites and migmatites are crosscut by Late Jurassic (~157 Ma) greenschist-facies NE-SW dextral strike-slip faults (D2). Both of the above rock units are reworked by a later local vertical shearing (D3). Combined with published age data, our results documented a late local metamorphism of 10 Ma with respect to the regional magmatism, suggesting a magma-induced high temperature metamorphism. We propose that this magma-induced mid-crustal flow and high-temperature metamorphism are in response to the Indo-China collision and the westward subduction of the Paleo-Pacific Plate. Our new results provide new insights on partial melting and its implications on mid-crust rheological behavior during orogenic processes.

How to cite: Liu, J., Wang, B., Cochelin, B., Lu, S., Shu, L., Gumiaux, C., Chen, Y., Raimbourg, H., Faure, M., and Ni, X.: Early Mesozoic magma-induced mid-crustal flow and high-temperature metamorphism in the Yunkai massif, South China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9918, https://doi.org/10.5194/egusphere-egu24-9918, 2024.

EGU24-10343 | ECS | Posters on site | GMPV4.1

Tectono-metamorphic evolution and crustal-scale shear zone origin in the high-grade crust of southern Madagascar 

Heninjara Narimihamina Rarivoarison, Pavlína Hasalová, Alfred Solofomampiely Andriamamonjy, Tongasoa Miha, Pavla Štípská, Prokop Závada, Jean-Emmanuel Martelat, and Karel Schulmann

In southern Madagascar two main tectono-metamorphic events, corresponding to the East African Orogeny (ca. 630–610 Ma) and the Kuunga Orogeny (ca. 580–515 Ma) were recognized. An early structures include recumbent folds and sub-horizontal foliation S1 that were transposed during a regional east–west shortening resulting into north–south-oriented upright folds, with horizontal axes and new vertical axial planar foliations S2. This second deformation event is coeval with the development of a network of vertical ductile shear zones such as the Ejeda SZ, Ampanihy SZ, Beraketa SZ, Ihosy SZ, Zazafotsy SZ and Tranomaro SZ. These megascale 15–25 km-wide intracrustal near-vertical N-S or NW-SE trending strike-slip ductile shear zones crosscut the entire high-grade metamorphic basement of southern Madagascar and separate lower-strain domains where complex fold interference patterns are visible. These high-strain zones developed between 580 and 530 Ma with a slight diachronism from the west to east and south to north and are coeval with melting and UHT/HT granulite facies conditions. The granulite facies metamorphism is widespread throughout the whole basement in all lithologies, in the southern part reaching peak conditions of 900–1000°C at 6–10 kbar and slightly lower temperature conditions (≤800°C) to the west, north, and in the Ikalamavony fold-thrust belt to the north–northeast. Importantly, the shear zones reveal large fluid/melt transfer from the depth that caused extensive fluid/melt rock interaction (in the shear zone as well as in the surrounding basement) that resulted in localized charnockitisation of the granulites. The melt/fluid flux here was structurally controlled and seems to be penetrative throughout the basement rocks. This offers a unique opportunity to study fluid-assisted pervasive melt migration controlled by localized deformation across the whole crust. In this context, our objective is to investigate the tectonometamorphic changes occurring in the intensely deformed high-grade lower to middle crust located in southern Madagascar. Additionally, we seek to delineate the chronological connection between the deformations and high-temperature metamorphism (U)HT, along with the associated processes of crustal anatexis and magmatism.

How to cite: Rarivoarison, H. N., Hasalová, P., Andriamamonjy, A. S., Miha, T., Štípská, P., Závada, P., Martelat, J.-E., and Schulmann, K.: Tectono-metamorphic evolution and crustal-scale shear zone origin in the high-grade crust of southern Madagascar, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10343, https://doi.org/10.5194/egusphere-egu24-10343, 2024.

EGU24-10898 | ECS | Posters on site | GMPV4.1

LT-HP metamorphic rocks from the Nan River suture zone, Thailand 

Pornchanit Sawasdee, Christoph A. Hauzenberger, and John E. Booth

This petrological study involves a detailed examination of blueschists and other LT-HP metamorphic rocks which were tectonically emplaced within the mafic – ultramafic belt of the Nan River suture zone of northern Thailand. The blueschists do not contain garnet, lawsonite, jadeite or pumpellyite and, therefore, are assigned to the epidote – blueschist subfacies. Associated meta-cherts sometimes contain piemontite or bright blue winchite. Thrust sheets of blueschists interlayered with greenschists occur in two localities: one large outcrop is patchily exposed west of Uttaradit city, the other 135 km to the north along two stream sections on the southern flank of Doi Phuk Sung. In addition, rather rare float samples of garnet – white mica ± blue amphibole gneisses have been found in one of the Doi Phuk Sung stream sections and on three different point bars of the Wa River, ca. 40 km further to the north. These gneisses are given the field term “exotics” as their outcrop is unknown and obviously of higher metamorphic grade than any other rocks exposed in the region. The blueschists contain the mineral assemblage Amp (glaucophane – riebeckite, barroisite – winchite) + Ep + Wm + Chl + Ab + Qz ± Ttn ± Rt ± Zrn. The greenschists are typically composed of Amp (actinolite, barroisite) + Chl + Ep + Ab + Qz +Wm ± Ttn ± Rt ± Hem. The “exotics” fall into three groups based on their mineralogy: (1) Grt – Wm + Ab + Chl + Qz ± Stp ± Ep ± Ttn ± Aln ± Zrn ± Ap; (2) Amp (hornblende) – Grt – Wm + Ab + Chl + Qz ± Stp ± Ep ± Ttn ± Aln ± Zrn ± Ap; and (3) Amp (glaucophane – riebeckite, barroisite, winchite) – Grt – Wm + Ab + Chl + Qz ± Stp ± Ep ± Ttn ± Aln ± Zrn ± Ap. The blueschists and greenschists from both localities show identical history of 3 phases of deformation and relative timing of mineral growth. Evidence of D1, preserved as rootless isoclinal folds of quartz rich seams, was almost entirely destroyed by the development of an intense pervasive schistosity during D2, associated with tight to isoclinal folds. D3 produced a crenulation cleavage with little recrystallisation. The peak P-T conditions of blueschists were estimated by constructing pseudosections, indicating temperatures of approximately 450 to 500 °C and pressures of 0.8 to 1.2 GPa. The exotics preserve direct evidence of gneissic segregation banding and a single deformation event. In many cases amphiboles are visually zoned with green cores and violet – blue rims. This is interpreted to indicate that they originated in the greenschist/amphibolite facies and then passed into the blueschist/eclogite facies. Garnets are generally fractured and fragmented and usually display strong prograde compositional zoning where Xprp and Xalm are increasing, Xgrs and Xsps decreasing from core to rim. Peak P-T conditions were estimated by using the Grt-Amp thermometer and calculated pseudosections with temperatures of approximately 550-600°C and pressures of 0.8 to 1.2 GPa.

How to cite: Sawasdee, P., A. Hauzenberger, C., and E. Booth, J.: LT-HP metamorphic rocks from the Nan River suture zone, Thailand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10898, https://doi.org/10.5194/egusphere-egu24-10898, 2024.

EGU24-11568 | ECS | Orals | GMPV4.1

U-Pb Dating of Apatite in Sanidinite-Facies Pyrometamorphosed Rocks from the Hatrurim Basin, Israel 

Zohar Segall, Yaron Katzir, Yevgeny Vapnik, and Bar Elisha

Apatite, an abundant accessory mineral in igneous and metamorphic rocks, may accommodate appreciable amounts of trace elements including U, Pb and REE and is thus a useful U-Pb geochronometer and tracer of high-temperature metasomatism. Since apatite is susceptible to recrystallization, new growth and fluid-induced chemical changes, a good understating of the U-Pb system closure in apatite at variable geological conditions is required to correctly interpret apatite U-Pb ages. In this research, we delve into the behavior of apatite in marine phosphorites metamorphosed at sanidinite facies conditions to constrain U-Pb systematics in apatite under extreme high-T low-P conditions.

We sampled non-metamorphosed, metamorphosed, and hydrothermally altered marine phosphorites from the Mottled Zone pyrometamorphic complex exposures in the Hatrurim Basin, Israel. Petrographic study of the samples was followed by in -situ measurement of major (EMPA) and trace element compositions and U-Pb dating (LA-ICP-MS) of apatite.

Our results show that during the pyrometamorphic event apatite recrystallized and incorporated carbonate, silica, and sulphate into its crystal lattice. Thermally derived apatite recrystallization resulted in a submillimeter-scale Pb isotopic homogenization, inheritance of common lead of very low 207Pb/206Pb ratio from the U-rich, biogenic apatite precursor, and contemporaneous U-Pb system closure of apatite on a wider scale. The Miocene and Pliocene U-Pb ages of apatite coincide with previously known 40Ar/39Ar and K-Ar ages of the Mottled Zone pyrometamorphic event (Gur et al., 1995). Post-metamorphic interaction of high-T metamorphosed phosphorites with carbonate-, uranyl- and vanadate-rich fluids resulted in U and V enrichment of apatite, as well as redistribution of REE.

The results of our research shed new light on the timing and extent of the Mottled Zone pyrometamorphic event, contribute to understating the behavior of biogenic apatite under extreme high-T, low-P conditions, and exemplify the utilization of apatite in meta-sedimentary rocks for dating thermal events including combustion metamorphism.

How to cite: Segall, Z., Katzir, Y., Vapnik, Y., and Elisha, B.: U-Pb Dating of Apatite in Sanidinite-Facies Pyrometamorphosed Rocks from the Hatrurim Basin, Israel, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11568, https://doi.org/10.5194/egusphere-egu24-11568, 2024.

EGU24-12237 | Orals | GMPV4.1

The effect of modulated deserpentinization on the deep carbon cycle 

Michał Bukała, José A. Padrón-Navarta, Manuel D. Menzel, Károly Hidas, Vicente López Sánchez-Vizcaíno, and Carlos J. Garrido Garrido

Interaction between fluids and different rock types at the subducting slab interface directly influences deep volatile recycling processes. Recent studies [1] suggest that an influx of reduced fluids from graphite-bearing metapelites can promote deserpentinization at lower temperatures and modify the intrinsic redox capacity of the released fluid. Here we report a newly discovered high-pressure deserpentinization front ­– Cerro Pingano (Betic Cordillera, Spain), located 20 km north of the type locality of Cerro del Almirez [1] – where additional observations involving carbonate-bearing chlorite-harzburgites further support the influx of C-bearing fluids concomitantly to deserpentinization. This small body (<0.5 km2) is hosted within a metasedimentary sequence of graphite-bearing mica schists and marbles which together underwent an Alpine high-pressure metamorphism. Antigorite (Atg-)serpentinite (without carbonate) is separated from Chl-harzburgite (enriched in magnesite) through a sharp boundary of chlorite (Chl-)serpentinite that can be traced across a ~50 cm wide reaction front.

Atg-serpentinite shows an S-C fabric with a strong crystallographic preferred orientation (CPO) characterized by [001]Atg perpendicular to the foliation. Although the transformation to Chl-harzburgite is associated with fabric weakening, the low-strain olivine, orthopyroxene, and tremolite show a remarkable distribution of the poles to their (010) perpendicular to the compositional layering. Magnesite [0001] axes are distributed perpendicular to the layering, and petrographic observations indicate textural equilibrium between Ol + Opx + Chl + Tr + Mag. The transformation of Atg-serpentinite to Chl-harzburgite is also associated with a decrease of Fe3+/ΣFe and a measurable increase of C, Na, and K content in bulk chemistry, suggesting an interaction with externally derived fluids.

We tested this hypothesis with thermodynamic modelling of the fluid-rock interaction between the host-rock derived fluids and Atg-serpentinites. Thermodynamic models of graphite-bearing mica schist predict dehydration due to chloritoid and chlorite breakdown, and release of highly reducing CH4 + CO2-bearing fluids. Open-system infiltration models show that host-rock derived fluids could effectively reduce the serpentinite bulk composition, consistently with the observed decrease of Fe3+/ΣFe between Atg-serpentinites and Chl-harzburgites. The infiltration-induced reduction shifts the stability of Chl-harzburgite mineral assemblage to temperatures ~50°C lower than predicted by closed-system models without external fluids input.

While the microstructural record suggests that Chl-harzburgite fabric was inherited from the Atg-serpentinite precursor, the changes in bulk chemistry and redox conditions result from interaction with highly reductive aqueous fluids derived from host graphite-bearing mica schists. Hence, we infer that the record of specific prograde metamorphic reactions may reflect changes in redox conditions, not necessarily associated uniquely with P-T changes. The redox contrast between the reduced fluids and prograde dehydrating serpentinites thus represents a new way to precipitate carbonates that can be further subducted and may devolatilized beyond subarc depths.  

[1] Padrón-Navarta, J.A. et al. (2023) Nat. Geosci.

Research funded by RUSTED project PID2022-136471N-B-C21 & C22 funded by MICIN/ AEI/10.13039/501100011033 and FEDER program, and “Juan de la Cierva” Fellowship JFJC2021-047505-I by MCIN/AEI/10.13039/501100011033 and CSIC (M. Bukała).

How to cite: Bukała, M., Padrón-Navarta, J. A., Menzel, M. D., Hidas, K., Sánchez-Vizcaíno, V. L., and Garrido, C. J. G.: The effect of modulated deserpentinization on the deep carbon cycle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12237, https://doi.org/10.5194/egusphere-egu24-12237, 2024.

EGU24-12609 | ECS | Orals | GMPV4.1

Insights from the Application of Accessory and Major Phase Petrochronology from the Manhattan Schist, NYC 

Adrian Castro, Stephanie Walker, Jay B. Thomas, Steven S. Jaret, Isabella Brunet, and Katherine D. Morin

Accurately constraining the timing and tempo of specific metamorphic events is necessary to constrain the rates of important geodynamic processes, such as burial and exhumation in orogens and devolatilization in subduction zones. Accessory phase petrochronology is a popular tool employed to constrain the age and duration of metamorphic processes, including mineral nucleation and deformation fabric development. While accessory phases can produce robust dates, their thermodynamic data is often poorly constrained, requiring careful petrographic analysis to link dates to the pressure-temperature-deformation histories of metamorphic rocks. The dating of rock-forming minerals, like garnet and plagioclase, is typically more resource intensive than accessory phase petrochronology, but allows for directly linking dates to specific metamorphic events. Here, we consider the results of monazite accessory phase U-Th-Pb chemical dating with that of Sm-Nd dating of garnet from the Manhattan Schist, New York City, to explore how the synthesis of these two methods can be used to constrain robust tectonic histories.

The Manhattan Schist is a Laurentia-derived aluminous pelite historically thought to record polymetamorphism characterized by: 1) upper amphibolite facies metamorphism and anatexis associated with the Taconic Orogeny (~520-470 Ma) and 2) lower grade overprinting during the Acadian orogeny (~416-360 Ma). This interpretation, however, is based on correlation with seemingly similar units elsewhere in New England rather than direct study of the Manhattan Schist, and is called to question by the data presented here.

This work explores three samples, MAT-2017-01a, GWB-03, and CRT-06. All samples are grt-ky-bt-ms migmatites, that record a four-stage metamorphic history: 1) garnet growth starting at ~550°C and 4-6 kbar, 2) burial and heating to kyanite-grade anatexis at 700-750°C and 7-11 kbar, 3) ~1-2 kbar of isothermal exhumation to sillimanite (fibrolite) stability, and 4) continued exhumation to ~700°C and ~6 kbar. Monazite grains in all samples occur both in the matrix and as inclusions in garnet. Metamorphic monazite dates are dominated by a ~465 ±30 Ma (n=15) age consistent with growth during the Taconic Orogeny, with only a single date at ~383 ±25 Ma found in CRT-06. Bulk garnet Sm-Nd dating via TIMS in MAT-2017-01a, however, yields a late Acadian age of ~386 ±3.68 Ma (n=5, MSWD=0.94). The low MSWD coupled with the preservation of major element growth zoning in garnet, suggests that this value represents a single garnet age population reflective of growth at peak or near-peak conditions, entirely during the Acadian orogeny.

Taken as a whole, our results suggest that the Manhattan schist experienced: 1) early greenschist facies metamorphism during the Taconic orogeny recorded in metamorphic monazite, and 2) peak metamorphism associated with collision and burial in the Acadian orogeny recorded in garnet. Additionally, the sample-to-sample heterogeneity in monazite ages within the same lithology suggests that monazite growth is controlled by (sub)cm-scale processes. Therefore, future studies should investigate multiple samples of the same formation, if not the same outcrop, before making tectonic interpretations based on accessory phase petrochronology.

How to cite: Castro, A., Walker, S., Thomas, J. B., Jaret, S. S., Brunet, I., and Morin, K. D.: Insights from the Application of Accessory and Major Phase Petrochronology from the Manhattan Schist, NYC, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12609, https://doi.org/10.5194/egusphere-egu24-12609, 2024.

Temperature predictably controls mineral stability during metamorphism, and exerts first-order influence on rock viscosity during deformation, but the co-evolution of temperature-dependent metamorphic mineralogy and rock rheology is poorly understood. Thermally-controlled metamorphic-mechanical feedbacks must lead to strain localization during plate boundary formation. However, geologic observations from horizontally-forced, newly-destructive, intra-oceanic subduction plate boundaries consistently present a rheological paradox: hot rocks are strong and cold rocks are weak. 

Observations from geo-/thermochronology and metamorphic thermobarometry demonstrate that following a stage of initially slow, forced convergence along a hot plate interface when the slab tip resists downward translation, the lower plate suddenly collapses into the mantle. After this catastrophic collapse, subduction becomes self-sustaining (i.e., slab pull is established), stable, and cold. The physical mechanism triggering collapse is unknown, though geological studies show that collapse occurs contemporaneously with rapid cooling of the nascent plate contact and depression of slab-parallel isotherms, or “refrigeration”. These observations imply that hot rocks are strong (i.e., viscously sticky), and cold rocks are weak (i.e., viscously lubricating). It is puzzling why the resistance phase would be characterized by the highest temperature metamorphism, since high-temperature rocks are commonly viscously weak; furthermore, plate boundary “unzipping” and lithosphere-scale localization only occur during the rapid refrigeration phase, when rocks should, to a first order, be stiffer and less deformable. What mechanism(s) overcome stiffening, such that a temperature decrease leads to rock weakening, strain localization, and successful subduction initiation? 

Here, we compare microstructures from metamorphic rocks that formed along ancient hot, warm, and cold plate interfaces that correspond to different stages in the evolution of subduction zone formation from initiation to self-sustaining. We conclude that refrigeration drives changes in metamorphic mineral stability, distributions of strain-accommodating minerals, fluid content, and deformation mechanisms, which together dramatically weaken the developing plate boundary. We use flow laws and paleopiezometry to bracket ductile rock strength and demonstrate that cooling at the time of inferred slab collapse causes a minimum 3 order of magnitude viscosity reduction from ~1021 to 1018 Pa-s—the most drastic change in viscosity over a subduction zone’s lifetime. The viscosity reduction leads to a series of dynamic feedbacks, namely: interface decoupling and accelerated plate rates; increased and sustained interface cooling; and stabilization of a wetter, weaker interface. Our ‘refrigeration weakening’ hypothesis embodies a coupled metamorphic-mechanical process that is inherent to the evolution of common oceanic crust, and successfully explains observed changes in upper plate stress state, inferred slab velocity, and timing of proto-forearc seafloor spreading. If true, this mechanism motivates several new testable hypotheses regarding the dynamics of subduction zone development as a function of temperature changes in the modern Earth and throughout Earth’s history.  

How to cite: Kotowski, A., Seyler, C., and Kirkpatrick, J.: From hot and strong to cold and weak: How ‘Refrigeration Weakening’ facilitates strain localization during subduction initiation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12666, https://doi.org/10.5194/egusphere-egu24-12666, 2024.

EGU24-14650 | ECS | Posters on site | GMPV4.1

In-situ LA-ICP-MS U-Pb dating of lower greenschist facies xenotime 

M. Sophie Hollinetz, Christopher R. M. McFarlane, David A. Schneider, Benjamin Huet, and Bernhard Grasemann

Xenotime, a common accessory mineral in metasedimentary rocks, is reactive during metamorphism and can incorporate significant amounts of uranium, making it a promising target for in-situ U-Pb geochonology. However, small grain sizes and cryptic mineral zoning limit the applicability of this tool in low-grade metamorphic rocks thus far. Herein we present results from the dating of two low-grade metamorphic samples collected in the Tirolic-Noric Nappe System at the southern base of Dachstein and Hochschwab massifs (Eastern Alps, Austria). These weakly metamorphosed metasediments, in which sedimentary structures are preserved, underwent metamorphism during the Cretaceous Eo-Alpine event, resulting in a mineral assemblage consisting of chloritoid + pyrophyllite + muscovite + hematite + rutile + quartz that infers P-T conditions of ~350°C and 0.2-0.6 GPa.

Both samples contain accessory xenotime grains that typically range from 10 to 30 µm in diameter. SEM imaging and chemical mapping reveal systematic chemical zoning of most xenotime grains with a heterogeneous core and a distinct, 5-10 µm wide rim that is enriched in MREEs (Sm-Gd). We targeted each chemical domain of xenotime by in-situ LA-ICPMS U-Pb dating using a 5 µm beam diameter. In addition to U and Pb isotopes, Gd and Y concentrations were monitored. The majority of concordant U-Pb dates in both samples range between 632 and 250 Ma. These analyses exhibit low Gd/Y ratios consistent with the xenotime core composition and are therefore interpreted as an inherited population. Both samples exhibit a younger age cluster characterized by high Gd/Y ratios, corresponding to the MREE-rich xenotime rim. In the Hochschwab sample, the youngest cluster yields a concordia age of 134.2 ± 4.0 Ma (MSWD: 2.7, n: 7). Host-inclusion relationships of chloritoid and xenotime suggest coeval growth of the MREE-rich xenotime rim and chloritoid porphyroblasts, linking the U-Pb date to the growth of the main metamorphic assemblage. In the Dachstein sample, the youngest cluster yields a concordia age of 92.4 ± 1.5 Ma (MSWD: 2.9, n: 9). Xenotime and chloritoid are not observed in direct contact, and this sample is characterized by a pervasive crenulation cleavage, which postdates chloritoid growth. From the distribution and morphology of xenotime we conclude that dissolution-precipitation related to crenulation cleavage formation facilitated growth of the MREE-rich rim.

Our results suggest that several stages of xenotime precipitation occurred during protracted or multistage tectono-metamorphic activity in the Tirolic-Noric Nappe System during the Eo-Alpine metamorphic evolution, which is also corroborated by published geochronological data in the same unit. We also demonstrate that the constantly improving spatial resolution of LA-ICP-MS systems allows successful in-situ dating of minute xenotime growth zones, thus providing great potential to improve our understanding of processes during low-grade metamorphism.

How to cite: Hollinetz, M. S., McFarlane, C. R. M., Schneider, D. A., Huet, B., and Grasemann, B.: In-situ LA-ICP-MS U-Pb dating of lower greenschist facies xenotime, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14650, https://doi.org/10.5194/egusphere-egu24-14650, 2024.

EGU24-15106 | ECS | Posters on site | GMPV4.1

In situ high-temperature Raman spectroscopy for the thermal decomposition of Mn2+- and Fe2+-bearing talc 

Stylianos Aspiotis, Lennard Stoeck, Jochen Schlüter, and Boriana Mihailova

Talc (nominally Mg3Si4O10OH2) is a Mg-dominant trioctahedral layered silicate with empty interlayer space that can accommodate minor quantities of Fe2+ and Mn2+ at the octahedral sites, replacing Mg. Given that talc is a common hydrous silicate mineral, containing up to 5.5 weight percent of H2O and commonly occurring under a variety of geological conditions, it can contribute to the volatile cycling in the vicinity of subduction zones. Therefore, the deeper understanding of the temperature-induced talc breakdown into Mg-rich pyroxene and the role of Fe and Mn in the crystal structure of talc during its structural collapse can provide valuable information in several fields of Geosciences such as metamorphic petrology, geophysics, and environmental sciences. Moreover, the information from the dehydroxylation and thermal decomposition of talc can be applied beyond Geosciences; in particular, to understand the weathering processes and firing conditions of soapstone-based cultural-heritage objects. Moreover, the high-temperature atomic dynamics of Fe2+-bearing hydrous silicates with strong structural anisotropy, as probed by Raman spectroscopy,  can shed light on the thermal activation of charge carriers (delocalized H+ and e-) and hence, on conductivity anomalies in the lithosphere (Bernardini et al., 2023).

In this study, we present the results of the thermally-induced changes in Fe2+- and Mn2+-containing talc in the temperature range of 100-1400 K by considering the framework (15-1215 cm-1) and OH-stretching vibrations (3400-3800 cm-1). For this purpose, two samples from Tyrol in Austria were examined, whose exact chemical formulas, particularly (Mg2.93Fe2+0.08Ni0.01Si4.04OH1.81O0.19) and (Mg2.95Mn2+0.07Fe2+0.01Si4.06OH1.69O0.31), were determined by wavelength-dispersive electron microprobe analysis (Aspiotis et al., 2023). We show that structural transformations at an atomic-scale level occur at different temperatures for the Fe2+- and Mn2+-containing talc samples, as the Raman peak position of the TO4 stretching vibration at ~1050 cm-1 starts deviating from the linear dependence with elevated temperatures at 1250 and 1150 K, respectively. In addition, the in situ Raman heating/cooling experiments demonstrate that the OH-stretching mode at ~ 3660 cm-1 associated with a MgMgFe2+ or MgMgMn2+ local configuration vanishes at 1250K for both talc crystals but recovers when cooling down to room temperature, whereas the OH-stretching vibration at 3675 cm-1 related to a MgMgMg triplet can still be identified at least at 1350 K. This reveals that reversible oxidation processes are related to Mn2+-bearing hydrous minerals besides those containing Fe2+. The complete irreversible thermal decomposition of talc occurs at 1400 K, where clinoenstatite is formed.

 

References

S. Aspiotis, J. Schlüter, F. Hildebrandt, B. Mihailova, J. Raman Spectrosc. 2023; 54, 1502.

S. Bernardini, G. Della Ventura, J. Schlüter, B. Mihailova, Geochem. 2023, 83, 125942.

How to cite: Aspiotis, S., Stoeck, L., Schlüter, J., and Mihailova, B.: In situ high-temperature Raman spectroscopy for the thermal decomposition of Mn2+- and Fe2+-bearing talc, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15106, https://doi.org/10.5194/egusphere-egu24-15106, 2024.

EGU24-15425 | ECS | Orals | GMPV4.1

P–T–t constraints on the Inthanon metamorphic core complex and implications for the evolution of the Western Gneiss Belt, northern Thailand 

Srett Santitharangkun, Christoph A. Hauzenberger, Etienne Skrzypek, Daniela Gallhofer, and Harald Fritz

The Inthanon metamorphic core complex in northern Thailand comprises gneisses, schists, migmatites and calc-silicates which are intruded by a variety of granitoids of different age. New P-T estimates, U-Th-Pb total age and U-Pb age data of monazite indicate a multi stage history of the core complex.

Garnet mica-schists and gneisses are exposed in the western part of the Inthanon metamorphic core complex. Garnets show two episodes of growth, with some displaying garnet breakdown and corona formation containing plagioclase, quartz, biotite, and muscovite. The garnet core (grt1) records medium to high-grade metamorphism in the Late Triassic to the Early Jurassic. The second garnet growth (grt2) can be distinguished by a significantly lower Ca content and formed during a high-grade metamorphic event in the Late Cretaceous. Both garnet generations contain abundant inclusions of biotite, muscovite, and monazite, which are used for the reconstruction of the P-T-t history. The monazite included in grt1 yields an age of ~230 Ma. Metamorphic conditions during the first episode of garnet crystallization are 0.7–0.8 GPa at 530–570 °C. The second garnet growth occurred in the upper amphibolite facies at pressures of 0.4–0.5 GPa and temperatures of 640–670 °C. The monazite inclusions in grt2 and monazite within the garnet coronae yield an age of about 80 Ma. The monazite in the matrix, which exhibits complex chemical zoning indicative of recrystallization and re-precipitation during multiple stages of metamorphism, yields a main population at 230 Ma and a typical lead loss trend to a few clusters of 80 Ma dates.

Orthogneiss domains are characterized by a mylonitic texture with large K-feldspar augen and porphyroclasts surrounded by a fine-grained, foliated matrix of quartz and feldspar. This domain is mainly exposed in the core zone of the Inthanon complex and tends to become more mylonitic towards the east. Temperature conditions of 650–700 °C and 0.4 to 0.7 GPa were calculated by pseudosection modelling and using the Ti-in biotite-geothermometer. The monazite texture from the orthogneiss domain displays patchy zoning indicative of several resorptions and reprecipitations. The monazite exhibits an older age range of 230–210 Ma, with younger clusters yielding ca. 75 Ma, and shows a lead loss trend to ca. 30 Ma. The orthogneiss domain is extensively injected by concordant foliated biotite-garnet leucogranite with a monazite U-Pb age around 40 Ma. This age is considered as the upper age limit for the early stages of ductile shearing in the core complex.

Our data indicate that the Western Gneiss Belt in Thailand underwent several tectono-metamorphic events: (1) a medium P-T regional metamorphic phase in the Late Triassic to the Early Jurassic related to Sukhothai-Sibumasu collision (~200 Ma), followed by (2) a widespread younger overprint at upper amphibolite facies in the Late Cretaceous connected with local plutonic activity 75‑65 Ma. (3) Local Late Eocene–Oligocene magmatism and Chiang Mai basin development within deformation zones led to the emplacement of orthogneisses and local metamorphic overprint as seen e.g. in the Mae Ping and Three Pagoda shear zones.

How to cite: Santitharangkun, S., Hauzenberger, C. A., Skrzypek, E., Gallhofer, D., and Fritz, H.: P–T–t constraints on the Inthanon metamorphic core complex and implications for the evolution of the Western Gneiss Belt, northern Thailand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15425, https://doi.org/10.5194/egusphere-egu24-15425, 2024.

EGU24-16362 | ECS | Orals | GMPV4.1

Interpreted 11-6 Ma age of Retrograde Metamorphism in the subduction channel of the Yuli Belt, Taiwan 

Chi-Hsiu Pang, Meng-Wan Yeh, Jian-Cheng Lee, and Yoshiyuki Iizuka

Based on petrological and geochronological studies of glaucophane-bearing schist in the Cenozoic Yuli metamorphic belt, Taiwan, as one of the world's youngest high-pressure (HP) terrane, we provide insights on the metamorphic ages, the metamorphic stages/microstructural fabrics, and the exhumation mechanisms of HP rocks.

In this study we conducted field surveys of well-preserved mesoscale amphibole facies ultramafic schist outcrops along the Mayuan River, located in the Juisui area. We also carried out microstructural analysis using a microscope and SEM-EDS on oriented thin sections to distinguish different deformation stages/fabrics, along with quantitative EPMA analysis of the chemical composition of amphibole and phengite mineral. Furthermore, two different grain sizes (0.18mm and 0.25mm) of phengite were used to conduct the 40Ar/39Ar step heating dating analysis to determine the metamorphic age.

Field observation identify S2 as the main foliation, shallowly dipping to the northwest or northeast in the Mayuan River area. The amphibole schist represents the rim of the ultramafic blocks within the matrix of the albite-quartz-mica schist. We also find a right-lateral west dipping shearing fault zone occurred between these two schists.

By adopting main Phengite fabrics as S2, in microstructure domain, the prograde to retrograde metamorphism (subduction to exhumation) of 5 stages were identified: 1) S2-1, defined by rotated stubby subhedral phengite; 2) S2, defined by Phengite ± Epidote ± Calcic-amphibole; 3) S2+1, defined by Phengite ± Epidote ± Calcic-amphibole ± Chlorite; 4) S2+2, defined by Phengite ± Calcic-amphibole ± Titanite ± Albite; 5) and post-S2+2 phengite. The amphibole revealed varied zoned compositions and evidence of both “clockwise” (high-T to low-T) and “counterclockwise” (high-T low-P to high-P low-T) metamorphism from core to rim: from Pargasite to Edenite/Mg-Hb to Actinolite, Glaucophane to Winchite to Actinolite, and Pargasite to Winchite to Actinolite. Phengite grow in every 5 stages, and the 40Ar/39Ar dating yielded plateau ages of 10.7±1.6 Ma, 10.4±0.5 Ma, 8.8±0.6 Ma, 8.9±1.9 Ma, and 11.0±0.7 Ma, indicating cooling ages after the subduction stage with an estimated closure temperature of 410-420°C. One age spectrum showed a minimum age of 6.1 Ma, possibly representing a recrystallized age during exhumation.

This study reveals the P-T-t path of the amphibole schists in the rim of ultramafic rocks in the subduction channel from subduction to exhumation. The clockwise and counterclockwise P-T path of the zoned amphibole indicated the complicated exhumation mechanism, and the retrograde metamorphism occurred in 11~6 Ma.

How to cite: Pang, C.-H., Yeh, M.-W., Lee, J.-C., and Iizuka, Y.: Interpreted 11-6 Ma age of Retrograde Metamorphism in the subduction channel of the Yuli Belt, Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16362, https://doi.org/10.5194/egusphere-egu24-16362, 2024.

EGU24-16493 | ECS | Orals | GMPV4.1

Reconstructing the nature of the metamorphic basement in the Cyclades, Greece, by the isotopic signature of hydrothermal minerals 

Sandra Wind, David Schneider, Mark Hannington, Simon Hector, and Clifford Patten

In complex continental back-arc settings, such as the Cycladic realm of southeast Greece, polymetallic mineralization can provide information about past tectonic events and help to reconstruct the architecture of the metamorphic basement. In the Cyclades archipelago, slab rollback generated Miocene crustal extension and the formation of metamorphic core complexes, where hydrothermal systems occurring in the upper crust track one of the latest events in the geodynamic evolution. Lead isotope ratios of galena (PbS) and Sr isotope ratios of barite (BaSO4) of the polymetallic ore deposits, which are exposed on most of the islands, reveal two distinct sources of lead and strontium in the underlying basement of the core complexes. A clear division exists between 206Pb/204Pb≤18.84 and 87Sr/86Sr≥0.711 in the north-central Cyclades and 206Pb/204Pb≥18.84 and 87Sr/86Sr≤0.711 in the west Cyclades. This regional pattern corresponds with the exposures of the high-pressure/low-temperature Upper and Lower Cycladic Blueschist nappes on the islands, respectively. Moreover, the pattern follows the surface trace of the proposed synorogenic Trans-Cycladic Thrust, a subduction-related structure that imbricated the high-pressure units. In addition, the isotopic composition of the hydrothermal minerals indicate that the structurally lower Cycladic Basement has a stronger influence on the metal sources of deposits occurring in the hanging wall of the Trans-Cycladic Thrust than in the footwall. Observations featuring the isotopic signature of hydrothermal minerals are complemented by a compilation of new and published isotopic and geochemical whole-rock data of the basement rock types. This allows us to further interpret the geodynamic significance of the apparent heterogeneities in the exposed rocks of the metamorphic core complexes and correlate the scattered exposures of the metamorphic basement. Furthermore, regional patterns in the isotopic and geochemical signature of the basement lithologies help to reconstruct the nature of the continental margin prior to Cretaceous-Eocene subduction.

How to cite: Wind, S., Schneider, D., Hannington, M., Hector, S., and Patten, C.: Reconstructing the nature of the metamorphic basement in the Cyclades, Greece, by the isotopic signature of hydrothermal minerals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16493, https://doi.org/10.5194/egusphere-egu24-16493, 2024.

EGU24-17461 | ECS | Orals | GMPV4.1

Garnet growth in a geological blink of an eye: evidence from high-precision Lu-Hf chronology 

Lorraine Tual, Matthijs A. Smit, Jamie A. Cutts, Kira Musiyachenko, Ellen Kooijman, Jaroslaw Majka, and Ian Foulds

Mineral reactions determine rocks' physical and rheological properties, but whether these reactions occur close to or far from equilibrium, and whether they are continuous or pulsed, is generally unclear. Garnet, the Rosetta Stone of metamorphic processes, presents an unparalleled potential to track the timing and rate of such reaction sequences often recorded and preserved in its growth zones. Here, we used a combination of major and trace-element mapping of garnet to identify single growth zones linked to specific mineral reactions. We extracted each zone by laser microsampling to perform high-precision Lu-Hf chronology and investigate whether and to what extent garnet keeps up with tectonic processes. The analyses were done on a single 1.3 cm-sized garnet grain from a mica schist from the Schneeberg Complex, Italy. The garnet grain was chemically characterised by major- and trace-element mapping (EPMA, LA-ICPMS), and five compositionally distinct micro-domains were extracted using a laser mill. Each single zone was divided into multiple garnet aliquots to enable multi-point isochrons. The four inner zones, corresponding to ~ 85% of the total garnet volume, yielded identical ages with a weighted mean of 98.4 ± 0.1 Ma (2σ). The outermost zone shows a strong chemical contrast with the rest of the grain, yielding a resolvably younger age of 97.8 ± 0.3 Ma. The data show that garnet growth in metapelites may take less than 1 Ma and, within that short time, progresses in several pulses that last less than c. 200 kyr. Our results demonstrate that garnet growth may occur much faster than required for changes in P–T conditions caused by tectonic processes. Pulsed, ultrafast garnet growth occurred instead at isobaric and isothermal conditions, far removed from equilibrium, and resulted in high-flux fluid production. While challenging the equilibrium paradigm, this example provides a rare glimpse into reaction overstepping and the rapid pushes of the system to attain equilibrium during periods of efficient matrix element transport.

How to cite: Tual, L., Smit, M. A., Cutts, J. A., Musiyachenko, K., Kooijman, E., Majka, J., and Foulds, I.: Garnet growth in a geological blink of an eye: evidence from high-precision Lu-Hf chronology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17461, https://doi.org/10.5194/egusphere-egu24-17461, 2024.

Bing Yu1,2* , M. Santosh1,3, Richard M. Palin2, Cheng-Xue Yang1

1School of Earth Sciences and Resources, China University of Geosciences Beijing, No. 29 Xueyuan Road, Haidian District, Beijing 100083, China

2Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, United Kingdom

3Department of Earth Science, University of Adelaide, Adelaide SA 5005, Australia

*E-mails:eart0615@ox.ac.uk ; bing-yu@email.cugb.edu.cn

 

The existence of Earth's oldest supercontinent Ur is controversial due to be paucity of rock records related to early continent-building processes, particularly since juvenile felsic crust formed during the Early Archean (4.0–3.2 Ga) in many cases had been reworked or destroyed. The Paleo-Mesoarchean terranes are therefore of potential interest, the subduction-related arc magmatism and high-grade metamorphism in these regions can be used as important clues to trace the history of the assembly of Earth’s oldest supercontinent.

The Southern Granulite Terrane (SGT) in India is a collage of continental blocks ranging in age from Paleo-Mesoarchean through Neoarchean and Late Neoproterozoic-Cambrian, providing a near-complete record of the history of assembly and disruption of several supercontinents. The Coorg Block and the surrounding Mercara suture zone are important windows for tracing the history of the Ur supercontinent. We investigate the Coorg Block composed dominantly of charnockites and mafic granulites and the Mercara Suture Zone exposing extensive khondalites (granulite facies metapelites). The khondalite belt in the Mercara Suture Zone is currently the oldest known khondalite series, and zircon U-Pb data of detrital zircons indicate that the protoliths formed during the Paleoarchean (up to 3.5 Ga), with high-grade metamorphism at ca. 3.1 Ga, coinciding with the timing of assembly of supercontinent Ur. Phase equilibria modelling indicated a peak temperature of above ca. 900 °C and pressure up to 12 kbar. The charnockite suite (usually associated with mafic granulite enclaves) from the Coorg block ranges in age from Mesoarchean to late Neoarchean, with magmatic xenocrysts showing ages up to 3.5 Ga, this suggests that old crustal components are present in the crystalline basement. The peak of magmatic emplacement for the charnockite and gabbroic suites, both showing arc affinity, occurred at ~3.15 Ga and the arcs accreted onto the Dharwar craton to the north during the Neoarchean transition, building the ‘expanded Ur’. Mafic granulites formed by the underplating of basaltic magma derived through slab partial melting during subduction. The magmatic zircon core suggests Mesoarchean emplacement and the metamorphic zircons as well as monazite indicate collisional metamorphism at 3.0-3.1 Ga marking the assembly of the Ur supercontinent.   

We also combine our data with published results from other regions including Madagascar and East Antarctica, where remnants of the early crust are preserved in an attempt to reconstruct the Ur supercontinent. Our spatio-temporal analysis and model simulations suggest near-simultaneous assembly of the early crustal nucleic on the globe around ca. 3.1-3.0 Ga, although some parts of the supercontinent did not cratonize until the Late Mesoarchean.

Keywords: High-grade metamorphism; Zircon and monazite Geochronology; Ur supercontinent

Reference:
Yu et al., 2021. Gondwana Research 91: 129-151.
Yu et al., 2022. Precambrian Research 370: 106537.
Yang et al., 2023. Gondwana Research, 118, 1-36.

How to cite: Yu, B.: Mesoarchean crustal growth in the Coorg block and Mercara suture zone, southern India: evidence for reconstructing the Ur supercontinent, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17675, https://doi.org/10.5194/egusphere-egu24-17675, 2024.

Subduction erosion present in oceanic subduction zones has been reported recently in continental subduction-collision zones, but the response of the upper plate remains enigmatic. The Dabie-Sulu orogen is considered to have formed by deep northward subduction of the Yangtze Block (YB) beneath the North China Block (NCB). However, the Haiyangsuo complex within the Northern Sulu ultrahigh-pressure (UHP) belt has intriguingly been accepted as NeoarcheanPaleoproterozoic metamorphic basement from the NCB. We examined petrography, mineral chemistry and geochronological data for the Haiyangsuo mafic granulites to decipher their multiperiod metamorphic evolution. The mineral assemblage from the first episode features coarse-grained Grt1 + Cpx1 ± Opx1 ± Amp1 + Pl1 + Ilm that formed under high-temperature (HT) granulite-facies conditions (7.3–8.3 kbar and 830–895 ℃). The second episode produced “red-eye socket” Grt2 + Cpx2 + Pl2 ± Amp2 + Qtz + Rut generated during high-pressure (HP) granulite-facies metamorphism (12.2–17.2 kbar and 800–875 ℃). Grt1 contains high heavy rare earth elements (HREEs) and oxygen isotopes in equilibrium with late Paleoproterozoic metamorphic zircons, while Grt2 has lower HREEs and oxygen isotopes, similar to Triassic metamorphic minerals in the Dabie-Sulu orogen. P-T estimates from pseudosection modeling and geothermobarometry show that Triassic HP granulite-facies metamorphism was followed by rapid decompression and slow cooling; these rocks resemble but mostly differ from the UHP eclogites due to non-UHP conditions. The above characteristics collectively imply that the metamorphic basement from the NCB was subducted to lower crustal to upper mantle depths (50–60 km) while the YB was subducted deeply; thus, tectonic erosion can indeed occur during continental subduction and collision.

How to cite: Liu, L.: Tectonic erosion along a continental subduction-collision zone revealed by compositions and metamorphism of mafic granulite in the Sulu orogen, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18068, https://doi.org/10.5194/egusphere-egu24-18068, 2024.

EGU24-18090 | Posters on site | GMPV4.1

P-T-t evolution of the Pulkau and Pleißing Nappes, Thaya Window, Lower Austria 

Christoph Hauzenberger, Martin Findl, Etienne Skrzypek, Daniela Gallhofer, Manfred Linner, and Harald Fritz

Two NW-SE trending profiles across the Pleißing and Pulkau nappes were investigated in detail and 56 samples from the Pernegger trench, 31 samples from the Pulkau and 32 samples from the Thaya valleys recovered. The Pleißing nappe exhibits amphibole-gneiss, metapelite, orthogneiss / metatuffite and marble with the corresponding mineral assemblages of hornblende - mica - feldspar - quartz - titanite - ilmenite; staurolite - garnet - mica ± graphite ± turmaline ± monazite; mica - biotite -epidote -kalifeldspar – quartz - ilmenite ± garnet ± chlorite; and calcite - biotite -mica -quartz -epidote - titanite ± amphibole. Grt-amphibolites, partly retrograded to greenschists, metapelite / phyllonite, and orthogneiss / metatuffite are recognized in the Pulkau nappe with the mineral assemblages amphibole -epidote - chlorite - rutile - ilmenite -quartz - titanite; mica - biotite - garnet - hornblende -quartz -plagioclase -ilmenite - monazite ± staurolite; mica - biotite - chlorite -Kfeldspar -quartz -ilmenite -magnetite ± turmaline.

P-T estimates from the Thaya valley profile are 580-620 °C / 0.8-0.9 GPa for the Pleißing nappe and 600-640 °C / ca. 0.5-0.8 GPa for the Pulkau nappe. Two phase garnets occur in some grt-metapelite from the Pleißing nappe. Garnet cores indicate P-T conditions of ca. 550 °C / 0.5 GPa and garnet rims in equilibrium with matrix minerals give ca. 590 °C / 0.9 GPa. P-T estimates along the Pulkau valley are 590-630 °C and 0.8-0.9 GPa for the Pleißing nappe and 540-580 °C / 0.5-0.8 GPa for the Pulkau nappe.

U-Pb dating of monazite by LA-ICPMS yielded a metamorphic age of 331 ± 2Ma , similar to the younger monazite age group of Štípská et al. (2015). The Th-U-Pb ages obtained by electron microprobe are slightly younger at 317 ± 6 Ma, which may be related to Pb loss during monazite recrystallization. Zircons from two meta-tuffite samples, one from the Pleißing, the other from the Pulkau nappe yielded concordant ages of 587 ± 8 Ma and 592 ± 8 Ma, respectively, similar to the magmatic age of the Biteš gneiss. The sample from the Pleißing nappe contained in addition a second age group with 620 ± 8 Ma.

Based on our geothermobarometric results the Pleißing and Pulkau nappe experienced a nearly identical metamorphic overprint in the northern part of the Thaya window. A slight decrease in metamorphic grade is seen in the southern part of the Pulkau nappe, suggesting a decreasing metamorphic gradient from NE to SW.

Štípská, P., Hacker, B. R., Racek, M., Holder, R., Kylander-Clark, A. R. C., Schulmann, K., & Hasalová, P. (2015). Monazite dating of prograde and retrograde P–T–d paths in the Barrovian terrane of the Thaya window, Bohemian Massif. Journal of Petrology, 56(5), 1007-1035.

How to cite: Hauzenberger, C., Findl, M., Skrzypek, E., Gallhofer, D., Linner, M., and Fritz, H.: P-T-t evolution of the Pulkau and Pleißing Nappes, Thaya Window, Lower Austria, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18090, https://doi.org/10.5194/egusphere-egu24-18090, 2024.

The present study integrates petrochemical analyses and phase equilibria modeling of rare Garnet-Al-Silicates (Kyanite-Sillimanite-Andalusite) - Staurolite ± graphite bearing anatectic metapelites to comprehend its tectono-metamorphic evolution from the Eastern Himalayan Syntaxis (EHS), NE India. Extensive field studies reveal the occurrence of high-grade metapelitic rocks as enclaves in the Trans-Himalayan Lohit group of rocks (migmatitic gneisses), Dibang Valley, Arunachal Pradesh, India. Quartz-garnet-kyanite-plagioclase represents the peak metamorphic assemblage, in which garnets (Fe-rich) occur as porphyroblast and kyanite exhibit long crystals embedded in polygonal quartz and feldspar. The presence of peritectic kyanite and overgrowth of muscovite corona over kyanite (back reaction of melt with Al-silicates) indicates melting in the metapelitic rocks. Additionally, the presence of hydrous phases (e.g., muscovite and biotite), in the matrix points towards a wet melting condition. Furthermore, the post-peak metamorphic history of the rocks can be characterized by the presence of sillimanite and andalusite formed during exhumation. Thermobarometric studies estimate the peak metamorphic conditions for the metapelite at T =650±25°C, P~8 Kbar. The P-T pseudosection analysis predicts the peak metamorphic condition for the metapelites at T~ 650°C, P=7-8 Kbar; with clockwise PT paths. This suggests a wet melting condition at T~ 680°C (Solidus) and P~8 Kbar for the high-grade metapelites possibly related to the India-Asia collision from the Eastern Himalayan Syntaxis of Arunachal Himalaya.

How to cite: Saikia, D., Ozha, M., and Shankar, R.: Metamorphic Evolution of Rare Garnet-Al-Silicates (Kyanite-Sillimanite-Andalusite)-Staurolite ± graphite bearing Anatectic Metapelites from Eastern Himalayan Syntaxis, NE India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20042, https://doi.org/10.5194/egusphere-egu24-20042, 2024.

The northern margin of the North China Craton is an important tectonic zone, bordered by the globe’s largest Phanerozoic accretionary orogen, the Central Asian Orogenic Belt. The Paleoproterozoic strata on the northern margin of the North China Craton (NCC) comprise a relatively intact low-grade (meta-)sedimentary sequence, but whether there are breaks in the sequence and the tectonic setting in which the sequence was deposited are uncertain. In this work, Lu–Hf isotopic, and zircon U–Pb geochronological analyses were performed on (meta-)sedimentary rocks from the Paleoproterozoic strata, to investigate the potential provenance, depositional age, and depositional environment, and discuss the likely tectonic setting of sedimentation on the northern margin of the NCC during the Paleoproterozoic. The distribution of detrital zircon ages shows that the lower meta-feldspathic sandstone unit of the Paleoproterozoic sequence was deposited after ca. 2.2 Ga, whereas the maximum depositional age of (meta-)quartz siltstone and quartzites were around 1.89 Ga and at from ca. 1.86 to 1.81 Ga, respectively. Integration of our U–Pb and Hf isotope data with data from the other regions of the NCC, indicate that the Paleoproterozoic strata have experienced a depositional environment between ca. 2.2–1.81 Ga in an extensional basin system. We further proposed that the northern margin of the NCC evolved from an extensional tectonic setting, possibly related to slab rollback. Subsequently, the Paleoproterozoic sequence was affected by a ~1.8 Ga metamorphic event to form these (meta-)sedimentary rocks in the region.

How to cite: Chen, N. H.-C.: Zircon U-Pb ages and Lu-Hf isotopes of Paleoproterozoic metasedimentary rocks in the North China Craton: Implications for its crust and evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1331, https://doi.org/10.5194/egusphere-egu24-1331, 2024.

EGU24-2374 | ECS | Posters virtual | GMPV4.2

Reaction textures in titanite-bearing mafic granulite: Constraints on the metamorphic evolution of Angul-Tikarpara domain of the Eastern Ghats Province, India 

Aparupa Banerjee, Proloy Ganguly, Sankar Bose, Nilanjana Sorcar, Sneha Mukherjee, and Kaushik Das

The Angul-Tikarpara domain of the northern Eastern Ghats Province (EGP) of Eastern India is characterized by high-grade rocks like felsic gneiss, khondalite (garnet-sillimanite-K-feldspar-quartz bearing granulite), charnockite, mafic granulite and aluminous granulite (spinel-magnetite-hematite-garnet-cordierite-sillimanite-K-feldspar-quartz-biotite-plagioclase). Two distinct mineralogical varieties of mafic granulite are present as enclaves within felsic gneiss and coarse-grained charnockite. Type-A mafic granulite is composed of orthopyroxene, clinopyroxene, hornblende, plagioclase, magnetite, ilmenite, biotite, and/or garnet with a subordinate amount of quartz. Type-B mafic granulite, on the other hand, contains titanite along with clinopyroxene, plagioclase, hornblende, garnet, calcite, ilmenite, magnetite, and biotite. The present study is focused on the latter variety where the peak (MA1) assemblage is represented by clinopyroxene, plagioclase, titanite, ilmenite, magnetite, calcite, and hornblende. Porphyroblastic clinopyroxene in the aforesaid assemblage is characterized by well-developed Al-zoning, with Al2O3-content being maximum at the core (5.3–3.8 wt.%) and minimum at the rim (3.6–0.22 wt.%). It appears that the high-aluminous core had stabilized at the peak stage, while the low-aluminous rim formed during the retrogressive stage characterized by decompression (MA1R). From the zoning pattern, the peak MA1 and MA1R conditions were estimated to be 8.6‒6.8 kbar, ~850˚C, and 4.2‒3 kbar, 660 ˚C, respectively. During the decompression, subidioblastic titanite broke down to low-Al clinopyroxene (2.5-0.5 wt.% Al2O3) + ilmenite intergrowth surrounding the former phase. The decompression was associated with cooling during which coronal garnet grew surrounding porphyroblastic clinopyroxene, plagioclase, and calcite. Zn-bearing spinel was exsolved from magnetite during this stage. Phase diagram modeling of Type-B mafic granulite shows that MA1 metamorphism occurred along a clockwise P-T trajectory. Further development of grossular-rich coronal garnet around hornblende suggests that the rock underwent a second prograde metamorphic event (MA2). In the chondrite-normalized rare earth element (REE) diagram, Type-B mafic granulite shows a more fractionated pattern than Type-A mafic granulite.

Textural, thermobarometric, and phase equilibria data indicate that the metamorphic evolution of Type-B mafic granulite is comparable to the recently published P-T evolution of Type-A mafic granulite, aluminous granulite, khondalite, and fine-grained charnockite of the area where the MA1 metamorphism involved decompression and associated cooling from ∼850C, 7–8 kbar to ∼760C, 4–5.8 kbar at ca. 1200 Ma and followed by subsequent prograde MA2 metamorphism at ca. 990 Ma. This study provides additional evidence that the geological evolution of the Angul-Tikarpara domain is different than the rest of the EGP lying at the southern part of the Mahanadi Shear Zone (MSZ). The latter segment of the EGP is characterized by ultra-high temperature metamorphism (UHT) at ca. 1030–990 Ma which is absent in the present study area. Such contrasting ages and P-T evolution of high-grade rocks on either side of the MSZ confirm the fact that the shear zone represents a terrane boundary which was formed by juxtaposition of the Angul-Tikarpara domain with the EGP only after ca. 960 Ma.

How to cite: Banerjee, A., Ganguly, P., Bose, S., Sorcar, N., Mukherjee, S., and Das, K.: Reaction textures in titanite-bearing mafic granulite: Constraints on the metamorphic evolution of Angul-Tikarpara domain of the Eastern Ghats Province, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2374, https://doi.org/10.5194/egusphere-egu24-2374, 2024.

EGU24-2810 | Orals | GMPV4.2 | Highlight

Acquisition and interpretation of ages from xenolithic mantle eclogites – the oldest records of subducted oceanic crust 

Sonja Aulbach, Aratz Beranoguirre, Leo Millonig, and Johannes Pohlner

Eclogites and their constituents ubiquitously form part of kimberlite-borne xenolith and xenocryst suites. Their mineralogic, geochemical, stable and radiogenic isotope characteristics unambiguously point to a crustal protolith, likely derived from ancient spreading ridges [1]. Available P-T constraints and the frequent occurrence of accessory coesite and/or diamond [2] indicate ultrahigh-pressure metamorphism. Because cratonic eclogites occur globally, their compositions can provide invaluable insights into ancient geodynamics and mass cycles, for which the ages of their formation (rather than later metasomatic overprints) must be constrained. However, the accurate and precise age determination for cratonic eclogites – and the application of petrochronologic concepts in general – is hampered by the fact that (i) they were emplaced into the cratonic mantle lithosphere billions of years ago, after which their composition may have been altered, (ii) they last resided at mantle temperatures enabling diffusive (partial) isotopic equilibration of their mineral constituents, (iii) accessory minerals amenable to U-Pb dating are rare (except rutile, which invariably yields kimberlite eruption ages) and, if present, of  metasomatic origin, and (iv) they represent high-variance systems, often consisting of only garnet and omphacite and typically devoid of inclusions.

 

The recent advent of garnet U-Pb geochronology as applied to metamorphic rocks [3] opened a new door to obtaining accurate and precise ages for eclogites, including xenoliths from the Navajo Volcanic Field presumably sampling the Cretaceous Farallon plate [4]. However, preliminary work, using a multicollector ICPMS (Thermo Finnigan Neptune Plus) at the FIERCE laboratory (Goethe University Frankfurt), shows that even garnet from relatively cold (last equilibrated at ~815-1000°C; [5]) eclogite xenoliths from the Kaapvaal craton margin may have lost its original crystallisation age information. Garnet in these eclogites, which were likely emplaced during the Mesoproterozoic Namaqua-Natal orogeny, all yield U-Pb ages are within several 100 Ma of Cretaceous kimberlite eruption. This is in stark contrast to results for UHT granulite xenoliths from the Kaapvaal craton, which retain 3 Ga garnet U-Pb ages [6]. This may reflect low garnet U-Pb closure T in cratonic eclogite related to slow secular lithosphere cooling, as opposed to high closure T in granulite owing to fast cooling from magmatic or peak metamorphic T.

 

Available “conventional” ages for eclogitic xenoliths and diamonds from cratons globally reveal some systematics, indicating metamorphism around 2.9-2.6 Ga and again 2.0-1.8 Ga. These ages can be interpreted in the framework of the supercontinent cycle, whereby the Palaeoproterozoic ages reflect emplacement during assembly of Nuna-Columbia, and the Meso-/Neoarchaean ages reflect the amalgamation of the oldest cratonic nuclei into Earth’s first supercontinent, consistent with a global, linked plate tectonic network. In contrast, a temporal link to emplacement ages for TTGs is weak, suggesting that cratonic eclogite is not the complementary residue to Earth’s oldest continental crust [1].

 

[1] Aulbach and Smart 2023 AREPS; [2] Stachel et al. 2022 RIMG; [3] Millonig et al. 2020 EPSL; [4] Pohlner, Aulbach et al. in prep.; [5] Le Roex et al. 2020 JPet; [6] Shu, Beranoaguirre et al. in prep.

How to cite: Aulbach, S., Beranoguirre, A., Millonig, L., and Pohlner, J.: Acquisition and interpretation of ages from xenolithic mantle eclogites – the oldest records of subducted oceanic crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2810, https://doi.org/10.5194/egusphere-egu24-2810, 2024.

Cratonic margin basins are crucial in tracking the provenance characteristics. This study aims to characterize one of the Proterozoic basins in Southeastern India known as Pranhita Godavari (PG) basin. Nestled between the famous Dharwar and Bastar cratons, the PG basin is about 450 Km long NW-SE trending rift-related basin with a huge thickness of siliciclastics. The basin consists of three cycles of deposition. In this study, we characterize the geochemistry, U-Pb geochronology and Lu-Hf systematics of the detritus as well as the adjacent basement Gneiss in order to define the sediment source.

                        K2O/Na2O v SiO2 and the Discriminant function diagrams (Verma & Armstrong-Altrin, 2013) indicate a passive margin setting for the sediments. Together with Eu/Eu*, the high La/YbN ratios (8.23-37.9) and LREE enriched and flat HREE patterns indicate a felsic source. The other geochemical indicators like TiO2 versus Zr and Ni, Al2O3/TiO2, Th/Co, La/Sc ratios along with high Th/U also indicate felsic continental sources.   The different weathering indices like CIA.PIA, and  ICV indicate moderate to slightly intense weathering of the source terrains producing mostly mature sediments.

The metamorphic zircons (average Th/U=0.88) from the basement Gneiss yield a Concordia age of 2490±6 Ma and a weighted mean age of 2490±6 Ma. Three magmatic zircon cores yield a weight mean average of 2677±36 Ma. Previous studies from the Bastar and Dharwar cratons also report the presence of 2.5 Ga old zircons.

The sediment was mainly sourced from the Paleoarchean to Mesoproterozoic sources with detrital zircon ages spread from 3571-1622 Ma. The Probability Density Plots show major peaks at 1842, 2498, 2637 Ma and minor peaks at 1637,3340, 3567 Ma. The Youngest detrital zircon method brackets the maximum depositional age of the Mulug Formation 1622±33 Ma.

The zircons from the basement gneiss of Peninsular Gneissic complex show negative Hf isotope values (εHf= -15.27 and 0.17). Similarly, the detrital zircons show negative values (εHf =-12.58-0.70) indicating their derivation from evolved sources.

The age peaks and the εHf composition from the Mulug formation perfectly match with the basement gneiss ages. This together with published literature indicates that the Mulug formation was deposited at ~1.6 Ga and was sourced from the eastern Dharwar and Bastar cratons

How to cite: Ganaie, A. M.: Detrital Zircon U-Pb Geochronology and Lu-Hf isotope systematics from the Pranhita Godavari basin: Implications for the Provenance and Mesoproterozoic tectonics  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3845, https://doi.org/10.5194/egusphere-egu24-3845, 2024.

The Jonnagriri greenstone belt (JGB) of eastern Dharwar craton is one of the unique and economically important greenstone belts of southern India. This greenstone sequence consists of metabasalts, meta-felsic volcanics and schistose meta-tuffs surrounded by granitoid intrusives. These intrusives are the only known granitoid in India that hosts orogenic type gold deposit in the Dona sector of JGB. In our present work, we are focusing on the granitoids emplaced surrounding the JGB that are broadly classified into two main groups; (i) The Pagadarayi granodiorite (PGD) and (ii) The Chennampalli granites (CGR). The present study is to examine the geochemical evolution, decipher the tectonic settings and determine the timing of emplacements of the granitoids using whole rock geochemistry and U-Pb zircon dating. This will also help us to understand the crustal architecture of the part of the eastern Dharwar Carton in the southern Indian peninsula. The PGD compositionally ranges from tonalite to granodiorite suits and the adjacent CGR ranges from granite to syenogranite suits of rocks. The petrogenetic evolution of these granitoid clearly showed a transition from calc-alkaline to a more fractionated potassic rich granite. The major oxide and trace element behavior showed that they are metaluminous to peraluminous in nature where the PGD are geochemically linked to the TTGs while the potassic rich CGR phase majorly shares its genetic link with hybrid and two-mica granites. The source of PGD suits of rocks is inferred to be an outcome of partial melting of TTG crust and the CGR suits are ferromagnesian deficit phase with an increase in K2O/Na2O due to crustal contamination, which indicates a result of crustally reworked magmatic phase. Therefore, an enrichment of LREE and LILE relative to HREE and HFSE with depletion of Nb-Ta-Ti notably is observed, which represents a convergent setting signature for these granitoids. The PGD suit of rocks dominantly showed I-type characteristics affirmed by their ASI index, and with the typical SiO2, CaO and FeO contents, indicating that they are part of volcanic arc to island arc granitoid settings. The CGR showed distinctive characteristics of A2 type granites due to its Y/Nb value ranging from 1.2 to 1.83 depicting a shallow depth subduction regime which are formed within the crust, indicating a within plate post-colliotional settings. Zircon U-Pb dating by LA-ICP-MS reveals that the first emplacement of PGD recorded a concordant emplacement age of 2651±14 Ma and the CGR yielded concordant ages of 2557±10 Ma and 2532±22 Ma respectively. This implies that the Jonnagiri granitoid represents an orogenic type tectonic settings where diversification in the mode of granitoid intrusion showed a change in volcanic-arc magmatism to within plate magmatism, from the older phase of tonalite-granodiorite emplacement to the successive younger potassic rich syenogranite emplacement. 

How to cite: Das, S. and Chinnasamy, S. S.: Granitoids of the Jonnagiri greenstone belt of eastern Dharwar craton: Constraints from geochemistry and U-Pb zircon geochronology., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6082, https://doi.org/10.5194/egusphere-egu24-6082, 2024.

EGU24-7316 | ECS | Posters on site | GMPV4.2

Machine Learning-Based Quantification of Archean Crustal Thickness (Moho Depth) 

Yu Zhang, He Liu, and Wei-dong Sun

The Earth's crust, an incredibly thin layer of rock encompassing the planet's outermost solid shell, plays a crucial role in sustaining human existence by housing vital natural resources. Moreover, actively engaged in a multitude of geological processes such as plate tectonics, volcanic activities, and erosion, it significantly molds landscapes and influences natural phenomena, thereby serving as a cornerstone in maintaining Earth's habitable conditions. However, substantial debate persists regarding the mechanisms governing the growth of continental crust, and the broader implications of its role within Earth's tectonic framework remain elusive. In this study, we sought to predict the historical evolution of crustal thickness during the Archean era using machine learning based on global geochemical data of igneous rocks. The model predicted that crustal thickness decreased progressively from approximately ~35km during the Paleoarchean period to a nadir of roughly ~33km in the Early Mesoarchean era. Subsequently, there was a trend of thickening observed from the Early Mesoarchean to the Neoarchean period. Our findings reveal a dynamic history of Archean crustal thickness characterized by an initial phase of thinning followed by subsequent thickening from the Paleoarchean to the Neoarchean. These fluctuations align cohesively with the transition from a pre-plate tectonic to a regime of sustained plate tectonics. The observed phenomena were attributed to the initiation of ultrathick primary crust formation, accompanied by a tectonic regime primarily influenced by Rayleigh–Taylor instabilities. The instabilities arising from an excessive buildup of primary crust likely played a pivotal role in causing the subsequent thinning of the continental crust, marking the transition phase towards a predominantly modern-style subduction.

How to cite: Zhang, Y., Liu, H., and Sun, W.: Machine Learning-Based Quantification of Archean Crustal Thickness (Moho Depth), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7316, https://doi.org/10.5194/egusphere-egu24-7316, 2024.

EGU24-7908 | Orals | GMPV4.2

Tracing modern-style cold subduction in the Proterozoic – evidence from H2O and trace elements in detrital rutile 

Mona Lueder, Jörg Hermann, Ines Pereira, Renée Tamblyn, and Daniela Rubatto

To understand the onset and evolution of cold subduction on Earth, detrital sedimentary rocks of Precambrian age, potentially derived from exposed high-P low-T metamorphic rocks can be investigated. This requires the estimation of peak metamorphic pressure and temperature, time of formation, and source lithology (P-T-t-X) of detrital single grains. Rutile is a common accessory mineral in subducted oceanic crust and one of the most likely minerals from subducted rocks to survive sedimentation processes. As single grain T-t-X estimates on rutile are possible, it is a prime candidate for the investigation of subduction processes through time.

We developed a method to identify rutile formed in modern cold subduction conditions, by combining in-situ polarised Fourier Transform Infrared Spectroscopy (FTIR) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS).

Our study reveals a pressure-dependent variation in hydrogen content within metamorphic rutile, ranging from less than 10 to 2500 μg/g H2O. Higher peak metamorphic pressures correspond to elevated H2O contents, particularly noticeable in mafic low-temperature eclogite facies rutile, suggesting H-in-rutile can be used as a pressure indicator. Using Zr in rutile as a temperature indicator, H2O/Zr ratios act as proxies for thermal gradients (P/T) in metamorphic rutile. When combined with low Nb, W, and Sn contents, typical of mafic protoliths, it is possible to identify modern-style cold subduction of mafic crust using trace element signatures in detrital rutile.

Therefore, detrital rutile can serve as a tracer for subduction conditions over time, as modern-style cold subduction signatures are preserved in rutile during weathering and sedimentary processes.  In this study, we test our novel approach on detrital rutile grains of sandstones and arkoses from the Torridon and Ardvreck Groups, Hebridean in NW Scotland. Our analysis reveals that some grains of the Torridon Group of late Proterozoic age (detrital ages ranging from 1.0 to 1.9 Ga; Pereira et al., 2020) exhibit high H2O/Zr ratios and low total Nb+W+Sn contents, typical of low-T eclogite facies rutile. This implies that low-T eclogites which formed during cold subduction were likely exposed and eroded in the catchment of the sedimentary basins, indicating modern-style cold subduction during the Mesoproterozoic.  We propose that the combined measurement of H2O and trace elements in detrital rutile is a powerful tool to search for remnants of cold subduction through the Earth’s history.

 

Pereira, I., Storey, C.D., Strachan, R.A., Bento dos Santos, T., Darling, J.R., 2020. Detrital rutile ages can deduce the tectonic setting of sedimentary basins. Earth Planet. Sci. Lett. 537, 116193. https://doi.org/10.1016/j.epsl.2020.116193

How to cite: Lueder, M., Hermann, J., Pereira, I., Tamblyn, R., and Rubatto, D.: Tracing modern-style cold subduction in the Proterozoic – evidence from H2O and trace elements in detrital rutile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7908, https://doi.org/10.5194/egusphere-egu24-7908, 2024.

EGU24-8283 | ECS | Orals | GMPV4.2

Machine Learning an All-Atom Empirical Force Field for a Water-Silica System 

Anthony Val Camposano, Henrik Andersen Sveinsson, and Anders Malthe-Sørenssen

Molecular modeling of the interaction between silica and water provides a better understanding of how water affects rocks and glasses at the nanoscale. Here, we parametrize a new classical dissociative force field for the water–silica system. We create a classical force field capable of reactive interactions between all chemical species in the water–silica system, using the same functional form by Vashishta et al. to describe bulk water, silica, and silica–water interactions. Using a hierarchical genetic algorithm as a global optimizer and the Nelder-Mead simplex algorithm as a local optimizer, we parameterized the Vashishta force field to reproduce the density, transport properties, and vapor-liquid properties of water. We then used the same method to obtain water–silica interaction parameters to reproduce gas phase orthosilicic geometry and silica surface properties such as silanol concentration, heat of immersion, and the wettability angle of water on a silica surface. For oxygen–silicon interactions in silica, we reuse an existing Vashishta potential parameter set that has been parameterized to reproduce bulk mechanical behavior, surface properties, and fracture properties. Our developed force field can be used to study processes such as dissolution, friction, and stress corrosion fracture in the presence of water over a wide range of thermodynamic conditions for larger-scale and longer-scale simulations.

How to cite: Camposano, A. V., Sveinsson, H. A., and Malthe-Sørenssen, A.: Machine Learning an All-Atom Empirical Force Field for a Water-Silica System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8283, https://doi.org/10.5194/egusphere-egu24-8283, 2024.

EGU24-8578 | ECS | Orals | GMPV4.2

RocMLMs: Predicting Rock Properties through Machine Learning Models 

Buchanan Kerswell, Nestor Cerpa, Andréa Tommasi, Marguerite Godard, and José Alberto Padrón-Navarta

Predicting the physical properties of rock is critical for modeling mantle convection. Density changes are the main driving force for mantle convection, for example, while elasticity/seismic properties allow probing of mantle dynamics and structure. Pressure-temperature (PT) conditions predicted by numerical thermo-mechanical models are often mapped to pre-computed pseudosections calculated by Gibbs Free Energy Minimization (GFEM) programs (e.g., Perple_X; Connolly, 2009) to predict phase changes and the associated evolution of rock properties (e.g., density, seismic wave velocities, and fluid contents). In principle, GFEM programs could be coupled to numerical geodynamic simulations (at each point in space and for each timestep) to establish models where phase assemblages and rock properties evolve self-consistently. In practice, this is currently intractable because GFEM programs remain too slow (102–104 ms per node) to be coupled to high-resolution numerical geodynamic models. While parallelization of GFEM calculations can increase efficiency dramatically (e.g., MAGEMin; Riel et al., 2022), predicting rock properties recursively during a geodynamic simulation requires GFEM efficiency on the order of ≤ 100–10-1 ms to be feasible. As an alternative to the GFEM approach, this study demonstrates the efficiency of predicting target rock properties through pre-trained machine learning models (referred to as RocMLMs). In our initial test case, RocMLMs are trained to predict density, seismic wave velocity, and melt fraction for dry upper mantle rocks based on an array of 128 Perple_X pseudosections (with 128x128 PT resolution) derived from 3111 harzburgite and lherzolite samples retrieved from the Earthchem.org repository. The training dataset size was reduced from 12813 to 1283 PTX examples by transforming the 11 oxide components of X (bulk rock composition) into a single Fertility Index value representing the estimated degree of melt extraction from a primitive mantle source. We show that Decision Tree, K-Neighbors, and single-layer Neural Network algorithms can predict rock properties up to 103 times faster than commonly-used GFEM programs (with some performance trade-offs), attaining the required efficiency of 100–10-1 ms. Our results imply that implementing dynamic evolution of rock properties in geodynamic simulations is now possible with RocMLMs. Future generations of RocMLMs will include hydrated systems and a larger array of mantle compositions (e.g., dunites and pyroxenites).

How to cite: Kerswell, B., Cerpa, N., Tommasi, A., Godard, M., and Padrón-Navarta, J. A.: RocMLMs: Predicting Rock Properties through Machine Learning Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8578, https://doi.org/10.5194/egusphere-egu24-8578, 2024.

EGU24-9828 | ECS | Posters on site | GMPV4.2

Predicting Vp/Vs in North America with a Machine Learning Approach 

Xingxing Gao, Yunfeng Chen, Zhou Zhang, and Wenyu Zhao

Vp/Vs (or the Poisson's ratio) provides critical information to constrain the bulk crustal composition, stress state, and tectonic evolution. The crustal Vp/Vs beneath the seismic station can be effectively determined by the receiver function H-κ stacking technique. However, complex crustal structures often cause large uncertainty in Vp/Vs measurements. Additionally, Vp/Vs observations are sparse in many regions of the world due to the uneven distribution of seismic stations. While interpolation methods have been widely applied to obtain a continuous distribution of Vp/Vs, these results are not accurate enough and may be strongly biased by the interpolation artifacts. Therefore, reliable mapping of the Vp/Vs variation in the crust remains a major challenge in seismological study.

We present a machine learning approach to estimate the Vp/Vs using multiple geophysical datasets. This approach assumes that the Vp/Vs is related to the physical and chemical properties of the crust. Specifically, we implement a Gradient Boosted Regression Tree algorithm (XGBoost) to develop an optimal prediction model for North America. To train the model, we use Vp/Vs as the target values and a compilation of geophysical observations as the predictor variables. These measurements are composed of two types of data: (1) continuous data, such as crustal velocities and gravity anomalies; (2) categorical data (tectonic type). We use 80% of the measurements to train the model, and the remaining 20% to validate the model. We first examine the reliability of this method by predicting Vp/Vs for the United States, where extensive geophysical data are available. Overall, the model achieves a high R2 value of 0.88 in all measured results versus prediction results, indicating robust prediction results at most locations. In the second, a more challenging test, we predict Vp/Vs for Canada where measurements are sparse and uneven, and the amount of data is only 14% of that in the United States. The results show an R2 value of 0.87 between the measured and predicted values. Feature importance analysis indicates that crustal shear wave velocity and tectonic type contribute most significantly to reducing the loss function. The prediction results show that bulk Vp/Vs varies between 1.70 and 1.90 across Canada, with a mean value of 1.82.  The cratonic regions generally exhibit high (>1.80) Vp/Vs with a relatively small (<0.05) variation, whereas Proterozoic orogens are characterized by a large Vp/Vs variation from 1.75 and 1.90. The lowest Vp/Vs of 1.66 is observed in the Phanerozoic orogenic belts of Cordillera, contrasting sharply with the basement rocks (~1.90) beneath the Alberta foreland basin. Overall, our study highlights the capability of the machine learning in discovering complex relationships between multi-dimensional geophysical data sets and resolving crustal Vp/Vs in continents globally.

How to cite: Gao, X., Chen, Y., Zhang, Z., and Zhao, W.: Predicting Vp/Vs in North America with a Machine Learning Approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9828, https://doi.org/10.5194/egusphere-egu24-9828, 2024.

EGU24-10081 | ECS | Posters on site | GMPV4.2

Insights into the Neoarchean Magmatic Evolution of the Western Nilgiri Block, Southern India. 

V.T. Muhammed Shamil, C.Ishwar -Kumar, and M.Satish -Kumar

The Southern Granulite Terrane (SGT) is an integral part of the Neoproterozoic Gondwana supercontinent. The Nilgiri block situated in the northern part of the SGT is characterized by Neoarchean magmatism. The major rock types found in the western part of the Nilgiri block include charnockite, hornblende biotite gneiss (HBG), pyroxenite, gabbro, amphibolite, mafic granulites, and granite. This study focuses on the geochemical signatures of major lithologies in the western Nilgiri block to understand the geological evolution within the broader Southern Granulite Terrane. Oxide data show charnockite samples with SiO2 from 51 to 67 wt% and HBG with SiO2 from 63 to 71 wt%. Normative Ab-An-Or classification diagrams indicate tonalitic and granodioritic signatures for charnockite and HBG, respectively. Both exhibit high Al2O3 (>15 wt%) and low K2O (<3 wt%). Charnockites and HBG display a magnesian and calcic-to-calc-alkalic composition, while mafic granulite shows a low-K tholeiite and calc-alkali composition. Zr vs. Ti diagrams reveal a volcanic arc signature for charnockite, HBG, and mafic granulites. In the study area, Peralimala Granite (PG), Ambalavayal Granite (AG), and Kalpetta Granite (KG) are present as plutons. KG and PG are magnesian, while AG is ferroan. KG and PG have an alkali-calcic composition, which contrasts with the calc-alkalic nature of AG. Comparative analysis with charnockites from the eastern Nilgiri block shows variations in SiO2 and Al2O3 content, with the western region exhibiting lower SiO2 and higher Al2O3. HBG in the western part shows a slightly elevated Na2O+K2O value. The charnockite consistently shows depletion in Y, Cs, Ta, Th, and U, coupled with Zr, Ba, Pb, and La enrichment. Similarly, HBG displays depletion in Y, Ta, Th, and U and enrichment in Rb, Sr, Zr, and Ba. Both rock types consistently exhibit enrichment in LREE and depletion in HREE. Mafic granulites show depletion in Cs, Th, Ta, and U, along with Nb, Ba, and Pb enrichment, displaying a flat REE pattern without significant fractionation. KG and PG exhibit enriched LREE and depleted HREE, whereas AG displays a strong negative Eu anomaly and a flat REE pattern. KG and PG are enriched in Ba, K, and La, with depletion in Ta, Nb, Ti, and Y. Conversely, AG is enriched in Ba, K, and Sr, with minimal Rb content and depletion in Th, U, Ta, Nb, and Ti, suggesting AG partial melts formed from the deep crustal level or upper mantle region. Charnockite and HBG show an affinity towards Archean TTG, suggesting their formation through the partial melting of Archean-hydrated, low K-metabasic source rocks, resulting in garnet amphibolite restite. U-Pb zircon data reveals an age of 2555±15 Ma for charnockite and 2512±12 Ma for HBG, indicating Neoarchean magmatism. Discordant ages from HBG align on a Pb-loss trend toward the lower intercept age of ~1100 Ma, suggesting a Late-Mesoproterozoic thermal event. U-Pb zircon data of Kalpetta Granite gives an age of 544±5 Ma, implying a Pan-African thermal event. These findings highlight distinct magmatic and thermal events in the western Nilgiri block, including Neoarchean activity and notable Late-Mesoproterozoic and Neoproterozoic thermal events.

How to cite: Shamil, V. T. M., -Kumar, C. I., and -Kumar, M. S.: Insights into the Neoarchean Magmatic Evolution of the Western Nilgiri Block, Southern India., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10081, https://doi.org/10.5194/egusphere-egu24-10081, 2024.

EGU24-10822 | ECS | Posters virtual | GMPV4.2

Metamorphic evolution of eclogite of Kem-Ludy Islands, Early Precambrian Belomorian eclogite province 

Varvara Grigorieva, Alexei Perchuk, Vasiliy Kozlovsky, and Fedor Sandalov

The Belomorian eclogite province (BEP) of the eastern Fennoscandian Shield (Russia) is one of the oldest eclogite metamorphic complexes on Earth, providing an opportunity to study the most ancient subduction processes. The BEP gained prominence due to the numerous publications on petrology and geochemistry of Archean-Paleoproterozoic HP metamorphic rocks from Gridino, Salma, and Kuru-Vaara areas. Here, we present results from a detailed petrological study of a representative retrograde eclogite sample from a new HP locality in the Kem-Ludy Islands, where eclogites form lenticular bodies and have conformable contacts with country gneisses.

The studied retrograde eclogite sample has a massive structure with a fine- to medium-grained granoblastic texture. At least three metamorphic stages were identified in the rock based on the mineral assemblages. The pre-eclogite stage is indicated by epidote inclusions in the cores of garnet porphyroblasts. Garnet, matrix omphacite, and quartz represent peak metamorphism stage. Plagioclase-clinopyroxene symplectites after the omphacite and amphibole-plagioclase kelyphytes around the garnet were formed at the retrograde stage, while peak metamorphism minerals were then replaced to different extents by secondary amphibole during fluid-rock interaction.

The application of garnet-clinopyroxene geothermometer and clinopyroxene-plagioclase-quartz geobarometer assessed peak metamorphic temperature of 625-670°C and minimum pressure of 1.2-1.3 GPa, respectively. The retrograde stage corresponds to conditions of 600-725°C and 0.6-0.7 GPa as determined by garnet-amphibole, amphibole-clinopyroxene, amphibole-plagioclase geothermometers, and clinopyroxene-plagioclase-quartz and amphibole-plagioclase geobarometers.

The established P-T metamorphic evolution of the retrograde eclogite from Kem-Ludy area differs from most of the eclogites of Gridino and Salma areas by lower pressure at the peak of metamorphism and a lack of decompressional heating up to the UHT granulite facies conditions. Therefore, Kem-Ludy area likely pertains to another tectonic slice than Gridino and Salma areas, where the Neoarchean and Paleoproterozoic ages of HP metamorphism are under debate. Further investigation is needed to clarify the tectonic position of Kem-Ludy area.

Financial support of Russian Science Foundation project 23-77-00066.

How to cite: Grigorieva, V., Perchuk, A., Kozlovsky, V., and Sandalov, F.: Metamorphic evolution of eclogite of Kem-Ludy Islands, Early Precambrian Belomorian eclogite province, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10822, https://doi.org/10.5194/egusphere-egu24-10822, 2024.

The Late Archean Gadag greenstone belt (GGB) in the northern continuity of extensive Chitradurga greenstone belt in the western Dharwar craton has extensive meta volcano-sedimentary cover apart from older TTGs (Tonalite-trondhjemite-granodiorite), pink granite and other intrusives. The GGB encompasses a very unique and classical orogenic type gold deposit known as Gadag gold field (GGF) where auriferous lodes are hosted by metabasalt, greywacke and BIFs in western, central and eastern part of GGF respectively. In this study, we focus on the deformation history and P-T conditions of metamorphism of greenstone rocks which could have influenced in the generation of auriferous fluid in GGB. Two events of deformation were suggested in GGB so far where the first event (D1) is represented by NW-SE trending pervasive fabrics (S1) and schistocity, whereas the second event (D2) marking the regional disposition of NNW-SSE tectonic trend. This is further corroborated by microscopic evidences of Q-M microlithons development and garnet porphyroblast growth that is post tectonic to D1 deformation, syn-tectonic to early D2 and stage 2 porphyroblast development of non-rotating porphyroblast model in garnetiferous amphibolite in the north-eastern part of GGB. However, the matrix continued to get deformed and reached stage 6 in garnetiferous schist with dominant sinistral sense of shear in the southern part of GGB. The estimated peak metamorphic temperature of garnetiferous amphibolite using hornblende-plagioclase thermobarometry is 578 ± 21°C and the pressures are 7.1 ± 3kb and 7.4 ± 2.3kb. Garnet-biotite thermometric estimation for the same garnetiferous amphibolite from north eastern part of GGB yielded 525 ± 25°C indicating a lower amphibolite facies of metamorphism. The auriferous quartz veins were associated with both the D1 and D2 phases of deformation, and the genesis of this auriferous fluid may be related to lower amphibolite facies of metamorphism of these host rocks as evidenced from the fluid inclusion study.

Keywords: craton, P-T conditions, thermobarometry

How to cite: Saikia, M. J. and Chinnasamy, S. S.: Deformation history and P-T condition of metamorphism of Gadag greenstone belt of western Dharwar craton, southern India: Implications on the genesis of orogenic gold mineralisation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10873, https://doi.org/10.5194/egusphere-egu24-10873, 2024.

EGU24-11081 | Posters on site | GMPV4.2

Mapping ancient geochemical terranes using feldspar Pb isotopes 

J. Stephen Daly, Michael Flowerdew, and Eszter Badenszki

Combined with geophysical, geochronological and structural data, isotope geochemical proxies (including Pb, Nd, Hf and Sr) are commonly used to correlate basement terranes and hence to test and refine supercontinent configurations. In the case of Pb, many such studies rely on whole-rock isotopic data, which being time-dependent, can be difficult to interpret.

By contrast, feldspars, by virtue of their low U/Pb and Th/Pb ratios, have time invariant Pb isotope compositions. They are also modally abundant rock-forming minerals and are amenable to in situ analysis and textural discrimination. This study evaluates the utility of Pb isotopes in feldspar as a mechanism to identify terrane boundaries and evaluate large-scale continental reconstruction models.

We are systematically collating feldspar Pb isotope data from Archaean and Paleoproterozoic basement rocks in the North Atlantic region (Laurentia-Baltica and the intervening continental plateaux) from literature sources as well as new measurements from outcrop and offshore wellbores from Scotland, Norway, Greenland and Russia. 

A particular focus is on the Lewisian Complex of Scotland because these rocks are argued to link with terranes in both Greenland and Baltica. Our Pb isotopic data identify four Pb isotopic domains in Scotland.  The NAC, Nagssugtoqidian and Rinkian terranes are recognised onshore and offshore west of Shetland and correlate strongly with Greenland.  Moreover the boundaries between them are consistent with large-scale sutures proposed on other grounds although they do not support the traditional nine-terrane model for the Lewisian Complex [1]. Feldspar Pb isotopic data from the Kola Peninsula and northern Fennoscandia are consistent with the suggestion that the sub-Moine inliers (previously considered to have Archaean protoliths, equivalent to the Lewisian Complex) have an affinity with Baltica [2].

References:

[1] Kinny et al. (2005) Journal of the Geological Society, London 162, 175-186.

[2] Strachan et al. (2020) Geology 48, 1094-1098.

How to cite: Daly, J. S., Flowerdew, M., and Badenszki, E.: Mapping ancient geochemical terranes using feldspar Pb isotopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11081, https://doi.org/10.5194/egusphere-egu24-11081, 2024.

The work reports on the state-of-the-art and future perspectives of Machine Learning (ML) in igneous petrology and volcanology. To do that, it starts reviewing established methods that mainly concern clustering, dimensionality reduction, classification, and regression. Among them, clustering and dimensionality reduction are particularly valuable for decoding the chemical record stored in igneous and metamorphic phases and to enhance data visualization, respectively. Classification and regression tasks find applications, for example, in petrotectonic discrimination and geothermobarometry, respectively. The main core of the discussion will consist of depicting the next future for ML in petrological and volcanological applications. I propose a future scenario where ML methods will progressively integrate and support established petrological and volcanological methods in boosting new findings, possibly providing a paradigm shift. In this framework, the use of multimodal data, data fusion, physics-informed neural networks, and ML-supported numerical simulations, will play a significant role. Also, the use of ML hypotheses formulation and symbolic regression could significantly boost new findings. In the proposed scenario, the main challenges are: a) progressively link machine learning algorithms with the physical and thermodynamic nature of the investigated processes, b) make deep learning algorithms more transparent, as they often operate as “black boxes,” c) advance in exploring cutting edge tools that rise from researches in Artificial Intelligence, and overall, d) start a collaborative effort among researchers coming from different disciplines in research and teaching.

How to cite: Petrelli, M.: Machine Learning in Igneous Petrology and Volcanology: State-of-the-Art and Perspectives, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13673, https://doi.org/10.5194/egusphere-egu24-13673, 2024.

EGU24-13794 | ECS | Posters on site | GMPV4.2

Estimating Biomass in the Lithosphere: A Machine Learning Approach 

Wenyu Zhao and Johnny Zhangzhou

Research on sampling and analysis of fluids and rocks within both continental and oceanic crusts has revealed a significant portion of Earth's prokaryotic biomass residing in the rock-hosted biosphere, extending to depths of several kilometers. This deep subsurface life within the lithosphere may host a substantial amount of Earth's biomass. However, more constrained estimates of this biomass are still lacking. In this study, we first determine the habitable volume of the lithospheric biosphere and then estimate its potential biomass. Temperature, a critical factor influencing the limits of life, is considered the primary focus in this context. We employ a machine learning approach to estimate the habitable volume of the lithosphere above the 122°C isotherm, which is considered the upper limit for prokaryotic life.

 

Our methodology involves selecting a range of geophysical and geological features that are thought to impact geothermal gradients. These include Moho depth, lithosphere-asthenosphere boundary (LAB) depth, topography, susceptibility, tectonic units, gravity mean curvature, vertical magnetic field, and distances to ridges, trenches, transform faults, young rifts, and volcanoes, as well as P-wave and S-wave velocities in the crust. We used a Gradient Boosted Regression Tree algorithm to develop two models correlating geothermal gradients in continental and oceanic settings with these geophysical and geological features. The models were applied to a binned grid with a 0.5° x 0.5° resolution, enabling the estimation of the depth to the 122°C isotherm for each grid based on the machine learning model's predictions of geothermal gradients.

 

Our results reveal substantial habitable volumes within the lithosphere. The habitable volume in the continental crust may account for about 7% of the total crustal volume, while in the oceanic crust, it could be around 5%. Given the cell density range of 102 to 106 cells per gram in oceanic rocks and 102 to 104 cells per gram in continental rocks, along with an estimated carbon mass of 2x10-14 grams per cell, the lithospheric biomass is estimated to be between 0.008 and 33.2 Gt Carbon. For context, the biomass found in plants and marine microbes is estimated to be around 450 Gt Carbon and 2.9 Gt Carbon, respectively.

How to cite: Zhao, W. and Zhangzhou, J.: Estimating Biomass in the Lithosphere: A Machine Learning Approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13794, https://doi.org/10.5194/egusphere-egu24-13794, 2024.

EGU24-14694 | Orals | GMPV4.2 | Highlight

A decade of the heat-pipe Earth hypothesis 

A Alexander G Webb, William B Moore, Jiawei Zuo, Thomas Müller, Chun'an Tang, Justin I Simon, Peter J Haproff, Chit Yan Eunice Leung, Ariuntsetseg Ganbat, Anthony Ramírez-Salazar, Sandra Piazolo, Qin Wang, Dominik Sorger, Emily J Chin, Tim E Johnson, N Ryan McKenzie, Christopher L Kirkland, H C Jupiter Cheng, and Christoph Hauzenberger

In his classic contribution “A Heat Pipe Mechanism for Volcanism and Tectonics on Venus” [1989, JGR 94, B3, 2779-2785], Turcotte applied O’Reilly and Davies’ [1981, GRL 8, 313-316] model for Io’s volcanic heat transport to Venus, and further speculated that this mechanism might explain a thick lithosphere inferred for Archean Earth. The latter idea – to consider heat-pipe cooling for Earth – then lay fallow until roughly 15 years ago, when one of us (Moore) argued in talks and manuscripts (all rejected) that the cold, thick, and strong lithosphere generated by heat-pipe cooling might offer an alternative to subduction tectonics for generating the “too-cold” Hadean zircons reported by Hopkins et al. [2008, Nature 456, 493-496]. With the additional realization that the heat-pipe cooling mechanism might similarly account for the rocks preserved from the first half of Archean time, the concept of an early heat-pipe Earth finally received broad consideration just over a decade ago [Moore & Webb, 2013 Nature 501, 501-505]. 

Heat-pipe cooling is a hot stagnant-lid cooling mode based on our understanding of the active volcano-tectonics of Jupiter’s moon Io [O’Reilly & Davies, 1981]. Heat-pipes are not plumes: heat-pipes are conduits channeling melts upwards through lithosphere, whereas plumes commonly span the whole crust and mantle and accordingly have relatively complex histories. The heat-pipe Earth hypothesis posits that during the first third of Earth history, rapid volcanism dominated cooling from the end of the magma ocean period to the onset of (episodic?) plate tectonics. During the heat-pipe period, voluminous mafic volcanism resulted in protracted resurfacing, causing quasi-continuous burial of cold, hydrated surface materials that (1) cooled a single-plate lithosphere and (2) generated tonalite-trondhjemite-granodiorite melts deep in the lithosphere. It is noteworthy that the burial of surface materials to mantle depths – long seen as a distinguishing characteristic of plate tectonics – is a hallmark of heat-pipe cooling.   

The past decade has seen abundant explorations and tests of the heat-pipe Earth hypothesis, as well as renewed interest in the heat-pipe cooling mechanism for other terrestrial bodies. This presentation will review major results and consider key critiques. Highlights include demonstrations that heat-pipe cooling viably explains: (a) the early histories of the lithospheres preserved at Mercury, Venus, Mars, and the Moon, and thus can be hypothesized as a universal cooling mechanism for early / hot terrestrial bodies in our Solar System and others [Moore et al., 2017 EPSL 474, 13-19; Peterson et al., 2021 Sci.Adv. 7:eabh2482]; (b) the Eoarchean development of the Isua supracrustal belt of southern West Greenland [Webb et al., 2020 Lithosphere 12, 166-179 and a collection of subsequent works], which was previously understood exclusively via plate tectonic models; (c) the initiation of a global plate network, as thinning and corresponding warming of lithosphere during waning heat-pipe cooling caused thermal expansion which overcame the tensional strength of the lithosphere [Tang et al., 2020 Nat.Comm. 11:3621]; and (d) Earth’s detrital zircon depositional records older than ~3.3 Ga [Zuo et al., 2021 EPSL 575:117182].  

How to cite: Webb, A. A. G., Moore, W. B., Zuo, J., Müller, T., Tang, C., Simon, J. I., Haproff, P. J., Leung, C. Y. E., Ganbat, A., Ramírez-Salazar, A., Piazolo, S., Wang, Q., Sorger, D., Chin, E. J., Johnson, T. E., McKenzie, N. R., Kirkland, C. L., Cheng, H. C. J., and Hauzenberger, C.: A decade of the heat-pipe Earth hypothesis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14694, https://doi.org/10.5194/egusphere-egu24-14694, 2024.

The Son Valley Crystallines (SVC) of the Precambrian Chhotanagpur granite-gneiss complex (CGGC) of the Sonbhadra district Uttar Pradesh contain gneisses and migmatites which are highly deformed and metamorphosed. The study area encompasses different parts of SVC which are Arangapani, Kudri, Anjangira, Jarha, Nawatola, and Naktu. Here we found gneiss and migmatite except Nawatola and Naktu where we found felsic breccia. The foliation in migmatite is E-W but at places it changes to ENE-WSW. The leucosome part of the migmatite occasionally shows pinching and swelling and ptygmatic folding structures. Petrography of the leucosome of this gneiss and migmatite shows the dominance of microcline, orthoclase, quartz, and rare plagioclase with a minor amount of biotite and amphibole whereas the melanosome is dominated by biotite, rarely with amphibole and minor quartz and, feldspars. These rocks contain a higher amount of REE-bearing phases viz. zircon, garnet, apatite, titanite, monazite, and xenotime. The REE-bearing phases particularly zircon, monazite, and xenotime are found as inclusions mostly within biotite and occasionally in feldspars whereas apatite and titanite were found as inclusions exclusively within feldspars. Few zircon and monazite are found in intergranular space between different mineral grains. REE-bearing phases were analyzed in EPMA for total rare earth oxide (TREO) quantification and it was observed that TREO is 0.84 - 1.91 wt% (avg. 1.37 wt%) for apatite and titanite, and for monazite, it is 44.54 - 68.51 wt% (avg. 58.98 wt%). The chemical ages of monazite from Kudri migmatite is 1166 - 748 Ma (avg. 936 Ma; n=10) and Jarha gneiss is 1339 - 837 Ma (avg. 1088 Ma; n=13) these ages coincide with Grenville orogeny (c.1250 - 980 Ma). Hence, REE mineralization in the study area may be the result of the Grenville orogenic event. Most monazite grains are anhedral to elongate in shape and they are found as inclusion in biotite and feldspar however, some of the monazite grains are found in the intergranular space. These two contrasting modes of occurrences of monazite suggest an earlier dominantly of syngenetic (orogenic) mineralization and later with an epigenetic overprint. The geochemical analysis of these rocks shows high SiO2 and low MgO, FeO, and CaO contents indicating a felsic source which is also supported by the TAS diagram in which most of the samples fall in the granite region. The A/NK vs A/CNK plot shows the rocks are peraluminous in nature. The tectonic discrimination diagram of Y vs Nb, Ta+Nb vs Rb, and Yb vs Ta suggests that most of the rock samples fall within the plate field with few in the volcanic arc and few in the syn-collisional setting which indicates the complexity of the terrain.

How to cite: Verma, A. and Chinnasamy, S. S.: The implication of Grenville orogeny on REE mineralization in migmatites and gneisses of Son Valley Crystallines Sonbhadra, Uttar Pradesh, North India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15661, https://doi.org/10.5194/egusphere-egu24-15661, 2024.

EGU24-17273 | ECS | Orals | GMPV4.2

Upper amphibolite- and granulite-facies metabasites: the natural record 

Jacob Forshaw, Eleanor Green, and Pierre Lanari

Upper amphibolite- and granulite-facies metabasites, ubiquitous in Archaean and Proterozoic terranes, represent a critical source of information on the lower continental crust. Elucidating the metamorphism of these rocks provides insights into the processes occurring at depth throughout Earth’s history. However, despite a century of geochemical studies examining high-temperature metabasites in the rock record, several aspects of their phase equilibria remain enigmatic, complicating the development of reliable thermodynamic equations of state for key phases.

This problem exists in part because studies of natural rocks primarily aim to establish the pressure-temperature (P-T) conditions of their respective region. Whilst researchers typically examine the relationship between the geochemical composition of different phases in pursuit of these P-T estimates, observations are necessarily restricted to the bulk composition of their rock and the P-T conditions at which the minerals equilibrated. In contrast, when developing equations of state, a rigorous understanding of how mineral compositions vary for a wide range of pressures, temperatures, and bulk compositions is required. This study lays the groundwork for such an understanding of metabasic phase equilibria by compiling a database of geochemical analyses from studies of natural samples worldwide.

Whole rock compositions, phase assemblages, modal abundances, and mineral compositions have been extracted from over 100 studies in the literature to construct a database containing >1000 samples. First, we determine the median value for and examine the range in the major- and minor-element whole rock composition of metabasites. These values are then compared to several average basalt compositions from the literature. Second, we examine the range and variability in the composition of individual minerals and the partitioning of elements between them. Third, using wet chemical analyses from the database, we test the ability of current ferric iron estimation techniques to reproduce that measured in garnet, orthopyroxene, clinopyroxene, and amphibole. Future work will use this database to test the capability of new thermodynamic equations of state and make it available as a community resource.

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 850530).

How to cite: Forshaw, J., Green, E., and Lanari, P.: Upper amphibolite- and granulite-facies metabasites: the natural record, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17273, https://doi.org/10.5194/egusphere-egu24-17273, 2024.

Monazites crystallize along with silicate minerals, displaying microstructure characteristic of different recrystallization processes. They crystallize as the result of dislocation creep, dissolution creep or dissolution- precipitation creep, depending on pressure-temperature conditions and fluid composition. In dissolution- precipitation creep, newly formed grains replace pre-existing ones and appear as a distinct compositional domain under X-Ray and BSE images. Rock strain-fabric can be correlated with monazite-microstructure and dated using monazite-chemistry. Because it contains a significant amount of Th and U and lacks common Pb and continues to be used for Th-U-total Pb geochronology by chemical analysis in Electron Probe Microanalyser. As the closure temperature of monazite for Th-U-total Pb is ca. 800 °C; each domain retains its age of formation and can be used as geochronometer. Thus, monazite geochronology is used as an effective tool to constrain the timing of fabric development. Fourteen samples of Ambaji granulites of South Delhi Terrane, Aravalli Delhi Mobile Belt, NW India were used for the monazite geochronology and 306 analyses were performed. The microfabric of these samples has been studied to ascertain the category of strain fabric present in them.

The Ambaji granulite comprises pelitic, calcareous, and mafic granulites with several phases of granite intrusions, G0-3. The granulites were deformed by three phases of folding, F1–3, during South Delhi orogeny and marked by a subhorizontal pervasive fabric, S1, axial planar to isoclinal-recumbent F1 folds that developed during granulite facies metamorphism. S1 is overprinted by discrete sets of subvertical shear zones associated with a mylonitic fabric, S2, that were developed axial planar to NE-SW striking upright F2 folds and facilitated exhumation of granulite facies rocks to the upper crust. The shear zones show early history of high-temperature thrust sense shear and late stage low-temperature sinistral shear. The NW-SE striking F3 folds also affected the granulite facies rocks. Brittle strike slip, and normal fault (Sf fabric) that developed post F3, led the final exhumation of the granulite facies rocks to the surface. The S1 monazites are Y-depleted and recrystallized through dislocation creep, and the S2-Sf monazites are Y-enriched and recrystallized through dissolution-precipitation creep. Different monazite population yielded distinct ages of circa 875-857, 834-778, and 764-650 Ma for S1, S2, and Sf strain, respectively, indicating that the South Delhi orogeny spanned 875-650 Ma overlapping with the early phase of the Pan-African orogeny or representing a transition between Grenvillian and Pan-African orogeny.

How to cite: Tiwari, S. K. and Biswal, T. K.: Monazite Geochronology of Deformational Strain Fabric and its Tectonic Implications of the Lower-Middle Crustal Rocks: A Case Study of Ambaji Granulite, NW India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18091, https://doi.org/10.5194/egusphere-egu24-18091, 2024.

EGU24-18431 | ECS | Orals | GMPV4.2 | Highlight

Primordial monazite growth in Archean “metapelites” of the Isua supracrustal belt, southern West Greenland 

Dominik Sorger, Thomas Müller, and A. Alexander G. Webb

We are exploring the origins of some of Earth’s oldest monazite minerals found in the Isua supracrustal belt of southern West Greenland. Monazite is the primary host for light rare earth elements, Th and U, and is a predominant accessory mineral in low Ca granites and metapelites. Its occurrence is controlled by the Al/Ca ratio of the host rock, and at lower metamorphic grade it may be preceded by allanite. Monazite does not form if the Al/Ca ratio falls below a certain threshold.
Rock types with a high Al/Ca ratio suitable for monazite formation are widespread in modern geological settings. Archean rocks, however, typically have a basaltic to ultramafic composition. Even Archean felsic igneous rocks such as TTGs generally exhibit relatively low Al/Ca ratios. Consequently, the composition of most Archean rocks essentially limits the growth of monazite, with apatite, allanite, titanite or zircon being the predominant accessory phases. Nonetheless, the Al/Ca ratio of some rocks must have exceeded the critical threshold during crustal differentiation, allowing the first monazites to be formed. The exact timing of when this happened, and which rocks were involved, is not known. Here we present evidence of very early monazite formation, as discovered in the Isua supracrustal belt (ISB) of southern West Greenland.
The "metapelitic" rock used for this study contains multiphase garnet porphyroblasts and exhibits two generations of monazite. Monazite found in garnet cores yield Th-U-Pb ages of ~3.6 Ga, placing these crystals among the oldest monazites known to date. The younger monazite generation found in the more peripheral parts of the garnet grains and in the rock matrix yields Th-U-Pb ages of ~2.7 Ga. These younger ages are consistent with recently published garnet ages that have been interpreted to record the dominant tectono-metamorphic event of the ISB (Eskesen et al., 2023, Geology 51, 1017–1021). A detrital origin of either monazite generation is unlikely because there are no other known occurrences of monazite in Isua and both monazite generations appear to have formed in their current host rock via a metamorphic overprint.
Due to the rocks’ pelitic bulk composition, they are interpreted as one of the oldest preserved clastic sedimentary rocks, consistent with a provenance consisting of ultramafic, mafic and felsic igneous rocks (Bolhar et al., 2005, GCA 69, 1555–1573). Alternatively, their composition can be interpreted as a metasomatic modification of a basaltic rock (Rosing et al., 1996, Geology 24, 43–46). In either case, the observed ~3.6 Ga monazite indicates a minimum age for the process that led to the high Al/Ca composition of the host rock, which in turn eventually allowed the growth of monazite in the Archean crust of the ISB. As for the hotly-debated matter of whether or not the Isua supracrustal belt hosts late Eoarchean metamorphism, the ~3.6 Ga data appears to potentially represent the first direct-dating evidence in support of this interpretation.

How to cite: Sorger, D., Müller, T., and Webb, A. A. G.: Primordial monazite growth in Archean “metapelites” of the Isua supracrustal belt, southern West Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18431, https://doi.org/10.5194/egusphere-egu24-18431, 2024.

EGU24-18808 | ECS | Posters on site | GMPV4.2

Unravelling the metamorphic history of the Isua supracrustal belt: A garnet-based study in West Greenland 

Julian Wolf, Dominik Sorger, Anthony Ramírez-Salazar, Christoph Hauzenberger, A. Alexander G. Webb, Matthias Willbold, and Thomas Müller

The Eoarchean Isua supracrustal belt (ISB) in West Greenland comprises one of the oldest rock records, yet its geological evolution and geodynamic setting are still debated. Major order questions involve the timing and number of the tectono-metamorphic events leading to the formation of mineral assemblages and structures observed today. Interpreted cross-cutting relationships and crystallization ages of the Ameralik (mafic) dykes have been used to suggest an Eoarchean metamorphic age for the most pervasive event (e.g., Nutman et al., 2004, JGS 161, 421-430). Recent studies, in contrast, argue that this event is Neoarchean in age, as constrained via garnet (-plagioclase-hornblende) dating (e.g., Eskesen et al. 2023, Geology 51, 1017-1021; Ramírez-Salazar et al., unpublished data). In this study, we present data of eight garnet grains from two metapelitic samples from the eastern limb of the ISB to acquire further information about the metamorphic evolution. Both samples share a similar mineral assemblage, featuring a matrix predominantly composed of porphyroblastic garnet with ±chlorite, biotite, white mica, quartz, and ±plagioclase. The garnets exhibit a diversity of unevenly distributed inclusions dominated by quartz, plagioclase, white mica, chlorite, and ilmenite. Additionally, apatite, ±monazite, ±allanite, ±rutile, and ±zircon, as well as some iron-arsenide and -sulphide minerals, are abundant as inclusions. Textural evidence in combination with major and trace element zoning reveals three distinct garnet core to rim domains referred to as garnet I to garnet III. The porphyroblasts’ inclusion-rich cores (garnet I) are characterized by a bell-shaped spessartine component and heavy rare earth element zoning pattern, along with a relatively flat grossular and pyrope pattern. The garnet annuli (garnet II) are grossular-rich, with a constant or slightly increasing pyrope and spessartine components already at their minimum. Garnet II typically exhibits less inclusions. A drop in grossular together with an increase in pyrope components, and the virtual absence of inclusions mark the third garnet domain (garnet III). Our examination of the chemical, mineralogical, and textural characteristics across the different garnet domains reveals the growth of garnet through distinct mineral reactions under variable metamorphic conditions. These domains may be linked to either distinct metamorphic growth stages within a single event or disparate metamorphic events in the tectono-thermal history of the ISB. To unravel the chronological sequence of garnet growth, we present texturally resolved dating of individual garnet domains using the Sm-Nd isochron method.

How to cite: Wolf, J., Sorger, D., Ramírez-Salazar, A., Hauzenberger, C., Webb, A. A. G., Willbold, M., and Müller, T.: Unravelling the metamorphic history of the Isua supracrustal belt: A garnet-based study in West Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18808, https://doi.org/10.5194/egusphere-egu24-18808, 2024.

EGU24-19107 | Posters on site | GMPV4.2

Unsupervised Deep Learning for Rapid Subsurface Interface Identification using Geophysical Measurements 

Zan Wang, Shengwen Qi, Youshan Liu, Bowen Zheng, Peng Sun, and Yu Han

Delineating subsurface interfaces is a crucial step in site selection and characterization for various subsurface applications, such as the geologic carbon sequestration, the radioactive waste disposal and hydrocarbon exploration and production. 3D seismic surveys are widely used for identifying subsurface interfaces and geologic features. Due to the large volumes and the complexity of seismic data, manual interpretation of subsurface interfaces is extremely time-consuming, and the interpretation results can be greatly affected by the subjectivity of a particular interpreter. With the latest advances in deep neural networks (DNNs), automatic seismic interpretation methods based on DNNs emerged. Most of the DNN-based seismic interpretation methods are supervised learning methods, which require large amount of labeled data for network training. We have developed an unsupervised learning method with deep fully convolutional networks (FCNs) for rapid subsurface interface identification based on self-learning algorithms, which does not require manual data labeling and specific training datasets. The characteristics of subsurface interfaces are represented as numerical constraints added to the specially designed loss function for constructing the FCN model. Physical constraints are further applied in postprocessing the outputs of the FCN model to improve the resolution of the identified subsurface interfaces. Application of the unsupervised learning method on a real seismic dataset collected at a potential CO2 storage site demonstrates that the proposed method yields rapid and accurate identification of subsurface interfaces with relatively strong acoustic impedance contrast in seismic images. The proposed approach may assist in automatic subsurface interface identification in real time and facilitate building geological models for subsurface applications.

How to cite: Wang, Z., Qi, S., Liu, Y., Zheng, B., Sun, P., and Han, Y.: Unsupervised Deep Learning for Rapid Subsurface Interface Identification using Geophysical Measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19107, https://doi.org/10.5194/egusphere-egu24-19107, 2024.

EGU24-19290 | Posters on site | GMPV4.2

Amphibolite facies conditions recorded in CO2-bearing fluid-mediated reaction fronts preserved in an ultramafic lens from the Isua supracrustal belt, southern West Greenland 

Thomas Mueller, Julian Wolf, Dominik Sorger, Sandra Piazolo, Christoph Hauzenberger, Jiawei Zuo, and Alexander Webb

The Eoarchean Isua supracrustal belt (ISB) in southern West Greenland exposes one of the oldest rock records on Earth. Its tectono-metamorphic evolution remains debated, particularly with respect to its timing and metamorphic peak conditions recorded by the various mafic to ultramafic lithologies. A first-order question is the presence or absence of metamorphic gradients within the belt. To that end, phase equilibria modelling combined with multiple geothermobarometric data by our group suggested a homogeneous distribution of peak metamorphic conditions (550-600 °C; 0.8-1.0 GPa). However, recent studies of a specific dunite lens from the ISB suggested different metamorphic conditions, varying from ultra-high pressure (UHP) to prograde low-pressure deserpentinization.

In this study, the metamorphism affecting ultramafic rocks from the specified lens B in the northwestern limb of the ISB is investigated along a transect from the rim towards the center of the lens. A total of four samples are examined for their petrography, mineral assemblages, and reaction textures, using EPMA, SEM, EBSD, ICP-MS data together with thermodynamic modelling.

Results reveal a strong foliation in the rim of the lens, with antigorite (XMg=0.91) + magnesite + magnetite ± ilmenite forming the stable assemblage. Deformation decreases towards the center of the lens, where antigorite (XMg=0.98) + fosterite (XMg=0.97) + magnesite + magnetite ± Ti-chondrodite/Ti-clinohumite form the observed assemblage.

The presence of accessory Ti-phases has been used as an indicator for retrograde decompression after UHP metamorphism through the breakdown reaction of Ti-chondrodite to form Ti-clinohumite. We present textural evidence of Ti-clinohumite being replaced by Ti-chondrodite, pointing to a different reaction along a cooling path at lower pressures. The presence of carbonate instead of brucite together with the absence of talc highlights the role of CO2 – which must be assessed to accurately describe phase relations for the metamorphic evolution of ultramafic rocks. Thermodynamic modelling indicates that antigorite stability is strongly CO2-dependent, limiting the stability of antigorite + magnesite to pressures < 1 GPa at XCO2 > 0.005. EBSD analysis reveals clear evidence of olivine experiencing internal deformation, and thus preceding the growth of antigorite in the sample. A second observation further supports this finding: Magnetite, magnesite and Ti-humite phases are spatially associated with olivine breakdown reaction textures.

In summary, this study suggests that UHP conditions or deserpentinization are not required to explain the metamorphic records of these mafic lenses, thus removing a strong argument for the ISB to exhibit a metamorphic gradient and UHP rocks. Instead, we interpret the lens to exhibit a fluid-mediated reaction front that can be readily achieved at the homogeneous, amphibolite-facies conditions reported for the rest of the belt.

How to cite: Mueller, T., Wolf, J., Sorger, D., Piazolo, S., Hauzenberger, C., Zuo, J., and Webb, A.: Amphibolite facies conditions recorded in CO2-bearing fluid-mediated reaction fronts preserved in an ultramafic lens from the Isua supracrustal belt, southern West Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19290, https://doi.org/10.5194/egusphere-egu24-19290, 2024.

EGU24-19548 | ECS | Posters on site | GMPV4.2

Zircon U-Pb and Hf petrochronology of mafic high-grade rocks of a Neoproterozoic nappe system in West Gondwana (Socorro Nappe, SE Brazil) 

Mikaella Balis, Bernhard Schulz, and Mario da Costa Campos Neto

In the Southern Brasília Orogen (south-eastern Brazil), a nappe system that represents the roots of a magmatic arc records HT-UHT metamorphic conditions in lower to mid-crustal rocks. It is divided into two segments by a major shear zone, of which the northern nappe hosts the most extreme metamorphism and has been targeted for most petrochronological studies. These rocks carry insights into the stages of orogeny, as well as the first direct evidence of the paleo-active margin basement, and time-constraint (1) a metamorphism related to the magmatic arc consolidation on the active margin at 670-640 Ma and (2) an enduring UHT event related to collision and decompression at 630-590 Ma. The southern nappe (Socorro Nappe) hosts felsic and mafic granulites, amphibolites and migmatites with intricate occurrences and complex pressure-temperature-time histories that may preserve distinct age populations in the inner nappe and its outward boundaries (Embu Terrane and São Roque Domain). The mafic lower to mid-crustal rocks of the Socorro Nappe lack detailed comprehensive studies of their P-T-t evolution. We present new preliminary LA-ICPMS U-Pb and Lu-Hf systematics in zircon retrieved from metamafic rocks such as granulites, amphibolites and orthogneisses, and partial results on conventional thermobarometry and thermodynamic modelling. We investigate the significance of a wide timespan from ca. 750 to 570 Ma where granulites tend to preserve older ages in contrast to amphibolites. However, Hf signatures are complex and also show a wide range of ε values from 0 to weakly radiogenic, and strongly radiogenic that are not straightforwardly related to a clear time evolution. Herein we discuss preliminary insights into the zircon petrochronology and P-T-t evolution of metamafic high-grade rocks as a tool to unravel the tectonic evolution of the southernmost segment of the Southern Brasília Orogen in relation to the adjacent São Roque Domain and Embu Terrane, in the context of the Western Gondwana amalgamation. 

How to cite: Balis, M., Schulz, B., and Campos Neto, M. D. C.: Zircon U-Pb and Hf petrochronology of mafic high-grade rocks of a Neoproterozoic nappe system in West Gondwana (Socorro Nappe, SE Brazil), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19548, https://doi.org/10.5194/egusphere-egu24-19548, 2024.

EGU24-19592 | ECS | Orals | GMPV4.2

Utilizing Deep Learning to Simulate Transient Fluid Pathways: Integrating 4D Synchrotron Tomography Experiments with Natural Observations 

Hamed Amiri, Ivan Vasconcelos, Evangelos Dialeismas, Damien Freitas, Roberto Rizzo, Florian Fusseis, and Oliver Plümper

Determining the dynamics of fluid-rock interactions is key to deciphering processes in the lithosphere and their importance in industrial applications, including the storage of CO2 and hydrogen, as well as in the development of geothermal energy technologies. Many geological occurrences show that when fluids interact with rocks, they can form their own pathways by developing a temporary network of connected pores as a result of mineral replacement reactions. Nonetheless, following the reaction's cessation, most pores become isolated retarding fluid flow. Here, we investigate transient porosity generation phenomena by conducting 4D (3D plus time) synchrotron tomography experiments using a salt analogue system. To capture the rapid evolution of reaction-induced pore networks, we acquire a full tomography volume every minute. After segmenting this extensive dataset using a deep convolutional neural network, the dynamics of the reaction are quantified by spatiotemporal correlation functions. These high-order statistics enable us to evaluate the evolution of the structural and morphological properties of the induced pore network during the salt replacement reaction. Inspired by image editing techniques in computer vision, we then train a leading-edge generative model, StyleGAN2-ADA (Karras et al., 2020[P(1] ), utilizing the 4D tomography dataset. Our results demonstrate that these advanced generative models can accurately simulate the microstructural evolution observed in the experiment. Next, we delve into the potential of deploying the trained model to reconnect isolated pores observed in data sets of natural mineral replacement reactions. We finally apply a voxel-based finite element method to simulate fluid flow in the salt and natural system. Our deep-learning method not only pioneers in determining transient fluid-rock interaction phenomena, but also, for the first time, enables a direct estimation of reaction-induced permeabilities.

Putnis, A. Mineral replacement reactions. Rev. mineralogy geochemistry 70, 87–124 (2009).

Karras, T. et al. Training generative adversarial networks with limited data. Adv. Neural Inf. Process. Syst. 33, 12104–12114 (2020).

How to cite: Amiri, H., Vasconcelos, I., Dialeismas, E., Freitas, D., Rizzo, R., Fusseis, F., and Plümper, O.: Utilizing Deep Learning to Simulate Transient Fluid Pathways: Integrating 4D Synchrotron Tomography Experiments with Natural Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19592, https://doi.org/10.5194/egusphere-egu24-19592, 2024.

EGU24-777 | ECS | Orals | GMPV4.5 | Highlight

Quantification of the pre-eruptive CO2 budget of Neo-Tethyan magmas and their forcing on Early Cenozoic global climate 

Lea Ostorero, Pietro Sternai, Rosario Esposito, Pierre Bouilhol, Veleda Müller, Nadia Malaspina, Simone Tumiati, Paolo Ballato, Zhiyong Zhang, Wei-Qiang Ji, Jingen Dai, and Maria Luce Frezzotti

Magmatic CO2 emissions can affect the atmosphere composition, thereby driving long term global climate changes. Early Cenozoic climate trends are generally associated with changes in global silicate weathering related to the India-Asia convergence and collision, whereas changes in degassing from Neo-Tethyan magmatic arcs and their likely climatic effects are largely dismissed. Here, we characterize the petrography and measure the volatile content (e.g. CO2, H2O, F, Cl and S) of glassy, bubble-bearing and reheated melt inclusions within quartz, feldspar and pyroxene crystals from Early Cenozoic basalts, andesites and rhyolites from Ladakh (India), Tibet and Iran. Integrating our unprecedented measurements with modeling of the Neo-Tethyan geodynamics, we quantitatively assess the history of magmatic emissions from the Neo-Tethyan arcs and their contribution to Early Cenozoic climate changes. Assessing the Neo-Tethyan magmatic forcing of Early Cenozoic climate has major implications for our understanding of global volatile cycling on geological timescales.

How to cite: Ostorero, L., Sternai, P., Esposito, R., Bouilhol, P., Müller, V., Malaspina, N., Tumiati, S., Ballato, P., Zhang, Z., Ji, W.-Q., Dai, J., and Frezzotti, M. L.: Quantification of the pre-eruptive CO2 budget of Neo-Tethyan magmas and their forcing on Early Cenozoic global climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-777, https://doi.org/10.5194/egusphere-egu24-777, 2024.

EGU24-2162 | ECS | Orals | GMPV4.5

Crustal fluid cycling triggers large-scale melting in Moldanubian migmatites, Bohemian Massif, Czech Republic 

Ina Alt, Elisa Oliveira da Costa, Barbara Kunz, Clare Warren, Pieter Z. Vroon, and Fraukje M. Brouwer

Large granitic batholiths developed in many mountain belts during the late stages of orogenesis. While current melting process research focuses on fluid-absent breakdown of hydrous minerals at amphibolite to granulite facies conditions, petrography, phase equilibrium modelling, and trace element evidence suggests that melt formation due to influx of fluids could be more widespread than previously thought. We investigate Crd bearing diatexites and Kfs bearing migmatitic paragneisses from two locations in the Moldanubian domain of the Bohemian Massif (Czech Republic) for signs of melt formation during water-fluxed or hydrous mineral breakdown melting. We use petrography of thin sections, mineral chemistry by EPMA and trace element compositions from LA-ICP-MS analysis. Samples from Nemojov consist of Crd + Bt + Plg + Qtz + Sill + Ilm ± Kfs and show signs of biotite breakdown to Kfs. It is assumed that pre-existing muscovite was consumed during water-fluxed melting and the subsequent peritectic reaction involves biotite, together with Sill, Plg, and Qtz to form Crd. Diffuse mesosome and leucosome boundaries and the absence of peritectic Kfs suggest water-fluxed melting. The Pohled sample has peritectic Kfs together with Plg + Bt + Ms + Qtz + Ilm ± Grt. This sample has a mm-sized foliation with a clear distinction between melanosome consisting of Plg+ Bt + Ms + Qtz + Ilm and the leucosome comprising Kfs + Qtz ± Grt, reflecting muscovite dehydration melting. Trace element data from both sites show significant differences in Rb, Ba, and Sr, which are dominantly incorporated in micas and feldspars. Variable Rb/Sr ratios can be an indicator for water fluxed melting: since Sr is mainly hosted in Plg and its involvement is stronger during water-fluxed melting, low Rb/Sr values (below 3.5) can be expected in Bt, Plg, and Kfs. This indicates muscovite involvement in Pohled and plagioclase-involvement in the Nemojov samples. Biotite hosts several elements such as LILE and metals like Sc, V, Cr, Co, Ni Nb, Ta, Sn, W. During melting, biotite was consumed via water fluxed melting via the reaction:

Bt + Plg + Sill + Qtz + H2O --> Crd + Melt

Elements like Li and Be are redistributed mainly to Crd, but Rb, Cs, Ba, Sc, V, Cr, Co, Ni, Nb, Ta, Sn, and W were incorporated into the melt (assuming equilibrium between Ilm + Bt). Alkali feldspar and plagioclase have high Ba, Sr, and Pb concentrations, and Zn is enriched in plagioclase. All of this indicates fluid influx, where muscovite released Rb, Cs, and Sn that was taken up by the feldspars. On the other hand, fluid-fluxed plagioclase breakdown resulted in elevated Sr and Ba in biotite and alkali feldspar during melting reactions in Nemojov. Feldspar from Pohled similarly shows high Rb, Sn, and Cs values indicating the influence of muscovite breakdown.

How to cite: Alt, I., Oliveira da Costa, E., Kunz, B., Warren, C., Vroon, P. Z., and Brouwer, F. M.: Crustal fluid cycling triggers large-scale melting in Moldanubian migmatites, Bohemian Massif, Czech Republic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2162, https://doi.org/10.5194/egusphere-egu24-2162, 2024.

Subduction-related dehydration and exhumation-related rehydration play an important role in water recycling on Earth. Water can be transported to the deep mantle through crustal subduction, whereas the behavior of water in the subducted crust during exhumation remains enigmatic. In subduction and exhumation processes, the oceanic crust is transformed into high-pressure mafic granulites and amphibolite through high and low temperature and pressure metamorphism, respectively. During the metamorphism, water can be transported into the deep mantle via subduction-related dehydration and returned to the surface through exhumation-related rehydration processes. As a result, the anhydrous and hydrous minerals are formed within the high-pressure mafic granulites and amphibolites.

In this contribution, we use an integrated micro X-ray fluorescence spectrometry (μ-XRF), transmission terahertz time-domain (THz-TDS), thermogravimetry (TG) and differential scanning calorimetry (DSC) approach on high-pressure mafic granulite and amphibolite to investigate the water species and contents, as well as exhumation rehydration reactions. Our study demonstrates that the high-pressure mafic granulite recorded peak/post peak metamorphism with the formation of Grt + Hbl + Pl + Qtz + Ilm + Ru. Amphibolite experienced retrograde metamorphism with an assemblage of Grt + Hbl + Pl + Qtz. Garnet, hornblende, and ilmenite contain considerable amounts of water as molecular and structural species. Plagioclase contains minor amounts of molecular and structural water. Quartz contains only a minor amount of structural water. Water released from garnet and external fluids from the grain boundary will either migrate into hornblende, plagioclase, ilmenite and quartz, or stored in the mantle wedge, or further subducted into the deep mantle. We suggest that water recycling between the Earth surface and deep mantle is an unequilibrium process, and the lower crust and mantle may store a significant amount of water in deep Earth and can function as a container to feed and maintain the water recycling balance.

How to cite: Li, S.-S. and Qiu, K.-F.: Water content and species in high-pressure granulite: An evaluation based on μ-XRF, THz-TDS spectroscopy, TG and DCS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3126, https://doi.org/10.5194/egusphere-egu24-3126, 2024.

EGU24-3452 | ECS | Orals | GMPV4.5

Magmatic nanogranitoids in the Late Cretacous zircon from Slavonian Mts. (Croatia) 

Petra Schneider and Dražen Balen

Micro-Raman spectroscopy was used to determine the inclusions in early-crystallised magmatic zircon from the Late Cretaceous (~82 Ma on zircon) acidic igneous rocks in the Slavonian Mts. (Mt. Papuk and Mt. Požeška Gora), located in the southwestern part of the Pannonian Basin (Croatia). The host rocks (granite and rhyolite) are predominantly peraluminous and alkali to calcic-alkali and were formed from high-temperature (up to 950 °C), ferroan and oxidised, dry A2-type of magma.

The mineral inclusions detected in the zircon from granite and rhyolites are anatase, apatite, hematite, ilmenite and possibly magnetite. Although anatase is generally considered to form in low-temperature hydrothermal environments and is regarded as metastable, experimental studies in the field of materials science have shown that anatase, compared to rutile, is being stabilised in the systems under a high cooling rate.

Numerous multiphase solid inclusions contain various polymorphs of feldspars (albite, K-feldspar, kokchetavite and kumdykolite) and SiO2 (quartz or cristobalite), hematite and phyllosilicates (kaolinite and muscovite). Such mineral association confirms the existence of an early granitic melt; therefore, this type of inclusion can be regarded as melt inclusions. Melt inclusions with such composition represent nanogranitoids, commonly found in peritectic garnets from high grade metamorphic rocks. Compared to the nanogranitoids of anatectic origin previously reported in partially melted rocks, here they represent primary inclusions of parental magma, i.e. magmatic nanogranitoids, that were protected from later equilibration with the melt or alteration by fluids. Furthermore, here we present the first finding of kokchetavite and kumdykolite in a magmatic zircon. This finding is a strong evidence that kumdykolite and kokchetavite do not require ultra-high pressure (UHP) to form and therefore should not be considered as exclusively UHP phases. Instead, together with anatase, these polymorphs are likely evidence of rapid uplift and consequent rapid cooling of hot oxidised magma generated in the deep (lower) crustal level. The rapid uplift was most likely aided by the weak zones in the continental crust, such as deep faults in a local back-arc extensional (half-)graben in the course of the Late Cretaceous regional geological event associated with the closure of the Neotethys Ocean in the area of the present-day Slavonian Mts.

How to cite: Schneider, P. and Balen, D.: Magmatic nanogranitoids in the Late Cretacous zircon from Slavonian Mts. (Croatia), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3452, https://doi.org/10.5194/egusphere-egu24-3452, 2024.

Yinggehai Basin is an important high-temperature and high-pressure gas producing basin in the South China Sea, and Ledong 8-1 diapir is located in the southeast of the basin, which is the focus of natural gas migration and accumulation. However, the study of fluid inclusions in this gas-bearing structure is not enough, and the accumulation period and accumulation process are not clear, which restricts the progress of exploration in this area. Taking Ledong 8-1 as the research object, this paper uses microscopic lithofacies observation, microscopic temperature measurement of inclusions, laser Raman composition identification, in situ quantitative spectroscopy based on inclusion data to recover paleo-pressure and indirect projection dating of uniform temperature-burial history to identify gas inclusions of different composition types and recover the paleo-pressure evolution history of the Huangliu Formation. The accumulation period and process of natural gas were determined. The results show that there are four types of gas inclusions in Ledong 8-1 diapir, corresponding to three phases of gas charging. The charging time of the first phase of natural gas is 2.2-1.6Ma, the gas composition is mainly CH4, and the pressure coefficient of Huangliu group is 1.13-1.42, indicating weak overpressure. The second phase of natural gas charging occurred at 1.6-0.6Ma, and the gas composition was mainly CO2. Since 0.6Ma, the third stage of natural gas was charged into the formation, and the pressure coefficient of Huangliu formation was as high as 1.8, indicating strong overpressure. It is speculated that the diapiric was opened at this stage, and the natural gas formed in the early stage of Huangliu formation and the newly generated natural gas from deep source rocks migrated upward and adjusted. Studying the fluid inclusions in Ledong 8-1 area of Yinggehai Basin and clarifying the process of gas accumulation in this area is of great significance to the oil and gas exploration in the whole basin, and it is also the key to promote the increase of oil and gas storage and production in the whole basin.

How to cite: Yang, C. and Tian, J.: Fluid inclusions were used to determine gas accumulation period and accumulation process in Ledong 8-1 diapir area of Yinggehai Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4060, https://doi.org/10.5194/egusphere-egu24-4060, 2024.

EGU24-5032 | ECS | Orals | GMPV4.5

Ophicarbonates transport carbon to the deep mantle: a case study from the Zermatt-Saas ophiolite 

Francesca Piccoli, Aaron Hutter, and Jörg Hermann

A large body of work has challenged the paradigm of carbonate stability at the forearc and subarc (> 80 km) conditions in subducted slabs and revealed a variety of complex processes that play an important role in the so-called slow C cycle. Serpentinite-hosted carbonate rocks (i.e., ophicarbonates) are an important rock type for the deep C cycle because they can occur either in the slab or in the mantle wedge. The question revolves around phase stability and metamorphic reactions upon subduction that can lead to a change in carbonate phase assemblage and fluid composition. Moreover, the phase relation between carbonates, silicates, oxide and sulfide minerals in ophicarbonates can be informative about the redox conditions during prograde metamorphism.

We present a case study of ophicarbonate rocks from the Zermatt-Saas unit, Western Alps, that were subducted up to eclogite facies conditions at 2.5 GPa, 560° C. In the study area, ophicarbonates overlie a large body of partially dehydrated serpentinites. This allows us to understand whether fluids released from the serpentinites infiltrated the ophicarbonates or not, and to what extent decarbonation reactions occurred in an open or closed system. We investigated three carbonate-bearing rock types: ophicarbonates, olivine-carbonate veins, and a talc-magnesite reaction rind at the contact between ultramafic and mafic/felsic lithologies. Our petrological and geochemical investigation, as well as thermodynamic modelling, reveal that the metamorphic evolution of the ophicarbonate was in a closed system, where calcite/aragonite was replaced by metamorphic dolomite and diopside, and that this reaction is nearly CO2 conservative, with the released fluid composition close to pure water. In situ LA-ICP-MS trace element analyses also show that carbonate in olivine-carbonate veins was most likely sourced from the ophicarbonates. Our thermodynamic modelling indicates that the talc-magnesite reaction zone was most likely formed during early exhumation between 9-13 kbar and 530-460° C, at XCO2 between 0.007 and 0.009. Lastly, we will discuss how the silicate-oxide-sulfide redox buffering assemblage indicates that all three rock types were equilibrated at redox conditions < FMQ.

In conclusion, our study demonstrates that in the absence of external fluid infiltration, carbonates in ultramafic lithologies are stable at subduction conditions. This suggests that ophicarbonate have a potential important role in the deep, long term, carbon cycle.

How to cite: Piccoli, F., Hutter, A., and Hermann, J.: Ophicarbonates transport carbon to the deep mantle: a case study from the Zermatt-Saas ophiolite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5032, https://doi.org/10.5194/egusphere-egu24-5032, 2024.

Metasomatism, a process whereby infiltrating fluids and melts rich in trace elements and volatiles interact and alter mantle rocks is a common mantle process, as reflected by the mineralogy and chemical composition of mantle-derived samples from all continents. However, the metasomatic agent itself is only rarely available as fluid/melt inclusions for direct analyses; and thus, in many cases, the nature of metasomatism remains elusive.

High-density fluid (HDF) microinclusions in diamonds provide a unique record of the compositions and nature of deep mantle carbon- and water-bearing (COH) fluids. Their high volatile content: 8-20 wt.% H2O and 4-32 wt.% CO2, and their enrichment in incompatible elements make them a key player in mantle metasomatism. The most common HDFs vary in compositions between four major types: silicic, rich in Si, Al, K and water; low- and high-Mg carbonatitic, rich in Ca, Mg, Fe, K and carbonate; and saline, rich in Cl, K, Na and water. Few lines of evidence indicate the relation of saline HDFs and subducted surface material: their K/Cl ratio overlaps the range of altered oceanic crust; pronounced positive Eu and Sr anomalies reflect the involvement of plagioclase during low-pressure crustal processes of protolith formation; and, low 3He/4He isotope ratios (2.7–4.4 Ra) further strengthen a connection with recycled surface material. In addition, recent radiogenic isotope data points to the involvement of distinct mantle sources and subducted components in the formation of varying HDF types. For example, the isotopic composition of silicic to low-Mg carbonatitic HDFs in a suite of diamonds from Canada indicate the contribution of two distinct sources within the continental lithosphere: one with relatively primitive isotopic compositions characterized by εNd of −0.2, 87Sr/86Sr of 0.7044 and 206Pb/204Pb of 17.52, and another with more unradiogenic εNd < −16 and radiogenic 87Sr/86Sr and 206Pb/204Pb > 0.713 and 18.3, respectively. The latter reflects an old metasomatic event in the continental lithosphere involving fluid addition from a subducting slab, most probably in the Paleoproterozoic. In comparison, isotopic compositions of HDFs in South African diamonds suggest that saline HDFs record the involvement of metasomatized Archaean lithosphere and subducting surface material that includes recent sediments.

HDFs are the deepest mantle fluids we have at hand. Due to their high mobility, they can migrate and react with different mantle lithologies over a range of depths. Such HDFs-rock interaction leads to the formation of new metasomatic phases and enriches depleted mantle rocks in volatile and incompatible elements, thereby impacting their density, rheology and melting behavior. Indeed, the mineralogy and chemical composition of xenoliths/xenocrysts and some alkaline magmas suggest a prevalent role of HDFs in mantle metasomatism and deep Earth processes.

How to cite: Weiss, Y.: Micro-windows to deep COH-rich planetary fluids and associated mantle processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5041, https://doi.org/10.5194/egusphere-egu24-5041, 2024.

The continental lithosphere is an enormous reservoir for carbon, but its sequestration and release over geological time are poorly understood. Recent advances indicate that estimates of the amount of carbon released by gradual degassing from the mantle need to be revised upwards, whereas the carbon supplied by plumes may have been overestimated in the past. Variations in rock types and oxidation state may be very local, exerting strong influences on carbon storage and release mechanisms. Deep subduction of thick sedimentary packages may be prevented by diapirism, whereas thinner sequences may be subducted. Carbonates stored in the transition zone melt when they heat up, a process which is recognised by coupled stable isotope systems (e.g. Mg, Zn, Ca). There is no uniform “mantle oxygen fugacity”, and heterogeneous oxidation conditions are likely to exist, particularly at the thermal boundary layer and in the lowermost lithosphere where very local mixtures of rock types coexist. The infiltration of carbonate-rich melts from either subduction or melting of the uppermost asthenosphere leads to trapping of carbon by redox freezing or as carbonate-rich dykes in this zone. Deeply-derived, reduced melts may form additional diamond reservoirs, recognised as polycrystalline diamonds associated with websteritic silicate minerals.

Carbon is released by either edge-driven convection, which tears down sections of the thermal boundary layer and lower lithosphere so that they melt by a mixture of heating and oxidation, or by lateral advection of solids beneath rifts. Both mechanisms are concentrated at changes in lithosphere thickness and result in carbonate-rich melts, explaining the spatial association of craton edges and carbonate-rich magmatism. High-pressure experiments on individual rock types, and increasingly on reactions between rocks and melts, are fine-tuning our understanding of processes and providing unexpected results that are not seen in experiments on single rocks. Future research should concentrate on elucidating local variations and integrating these with the interpretation of geophysical signals. Global concepts such as average sediment compositions and a uniform mantle oxidation state are not appropriate models for small scale processes; an increased focus on local variations will help to refine carbon budget models.

How to cite: Jacob, D., Chen, C., and Foley, S.: Local variations in lithology, thermal conditions and redox state control mechanisms of carbon storage and release in the continental mantle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6836, https://doi.org/10.5194/egusphere-egu24-6836, 2024.

EGU24-7266 | ECS | Orals | GMPV4.5

Machine learning for reconstructing the primary carbon contents of mid-ocean ridge basalts 

Tian-Ting Lei, Jia Liu, and Qun-Ke Xia

One of the primary locations of mafic magma production on Earth is the global mid-ocean ridge system, with basalts erupted from these ridges serving as valuable probes for assessing the compositional variability of the upper mantle and exploring the deep carbon cycle. However, directly measuring carbon contents in mid-ocean ridge basalts (MORBs) has proven challenging due to degassing during magma ascent. Early investigations indicate that some incompatible-trace-element- depleted and -enriched MORBs avoid heavy degassing, and show a narrow range of CO2/Ba ratios, which was generally applied to reconstruct the primitive CO2 content of global MORBs. However, increasing studies reveal significant variability in the CO2/Ba ratios of MORBs. Here, we compiled a dataset including the geochemical compositions of MORB glasses and melt inclusions for which studies supported no significant degassing. Based on it, we constructed a supervised machine learning (ML) model capable of accurately predicting CO2 contents in individual samples using the selected elemental contents. Applying our model to a global MORB database reveals that CO2 contents and CO2/Ba ratios of global MORBs are highly variable, highlighting the significance of mantle heterogeneity, which can be attributed to the interactions with deep-sourced plume, or the recycled components associated with the big subduction zone. Our findings underscore the potential of ML as a powerful tool for uncovering hidden structural patterns in complex geological data, shedding light on the intricate interplay between carbon, mantle composition, and Earth's long-term geological processes.

How to cite: Lei, T.-T., Liu, J., and Xia, Q.-K.: Machine learning for reconstructing the primary carbon contents of mid-ocean ridge basalts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7266, https://doi.org/10.5194/egusphere-egu24-7266, 2024.

EGU24-7404 | Orals | GMPV4.5

Transfer of sulfur and chalcophile metals via sulfide-volatile compound drops in the Christiana-Santorini-Kolumbo volcanic field 

Clifford G. C. Patten, Simon Hector, Stephanos P. Kilias, Marc Ulrich, Alexandre Peillod, Aratz Beranoaguirre, Paraskevi Nomikou, Elisabeth Eiche, and Jochen Kolb

Efficient transfer of S and chalcophile metals through the Earth’s crust in arc systems is paramount for the formation of large magmatic-hydrothermal ore deposits and can strongly affect the Earth’s climate. The formation of sulfide-volatile compound drops has been recognized as a potential key mechanism for such transfer but their fate during dynamic arc magmatism remains cryptic. We report evidence of compound drops preserved in the active Christiana-Santorini-Kolumbo volcanic field. The observed compound drops are micrometric sulfide blebs associated with vesicles trapped within silicate phenocrysts. The compound drops accumulate and coalesce at mafic-felsic melt interfaces where larger sulfide ovoids form. These ovoids are subsequently oxidized to magnetite during sulfide-volatile interaction. Comparison of metal concentrations between the sulfide phases and magnetite allows for determination of element mobility during oxidation. The formation and evolution of compound drops is an efficient mechanism for transferring S and chalcophile metals into shallow magmatic-hydrothermal arc systems.

How to cite: Patten, C. G. C., Hector, S., Kilias, S. P., Ulrich, M., Peillod, A., Beranoaguirre, A., Nomikou, P., Eiche, E., and Kolb, J.: Transfer of sulfur and chalcophile metals via sulfide-volatile compound drops in the Christiana-Santorini-Kolumbo volcanic field, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7404, https://doi.org/10.5194/egusphere-egu24-7404, 2024.

EGU24-7943 | Orals | GMPV4.5

Tracking CO2 mobility during magma-limestone interaction: insights from spectroscopic analysis of experiments 

Frances Deegan, Manfredo Capriolo, Franz Weis, Sara Callegaro, Valentin Troll, Carmela Freda, Valeria Misiti, Lázló Aradi, Henrik Skogby, Herlan Darmawan, and Harri Geiger

Magma-limestone interaction is thought to be an important source of carbon in volcanic arc emissions (1). To better understand the production of volatiles and their behaviour in silicate melts during magma-limestone interaction, we performed Raman and FTIR spectroscopic analysis of bubbles and glasses in the products of a time-series of high pressure-temperature experiments (2). The experiments were designed to simulate entrainment and assimilation of limestone (CaCO3) xenoliths in mafic magma using starting materials from an iconic example of a limestone-hosted arc volcano (Mt. Merapi, Sunda arc, Indonesia) (3). The experimental conditions were T = 1200 °C and P = 0.5 GPa, with run-times ranging from t = 0 s to t = 300 s. Our shortest run-time experiment (t = 0 s) reveals formation of CO2-rich bubbles (± C, CO, N2, H2, H2O, CH4) in and around the magma-limestone reaction site and fast diffusion of CO32- and CO2 molecules throughout the host melt (qualitatively faster than Ca diffusion). Longer run-time experiments (up to t = 300 s) show that bubbles evolved to become larger and richer in CO2 close to the reaction site and that they grew by extracting CO2 from the surrounding melt. Magma-limestone interaction thus rapidly mobilizes CO32- andCO2 and promotes formation of compositionally evolving CO2-rich fluids, which could migrate along fractures, faults, or other fluid escape pathways to contribute to atmospheric fluxes of CO2 at volcanic arcs.

 

References

(1) Mason E., Edmonds M., Turchyn AV (2017) Remobilization of crustal carbon may dominate volcanic arc emissions. Science 357, 290-294, doi: 10.1126/science.aan5049

(2) Deegan FM, Troll VR, Freda C, Misiti V, Chadwick JP, McLeod CL, Davidson JP (2010) Magma-carbonate interaction processes and associated CO2 release at Merapi volcano, Indonesia: Insights from experimental petrology. Journal of Petrology 51, 1027-1051, doi:10.1093/petrology/egq010

(3) Deegan FM, Troll VR, Gertisser R, Freda C (2023) Magma-carbonate interaction at Merapi volcano. In: Gertisser R., Troll VR, Walter T, Agung Nandaka IGM, Ratdomopurbo A (Eds.) Merapi volcano: Geology, eruptive activity, and monitoring of a high-risk volcano (Volcanoes of the World Book Series). Springer Verlag, Berlin, Heidelberg, New York. Chapter 10, 291-321, doi:10.1007/978-3-031-15040-1_10

How to cite: Deegan, F., Capriolo, M., Weis, F., Callegaro, S., Troll, V., Freda, C., Misiti, V., Aradi, L., Skogby, H., Darmawan, H., and Geiger, H.: Tracking CO2 mobility during magma-limestone interaction: insights from spectroscopic analysis of experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7943, https://doi.org/10.5194/egusphere-egu24-7943, 2024.

EGU24-8247 | ECS | Posters on site | GMPV4.5

Linking zircon formation to partial melting events in Kerala Khondalite using nanogranitoids 

Kerstin Gresky, Silvio Ferrero, and Patrick J. O'Brien

The Kerala Khondalite Belt – part of the Southern Granulite Belt of SW India – is well known for its excellent outcrops of metapelites which underwent partial melting during the Panafrican orogeny at lower crustal conditions with temperatures up to 1000°C. Several groups have worked on the metamorphism and petrology of this area which is now complemented by our study of nanogranitoids, i.e., unmodified melt inclusions (MI) of anatectic origin, in zircons from Khondalite. The investigated samples originate from the locations Koliakkode and Pottangodu quarries. Whereas nanogranitoids in peritectic garnets from Koliakkode quarry have already been investigated (Cesare et al., 2009; Ferrero et al., 2012), in Pottangodu we report the first finding of such inclusions.

Preliminary results from optical microscopy investigation reveal that the inclusions are always primary, with an azonal distribution in zircon and a cluster distribution in the garnets from both localities. MicroRaman spectroscopy shows the occurrence of a constant phase assemblage in MI in zircon consisting mainly of kokchetavite, white mica, cristobalite/quartz ± kumdykolite. Phase 430 and phase 412 (both new phases and currently under investigation), carbonate and graphite may be present, in some cases also CO2 and N2. The MI hosted by garnet are quite similar but here we also find biotite in the main assemblage. Additionally, the MI in garnet may contain osumilite, andalusite, apatite and rutile.

In numerous studies by our group we have demonstrated that the identified metastable polymorphs, like kokchetavite (hexagonal k-feldspar), kumdykolite (orthorhombic albite) and cristobalite, are an excellent indicator that melt inclusions are pristine i.e. unadulterated due to decrepitation or by post entrapment infiltration of material along cracks. In order to obtain new data on the pristine melt compositions these nanogranitoids will be then re-homogenized via piston cylinder experiments.

The detailed investigation of these inclusions, coupled with geochronological studies on the host zircon from both localities will unravel the microchemistry of the original unmodified anatectic melt preserved in inclusions, as well as its evolution over time at the host rock scale. In particular, these data will clarify 1) which zircon domains originated before, during and after melt production, as well as 2) the age of the melting event(s?) at HT-UHT conditions. Moreover, to date this represents one of the few examples of anatectic MI in zircons from metamorphic rocks to be investigated in detail via in situ MicroRaman spectroscopy.

References:

Cesare, B., Ferrero, S., Salvioli-Mariani, E., Pedron, D. & Cavallo, A. 2009. Nanogranite and glassy inclusions: the anatectic melt in migmatites and granulites. Geology, 37, 627–630, https://doi.org/10.1130/G25759A.1

Ferrero, S., Bartoli, O., Cesare, B., Salvioli-Mariani, E., Acosta-Vigil, A., Cavallo, A., Groppo, C., Battiston, S., 2012. Microstructures of melt inclusions in anatectic metasedimentary rocks. Journal of Metamorphic Geology, 30, 303–322, https://doi.org/10.1111/j.1525-1314.2011.00968.x

How to cite: Gresky, K., Ferrero, S., and O'Brien, P. J.: Linking zircon formation to partial melting events in Kerala Khondalite using nanogranitoids, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8247, https://doi.org/10.5194/egusphere-egu24-8247, 2024.

EGU24-8477 | Orals | GMPV4.5

High pressure diversity of solid organic compounds in subduction zones, a window to the deep organic carbon cycle. 

Baptiste Debret, Bénédicte Ménez, and Clara Caurant

The nature and the fraction of carbon that are recycled to the deep Earth via the subduction factory remain an active and controversial research frontier. While many studies have attempt to establish the budgets and distribution of inorganic carbon in the subducting slab at high pressure (HP), relatively little is known about the organic counterpart. Here, we explore the nature and diversity of solid organic compounds trapped in HP ultramafic rocks from the Monviso meta-ophiolite. We show that the eclogitic ultramafic rocks record strong variations of redox conditions (i.e., oxygen fugacity, fO2) during subduction. Such variations influenced carbon distribution and redox state. In particular, reducing conditions associated with brucite breakdown in meta-ophicarbonate promoted the formation of an unexpected diversity of abiotic carbon-based materials, ranging from disordered carbonaceous matter and organic minerals, never described in HP environments, to nanodiamonds. These newly-formed organic compounds could subsequently be recycled in the deep mantle, with the potential to play a major role on the deep carbon cycle, therefore calling for a thorough examination of the diversity, abundance and stability of solid organic phases under deep Earth.

How to cite: Debret, B., Ménez, B., and Caurant, C.: High pressure diversity of solid organic compounds in subduction zones, a window to the deep organic carbon cycle., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8477, https://doi.org/10.5194/egusphere-egu24-8477, 2024.

EGU24-9119 | ECS | Orals | GMPV4.5

Carbon and sulfur trapping during contact metamorphism: Impact on volatile transfers in sedimentary basins with magmatic activity, example of the Guaymas Basin. 

Alban Cheviet, Martine Buatier, Flavien Choulet, Philippe Goncalves, Christophe Galerne, Armelle Riboulleau, Wolfgang Bach, and Torsten Vennemann

The opening of sedimentary basins is often accompanied by magmatic activity, and the emplacement of magmatic sills in the sediments. Contact metamorphism at the edges of the sills releases  large amounts of volatiles (H2O, CO2, CH4, and H2S), disrupting the carbon and sulfur cycle within the basin. The volatiles then migrate toward the seafloor and may be released into the oceans and atmosphere. While the reactions of dehydration, decarbonation, and desulfurization during contact metamorphism are well understood, the interactions between the produced fluids and the rocks remain unclear, especially when the fluids remain trapped within the metamorphic aureoles. This study, based on samples collected during the IODP Expedition 385 in the Guaymas Basin, aims to quantify the fluids produced and trapped in the metasediments during the emplacement of magmatic sills. Geochemical and mineralogical characterization of sediments in contact with the sill indicates metamorphic reactions, primarily affecting silica polymorphs (opal-A and opal-CT), diagenetic sulfides (pyrite), and detrital minerals (mainly quartz, clays, and feldspars), and cracking of the organic matter. The transitions from opal-CT to metamorphic quartz and from pyrite to pyrrhotite are good markers of the metamorphic aureoles. The size and the mineralogical assemblages differ in the upper and the lower aureoles suggesting major fluid rock interactions below the sill.  Indeed in this metamorphic aureole, the precipitation of carbonate-pyroxene-pyrrhotite patches within a quartz-plagioclase matrix is a good indicator of fluid-rock interactions at about 200-400°C. These newly formed carbonate patches indicate the trapping of metamorphic fluids below the sill. Isotopic data (δ18O and δ13C) were used to estimate the peak temperature of metamorphism and precipitation of carbonates. Additionally, thermodynamic modeling was conducted to understand the conditions of these reactional textures in the metasediments below the sill and quantify the amount of carbon and sulfur trapped under the sill. We show that a third of the carbon released to the fluid by organic matter cracking is directly trapped under the sill as carbonates. These results indicate that a significant fraction of the carbon initially released upon emplacement of the sill is sequestered deeply and doesn't rise up to the ocean floor.

How to cite: Cheviet, A., Buatier, M., Choulet, F., Goncalves, P., Galerne, C., Riboulleau, A., Bach, W., and Vennemann, T.: Carbon and sulfur trapping during contact metamorphism: Impact on volatile transfers in sedimentary basins with magmatic activity, example of the Guaymas Basin., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9119, https://doi.org/10.5194/egusphere-egu24-9119, 2024.

EGU24-9886 | ECS | Posters on site | GMPV4.5

Sulfur disproportionation in sub-arc COHS slab fluids drives mantle wedge oxidation 

Andrea Maffeis, Maria Luce Frezzotti, James Alexander Denis Connolly, Daniele Castelli, and Simona Ferrando

Sulfur degassed at volcanic arcs calls for dissolved S6+ released by subduction-zone fluids, oxidising (in association with C) the sub-arc mantle, but sulfur speciation in subduction fluids at subarc depths remains unclear. We apply electrolytic fluid thermodynamics to model the dissolution behaviour of pyrite in meta-carbonate sediments as a function of P, T and rock redox state up to 4.3 GPa and 730°C. At subarc depth and at the redox conditions of the fayalite-magnetite-quartz oxygen buffer, pyrite dissolution releases oxidised S in fluids by disproportionation into sulfate, bisulfite, and sulfide species. These findings indicate that oxidised, sulfur-rich COHS fluids form within subducting slabs at depths greater than 100 km independent from slab redox state and that sulfur can be more effective than the concomitantly dissolved carbon at oxidising the mantle wedge, especially when carbonates are stable in the mantle. Further open system modelling shows that such fluids are capable of oxidising the sub-arc mantle within a few million years.

How to cite: Maffeis, A., Frezzotti, M. L., Connolly, J. A. D., Castelli, D., and Ferrando, S.: Sulfur disproportionation in sub-arc COHS slab fluids drives mantle wedge oxidation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9886, https://doi.org/10.5194/egusphere-egu24-9886, 2024.

EGU24-10189 | ECS | Posters on site | GMPV4.5

The C, H2O and S budget of the deep crust (Ossola Valley, Ivrea-Verbano Zone) 

Sarah Degen, Alexia Secrétan, Jörg Hermann, and Daniela Rubatto

The deep crust in the Ivrea-Verbano zone consists of underplated mafic and metasedimentary rocks. In the metasedimentary rocks, C in the form of residual carbonates and graphite, H2O in hydrous phases and S in sulphides can potentially be stored for millions to billions of years. Yet, the budgets of these volatile elements in the deep crust are poorly quantified.

Drill cores obtained from the DIVE-project have been studied for the distribution of C-, H2O- and S-bearing phases in the predominantly felsic metasedimentary upper portion of the lower crust. The drill core samples are mainly biotite-gneisses (75 vol-%, Qtz + Pl + Bt ± Grt ± Sil ± Kfs), metabasites (21 vol-%, Amp + Pl ± Qtz ± Grt ± Px ± Bt) and calcsilicate rocks (2 vol-%, Cc + Grt + Px + Ttn + Pl + Qtz ± Amp) which were metamorphosed at upper amphibolite facies conditions (720-770 ± 50°C at 7.4 ± 1.5 kbar). Varying degrees of partial melting have been observed in all lithologies. Graphite occurs in the matrix of biotite-gneisses and as inclusions in garnet. Moreover, carbonates are present in calcsilicate rocks and occasionally in metabasites. H2O is hosted in biotite and amphibole and S occurs in sulphides.

C-N-S analyses revealed that the biotite-gneisses contain an average of 0.26 wt.-% C while the average values for the metabasites and calcsilicate rocks are 0.07 and 2.22 wt.-%, respectively. The majority of the water is stored in the biotite-gneisses (0.41 wt.-%) and metabasites (0.14 wt.-%). In contrast, the calcsilicate rocks contain negligible amounts of H2O (< 0.004 wt.-%). S concentrations are highest in the biotite-gneisses (0.25 wt.-%) and metabasites (0.19 wt.-%) For the 578.7m deep borehole, overall concentrations reach an average of 0.23 wt.-% C, 0.55 wt.-% H2O and 0.23 wt.-% S.

C mobilisation in the calcsilicate rocks likely occurred via garnet-forming decarbonation reactions (e.g. Zo + Hed + Cc --> Qtz + Grs + H2O + CO2) as well as via melt, which is indicated by the presence of calcite in leucosomes. FTIR spectra of apatite indicate varying concentrations of CO2 which reach 1500 ppm in case of the calcsilicate rocks. Furthermore, apatites hosted by leucosomes contain several hundreds of ppm CO2, indicating the presence of C-bearing hydrous melts. Therefore, devolatilisation reactions as well as partial melting result in a moderate transfer of C and H2O from the deep crust to the upper crust. Nevertheless, metasedimentary rocks that reside at around 25 km depth at temperatures of ~750°C are an important reservoir for C, H2O and S.

How to cite: Degen, S., Secrétan, A., Hermann, J., and Rubatto, D.: The C, H2O and S budget of the deep crust (Ossola Valley, Ivrea-Verbano Zone), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10189, https://doi.org/10.5194/egusphere-egu24-10189, 2024.

EGU24-11595 | Posters on site | GMPV4.5

It’s on the way up! Syn-exhumation paragenesis of glaucophane-phengite-quartz veins 

David Schneider, Taylor Ducharme, Bernhard Grasemann, Michal Bukala, Alfredo Camacho, Kyle Larson, and Konstantinos Soukis

Subvertical glaucophane + quartz ± phengite veins exposed in the footwall of a major extensional detachment on southern Evia (NW Cyclades, Greece) record mode-I brittle fracturing with variable principal stress orientations. The dense network of veins displays systematic cross-cutting relationships with a prominent youngest vein set spaced 5-10 cm apart transecting all other veins. Interlayered jadeite-rich metabasalt and quartzite host the veins and promote a pronounced rheological control on fracturing, with veins preferentially hosted in metabasalt layers and terminating abruptly as pressure solution seams or shear bands at contacts with the ductily deformed quartzite. Vein-hosted ferromagnesian minerals do not exhibit recrystallization or dissolution-reprecipitation microstructures. Jadeite in the metabasalt forms both i) 'fuzzy' euhedral crystals overgrown by hematite and ii) symplectitic intergrowths with quartz and albite. Vein-hosted glaucophane and phengite grew at fixed angles (normal and oblique) to vein walls. Phengite is compositionally homogeneous with elevated Si content (3.41–3.52 apfu). Glaucophane from all veins shows a homologous concentric compositional zoning with core chemistry intermediate between glaucophane and magnesioriebeckite, glaucophane-rich mantles, and rims of magnesioriebeckite or winchite. Phengite yields consistent single-grain total-fusion 40Ar/39Ar dates with a weighted mean of 22 ± 1 Ma (n: 22), whereas the low-K glaucophane produced equivocal and dispersed dates. Phengite (n: 44, 20) and glaucophane (n: 8, 42) in-situ 87Rb/87Sr isochrons from two samples yield mutually indistinguishable dates of 21 ± 5 Ma and 25 ± 4 Ma, within uncertainty of the 40Ar/39Ar dates. The uniform mineral chemistry, compositional zoning, and geochronology indicate that the veins formed over a short time without major shifts in ambient pressure-temperature conditions. Contrary to the apparent mineralogically-defined high pressure-low temperature paragenesis of the veins, dates obtained from pristine high-Si phengite support crystallization in the latest Oligocene to earliest Miocene, coincident with regional extension and widespread greenschist-facies retrogradation in the Aegean. Abundant hematite and the predominance of Fe3+-rich sodic amphibole and clinopyroxene species implicates a highly oxidizing fluid in the stabilization of these nominally ‘high-pressure’ minerals under conditions widely responsible for producing retrogradational greenschist-facies assemblages throughout the Cyclades.

How to cite: Schneider, D., Ducharme, T., Grasemann, B., Bukala, M., Camacho, A., Larson, K., and Soukis, K.: It’s on the way up! Syn-exhumation paragenesis of glaucophane-phengite-quartz veins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11595, https://doi.org/10.5194/egusphere-egu24-11595, 2024.

EGU24-12039 | ECS,ECS | Posters on site | GMPV4.5

Fluid-mediated forearc mantle metasomatism and its chemical feedbacks: Insights from coupled petrological and thermomechanical modelling 

Jun Ren, Manuele Faccenda, Xin Zhong, Matthieu E. Galvez, Jianfeng Yang, and Nicolas Riel

Fluid-mediated mantle metasomatism (FMM) and associated matter transfer is a key process for subduction zone evolution. Over the past decade, the implementation of thermodynamic modelling into geodynamic numerical models became popular, boosting dozens of new insights into ongoing processes within mantle wedge.

Building on the work of Galvez et al. (2015) and Zhong and Galvez (2021), we now combine the original fluid speciation algorithm within a geodynamic model to obtain a chemo-thermo-mechanical modelling platform. It integrates a Gibbs free energy minimizer, e.g. Perple_X or MAGEMin (Connolly et al., 2005; Riel et al., 2022), the ‘single’ backcalculation algorithm (Backcalc, Galvez et al., 2015) with the thermo-mechanical code I2VIS (Gerya and Yuen, 2003) to investigate FMM. Specifically, the speciation and fractionation of electrolytic fluids are governed by cell-wise calculation from Backcalc, and fluid migration is computed assuming incompressible two-phase flow, whereby pore fluid pressure is assumed to be equal to the solid pressure (Faccenda et al., 2009). This new modelling platform is capable of capturing the chemical feedbacks on the geodynamic evolution of subduction zones. Our preliminary efforts have been to replicate the major elements fluxes from a kinematic model presented by Zhong and Galvez (2021) to test the successful combination of the codes. Our ‘benchmark’ tests show excellent agreement. Here, we will present some preliminary tests incorporating mechanical deformations of layers, and how such process, including mantle diapirism, may affect the trajectory of fluids and metasomatic pathways.

How to cite: Ren, J., Faccenda, M., Zhong, X., Galvez, M. E., Yang, J., and Riel, N.: Fluid-mediated forearc mantle metasomatism and its chemical feedbacks: Insights from coupled petrological and thermomechanical modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12039, https://doi.org/10.5194/egusphere-egu24-12039, 2024.

Aqueous fluids are essential agents of mass transport and geochemical cycling in various magmatic, metamorphic orogenic and subduction settings. Thermodynamic properties of aqueous solutes at high pressure have been modelled using several approaches: (1) electrostatic models (Sverjensky et al. 2014), (2) density extrapolations (Wohlers et al. 2011; Manning 2013), or (3) density models (Dolejš and Manning 2010; Dolejš and Salomone 2023). Critical comparison of experimental and predicted mineral solubilities in aqeuous fluids over wide range of temperatures and pressures provides the most accurate constraints on the functional performance of these approaches. This evaluation reveals that (1) electrostatic models offer greater fitting flexibility at costs of extrapolation accuracy and stability across the pressure-temperature space; (2) density models are more robust, require fewer parameters at costs of accuracy at low-temperature conditions. With increasing pressure, the solute concentrations rise and approach the critical transition to hydrous melts. Solute-solvent interaction indicate that mineral-fluid equilibria during critical approach are initially far from congruent and this pressure-temperature region strongly promotes metasomatic effects. The infinite dilution formalism is not physically not suited for reproducing these solubility trends. Instead, thermodynamic description of the critical fluid-melt transition requires consideration of: (1) competing effects of solute polymerization vs. association (hydration) in the dilute region, (2) transition from flexible liquid medium to structured aluminosilicate framework, and (3) speciation mechanism of H2O in aluminosilicate melt. Using the model system H2O-SiO2 we demonstrate coupling between configurational, ideal and excess mixing effects using several molecular and structural formalisms. Use of universal thermodynamic conditions for critical point or curve effectively constrains the location of these phase diagram features and it reduces the number of independent parameters in the mixture equation of state.  In the simplest case, the solubility, melting and critical phase equilibria in the system H2O-SiO2 can be reproduced with a four-parameter equation of state for solute and one interaction parameter. These results reveal diverse heuristic aspects arising from classical thermodynamic constraints and indicate predictive capability and practical accuracy of these models for natural solute-rich fluids in high-pressure settings.

References:  Dolejš D., Manning C.E., 2010. Geofluids 10, 20-40.  Dolejš D., Salomone F., 2023. Proc. 17th Bienn. SGA Meeting 1, 143-146.  Manning C.E., 2013. Rev. Mineral. Geoch. 76, 135-164.  Miron D. et al., 2017. Am. J. Sci. 317, 755-806.  Sverjensky D.A. et al., 2014. Geoch. Cosmoch. Acta 129, 125-145.  Sverjensky D.A., 2019. J. Geol. Soc. 176, 348-374.  Wohlers A. et al., 2011. Geoch. Cosmoch. Acta 75, 2924-2939.

How to cite: Dolejš, D.: High-pressure aqueous systems: experimental constraints and thermodynamic models of fluid-mineral-melt equilibria, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12887, https://doi.org/10.5194/egusphere-egu24-12887, 2024.

Magmatic-hydrothermal ore deposits form in response to metal precipitation from fluids released from crustal magma reservoirs. Following release from the magma, these fluids often go through phase separation involving the condensation of a saline liquid phase (=brine). The brine tends to stay in the deeper part of the hydrothermal system, whereas the vapor ascends to form epithermal ore deposits. Therefore, chemical contrast between these two phases may be deterministic for the spatial distribution of mineralization in magmatic-hydrothermal systems, and also affects volcanic sulfur outputs during quiescent periods. As sulfur is a key constituent for ore metal transport and precipitation, understanding its partitioning between the vapor and brine phases is critically important.

We conducted experiments to determine the effect of oxygen fugacity on the partitioning of sulfur between vapor and brine at P-T conditions relevant for the magmatic-hydrothermal transition by trapping coexisting vapor and brine phases as synthetic fluid inclusions in quartz and subsequently analyzing them for sulfur concentrations by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The results show that at relatively low fO2 at which sulfur is predominantly present in 2- oxidation state, sulfur shows strong preference for the vapor phase with liquid/vapor partition coefficients around 0.2 at a liquid/vapor salinity contrast above a factor of 6. However, with increasing fO2, sulfur partitioning into the liquid phase increases corresponding to the transition of the redox state of sulfur from 2- to 4+ and 6+. In relatively alkaline fluids at the fO2 of the MnO-Mn3O4 buffer, the preferential partitioning of sulfur to the liquid phase is nearly as strong as that of NaCl. Liquid condensation from SO2-rich single-phase aqueous fluid at T = 875oC and P = 200 MPa were observed by in situ Raman spectroscopic experiments and sulfate was identified as the dominant sulfur species in the condensed liquid. It is thus apparent that liquid condensation in oxidized magmatic hydrothermal systems is a redox process that yields sulfate-bearing brines.

A consequence of the above observations is that brines in typical porphyry Cu (-Au) ore forming systems will have the capacity to precipitate ore metal sulfides without externally derived sulfur, provided that some sulfate can be reduced to sulfide and the HCl produced during metal sulfide precipitation is consumed via fluid-rock interaction or is carried away by the vapor phase to higher levels of the system. In addition, a large fraction of the sulfur budget of the primary magmatic volatile phase in oxidized active arc volcanic systems may be stripped by brine condensation during quiescent degassing periods and may never reach the Earth’s atmosphere.

How to cite: Zajacz, Z. and Farsang, S.: Redox dependent sulfur partitioning between liquid and vapor: implications for magmatic-hydrothermal ore genesis and volcanic degassing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13176, https://doi.org/10.5194/egusphere-egu24-13176, 2024.

EGU24-13634 | ECS | Orals | GMPV4.5

Multiphase inclusions in HP rocks (Western Mongolia): Remnants of high saline–CO2 fluids released during deep subduction 

Manzshir Bayarbold, Atsushi Okamoto, Masaoki Uno, Alexey Kotov, Geri Agroli, and Noriyoshi Tsuchiya

Subduction zone fluids play a critical role in the global element cycle. During subduction and progressive heating of the subducting slab, hydrous minerals become unstable, which releases water (Schmidt and Poli 1998). The released water is the trigger for element transport within the subducting slab, along the plate interface, and in the overlying mantle wedge (Bebout 2007). Such released fluid composition has been changed due to fluid-rock interaction during the metamorphism, which has been provided by fluid inclusion behavior in high-pressure (HP) minerals in eclogite facies rock (Bayarbold et al., 2023). Moreover, element mobility along the subduction might be highly dependent on volatile compounds in the metamorphic fluid (Tanis et al. 2016). Related to the size of the trapped fluid and fluid-mineral interaction after being trapped in HP minerals, the reconstructed fluid composition from eclogite facies has not yet been properly quantified. In this study, we report the results of our investigation of fluid inclusions (FIs) in the Khungui eclogite, found in western Mongolia.

Based on the main mineral assemblages of the Khungui eclogite, it can be classified into two types: (i) dry eclogite (<15 vol.% for hydrous minerals) and (ii) wet eclogite (>45 vol.% for hydrous minerals). Numerous primary FIs are present in the omphacite (Omp) from dry eclogite. Omp in dry eclogite is clearly distinguished into two types (Omp1 and Omp2) by their textures. Omp1 occurs within large (up to 100 µm) elongated quartz crystals in the matrix. The fractured Omp1 contains mineral inclusions (amphibole and quartz) and abundant primary FIs. In contrast to Omp1, Omp2 shows an equilibrium boundary with barroisite and garnet in the matrix. Furthermore, no mineral inclusion or FIs occur in Omp2, which is partially replaced by hornblende and plagioclase, whereas Omp1 is not.  FIs in Omp1 consist of variable phases such as liquid, vapor, and several solid phases with various phase ratios. The solid phases in FI within Omp consist of halite (Hl), amphibole, and calcite. These observations reveal that (1) the peak pressure-temperature (P-T) of dry eclogite is higher than the eclogite facies P-T condition of wet eclogite (2.1–2.2 GPa, 580–610°C); (2) high-saline and CO2 saturated fluid interacted with rock at eclogite facies; and (3) Hl in primary FIs in Omp suggests that the salinity of fluid might be up to 26.3 wt.% NaCl equivalent.

How to cite: Bayarbold, M., Okamoto, A., Uno, M., Kotov, A., Agroli, G., and Tsuchiya, N.: Multiphase inclusions in HP rocks (Western Mongolia): Remnants of high saline–CO2 fluids released during deep subduction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13634, https://doi.org/10.5194/egusphere-egu24-13634, 2024.

EGU24-15035 | Posters on site | GMPV4.5

Fluid-driven metasomatism in the mantle wedge: the hidden role of carbon-saturated COH fluids 

Carla Tiraboschi, Dimitri Sverjensky, and Carmen Sanchez Valle

COH fluids have a crucial role in a variety of geological processes in subduction zones, where carbon-bearing aqueous fluids released from the down-going slab infiltrate the overlying mantle wedge prompting metasomatic modifications. Yet, the ability of these fluids to mobilize rock components, and hence their metasomatic potential remains poorly constrained. This is mainly due to the scarcity of experimental data on mineral solubility and fluid speciation in COH-bearing systems at high-pressure conditions. Graphite-saturated COH fluids have been suggested as potentially efficient metasomatic agents, due to their high solute concentrations even at relatively low-pressure conditions. Graphite-saturated COH fluids in equilibrium with forsterite and enstatite can contain up to 11 wt.% of total solutes at 1 GPa and 800 °C, an amount significantly higher compared to the solute content for the same phase assemblage in a H2O-only fluid (i.e. 2.4 wt.%) [1].
Investigating the metasomatic effect of solute-bearing fluids moving away from the source rock and reacting with different lithologies is a complex task. Experimentally, this would require the fluid to be transferred from the initial experimental charge to a different one. However, after quenching most of the dissolved solids originally dissolved in the fluid precipitate. The precipitated solids are both heterogeneous and physically fragile, making their collection and analysis a challenging aspect of the experimental design. Thermodynamic models, such as the Deep Earth Water model [2], allow to tackle the issue from a different perspective and assist in investigating the effect of solute-bearing fluids reacting with different rock assemblages.
Here, we present thermodynamic modeling relative to the interaction between solute-rich COH fluids and mantle wedge rocks (i.e. lherzolite, harzburgite and dunite), to assess their ability to generate orthopyroxene at 1 GPa and temperatures from 700 to 900 °C. Our results show that the fluid generated from the sole dissolution of forsterite and enstatite in graphite-saturated COH fluids at relatively low-pressure conditions can modify the starting ultramafic rock composition, especially at high fluid/rock ratio, through enstatite formation. Fluid-driven metasomatism operated by COH fluids can thus represent an efficient mechanism to produce orthopyroxene-rich levels in the mantle wedge, without the concomitant formation of carbon-bearing phases, which would conceal the trivial role of carbon in the formation of these solute-rich fluids in the exhumed rock record.

[1] Tiraboschi C. et al. (2018) Contributions to Mineralogy and Petrology 173, 1–17.
[2] Sverjensky D.A. et al. (2014) Geochimica et Cosmochimica Acta 129, 125-145.

How to cite: Tiraboschi, C., Sverjensky, D., and Sanchez Valle, C.: Fluid-driven metasomatism in the mantle wedge: the hidden role of carbon-saturated COH fluids, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15035, https://doi.org/10.5194/egusphere-egu24-15035, 2024.

EGU24-15241 | ECS | Orals | GMPV4.5

Melting of hydrous and hydrous-carbonated eclogite in the mantle 

Andrea Curtolo, Pierre Condamine, Nathalie Bolfan-Casanova, Federica Schiavi, and Davide Novella

Water is a key component at Earth’s surface controlling geomorphological processes and establishing an environment capable of supporting life, but it is also present in the mantle as point defects in the lattice of nominally anhydrous minerals (NAMs). Even in trace amounts (i.e., ppm wt), H2O exerts a profound influence on rock properties such as decreasing the melting temperature, which allows melting to occur at much greater depths with respect to volatile-free conditions, impacting the geochemical evolution of the deep mantle. Therefore, precisely modelling melting processes as a function of volatiles content is of great interest in petrology and requires a precise knowledge of the behavior of volatiles at mantle pressure and temperature.

A fundamental parameter used to investigate hydrous melting is the partition coefficient of H2O (DH2Omin/melt = CH2Omin/CH2Omelt), which can be studied at high-pressure high-temperature by performing laboratory experiments. A large number of studies have previously determined the DH2Omin/melt for major mantle phases and mantle conditions in a hydrous system. However, a more comprehensive investigation of the distribution of H2O in the mantle requires also the consideration of CO2, which is the 2nd most abundant volatile in the mantle and is expected to alter the activity of H2O of the system and, consequently, the DH2Omin/melt. Notably, the effect of CO2 on DH2Omin/melt at mantle conditions remains largely unconstrained today.

We present the results of a series of 2 GPa-1200°C piston cylinder experiments investigating an eclogitic system, where clinopyroxene (+garnet) crystals were equilibrated with melt. The experiments were conducted at hydrous and hydrous-carbonated conditions with different amounts of CO2. The experimental charges were recovered, and minerals and melts were investigated by electron microprobe analyses, to determine chemical composition and Fourier Transform Infra-Red and Raman spectroscopy to determine the H2O contents. The experiments highlight a strong effect of CO2 content on decreasing DH2Omin/melt. The new results are used to discuss melting processes interesting eclogitic lithologies in the deep mantle and at representative chemical compositions.

How to cite: Curtolo, A., Condamine, P., Bolfan-Casanova, N., Schiavi, F., and Novella, D.: Melting of hydrous and hydrous-carbonated eclogite in the mantle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15241, https://doi.org/10.5194/egusphere-egu24-15241, 2024.

EGU24-16060 | Posters on site | GMPV4.5

The effects of grain-scale melt migration process on metagranite at eclogite facies,  Bohemian Massif 

Pavla Stipska, Andrew R. C. Kylander Clark, Pavlína Hasalová, and Prokop Závada

Augen to banded metagranite from the Snieznik dome have been modified locally to have stromatic, schlieren, nebulitic and granite-looking textures typical of migmatites. Former presence, and increasing role of melt in transformation towards nebulite is inferred from interstitial phases along grain boundaries in the dynamically recrystallized monomineralic feldspar and quartz aggregates, and from textures of fine-grained plagioclase and quartz replacing K-feldspar. These features are interpreted as resulting from dissolution-reprecipitation along grain boundaries due to grain-scale melt migration, being pervasive at the grain-scale, but localized at hand-specimen to outcrop scales. The new minerals crystallized from melt are in textural equilibrium with phengite. All the rock types have the same mineral assemblage of Grt−Ph−Bt−Ttn−Kfs−Pl−Qz±Rt±Ilm, with similar garnet, phengite and biotite composition, leading to modelled equilibration conditions of 15−17 kbar and 690–740 °C. Because the mineral compositions in the assemblage of interest are independent of the amount of melt, the modelling did not allow to estimate melt quantities in individual rock types. However, migmatite textures suggest that increasing degree of melt-rock interaction occurred from the banded to the schlieren and nebulitic types. The initiation of melt migration is related to gently dipping structures related to continental subduction to eclogite-facies conditions, and more pronounced melt migration is related with vertical fabrics leading to exhumation of the continental subduction wedge from eclogite-facies to mid-crustal conditions.

The effects of melt migration had impact on partial recrystallization of zircon. Zircon in augen to banded types shows oscillatory zoning and gives Cambro-Ordovician age of the protolith. In schlieren to nebulite types, zircon shows domains of blurred oscillatory zoning to structure-less textures. These metamorphic domains are located along grain boundaries, form embayments, form straight or curved linear structures cutting through the oscillatory zoned domains, or are affecting the whole grains. The domains with sharp oscillatory zoning tend to give Cambro-Oridovician ages, while the metamorphic domains tend to give Carboniferous age. Zircon shows numerous apparent “inclusions” of phengite, K-feldspar, quartz, plagioclase, rare garnet, rutile and biotite. However, the “inclusions” of phengite, garnet and rutile are located in the metamorphic domains of the zircon grains. In places, the inclusions are aligned, and these structures are interpreted as former cracks, along which the metamorphic phases crystallized and zircon (re)crystallized. As the assemblage of phengite-garnet-rutile is compatible with previously inferred eclogite-facies conditions, we interpret the Carboniferous zircon (re)crystallization as dating the eclogite-facies grain-scale melt migration process.

How to cite: Stipska, P., Kylander Clark, A. R. C., Hasalová, P., and Závada, P.: The effects of grain-scale melt migration process on metagranite at eclogite facies,  Bohemian Massif, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16060, https://doi.org/10.5194/egusphere-egu24-16060, 2024.

K2O-poor or trondhjemite leucosome is a common feature of migmatites in the Himalayas and other orogens. The origin of K2O-depleted leucosomes has been attributed to several melting scenarios, such as residuum left after melt extraction and magma accumulation. However, the process leading to the formation of leucosome of trondhjemite composition needs to be better understood. In the kyanite zone of the Higher Himalaya Crystallines (HHC) along the Bhagirathi valley, partial melting of metapelite resulted in the formation of two types of leucosomes: K2O enriched granitic L-1 leucosomes formed stromatic veins of variable thickness and K2O poor trondhjemitic L-2 leucosomes occur as patches and lenses. The L-1 leucosomes are characterized by positive and negative Eu anomaly, variable depleted REE content, and represent in-source leucosomes. The L-2 leucosomes are REE depleted, have small negative Eu anomaly (0.8-0.9), and show a clear trend for anatectic melt-residuum-protolith in major-oxide plots of compatible versus incompatible elements. The overall depletion of REE, Sc, V, Cr, Ni, Co, Ti, Th, Nb, Hf, P2O5, and Zr/Zr* <1 in both leucosomes is indicative for disequilibrium melting. Plagioclase composition in the L-1 leucosomes and the associated melanocratic layers show a narrow range for XAb (0.81-0.86). Pl composition measured for two leucosome layers in L-2 leucosomes show near-constant values between XAb =0.81 and XAb =0.85, but the melanosome shows reverse-zoned plagioclase grains with variable XAb (0.69-0.80). Phase equilibria modelling in the system MnNKCFMASTH (Perplex version 7.0.6, thermodynamic database: Holland and Powell (2011)) using the protolith composition correlated to L-2 leucosome shows a clockwise P-T path in the kyanite field. The evolution of melt composition modeled as a function of pressure and X(H2O) at constant temperatures of 690, 710, and 750° C shows that X(H2O) has little to no effect on melt composition. Melting at low pressure produces a granitic composition, and with increasing pressure at constant temperature and X(H2O), melt composition evolves from granite to trondhjemite. The higher the temperature, the smaller the chemical effect.

We conclude that the K2O-poor trondhjemite L-2 leucosomes were produced at incipient partial melting by disequilibrium melting of plagioclase by the reaction Mus + Pl1 (Ab -rich) → melt + Pl2 (Ab-poor). The melt volume is too small to form an interconnected network on which melt could escape, and thus, the melt formed patches and lenses. With increasing temperature, the melting reaction evolved to muscovite dehydration melting, producing a large melt fraction of granitic composition (L-1 leucosome). While previous studies consider K2O poor-leucosomes as residuum melt after melt extraction or represent melt accumulation, we suggest that K2O poor melts could be anatectic melts produced at the beginning of partial melting at high pressure in low melt fractions.

References:

Connolly, J.A., 2005. Earth and Planetary Science Letters236(1-2), pp.524-541.

Holland, T.J.B. and Powell, R.T.J.B., 2011.  Journal of metamorphic Geology16(3), pp.309-343.

How to cite: Kushwaha, A., Singh, S., Putlitz, B., and Baumgartner, L.: Origin of trondhjemite leucosome in a kyanite-grade migmatite from the Higher Himalaya Crystalline (Bhagirathi valley): Insight into leucosome forming processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16973, https://doi.org/10.5194/egusphere-egu24-16973, 2024.

EGU24-17103 | ECS | Posters on site | GMPV4.5

Hydrogen in orthopyroxene records oxidation during hydration of the cold mantle wedge 

María Ramón-Fernández, José Alberto Padrón-Navarta, Françoise Boudier, and Carlos J. Garrido

The mechanisms influencing the oxidation state of arc magmas and their correlation with high volatile content remain highly debated. It has been suggested that the incorporation of hydrogen into Nominally Anhydrous Minerals (NAMs), particularly pyroxenes, in the mantle wedge may play a significant role in the oxidation of arc magmas in subduction zones [1]. To assess this potential link, samples from two contrasting settings were analyzed using infrared spectroscopy (FTIR): [i] ultramafic xenoliths from the Colorado Plateau (CP, USA), representing a unique direct sampling of the cold part of the mantle wedge (< 800ºC), and [ii] reference samples from the Kilbourne Hole (New Mexico), and San Quintín volcanic field (Mexico) which were not directly affected by the fluids responsible for the hydration of xenoliths from CP. 

CP samples exhibit significant lithological variability, ranging from Opx-poor harzburgites to lherzolites and pyroxenites, with hydration levels varying from nominally dry and devoid of hydrated minerals to chlorite-rich samples  (occasionally antigorite), and to a lesser extent, bearing amphibole and Ti-clinohumite. The extent of hydration nicely correlates with the transition from spinel to magnetite. Hydrogen content hosted in NAMs ishigher and more variable in samples from the CP  cold hydrated mantle wedge (Ol: 4-32 and Opx: 146-685 ppm wt% H2O) compared to other localities  (Ol: 0-4 and Opx: 24-209 ppm wt% H2O). Notably, absorption bands exhibit distinct signatures for the two sample groups. Olivines from other localities  display bands related to Ti-defect complexes, while CP olivines also present bands related to Si- and Mg-vacancies. Interestingly, CP orthopyroxene shows distinctive bands (3544, 3520, 3325, and 3060 cm-1) previously observed at relatively high oxygen fugacities [1] consistent with the presence of magnetite in these samples. These bands are absent in samples outside CP. 

These observations suggest that NAMs can serve as sensors of redox processes occurring during the hydration of the cold mantle wedge and that fluids derived from the slabs have sufficiently oxidizing capacity to significantly alter its redox budget [2].

[1] Tollan & Hermann, Nat. Geosci. 12, 667–671 (2019). [2] Evans. Geology 34, 489–492 (2006).

Research funded by RUSTED project PID2022-136471N-B-C21 & C22 funded by MICIN/AEI/10.13039/501100011033

 

How to cite: Ramón-Fernández, M., Padrón-Navarta, J. A., Boudier, F., and Garrido, C. J.: Hydrogen in orthopyroxene records oxidation during hydration of the cold mantle wedge, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17103, https://doi.org/10.5194/egusphere-egu24-17103, 2024.

EGU24-17686 | ECS | Orals | GMPV4.5

Heterogeneous fluid release in subduction zones – evidence from experimental dehydration of brucite vein networks in serpentinite 

Manuel D. Menzel, Lisa Eberhard, José Alberto Padrón-Navarta, Hans van Melick, and Oliver Plümper

Aqueous fluids released by metamorphic dehydration reactions are key components for magmatism, seismicity, creep, and geochemical cycling in subduction zones. How these fluids drain and migrate towards the mantle wedge is not fully understood, partly because the recognition and interpretation of deep fluid pathways in the exhumed rock record is challenging. Serpentinites are among the most important H2O carriers in subducted slabs, with dehydration occurring for example during the lizardite to antigorite transition (ca. 300 – 350 °C), brucite breakdown (ca. 500 °C) and antigorite dehydration (620 – 670 °C). Fluid production and the related formation of interconnected porosity allowing fluid migration are influenced by pre-existing chemical and mineralogical heterogeneities, as well as microstructure and porosity. In oceanic and low-grade metamorphic serpentinites such heterogeneities are very common. To investigate their effect on metamorphic dehydration and fluid migration during subduction to forearc conditions, we experimentally dehydrated natural serpentinite that contains abundant brucite formed during the prograde lizardite–antigorite transformation [1]. In the starting material, brucite occurs as veins and as intergrowths with serpentine in the matrix. We performed piston-cylinder experiments at conditions of brucite dehydration in subduction zones (520 – 570 °C; 1.5 GPa), coupled with micro-tomography (µ-CT), Raman, electron microscopy and microstructural analysis. The experimental results show the formation of olivine as (i) veinlets along the rims of brucite veins, (ii) surrounding and replacing Fe-oxides, and as (iii) tabular grains growing in the serpentinite matrix at the hot spot of the sample cylinder. All olivine types are related to newly formed porosity visible at the resolution of the µ-CT (1.2 µm voxel size). Broad-ion beam polished FE-SEM analysis of the starting material indicates that veins of brucite (± serpentine, Fe-oxides) have significantly more nano-porosity than the serpentine matrix. This observation and the formation of olivine veinlets along the previous brucite vein walls in the experiment suggest that the presence of brucite veins –formed early during shallow forearc metamorphism of serpentinite– will influence fluid production and migration pathways during brucite and antigorite dehydration at deep forearc conditions. Incidentally, our results further demonstrate that preferential dehydration occurs when an external reducing agent (in the case of the experiment H2 most likely derived from the graphite heater) triggers the replacement of serpentine + magnetite by olivine, in line with previous experimental and natural observations [2,3]. Incipient fluid release from serpentinite is thus heterogeneous at the microscale, and will cause local fluid pressure variations that may lead to flow and ultimately drainage. This process, possibly in combination with deformation, deviatoric stress and/or external fluid flux, may favour the development of commonly mono-mineralic olivine veins, which are inferred to form by an interplay of brucite dehydration and reactive fluid flow [4,5].

 

[1] Menzel et al., 2018, Lithos

[2] Eberhard et al., 2023, Journal of Petrology

[3] Padrón-Navarta et al., 2023, Nature Geoscience

[4] Plümper et al., 2017, Nature Geoscience

[5] Huber et al., 2022, G-cubed

 

Funding: M.D.M: Junta de Andalucía (Postdoc_21_00791) and project “RUSTED”, MCIU Spain (PID2022-136471N-B-C21 & 22). LE: NWO (VI.Vidi.193.030), EXCITE (TNA-C3-2023-13).

How to cite: Menzel, M. D., Eberhard, L., Padrón-Navarta, J. A., van Melick, H., and Plümper, O.: Heterogeneous fluid release in subduction zones – evidence from experimental dehydration of brucite vein networks in serpentinite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17686, https://doi.org/10.5194/egusphere-egu24-17686, 2024.

EGU24-17921 | Orals | GMPV4.5

Chlorine cycle in subduction zone settings: insights from chlorine isotopes in olivine-hosted melt inclusions and bulk rocks 

Anne-Sophie Bouvier, Estelle Rose-Koga, Maxim Portnyagin, Alexander Nichols, Stamastis Flemetakis, and Timm John

Chlorine (Cl) is a highly hydrophile and incompatible element which may provide insights into the transfer of elements from the slab to the surface in subduction zone settings. Bulk rocks data have shown that Cl stable isotopes (δ37Cl) are effective tracers of subducted fluids influence in volcanic rocks, with δ37Cl variation up to 3‰ along an arc (Barnes et al., 2009). Nevertheless, a more profound comprehension is needed to identify the specific contributions from the different slab lithologies. Recent advancements in secondary ion mass spectrometry (SIMS) enable precise determination of δ37Cl values at high spatial resolution. In situ measurements of olivine-hosted melt inclusions provide a first order constraint on the δ37Cl of primary magmas since these melt droplets are unaffected by near surface processes.

Chlorine isotopes measurements in melt inclusions from arc samples have revealed large variation within a single rock sample (more than 2‰), and even larger considering melt inclusions from different rock samples along a single arc (up to 5‰). The combination of these data with O and B stable isotopes or with trace elements, measured within the same melt inclusions, suggest that the intra-sample and along-arc variations are related to variable influences of different Cl sources (Bouvier et al., 2019; Bouvier et al., 2022a,b). Indeed, the lowest δ37Cl values (down to -3.4‰) usually reflect the imprint of subducted sediments, whereas the highest δ37Cl values (up to -3.1‰) might reflect the presence of amphibole in the mantle source. Intriguingly, when we compare δ37Cl values from bulk rocks with those obtained in situ in melt inclusions from the same volcano, discrepancies occasionally emerge. These deviations cannot be ascribed solely to instrumental biases. Instead, the difference between bulk rocks and melt inclusions suggests that the latter preserve undegassed signatures which might be lost in bulk rocks. In situ measurement of δ37Cl in melt inclusions can thus be very useful to: (i) better constrain the behavior of Cl and δ37Cl in subduction zone settings, in particular during fluid-rock interaction within the mantle wedge and during degassing, and (ii) track the influence of crystallization/dissolution of Cl-rich minerals in the context of arc magma genesis and differentiation.

 

References:

Barnes et al. (2009), G3, doi:10.1029/2009GC002587; Bouvier et al. (2019), EPSL 507, doi:10.1016/j.epsl.2018.11.036; Bouvier et al (2022a), EPSL 581, doi:10.1016/j.epsl.2022.117414; Bouvier et al. (2022b), Front. Earth Sci., doi:10.3389/feart.2021.793259

How to cite: Bouvier, A.-S., Rose-Koga, E., Portnyagin, M., Nichols, A., Flemetakis, S., and John, T.: Chlorine cycle in subduction zone settings: insights from chlorine isotopes in olivine-hosted melt inclusions and bulk rocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17921, https://doi.org/10.5194/egusphere-egu24-17921, 2024.

Fluid-induced metasomatic changes and origin of patchy charnockite via CO2 influxed dehydration of biotite and amphibole is frequently encountered in different high-grade terrains. The current study reports fluid-mediated transition of garnet-bearing quartzofeldspathic gneiss (GG) to orthopyroxene-bearing quartzofeldspathic gneisses (charnockitic gneisses; CG) from parts of Eastern Ghats mobile belt. Field study reveal that irregular patches of charnockitic gneisses have developed within a foliated garnet-bearing quartzofeldspathic gneiss. The foliation in the garnet-bearing quartzofeldspathic gneiss is continuous and pervasive in the charnockitic gneiss while the contact between the two lithotypes is transitional which advocates for a fluid-induced transformation. Petrography suggest that the peak metamorphic mineralogy in the garnet-bearing quartzofeldspathic gneiss comprises garnet+ plagioclase+ alkali-feldspar (perthite) + quartz+ ilmenite. Garnet (Alm76Py18Gr5Sps1 to Alm68Py26Gr5Sps1) grains in the garnet-bearing quartzofeldspathic gneisses are dominantly anhedral to subhedral, often occur as aggregates and define the melanosomes. Small, polygonal garnet grains often show recrystallized boundaries, indicating presence of deformation. In the charnockitic gneisses, large orthopyroxene (XMg ~0.54 to 0.58; Al: 0.26 to 0.28 a.p.f.u.) grains have inclusions of polygonal garnet grains (Alm68Py28Gr4Sps1)along with ilmenite and quartz. Plagioclase in both the rocktypes are dominantly albitic and plagioclase in garnet-bearing quartzofeldspathic gneiss is more sodic than that of charnockitic gneiss (An31Ab69 in GG and An38-40Ab62-60 in CG). In both the rocktypes biotite develops as secondary minerals replacing both garnet and orthopyroxene.

Reaction modelling suggest the following reactions that possibly led to the development of orthopyroxene:

1.9 Garnet + 8.3 Plagioclase GG + 5.5 Quartz + 3.1 Mg2++ 1 Ca2+ = 4.7 Orthopyroxene + 8.3 Plagioclase CG

The reaction predicts mobilization of Mg and Ca being essential in forming the charnockitic patches.

Conventional geothermobarometry constrain the temperature-pressure conditions of orthopyroxene formation between 800 to 850°C and 7-8 kbar. Pseudosection constructed in NCKFMASHT (Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2) system and the intersection of compositional isopleths of garnet from each rocktypes further yield a similar physical conditions corresponding to the observed mineral assemblages. High metamorphic temperatures also corroborates well with the high Al2O3 (4.30-5.53 wt.%) contents of the orthopyroxene. Mass balance calculations using the whole rock compositions predict extensive mobilization of Mg which corroborates the inference from the modelled reaction. T-XMg and P- XMg diagram indicate that the stability of the orthopyroxene is strongly influenced by XMg rather the physical conditions. T-XH2O diagram further suggest that low H2O (possibly high CO2 or brine-rich) fluids favour the stabilization of orthopyroxene in the observed assemblage and at ~800°C and ~7 kbar, increasing H2O content even up to 2.5 wt.% does not hinder the stability of the orthopyroxene suggesting that temperature and the Mg-influx were the probable parameter that triggered the transition. Low H2O and high CO2 fluid presumably facilitated the process.

How to cite: Mukherjee, S. and Singh, P.: Formation of patchy charnockite from garnet bearing quartzofeldspathic gneiss: evidences of fluid induced metasomatism under granulite facies conditions , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18325, https://doi.org/10.5194/egusphere-egu24-18325, 2024.

EGU24-19855 | ECS | Posters on site | GMPV4.5

Hydrous nano-silicate melt inclusions supports amphibole growth, Persani Mountains Volcanic Field (Transylvania) 

Thomas Pieter Lange, Zsófia Pálos, Márta Berkesi, Péter Pekker, Ábel Szabó, Csaba Szabó, and István János Kovács

Mantle metasomatism plays an important role in the element transport within the Earth’s mantle causing significant change in rheology and geochemistry of the infiltrated region. During volatile-rich fluid-mediated mantle metasomatism, new volatile-rich phases form at the micro- and nanoscale due to fluid-solid interaction. These micro- and nanoscale processes go hand-in-hand but evidence regarding the similarity or difference is scarce. We studied amphibole lamellae and here the connection should be mentioned nano-silicate melt inclusions on clinopyroxene from an amphibole-bearing mantle xenolith from the Persani Mountains Volcanic Field, southeastern Transylvania (Romania) with transmission electron microscopy (TEM).

Based on petrography, post-entrapment interaction occurred between the host clinopyroxene and the trapped CO2-rich fluid in the inclusion, which all was essential to form the amphibole lamellae. According to our observation at the nanoscale, fluid escaped from the fluid inclusion followed by amphibole formation along the clinopyroxene-amphibole interface. The escaped fluid formed nano-silicate melt inclusions (NSMIs) that was studied by TEM. These NSMI consist of ~ 80 v% silicate glass and ~ 20 v% bubble. The composition of the silicate glass is as follows: high SiO2 (>60 wt.%) and Al2O3 (>20 wt.%), whereas low CaO, FeO and MgO (sum <8 wt.%). We calculated the original bulk composition of the nano-silicate melt inclusions with Monte Carlo simulation using hydrated fluid complexes. The results show that the nano-silicate melt inclusions originally had a low SiO2 (~43.5 wt.%) and high Al2O3 (~15.5 wt.%), Na2O (~12.0 wt.%) and H2O (~30.5 wt.%) content.

The composition of the studied nano-silicate melt inclusion suggests that significant compositional change occurs during nano-scale fluid formation from the parent (micron-scale) CO2-rich fluid. Therefore, our results suggest that mineral interfaces play a significant role in hydrous mineral precipitation and growth. Furthermore, we propose that nanoscale processes might play significant role in fluid-poor regions and during and after fluid-mediated metasomatic events within the lithospheric mantle (e.g., H2O, Na, Al consumption during amphibole formation). In addition, the nano-scale fluid migration that we observed here can be one of the mechanisms that enhances deep lithosphere-originated fluid degassing that occurs at many sites on planet Earth. Eventually, our results also provide information about the interactions of H2O globally in the lithospheric mantle where hydrous minerals are stable and along the lithosphere-asthenosphere boundary in younger oceanic and continental plates.

How to cite: Lange, T. P., Pálos, Z., Berkesi, M., Pekker, P., Szabó, Á., Szabó, C., and Kovács, I. J.: Hydrous nano-silicate melt inclusions supports amphibole growth, Persani Mountains Volcanic Field (Transylvania), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19855, https://doi.org/10.5194/egusphere-egu24-19855, 2024.

Boron has two stable isotopes, 10B and 11B, which are strongly fractionated during geological processes. They have been widely used to trace fluids in subduction zones. The temperature-dependent equilibrium boron isotope fractionation depends on boron coordination in the B-hosting minerals and fluids. In blueschist- and eclogite-facies high-pressure metamorphic rocks, omphacite (Cpx), amphibole and white mica are the dominant hosts of B. Yet, different crystallographic mechanisms of B substitution in Cpx have been proposed with first-order implications for B isotope fractionation during slab dehydration and eclogite formation. Hence, clarification of B coordination in clinopyroxene is desired, but a direct determination of boron coordination in silicates at the trace-element level is not technically possible. In this study, we have thus determined the B coordination in omphacite, glaucophane and mica by indirect means through the investigation of the B isotope fractionation in natural rocks.

We investigated a set of six different tourmaline-bearing reaction zone rocks from the high-pressure (HP) mélange on the island of Syros formed at approximately 0.7 GPa, 430 °C. The rocks show the paragenesis tourmaline + phengite + omphacite + glaucophane in textural equilibrium, which offers the opportunity to determine equilibrium B isotope fractionation among these minerals. The proportions of trigonally and tetrahedrally coordinated B in omphacite, glaucophane and phengite was then estimated from the respective boron isotope fractionation against tourmaline. The B isotope fractionation between phengite and tourmaline is -14.7 ±0.6 ‰, and -12.4 ±0.8 ‰ between omphacite and tourmaline. B isotope composition in omphacite is 2.5 ±1.6 ‰ heavier than in phengite. No significant difference was found between glaucophane and phengite. From these results, we conclude that boron in omphacite is dominantly in tetrahedral coordination (84 ±6 % of the total B) with a minor amount of B in trigonal coordination (16 ±6 %).

How to cite: Xu, J., Marschall, H. R., and Gerdes, A.: Boron isotope fractionation during oceanic-crust dehydration in subduction zones: boron coordination in omphacite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19863, https://doi.org/10.5194/egusphere-egu24-19863, 2024.

EGU24-20131 | ECS | Posters on site | GMPV4.5

Preliminary FTIR spectrometry study in a cratonic log: a case study from Jagersfontein mine, South Africa 

Jessy Dominique, Nathalie Bolfan-casanova, and Bertrand Moine

 

Cratonic peridotite xenoliths are unique specimens that allow to constrain the mineralogy of the deep mantle. They are transported at ultrasonic speeds to the surface by volatile-rich kimberlite magmas. Water is an important parameter as it may impact, depending on its concentration, physical parameters such as rheology and partial melting. This study is focused on water content of 12 Spinel and Garnet harzburgites from Jagersfontein mine located at the rim of the Kaapvaal craton. The samples were cautiously selected and are modally non-metasomatized and ultra-refractory peridotites (Fo92-95) with the aim to represent the most preserved archean mantle. Samples originate from 80 to 165 km depth allowing to obtain a continuous monitoring of the cratonic mantle. Water content obtained from FTIR spectroscopy was measured on most representative phases: Ol (15-74 ppm), Opx (70-199 ppm), Gt (3-8 ppm). Orthopyroxene and garnet display a decreasing OH content with increasing depth whereas olivine shows an increase of water content up to 4.5 GPa and then a sudden decrease. The trend shown by olivine [OH] content agrees with olivine data compiled from the literature over decades. The different reasons for explaining such results will be discussed.

How to cite: Dominique, J., Bolfan-casanova, N., and Moine, B.: Preliminary FTIR spectrometry study in a cratonic log: a case study from Jagersfontein mine, South Africa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20131, https://doi.org/10.5194/egusphere-egu24-20131, 2024.

EGU24-20498 | ECS | Posters on site | GMPV4.5

Mineral chemistry and water-rock interaction in exhumed mantle rocks at the Atlantis Massif: Insights from the newly drilled (April-June 2023) IODP Exp. 399 

William Osborne, Ivan Savov, Samuele Agostini, Andrew McCaig, and Emily Baker and the International Ocean Discovery Program Expedition 399 Sci Party

Hydrothermal circulation at slow-ultraslow spreading ridges represents the primary means by which seawater can penetrate the oceanic crust. This process redistributes volatile elements that can be sequestered in hydrous alteration minerals and later remobilised during plate subduction. Accordingly, the hydration state of the oceanic crust fundamentally influences a variety of fluid-mediated processes across subduction zones.

Numerous drill cores penetrate the upper oceanic crust and provide relatively robust constraints on the volatile content of sedimentary and volcanic crustal components. However, very few drill cores sample the lower gabbroic and lithospheric mantle crustal domains, which are rich in hydrous minerals (serpentine, brucite, amphibole, chlorite, talc, zeolites, etc.). This has led to considerable uncertainty regarding the volatile makeup of the crust entering subduction zones, and the behaviour of fluid tracers such as boron and its isotopes.

Lower crustal units are exposed by domal detachment faulting at the Atlantis Massif (30°N; Mid-Atlantic Ridge). We will present preliminary data from IODP Expedition 399, which recovered 1268m of serpentinized mantle peridotite and subordinate gabbroic rocks from the southern wall of the massif, proximal to the famous Lost City Hydrothermal Field. This is by far the longest core ever drilled in situ in serpentinized oceanic peridotite. We will report whole-rock and mineral (serpentine, amphibole, chlorite, prehnite, talc, Cr-spinel, oxide) chemistry in order to investigate the down-hole style of alteration. This will include whole-rock 11/10 B and 87/86 Sr isotope ratios to assess the role of seawater vs. possible ongoing metamorphic alteration at depth. These data represent an important step towards quantifying the fluid mobile element budgets and specifically the boron and 11/10 B content of the lower oceanic crust.

How to cite: Osborne, W., Savov, I., Agostini, S., McCaig, A., and Baker, E. and the International Ocean Discovery Program Expedition 399 Sci Party: Mineral chemistry and water-rock interaction in exhumed mantle rocks at the Atlantis Massif: Insights from the newly drilled (April-June 2023) IODP Exp. 399, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20498, https://doi.org/10.5194/egusphere-egu24-20498, 2024.

EGU24-449 | Posters on site | GMPV4.6

Detailed study of garnet inclusions from the UHP meta-ophiolites of the Western Alps: new petrological constraints on the deep history of a subduction zone 

Federica Boero, Stefano Ghignone, Marco Bruno, Mattia Gilio, Alessia Borghini, and Emanuele Scaramuzzo

The occurrence of Ultrahigh Pressure (UHP) index minerals (i.e., coesite, microdiamond, overall) in tectono-metamorphic belts is of paramount importance to attest the depths attained during subduction of the lithosphere. Recently, many studies focuses on the importance of the inclusions stored in host garnet that preserve information on the trapping conditions (i.e., elastic properties). Detailed inclusions study allows to recognize UHP mineral phases that escaped re-equilibration. Locally, these minerals are no more present in rock matrix, making inclusions the unique evidence of early rock evolution. In this work, we perform a detailed inclusion study through a multi-technique approach to obtain new constraints on the peak metamorphic conditions of a deeply subducted oceanic slab (> 100km).

We focused on two tectono-metamorphic units outcropping in the Western Alps, characterized by a metamorphic peak in UHP conditions. These units belong to the meta-ophiolites of the Internal Piedmont Zone (IPZ) and are located in (i) the Susa Valley (Ghignone et al., 2021), and (ii) Pellice Valley (Colle del Baracun; Ghignone et al., 2023). The units consist of oceanic lithosphere (serpentinite, metagabbro) and metasedimentary cover (micaschist, calcschist). For each unit we selected three samples of Grt-bearing metasediments, making a detailed characterization of the garnet inclusions with optical microscope and micro-Raman spectroscopy. Measured Raman spectra allowed to identify coesite in the Susa Valley (previously unrecognized). We applied Raman-based elastic geothermobarometry (Angel et al., 2015) on quartz and zircon inclusions in garnet as well as Zr-in-rutile thermometry to define the metamorphic path of the units. Furthermore, we combined the distribution of inclusions in zoned garnet with multispectral compositional maps (SEM-EDS), for obtaining a detailed mineral assemblage related to each garnet growth stage.

Our results highlight substantial differences of inclusion mineralogy and their microstructural position within the garnet shells between the two studied units. The IPZ in the Susa Valley recorded (i) the peak-PT under UHP conditions, (ii) a second event under HP eclogitic conditions, and (iii) a late re-equilibration event under LP conditions. Instead, the IPZ in the Pellice Valley recorded i) an early event corresponding to the prograde stage, ii) a peak pressure in UHP conditions, iii) a late re-equilibration event under LP conditions. Despite these differences, the two studied meta-ophiolitic units show similar metamorphic evolutions down to UHP conditions. This evolution follows a similar gradient to that of the coesite-bearing Lago di Cignana unit (e.g., Groppo et al., 2009). This may point out that in the Western Alps three major ophiolite slices underwent UHP metamorphism, thus suggesting that a large volume of oceanic lithosphere was subducted at ca. 100 km depth.

Angel, R., J., Nimis, P., Mazzucchelli, M., L., Alvaro, M., Nestola, F. (2015). J. Metamorph. Geol. 33 (8), 801-813. [10.1111/jmg.12138]

Ghignone, S., Borghi, A., Balestro, G., Castelli, D., Gattiglio, M., Groppo, C. (2021). J. Metamorph. Geol. 39 (4), 391–416. [10.1111/jmg.12574]

Ghignone, S., Scaramuzzo, E., Bruno, M., Franz, A. L. (2023). Am. Mineral. 108, 1368–1375. [10.2138/am-2022-8621]

Groppo, C., Beltrando, M., Compagnoni, R. (2009). J. Metamorph. Geol., 27(3), 207-231. [10.1111/j.1525-1314.2009.00814.x]

How to cite: Boero, F., Ghignone, S., Bruno, M., Gilio, M., Borghini, A., and Scaramuzzo, E.: Detailed study of garnet inclusions from the UHP meta-ophiolites of the Western Alps: new petrological constraints on the deep history of a subduction zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-449, https://doi.org/10.5194/egusphere-egu24-449, 2024.

The area of Mt. Papuk in Croatia, which is protected as a UNESCO Global Geopark due to its exceptional geological diversity, is known for polycyclic metamorphic rocks. The study of metamorphic and igneous rocks demonstrate the occurrence of pre-Variscan, Variscan and Alpine orogenic events. Within the metamorphic lithologies (but also igneous ones, e.g., S-type granite), garnet is a key mineral to decipher details of the geological evolution even if it represents a rock volume of up to 2-3% only. The Variscan orogeny has been recognized here as the most imprinting one producing garnet-bearing medium- to high-grade rocks accompanied by partial melting. This is the only case in the Mt. Papuk area where garnet in metamorphic complex coexisted with melt, i.e. reached high temperatures.

The rock samples (mica schist, gneiss, migmatite) show a schistose fabric and a well-preserved medium to coarse-grained granolepidoblastic texture. Some of the rocks reached high-grade conditions discernible by partial melting. Schistosity is defined by the preferential orientation of elongated feldspar grains, micaceous (biotite and minor muscovite) domains and quartz bands. Feldspar (~40-50 vol%; oligoclase up to 28 mol% An) is the predominant phase, followed by biotite (20-30 vol%), quartz (20 vol%), white mica, reddish garnet and sillimanite (fibrolite). Zircon, apatite, monazite, ilmenite, rutile and titanite are accessory minerals. Monazite grains with high Ce2O3 content (approx. 28 wt%) were dated with the electron microprobe and yielded an age peak at 384.5±9.0 Ma (1σ).

Garnet occurs in almost all quartz- and mica-rich lithologies of the upper amphibolite facies and exhibits two size populations: 1) small, up to 100 μm large and chemically homogeneous (Alm=64, Prp=9, Grs=2 and Sps=25 mol%) garnets that are generally devoid of inclusions except some containing quartz, and 2) 1-2 mm large garnets with a slightly different chemical composition (Alm=66, Prp=12, Grs=2 and Sps=20 mol%) in inner zones containing numerous apatite, rutile, biotite, plagioclase and quartz inclusions. The thin rim of the large garnets corresponds chemically to the composition of the small garnet population.

Using Ti-in-biotite (average 645°C) and garnet-biotite thermometry (590-650°C at 500 MPa) and pseudosection modelling, a clockwise P-T path was reconstructed with maximum pressure conditions within the rutile P-T stability field where the garnet core grew at 800-900 MPa and a temperature of 590-600°C. These conditions were followed by a significant pressure drop, accompanied by melting, partial resorption of garnet and the formation of a thin garnet rim, to 450 MPa (~15 km depth) at temperatures of 680°C.

The geothermobarometric data, additionally constrained by microtextural evidences and mineral stability fields, suggest a convergence-related model reflecting burial, heating and finally rapid (tectonic?) exhumation of the moderately thickened crust. This model suggests a complex tectonometamorphic evolution of the crystalline terrain filling a gap in the Variscan belt between Central and Eastern Europe.

How to cite: Balen, D. and Massonne, H.-J.: Geochemistry and microtextural characteristics of garnet from the Variscan medium- to high-grade metamorphic complex of Mt. Papuk (Croatia), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3436, https://doi.org/10.5194/egusphere-egu24-3436, 2024.

EGU24-3555 | Orals | GMPV4.6 | Highlight

Orogenic treasures: Ziller Valley garnets and their transformation from petrogenetic indicator to gemstone 

Simon Wagner, Roland Köchl, Bianca Zerobin, Peter Tropper, Gert Goldenberg, Gunda Barth-Scalmani, Christoph Hauzenberger, Gerald Degenhart, and Walter Ungerank

Garnet has been utilized for various applications for centuries. It is an important phase for interpreting geological and mineralogical processes due to its wide range of stability and occurrence in various geochemical environments. In the late 18th century, the Zemmgrund in the innermost parts of the Zillertal became an important source of raw material for garnet jewelry. The garnets are found within ductile shear zones in the “Zentralgneisse” of the Venediger nappe system, which is part of the Penninic Tauern Window. There are several comparable shear zones in the innermost Zillertal, with the most relevant for industrial purposes being at the Rossrugg ridge (Zemmgrund). The shear zone rocks can be described as garnet-bearing chlorite mica schists from a petrographic perspective. To better comprehend the deposit's genesis, geochemical composition analyses were conducted on Rossrugg samples using µ-XRF, EPMA, and LA-ICP-MS. The garnet samples exhibit continuous zoning, with the almandine component having the highest proportions of 60 mol% (core) and 73 mol% (rim). The distribution of trace elements, such as Co, Zn, or Zr, correlates with this pattern. In contrast, Ti, HREEs and Y shows a decreasing concentration towards the core. The calculations for garnet formation conditions were performed using Thermocalc v3.45 and TC_Comb, resulting in T=612±34°C and P=7.5±1.4 kbar. The PerpleX and Theriak-Domino software was used to calculate garnet isopleths, which showed that garnet growth occurred at decreasing pressure and increasing temperatures.

This mineral has been utilized by mankind for thousands of years due to its abundance in a wide variety of rocks, especially as a gemstone. Almandine garnets from the Zemmgrund (Ziller Valley, Tyrol) and Radenthein (Carinthia) have played a significant role in jewelry production in the Alpine region since the end of the 18th century. Until the early 20th century, a small industry was established in the Zillertal, which supplied raw materials to Bohemia. Due to the export to Bohemia, the 'Tyrolean' garnets were mixed with the pyropes and lost their identity to some extent. However, there are various methods available to determine the origin of the raw materials used. Besides size and color, another criterion for differentiation is the inclusion pattern of the garnets. For example, Zillertal garnets typically contain chlorite, zircon, apatite, quartz, ilmenite, and epidote as inclusions. In contrast, the garnets from Radenthein exhibit oriented inclusion growth of ilmenite and rutile. However, to clearly differentiate between various garnets from the alpine deposits in a piece of jewellery, destruction-free chemical analyses using suitable methods (e.g. µ-XRF) are necessary. By using PCA and comparing specific oxides (e.g. CaO-MgO), individual deposits can be effectively distinguished. However, local differences, due to different small deposits of the Zemmgrund, presents a challenge as the chemical differences are subtle because of similar geological conditions and little differences in local bulk compositions. Nonetheless, by applying PCA to the collected data, it can be subdivided into five groups, including samples from individual deposits and a warehouse in Zell am Ziller.

How to cite: Wagner, S., Köchl, R., Zerobin, B., Tropper, P., Goldenberg, G., Barth-Scalmani, G., Hauzenberger, C., Degenhart, G., and Ungerank, W.: Orogenic treasures: Ziller Valley garnets and their transformation from petrogenetic indicator to gemstone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3555, https://doi.org/10.5194/egusphere-egu24-3555, 2024.

EGU24-4106 | ECS | Posters on site | GMPV4.6

Mechanisms and durations of metamorphic garnet crystallization in the lower nappes of the Kalak Nappe Complex (Arctic Norway) 

M. Thereza A. G. Yogi, Fred Gaidies, Olivier K. A. Heldwein, and A. Hugh N. Rice

The 3D microstructure and compositional zoning of garnet populations in micaschists from the Kolvik and Bekkarfjord nappes indicate the quasi-equilibration of their major components across the rock matrices during interface-controlled, size-independent garnet growth. There is microstructural evidence for foliation-parallel, small-scale resorption of garnet rims in the Kolvik Nappe, influencing the metamorphic peak conditions obtained from thermodynamic modelling. The local chemical compositions of rims less affected by resorption indicate a peak temperature of c. 630˚C, which is c. 40˚C higher than the temperature obtained from resorbed rims of the largest garnet crystal. The use of a diffusion geospeedometry approach that considers the geometry of the compositional zoning of the entire garnet population, and the higher, more realistic peak temperature, results in an estimated duration of 1 to 4.9 Myr for garnet growth in the Kolvik Nappe. This is approximately one order of magnitude faster than duration estimates calculated when using the apparent, lower temperature obtained from the resorbed garnet rims. Concomitantly to garnet growth in the Kolvik Nappe, garnet overgrowths formed in the Bekkarfjord Nappe for c. 2.5 Myr at metamorphic peak temperatures of c. 560˚C. The garnet growth durations obtained in this work are comparable with the uncertainty on the Lu–Hf garnet–whole-rock isochron ages published previously for the studied rocks (Gaidies et al., 2022). The results provide new insight into the timescales of repeated Barrovian-type metamorphic events experienced by the lower nappes of the Kalak Nappe Complex during the final stages of the Caledonian Orogeny in Arctic Norway.

Reference: Gaidies, F., Heldwein, O. K. A., Yogi, M. T. A. G., Cutts, J. A., Smit, M. A., Rice, A. H. N. (2022). Testing the equilibrium model: An example from the Caledonian Kalak Nappe Complex (Finnmark, Arctic Norway). Journal of Metamorphic Geology, 40(5):859–886.

How to cite: Yogi, M. T. A. G., Gaidies, F., Heldwein, O. K. A., and Rice, A. H. N.: Mechanisms and durations of metamorphic garnet crystallization in the lower nappes of the Kalak Nappe Complex (Arctic Norway), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4106, https://doi.org/10.5194/egusphere-egu24-4106, 2024.

EGU24-5164 | ECS | Posters on site | GMPV4.6

Constraining latent heat of hydration using combined thermal- and garnet diffusion modelling 

Simon Schorn, Evangelos Moulas, and Kurt Stüwe

Hydration and retrogression are common processes in many reworked polymetamorphic terranes. The incorporation of water into a new, hydrated assemblage obliterates precursor high-grade parageneses and releases significant latent heat proportional to the degree of hydration. The hydration of dry gneisses (containing 1–2 wt.% water) at greenschist-facies conditions, may result in an approximate doubling of the bulk water content (4–5 wt.% water). This equates to a gain of 20–40 g of water per kg of retrogressed rock. Considering an average latent heat release of 4 kJ per g of water accommodated in hydrous minerals (Connolly & Thompson, 1989), hydration leads to the release of 80–160 kJ per kg of retrogressed rock. Consequently, this effect causes a significant, albeit short-lived, perturbation of the local thermal conditions. Cooling of the affected rock pile is delayed while the additional energy enhances thermally-activated processes such as diffusive loss of radiogenic Argon. This, in turn, may contribute to a significant rejuvenation of apparent 40Ar/39Ar ages in white mica of up to ~10 % (Schorn et al., 2023). In this study, we present results of multicomponent diffusion modelling of garnets hosted in pervasively hydrated micaschist from the polymetamorphic eclogite-type locality (Koralpe–Saualpe, Austria). Using simple thermokinematic models, we explore exhumation paths that encompass variable degrees and conditions of hydration, along with latent heat to, constrain a set of plausible, yet non-unique, temperature–time histories for the investigated rocks. These cooling paths serve as input for garnet diffusion modelling (Fig. 1), used to determine an appropriate set of thermal parameters for the investigated samples. Our findings contribute to discussions on the broader implications of pervasive fluid–rock interaction in a collisional setting, emphasizing the significance of the often-overlooked effects of retrogression in reworked metamorphic terranes.

Figure 1 - Multicomponent diffusion modelling of a polyphasic garnet. Yellow dots: EMPA data; red line: initial composition; blue line: calculated composition.

Figure 1 - Multicomponent diffusion modelling of a polyphasic garnet. Yellow dots: EMPA data; red line: initial composition; blue line: calculated composition.

REFERENCES

Connolly, J. A., & Thompson, A. B. (1989). Fluid and enthalpy production during regional metamorphism. Contributions to Mineralogy and Petrology, 102(3), 347-366.

Schorn, S., Moulas, E., & Stüwe, K. (2023). Hot when wet: the consequences of exothermic hydration on geochronology (No. EGU23-5769). Copernicus Meetings.

How to cite: Schorn, S., Moulas, E., and Stüwe, K.: Constraining latent heat of hydration using combined thermal- and garnet diffusion modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5164, https://doi.org/10.5194/egusphere-egu24-5164, 2024.

EGU24-5398 | Orals | GMPV4.6

Distinguishing cooling histories via Diffusion Geospeedometry 

Evangelos Moulas and Kurt Stüwe

Extracting apparent timescales or cooling rates of rocks via inverse diffusion modelling allows the testing of geodynamic consequences on the petrological record.  Indeed, inverse modelling of diffusion in minerals such as garnet has been used extensively to constrain thermal history timescales [1] and/or cooling rates [2]. Although inherently such models do not have unique solutions, [3], they can be used to place constraints on the thermal history of rocks and regions [4].

This is interesting because different geodynamic processes will have thermal histories with different attributes [5], in particular qualtiative differences in the shape of cooling curves. In this contribution, we investigate aspects of different apparent cooling rates extracted via inverse diffusion modelling in garnet. Our results suggest a clear distinction in thermal history depending on wether the rocks experienced “active” (driven from tectonic forces) or “passive” (purely conductive) cooling [5]. We emphasize that active cooling implies slow cooling rates at high-grade conditions whereas passive cooling can have very large cooling rates at high-grade conditions (Fig. 1). For petrologic systems with relatively high closure temperatures (>400 °C), the spatially varying aparent cooling rates allow the identification of local heat sources such as intrusions or heat-producing shear zones (Fig. 1). Our results help to identify processes that have transient and local characters such as the thermal affects of heat-producing shear zones and magmatic intrusions.

 

Figure 1 – (a) Thermal histories from rocks in the vicinity of a shear zone, note the higher temperatures experienced by the shear-zone rocks. Such thermal histories will lead to spatial gradients of diffusion relaxation. (b) Absolute cooling rates as a function temperature for the curves shown in (a). The cooling rate versus temperature curve was calculated considering the thermal histories shown in (a) for the time period after 1Myr. (after [2]).

 

REFERENCES

[1] Chakraborty, S. Diffusion in Solid Silicates: A Tool to Track Timescales of Processes Comes of Age. Annu. Rev. Earth Planet. Sci. 36, 153–190 (2008).

[2] Burg, J.-P. & Moulas, E. Cooling-rate constraints from metapelites across two inverted metamorphic sequences of the Alpine-Himalayan belt; evidence for viscous heating. J. Struct. Geol. 156, 104536 (2022).

[3] Moulas, E. & Bachmayr, M. Petrology as an ill-posed inverse problem. in 73 (Mainz Institute of Multiscale Modelling, 2023).

[4] Braun, J., Beek, P. van der & Batt, G. Quantitative Thermochronology: Numerical Methods for the Interpretation of Thermochronological Data. (Cambridge University Press, 2006). doi:10.1017/CBO9780511616433.

[5] Stüwe, K. & Ehlers, K. Distinguishing Cooling Histories using Thermometry. Interpretations of Cooling Curves with some Examples from the Glein-Koralm Region and the Central Swiss Alps. Mitteilungen Österr. Geol. Ges. 89, 201–212 (1998).

How to cite: Moulas, E. and Stüwe, K.: Distinguishing cooling histories via Diffusion Geospeedometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5398, https://doi.org/10.5194/egusphere-egu24-5398, 2024.

EGU24-6665 | Orals | GMPV4.6

Garnet as an archive of fluid flow processes during subduction metamorphism: Evidence from in situ measurement of Li isotopes 

Sarah Penniston-Dorland, Alejandro Cisneros de León, William Hoover, Besim Dragovic, Philip Piccoli, and Christiana Hoff

Fluids released within subduction zones affect fundamental Earth processes, including seismicity and the generation of arc magmas, the formation of continental crust, and the geochemical evolution of the mantle. However, very little is understood about processes of fluid transport within subduction zones. Bulk-rock variations in Li isotopic compositions (δ7Li) are observed in fluid-related features in subduction-related metamorphic rocks at the centimeter-scale suggesting a short duration of fluid infiltration events – weeks to centuries. These measurements capture a time-integrated record, while in situ measurements in metamorphic minerals such as garnet can record individual events experienced by the rock. In our work measuring δ7Li in situ in garnet from several exhumed subduction zone metamorphic localities, we have found variations in δ7Li occurring within crystals over a scale of a few hundred microns, including troughs of negative values of δ7Li. Variations in δ7Li are associated with evidence for fluid release and fluid-rock reaction suggesting a role for fluids fluxing through the slab. The negative δ7Li excursions suggest that diffusion played a role in the history recorded by these garnets - in some cases garnet experienced intracrystalline diffusion of Li on the scale of a few hundred microns, and in others garnet growth zones incorporated variations of δ7Li within the metamorphic fluid surrounding the garnet, caused by diffusion of Li within the intergranular fluid on at least a centimeter scale. Multiple troughs in some of the garnets record the episodicity of fluid flow. Ongoing work is focusing on investigating garnets from a wide range of natural samples to look for patterns in fluid flow episodicity. Additionally, experiments determining the diffusivity of Li within garnet are being performed in order to quantitatively constrain timescales of intracrystalline diffusion.

How to cite: Penniston-Dorland, S., Cisneros de León, A., Hoover, W., Dragovic, B., Piccoli, P., and Hoff, C.: Garnet as an archive of fluid flow processes during subduction metamorphism: Evidence from in situ measurement of Li isotopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6665, https://doi.org/10.5194/egusphere-egu24-6665, 2024.

EGU24-6669 | ECS | Posters on site | GMPV4.6

P-T conditions of high- and ultrahigh-pressure metamorphism along the Western Gneiss Region, Norway 

Olga Turek, Karolina Kośmińska, Jarosław Majka, Mattia Gilio, Iwona Klonowska, Alessia Borghini, Adam Włodek, Daniel Buczko, and Simon Cuthbert

The Western Gneiss Region (WGR) is a well-known UHP metamorphic terrane in SW Norway, where eclogite bodies crop out among gneisses. These rocks experienced high- and ultrahigh-pressure (HP-UHP) metamorphism during the Caledonian Orogeny and display pressure-temperature (P-T) gradient increasing from the south to the north (e.g., Cuthbert et al., 2000). Eclogites from nine localities along the entire length of WGR, namely Drøsdal, Vårdalsneset, Verpeneset, Halnes, Saltaneset, Grytting, Ulsteinvik, Solholm, and Juvika, have been chosen for P-T condition estimates. Here we present a reevaluation based on the new geothermobarometric techniques in the WGR regional study.

Eclogite varies in the amount of amphibole, kyanite, phengite, zoisite, and inclusions of quartz and rutile in garnet. Phengite occurs mainly in the eclogites in the south, whereas those from the north contain orthopyroxene. Garnet in the south is almandine-rich with the average composition of Alm0.41–0.57Grs0.15–0.31Prp0.10–0.37Sps0.01–0.07, with increasing Mg in the rims and often showing complex compositional zoning. Garnet from the other localities is homogenized and dominated by pyrope with the composition of Prp0.41–0.56Alm0.33–0.46Grs0.09–0.13Sps0.01–0.04. Clinopyroxene in the northern part is poorer in jadeite component with XNa=0.20-0.29 and XFe=0.12-0.17 than clinopyroxene in the south with XNa=0.40-0.52 and XFe=0.12-0.19. Silicon in phengite is up to 3.30 atoms per formula unit (apfu) in most localities, with a maximum of 3.48 apfu in the Verpeneset locality.

Coesite and polycrystalline quartz inclusions in garnet, evidence of UHP metamorphism, are typical of Saltaneset and Verpeneset localities, which is also validated by thermobarometric calculations. We estimated the peak P-T equilibration condition by Grt-Cpx-Phe thermobarometry, Ti-in-Quartz and Zr-in-Rutile thermometry, along with Quartz-in-Garnet elastic geobarometry. Preliminary estimates give slightly higher P values than previously reported in the two southernmost localities Drøsdal and Vårdalsneset [720-830°C and 1.9-2.1 GPa (Foreman et al., 2005), 635°C and 2.3 GPa (Engvik et al., 2007), accordingly] yielding the peak conditions of 680-740°C and 2.7-2.85 GPa. The obtained results from other localities give P conditions close to the boundary of quartz and coesite stability fields and T in the range of 650-750°C, with the highest P of 3.28 GPa in the Verpeneset locality. The highest T of 875°C has been obtained in Ulsteinvik locality. Those results may help refine previous studies and understand the history of the WGR.

This work was funded by the National Science Centre of Poland project no. 2021/43/D/ST10/02305.

 

References:

Cuthbert, S.J., Carswell, D.A., Krogh-Ravna, E.J., Wain, A. (2000). Eclogites and eclogites in the Western Gneiss Region, Norwegian Caledonides. Lithos, 52 (1–4), 165-195.

Foreman, R., Andersen, T.B., Wheeler, J. (2005). Eclogite-facies polyphase deformation of the Drøsdal eclogite, Western Gneiss Complex, Norway, and implications for exhumation. Tectonophysics, 398, 1-32.

Engvik, A.K., Andersen, T.B., Wachmann, M. (2007). Inhomogeneous deformation in deeply buried continental crust, an example from the eclogite facies province of the Western Gneiss Region, Norway. Norwegian Journal of Geology, 87, 373-389.

How to cite: Turek, O., Kośmińska, K., Majka, J., Gilio, M., Klonowska, I., Borghini, A., Włodek, A., Buczko, D., and Cuthbert, S.: P-T conditions of high- and ultrahigh-pressure metamorphism along the Western Gneiss Region, Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6669, https://doi.org/10.5194/egusphere-egu24-6669, 2024.

EGU24-8683 | ECS | Posters on site | GMPV4.6

High-P metamorphism in the Mesoproterozoic: Petrochronological insights from the Grenville Province 

Caroline Lotout, Aphrodite Indares, Jeffrey Vervoort, and Etienne Deloule

In the Grenville Province, high-P rocks that are discontinuously exposed along the margin of the allochthonous belt preserve the record of deep crustal processes and are an essential puzzle piece to understanding Mesoproterozoic geodynamics. The Manicouagan Imbricate zone (MIZ) is one of the three high-P domains from the Grenville Province. It is located in the Central Grenville between the Parautochthonous Belt to the North and the orogenic hinterland to the South, that were metamorphosed during the 1005–980 Ma Rigolet and 1080–1020 Ma Ottawan orogenic phases, respectively. In the western MIZ, the Lelukuau Terrane (LT) mostly consists of Labradorian-age (~1650 Ma) mafic suites with a fringe of aluminous rocks at its southern edge. Metamafic samples from the Western and Eastern parts of the MIZ display a peak assemblage of garnet, clinopyroxene, plagioclase, rare pargasite or edenite, and quartz ± kyanite. Pseudosection modelling suggests high-P granulite peak conditions at ca. 14 to 16 kbar and 800–900°C, with the scarcity of hydrous phases and quartz explaining the lack of evidence for partial melting. Zircon cores from the Western LT sample show a maximum magmatic age of ca 1.6 Ga. Lu–Hf and Sm–Nd dating on garnet from this sample yield ages of 1020 ± 7 Ma and 1005 ± 13 Ma, respectively, overlapping within error and inferred to represent peak metamorphic conditions followed by fast cooling. In the Eastern LT sample, garnet Lu–Hf dating yields two ages that are consistent with a petrographically preserved two stage growth, at 1033 ± 6 Ma and 1013 ± 6 Ma, while the Sm–Nd age indicates cooling at 1003 ± 8 Ma. The recorded high-P granulite facies conditions highlight a late Ottawan to Rigolet-age localized crustal thickening at the margin of the hinterland during the propagation of the orogen to the NW, with a possible younging of the high-P granulite-facies metamorphism from the Eastern to Western LT. These new results indicate that the high-P belt in the Central Grenville does not represent the exhumed base of an Ottawan age orogenic plateau, as previously proposed, and that no tectonic hiatus exists between the two orogenic phases, as generally thought. Finally, this publication highlights the diversity and diachronicity of the high-P domains in the Grenville Province.

How to cite: Lotout, C., Indares, A., Vervoort, J., and Deloule, E.: High-P metamorphism in the Mesoproterozoic: Petrochronological insights from the Grenville Province, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8683, https://doi.org/10.5194/egusphere-egu24-8683, 2024.

EGU24-8787 | Posters on site | GMPV4.6

Fluid-melt immiscibility during lower crustal melting recorded in the orthogneiss of Punta de li Tulchi,  Sardinia (Italy). 

Silvio Ferrero, Gabriele Cruciani, Marcello Franceschelli, Dario Fancello, Leila Rezaei, and Kerstin Gresky

Garnet in high grade rocks often contains primary melt (MI) and fluid inclusions (FI), fundamental to reconstruct the suprasolidus history of the rocks in which it occurs. MI and FI-bearing garnets have been recently found at Punta de li Tulchi, on the NE coast of Sardinia, Italy. They were identified in a single, decimetre-thick leucocratic body of overall granitic composition, hosted in migmatitic orthogneiss. Whereas in the host rock garnet is generally rare or absent, in the leucocratic body it reaches up to 5 vol% and occurs as subhedral grains up to several mm in size. Garnet composition is mainly almandine-spessartine (Alm60-70, Sps20-30 Pyr~7 Grs~3).

The inclusions occur in clusters in the inner part of the garnet, i.e., they are primary in nature and therefore trapped during garnet growth. A preliminary investigation via optical microscopy and MicroRaman Spectroscopy (MRS) shows the presence of (at least) two types of inclusions. Type 1 inclusions are polycrystalline, ≤30 microns in size, and contain cristobalite +white mica ±carbonate, an assemblage overall consistent with their interpretation as nanogranitoids, or crystallized melt inclusions of anatectic origin. Type 2 inclusions contain two phases, i.e., liquid and vapour (70-30 vol% approximately). MRS display the presence of liquid H2O and a CH4-rich bubble, with minor amounts of CO2 and N2 detected in some cases. Often type 2 inclusions are characterized by the presence of a carbonate – either ankerite (CaFe carbonate) or rhodochrosite (Mn carbonate), based on the features of its Raman spectrum.

Previous studies in the area suggest that these crustal rocks underwent high T metamorphism and re-melting in presence of fluid at 1.0 -1.1 GPa (Fancello et al., 2018) during the Variscan orogeny. The finding of melt-bearing garnets suggests that anatexis here also involved dehydration melting, at least locally, with formation of peritectic garnet. Moreover, this took place under conditions of primary fluid-melt immiscibility, as testified by the coexistence of MI and FI in the same cluster, a feature already found in many other nanogranitoid studies (see Ferrero et al., 2023). Finally, this is the first case study where nanogranitoids are found in almandine-spessartine garnet rather than in almandine-pyrope.

References

Fancello, D., et al. Trondhjemitic leucosomes in paragneisses from NE Sardinia: Geochemistry and P-T conditions of melting and crystallization. Lithos, https://doi.org/10.1016/j.lithos.2018.02.023

Ferrero, S., et al. H2O and Cl in deep crustal melts: the message of melt inclusions in metamorphic rocks. EJM, https://doi.org/10.5194/ejm-35-1031-2023

How to cite: Ferrero, S., Cruciani, G., Franceschelli, M., Fancello, D., Rezaei, L., and Gresky, K.: Fluid-melt immiscibility during lower crustal melting recorded in the orthogneiss of Punta de li Tulchi,  Sardinia (Italy)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8787, https://doi.org/10.5194/egusphere-egu24-8787, 2024.

EGU24-9255 | ECS | Orals | GMPV4.6

Mineral inclusions under non-ambient conditions 

Nicola Campomenosi, Ross John Angel, Matteo Alvaro, and Boriana Mihailova

Mineral inclusions represent a real treasure in earth sciences because of their large range of applicability to unravel metamorphic and geodynamic processes. For instance, the contrast in the thermal expansion and compressibility coefficients between a mineral inclusion and its surrounding host leads to a residual pressure in the inclusion (Pinc) that, once determined at ambient conditions, can be used to back-calculate the pressure and temperature of entrapment (e.g. Rosenfeld and Chase, 1961; Angel et al. 2015). The Pinc can be quantified via in situ Raman spectroscopy, using ab initio calibrations (e.g. Murri et al. 2018). In addition, Raman spectroscopy can be used to explore the evolution of residual pressure in mineral inclusions under non-ambient conditions. We have analysed quartz-in-garnet (QuiG) host-inclusion systems in situ under high external pressure applied with a diamond-anvil cell at room temperature. The evolution of quartz Pinc calculated from the Raman data collected on fully encapsulated inclusions at high pressure agrees with the predictions calculated from the equations of state and confirm that the garnet host acts as a pressure shield to the softer quartz inclusion. The pressure-dependent sharpening of the A1 mode near 207 cm-1 indicates that quartz inclusions become metastable against coesite at values of Pinc of ~ 2.4 GPa, which corresponds to the pressure of the quartz-coesite phase boundary at room temperature of free crystals (Bose and Ganguly 1995). However, the external applied pressure may exceed the Pinc of more than 2 GPa. Finally, we show that “partially” encapsulated inclusions undergo significant non-hydrostatic stress with evident symmetry-breaking due to heterogeneous host-shielding effects. At room temperature, such deviatoric stresses do not affect the metastability of quartz inclusions with respect to coesite.

Financial support by the Alexander von Humboldt Foundation to N. Campomenosi., and by the European Research Council (ERC) grant agreements 714936 to M. Alvaro

Angel, R. J., et al. (2015).  Journal of Metamorphic Geology33(8), 801-813.

Bose, K., & Ganguly, J. (1995). American Mineralogist80(3-4), 231-238.

Kaminsky, F. (2012). Earth-Science Reviews110(1-4), 127-147.

Murri, M., et al. (2018). American Mineralogist103(11), 1869-1872.

Rosenfeld, J. L., & Chase, A. B. (1961). American Journal of Science259(7), 519-541.

How to cite: Campomenosi, N., Angel, R. J., Alvaro, M., and Mihailova, B.: Mineral inclusions under non-ambient conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9255, https://doi.org/10.5194/egusphere-egu24-9255, 2024.

Understanding the mechanisms of mountain building and its destruction poses significant challenges. Following subduction of a slab, an increase in the subduction rate and/or a decrease of the convergence rate, may lead to slab rollback. During slab rollback, segments of the middle-lower crust may undergo heating and partial melting due heating of thinned lithosphere by the asthenosphere and the migration of the magmatic arc. Alternatively, after accretion of radiogenic crust, the lower parts of the crust may relax through radiogenic decay. In both scenarios, the heating of the middle-lower crust reduces crustal strength, resulting in the development of metamorphic core complexes. The timing of lower crust heating is crucial for understanding the switchover from lithospheric shortening to extension.

The Hellenides in the eastern Mediterranean constitute an arcuate orogen located north of the present-day active Hellenic margin, marking the site of NNE-ward subduction of the African plate beneath Eurasia. The Aegean Sea region in the Hellenide is a world-class example of large-scale continental extension above a retreating subduction zone. In the Cyclades, the Hellenide orogeny began in the early Cenozoic, causing subduction and sustained high-pressure (HP) metamorphism between approximately 53 and 30 Ma. The timing of slab rollback is subject of intense debate. A decrease in the convergence rate was interpreted to suggest that slab rollback initiated at around 35–30 Ma, during or even after the waning stages of HP metamorphism. In contrast, the formation of extensional sedimentary basins and radiometric dating of extension-related mylonite place rollback at approximately 23 Ma, distinctly after the final stages of HP metamorphism.

Between about 30 Ma and 20 Ma, isobaric heating during the exhumation of some HP rocks has been proposed on some islands (Syros, Tinos, Andros, and Naxos). However, the precise timing and duration of this isobaric heating remains largely unconstrained. On Naxos, previous geothermobarometry estimates indicate isobaric heating occurred from 500 to 550°C from a middle segment of the nappe stack (Peillod et al., 2021). Garnet chemical zonation formed during exhumation allows for a heating timescale to be estimated via diffusion chronometry. We conducted Monte Carlo diffusion simulations to determine the best-fitting timescale based on Chi-square statistics, assuming three different heating paths. Diffusion model results for a heating path from 500 to 550°C indicate a 10 Myr timescale. A lower temperature path (from 400 to 450°C) requires heating over an unreasonable geological timescale (>100 Myr). Conversely, a higher temperature path (from 600 to 650°C) requires a timescale of <1 Myr. This higher temperature path corresponds to temperatures recorded near the migmatite core at the bottom of the Naxos nappe stack. At such temperatures and within a 10 Myr period, chemical heterogeneities in garnet would have relaxed, as observed in most garnets near the migmatite core. The results of this approach indicate that the heating of the lower crust occurs over a 10 Myr period, suggesting that the heating may result from radiogenic decay during the Oligocene before the slab roll during the Miocene.

How to cite: Peillod, A., Hess, B., and Ring, U.: Slab reequilibration and slab roll back timing in the Cyclades: Evidence from garnet diffusion and P-T estimates (Naxos, Greece), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9789, https://doi.org/10.5194/egusphere-egu24-9789, 2024.

EGU24-9809 | ECS | Orals | GMPV4.6 | Highlight

Role of manganese, chromium and vanadium in the photoluminescence emission spectrum of grossular var. tsavorite from Tanzania. 

Alfredo Idini, Celestino Angeli, Franco Frau, and Roberto Argazzi

Tsavorite is the trade name for the green vanadium-chromium variety of grossular. The occurrence of tsavorite plays a key role in the geological research inherent to the formation of the Gondwana continent because it is hosted exclusively in the metamorphic unit from the Neoproterozoic Metamorphic Mozambique Belt (NMMB). The studies on the tsavorite deposit of the NMMB contributed to determining the metamorphic evolution of these Precambrian terrains. The areas of Merelani Hills (Tanzania) and Tsavo Park (Kenya) are by far the most important source of high-quality specimens of tsavorite that are extensively used for petrological studies. Furthermore, the tsavorite crystals from Merelani Hills exhibit a peculiar feature: the fluorescence is easily recognizable lighting up centimetric crystals with a common portable LED lamp. Using the long UV we observe a bright pink-orange colour, while exciting with the short UV the effect is a pale yellow. To the best of our knowledge, this phenomenon is unusual among the members of the garnet group and only a few research papers have investigated this phenomenon in natural garnets. To characterize the fluorescence, up to 25 grams of tsavorite crystals were meticulously sampled from the rocky matrix under the UV lamp and then pulverized in an agate mortar to perform an accurate XRPD acquisition. The results show that no other phases than garnet are present and, thanks to the high quality of the XRPD acquisition, the Electron Density Map was calculated and plotted against a CIF grossular standard, showing that an excess of negative charge is clearly pinpointed in the Y(6) crystallographic site, occupied by Al+3 in the grossular standard structure. The bulk elemental analysis, performed on the same powder used for XRPD acquisition, shows that the contents of Fe, Mg and Mn are < 0.5 wt.%, while V2O3  and Cr2O3 are respectively 0.32  and 0.015 wt.%, showing a good consistency with bibliographic data. The fluorometry with an excitation beam at 408 nm indicates a complex emission pattern with the most intense emission at 701 and 716 nm and subordinately at 592 nm. The colour perception of the emitted light is dominated by the emission band at 592 nm which is close to the peak sensitivity of the human eye at 555 nm, while the contribution of the red band, though more intense, is perceived as much weaker due to the lower eye sensitivity and modulates the colour ranging from bright orange to pink-red. Because of the characteristic colour perceived under UV light, the use of a common led lamp can serve as a diagnostic tool to identify tsavorite whenever a rapid test is required, e.g. in the case of field survey. The emitted photoluminescence lines, besides the very uncommon low andradite molarity, allow precise identification of the emissions of Mn2+, Cr3+ and V3+.

 

 

How to cite: Idini, A., Angeli, C., Frau, F., and Argazzi, R.: Role of manganese, chromium and vanadium in the photoluminescence emission spectrum of grossular var. tsavorite from Tanzania., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9809, https://doi.org/10.5194/egusphere-egu24-9809, 2024.

EGU24-9913 | ECS | Posters on site | GMPV4.6

New petrological and geochronological results from the Koralpe-Saualpe-Pohorje Complex (Eastern Alps) 

Iris Wannhoff, Jan Pleuger, Xin Zhong, Timm John, Leo J. Millonig, Axel Gerdes, and Richard Albert

The Koralpe-Saualpe-Pohorje Complex (KSPC) in the Eastern Alps stretches from SE Austria to NE Slovenia and hosts the type locality for eclogite. Although the KSPC has been studied for decades, some aspects of its tectonometamorphic evolution are still controversial. There is, for example, an ongoing discussion, if the Pohorje unit experienced ultra-high-pressure (UHP) conditions during the Eoalpine orogeny. The KSPC is part of the Austroalpine basement units and was interpreted to represent a coherent (U?)HP nappe consisting mainly of gneisses and metasedimentary rocks, with abundant eclogite lenses embedded. Some of the Austroalpine basement units, including the KSPC, experienced a long-lived Permian-Triassic tectonometamorphic event, where gabbros intruded into a thinned crust, which experienced eclogite facies conditions during the Late Cretaceous. A metamorphic field gradient with an increase in peak pressure-temperature (PT) conditions from NW to SE, and UHP conditions for Pohorje, has previously been proposed based on thermodynamic modelling, geothermobarometry and the discovery of diamond in fluid inclusions in garnet. To unravel the metamorphic evolution of the KSPC, we applied quartz-in-garnet elastic barometry, Zr-in-rutile thermometery and in-situ U-Pb dating of garnet and rutile from eclogite and metasedimentary rock samples along a NW-SE transect. This is the first application of quartz in garnet elastic barometry within the KSPC in order to determine the entrapment pressures of the quartz inclusions. The eclogite samples yielded maximum pressures of 1.9 GPa across the KSPC, indicating no pressure increase from the NW to SE. The metasedimentary rocks show overall lower pressures with a maximum of ca. 1.4 GPa. Zr-in-rutile thermometry yielded uniform temperatures of 640 (±30)°C, indicating no temperature gradient. The novel approach of in-situ garnet U-Pb dating was conducted to decipher potentially different metamorphic events. Garnet from the Koralpe, Saualpe and Pohorje metasedimentary rocks yielded Early Cretaceous dates ranging from ~95 to 105 Ma, similar to eclogitic garnet from the Koralpe with ~112 Ma. Additionally, garnet from a Saualpe micaschist yielded Late Triassic cores (~224 Ma) and Early Cretaceous rims (~115 Ma). Rutile throughout the KSPC yielded Late Cretaceous U-Pb dates of ~98–83 Ma (eclogites) and ~87–80 Ma (metasedimentary rocks).The results of this study suggest that the KSPC represents a coherent nappe. The recorded maximum pressures and temperatures are identical throughout the KSPC. The lower pressure for the metasedimentary rocks is interpreted to be the result of viscous relaxation in garnet due to the presence of fluids during metamorphism. The obtained garnet U-Pb dates from both eclogites and metasedimentary rocks are interpreted as Late Cretaceous bulk crystallization ages that reflect prograde to peak metamorphic garnet growth. The Late Triassic U-Pb dates from the Saualpe garnet cores are in line with the existing literature proposing a polymetamorphic cycle for the KSPC. The rutile dates are interpreted as cooling ages. The lack of a metamorphic field gradient may imply a different tectonical setting for the KSPC than previously proposed, and warrants further investigation.

How to cite: Wannhoff, I., Pleuger, J., Zhong, X., John, T., Millonig, L. J., Gerdes, A., and Albert, R.: New petrological and geochronological results from the Koralpe-Saualpe-Pohorje Complex (Eastern Alps), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9913, https://doi.org/10.5194/egusphere-egu24-9913, 2024.

EGU24-10096 | ECS | Orals | GMPV4.6

Formation of various trace element zoning patterns in high-pressure metamorphic garnet 

Jan Kulhánek and Shah Wali Faryad

Compositional zoning of trace elements in garnet serves as a valuable tool for reconstructing petrogenetic evolution, supplementing major element analyses. This is particularly applicable to trace elements exhibiting a strong affinity for garnet and characterized by slow diffusion rates, such as Y and heavy rare earth elements (HREE). The present study examines various zoning patterns of trace elements observed in large garnet porphyroblasts within micaschist samples from the Variscan high-pressure (HP) metamorphic terrain of the Krušné hory Mts. (Saxothuringian zone, Bohemian Massif).

Using electron probe micro-analyser and laser ablation-inductively coupled plasma mass spectrometry, three distinct types of compositional zoning in garnet were identified by compositional mapping. These zoning types were classified as a continuous core-to-rim change, concentric annular changes, and overprinting (or mimicking) of a pre-existing distribution. The study focuses on the formation mechanisms of each type of zoning, their dependence on pressure-temperature change, and fluid availability.

The significantly elevated concentrations of Sc, Y, and HREE in the garnet's central core suggest a rapid diffusion of these elements from the matrix into the garnet after nucleation, challenging a description solely through Rayleigh fractionation. The observed prograde growth of pressure-temperature (PT) conditions of the rock samples to HP–medium temperature (MT) aligns well with the compositional zoning patterns exhibited by the garnet, encompassing major and trace elements, as well as other minerals. Specific compositional patterns include: (1) gradual increase in Co and Zn contents towards the rim, mirroring Mg and inversely related to Mn, indicative of a continuous rise in temperature; (2) overprint zoning of Ti and partly Ca, Sm, Eu, Gd, and Tb in the central part, transitioning to purely concentric annular zoning in the rim, suggesting an increase in temperature; (3) well-developed overprint zoning of Cr throughout the garnet grain, indicating temperatures only up to MT; and (4) depletion of Y, and most of rare earth elements (HREE, Ho, Dy, Tb, Gd, Eu, and Sm – REE) in the rim, accompanied by enrichment of coupled VIII(Na, Li)+ + IVP5+ substitution elements, experimentally documented from HP to ultra-HP conditions.

The observed inverse annular oscillatory distribution of Sc and V is discussed to be attributed to fluctuating oxygen fugacity during garnet growth, influenced by changes in the availability of the fluid matrix medium carrying trace elements. Higher fluid availability corresponds to increased Sc, Y, and REE incorporation into garnet, evident in well-correlated annular elevations, while V exhibits the inverse trend. Elevated trace element contents in garnet are linked to the breakdown of main and accessory phases carrying these elements during garnet growth, incorporating them into the garnet. The presence of a fluid medium in the system appears to predominantly influence the extent and frequency of annular variations in trace element concentrations. Thus, annular zoning in garnet is associated with both the decomposition of trace element-bearing phases and fluid medium availability.

Acknowledgement: This work was supported by the Czech Science Foundation (Grant No. 24-12845S), Grant Agency of Charles University (Grant No. 1194019), and by Charles University through the Cooperatio Program (Research Area GEOL).

How to cite: Kulhánek, J. and Faryad, S. W.: Formation of various trace element zoning patterns in high-pressure metamorphic garnet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10096, https://doi.org/10.5194/egusphere-egu24-10096, 2024.

EGU24-10532 | ECS | Posters virtual | GMPV4.6

Petrological and textural characteristics of Garnet mica schists and Gneisses from Almora Group: Insights into pre-Himalayan metamorphism from Kumaun Himalaya, India 

Tanya Srivastava, Mallickarjun Joshi, Alok Kumar, Amar Nath Tiwari, and Shubham Patel

In Kumaun Lesser Himalaya, North Ramgarh Thrust and South Ramgarh Thrust define the northern and southern boundaries of the Almora Nappe. The Almora Nappe consists of two tectono-stratigraphic units, viz. the Ramgarh Group and the Almora Group. The Ramgarh Group consists of mylonitised granite gneisses capped by low-grade metamorphic rocks and the Almora Group consists of an interbanded sequence of metapelites and metapsammites progressively metamorphosed from the greenschist to upper amphibolite facies conditions. The Almora Group rocks comprise quartzites, garnet-mica schists, and K-feldspar–sillimanite gneisses. The garnet-mica schists are coarse to medium-grained, with well-developed foliation defined by chlorite-biotite-muscovite-garnet-plagioclase-quartz mineral assemblage, and the accessory minerals are apatite and zircon. The pelitic gneisses consist of garnet, kyanite, cordierite, sillimanite, and K-feldspar. Garnet is a common and important mineral in these metamorphic rocks to constrain P-T conditions.  In this study, we specifically focus on the textural details of garnets from the schists and gneisses of the Almora Group. The most common garnet is type II garnet which is synkinematic with S-shaped inclusions of quartz and biotite, while the older type-I garnets occur as stretched out grains in the matrix with the stretch direction generally parallel to the foliation. The garnet porphyroblasts are euhedral to subhedral and consist of quartz, plagioclase, muscovite, and apatite inclusions, which are wrapped around by muscovite and biotite lepidoblasts. The hematite leachings are observed around the periphery of the garnet porphyroblasts that suggest high fO2 in the last stages of garnet growth. The micas microfolded in a few samples, with the presence of quartz in the folded hinge region. The garnets can be classified into at least two generations based on textural and petrographic attributes. Moreover, the presence of an idioblastic rim in the garnets suggests that the later phase of metamorphism outlasted the deformation. The occurrence of two generations of garnet i.e. garnet within garnet documented by (Joshi & Tiwari, 2004; Joshi & Tiwari, 2009) suggests a hiatus in crystallization and the associated metamorphic processes are likely attributed to two generations of pre-Himalayan metamorphisms.

 

How to cite: Srivastava, T., Joshi, M., Kumar, A., Tiwari, A. N., and Patel, S.: Petrological and textural characteristics of Garnet mica schists and Gneisses from Almora Group: Insights into pre-Himalayan metamorphism from Kumaun Himalaya, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10532, https://doi.org/10.5194/egusphere-egu24-10532, 2024.

EGU24-11318 | ECS | Posters on site | GMPV4.6

Nanostructural and chemical evolution of garnet during high-strain deformation 

Renelle Dubosq, Alfredo Camacho, Anna Rogowitz, David Schneider, and Baptiste Gault

Garnet is a common high-pressure mineral in the Earth’s lithosphere. Considered a high-strength mineral stable across a wide range of pressure and temperature conditions, it is generally accepted that garnets can retain their microstructures and chemical composition during deformation and metamorphism. Therefore, the trace and major element compositions of garnet are commonly used for geothermobarometers and geochronometers to provide the conditions and timing of metamorphic events. We combine electron backscatter diffraction (EBSD), electron channeling contrast imaging (ECCI) and atom probe tomography (APT) on garnet from an eclogite facies mylonite in the Musgrave Province (central Australia) to investigate the mechanisms of element mobility during high-strain deformation under dry (<0.002 wt% H2O), lower crustal conditions. Previous investigations suggest that mylonitization occurred at 1.2 GPa and 650°C. Herein, we focus on two garnet clasts that are located within one common high-strain zone. EBSD and ECCI data from garnet clast 1 reveal a micro-shear zone characterized by recrystallized strain-free garnet crystals. APT analysis of one of the recrystallized high-angle grain boundaries shows Fe enrichment in the form of  equally spaced (4.5–6.5 nm), planar arrays of Fe-rich nanoclusters (3.0–7.5 nm). The combined data suggests that these nanoclusters formed as a result of enhanced Fe diffusion along high-angle grain boundaries of recrystallized garnet during high-strain deformation. Garnet clast 2 evinces crystal-plasticity associated with brittle deformation in the form of heterogeneous misorientation patterns and low-angle grain boundary development at the rim of the garnet porphyroclast. APT analysis of a low-angle grain boundary within the highly-strained clast shows Ca enrichment and Mg depletion along dislocations, suggesting crystal-plasticity enhances element mobility via 'pipe' diffusion, with dislocations acting as high-diffusivity pathways. Our data reveal the interaction of chemical and mechanical processes at the nanoscale through deformation-induced enhanced element diffusivity. Consequently, caution should be exercised when using deformed garnets as petrological tools because of this enhanced major element mobility during high-strain deformation. To evaluate this hypothesis, we modelled the Ca diffusion profiles across undeformed and deformed garnet rims within clast 2. Simulations based on the measured Ca concentration profiles of the undeformed rims yield time estimates of 0.8 to 1 Ma for the duration of high-strain deformation at eclogite facies along the shear zone, whereas simulations across the deformed rims yield longer time estimates of 5 to 22 Ma. Our study thus highlights the importance of conducting a thorough microstructural and geochemical analysis on garnet prior to utilizing the mineral for petrological applications.

How to cite: Dubosq, R., Camacho, A., Rogowitz, A., Schneider, D., and Gault, B.: Nanostructural and chemical evolution of garnet during high-strain deformation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11318, https://doi.org/10.5194/egusphere-egu24-11318, 2024.

EGU24-11567 | Posters on site | GMPV4.6

Systematic variations in shape preferred orientation and crystallographic orientation relationships of rutile inclusions in garnet upon fractional crystallization of pegmatoid melt 

Thomas Griffiths, Victoria Kohn, Taisia Alifirova, Nina Daneu, Eugen Libowitzky, Olga Ageeva, Rainer Abart, and Gerlinde Habler

Almandine-spessartine garnet in a Moldanubian peraluminous pegmatoid  (Bohemian Massif, Austria) shows asymmetric morphology, compositional zoning, and microstructural zoning, indicating directed crystal growth. Sector-specific variations in inclusion abundance and microstructures in {112} and {110} garnet sectors indicate facet-specific crystallization processes, associated with individual garnet surface configurations and a compositional boundary layer (CBL) present in the melt adjacent to growing garnet (Kohn et al., 2024). Rutile inclusions show distinct changes in abundance, aspect ratio, shape preferred orientations (SPOs) and crystallographic orientation relationships (CORs) between garnet growth zones. We quantified the SPOs of > 2400 rutile needles in two crystallographically equivalent {112}Grt rim sectors, and recorded the COR, location, habit and SPO of > 350 rutile inclusions in a transect across core and rim zones within one {112} Grt sector.

Rutile inclusions are elongated parallel to the four ⟨111⟩ Grt directions, the three ⟨100⟩ Grt directions and one ⟨112⟩ Grt direction. The most frequent SPO for a given {112} Grt sector is the one closest to the garnet growth direction (i.e. the facet normal), whereas the SPO lying in the facet is exceedingly rare. Sectioning effects cannot explain these frequency variations. Based on the facet-specific SPO and COR statistics, we infer rutile inclusions formed by nucleation at the advancing garnet surface and subsequent co-growth with the host.

Based on directly correlated SORs and CORs between elongate rutile inclusions and garnet host, specific CORs were pooled into three COR groups: 103R/111G (“one <103>Rutile direction one <111>Garnet direction”), 001R/111G and 001R/100G. Within one {112} Grt sector, core domains exhibit lower aspect ratios and higher abundance of rutile inclusions, with COR group 103R/111G being predominant. Contrastingly, the rim domain exhibits highly elongate rutile needles with lower abundance. The dominant COR group changes to 001R/111G and COR group 001R/100G appears. We suggest the decrease in inclusion abundance signals a decrease in the ratio of rutile nucleation rate to rutile growth rate, while the increase in aspect ratio signals an increase in the growth rate of rutile compared to the garnet growth rate (normal to the facet). The needle-bearing rim supposedly crystallized from a melt with higher Na, Si and OH content compared to the core (Kohn et al. 2024). A corresponding increase in diffusion rates of components in the melt is hypothesized to have decreased supersaturation with respect to rutile in a CBL, decreasing rutile nucleation rates and affecting relative growth rates. The preference for particular SPO-COR combinations should be influenced by the garnet surface configuration upon heterogeneous nucleation of rutile. Radial and lateral variations of rutile CORs and SPOs are thus attributed to changes in the nature of the garnet/melt interface, and/or the garnet growth mechanism.

Based on comparison with previous studies, changes in rutile COR group frequencies associated with increasing Si- (and likely OH) content of the melt are a systematic feature of magmatic fractional crystallization in peraluminous pegmatitic systems containing rutile-bearing garnet.

Funded by Austrian Science Fund (FWF): I4285-N37 and Slovenian Research Agency (ARRS): N1-0115

Kohn et al. (2024), Lithos, DOI: 10.1016/j.lithos.2023.107461

How to cite: Griffiths, T., Kohn, V., Alifirova, T., Daneu, N., Libowitzky, E., Ageeva, O., Abart, R., and Habler, G.: Systematic variations in shape preferred orientation and crystallographic orientation relationships of rutile inclusions in garnet upon fractional crystallization of pegmatoid melt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11567, https://doi.org/10.5194/egusphere-egu24-11567, 2024.

EGU24-11813 | ECS | Posters on site | GMPV4.6

High-pressure eclogites preserve a halogen-bearing metasomatizing agent in primary melt inclusions (Bohemian Massif, Germany). 

Alessia Borghini, Silvio Ferrero, Patrick O'Brien, Bernd Wunder, Peter Tollan, Jarosław Majka, Rico Fuchs, and Kerstin Gresky

Garnets in the eclogites of Pfaffenberg, Granulitgebirge (Bohemian Massif, Germany) contain primary granitic melt inclusions with a continental crust signature. The inclusions are up to 30 µm in diameter and polycrystalline with a main mineral assemblage dominated by phlogopite/biotite, kumdykolite, quartz/cristobalite, two unknown phases with main Raman peaks at 412 and 430 cm-1 respectively, osumilite and plagioclase. In minor amounts, the inclusions contain also white mica, K-feldspar, amphibole and kokchetavite with the local presence of a fluid phase composed of CO2, CH4 and N2.

The inclusions were successfully re-homogenized at 975ºC and 2.7 - 3 GPa and the melt is from trondhjemitc to granitic, peraluminous and hydrous (average H2O = 4.82 wt%). The melt trace elements patterns revealed similarities with melts produced by partial melting of metasediments part of the continental crust. The melt is in fact enriched in Cs, Pb, Rb, Th, U, Li and B and most likely it originated from the continental crust itself. Interestingly, in situ analyses of Cl and calculation of F partitioning between apatite and melt show that the melt is exceptionally halogens-rich with an average Cl content of 0.41 wt% and a calculated F content of 0.23 wt%.

Pfaffenberg eclogites occur as lenses in garnet peridotite and they are surrounded by continental rocks. They can be regarded as the product of crust-mantle interaction taking place during subduction at mantle depth with the agent of the interaction, i.e., the melt, now preserved as inclusions in the eclogite garnets. The melt is responsible for crustal material mobilization and transfer in the mantle and can be used to constrain and quantify the elements, especially volatiles, transported from the crust to the mantle.

This research is part of the project No. 2021/43/P/ST10/03202 co-funded by the National Science Centre of Poland and the European Union Framework Programme for Research and Innovation Horizon 2020 under the Marie Skłodowska-Curie grant agreement No. 945339.

How to cite: Borghini, A., Ferrero, S., O'Brien, P., Wunder, B., Tollan, P., Majka, J., Fuchs, R., and Gresky, K.: High-pressure eclogites preserve a halogen-bearing metasomatizing agent in primary melt inclusions (Bohemian Massif, Germany)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11813, https://doi.org/10.5194/egusphere-egu24-11813, 2024.

Documenting metamorphic conditions through the geologic record is a key for understanding the evolution of plate tectonics on Earth. Minerals characteristic for deep subduction processes (i.e. modern-style plate tectonics) like glaucophane, coesite, and diamond are commonly replaced by their low-pressure polymorphs during exhumation. However, when entrapped as inclusions in resistant host minerals like garnet, these mineral phases are shielded from external metamorphic fluids and may be preserved. Finding evidence for deep subduction processes in host garnets of large volumes of (partially) re-equilibrated crystalline rocks is challenging, time consuming, and often hampered by poor outcrop conditions due to weathering and soil formation. In contrast, by analyzing detrital garnet, natural processes such as erosion and sedimentary transport can sample garnet grains sourced from fresh as well as altered crystalline rocks located in the drainage area, enabling large crustal volumes to be screened using a comparatively low number of samples. Case-studies from Norway (Schönig et al. 2018, Sci. Rep.), Germany (Schönig et al. 2019, Geology; Schönig et al. 2020 Gondwana Res.), Austria, Papua New Guinea (Baldwin et al. 2021, PNAS), and Greenland (Schönig et al. 2023, Eur. J. Mineral.) demonstrate mineral inclusion analysis of detrital garnet integrated with major-element chemistry (Schönig et al. 2021, Contrib. Mineral. Petrol.) to be an efficient tool for screening tectonometamorphic units on the presence or absence of rocks related to modern-style plate tectonic processes (Schönig et al. 2022, Earth-Sci. Rev.). This contribution gives a synopsis of the main findings from the five spatially, chronologically, and tectonically distinct localities.

How to cite: Schönig, J.: Detrital Garnet Petrology: Inclusions as a main source of information, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14917, https://doi.org/10.5194/egusphere-egu24-14917, 2024.

EGU24-15529 | Orals | GMPV4.6 | Highlight

Common, non-cubic garnet in metamorphic rocks: the state of the art 

Bernardo Cesare, Enrico Mugnaioli, Tommaso Tacchetto, Sofia Lorenzon, Cristian Biagioni, Fabrizio Nestola, Nicola Campomenosi, and Giancarlo Della Ventura

Since the first report on the tetragonal structure of common (OH- and andradite-free) garnet in metamorphic rocks (Cesare et al., 2019) , many new occurrences have been discovered.

Non-cubic anhydrous garnets are widespread in low-temperature metamorphic terranes worldwide, including the world-renowned blueschists from the Franciscan Complex (USA), Syros (Greece) and Aosta Valley (Italy), and the phyllites from the iconic Barrow garnet zone of Scotland.

These garnets share compositional features such as grossular >20% and pyrope <7%, which are common in both metabasites and metapelites metamorphosed at T < ~500 °C.

The non-isotropic nature of these garnets determines a very weak birefringence, which is generally overlooked, yet it can be easily detected by polychromatic polarization microscopy on conventional 30-µm thin sections. Similarly, this deviation from an isotropic behaviour can be observed by Raman microspectroscopy using crossed-polarized geometry.

Optically, the birefringence pattern suggests the presence of twelve growth sectors (twins) arranged in a dodecahedron, displaying sector quartets with three crystallographic orientations having optical axes swapped by 90°.

Preliminary single-crystal XRD and HRTEM investigations have demonstrated that these anisotropic garnets have a pseudocubic tetragonal structure with a minimal (~ 1/1000) difference between the a,b and c axes.

Due to the minimal departure from the cubic cell, conventional EBSD orientation analysis could notdiscriminate the orthogonal orientation of axes in the optically different sectors. However, EBSD revealed consistent, small (<1°) structural disorientations coincident with the rhythmic Ca-Fe compositional variations, similar to what is observed in zircon growth zoning.

This presentation will report the new results obtained from FPA-FTIR, HRTEM, single-crystal XRD and synchrotron micro-XAS investigations, aiming to better constrain the crystallographic structure of tetragonal garnets as well as their OH- content, thereby providing a better understanding of the origin of their departure from a cubic structure.

 

References

Cesare, B., Nestola, F., Johnson, T. et al. Garnet, the archetypal cubic mineral, grows tetragonal. Sci Rep 9, 14672 (2019). https://doi.org/10.1038/s41598-019-51214-9

How to cite: Cesare, B., Mugnaioli, E., Tacchetto, T., Lorenzon, S., Biagioni, C., Nestola, F., Campomenosi, N., and Della Ventura, G.: Common, non-cubic garnet in metamorphic rocks: the state of the art, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15529, https://doi.org/10.5194/egusphere-egu24-15529, 2024.

EGU24-17060 | ECS | Posters on site | GMPV4.6

Decompression of high-grade metamorphic mafic rocks with small-scale compositional layering, Gföhl Unit, Moldanubian Zone 

Rene Asenbaum, Rainer Abart, and Martin Racek

Mafic–ultramafic lenses embedded in felsic granulites of the Gföhl Unit, Moldanubian Zone, are considered as mantle fragments incorporated into mid-crustal levels of the Variscan orogenic crust. We investigated a several 100 m-sized mafic lens mainly formed by garnet-pyroxenite. Several samples were collected from loose boulders. Petrographic features provide evidence for an early HP-HT eclogite-facies peak metamorphism overprinted to variable degrees by HT granulite-facies metamorphism at lower pressures.

The primary eclogite facies mineral assemblage comprises garnet, sodium-rich clinopyroxene, kyanite, rutile and quartz. The rocks are characterized by

compositional layering on the mm-scale, which is reflected by corresponding systematic variation of the compositions of garnet porphyroblasts. The garnets show homogeneous compositions in their internal domains defining plateaus, the compositional characteristics of which correlate with the compositional layering of the rocks and vary from Alm19 Prp55 Grs27 to Alm15-18 Prp42-50 Grs32-43. The systematic variation of garnet compositions with the bulk rock compositional layering testifies to lack of equilibration between the compositionally distinct layers on the mm-scale during HP-HT eclogite-facies metamorphism.

The HT-granulite-facies overprint is manifested by the breakdown of the eclogite facies mineral assemblage. This is evident, for example, from the formation of sapphirine–spinel–an-rich plagioclase symplectites in garnet supposedly replacing garnet-hosted kyanite and clinopyroxene inclusion. Another peculiar feature is represented by the partial resorption of garnet by plagioclase and clinopyroxene in the form of corrosion tubes penetrating the garnet in a worm-like fashion. Finally, garnet is partially or entirely replaced by plagioclase–spinel–orthopyroxene—clinopyroxene symplectite, where Grs-rich garnets are systematically more strongly affected by this replacement than Grs-poor garnets. Quartz is consumed during the decompression reactions and can only be found as rare relic grains. When a clinopyroxene matrix surrounds relic quartz, the clinopyroxene becomes successively more Si-rich due to inverse Tschermak substitution towards the relic quartz grain.

Throughout the samples and irrespective of the layer they pertain to, the garnets show similar pronounced secondary compositional zoning in the outermost 200 µm. The zoning is characterized by a strong decrease of the Grs content accompanied by an increase of the Alm and Prp contents towards the rim. The compositional changes in garnet are gradual suggesting diffusion-mediated re-equilibration at decreasing pressures, and the composition of the garnet at the interface to the rock matrix is the same throughout the specimen indicating that the rock equilibrated on the cm scale during the HT overprint.

Pressure and temperature were estimated based on equilibrium phase diagrams. They indicate peak pressures above 1.8 GPa and temperatures of around 950 °C for the primary mineral assemblages and the different garnet cores. In accordance with peak P-T, the garnet rims indicate pressures of around 1.3 GPa at the same temperature.

Considering the regional metamorphic setting of the Moldanubian Zone, the relatively localized secondary chemical zoning of garnet at its rim indicates that the granulite-facies metamorphism was remarkably short-lived and suggests rapid transport of the mafic–ultramafic lithologies from mantle depths to the mid-crustal level. Very likely incorporation of the relatively hot mafic lens into a supposedly cooler dominantly felsic environment led to immediate cooling of the mafic lens.

How to cite: Asenbaum, R., Abart, R., and Racek, M.: Decompression of high-grade metamorphic mafic rocks with small-scale compositional layering, Gföhl Unit, Moldanubian Zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17060, https://doi.org/10.5194/egusphere-egu24-17060, 2024.

EGU24-17450 | ECS | Orals | GMPV4.6

Extending (Garnet) Diffusion Modelling into Multidimensional Domains 

Ben Knight and Chris Clark

The variation in element concentrations within a mineral play a critical role in understanding the evolution of geological margins over time. Diffusion is a process that alters element concentrations during crystal growth and subsequent cooling, with modelling of this process primarily conducted in one-dimension (1D), significantly contributing to understanding the thermal and tectonic evolution of various igneous and metamorphic regions. However, the complexity of geological systems requires a more detailed approach encapsulating the multidimensional nature of mineral evolution. We present the initial developments of diffusion modelling, extending from 1D models to two-dimensional (2D) and three-dimensional (3D) modelling of garnet diffusion using the Underworld code. These models are designed to better constrain geological settings where garnet diffusion occurs, concentrating on the growth and extraction of the mineral from various bulk rock compositions. 2D and 3D models are compared to previously published work to validate the development of the models. Furthermore, the implications of these models for geochronological and petrological interpretations are explored, highlighting their potential to provide further insights into metamorphic processes when compared to 1D models. Future work will focus on the anisotropic properties of the garnet, including fast diffusion pathways within the mineral, as well as anisotropic properties of the rock itself, due to varying diffusion coefficients across minerals. This research paves the way for a more comprehensive understanding of diffusion in rocks, offering a robust tool for the community to unravel the complex history recorded in metamorphic rocks and enhance the accuracy of thermobarometric estimations. Through these new tools, we aim to provide better insights into the evolution of geological margins over time.

How to cite: Knight, B. and Clark, C.: Extending (Garnet) Diffusion Modelling into Multidimensional Domains, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17450, https://doi.org/10.5194/egusphere-egu24-17450, 2024.

EGU24-18033 | ECS | Orals | GMPV4.6

Exploring Garnet’s Geochemical Variations: Insights into Base Metal Deposits  

Joëlle D'Andres, John Mavrogenes, Elena Belousova, and Fabrizio Magrini

This study addresses a significant gap in the geochemical literature by systematically investigating garnet compositions within and around base metal deposits -- a topic that remains relatively understudied, despite the mineral's known significance in various geological contexts. Garnet, traditionally associated with diamond exploration and recognized for its potential as an indicator mineral for deposits like skarns,emerges in our research as a key geochemical tracer in the context of base metal exploration.

Focusing on the Eastern Succession of the Mount Isa Inlier in Australia, a globally significant mineral province, we characterized the major and trace element compositions of garnets associated with diverse base metal systems. Our new dataset, containing more than 2500 datapoints, was complemented by literature data compiled from a range of mineral systems including skarns, IOCGs, subaqueous volcanic-related (VMS, Broken Hill, sedimentary-exhalative), porphyry-epithermal and granite-related pegmatite systems. Comparative analyses with background metamorphic/igneous garnets reveal distinct trends in Mn-Fe and Ca-Mg space in ore-associated garnets, along with unique trace element patterns (e.g., Eu anomalies) and chalcophile element variations (e.g., Zn, Cd, Ga) in diverse ore systems.

To clarify the importance of these anomalous compositions, we refined our dataset by considering specific garnet associations and their related geological context. Garnets in the database were categorized depending on their occurrence within the ore bodies, the alteration haloes, or the background lithologies. Additionally, we carried out a multivariate statistical analysis through a principal component analysis (PCA) and subsequent cluster analysis, to identify hidden spatial patterns. Our results shed light on the geochemical variations in garnet composition across various ore systems and provide new insights into the sources of these variations.

This research not only contributes valuable geochemical data for base metal exploration but also establishes the efficacy of multivariate statistical analyses in deciphering complex garnet data structures. The implications of our findings extend beyond the Eastern Succession of the Mount Isa Inlier, fostering a broader understanding of the geochemical dynamics associated with base metal deposits globally.

How to cite: D'Andres, J., Mavrogenes, J., Belousova, E., and Magrini, F.: Exploring Garnet’s Geochemical Variations: Insights into Base Metal Deposits , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18033, https://doi.org/10.5194/egusphere-egu24-18033, 2024.

This study analyses the H2O content in nominally anhydrous minerals (NAMs) in 10 eclogites from W Norway. Each sample has oriented lamellar to acicular inclusions in clinopyroxene, which are either quartz with pargasite or quartz/albite without pargasite [1]. Low-Al orthopyroxene and polycrystalline quartz inclusions in several of these samples provide evidence for UHP metamorphism in the stability fields of diamond and coesite. The H2O content is quantified using Fourier transform infrared spectroscopy (FTIR), unpolarised infrared radiation, spectra deconvolution, and the calibration of [2].

Preliminary data was obtained from the analysis of the first 5 eclogites yield for garnet 22-379 and 16-31 µg g-1 structural H2O for samples with and without pargasite lamellae, respectively. The highest value occurs in a zoisite-bearing eclogite. If regarded separately, then the variation in the 4 zoisite-free eclogites shrinks to 16-32 µg g-1 H2O. Absorption bands characteristic for molecular H2O in garnet (centered at wavenumbers <3460 cm-1) were not observed. The ranges for structural H2O in clinopyroxene from these 5 samples are 125-380 and 183-564 µg g-1, respectively. The highest value occurs in a sample with intense recrystallization of clinopyroxene (but not garnet) after peak metamorphism. If regarded separately, then the total range is 125-380 µg g-1 H2O. The obtained clinopyroxene–garnet H2O partition coefficient has ranges of 1.0-11.0 and 11.6-18.2, respectively. The extreme values belong to the zoisite-bearing (1.0) and the strongly recrystallized (18.2) samples. If regarded separately, then the total range is reduced to 3.9-11.6.

 

Combining the preliminary data of the quantified structural water with petrological information tends to suggest the following relationships. (1) The current H2O content in NAMs is affected by the presence of hydrous minerals during peak metamorphism and the retrogression history. (2) The peak UHP garnet is water-deficient unless zoisite forms part of the mineral assemblage. (3) The current H2O content of clinopyroxene (containing oriented inclusions of quartz with and without pargasite) from "diamond-facies" UHP eclogite is lower compared to that of "graphite-facies" UHP eclogite from a similar tectonic setting that lacks such inclusion microstructures [3]. (4) Samples with oriented inclusions of pargasite in clinopyroxene tend to have lower clinopyroxene–garnet H2O partition coefficients than those without pargasite, which suggests that pargasite lamellae formed by clinopyroxene dehydration during early decompression. Additional data will be presented to test these preliminary indications.

This study received funding from Norway Grants 2014–2021 operated by the National Science Centre (Poland) under project contract no. 2020/37/K/ST10/02784.

[1] Spengler et al., 2023, Eur. J. Mineral. 35:1125-1147

[2] Bell et al., 1995, Am. Mineral. 80:465-474

[3] Gose & Schmädicke, 2022, J. Metamorph. Geol. 40:665-686

How to cite: Spengler, D.: Water in eclogitic garnet and clinopyroxene with oriented quartz and pargasite inclusions, W Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21602, https://doi.org/10.5194/egusphere-egu24-21602, 2024.

Abstract: The study of K-enriched intrusive rocks is essential for deciphering mantle metasomatism beneath active continental arcs. In this contribution, high-precision zircon U‒Pb‒Hf isotope, whole-rock geochemistry, Sr‒Nd isotope, and mineral chemistry analyses were performed to evaluate the petrogenesis and geodynamic system of the Yunnongfeng intrusion on the southwestern margin of the Yangtze Block. The Yunnongfeng intrusion consists of a high-K to shoshonitic rock assemblage with variable lithology from gabbro-diorite to granite. Zircon U‒Pb dating gives concordant crystallization ages of ca. 782.5 ± 3.8 Ma for gabbro-diorite, ca. 774 ± 4.1 and 776 ± 4.1 Ma for diorite, ca. 770 ± 4.7 Ma for quartz monzonite, ca. 763 ± 3.4 Ma for quartz syenite, and ca. 764 ± 16 Ma for granite. These samples also show similar Sr‒Nd, and Lu‒Hf isotopic compositions, implying a common magma source. The similar crystallization age and regular variation of major and trace element contents suggest that these rocks were formed through fractional crystallization of cogenetic primitive mantle magmas. The enriched εNd(t) (−5.7 to −5.1) and εHf(t) (−6.7 to −1.2) values, high Rb/Y and Th/La ratios, slight Nd‒Hf decoupling, and high-K and Th contents demonstrate that their lithospheric mantle source was enriched by slab-related fluid and sediment-related melt. The samples also exhibit remarkable enrichment in large-ion lithophile elements and depletion in high-field-strength elements, indicative of subduction-related arc magmatism. Taking into account previous studies, we suggest that the western margin of the Yangtze Block experienced a long-term subduction process during the Neoproterozoic, and the Yunnongfeng intrusion formed in an extensional back-arc basin. Based on the K-enriched mafic‒intermediate rocks from the western margin of the Yangtze Block commonly show high K2O/Na2O, Rb/Sr, low Ba/Rb ratios, and enriched εNd(t) values, our study, coupled with numerous previous reports, proposes that the K-enrichment resulted from the breakdown of phlogopite, owing to subduction-related sediment melt reacting with peridotite in the mantle source area.

Keywords: Potassium-enriched intrusive rocks; Southwestern Yangtze Block; Fractional crystallization; Lithospheric mantle; Sediment melt

How to cite: Jiang, X. and Lai, S.: Petrogenesis of Neoproterozoic high-K intrusion in the southwestern Yangtze Block, South China: Implication for the recycled subducted-sediment in the mantle source, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-253, https://doi.org/10.5194/egusphere-egu24-253, 2024.

EGU24-330 | Orals | GD4.1

The Role of Upper Mantle Forces in Post-subduction Tectonics: Insights from 3D Thermo-mechanical Models in the East Anatolian Plateau 

Ebru Şengül Uluocak, Russell N. Pysklywec, Andrea Sembroni, Sascha Brune, and Claudio Faccenna

Post-subduction tectonics can involve a wide range of spatiotemporal processes associated with regional and large-scale upper mantle forces. To better understand the interaction between these forces in collisional settings, we focus on active mantle dynamics beneath the East Anatolian Plateau, a well-documented segment of the Arabian-Eurasian continental collision zone. In detail, we use state-of-the-art instantaneous thermomechanical models by combining the advantages of 3D numerical modeling with high-resolution imaging techniques. We analyze the model’s outputs, such as 3D stress-strain and temperature variations of upper mantle convection and reconcile them with numerous geological and geophysical observations. Our results show prominent northward-directed channel flow in the mantle that cuts across the plateau and surroundings, from the Arabian foreland to the Greater Caucasus domain. This result reproduces and elucidates the proposed ~SW-NE-oriented Anatolian Background Splitting pattern and recent seismic low-ultra low-velocity anomalies. We argue that this large-scale upper mantle flow constitutes the engine for the long-wavelength dynamic topography (~400 m) in the region and promotes the relatively small-scale convection pattern by supporting intraplate rift tectonics in the extensional Van Lake zone.

How to cite: Şengül Uluocak, E., Pysklywec, R. N., Sembroni, A., Brune, S., and Faccenna, C.: The Role of Upper Mantle Forces in Post-subduction Tectonics: Insights from 3D Thermo-mechanical Models in the East Anatolian Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-330, https://doi.org/10.5194/egusphere-egu24-330, 2024.

  Yanshanian magmatic rocks are widely distributed in the northern margin of the South China Sea and the continental margin of South China. These magmatic rocks are generally believed to have been formed by the subduction of the Paleo-Pacific plate to the South China Plate from Late Jurassic to Early Cretaceous. Due to the small number of wells drilled to the basement, most predecessors have studied on the distribution range, origin and tectonic setting of Yanshanian magmatic rocks by geophysical means(magnetic anomalies and seismic data). At present, The reported ages of basement magmatic rocks in the Pearl River Mouth Basin are mainly concentrated in Zhu 1 Depression and Panyu Low Uplift, and there is no petrological evidence in other regions.Baiyun Depression, as the largest hydrocarbon generating depression in the Pearl River Mouth Basin, has important oil and gas significance. In order to better define the spatial and temporal distribution of Yanshanian magmatic rocks, nearly 30 basement drilling samples in the periphery of Baiyun Depression and 8 onshore outcrop samples were collected. The genesis and tectonic significance of Yanshanian magmatic rocks are discussed through 76 thin sections, 7 U-Pb zircons dating, 26 major elements analysis, 16 trace elements analysis and 4 Sr-Nd-Pb isotope analysis.The results show that the magmatic rocks in the study area are concentrated in the J3-K1 and mainly developed S-type granite. These magmatic rocks are basically derived from the crust, and a few magmatic rocks or a small amount of mantle-derived materials are mixed in. The trace element discrimination diagram indicates that all samples belong to volcanic island arc type granite. The distribution curve of rare earth elements shows that light rare earth elements are enriched and heavy rare earth elements are low and stable.According to the above results, these magmatic rocks are part of the NE-trending continental margin magmatic arc formed by subduction and accretion of the paleo-Pacific plate to the South China Plate during the Yanshanian.Combined with the previous research results, it is believed that the extensional action caused by subduction and retreat of the Paleo-Pacific plate migrated to the ocean direction in the late stage of tensile rupture, and magmatism also migrated to the ocean, so the intrusion time of the magmatic rocks from continental to marine along the NW-SE direction gradually became late.This study adds important petrological evidence to clarify the genesis and tectonic setting of Yanshanian magmatic rocks in the northern margin of the South China Sea and the South China continent, and also has important application value for oil and gas exploration of buried hills in the Pearl River Mouth Basin.

How to cite: lu, F. and zhao, J.: Genesis and Tectonic Setting of Yanshanian Magmatic Rocks in the Northern Margin of South China Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-339, https://doi.org/10.5194/egusphere-egu24-339, 2024.

EGU24-568 | ECS | Posters on site | GD4.1

Trans-Lithospheric Diapirism as a Possible Mechanism for Ophiolite Emplacement? 

Nikola Stanković, Taras Gerya, Vladica Cvetković, and Vesna Cvetkov

Oceanic obduction and ophiolite emplacement are processes which result in positioning of more dense oceanic lithosphere on top of less dense continental crust. It is known that obduction is related to the closure of oceanic realms, however exact mechanisms that lead to the obduction of these ophiolite rocks, and more importantly, their permanent emplacement onto the continental crust is still controversial.

Although many mechanisms for ophiolite emplacement have been proposed, there have been substantial difficulties in modelling the ophiolite emplacement by means of numerical simulations. Creating physically viable simulations of the ophiolite emplacement is of paramount importance for better understanding of the process itself. There have been some notable successful attempts. For example, [1] succeeded in emplacing ophiolites by artificially reversing the velocity conditions once the ophiolite block is already obducted. More recently, [2] have shown that continental extrusion mechanism, which is a result of the activation of subducted continental crust at higher P-T conditions, can account for the emplacement of far-travelled ophiolites.

In this communication, we report interim results of our attempt to explain spontaneous emplacement of large ophiolite blocks by means of trans-lithospheric diapirism of continental crust. This phenomenon has recently been modelled [3] in the context of continental collision and the formation of the European Variscides. However, in this study, we produce a spontaneously induced intra-oceanic subduction. This model involves a retreating subduction with trench reaching the passive continental margin, leading to the continental subduction under very young oceanic lithosphere. Consequently, subducted crust is activated in deeper regions and forms a diapiric upward flow. This trans-lithospheric diapirism reaches the surface, thus separating the already obducted parts of the oceanic lithosphere from the rest of the oceanic domain, resulting in permanent ophiolite emplacement.

The presence of crustal rocks in such deep environments of ultra-high pressure certainly leads to their metamorphism. In the scope of our simulations we are monitoring the P-T paths of relevant crustal markers and propose rough estimates of the P-T conditions of metamorphic peak. For the calculations of the numerical simulations we utilize marker-in-cell method with conservative finite differences [4].

 

[1] T. Duretz, P. Agard, P. Yamato, C. Ducassou, E. B. Burov, and T. V. Gerya, “Thermo-mechanical modeling of the obduction process based on the oman ophiolite case,” Gondwana Research, vol. 32, pp. 1-10, 2016.

[2] K. Porkoláb, T. Duretz, P. Yamato, A. Auzemery, and E. Willingshofer, “Extrusion of subducted crust explains the emplacement of far-travelled ophiolites,” Nature Communications, vol. 12, no. 1, p. 1499, 2021.

[3] P. Maierová, K. Schulmann, P. ’Štípská, T. Gerya, and O. Lexa, “Trans-lithospheric diapirism explains the presence of ultra-high pressure rocks in the european variscides,” Communications Earth & Environment, vol. 2, no. 1, p. 56, 2021.

[4] T. V. Gerya and D. A. Yuen, “Characteristics-based marker-in-cell method with conservative finite-differences schemes for modeling geological flows with strongly variable transport properties,” Physics of the Earth and Planetary Interiors, vol. 140, no. 4, pp. 293-318, 2003.

How to cite: Stanković, N., Gerya, T., Cvetković, V., and Cvetkov, V.: Trans-Lithospheric Diapirism as a Possible Mechanism for Ophiolite Emplacement?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-568, https://doi.org/10.5194/egusphere-egu24-568, 2024.

EGU24-700 | ECS | Posters on site | GD4.1

The British Virgin Islands in the Caribbean Evolution: Petrogeochemical and geochronological constraints 

Noémie Bosc, Delphine Bosch, Mélody Philippon, Mélanie Noury, Olivier Bruguier, Lény Montheil, Douwe van Hinsbergen, and Jean Jacques Cornée

The British Virgin Islands (BVI) is a NE-SW trending archipelago located in the northeastern corner of the Caribbean plate. Exposing volcanic arc rocks, it is located at the junction between the old arc of the Greater Antilles to the Northwest and the active arc of the Lesser Antilles to the South. The BVI are a key location to study the geodynamical evolution of the northeastern boundary of the Caribbean plate. In order to understand its significance into the overall Caribbean evolution, a set of 16 igneous samples from seven islands was studied for petrology, geochemistry (major and trace elements, and Pb-Sr-Nd-Hf isotopes), thermobarometry (Al-in-hornblende) and U-Pb geochronology on accessory minerals (zircon, titanite and apatite). The studied rocks show a typical volcanic arc signature and correspond to a calc-alkaline series, differentiated along a NE/SW gradient. Trace elements patterns show strong negative HFSE anomalies and LILE enrichments. ɛHfi are homogeneous ranging from +11.4 to +14.1 typical of a MORB-type mantle. Magmas were thus originated from a homogeneous mantle corresponding to the mantle wedge, with participation of a slab component. The slab component contribution is estimated to be less than 2% and is dominated by aqueous fluids, except for Peter and Norman Islands. U-Pb ages emphasize an active magmatic period spanning between ~43 Ma and ~30 Ma along a NE-SW younging gradient. This age range and strong geochemical similarities with arc lavas exposed in St Martin and St Barthélémy suggest that the BVI represent the northern continuity of the Eo-Oligocene extinct branch of the Lesser Antilles arc. Crystallization depth of the studied plutonic bodies, estimated by thermobarometric constraints, supports a NE-SW increasing emplacement depth from ~7km to ~13km. The oldest plutonic bodies at NE thus experienced less total exhumation than the youngest plutonic bodies at SW (maximum rate of ~2.2 mm/yr at SW and minimum rate of ~0.2 mm/yr at NE). From Eocene to Oligocene it has been recently demonstrated that the block from Puerto Rico-Virgin Islands (PRVI) rotated 45° counter clockwise (Montheil et al., 2023). Previous thermochronological data shows that the BVI exhumation occurred synchronously along the archipelago between ~25 and ~21 Ma (Román et al., 2021). Together these observations suggest a regional tilt of the BVI block that occurred between plutons crystallisation and their exhumation at ~2 km depth. We propose that the tilting and the fast exhumation of the BVI, that are synchronous with counterclockwise rotation of the PRVI block, are the consequence of subduction locking generated by the Bahamas bank accretion to the northeastern Caribbean plate.

How to cite: Bosc, N., Bosch, D., Philippon, M., Noury, M., Bruguier, O., Montheil, L., van Hinsbergen, D., and Cornée, J. J.: The British Virgin Islands in the Caribbean Evolution: Petrogeochemical and geochronological constraints, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-700, https://doi.org/10.5194/egusphere-egu24-700, 2024.

EGU24-1044 | ECS | Orals | GD4.1

The role of hydration-induced processes in the deformation of the North China craton 

Açelya Ballı Çetiner, Oğuz Göğüş, Jeroen van Hunen, and Ebru Şengül Uluocak

Numerous previous studies have been conducted in the North China Craton to investigate its anomalously thin lithosphere, high magmatism, and extensional tectonics along its eastern margin. Based on petrological analyses it has been suggested that the cratonic mantle lost its root (~100 km) with multiple tectonic processes during the late Jurassic – Early Cretaceous. The weakening and erosion of the North China craton is often attributed to its high water content and lower viscosity of the lithosphere associated with the movement and position of the Paleo-Pacific plate. However, other mechanisms and control parameters for the craton destruction have been proposed, and the thinning of the North China craton remains an enigmatic process.

To have a better understanding of the dynamics of the lithospheric deformations beneath the North China Craton that changes over time, we conducted a series of 2D geodynamic models. Specifically, we investigate the impact of hydration-induced processes on the lithosphere and the overriding plate and focus on parameters such as external tectonic forcing, the rheology and the strength of the overriding plate. Moreover, the effect of the angular position of the oceanic plate, and the existence of the mid-lithosphere discontinuities was also examined. Our results reveal that the destruction of North China Craton is more complex and heterogeneous than is often assumed in modelling studies. Furthermore, we find that without significant weakening, the mantle lithosphere is unlikely to delaminate. Extensive hydrous weakening may account for this, but external tectonic forcing in combination with non-linear rheology and eclogitization of the lower crust may have played an important role too.  

How to cite: Ballı Çetiner, A., Göğüş, O., van Hunen, J., and Şengül Uluocak, E.: The role of hydration-induced processes in the deformation of the North China craton, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1044, https://doi.org/10.5194/egusphere-egu24-1044, 2024.

EGU24-3010 | ECS | Posters on site | GD4.1

Thermo-mechanical models on the missing forearc basement in Taiwan 

Chih-Hsin Chen, Eh Tan, Shu-Huei Hung, and Yuan-Hsi Lee

Taiwan is located at the edge of the Eurasian plate and borders the Philippine Sea plate. The Philippine Sea plate is moving northwestward at a speed of 70 to 80 mm/yr and is converging with the Eurasian plate, forming the Luzon arc and the Taiwan orogenic belt. However, in the middle section of the Taiwan orogenic belt, the Luzon arc is directly adjacent to the edge of the Eurasian continental margin, and the forearc basement is missing. This phenomenon of missing forearc basement is also widely observed in similar plate convergence zones. Previous studies have suggested that this forearc basement has subducted between the Philippine Sea plate and the Eurasian plate. In order to explore the mechanism of forearc basement subduction, we used thermal-mechanical coupled numerical simulations combined with geological data to simulate the dynamic mechanism of forearc basement subduction in the middle section of the Taiwan orogenic belt.

 

The simulation results show that when the subducting plate transitions from oceanic crust to continental crust, the continental crust has a lower density and is not easily subducted. The huge mass formed by the orogeny blocks the Philippine Sea plate from moving northwestward, causing the forearc crust to bend concavely and form a forearc basin. The basin begins to accumulate a large amount of sedimentary material. Later, the center of the basin breaks to form the Longitudinal Valley fault, the island arc to the east of the basin thrusts over the forearc basement, pushing the basin sediment to uplift rapidly, and finally the forearc basement subducts below the Philippine Sea plate.

 

This model explains the mechanism for the missing forearc basement, the timing of the formation of the Longitudinal Valley fault, and the dramatic up and down movements recorded in the sedimentary rocks of the Coastal Mountains. It also explains the spatial pattern of the surface heatflow.

How to cite: Chen, C.-H., Tan, E., Hung, S.-H., and Lee, Y.-H.: Thermo-mechanical models on the missing forearc basement in Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3010, https://doi.org/10.5194/egusphere-egu24-3010, 2024.

EGU24-4122 | ECS | Orals | GD4.1

Investigating Interactions between Subduction Initiation and Plate Reorganizations From A Global Perspective 

Xin Zhou, Nicolas Coltice, and Paul Tackley

Subduction initiation (SI) creates new subduction zones and provides driving forces for plate tectonics, being a key process of theplate tectonic regime on Earth. Although SI has been extensively studied in 2D regional numerical models, obtaining a global perspective on SI remains elusive. Geological observations and plate reconstructions both suggest that SI is coeval with the global or local plate reorganizations. The tectonic plate reorganizations are marked by rapid changes of plate motions occurring over a few million years and are recurrent throughout Earth’s history.  One of the most well-known plate reorganization events occurred at approximately 53-47 Ma ago, characterized by the bending of Hawaii-Emperor Seamount Chain. Simultaneously, several SI events occurred in the Pacific Plate, such as Izu-Bonin-Mariana (~52 Ma) and Tonga-Kermadec (~50 Ma). The relationship between SI and plate reorganizations, as well as their collective impacts on continental evolution, is poorly understood. It is also unclear whether these processes are dominated  by a “top-down” or “bottom-up” mechanism. This study is committed to exploring the interaction between SI and plate reorganizations using 3D global mantle convection models. We reproduce SI coeval with plate reorganizations in these numerical models. We analyze the changes of stress distribution in the lithosphere during the plate reorganizations and their effects on SI. A variety of different interplays between SI and tectonic plates reorganizations have been identified based on their chronology and driving mechanisms. We also investigate their influences on the supercontinental breakup and assembly. Two major plate reorganization events, occurring at 100 Ma and 50 Ma ago respectively, are used to compare with the numerical modeling results. The effects of key parameters, such as lithosphere thickness and strength, will be examined. Plate reconstruction models will also be included to study the interaction between SI and plate reorganizations in the future.

How to cite: Zhou, X., Coltice, N., and Tackley, P.: Investigating Interactions between Subduction Initiation and Plate Reorganizations From A Global Perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4122, https://doi.org/10.5194/egusphere-egu24-4122, 2024.

Subduction initiation remains one of the least understood global processes of plate tectonics.  Prominent models have been cast in terms of two broad classes: “spontaneous” cases due to lithospheric gravitational instabilities and “induced” cases due to forced plate convergence. Yet gravitationally unstable lithosphere is old, strong, and difficult to begin to bend into a subduction zone and convergent forces necessary to begin subduction are often too large given the plates involved. These models also consider the asthenospheric mantle as passive, even though relative motion between slabs and the asthenosphere has long been regarded as a strong control on subduction dynamics. Here I propose that subduction-transform edge propagator (STEP) faults can initiate subduction depending on the absolute motion of the STEP fault with respect to the asthenosphere. STEP faults form where subduction zones end and the subducting plate tears forming a down flexed transcurrent plate boundary at the surface shearing against the adjacent rear arc lithospheric plate. However, STEP faults are not simple transcurrent boundaries. Absolute motion of the down flexed STEP fault edge with respect to the surrounding asthenosphere can produce a strong “sea anchor” force that either continues to bend the edge downward, initiating subduction, or opposes slab bending, inhibiting subduction. In the south Pacific, the southern end of the New Hebrides Trench and the northern end of the Tonga Trench are type-example STEP faults with opposite senses of dip but both moving northward with respect to the asthenosphere. The northward dipping New Hebrides STEP fault moves northward in a mantle reference frame creating a strong asthenospheric flow against the STEP fault edge, inducing active subduction at the Matthew-Hunter trench. In contrast, the Tonga STEP fault dips southward but also has a northward component of motion with respect to the mantle. Asthenosphere thus flows southward beneath the down flexed Tonga STEP fault edge opposing further bending.  Subduction does not initiate at the Tonga STEP fault despite a ~100 Myr age contrast between the Pacific and north Fiji and Lau basin lithospheres. Since absolute plate motions reflect the sum of all forces acting on the entire lithospheric plate, a strong sea anchor mantle force may be generated at a STEP fault edge, initiating subduction (or inhibiting it), even where lithosphere is old, strong, and resists bending and without requiring large convergent forces between plates, overcoming these objections to previous models.

How to cite: Martinez, F.: Subduction initiation (or not) due to absolute plate motion at STEP faults: The New Hebrides vs. the Tonga examples, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4189, https://doi.org/10.5194/egusphere-egu24-4189, 2024.

The migration and character of magmatism over time can provide important insights into the tectonic evolution of an orogen. We present evidence for three separate episodes of compositionally distinct granitoid magmatism associated with the Acadian orogenic cycle in the eastern and southern Newfoundland Appalachians. The interpretations are based on new zircon U-Pb ages, geochemical data, and Sr-Nd-Hf-O isotopic data for 18 samples from 15 Silurian and Devonian granitoid plutons, combined with previously published data. The three episodes outline hinterland and foreland-directed migration trends and represent subduction (435-420 Ma), syn-collision (415-405 Ma), and post-collision (395-370 Ma) settings in the Acadian orogenic cycle. The Silurian plutons (435-420 Ma) consist mainly of quartz diorite, tonalite, granodiorite, monzogranite, and syenogranite, with high-K calc-alkaline and enriched Sr-Nd-Hf-O isotopic compositions (e.g., εNd[t] = -5 to -2; εHf[t] = -3 to -1; δ18O = +6 to +8). They are interpreted to record the subduction of oceanic lithosphere of the Acadian seaway that separated the leading edge of composite Laurentia represented by the Gander margin and Avalonia. The Early Devonian plutons (415-405 Ma), containing more voluminous monzogranite and syenogranite, have calc-alkaline to high-K calc-alkaline features, adakite-like compositions, and more-depleted Sr-Nd-Hf-O isotopic compositions (e.g., εNd[t] = -6 to 0; εHf[t] = +1 to +3; δ18O = +5 to +6). This stage occurs mostly to the northwest of the Silurian, indicating a regional scale northwestward (hinterland-directed) migration of magmatism with a rate of > 9 km/Ma. The migration is interpreted to be related to the progressive shallow underthrusting of Avalonia beneath the Gander margin (composite Laurentia) at least as far as 90 km inboard. The Middle to Late Devonian plutons (395-370 Ma) consists mainly of monzogranite, syenogranite, and alkali-feldspar granite, which are silica- and alkali-rich with large negative Eu anomalies. These rocks are concentrated along both sides of the Dover - Hermitage Bay fault zone, which represents the boundary between Avalonia and composite Laurentia, to the southeast of the Silurian-Early Devonian igneous rocks. This stage of magmatism represents a foreland-directed (retreating) migration. The Early Devonian and Middle to Late Devonian magmatism were separated by a gap between 405 and 395 Ma, and recorded an evolution from (high-K) calc-alkaline to alkaline compositions, which is ascribed to partial delamination of Avalonian lithospheric mantle in a post-collisional setting.

How to cite: Wang, C., Wang, T., Cees, V. S., Hou, Z., and Lin, S.: Evolution of Silurian to Devonian magmatism associated with the Acadian orogenic cycle in Newfoundland Appalachians: Evidence for a three-stage evolution characterized by episodic hinterland- and foreland-directed migration of granitoid magmatism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4216, https://doi.org/10.5194/egusphere-egu24-4216, 2024.

Convergent continental margins are the major sites for the formation, differentiation, preservation, and destruction of continental crust. This article focuses on the Mesozoic crustal modification history of northeastern China from a magmatic perspective. During Mesozoic times, NE China was influenced by three convergent systems, namely the Paleo-Asian Ocean (PAO) regime to the south, the Mongol-Okhotsk Ocean (MOO) regime to the northwest, and the Paleo-Pacific Ocean (PPO) regime to the east. This study comprehensively synthesizes information on Early Triassic to Early Cretaceous magmatic rocks. We unravel the spatiotemporal effects of the above-mentioned convergent regimes by evaluating the migration of major magmatic belts and other geological and geophysical evidence. The PAO regime is confined to the southernmost part of NE China and exerted influence during pre-late Late Triassic times. The MOO regime-related magmatism lasted until the early Early Cretaceous and occurred throughout the Great Xing’an Range and adjacent regions. The spatial effect of the PPO did not exceed the eastern margin of the Songliao Basin until the Early Jurassic; low-angle to flat subduction of the PPO slab led to the westward migration of continental arc front in the Middle Jurassic and the waning of PPO regime-related magmatism in the Late Jurassic. Since the earliest Cretaceous, the rollback and retreat of the PPO slab became the predominant geodynamic control in NE China, but the superposition of the MOO regime played a role during the early Early Cretaceous. Employing whole-rock Nd and zircon Hf isotope spatial imaging, this study elucidates that, although the pre-Mesozoic lithospheric heterogeneity provides first-order control, the Mesozoic crustal architecture of NE China was further carved by Mesozoic tectonics. Retreating subduction (slab rollback) and post-collisional lithospheric delamination resulted in the prolonged extensional background and crustal growth (rejuvenation); on the contrary, low-angle subduction and syn-collisional compression could cause transient periods of ancient crust reworking. Our results also estimate the high altitude of the Great Xing’an Range and adjacent regions in the Early Cretaceous. This study opens new possibilities to explicitly document crustal modification processes in fossil orogens from a magmatic perspective.

How to cite: Huang, H., Wang, T., and Guo, L.: Crustal modification influenced by multiple convergent systems: Insights from Mesozoic magmatism in northeastern China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4240, https://doi.org/10.5194/egusphere-egu24-4240, 2024.

EGU24-4319 | Posters virtual | GD4.1

Towards understanding the interplay between tectonics, magmatism, and sedimentation in the Timok Magmatic Complex (TMC) basin of the Serbian Carpathians 

Uros Stojadinovic, Marinko Toljić, Branislav Trivić, Radoje Pantović, Danica Srećković-Batoćanin, Nemanja Krstekanić, Bojan Kostić, Miloš Velojić, Jelena Stefanović, Nikola Randjelović, and Maja Maleš

Among the many examples observed worldwide, the Timok Magmatic Complex (TMC) basin of the Serbian Carpathians represents an excellent area for a process-oriented study on the interplay between tectonics, sedimentation, and magmatism in continental back-arc basins above evolving subducted slabs. The TMC is a segment of the larger Late Cretaceous Apuseni-Banat-Timok-Srednogorie (ABTS) magmatic belt, formed in response to the subduction of the Mesozoic Neotethys oceanic lithosphere beneath the Carpatho-Balkanides of south-eastern Europe. However, despite many qualitative studies, the quantitative link between the subducted slab's mechanics and the overlying basins' evolution is less understood. Within the scope of the newly funded TMCmod project, supported by the Science Fund of the Republic of Serbia (GRANT No TF C1389-YF/PROJECT No 7461), coupled field and laboratory kinematic and petrological investigations will be focused on creating a conceptual definition of the TMC geodynamic evolution, by combining near-surface observations with the known evolution of the subduction system. This definition will be subsequently validated through analogue modelling and integrated into a coherent geodynamic model of tectonic switching in basins driven by the evolution of subducted slabs. The new geodynamic model coupling the TMC basin with its Neotethys subduction driver will quantitatively advance the strategy of prospecting and exploration of world-class porphyry copper-gold deposits, which have been actively exploited in this region for more than a century. Furthermore, reconstructed regional kinematic evolution will improve seismic hazard assessment during industrial and societal infrastructure planning and construction.

How to cite: Stojadinovic, U., Toljić, M., Trivić, B., Pantović, R., Srećković-Batoćanin, D., Krstekanić, N., Kostić, B., Velojić, M., Stefanović, J., Randjelović, N., and Maleš, M.: Towards understanding the interplay between tectonics, magmatism, and sedimentation in the Timok Magmatic Complex (TMC) basin of the Serbian Carpathians, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4319, https://doi.org/10.5194/egusphere-egu24-4319, 2024.

Previous subduction thermal models are inconsistent with the values of forearc heat flow (50-140 mW/m2) and global P‒T conditions of exhumed rocks, both suggesting a shallow environment 200~300°C warmer than model predictions. Here, we revaluate these problems in Kuril-Kamchatka using 3-D thermomechanical modeling that satisfies the observed subduction history and slab geometry, while our refined 3-D slab thermal state is warmer than that predicted by previous 2-D models and better matches the observations involving exhumed rock records. We show that warmer slabs create hierarchical slab dehydration fronts at various forearc depths, causing fast and slow subduction earthquakes. The multilayered subduction regime and a large downdip thermal gradient of > 5°C/km beneath Kuril-Kamchatka indicate a stratified characteristic effect on slab dehydration efficiency. We conclude that fast-to-slow subduction earthquakes all play a key role in balancing plate coupling energy release on megathrusts trenchward of high P‒T volcanism.

How to cite: Zhu, W. and Ji, Y.: Reestimated slab dehydration fronts in Kuril-Kamchatka using updated three-dimensional slab thermal structure, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4972, https://doi.org/10.5194/egusphere-egu24-4972, 2024.

Oceanic Core Complexes (OCCs) are peridotite and serpentinite rich geological features, commonly located at the external intersections of slow-spreading mid-oceanic accreting ridges (MORs) with transform faults (TFs). The peridotites of these complexes are commonly considered to derive from the upper mantle while the serpentinites are attributed to chemical weathering that affected rock-mass during its ascent through the lithosphere. Description of cores drilled into OCCs commonly describes in detail the various peridotites but ignores the serpentinites, which are considered secondary additions. However, this presumption seems flawed due to the absence of high-pressure rocks such as eclogites, therefore it seems that the origin of the various peridotite minerals were formed concurrently with the serpentinites from pyroxenes under constrains of moderate geological pressures and temperatures, and various availabilities of H2O.

The intersections between slow MORs and TFs, where most OCCs occur, are characterized by steep thermal gradients and by distinct density contrasts. The thermal gradients in the upper crust of the MOR axial rift are nearly 1300/km, due to the shallow depth of the upper mantle there. The density of the fresh basaltic lava at the MOR is ca. 2700 kg/m3, because the temperature of the fresh basalt is some 1100oC. However, the density of the older basalt that builds the older plate across the transform fault is 2900 kg/m3. It is plausible that at fast-spreading MORs the plate juxtaposed against the active spreading rift would still be warm and its density would too light to initiate the spontaneous subduction. Tectonic experiments showed that at least 200 kg/m3 density contrast between lighter and denser crustal slabs would be sufficient to initiate spontaneous subduction. Furthermore, geochemical experimentation shows that under 500oC temperatures, namely at depths of ca. 4 km under the MOR, minerals of the pyroxene group in the oceanic basalts, are likely to be altered either into peridotites under dry conditions or into serpentinites under wet constraints at such temperature. These constraints suggest that the serpentinites in OCCs are generic and not erosional features, and their light densities and plasticity could have generated the diapiric ascent of the OCCs. The density contrast between the fresh and the old basalts, juxtaposed at the ridge – transform junctions, could take place if the spreading rate of the MOR is slow and the older slab has the time required to cool and reach the density of 2900 kg/m3.

 Keywords: Ridge-transform intersection, oceanic core complexes, spontaneous subduction, peridotites, serpentinites, diapirs.

How to cite: Mart, Y.: Oceanic core complexes: Serpentinite diapirs at slow ridge - transform fault intersections?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5261, https://doi.org/10.5194/egusphere-egu24-5261, 2024.

EGU24-5274 | ECS | Orals | GD4.1

Investigating the plate motion of the Adriatic microplate by 3D thermomechanical modelling 

Christian Schuler, Boris Kaus, Eline Le Breton, and Nicolas Riel

The geodynamic evolution of the Alpine-Mediterranean area is complex and still subject to ongoing debate. The Adriatic microplate motion is of particular interest as it is influenced by three distinct subduction systems: the Alpine subduction in the north, the Dinaric-Hellenic subduction in the east, and the Calabrian-Apenninic subduction in the west. Additionally the system is influenced by the northward movement of the African continent, which further contributes to the geodynamic complexity of the region.

In this study, 3D thermomechanical simulations of the Alpine-Mediterranean region are performed using the code LaMEM (Kaus et al., 2016). The simulations employ a viscoelastoplastic rheology and an internal free surface to investigate the internal dynamics of the mantle. The initial plate configuration for the simulations is based on the kinematic reconstructions of Le Breton et al. (2021) at 35 Ma. The objective is to identify the controlling factors that drive the motion of the Adriatic microplate. This is achieved by investigating the role of various model parameters, such as the thermal structure of the lithosphere, the geometry and strength of the continental margin, the mantle viscosity, brittle parameters of the crust and the location of crustal heterogeneities.

Results show that Adria undergoes two distinct phases of plate motion over the past 35 million years. Between 35 Ma and 20 Ma, the African plate moves northward, pushing Adria in the same direction. However, once the Hellenic slab rolls back from the east and the Calabrian and Apenninic slabs roll back from the west, the Adriatic microplate decouples from the African plate, resulting in an anticlockwise rotation of Adria. Overall, this study provides valuable insights into the parameters that affect subduction dynamics in the Mediterranean and the independent motion of the Adriatic microplate.

Kaus, B. J. P., A. A. Popov, T. S. Baumann, A. E. Pusok, A. Bauville, N. Fernandez, and M. Collignon, 2016: Forward and inverse modelling of lithospheric deformation on geological timescales. Proceedings of NIC Symposium.

Le Breton, E., Brune, S., Ustaszewski, K., Zahirovic, S., Seton, M., & Müller, R. D. (2021). Kinematics and extent of the Piemont–Liguria Basin–implications for subduction processes in the Alps. Solid Earth, 12(4), 885-913.

How to cite: Schuler, C., Kaus, B., Le Breton, E., and Riel, N.: Investigating the plate motion of the Adriatic microplate by 3D thermomechanical modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5274, https://doi.org/10.5194/egusphere-egu24-5274, 2024.

Fluid release from dehydration reactions and subsequent fluid migration in the subducting slab control the distribution of fluids in subduction zones, impacting many subduction processes, such as intraslab earthquakes, megathrust earthquakes, episodic slip and tremor, mantle wedge metasomatism, and arc-magma genesis.  Previous numerical models of two-phase flow indicate that compaction-pressure gradients induced by the dehydration reactions could drive updip intraslab fluid flow near the slab surface (Wilson et al., 2014). However, how the initial hydration in the incoming oceanic mantle prior to subduction impacts the updip fluid flow has not been investigated. Here, we use a 2-D two-phase flow model to investigate this effect under various initial slab-mantle hydration states and slab thermal conditions, the latter of which impact the depth extent of the stability of hydrous minerals. We especially focus on quantifying the lateral shift between the site of dehydration reactions and the location at which the fluids reach the slab surface due to their updip migration within the slab. The modeling results show that the most favourable path for updip flow is the antigorite dehydration front, the spatial extent of which depends on the slab-temperature and the thickness of the hydrated slab mantle. Our models predict that slab-derived fluids can travel over tens of km updip within the slab before reaching the slab surface. Such updip migration is more likely in warm(ish)-slabs, in which the formation of the antigorite dehydration front in the slab mantle does not require deep hydration of the incoming oceanic mantle prior to subduction.

How to cite: Cerpa, N. and Wada, I.: Role of degree and depth extent of slab-mantle hydration in controlling the intraslab fluid flow upon dehydration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6007, https://doi.org/10.5194/egusphere-egu24-6007, 2024.

EGU24-6290 | Orals | GD4.1

Can we identify evidence of subduction initiation beneath the Macquarie Ridge Complex from teleseismic tomography? 

Jifei Han, Nick Rawlinson, Hrvoje Tkalčić, Caroline Eakin, Mike Coffin, and Joann Stock

Subduction is a key process in both the recycling and creation of new oceanic crust, the exchange of water between the Earth, oceans and atmosphere, and the distribution of earthquakes and volcanoes. However, the formation of new subduction zones - or subduction initiation - remains a poorly understood process. Macquarie Island, which lies along the Macquarie Ridge Complex (MRC) that forms the transpressional boundary between the Australian and Pacific plates in the southwest Pacific, is one location on Earth where subduction initiation is thought to be taking place. Several studies have suggested that the northern and southern segments of the MRC may be experiencing incipient subduction, but it is unclear what is happening in the central section, which includes Macquarie Island.


Indirect evidence for at least incipient subduction beneath Macquarie Island includes (i) ophiolite (oceanic crust) being exposed above sea level; (2) extreme topography, with Macquarie Island lying  ~5 km above the surrounding ocean basin; (3) thrust faults on either side of the island. To help investigate whether subduction may have been initiated in the neighborhood of Macquarie Island, we analyze teleseismic body wave data recorded by a network consisting of land stations and oceanic bottom seismometers deployed between October 2021 and November 2022. We extract teleseismic P-wave arrival time residuals across the combined array from ~20 events with epicentral distances between 30 and 90 degrees and invert them using FMTOMO to obtain 3-D P-wave velocity anomalies in the upper mantle. Preliminary results indicate that higher velocities are present to the east of the MRC in the vicinity of Macquarie Island, although further refinement is required before a detailed interpretation is possible.

How to cite: Han, J., Rawlinson, N., Tkalčić, H., Eakin, C., Coffin, M., and Stock, J.: Can we identify evidence of subduction initiation beneath the Macquarie Ridge Complex from teleseismic tomography?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6290, https://doi.org/10.5194/egusphere-egu24-6290, 2024.

The spinel phase (wadsleyite, ringwoodite) in the mantle transition zone (MTZ), can contain up to 1–2 wt% of water. However, whether these water reservoirs in the MTZ are filled is debated and, as the result, water content estimates in the MTZ range from less than 1 to up to 11 surface oceans (Ohtani, 2021 and references therein). I test water stability in the MTZ numerically by using 2D hydro-thermomechanical-chemical upper-mantle scale models with phase transitions and water diffusion and percolation in the mantle. Initial conditions correspond to a hydrated stagnant slab segment placed on top of 660 km discontinuity. Numerical model predicts that water diffusion from thermally relaxing slab triggers development of cold hydrous plumes from the slab surface, which are driven by the water-induced buoyancy (Richard and Bercovici, 2009). These plumes rise to and interact with olivine-spinel transition at 410 km. Positive Clapeyron slope of this transition causes cold plume upwellings to spread under it until their temperature rises enough to allow hydrated material to cross the transition. This crossing triggers aqueous fluid release, which rapidly rises upward in form of porosity waives. Relatively low water content and cold temperature of the wet plumes rising from stagnant slabs in the mantle transition zones may suppress hydrous melting above the 410 km discontinuity, thereby disabling the transition-zone water filter effect (Bercovici and Karato, 2002) at this boundary. Based on the results of experiments, we conclude that, due to the intrinsic positive buoyancy of hydrated mantle compared to dry rocks, mantle transition zone can only serve as a transient water reservoir. The duration of water residence mainly depends on the characteristic thermal-chemical relaxation time of subducting slabs in the mantle transition zone. Therefore, average water content in this zone should mainly depend on the average amount of water brought into it by subducting slabs globally during the characteristic relaxation time.

 

References

Bercovici, D., Karato, S., 2003. Whole-mantle convection and the transition zone water filter. Nature, 425, 39–44.

Ohtani, E., 2021. Hydration and Dehydration in Earth's Interior. Annual Review of Earth and Planetary Sciences, 49, 253-278.

Richard, G.C., Bercovici, D., 2009. Water-induced convection in the Earth’s mantle transition zone. J. Geophys. Res. 114, B01205.

How to cite: Gerya, T.: Is mantle transition zone a water reservoir? Yes, but only transient, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6602, https://doi.org/10.5194/egusphere-egu24-6602, 2024.

EGU24-6689 | Orals | GD4.1

Hoop Stresses in Free Subduction on a Sphere 

Neil Ribe, Stephanie Chaillat, Gianluca Gerardi, Alexander Chamolly, and Zhonghai Li

Because Earth's tectonic plates are doubly curved shells, their mechanical behavior during subduction can differ significantly from that of flat plates. We use the boundary-element method to study free (gravity-driven) subduction in 3-D spherical geometry. The model comprises a shell with thickness h and viscosity η1 subducting in a viscous planet with radius R0. Our focus is on the magnitude of the longitudinal normal membrane stress (`hoop stress'), which has no analog in Cartesian geometry. Scaling analysis based on thin-shell theory shows that the resultant (integral across the shell) of the hoop stress obeys the scaling law Tφ ∼ (η1h W/R0) max(1, cotθ) where θ is the colatitude and W is the velocity of the shell normal to its midsurface that is associated with bending. We find that the state of stress in the slab is dominated by the hoop stress, which is 3-7 times larger than the downdip stress. Because the hoop stress is compressive, it can drive longitudinal buckling instabilities. We perform a linear stability analysis of a subducting spherical shell to determine a scaling law for the most unstable wavelength, which we compare with observed shapes of trenches in the Pacific ocean. 

How to cite: Ribe, N., Chaillat, S., Gerardi, G., Chamolly, A., and Li, Z.: Hoop Stresses in Free Subduction on a Sphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6689, https://doi.org/10.5194/egusphere-egu24-6689, 2024.

The dynamics of subducting lithosphere with an embedded continental fragment is complex, with rapid changes in plate kinematics, mantle flow and uplift of the overriding plate as the fragment impacts the trench. However, the sequence and timing of the effects is often difficult to constrain, leading to uncertainties in the exact causes for particular subduction zones. We conducted 2D and 3D numerical modelling of subduction with Underworld2.0 to investigate the interactions between the subducting lithosphere and an embedded continental fragment, the Eratosthenes Seamount in the Cyprus subduction zone. Due to the uncertainty in the size of the continental crust around the Eratosthenes Seamount, we varied the size of the fragment from 200 km to 400 km (trench perpendicular) and compared to 3D model with a fixed seamount. The 3D model matches the regional seismic tomography models that show the absence of lithosphere on the subducting slab ahead of the continental fragment. In all the models, the subduction zone first develops as expected as the continental fragment approaches the trench. As the fragment contacts the trench at 6.5 Ma, the first uplift in Anatolia is experienced. However, the pace of uplift increases dramatically at 450 ka as the slab tear develops and the mantle flow pattern changes. The observed uplift rate before 450 ka is 0.07 mm/yr while after 450 ka, the uplift rate increases to 3.21 – 3.42 mm/yr. The model that best matches the size of the fragment is 200 km with a rate of 0.04 mm/yr before 450 ka and 1.76 mm/yr after 450 ka. The reference uplift rate from the model without the slab break-off from 450 ka is only 0.02 mm/yr.  The models demonstrate that the slab tear and break-off caused by the impact of the Eratosthenes Seamount causes the uplift observed and in particular is responsible for the more rapid uplift rates observed since 450 ka in the Central Taurides. 

How to cite: Clark, S. and Lou, P.: The Acceleration of Uplift in the Central Taurides due to Continental Fragment Collision in the Subduction Zone of the Eastern Anatolian Region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7174, https://doi.org/10.5194/egusphere-egu24-7174, 2024.

EGU24-7864 | Orals | GD4.1

Folding of subducting slabs controls their deep thermal structures in the mantle transition zone  

Fanny Garel, Nestor Cerpa, Hana Čížková, Xavier Vergeron, Diane Arcay, Serge Lallemand, and Cécilia Cadio

The thermal structure of slabs is thought to be a key parameter for deep-focus earthquakes in subduction zones, since most proposed mechanisms, such as transformational faulting, dehydration reactions or shear instabilities, are controlled by temperature. However, the classical (shallow) thermal parameter "phi", associated to the downward advection of isotherms and approximated as slab age x sinking velocity (Kirby et al., 1996), does not explain deep-focus seismicity occurring in relativelty “hot” subduction zones, e.g. under Bolivia.

 

On the other hand, the various morphologies if subducting slabs imaged by seismic tomography reveal reveal the diversity of slab deformation histories in the transition zone as they reach the high-viscosity lower mantle, e.g. folding, deflection, vertical piling.

 

Using numerical models of subduction dynamics, we propose here to characterize the spatio-temporal evolution of deep thermal structures of subducted slabs throughout various subduction scenarios. We investigate how the maximum depth reached by a given isotherm vary through time (up to 200 km for a given subduction zone). In particular, we evidence the key control of the history of slab-folding in the transition zone (folding amplitude and frequency), associated to e.g. slab viscosity and buoyancy.

 

Hence the past dynamics of subduction zones, in addition to present-day subduction parameters, has to be taken into account to predict slabs thermal structures.

 

This work is part of ANR project RheoBreak (ANR-21-CE49-0009).

How to cite: Garel, F., Cerpa, N., Čížková, H., Vergeron, X., Arcay, D., Lallemand, S., and Cadio, C.: Folding of subducting slabs controls their deep thermal structures in the mantle transition zone , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7864, https://doi.org/10.5194/egusphere-egu24-7864, 2024.

EGU24-8053 | Posters on site | GD4.1 | Highlight

Gibraltar subduction zone is invading the Atlantic 

Joao C. Duarte, Nicolas Riel, Filipe M. Rosas, Anton Popov, Christian Schuler, and Boris J.P. Kaus

Subduction initiation is a cornerstone of the Wilson cycle. It marks the turning point in an ocean’s lifetime, allowing its oceanic lithosphere to be recycled back into the mantle. However, forming new subduction zones in Atlantic-type oceans is challenging, as it commonly involves the action of an external force, such as the slab pull from a nearby subduction zone, a far-field compression or the impact of a mantle plume. Notwithstanding, the Atlantic Ocean already has two fully developed subduction zones, the Lesser Antilles and the Scotia arcs. These subduction zones have been forced from the nearby Pacific subduction zones. The Gibraltar Arc is another place where a subduction zone is invading the Atlantic. This corresponds to a direct migration of a subduction zone that developed in the dying Mediterranean basin. Nevertheless, few authors consider the Gibraltar subduction zone as still active because it has significantly slowed down in the last millions of years. Here, we present new 3D buoyancy-driven geodynamic models, using the code LaMEM, that reproduce the first-order evolution of the Western Mediterranean, show how the Gibraltar Arc may have formed and test if it is still active. The numerical simulations are validated using geological and geophysical data. The results suggest that the Gibraltar arc is still active and will propagate further into the Atlantic after a period of tectonic quiescence. The models also show how a subduction zone starting in a closing ocean (the Ligurian) can migrate on its own into a new opening ocean (the Atlantic) through a narrow oceanic corridor. Subduction invasion is likely a common mechanism for introducing new subduction zones in Atlantic-type oceans and a fundamental process in the recent geological evolution of Earth.

 

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). JCD also acknowledges FCT a CEEC Inst. 2018, CEECINST/00032/2018/CP1523/CT0002 (https://doi.org/10.54499/CEECINST/00032/2018/CP1523/CT0002).

How to cite: Duarte, J. C., Riel, N., Rosas, F. M., Popov, A., Schuler, C., and Kaus, B. J. P.: Gibraltar subduction zone is invading the Atlantic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8053, https://doi.org/10.5194/egusphere-egu24-8053, 2024.

EGU24-8155 | ECS | Posters on site | GD4.1

Insights into Asymmetric Back-Arc Basin Formation in the Mariana Trough at 17°N from Traveltime Tomography 

Helene-Sophie Hilbert, Anke Dannowski, Ingo Grevemeyer, Christian Berndt, Shuichi Kodaira, Gou Fujie, and Narumi Takahashi

The Mariana Trough is the youngest back-arc basin in a series of basins and arcs that developed behind the Izu-Bonin-Mariana subduction zone in the western Pacific. In addition to active seafloor spreading, the Mariana Trough also exhibits a pronounced asymmetry, with the spreading axis closer to the Mariana Arc. The formation and development of this back-arc basin and its predecessor is controlled by a complex interplay of temporal mantle heterogeneities, subduction dynamics of the Pacific Plate and large-scale tectonics since ~50 Ma. Here, we present new insights into the development of the central Mariana Trough at ~17°N from analyses of a 2-D P-wave traveltime tomography together with high-resolution bathymetric data. The refraction and wide-angle reflection data have been recorded by R/V KAIYO (JAMSTEC) on 41 ocean bottom seismometers (OBSs) along a 250 km profile in 2003. The results allow a subdivision of the Mariana Trough into different stages of back-arc basin opening and seem to imply a transition from symmetric rifting to asymmetric seafloor spreading. Fast-velocities in the lower crust in the rifting domain indicate that magma generation and crust formation was highly affected by hydrous melting from the subducting slab during this stage. This slab contribution decreases with the onset of active seafloor spreading due to a change in mantle flow and hence seems to be accompanied by a tectonic rearrangement of the eastern side of the basin.

How to cite: Hilbert, H.-S., Dannowski, A., Grevemeyer, I., Berndt, C., Kodaira, S., Fujie, G., and Takahashi, N.: Insights into Asymmetric Back-Arc Basin Formation in the Mariana Trough at 17°N from Traveltime Tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8155, https://doi.org/10.5194/egusphere-egu24-8155, 2024.

EGU24-8282 | ECS | Orals | GD4.1 | Highlight

A twisted ribbon of subducted lithosphere beneath southeast Anatolia and its seismotectonic implications 

Sonia Yeung, Gordon Lister, Wim Spakman, Oğuz Göğüş, Marnie Forster, Adam Simmons, and Hielke Jelsma

Forensic analysis of the geological architecture in the aftermath of destructive earthquakes is an essential step to identify controlling structures that need to be monitored. Here we suggest the sequence of events during the February 2023 Turkey–Syria earthquakes was driven by the roll back of a twisted ribbon of subducted lithosphere beneath southeast Anatolia. We assume that the February 2023 Turkey–Syria earthquakes were short-term manifestations of a longer-term tectonic process. To investigate, we built a three-dimensional (3D) mesh frame defining the geometry of subducted Tethyan lithosphere in the Eastern Mediterranean, using the UU-P07 global tomography model, and where appropriate, earthquake hypocentre sets from the Global Centroid Moment Tensor project (GCMT) and from the International Seismic Centre (ISC). The 3D model of the subducted Tethyan lithosphere exhibits three variably twisted ribbons. The Cyprus ribbon is subducted to ~280 km depth and is ~120 km wide, and it twists and curls parallel to its length by ~20 degrees anticlockwise.

The geometry prior to subduction can be estimated by floating the mesh back to the surface using the Pplates program. The process of subduction can be visualised by incorporating the floated mesh into a 2D+time tectonic reconstruction from 125 Ma to the present. This leads to the inference that the ribbons are associated with slab tearing during roll back of the Tethyan lithosphere, due to the accretion of the Lycian block and the Cyprus promontory. The twisting motions can be related to a lateral push sideways caused by anticlockwise vertical axis rotation of the Arabia indenter during opening of the Red Sea rift and the Gulf of Aden. We suggest that the Anatolian lithosphere is being stretched by ongoing differential roll back caused by drag of the Cyprus ribbon through the asthenosphere underlying southeast Anatolia. This motion continually triggers failure along strike-slip faults while facilitating the continued indentation of Arabia. Seismotectonic analysis of aftershock sequences highlights the underlying geodynamics.

How to cite: Yeung, S., Lister, G., Spakman, W., Göğüş, O., Forster, M., Simmons, A., and Jelsma, H.: A twisted ribbon of subducted lithosphere beneath southeast Anatolia and its seismotectonic implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8282, https://doi.org/10.5194/egusphere-egu24-8282, 2024.

EGU24-8760 | ECS | Orals | GD4.1

Mantle Oxidation Driven by the Redox Dynamics of the Mariana-Type Subduction 

Wenyong Duan, James Connolly, Peter van Keken, Taras Gerya, and Sanzhong Li

Oceanic plates descending into subduction zones transport a significant amount of oxidized material to both the subduction zone and the Earth's deeper layers (Wood et al. 1990). However, the specific mechanism of mass transfer and the corresponding flux released at different depths remains unclear. Through the use of numerical modeling and a coupled geochemical database, we examined redox dynamics in subduction zones, particularly focusing on Mariana-type subduction zones, representative of the modern plate tectonic regime (Yao et al., 2021).

Our findings highlight two primary mechanisms in the mantle oxidation processes related to subduction. Firstly, desulfurization enables subduction fluids to carry substantial oxidation fluxes into the sub-arc mantle. Mass balance calculations emphasize the sufficiency of these fluxes in oxidizing both the arc magma and mantle wedge, with the hydrated mantle being the primary fluid contributor, followed by the altered oceanic crust. Secondly, partial melting of slab-top rocks, where Fe3+-rich melts from sediments and altered oceanic crust play a predominant role in the oxidation of the back-arc mantle. Importantly, during Mariana-type subduction, the majority of oxidation fluxes penetrate the deeper mantle with subducting slabs. According to our models, we illustrate that during the modern era of plate tectonics, the oxidation fluxes generated by Mariana-type subduction zones had a significant global impact on Earth's mantle redox evolution and the oxygenation of our planet.

References

Wood, B. J., Bryndzia, T., Johnson, K. E. Mantle oxidation state and its relationship to tectonic environment and fluid speciation. Science 248, 337-345 (1990).

Yao, J., Cawood, P. A., Zhao, G., Han, Y., Xia, X., Liu, Q., Wang, P. Mariana-type ophiolites constrain the establishment of modern plate tectonic regime during Gondwana assembly. Nat. Commun. 12(1), 4189 (2021).

How to cite: Duan, W., Connolly, J., van Keken, P., Gerya, T., and Li, S.: Mantle Oxidation Driven by the Redox Dynamics of the Mariana-Type Subduction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8760, https://doi.org/10.5194/egusphere-egu24-8760, 2024.

EGU24-8783 | Posters on site | GD4.1

Unveiling parental compositions in Andean-type intrusions through magma mingling zones 

Daniel Gómez Frutos and Antonio Castro

An important task in petrology is the successful identification of the parental that birthed the magmas constituting the continental crust. Among these, an intermediate parental to subduction related magmas, often referred to as Andean-type, has been determined experimentally in various works. However, identification of a natural rock matching the model compositions has not been accomplished. This difficulty arises primarily from prolonged cooling times, leading to large-scale fractionation and impeding the preservation of the parental magmas. In this regard, quenching becomes a valuable phenomenon, precluding differentiation and thereby preserving the initial compositions. This highlights the relevance of magma mingling zones, a common feature of Andean-type batholiths, as optimal places to probe for parental compositions. Following these considerations, a new set of geochemical analyses from the Gerena magma mingling zone, an Andean-type intrusion in southwest Iberia, is presented to address this problematic. Sampling focused on dark bodies, presumed to be mafic to intermediate in composition. Interestingly, combined evidence from major, trace element and Sr and Sm isotopes suggest that the smaller dark bodies have undergone precluded differentiation. Moreover, according to geochemical modelling their composition can reproduce the neighbouring granites and cumulates through differentiation. These findings emphasize the importance of magma mingling zones as valuable sources of information and shed new light in the identification of the parental composition to Andean-type magmatism.

How to cite: Gómez Frutos, D. and Castro, A.: Unveiling parental compositions in Andean-type intrusions through magma mingling zones, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8783, https://doi.org/10.5194/egusphere-egu24-8783, 2024.

        The East Kunlun orogenic belt represents a typical accretionary orogenic belt and has undergone an evolutionary process from the Proto-Tethys to the Paleo-Tethys oceans. The Late Triassic period witnessed the East Kunlun transitioning into the post-collisional extensional tectonic setting. However, there is ongoing debate regarding the dynamic mechanism responsible for the post-collisional extension. This study conducts the lithological, geochronological, and geochemical characteristics of the Yeniugou gabbros to shed light on the dynamic mechanism. Zircon geochronology suggests that the gabbros formed in the Late Triassic, ca. 207–209 Ma. Furthermore, the positive εHf (t) values (0.1–5.7), the relatively high values of Mg# (42.2–59.4), as well as the elevated contents of the compatible element (V, Cr, Co, Ni), suggest a mantle source with the contributions from asthenospheric mantle constituents. Additionally, gabbros are enriched in LREE and LILEs (Rb, Ba, Th, U, Sr), and depleted in HFSEs (i.e., Nb, Ta, Ti, Zr), suggesting the incorporation of arc-related enrichment components. The higher values of La/Sm, Th/Yb, Th/La, and lower values of Ba/Th, Ba/La, and Lu/Hf indicate that the enriched components are derived from the melting of the terrigenous sediment. The higher Zr/Y ratios, Nb contents, moderate Zr, Y contents, and the positive correlation between clinopyroxene Alz and TiO2, imply that these rocks were formed within an extensional tectonic setting, where upwelling of asthenospheric mantle caused partial melting of metamorphosed lithospheric mantle. Our new investigations support the interpretation that E-KOB experienced the thickening lithospheric delamination during the Late Triassic.

How to cite: Zhang, B., Dong, Y., Sun, S., and He, D.: Petrogenesis and tectonic implications of the late Triassic gabbro in southern East Kunlun Orogenic Belt, northern Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10243, https://doi.org/10.5194/egusphere-egu24-10243, 2024.

EGU24-10304 | Orals | GD4.1

Dynamics of subducting slabs and origin of deep-focus earthquakes 

Hana Čížková, Jakub Pokorný, Craig Bina, and Arie van den Berg

Most earthquakes are associated with subduction zones. While earthquakes occur on very short time scales, they reflect thermal conditions and stress state attained in the subducted slab during its long term evolution. The source models of deep earthquakes thus might provide unique information about stress distribution in subduction zones which could be used to constrain geodynamic models.  

In the Tonga region, ordinary deep (620-680 km) earthquakes exhibit down-dip compressional stresses as expected, but unusually deep (≥680 km) earthquakes have unique focal mechanisms with vertical tension and horizontal compression. Here we employ geodynamic slab models to investigate the effects of the phase transitions and rheology on the stress and thermal state in Tonga slab in the transition zone and shallow lower mantle and we discuss its relation to deep earthquakes. We show that the direct buoyancy effects of the endothermic transition at 660 km depth are overprinted by bending-related forces and resistance from the more viscous lower mantle transmitted by a strong slab up-dip. The stress pattern that best fits seismogenic stresses is found for the cold plate (150 Myr old) and a viscosity increase at 1000 km depth. An abrupt change in stress orientations occurs as the slab temporarily deflected by the endothermic phase transition penetrates the shallow lower mantle while the fold in the flat-lying part tightens.

How to cite: Čížková, H., Pokorný, J., Bina, C., and van den Berg, A.: Dynamics of subducting slabs and origin of deep-focus earthquakes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10304, https://doi.org/10.5194/egusphere-egu24-10304, 2024.

EGU24-10345 | ECS | Orals | GD4.1

Subduction initiation, propagation and progression recorded along the Sulu and Celebes seas (SE Asia) 

Patricia Cadenas Martínez and César R. Ranero

The inception of a subduction system delineates the birth of a destructive plate boundary that constrains the closure of Earth´s oceans. Material and structures of the transient stage between the reactivation of a passive margin and the establishment of a self-sustaining subduction zone are rarely-preserved in the geological record of fossil subduction zones, and natural examples of currently ongoing subduction initiation are scarce. Reported Cenozoic fossil examples have been interpreted to illustrate successive immature stages of plate rupture, underthrusting and the formation of a volcanic arc, all prior to the formation of a mature self-sustained subduction zone. However, many uncertainties about the processes and the kinematics of subduction initiation remain, due to the scarcity- and lack of recent studies- of examples recording the plate rupture and decoupling, the transition to underthrusting, and the formation of the mega-thrust fault.

We use seismic images to study active subduction initiation and plate-boundary propagation in the Sulu and Celebes seas located in SE Asia. The two basins formed in Paleogene to Lower Miocene time and since possibly late Miocene, a phase of contractional deformation has led to the creation of the subduction trenches. The Sulu Trench is growing and laterally propagating along the SE margin of the Sulu Sea basin, and the Cotobato and North Sulawesi trenches propagate along the northeastern and southern margins of the Celebes Sea basin.

We reprocessed and interpreted >4857 km of 2D seismic reflection profiles that image the structure across three active trenches and the regions where the trenches are laterally propagating and display likely related deformation. We identified and mapped subduction-related structural domains of the downing and overriding plates. The megathrust plate boundary reaching the surface separates a trench filled with turbidites from the thrusts sheets of accretionary prisms, overlain with a forearc basin. The images show pre-existing faults and first-order seismo-stratigraphic horizons along the continental margins away from the trench, and the deformation structures associated to their reactivation and possibly linked to either lateral propagation of the subduction trenches or perhaps the local formation of a new trench.

The images illustrate the transition from diffuse deformation to two decoupled plates and to along-strike structural variations of subduction-related structural domains. We show for the first time how the three trenches record the spatial variability of currently active deformation associated to stages of passive margin reactivation, subduction initiation, propagation and progression. These results provide novel insights to further investigate and constrain unsolved questions about the initiation and development of subduction zones.

How to cite: Cadenas Martínez, P. and R. Ranero, C.: Subduction initiation, propagation and progression recorded along the Sulu and Celebes seas (SE Asia), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10345, https://doi.org/10.5194/egusphere-egu24-10345, 2024.

EGU24-10454 | Orals | GD4.1

Compaction pressure goes global: Investigating fluid release and flow in subduction zones worldwide 

Peter E. van Keken, Cian R. Wilson, and Geoff A. Abers

Subduction of oceanic slabs causes the influx of fluids through hydrated phases. Fluids are released by metamorphic dehydration reactions particularly when the slab comes in contact with the hot mantle wedge at depths greater than ~80 km. Fluid release can be diverse and occur at different depths inside the oceanic slab with sediments and uppermost oceanic crust generally dehydrating before the serpentinized mantle and gabbroic sections.

Significant progress has been made in recent years on geophysical imaging of subduction zones that highlight the thermal structure, the location of metamorphic dehydration reactions, and the presence of fluids in slab and mantle wedge (e.g., Kita et al., Tectonophysics, 2010; van Keken et al., Solid Earth, 2012; Shiina et al., GRL, 2013; Pommier and Evans, Geosphere, 2017, Abers et al., Nature Geoscience, 2017). In a complimentary fashion, geodynamical modeling provides first principles constraints on how fluids are released and transported.

Using a simplified modeling geometry, Wilson et al. (EPSL, 2014) showed the importance of compaction pressure gradients as an oft cited, but also frequently ignored, driving force for fluids in the slab. The inclusion of compaction pressure gradients causes the fluids to both be driven from their source to the arc and flow up in part parallel to the slab surface, explaining to at least some extent geophysical observations.

We have modeled the effects of compaction pressure gradients in a global set of subduction zone models (van Keken and Wilson, PEPS, 2023) and show that focusing of the fluids below the typical arc location (at where the slab is at about 100 km depth) is a common feature and that therefore the compaction pressure effects, along with the geometry of the cold corner in the mantle wedge, can naturally explain the position of the arc above subduction zones globally.

How to cite: van Keken, P. E., Wilson, C. R., and Abers, G. A.: Compaction pressure goes global: Investigating fluid release and flow in subduction zones worldwide, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10454, https://doi.org/10.5194/egusphere-egu24-10454, 2024.

EGU24-10800 | ECS | Orals | GD4.1

Gravimetric signature of subducted slabs’ deep thermal structures. 

Xavier Vergeron, Cécilia Cadio, and Fanny Garel

At subduction zones, cold lithospheric plates dive deep into the hotter Earth’s mantle. Earthquakes can occur at depths of hundreds of kilometers in these cold subducted slabs, apparently related to their thermal structures. Seismic tomography provides a first-order information on slab morphology but cannot discriminate « cold » from « warm » slabs partly due to the inhomogeneous repartition of seismic sources and surface sensors. This study investigates the potential of the gravity data from the GOCE mission to infer deep slabs’ inner thermal structures (> 200 km depth). Thermal structures of slabs with various morphologies are derived from dynamic subduction zones models. We convert temperature field into density assuming mineralogical phases at thermodynamical equilibrium for pyrolite mantle using HeFESTo model (Stixrude and Lithgow-Bertelloni 2011). We then use the freeware DynG3 (Cadio et al. 2011) to predict surface and CMB deflections due to slab dynamic sinking – depending on the radial mantle viscosity – and calculate the corresponding synthetic signals (geoid, gravity disturbance, gravity gradients). Our parametric study considers various radial mantle viscosity profiles, slab morphologies and slabs inner thermal structures (SITS). As expected, geoid and gravity gradients are sensitive to density anomalies at different depth ranges. We highlight linear relationships between both these signal for a given viscosity profile and a given slab’s morphology :

  • First, the colder an isothermal slab, the higher the geoid and gravity gradients anomalies.

  • Second, for a given shallow temperature, the colder the deep slab (>500 km), the lower the gravity gradient anomaly and the higher the geoid anomaly.

This last, counter-intuitive, result is explained by the fact that the long wavelength component associated to deep density anomaly overprints, for colder slabs, the short wavelength component associated to surface deflection. Thus, for a known viscosity profile and slab morphology, both shallow (~ 200-500 km depth) and mean slab thermal structures could be inverted from the combination of geoid and gravity gradients anomalies.

How to cite: Vergeron, X., Cadio, C., and Garel, F.: Gravimetric signature of subducted slabs’ deep thermal structures., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10800, https://doi.org/10.5194/egusphere-egu24-10800, 2024.

Subduction zone plate boundary shear zones are often heterogenous, polyrheological units with a block-in-matrix structure analogous to exhumed mélanges. Field study of these units reveal extreme variability in block and matrix lithologies, geometries, and internal structures. Subduction zone plate interfaces are host to a wide range of slip magnitudes and velocities, including some of the largest earthquakes on our planet.

Previous studies on the mechanical behaviour of these mélange units in shear zones have shown that the material properties of the blocks and matrix, as well as the proportions of each, strongly influence the rheological behaviour of the zone. Analysis of the Osa Mélange in SW Costa Rica has also shown that blocks may be weakened by alteration and brecciation, and/or the matrix strengthened by diagenesis/metamorphism, such that the blocks become weaker than their surrounding matrix at shallow depths of subduction. Rheological inversion may also occur at greater depths by processes such as heterogenous dehydration of serpentinite. Such an inversion of the typically-envisaged rheological relationship can have a profound influence on the distribution of stresses, location of ruptures, and the resultant slip behaviour. 

Using COMSOL Metaphysics, we conducted a systematic series of finite element numerical experiments of simple-shear in models consisting of one or multiple inclusions. The geometry, arrangement, number, and material properties of these inclusions were varied systematically — as was the material properties of the surrounding matrix — and the magnitude and location of von Mises stress minima and maxima were recorded. These experiments assessed varying the Young’s Modulus of blocks and matrix from Eblock > Ematrix to Ematrix > Eblock in comparison to varying block proportion, block aspect ratio, block angularity, block rotation angle, and the difference in Poisson’s ratio between the blocks and the matrix. 

Our data shows that the difference in Young’s Modulus between the blocks and the matrix has a greater influence on the magnitude and structure of the stress field than any other studied factor and that weak blocks in a strong matrix lead to significantly greater accumulated stresses in all geometrical configurations. Whether the blocks or matrix are expected to yield first will depend on the interplay between the difference in strength and the difference in Young’s Modulus of the two materials. In the inverted rheological relationship, failure in one block leads to greater increases in the stresses in neighbouring blocks than in the normal rheological relationship.

Clustered failure of blocks in a subduction channel has been proposed as a causal mechanism for non-volcanic tremor, with the accompanying accelerated strain being analogous to slow slip events. Rheological inversion markedly increases the likelihood that blocks fail before the matrix and that failure of one block triggers a cascade of similar failure events. This study demonstrates the significance of rheological inversion to considerations of the mechanics of subduction zone plate boundary shear zones.

How to cite: Clarke, A., Vannucchi, P., and Morgan, J.: Weak Blocks in a Strong Matrix: Exploring parameter-spaces for the biggest controls on subduction interface mechanics , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11199, https://doi.org/10.5194/egusphere-egu24-11199, 2024.

EGU24-12008 | ECS | Posters on site | GD4.1

On The Timing of Collision Induced Slab Break-Off and Polarity Reversal 

Erkan Gün, Philip Heron, Russell Pysklywec, Gültekin Topuz, and Oğuz Göğüş

The subduction process is the main driver of tectonic plate movements and can carry different-sized, thick crustal materials (i.e., continents, oceanic plateaux, seamounts, volcanic arcs) to the subduction trenches through the consumption of oceanic plates. The arrival of these allochthonous terranes to the subduction channel and their accretion to the overriding plate (fully or partly) can often halt the subduction process. Such a subduction-choking event is usually followed by slab break-off or polarity reversal if an ocean-ocean subduction setting is present. While these two types of post-subduction termination events are well-documented in the literature, their timing following a collision is often overlooked.

Here, we present an extensive compilation of scientific literature that shows slab break-off and subduction polarity reversal (flip) events following a collision can happen in a very short time interval. Evidence from contemporary and paleo-subduction zones (i.e., Ontong Java Plateau, Taiwan/Ryukyu Arc, Banda Arc, Philippine Trench, Caribbean Oceanic Plateau, Central Apennines, India-Asia collision) suggests that these major subduction dynamic changes can occur, on average, in 2.5 to 4.5 Myr. The findings of our numerical subduction models are in accordance with the literature and demonstrate that the required time for collision-induced break-off and polarity flip can be as short as ~2 Myr. Our recent numerical modeling work, focusing on allochthonous terranes (microcontinents and oceanic plateaux), explains a potential mechanism for these fast geodynamic events. The slab pull force can stretch and weaken the trench side of drifting terranes. Following arrival in the subduction channel, this weakened portion of terranes is easier to break, yielding a fast detachment of subducting slabs.

How to cite: Gün, E., Heron, P., Pysklywec, R., Topuz, G., and Göğüş, O.: On The Timing of Collision Induced Slab Break-Off and Polarity Reversal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12008, https://doi.org/10.5194/egusphere-egu24-12008, 2024.

EGU24-12731 | Orals | GD4.1

The Seismic Expression and Tectonomagmatic Evolution of Subduction Termination along the Anatolian Margin  

Jonathan Delph, Mary Reid, Daniel Portner, Susan Beck, A. Arda Ozacar, W. Kirk Schleiffarth, Michael Darin, Donna Whitney, Michael Cosca, Christian Teyssier, Nuretdin Kaymakci, and Eric Sandvol

The geological expression of subduction termination is poorly understood due to overprinting during the collisional stage of the Wilson Cycle. The Anatolian domain of the eastern Mediterranean represents a modern system where spatial variability can be interpreted in terms of the transition from subduction to collision. Convergence in the west is accommodated by the subduction of the last remnants of Neotethyan oceanic lithosphere, while in the east, the margin has transitioned to complete continent-continent collision. In central Anatolia, however, the expression of convergence is complicated by the underthrusting of small continental fragments and attenuated continental lithosphere. By investigating variations in the geological expression of convergence across this system, we can investigate the processes that accompany the transition from subduction to collision.

Spatially variable tectonomagmatic and seismic characteristics along the Anatolian margin reflect this transition. Seismic images reveal a disjointed and disaggregating subducting slab beneath central Anatolia that interacts with, and in some cases induces, mantle flow. This spatially corresponds with Miocene-to-recent volcanism that is sourced from very shallow depths (<60 km) and has a southwestward younging pattern to the initiation of magmatism. Primitive melts in the region contain metasomatized lithospheric mantle and asthenosphere signatures resulting from the long-lived subduction history of the margin combined with recent slab rollback and mantle upwelling around the subducting slab edge based on seismic images. Superimposed on regional magmatic trends, local spatiotemporal patterns show subtle southward and westward younging and/or broadening, perhaps associated with thermomagmatic erosion of the lithosphere along relict structures and/or slab edge-induced flow. Conversely, seismic images in eastern Anatolia reveal a nearly uniform mantle flow and no discernable evidence for subduction. Interestingly, magmatic patterns in central and eastern Anatolia bifurcate in the early to mid-Miocene, interpreted as the time when a vertical slab tear developed along the once continuous Tethyan slab. These results indicate that expressions of subduction termination can be very heterogenous along the strike of a margin.

How to cite: Delph, J., Reid, M., Portner, D., Beck, S., Ozacar, A. A., Schleiffarth, W. K., Darin, M., Whitney, D., Cosca, M., Teyssier, C., Kaymakci, N., and Sandvol, E.: The Seismic Expression and Tectonomagmatic Evolution of Subduction Termination along the Anatolian Margin , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12731, https://doi.org/10.5194/egusphere-egu24-12731, 2024.

EGU24-12869 | Posters on site | GD4.1

Deep lithospheric controls on the formation and evolution of the East Anatolian Fault Zone and Anatolia-Arabia-Africa Triple Junction 

Jonathan Delph, Michael Darin, Donna Whitney, Michael Cosca, Christian Teyssier, Tuna Eken, Nuretdin Kaymakci, Mary Reid, and Susan Beck

The North and East Anatolian Fault Zones represent plate-bounding transform faults that enable the westward tectonic escape of the Anatolian Plate away from the Arabian-Eurasian collisional zone. These fault zones are both capable of hosting large (Mw > 7) seismic events, as most recently demonstrated by the extremely damaging February 2023 Kahramanmaraş earthquake sequence. This earthquake sequence highlighted that plate boundary forces in this area are distributed over a very broad region, however what controls the location, distribution, and character of this plate-bounding strike-slip system remains enigmatic. To better understand potential contributions to deformation, we compare seismic images of the lithosphere (e.g., crustal and lithospheric mantle thickness and velocity) to deformational features and seismicity near the EAFZ, as well as further west where it joins with the Anatolia-Arabia-Africa (A3) triple junction along the southeastern margin of the Anatolian escape system. We interpret that although controls on surface deformation are commonly linked to stress in the brittle upper crust, the complex deformation and seismicity patterns in this region are likely related to variations in the location and extent of the strong lithospheric mantle of the Arabian plate, which currently underthrusts Anatolia as far north as the Sürgü-Çardak fault zone (~50 km). In addition, the Arabian lithospheric mantle extends at least as far west as at least the central Adana Basin, coincident with a zone of relatively deep (>30 km) strike-slip seismogenesis that has produced Mw > 6 earthquakes. By investigating the relationship between recent geological deformation since the inception of the East Anatolian Fault (ca. 5 Ma) and the modern record of seismic structure and seismicity, we infer that the Sürgü-Çardak fault zone and its associated near-orthogonal bend reaching into the Adana Basin will be the future southeastern boundary of the Anatolian Plate escape tectonic system.

How to cite: Delph, J., Darin, M., Whitney, D., Cosca, M., Teyssier, C., Eken, T., Kaymakci, N., Reid, M., and Beck, S.: Deep lithospheric controls on the formation and evolution of the East Anatolian Fault Zone and Anatolia-Arabia-Africa Triple Junction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12869, https://doi.org/10.5194/egusphere-egu24-12869, 2024.

EGU24-14322 | ECS | Posters on site | GD4.1

The metamorphic dehydration of subducted metabasalts in the Catalina Schist: Does epidote record fluid production at the depths of deep slow slip and tremor? 

Peter Lindquist, Cailey Condit, William Hoover, and Victor Guevara

Dehydration reactions in the subducting slab have been suggested as a fluid source for high pore fluid pressures that are inferred in the environment that hosts deep slow slip and tremor in subduction zones. Using petrography, major and trace element geochemistry, and petrologic modeling, we study the record of dehydration reactions in exhumed metabasalt from the Catalina Schist in southern California, USA to explore potential sources of the fluids that produce high pore fluid pressures at the plate interface. The Catalina Schist comprises tectonic slices that were underplated in a subduction zone at lawsonite blueschist to amphibolite facies conditions. Metabasalts from the epidote-amphibolite facies unit here represent a coherent section of oceanic crust that was underplated during subduction at ~550°C and ~1 GPa, and are  ~100 m structurally below an ultramafic-metasedimentary mélange unit interpreted to be a paleosubduction interface from ~35 km paleodepth. Previous thermodynamic modelling suggests that epidote minerals may be common reaction products during prograde dehydration reactions along typical warm subduction geotherms, particularly at the conditions of slow slip and tremor. We therefore focus on epidote textures and trace-element compositions to provide insights into the metamorphic reactions experienced by these metabasalts, and by extension reconstruct the dehydration history of this subducted slab. Pairing these analyses with phase equilibrium modeling, we estimate the P-T path experienced by these metabasalts and the conditions at which epidote may be growing or reacting out. Epidote textures vary significantly across outcrops and appear in various settings including: epidote-rich veins and vein-like dehydration networks, and porphyroblastic epidote in surrounding host rocks. Oscillatory zoning in synkinematic epidote porphyroblasts further suggests episodic growth under varying conditions or fluid compositions. Variations in the major element and trace element geochemistry of epidote across these domains, coupled with petrologic modeling helps to reveal the metamorphic reactions that occurred in these rocks, and allows us to begin quantifying the volumes of fluids that may be released during prograde metamorphism near the conditions of deep slow slip and tremor.

How to cite: Lindquist, P., Condit, C., Hoover, W., and Guevara, V.: The metamorphic dehydration of subducted metabasalts in the Catalina Schist: Does epidote record fluid production at the depths of deep slow slip and tremor?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14322, https://doi.org/10.5194/egusphere-egu24-14322, 2024.

Elastic/viscoelastic dislocation theory is a fundamental tool in computing crustal deformation due to fault motion, not only for instantaneous coseismic deformation but also for gradual postseismic and interseismic deformation. Expressing the kinematic interaction between the subducting and overriding plates by dislocation along the plate interface, our group has developed a crustal deformation model due to plate subduction, named "dislocation model for plate subduction" (Matsu'ura & Sato 1989, GJI), which is a generalization of Savage's back slip model (Savage, 1983, JGR), including the effect of deformation due to steady plate subduction. Hashimoto et al. (2004, PAGEOPH) demonstrated that the pattern of uplift rates in and around Japan computed by this model shows excellent coincidence to the observed free-air gravity anomalies. Fukahata and Matsu‘ura (2016, GJI), using the 2D model, explained the physical mechanism of island-arc uplift, trench subsidence, and outer rise uplift by combining the effects of lithospheric rotation and gravity.

   In this study, we develop a 3D numerical model and compute vertical displacement rates in a subduction zone caused by steady slip along a plate interface, in which the trench axis has a bend convex toward the island arc. Computation results show that the island arc lithosphere significantly subsides around the bend, and that the subsidence is larger for a larger bend angle.

   This subsidence can be physically understood by mass deficit in the island arc lithosphere, as explained below. When a plate subducts along a trench with a bend convex toward the island arc, mass excess inevitably occurs in the subducting slab, which can be understood from an analogy of a tablecloth draped at a corner of a table. In the dislocation model, the motion of plate subduction is expressed by displacement discontinuity along the plate interface. The displacement discontinuity, which is equivalent to a force system of a double couple, requires two surfaces that sandwich a fault to move in exactly opposite directions each other, which results in mass deficit in the island arc, because mass excess occurs in the subducting slab.

   Along the main Japanese islands, we observe significant invasions of negative free-air gravity anomalies into the forearc around the Hidaka Trough, the Kanto Plain, and the Bungo Channel, which correspond to the junctions of the trench axes. In brief, these forearc negative free-air gravity anomalies can commonly be understood by the above mechanism. We also observe similar invasions of negative free-air gravity anomalies around the Arica bend, South America, and Cascadia, though the signals of negative gravity anomalies are smaller in these regions, reflecting gentler changes of the strikes of the trench axes.

How to cite: Fukahata, Y. and Mori, Y.: 3-D Numerical Simulation of Island Arc Deformation based on the Dislocation Model for Plate Subduction and its Insight into Topographic Evolution of Island Arcs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14479, https://doi.org/10.5194/egusphere-egu24-14479, 2024.

EGU24-14482 | ECS | Posters on site | GD4.1

An alternative mode of slab deformation in the mantle transition zone: segmentation and stacking 

Keqing Li, Jiashun Hu, Yida Li, Hao Zhou, and HaiJiang Zhang

The contradiction of high subducting plate speed (ranging from 4-9 cm/yr on Earth’s surface) and slow slab sinking rate (about 1-2 cm/yr in lower mantle) is intimately related to the subduction dichotomy of strong plates and weak slabs. The significant difference in the two rates indicates significant slab deformation in the mantle transition zone. However, the way and mechanism by which this deformation occurs have not been fully understood. Slab buckling has been frequently invoked to explain the deformation, but it is insufficient to accommodate the large difference in slab sinking rates across the mantle transition zone, even if an extremely low yield stress  100 MPa is applied.

Using 2-D numerical models that incorporate composite viscosity and grain size evolution, we propose a new mode of slab evolution, slab segmentation and stacking, to accommodate the differential slab sinking rates between the upper and lower mantle. The segmentation of slab is facilitated by the serpentinization of the normal faults at the outer rise and the grain size evolution, confirming the results of earlier studies (Gerya et al., 2020). More interestingly, we find periodic tearing and stacking of slab when it encounters the high viscosity lower mantle. Stacked slabs slowly sink in the lower mantle, while periodic slab tearing hinders stress transimission upward, allowing shallow plates to subduct at a higher rate. This model not only explains the high plate subduction rate observed at present day, but also the thickening of slab in the lower mantle. In addition, it provides a mechanism for slab to tear in the mantle transition zone, and thus may explain the enigmatic slab geometry beneath the Izu-Bonin-Mariana subduction zone.

How to cite: Li, K., Hu, J., Li, Y., Zhou, H., and Zhang, H.: An alternative mode of slab deformation in the mantle transition zone: segmentation and stacking, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14482, https://doi.org/10.5194/egusphere-egu24-14482, 2024.

EGU24-14498 | ECS | Posters on site | GD4.1

Numerical modelling of dynamic fluid-rock reactions in subduction settings 

Kevin Wong, Alberto Vitale Brovarone, Simon Matthews, Guillaume Siron, Valeria Turino, Adam Holt, and Andrew Merdith

At subduction zones, geophysical and petrological observations suggest that forearc mantle wedges may be serpentinised by fluids released from the devolatilization of subducting slabs [1]. This pervasive serpentinisation of the wedge may be a substantial source of abiotic hydrogen (H2) and methane (CH4): gases with the potential to feed extremophile microorganisms in the deepest parts of the continental lithosphere that overlie the wedge. Characterisation of mantle wedge serpentinisation is therefore paramount to constraining the limits within which this deep biosphere can exist. However, the geochemical and geodynamical controls on wedge serpentinisation remain a subject of immense uncertainty. The magnitude of H2 and CH4 concentrations and fluxes generated from wedge serpentinisation are therefore poorly constrained at present.

Owing to the inaccessibility of the mantle wedge, constraints on H2 and CH4 generation within the mantle wedge must be predicted through geochemical models. In this contribution we present the preliminary results of an ongoing modelling study into mantle wedge serpentinisation. Our approach utilises the Deep Earth Water model [2] to calculate fluid-rock reactions at relayed pressure-temperature conditions in the wedge, which are dictated by geodynamical models of subduction zone thermal structure [3]. The resultant fluids of prior reactions are used as reactant fluids for subsequent reactions at new pressures and temperatures; a chain of individual reactions therefore simulates the whole-scale serpentinisation of a column of mantle rock by slab fluid as the fluid migrates upwards through the wedge. By recording the composition of the overall mantle column at each pressure-temperature step, the introduction of new fluid to the resultant column provides a time element, which we use to track the evolution of bulk mantle mineralogy as subduction progresses.

Our preliminary results suggest that a heavily serpentinised layer forms rapidly at the slab-wedge interface, thereby strongly shielding the overlying mantle from significant alteration. Over more time steps, while bulk mantle density continues to decrease with time and increasing serpentinisation, our model suggests that new fluid does not significantly alter the mineralogical composition of the bulk mantle as observed within the first few time steps, and H2 and CH4 concentrations remain invariant throughout the column. However, the rate at which this fluid equilibration is achieved is strongly dependent on the initial conditions applied to the model. Our approach therefore provides a means to test multiple different parameters on H2 and CH4 generation at subduction zones, with scope for investigating the impact of variable fluid-rock ratio, initial mantle wedge and slab fluid compositions, and mantle wedge thermal structure.

[1] Vitale Brovarone et al., 2020. Nature Comms. 11(1), 3880.
[2] Sverjensky et al., 2014. Geochim. Cosmochim. Acta 129, 125-145.
[3] Holt and Condit, 2021. Geochem. Geophys. Geosyst. 22(6), e2020GC009476.

How to cite: Wong, K., Vitale Brovarone, A., Matthews, S., Siron, G., Turino, V., Holt, A., and Merdith, A.: Numerical modelling of dynamic fluid-rock reactions in subduction settings, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14498, https://doi.org/10.5194/egusphere-egu24-14498, 2024.

EGU24-14820 | Orals | GD4.1

Subduction dynamics and overriding plate deformation 

Wouter P. Schellart

Many subduction zones on Earth experience active overriding plate deformation. Most experience extension, resulting in the formation of a backarc basin (e.g. East Scotia Sea, North Fiji Basin, Aegean Sea), while some experience shortening, resulting in a massive cordilleran mountain range (e.g. Andes). It is unclear why some overriding plates experience shortening and others extension, and why extension occurs more frequently than shortening. Numerical geodynamic simulations of subduction are presented investigating the control of slab width and subduction depth on overriding plate deformation. The numerical models demonstrate that shortening only occurs at very wide subduction zones that have subducted into the lower mantle, while overriding plate extension occurs more frequently, taking place both for narrow and intermediate size subduction zones throughout their evolution, and for wide subduction zones in the early (upper mantle) stage of their evolution as well as near their lateral slab edges during the middle stage of their evolution. The model results are compared with a global dataset of all active subduction zones on Earth (about 51,600 km of subduction zones), providing an explanation for the present-day deformation style at these subduction zones. In particular, the comparison between models and the global dataset provides an explanation for the more frequent occurrence of extension in the overriding plate compared to shortening.

How to cite: Schellart, W. P.: Subduction dynamics and overriding plate deformation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14820, https://doi.org/10.5194/egusphere-egu24-14820, 2024.

EGU24-15803 | ECS | Posters on site | GD4.1

Slab window geodynamics: towards an integrated understanding of upper mantle dynamics and observations 

Jorge Sanhueza, Attila Balázs, Taras Gerya, Gonzalo Yáñez, and W. Roger Buck

The generation of a slab window impacts the spatio-temporal evolution of subduction zones and promote complex mantle flow pattern where slabs once descended. The origin of slab windows is attributed to processes such as mid-ocean ridge subduction, slab tearing and/or break-off. The interaction between mid-ocean ridges and trenches is a common process affecting the geodynamic history of the margins around the Pacific, at least, during the Cenozoic and generated several modern slab windows. These intriguing features have notable effects on the upper mantle where temperature anomalies develop due to the asthenospheric upwelling and complex toroidal flow patterns through and around slab windows. There are profound effects on the overriding plate for the surface heat flow, geochemistry and spatial distribution of magmatic activity, seismicity and topographic relief. However, these manifestations evolve through space and time depending on the ridge axis-trench geometry, inducing the continuous slab window opening during its subduction.

In this contribution, we derived a simplified expression for the slab window angle and then conducted 3D geodynamic modeling to link slab windows dynamics with geochemical and geophysical observables. The numerical models were conducted with fixed geometries in steady-state (using finite elements), compared with time-dependent solutions (using the I3ELVIS code) and then compared with observations from modern slab windows along the eastern Pacific. The analytical solution for the plan projection of the slab window depends on three parameters: the ratio between the half-spreading rate to the velocity of the overriding plate, the subduction angle and the obliquity of the ridge axis respect to the trench.

Fast spreading or slow plate convergence promotes a wide (> 90°) slab window while slow spreading or fast convergence narrows this gap (< 90°). The slab dip and ridge obliquity have a second order control on the plan projection of the slab window but affect the existence of a steady-state solution. The implementation of this geometry into 3D steady-state models was used to generate a novel methodology to estimate mantle/melt upwelling and temperature anomalies in the upper mantle for a wide range of tectonic settings. Preliminary results on 3D time-dependent models reproduce a self-consistent opening of the slab window by only imposing spreading at the mid-ocean ridge and a subduction velocity with respect to the overriding plate. The ratio and absolute magnitude of these velocities controls the timing of the opening as well as the lateral and depth extent of the subducting plates. This timing also influences the development of upwelling and toroidal flow patterns around the slab edges. Finally, observations in modern slab windows along the eastern Pacific are consistent with the temperature and velocity field of the models. Variations in temperatures in the upper mantle are consistent with mantle shear wave speeds anomalies, while the flow field is correlated with the azimuthal anisotropy. In terms of magmatism, variables degrees of melting are consistent with the generation of tholeiitic to alkaline magmas in backarc areas.

How to cite: Sanhueza, J., Balázs, A., Gerya, T., Yáñez, G., and Buck, W. R.: Slab window geodynamics: towards an integrated understanding of upper mantle dynamics and observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15803, https://doi.org/10.5194/egusphere-egu24-15803, 2024.

EGU24-15924 | Posters on site | GD4.1

The Mussau Ridge and Trench – news from an infant subduction zone 

Philipp Brandl, Christoph Beier, Leon Waßmund, Jacob Geersen, and Felix Genske

The Mussau Trench between Papua New Guinea and the Federated States of Micronesia is considered as the type locality for induced subduction initiation through transference. Despite its significant role for studying and understanding global plate tectonic cycles, little is known about its tectonic  geomorphology, lithostratigraphy, and geodynamic evolution. During research expedition SO299 DYNAMET with the German RV SONNE, the morphology and shallow structure of the Mussau Ridge was mapped along its entire length and sampled at representative locations. At the central segment, the ridge was visually mapped and stratigraphically sampled using the ROV. Here we present the first results from petrology, geochemistry and structural mapping of the ridge. Preliminary glass major and trace element data indicate a depleted MORB-like nature of the exposed crust that is in agreement with previous findings. Stratigraphically, lavas (layer 2A) and sheeted dykes (layer 2B) of the oceanic igneous crust are exposed. Whole rock trace element and radiogenic isotopes analyses are currently underway to further constrain the geochemical character of the crust and its associated mantle sources. Initial results from hydroacoustic and visual mapping indicate the presence of an active thrust system based on pristine fault scarps and large rubble piles lacking any sediment cover. However, shape and structure of the ridge vary along strike, and only the central portion holds indications for tectonic uplift. In the south and in the north, the ridge shows evidence for a strong lateral shear component. We combine the obtained results into an initial model of the tectonic evolution of the ridge and how this fits into regional plate tectonic models.

How to cite: Brandl, P., Beier, C., Waßmund, L., Geersen, J., and Genske, F.: The Mussau Ridge and Trench – news from an infant subduction zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15924, https://doi.org/10.5194/egusphere-egu24-15924, 2024.

EGU24-16152 | Posters on site | GD4.1

Balance of solid and fluid transfers near the updip limit of the seismogenic zone at the scale of all subduction zones in a revised kinematic framework 

Serge Lallemand, Michel Peyret, Diane Arcay, Nestor Cerpa, and Arnauld Heuret

The nature and amount of sediments transferred from one plate to the other near the subduction interface partly determine the tectonic and seismogenic regime of a margin. Examination of over 500 multichannel seismic lines has enabled us to build a global database of subduction zone front characteristics at unprecedented spatial resolution. The total thickness of sediments in the trench below the deformation front, as well as that of the subduction channel at a distance from the trench, combined with other indices, such as the tectonic regime of the forearc or the migration of the volcanic front, are used to revisit the accretionary or erosional character of active margins.

The integration of our observations over the last million years has been achieved in parallel with a revision of the kinematics of subduction zones, taking into account deformation at the front of the thrust plate. Indeed, subduction zones are often the site of distributed or localized deformation up  to several hundred kilometers away from the plate boundary. Taking the "arc sliver zone » deformation into account yields a more accurate estimate of the effective long-term slip velocities (modulus, azimuth) on the subduction interface, which is fundamental to properly estimate material flow transiting towards the mantle.

Preliminary conclusions, based on ∼3/4 of sufficiently documented subduction zones, show a predominance of the erosive character of subduction over the last million years. The flux of solid sedimentary matter through the shallow part of the subduction channel is approximately 1.5 km3/yr, and that of pore fluids 0.4 km3/yr. Some subduction zones, such as the Aegean-Cyprean one, are characterized by exceptional solid flux in the channel, whereas the fluid flux is comparatively moderate. This is because channel sediments are compacted even before being subducted. Indeed, porosity has a major influence in estimating these fluxes, maximum porosity in the channel being reached when there is neither accretion nor tectonic erosion. Overall, fluid flux in the channel is greater under erosive margins, due both to the higher rate of subduction and often higher porosity. The data are displayed over 260 transects across subduction zones thanks to the Submap web-tool (www.submap.fr).

How to cite: Lallemand, S., Peyret, M., Arcay, D., Cerpa, N., and Heuret, A.: Balance of solid and fluid transfers near the updip limit of the seismogenic zone at the scale of all subduction zones in a revised kinematic framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16152, https://doi.org/10.5194/egusphere-egu24-16152, 2024.

EGU24-16410 | ECS | Orals | GD4.1 | Highlight

H2 formation in subduction zone 

Alexis Gauthier, Tiphaine Larvet, Laetitia Le Pourhiet, and Isabellle Moretti

Dihydrogen (H2) is a promising decarbonized energy source, but traditional artificial production methods emit CO2 and/or consume a lot of energy. However, there are natural sources of H2 on Earth originating from diverse geochemical processes. A recent study above the Nazca plate subduction in the Andes, detected variations in the H2 emanation function on the slab dip angle. This H2 release is likely the result of peridotite hydration in the mantle wedge, notably through serpentinization. The water required for peridotite hydration is sourced from dehydration of the subducting plate as it sinks into the Earth's mantle.

This study aims to understand the influence of slab dip angle on H2 production in the mantle wedge using the pTatin2D code. Fluid circulation were implemented based on two principles:

  • The hydration and dehydration capacity of rocks under varying pressure and temperature conditions is predicted using tables from the thermodynamic software PerpleX.
  • The velocity of free water is equivalent to that of surrounding rocks, with a vertical component related to percolation.

Numerical simulations show that in the case of flat subduction, the mantle hydration zone, where H2 is produced, is wide and extending up to 500 km from the trench. On the other hand, in the case of a steep subduction, the zone is narrower, and is located between the trench and the volcanic arc. Magma formation competes with H2 generation for the use of water released from the subducting plate. During the transition from steep to flat subduction, the mantle hydration zone undergoes widening while the volcanic zone migrates significantly away from the trench. This transition may also trigger oceanic crust melting, resulting in a shift in magma composition before the volcanism intensity diminishes and then disappears.

How to cite: Gauthier, A., Larvet, T., Le Pourhiet, L., and Moretti, I.: H2 formation in subduction zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16410, https://doi.org/10.5194/egusphere-egu24-16410, 2024.

EGU24-17659 | ECS | Posters on site | GD4.1

Dynamics of Plateau Growth: Geodynamic Modeling of the East AnatolianPlateau Uplift Through Double Subduction Processes 

Uğurcan Çetiner, Jeroen van Hunen, Andrew P. Valentine, Oğuz H. Göğüş, and Mark B. Allen

The Turkish–Iranian Plateau was formed by the collision between the Arabian and
Eurasian plates, commencing along the Bitlis-Zagros suture in the Late Eocene (~30-
35 Ma). This region, commonly partitioned into the East Anatolian Plateau and the
Iranian Plateau, is associated with significant differences in terms of lithospheric
structure despite an overall average of ~2 km. The geodynamic evolution of East
Anatolia is represented by a double subduction system, where the two branches of
Neo-Tethys were subducting beneath Eurasia, constantly accumulating accretionary
material that forms the bulk of the plateau today (i.e., East Anatolian Accretionary
Complex). Seismic evidence demonstrates that the region has unusually thin MOHO
(~35 km around Lake Van region) while the whole area is formed mostly by oceanic
(accretionary) material and is underlain by no or very thin mantle lithosphere. The
uplift of East Anatolia is attributed to slab break-off and slab peelback (delamination),
combined with crustal shortening. However, the intricate plate dynamics arising from
such a double subduction system, controlling plateau formation remains unclear.
Here, we conducted 2D numerical experiments and comparative model sets indicate
that, in a double subduction system like Eastern Anatolia, the mechanisms of slab
break-off and peelback heavily depend on the rheology of the subducting plates and
the coupling between the overlying and subducting plate along the trenches. In cases
of strong coupling between subducting and overlying plates, we observed an
amalgamation of the two subducting plates as they converge, potentially resulting in
a break-off as a single blob, depending on plate rheology. Conversely, in models with
weaker coupling along the trenches, peelback along the northern slab creates a thin
lithosphere along the accretionary prism, such as in the evolution of the Eastern
Anatolian Plateau. Our results highlight the important interaction between the
subduction systems where rheological constraints of the lithosphere, among other
model parameters, exert a first-order control for plateau formation.

How to cite: Çetiner, U., van Hunen, J., Valentine, A. P., Göğüş, O. H., and Allen, M. B.: Dynamics of Plateau Growth: Geodynamic Modeling of the East AnatolianPlateau Uplift Through Double Subduction Processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17659, https://doi.org/10.5194/egusphere-egu24-17659, 2024.

EGU24-17823 | Posters on site | GD4.1

Influence of the fluid pressure ratio on accretionary wedge evolution over long timescales 

Derek Neuharth, Whitney Behr, Adam Holt, and Jonas Ruh

Accretionary wedges are regions of off-scraped and underplated sediment and oceanic crustal materials formed along subduction zones. Many modeling studies investigate accretionary wedge mechanics on a crustal scale, or on a larger scale using kinematic boundary conditions. However, in fully dynamic systems subduction velocity can change through time in response to variations in large-scale subduction dynamics (e.g., as the slab travels rapidly through the upper mantle vs. slower sinking through the transition zone). How this time-dependence affects an evolving accretionary wedge and subduction interface properties, and the resulting effect on subduction speeds, is not well understood.

To understand how accretionary wedges evolve during different stages of subduction, we develop fully dynamic 2D subduction models using the finite element code ASPECT. The visco-plastic model setup consists of a dense subducting plate and a buoyant overriding plate coupled with a 6-km thick wet quartzite sediment interface. A fluid pressure ratio profile is prescribed within the sediment that varies from 0.4 at the surface to 0.9 at depths greater than 4-km. Between 50 to 100 km depth, the fluid pressure ratio is linearly tapered from 0.9 to 0. We run models for 30 Myr where we vary 1) the initial sediment thickness, 2) frictional strength, and 3) the depth needed to reach the maximum fluid pressure ratio. We explore how these parameters affect the thickness of the accretionary wedge, the amount of sediment that enters the subduction channel, and the resulting subduction speed.

Preliminary results suggest that an accretionary wedge will initially frontally accrete as the wedge thickens. Over time, the faults forming these slivers are rotated towards vertical and moved towards the subduction zone along a basal decollement. Eventually, a second decollement forms along the overriding plate interface and links to the first decollement through backthrust faulting, creating a series of accretionary wedge blocks that are underthrust into the subduction interface. Increasing the depth to the maximum fluid pressure ratio leads to a larger accretionary wedge, and a deeper basal decollement. A deeper decollement results in greater sediment underplating due to the backthrust faulting, resulting in more sediment within the subduction interface.

How to cite: Neuharth, D., Behr, W., Holt, A., and Ruh, J.: Influence of the fluid pressure ratio on accretionary wedge evolution over long timescales, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17823, https://doi.org/10.5194/egusphere-egu24-17823, 2024.

EGU24-18222 | ECS | Posters on site | GD4.1

Variability of lower continental crust constrained by drill core data of the Ivrea Zone (DIVE project DT-1B, Ornavasso, Val d’Ossola, Italy) 

Alexia Secrétan, Sarah Degen, Luca Pacchiega, Jörg Hermann, and Othmar Müntener

The estimates of the chemical composition of the lower continental crust ranges from predominantly mafic to felsic. The Ivrea Zone in the Southern European Alps provides insight into this variability, featuring a pre-Permian mostly felsic lower crust modulated by additions of mafic rocks during Permian underplating. The Ivrea zone is an ideal location to examine major, trace, and volatile elements over the full range of proposed lower crustal compositions. Our study presents whole-rock data derived from a drill core of the first hole (DT-1B) of the ICDP-funded project DIVE (Drilling the Ivrea-Verbano Zone). The drilled section spans nearly 600 m, representing an upper part of the Ivrea lower continental crust. Logging of the drill core showed that biotite-gneisses (Qtz + Pl + Bt ± Gt ± Kfs ± Sil – 75 vol%) and metamafic rocks (Amp + Pl + Qtz ± Px ± Bt ± Gt – 21 vol%) are the main rock types with minor calcsilicate rocks (Cc + Gt + Px + Ttn + Qtz + Pl ± Amp – 2 vol%), and some minor pegmatites (2 vol%). Both targeted and grid sampling strategies aimed to minimize sampling bias, providing a reliable basis for understanding the Ivrea lower continental crustal composition and extrapolating the results toward a realistic assessments of the LCC composition in general.

Amphibolite facies metasediments (34 samples) range from calc-silicates to pelites and psammites, exhibiting a wide range of major element compositions (32 - 89 wt.% SiO2; 0.5 - 5.8 wt.% K2O; 0.35 - 0.54 Mg#). Metamafic rocks (16 samples) cover a more restricted compositional range (43 - 57 wt.% SiO2; 0.1 - 5 wt.% K2O; 0.3 - 3 wt.%; 0.36 - 0.61 Mg#). Most mafic rocks are LREE enriched, but a few resemble MORB-like compositions. A preliminary comparison of the bulk rock estimate of the entire drill core relative to the integrated composition derived from geological maps indicates that deviations between the two approaches are considerable, ranging from <10% up to 30% difference for major elements (calculated bulk vs compiled data from the literature: 62.8 vs 57.6 wt.% SiO2; 2.3 vs 1.95 wt.% K2O; 0.47 vs 0.50 Mg#). Results also indicate that fluid-mobile elements are mostly conservative with respect to potential protoliths. The chemical variability points to a possible origin of sediments derived from an accretionary wedge. The evaluation of bulk trace element ratios (i.e., Th/La, Sm/La, Nb/K2O) suggests that the drilled sequence likely originated from (Paleozoic?) turbidites. Subduction of sediments and accretion to the lower continental crust are the most likely processes to explain the predominance of metasediments in this part of the Ivrea lower continental crust.

How to cite: Secrétan, A., Degen, S., Pacchiega, L., Hermann, J., and Müntener, O.: Variability of lower continental crust constrained by drill core data of the Ivrea Zone (DIVE project DT-1B, Ornavasso, Val d’Ossola, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18222, https://doi.org/10.5194/egusphere-egu24-18222, 2024.

EGU24-18579 | ECS | Posters on site | GD4.1

Complex subduction and mantle dynamics induced by along-strike variations in overriding plate structure 

Pedro José Gea Jódar, Ana M. Negredo, Flor de Lis Mancilla, Jeroen van Hunen, and Magali Billen

Subduction zones are intrinsically three-dimensional and present a huge variability in observables along the trench, such as deformation style of the overriding plate, trench velocity, slab depth and mantle flow patterns. Geodynamic models commonly rely on factors such as external mantle flow and/or along-strike variations in the properties of subducting slabs to account for these variations in the trench-parallel direction, often ignoring the role of the overriding plate, which has been proven to strongly affect subduction dynamics. In this work, we investigate through self-consistent 3D subduction models how along-strike variations in the overriding plate structure can induce along-strike variations in subduction dynamics and mantle flow. Our results show that variations of the overriding plate thickness along the trench-parallel direction result in large along-strike variations of the trench retreat velocities, leading to highly arcuated trenches. This difference in trench retreat velocities along the trench induce complex mantle flow patterns, with the toroidal flow cells that surround the slab converging below the thin part of the overriding plate. Due to this complex mantle flow, regions of maximum localised extension are found within the thin portion of the overriding plate. Overall, our results contribute to a better understanding of seismic anisotropy observations at subduction zones on Earth.

How to cite: Gea Jódar, P. J., Negredo, A. M., Mancilla, F. D. L., van Hunen, J., and Billen, M.: Complex subduction and mantle dynamics induced by along-strike variations in overriding plate structure, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18579, https://doi.org/10.5194/egusphere-egu24-18579, 2024.

EGU24-19448 | ECS | Posters on site | GD4.1

Bending-related faulting, hydration, and mantle serpentinization in the incoming Cocos Plate at Middle America Trench: Evidence from wide-angle seismic refraction data 

Yuhan Li, Ingo Grevemeyer, Adam Robinson, Timothy J. Henstock, Milena Marjanović, Anke Dannowski, Helene-Sophie Hilbert, and Damon A.H. Teagle

At subduction zones, the bending of incoming plates and associated extensional stresses resulted in strong fault activity in the crust and upper mantle. The severe fracturing of the subducting slab in the trench outer rise facilitates the entrain of seawater into the lithosphere, leading to the serpentinization of peridotite in the upper mantle. Therefore, subduction zones are an important setting, nurturing material exchange between the hydrosphere and the solid earth, affecting the water cycle.

To investigate the behavior of the subducting plate, during the experiment conducted aboard RRS JAMES COOK in the Guatemala Basin where the Cocos plate enters the Middle America Trench, we collected a wide-angle seismic refraction profile and coincident multi-channel seismic profile. Here, we present a seismic velocity model derived from a joint refraction and reflection seismic tomography using 10,508 crustal refraction arrivals, 6,533 Moho reflection arrivals, and 7,769 upper mantle refraction arrivals recorded by 37 ocean-bottom-seismometers. The spacing of instruments is ~7.5 km on the unaltered incoming plate and decreases to half of that from the outer rise into the trench. The results show that the unaltered oceanic crust is ~5-6 km thick and features a typical two-layer oceanic structure, ranging from ~4-5 km/s at the basement top to ~7 km/s at the bottom of the crust. Closer to the trench, at ~70 km away, we observe a prominent velocity reduction with lower-crustal velocities dropping to <6.8 km/s, indicating a strong impact of bend-faulting and/or hydration of the crust. However, the onset of normal faulting is observed in the coincident seismic reflection profile at ~100 km away from the trench axis. The observed faulting may indicate an evolutionary process with the progressive development of bending-related faults. At the outer rise, a seamount rising ~1 km above the seafloor is characterized by extremely low crustal velocities of only <6.5 km/s at the bottom of the crust, suggesting that the seamounts facilitate hydration. Further east, the lower crustal velocities are reduced to ~6.5-6.7 km/s beneath the outer trench wall. In the upper mantle, velocity reduction is observed ~100 km away from the trench axis and reaches its minimum beneath the seamount at the outer rise with ~7.2 km/s, which may indicate up to ~20% of mantle serpentinization. Based on our velocity modeling results, we conclude that the intensity of bend-related faulting, hydration, and mantle serpentinization is not only controlled by the distance from the trench axis but also by seamounts ventilating the oceanic crust.

How to cite: Li, Y., Grevemeyer, I., Robinson, A., Henstock, T. J., Marjanović, M., Dannowski, A., Hilbert, H.-S., and Teagle, D. A. H.: Bending-related faulting, hydration, and mantle serpentinization in the incoming Cocos Plate at Middle America Trench: Evidence from wide-angle seismic refraction data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19448, https://doi.org/10.5194/egusphere-egu24-19448, 2024.

EGU24-19465 | Posters on site | GD4.1

Parametric study for self-sustained Andean-type subduction speed 

Jamison Assunção, Nicolas Riel, Andrea Piccolo, and Victor Sacek

The relation between subduction dynamics, plate rheology and geometry is still not well understood. To numerically assess how subduction convergence velocity develops, a wide range of simulations is required to quantify any correlation between physical parameters and kinematic behavior of a subduction system. In this study, we performed a set of 2D numerical simulations designed to better constrain the range of rheological and geometrical conditions necessary to model subduction dynamics. We used the parallel numerical code LaMEM to simulate thermo-mechanical convection. In addition, we coupled these numerical simulations with MAGEMin to compute a self-consistent mineral assemblage of the asthenospheric mantle and the plates, and we parameterized the lower mantle using a linear equation, following the Clapeyron slope from Faccenda and Zilio (2017). The modeled region is 9300 km wide and accounts for both the upper and whole lower mantle. We consider an Andean type subduction system where our baseline scenarios are defined by a partially subducting oceanic plate beneath a continental plate. Once the simulation starts, the subducted portion of the oceanic plate triggers the subduction thanks to a weak zone between the lower and upper plate. The subduction is sustained by the negative buoyancy of the lower plate with respect to the surrounding mantle. We aim to simulate subduction dynamics that exhibit convergence velocities and long term behavior, including lower mantle penetration, similar to what is observed in nature. We investigate the role of the length of the subducting plate, the geometry of its composing lithological units, and the viscosity of the asthenosphere and the lower mantle. We find that the subduction velocity is inversely correlated with the non subduction length of the oceanic plate, and that a less viscous asthenospheric mantle increases the subduction speed. 

How to cite: Assunção, J., Riel, N., Piccolo, A., and Sacek, V.: Parametric study for self-sustained Andean-type subduction speed, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19465, https://doi.org/10.5194/egusphere-egu24-19465, 2024.

EGU24-19667 | ECS | Posters on site | GD4.1

Dynamical evolution of forearc subsidence controlled by slab geometry 

Francisco Bolrão and Wouter Schellart

The forearc is the region of the overriding plate (OP) that physically interacts with the subducting plate (SP) and is expected to record critical information about subduction dynamics. A way to access such information is through its topography, which presents a wide variability across the natural prototypes. Some forearcs show a peculiar topography characterised by a forearc high next to the trench and a forearc basin in between this high and the magmatic arc (e.g. Alaska, Java, Central Chile). Previous studies have proposed that such topographic signature is a consequence of the gradient of the vertical component of the suction force along the plate interface (e.g., Hassani et al. 1997, Chen et al. 2017). 
Our study focuses on the role of several subduction parameters in shaping the topography of the forearc, namely the OP and SP thicknesses, OP viscosity, and slab dip angle. To carry out this investigation, we developed a series of buoyancy-driven and isoviscous models using analogue techniques, where we applied a stereoscopic particle image velocimetry technique to monitor the topography of the forearc.
So far, we have analysed the impact of the OP thickness, which shows a negative correlation with the magnitude of the forearc basin. Thicker OPs constrain trench retreat, which forces the SP to move trenchward,with subduction occurring mostly through down-dip slab sinking. Consequently, the suction force created at the plate interface by hinge retreat will decrease, resulting in shallower forearc basins. Moreover, the wavelength of the forearc basin is also affect, with thicker OP producing wider basins. Such observation suggests that the previously proposed mechanism that shapes the forearc topography is correlated with the subduction partitioning so that the magnitude of the forearc basin increases as the subduction is increasingly accommodated by slab retreat.

How to cite: Bolrão, F. and Schellart, W.: Dynamical evolution of forearc subsidence controlled by slab geometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19667, https://doi.org/10.5194/egusphere-egu24-19667, 2024.

EGU24-20470 | Orals | GD4.1

Storage and fate of volatiles in the shallow mantle: Insights from fluid mobile elements and light element (B, Li) isotopes in serpentinites 

Ivan Savov, Samuele Agostini, CeesJan DeHoog, William Osborne, Andrew McCaig, Detlef Rost, Jeff Ryan, Roy Price, Dyonisis Foustoukos, Haiyang Liu, and International Ocean Discovery Program Expedition 399 Sci. Party

We will present whole rock and mineral chemistry insights into the systematics of light elements (B, Li) and their isotopes during the serpentinization processes at both divergent and convergent plate margins. For the divergent plate case we have selected Site 1309D and some from the recently drilled (IODP Expedition 399, Atlantis Massif, Mid-Atlantic Ridge 30N) Site 1601C as the deepest in situ gabbo-peridotite drill cores ever recovered from the ocean floor. The downcore variation in fluid mobile elements and the vast Sr and light element isotope fractionations highlight the important role of seawater infiltration and seawater-crust interactions taking place at depth. However, it appears that the role of seawater is gradually diminishing with depth, where rather unaltered lithologies may still be involved in active metamorphic (hydration) reactions. For the convergent plate margin serpentinization we have selected to present the fascinating case of the Mariana serpentinite mud “volcanism” in the W. Pacific. Several key cores were recovered during ODP Legs 125 and 195, as well as during the IODP Expedition 366. The rocks and fluids at these forearc sites also show very large downcore elemental and isotope fractionations. In contrast to the oceanic intraplate sites, these are associated with fluids produced by metamorphic dehydration reactions occurring at blueschist and amphibolite facies conditions as a consequence of subduction of old and cold Pacific slabs. We will attempt to contrast the different tectonic settings and speculate on the importance of variously hydrated ocean crust as a volumetrically important carrier of volatiles from the surface to the deep mantle and back. Serpentinites may be important to kick-start subduction initiation.

How to cite: Savov, I., Agostini, S., DeHoog, C., Osborne, W., McCaig, A., Rost, D., Ryan, J., Price, R., Foustoukos, D., Liu, H., and Ocean Discovery Program Expedition 399 Sci. Party, I.: Storage and fate of volatiles in the shallow mantle: Insights from fluid mobile elements and light element (B, Li) isotopes in serpentinites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20470, https://doi.org/10.5194/egusphere-egu24-20470, 2024.

EGU24-20684 | ECS | Posters on site | GD4.1

Subduction polarity reversal facilitated by plate coupling during arc-continent collision 

Zaili Tao and Jiyuan Yin

Subduction polarity reversal usually involves the break-off or tearing of downgoing plates (DPs) along the continent-ocean transition zone, in order to provide space for the overriding plate (OPs) to descend. Here we propose that subduction polarity reversal can also be caused by DP-OP coupling and that it can account for the early Paleozoic geological relationships in the West Kunlun Orogenic Belt (WKOB). Our synthesis of elemental and isotopic data reveals transient (~5 Myr) changes in the sources of the early Paleozoic arc magmatism in the southern Kunlun terrane. The early stage (530–487 Ma) magmatic rocks display relatively high εNd(t) (+0.3 to +8.7), εHf(t) (−3.6 to +16.0) values and intra-oceanic arc-like features. In contrast, the late-stage (485–430 Ma) magmatic rocks have predominantly negative εNd(t) (−4.5 to +0.3), εHf(t) (−8.8 to +0.9) values and higher incompatible trace elements (e.g., Th), similar to the sub-continental lithospheric mantle (SCLM) beneath the Tarim Craton. This abrupt temporal-spatial variation of arc magmatism, together with the detrital zircon evidence, indicate that subduction polarity reversal of the Proto-Tethys Ocean occurred in a period of ~10 Ma, consistent with migration of the magmatic arc. This rapid polarity reversal corresponds with the absence of ultra-high-pressure metamorphic [(U)HP] and post-collisional magmatic rocks, features normally characteristic of the slab break-off or tearing. Numerical modeling show that this polarity reversal was caused by plate coupling during arc-continent collision without slab break-off and tearing. This prevented rebound of the positively buoyant relic rocks and asthenosphere upwelling. This model successfully explains the early Paleozoic orogenesis in the WKOB and may be applied elsewhere where post-collisional magmatic and (U)HP rocks are absent.

How to cite: Tao, Z. and Yin, J.: Subduction polarity reversal facilitated by plate coupling during arc-continent collision, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20684, https://doi.org/10.5194/egusphere-egu24-20684, 2024.

EGU24-21046 | ECS | Orals | GD4.1

On the iron isotope systematics of subducted oceanic gabbros 

Alex Churchus, Oliver Nebel, Yona Jacobsen, Xueying Wang, Massimo Raveggi, Marianne Richter, and Roland Maas

Oceanic gabbros represent a voluminous part of oceanic crust and are to a large degree cumulative mineral assemblage composed of olivine-pyroxene-feldspar and iron oxides. As such, oceanic gabbros represent a large Fe isotope reservoir in the global Fe cycle. During recycling into the mantle, oceanic gabbros undergo metamorphic reactions but are often considered a small contributor to the subduction component in arcs (e.g., slab-derived fluids) due to their relatively dry and refractory nature. Instead, fluids released from serpentinite as a result of slab devolatisation are considered to be the main source of deep mantle wedge fluids and considerably contribute to arc-lava chemistry and the redox state of metasomatised mantle wedge. However, serpentinite-derived fluids will, by default, pass through overlying gabbroic sequences when ascending to the mantle wedge with a potentially considerable contribution to the Fe isotope budget of the mantle wedge and arc lavas.

Here, we investigate the Fe isotopic signature of gabbroic rocks exposed on the seafloor along the Southwest Indian Ridge and collected during IODP scientific ocean drilling expedition leg 118 from the Atlantis Bank Gabbro Massif (IODP Site 735B). Site 735B is composed of intrusive lower crustal and upper mantle rock exhumed to the surface by detachment faulting. Iron was chemically leached, simulating passing fluids, with both leachate and residue analysed for their Fe isotope composition. Our samples display large variation in isotopic composition ranging from mantle to extreme values of δ57Fe = -0.07 to +0.68‰ (relative to IRMM-524a) for the leachate, and MORB-like δ57Fe = -0.1 to +0.21‰, for the residue, respectively. Our results imply that the leached isotopically heavier Fe from oceanic gabbros can be a significant contributor to the Fe isotope composition of the subduction component in arcs and counterbalance the light Fe isotopes derived from serpentinites. Considering the oxidation state of Fe in magnetite, this may further add to the oxidized nature of arc lavas. If such fluids remain in the mantle, they can potentially be a very heavy Fe isotope reservoir, which may explain some exotic signatures observed in ocean island lavas or transition zone diamond inclusions. Gabbroic residues deprived of any such leachate resembles Fe isotope signatures of the upper mantle and MORB and thus does not change the Fe isotope composition of the mantle significantly after subduction. 

How to cite: Churchus, A., Nebel, O., Jacobsen, Y., Wang, X., Raveggi, M., Richter, M., and Maas, R.: On the iron isotope systematics of subducted oceanic gabbros, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21046, https://doi.org/10.5194/egusphere-egu24-21046, 2024.

EGU24-2415 | ECS | Posters on site | GMPV4.9

Thermal conductivity of Fe-bearing bridgmanite and post-perovskite determined by machine learning 

Dong Wang, Xin Deng, and Zhongqing Wu

Bridgmanite (Brg) and post-perovskite (PPv), as the most abundant minerals at the lower mantle, could be the main minerals in the Large Low Shear Velocity Provinces (LLSVPs). However, their thermal conductivities, as well as the impact of Fe impurities, are highly controversial. Measuring the thermal conductivity of minerals at high P-T conditions remains challenging, and determining the thermal conductivity of minerals by first principles calculations leads to finite size effects due to computational limitations. To overcome computational limitations, we trained a machine learning potential for Fe-free and Fe-bearing Brg and PPv with data from first-principles calculations, then investigated their thermal conductivity at high P-T conditions based on the machine learning potential in the large cells with finite-size effects well considered. We found that the presence of 12.5 mol% Fe in the lowermost mantle decreases the thermal conductivities of Brg and PPv by 10% and 14%, respectively. Furthermore, the phase transition from Brg to PPv increases the thermal conductivity of pyrolite by 22%. Incorporating the distribution of minerals, temperature, and iron content obtained through the inversion based on mineral elasticity and seismic tomography models, we found the heat flux is significantly lower in the LLSVPs regions, which would have important implications for the geomagnetic field and the thermal evolution of the Earth.

How to cite: Wang, D., Deng, X., and Wu, Z.: Thermal conductivity of Fe-bearing bridgmanite and post-perovskite determined by machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2415, https://doi.org/10.5194/egusphere-egu24-2415, 2024.

EGU24-2430 | ECS | Posters on site | GMPV4.9

Superionic Iron Hydride originated Ultra-low Velocity Zones at Earth’s Core Mantle Boundary 

Yu Zhang, Wenzhong Wang, and Zhongqing Wu

The origins of ultra-low velocity zones (ULVZs) detected at Earth’s core-mantle boundary, potentially linked to large low shear velocity provinces (LLSVPs), have been a subject of ongoing debate. Recent experiments have demonstrated the formation of iron hydride through a water-iron reaction under lowermost-mantle conditions; however, the stability of this compound has been inadequately constrained. By integrating first-principles molecular dynamic simulations with a machine learning approach, we have determined the stability and elastic properties of iron hydride under core-mantle boundary conditions.

Our results reveal that iron hydride is a stable superionic phase, in which hydrogen diffuses akin to a liquid while iron vibrates at lattice sites. Significantly, this phase exhibits markedly slower velocities and a higher density compared to the ambient mantle under lowermost-mantle conditions. The accumulation of iron hydride, through either water-iron reaction or the solidification of core material, provides a plausible explanation for seismic observations of ULVZs, particularly those associated with subduction. This work underscores the substantial role of water in generating seismic heterogeneities at the core-mantle boundary.

How to cite: Zhang, Y., Wang, W., and Wu, Z.: Superionic Iron Hydride originated Ultra-low Velocity Zones at Earth’s Core Mantle Boundary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2430, https://doi.org/10.5194/egusphere-egu24-2430, 2024.

EGU24-4206 | ECS | Posters on site | GMPV4.9

Moon-forming impactor as a source ofEarth’s basal mantle anomalies 

Qian Yuan, Mingming Li, Steven J. Desch, Byeongkwan Ko, Hongping Deng, Edward J. Garnero, Travis S. J. Gabriel, Jacob A. Kegerreis, Yoshinori Miyazaki, Vincent Eke, and Paul D. Asimow

Seismic images of Earth’s interior have revealed two continent-sized anomalies with low seismic velocities, known as the large low-velocity provinces (LLVPs), in the lowermost mantle. The LLVPs are often interpreted as intrinsically dense heterogeneities that are compositionally distinct from the surrounding mantle. Here we show that LLVPs may represent buried relics of Theia mantle material (TMM) that was preserved in proto-Earth’s mantle after the Moon-forming giant impact. Our canonical giant-impact simulations show that a fraction of Theia’s mantle could have been delivered to proto-Earth’s solid lower mantle. We find that TMM is intrinsically 2.0–3.5% denser than proto-Earth’s mantle based on models of Theia’s mantle and the observed higher FeO content of the Moon. Our mantle convection models show that dense TMM blobs with a size of tens of kilometres after the impact can later sink and accumulate into LLVP-like thermochemical piles atop Earth’s core and survive to the present day. The LLVPs may, thus, be a natural consequence of the Moon-forming giant impact. Because giant impacts are common at the end stages of planet accretion, similar mantle heterogeneities caused by impacts may also exist in the interiors of other planetary bodies.

How to cite: Yuan, Q., Li, M., Desch, S. J., Ko, B., Deng, H., Garnero, E. J., Gabriel, T. S. J., Kegerreis, J. A., Miyazaki, Y., Eke, V., and Asimow, P. D.: Moon-forming impactor as a source ofEarth’s basal mantle anomalies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4206, https://doi.org/10.5194/egusphere-egu24-4206, 2024.

EGU24-5736 | Posters on site | GMPV4.9

The effect of Fe3+ on the grain growth kinetics of bridgmanite and implications for the lower mantle seismic velocity anomalies 

Hongzhan Fei, Fei Wang, Catherine McCammon, and Tomoo Katsura

Two large low shear velocity provinces (LLSVPs) near the core-mantle boundary beneath the Pacific Ocean and Africa were discovered about 40 years ago and are characterized by tomographic images as reductions of shear and compression wave velocities by up to 3-4% and 1%, respectively, over an area of several thousand kilometers and a height of more than a thousand kilometers. It was recently proposed that the Fe3+ enrichment in bridgmanite could reduce its shear wave velocity and thus account for the formation of LLSVPs (Wang et al., 2021). However, the viscosity of the Fe3+-enriched bridgmanite is unknown, while it is critical for the long-term stability of LLSVPs at the base of the lower mantle against mantle convection. Considering the operation of diffusion creep in the lower mantle, viscosity will be positively correlated with grain size. Therefore, we measured the grain growth rate of bridgmanite under lower mantle conditions as a function of Fe3+ content. The experimental results show a significant enhancement of grain growth by Fe3+ incorporation. Thus, a larger grain size of bridgmanite is expected in the Fe3+-enriched LLSVPs than in the Fe3+-poor surrounding mantle, leading to highly viscous LLSVPs. As a result, they are stabilized at the base of the lower mantle over geological time.

How to cite: Fei, H., Wang, F., McCammon, C., and Katsura, T.: The effect of Fe3+ on the grain growth kinetics of bridgmanite and implications for the lower mantle seismic velocity anomalies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5736, https://doi.org/10.5194/egusphere-egu24-5736, 2024.

Minor amount of water may alter the chemical properties of minerals. In this talk, we review the role of water as an oxidant and explore the chemistry between water and mineral at Earth’s deep lower mantle. We consider the addition of pyrite-type (Mg,Fe)O2, which is stable at depth of 1800 through the reaction between water and ferropericlase. Among the major lower mantle components, we find that this pyrite-type phase holds the strongest affinity to ferrous Fe. This is consistent with quenched experiments in which we observed amorphous bands enriched with Fe and an excessive amount of O, possibly derived from the decompression-induced amorphization of high-pressure samples. Our results support the existence of Fe-rich and dense pyrite-type (Mg,Fe)O2 near the core mantle boundary. It features high density due to its Fe concentration. At the meantime, the pyrite-type phase is known to exhibit low seismic velocity. The formation of this phase suggests some seismic heterogeneities, for example the LLSVP, may have originated from the chemistry between water and surrounding minerals.

How to cite: Hu, Q.: Water modulate the Fe-Mg partitioning in Earth’s deep lower mantle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5856, https://doi.org/10.5194/egusphere-egu24-5856, 2024.

EGU24-7271 | Posters on site | GMPV4.9

Is PREMA exclusively associated with LLSVPs? 

Jingao Liu, Ronghua Cai, Graham Pearson, Andrea Giuliani, Peter van Keken, and Senan Oesch

Studies of ocean island basalts (OIBs) have identified a “Prevalent Mantle” component (or PREMA) that appears to represent one of the fundamental constituents of Earth’s mantle. Recent documentation of this signature in deep-sourced kimberlitic magmatism has increasingly linked PREMA with thermochemical structures above the core mantle boundary (LLSVPs). Yet, kimberlites provide geographically limited sampling of Earth’s mantle, which makes it difficult to identify the spatial association between LLSVPs and the PREMA component sampled by these magmas. To further investigate the global distribution of the PREMA mantle component, we utilize a much more widespread class of mantle-derived magmatism – global Cenozoic alkali basalts, nephelinites and basanites (‘sodic basalts’ hereafter) – that are derived from both continental and oceanic settings. Statistical treatment of the available ~3500 geochemical and isotopic analyses of Cenozoic sodic basalts worldwide shows that at low degrees of melting these magmas exhibit similar Sr-Nd-Hf isotopic characteristics to PREMA. There is no apparent spatial relationship between the distribution of PREMA-like sodic basalts and LLSVPs, implying that the PREMA component is not exclusively associated with LLSVPs. The PREMA-like signature of low-degree sodic basalts occurs in both OIBs and continental magmas, negating an exclusive link to continental lithosphere. Geochemical modelling and mantle convection simulations indicate that PREMA could have been generated soon after Earth accretion, experiencing only minimal melting or enrichment, and then scattered throughout the mantle, including the upper mantle, rather than being the result of mixing between depleted and enriched mantle components. This work indicates that PREMA probably represent a widespread fusible component that can be mingled with other components at various scales to generate all types of mantle magmatism.

How to cite: Liu, J., Cai, R., Pearson, G., Giuliani, A., van Keken, P., and Oesch, S.: Is PREMA exclusively associated with LLSVPs?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7271, https://doi.org/10.5194/egusphere-egu24-7271, 2024.

EGU24-9201 | ECS | Posters on site | GMPV4.9

Imaging of the Mantle Transition Zone with SS Precursors in the Iceland-Mid-Atlantic Ridge Region 

Xiuxuan Jiang, Yunfeng Chen, Yapo Abol ́e Serge Innocent Obou ́e, and Jingchuan Wang

The nature of Iceland hotspot, located on the Mid-Atlantic Ridge, has been subject of contentious debate. Earlier seismic tomographic studies have suggested the presence of a deep mantle plume or confined to the upper mantle without a clear plume affinity. In this study, we utilize SS precursors to image the Mantle Transition Zone (MTZ) beneath Iceland. We collected a large SS precursor dataset that contains teleseismic recordings from all available global broadband stations between year 1976 and 2023. The resulting dataset enables a dense sampling of the Iceland and the Mid-Atlantic Ridge (i.e., 40°-80° N and -70°W to 10° E) with more than 3000 high-quality SS precursor waveforms. We adopted a recently proposed Robust Damped Rank-Reduction method to process the SS precursor data, which enables exploiting the signal coherency in multi-dimensional (4D) data and significantly improving the quality of the weak precursory arrivals. Seismic imaging based on the processed SS precursors effectively captures regional-scale topographic variations of mantle discontinuities, eliminates contaminating noises that produce small-scale artifacts, and enhances the lateral coherency of the MTZ structure.

 

The resulting MTZ images reveal that the 410 km discontinuities are depressed by 5 km compared to regional average, whereas the 660 km discontinuities are uplifted by 6 km, leading to a MTZ of 230 km thick beneath Iceland. The region of depressed 410 extends southwards from the eastern edge of Greenland along the Mid-Atlantic Ridge for a distance about 20 degrees. In comparison, the elevation of 660 is more wide-spread, reaching as far as the northwestern end of Greenland. These observations suggest the interaction of a deep mantle plume with the 660 km discontinuity in a broad area covering the north Mid-Atlantic Ridge. The thick lithosphere beneath Greenland may have channeled the mantle flow towards the ridge, thereby causing the thinning of the MTZ centering on Iceland. In the southeast of the study area, our model also reveals a thinning area, isolated from the Iceland anomaly. The observed complex MTZ topography, in conjunction with multiple low-velocity centers in global tomographic models, may suggest the presence of a bifurcated, deep mantle plume originated from the lower mantle that may feed the shallow hotspots near the Iceland-Mid-Atlantic Ridge.

How to cite: Jiang, X., Chen, Y., Obou ́e, Y. A. ́. S. I., and Wang, J.: Imaging of the Mantle Transition Zone with SS Precursors in the Iceland-Mid-Atlantic Ridge Region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9201, https://doi.org/10.5194/egusphere-egu24-9201, 2024.

EGU24-13850 | ECS | Posters on site | GMPV4.9

Ab initio study of the conductivities of B2 FeSi under core-mantle boundary conditions 

Yonghui Huang, Yunguo Li, and Huaiwei Ni

While the ultralow velocity zones (ULVZs) may hold key information about deep earth dynamics, their elusive state and origin remain as an enigma. Recently, high pressure experiments indicate that ULVZs may form from the B2 FeSi phase crystallized from the outer core containing H and Si. The possibility and impact of the B2 FeSi at the core mantle boundary (CMB) awaits further exploration. The conductivity of the B2 phase can be used to understand its role in deep mantle dynamics and also served as a test for its existence at the CMB. By using first-principles molecular dynamics and Kubo-Greenwood formula, we calculated the thermal and electrical conductivities of B2 FexSi1-x at 135 GPa up to 4,500 K. Our results show that at the CMB conditions, the thermal and electrical conductivities of B2 FeSi are significantly higher than other lower mantle minerals and the core. This would lead to a thermal anomaly region at the CMB, promote the core dynamo and enhance the cooling of the core if the ULVZs are dominated by B2 phase.

How to cite: Huang, Y., Li, Y., and Ni, H.: Ab initio study of the conductivities of B2 FeSi under core-mantle boundary conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13850, https://doi.org/10.5194/egusphere-egu24-13850, 2024.

EGU24-14584 | Posters on site | GMPV4.9

The origin of water in the large igneous provinces: constraints from hydrogen isotope 

Jia Liu, Qunke Xia, and Jingjun Zhou

Large igneous provinces (LIPs), characterized by massive basaltic lava flows and rapid formation over short time frames, exert profound effects on Earth's environment, climate, and mineral resources. Although prior studies have revealed that high water content in the mantle sources would be a critical factor for the genesis of LIPs, the origin of water in their mantle sources remains debated, posing a critical challenge for understanding the geodynamic context of LIP formation and associated deep mantle processes. The water can derive from the primordial components that build the earth, or from the earth surface carried by the subducted oceanic slabs. Here, we conducted coupling analysis of water contents and hydrogen isotopes of the melt inclusions and quenched glasses from the high 3He/4He picrites in Western Greenland and low-Ti type picrites from Emeishan large igneous province. The results show that the high H2O/Ce (>1300) and normal mantle like D/H ratio of the primary magma are distinct to that of the oceanic island basalts and Archean komatiites. Combining the high mantle potential temperature and non-arc like trace elemental patterns, we suggest that the ELIP taps highly hydrous reservoirs in the deep mantle, potentially with water inherited from earth-building materials or the less dehydrated subducted oceanic lithosphere. Our work also raises the caution that the traditionally combined water content and δD analysis for OHMs does not necessarily allow the accurate determination of water concentration of the primary magma. For Western Greenland picrites, the results show water contents from 850 to 1050 ppm by weight, but large variable δD from -75± to -140±8 ‰, which forms the trends well modeled by the kinetic fractionation driven by inward water diffusion into the melt inclusions. The primary δD of the these picrites were inferred to be around -80 ‰, consistent with the recent results for the high 3He/4He submarine basaltic glasses from Loihi, Hawaii. Thus, our work may support a globally consistent primordial water in the origin of chondritic material.

How to cite: Liu, J., Xia, Q., and Zhou, J.: The origin of water in the large igneous provinces: constraints from hydrogen isotope, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14584, https://doi.org/10.5194/egusphere-egu24-14584, 2024.

EGU24-1660 | ECS | Orals | GD7.2

Structural softening in poro-elasto-plastic media 

Yury Alkhimenkov and Ruben Juanes

Structural softening is a well-known phenomenon in single-phase materials. If we consider a single-phase material, assume an elastoplastic rheology, and perform a strain-driven loading under pure shear boundary conditions, the evolution of the integrated stress will exhibit a softening beyond its peak. This is true for non-associated flow rules considering an ideal plasticity model with, for example, Mohr-Coulomb or Drucker-Prager yield criteria. The post-peak softening is usually associated with the development of the localized shear zones. However, this phenomenon hasn’t been properly analyzed for the case of porous rocks modeled with the quasi-static Biot’s poroelastic equations.

In this contribution, we present numerical results considering the poro-elasto-plastic rheology with a focus on structural softening. We show that the post-peak structural softening might be significant and exhibit large stress drops. The most important outcome is that even a little fluid overpressure leads to much larger stress drops compared to scenarios without any kind of fluid overpressure. This result may shed some light on the phenomenon of large earthquakes associated with small injection rates in geothermal or CO2 sequestration fields.

 

References:

Vermeer, P. A. (1990). The orientation of shear bands in biaxial tests. Géotechnique40(2), 223-236.

How to cite: Alkhimenkov, Y. and Juanes, R.: Structural softening in poro-elasto-plastic media, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1660, https://doi.org/10.5194/egusphere-egu24-1660, 2024.

EGU24-4132 | ECS | Orals | GD7.2

On the link between subduction and lithospheric texture : insights from convection in colloidal dispersions 

Manon Pépin, Gianluca Gerardi, Hugo Remise-Charlot, Christiane Alba-Simionesco, and Anne Davaille

Strain-localization along plate boundaries and subduction of the lithosphere are key-features of Earth’s mantle plate tectonics and convective dynamics. Numerous mechanisms, operating on various time and length-scales, are able to produce strain localization. But the exact process(es) that control lithospheric subduction from convection in a viscous mantle remain debated. Laboratory experiments, where one can 1) characterize and control the fluid rheology, and 2) determine the structure/texture of the resulting lithosphere, can give valuable constraints to the ongoing discussion. To date, we have found only one fluid able to produce in the laboratory self-consistent subduction during convection: colloidal dispersions of silica nanoparticles (‘NP’). These fluids encompass a large diversity of rheological behavior, from viscous to elasto-visco-plastic to brittle, depending on the nanoparticles volume fraction. But we can now go one step further, and investigate the links between the rheological properties and the nanoparticles’organization.

 

So we studied Ludox® dispersions with NP of two different diameters (16 and 28 nm) and vary the water concentration, while keeping the ionic content constant. The rheology is characterized using shear rate and oscillatory tests. The organization of the nanoparticles is probed with Small-Angle Neutron Scattering (SANS) and Small-Angle X-ray Scattering (SAXS) measurements, and the solvent (water) state thanks to thermal analysis (ThermoGravimetric Analysis, TGA, and Differential Scanning Calorimetry, DSC). These measurements allow us to identify three types of water, (i) water adsorbed at the surface of the particles, (ii) water confined in nano-cavities and (iii) free water, and to determine the evolution of their amounts with increasing particle volume fraction. Rheology seems mainly controlled by the amount of free water. As the fraction of the latter decreases, the material becomes more heterogeneous at the meso-scale, with the formation of particle aggregates and free water channels. The rheology becomes more non-newtonian with the apparition of a yield stress, which value increases with decreasing free water. In convection-evaporation experiments, this results in the formation of a lithospheric « skin » floating on a less concentrated solution, and strong localization of deformation on this heterogeneous skin that can induce its break-up and subduction. Interestingly enough, subduction is observed for skins still containing a little amount of free water (0.2-1%). On a rocky planet, this suggests that the existence of partial melt in the asthenosphere and the lithosphere could be important to allow subduction. This could explain why localized subduction may exist on present-day Venus: eventhough there is no liquid water ocean on the surface of Venus today, there is plenty of evidence of active volcanism, which indicate the existence of a sizable amount of partial melt.  

How to cite: Pépin, M., Gerardi, G., Remise-Charlot, H., Alba-Simionesco, C., and Davaille, A.: On the link between subduction and lithospheric texture : insights from convection in colloidal dispersions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4132, https://doi.org/10.5194/egusphere-egu24-4132, 2024.

Ophiolites are remnants of oceanic crust and mantle, now typically found within continental mountain ranges. Particularly in areas once part of the Tethys Ocean, ophiolites are often accompanied by narrow strips of metamorphic rocks, commonly referred to as metamorphic soles. These rocks exhibit peak metamorphic conditions characteristic of either granulite or amphibolite facies. Geochronological studies of Tethyan ophiolites indicate that the development of these metamorphic soles occurred almost simultaneously with the crystallization of the ophiolite's crustal sequence. Geological evidence also suggests that the metamorphism of the sole rocks took place concurrently with deformation, likely at the same time as the ophiolite's obduction. In our research, we explore the metamorphic effects of shearing in an ophiolite sequence overlying a crustal sequence. Our findings reveal that a strong crustal lithology can produce additional heat through the dissipation of mechanical energy, which can explain the high temperatures found in metamorphic-sole rocks. In addition, heating of the footwall rocks eventually leads to the migration of the active shear zone from the mantle sequence into the upper crustal domain. This migration is responsible for the metamorphic sole incorporation at the base of the ophiolite. Finally, we demonstrate that stopping the shearing process rapidly cools these rocks, corresponding with the findings from thermochronological studies from Oman ophiolite.

How to cite: Ibragimov, I. and Moulas, E.: A thermo-mechanical model of the thermal evolution and incorporation of the metamorphic sole in the Oman ophiolite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5497, https://doi.org/10.5194/egusphere-egu24-5497, 2024.

EGU24-8478 | Orals | GD7.2

Reaction-driven mineral expansion and its impact on fluid flow 

Viktoriya Yarushina, Johannes C. Vrijmoed, and Lawrence H. Wang

Addressing climate change necessitates shifting from fossil fuels to renewables and implementing carbon capture and storage (CCS). Storing CO2 in mafic and ultramafic rocks is appealing due to the potential for mineral conversion. Recent pilot studies showed the feasibility of mineral CO2 storage in basalts. However, combating climate change requires increasing injection volumes by several orders of magnitude. Discussion continues on whether mineralization processes will still be as efficient at larger scales. One foreseen issue is the potential pore clogging due to mineral precipitation, eventually impeding the reaction. While reactive transport models based on dissolution-precipitation mechanism predict pore clogging and thus the limited extent of reaction, there is clear field evidence for complete reactions in natural analog systems. Besides, developing new injection sites requires pre-injection feasibility studies based on numerical simulations. These simulations aim to provide an initial evaluation of the potential success and challenges associated with the proposed CO2 injection project. They require large-scale, high-resolution simulations, which are challenging for commercially available codes. Recent success in using GPUs for scientific computing combined with matrix-free numerical methods stimulates the development of new numerical models and the revisiting of underlying theoretical approaches. CCS in depleted reservoirs, especially with old plugged-and-abandoned wells, also presents challenges. CO2 interacting with old cement compositions may compromise well integrity, leading to potential CO2 leakage along wellbores. Chemical reactions, fluid flow, and deformation are intricately coupled processes. Studies highlight the dependence of reaction progress both on assumed kinetics and constitutive hydro-mechano-chemical models. While conventional knowledge suggests transport-dominated reactions leading to pore clogging, recent observations challenge this, indicating that reaction-induced alterations occur in the solid phase without changing pore volume. A novel model addressing reaction-driven mineral expansion is presented, preserving porosity while allowing solid volume change. Examining fluid-rock interaction at the pore scale, we derive effective rheology for reacting porous media. The micromechanical model assumes rocks or cement as assemblies of solid reactive grains, accommodating externally applied and reaction-induced stresses through elastic, viscous, and plastic deformation mechanisms. Depending on the level of reaction-induced stresses, the model predicts either pore clogging or porosity-preserving solid volume increase as dominant mechanisms, with the latter facilitating complete reactions. Macroscopic stress-strain constitute laws account for chemical alteration and viscoelastic deformation, elucidating the dependence of mechanical rock properties on fluid chemistry [1]. We use a two-phase continuum medium approach and local equilibrium thermodynamic models [2] to investigate the coupling between reaction, deformation, and fluid flow on a larger scale. We consider two simple examples of the carbonation of portlandite and the hydration of mantle rocks. Both reactions are associated with a change in solid volume. We show how reaction-driven mineral expansion affects the porosity evolution and reaction progress.

References:

1. Yarushina, V.M., Y.Y. Podladchikov, and H.L. Wang, On the Constitutive Equations for Coupled Flow, Chemical Reaction, and Deformation of Porous Media. Journal of Geophysical Research-Solid Earth, 2023. 128(12).

2. Vrijmoed, J.C. and Y.Y. Podladchikov, Thermolab: A Thermodynamics Laboratory for Nonlinear Transport Processes in Open Systems. Geochemistry Geophysics Geosystems, 2022. 23(4).

How to cite: Yarushina, V., Vrijmoed, J. C., and Wang, L. H.: Reaction-driven mineral expansion and its impact on fluid flow, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8478, https://doi.org/10.5194/egusphere-egu24-8478, 2024.

EGU24-8862 | Posters on site | GD7.2

Multicomponent Fluid Flow in Deforming and Reacting Porous Rock in the Earth’s crust: hydro-mechanical-chemical model 

Andrey Frendak, Lyudmila Khakimova, Leonid Aranovich, and Yury Podladchikov

We propose a coupled hydro-mechanical-chemical model and its 1D numerical implementation. We demonstrate its application to the model filtration of a multicomponent fluid in deforming and reacting host rocks, considering changes in the densities, phase proportions, and the chemical compositions of the coexisting phases.

The numerical results show the propagation of a porosity wave by means of a viscous (de)compaction mechanism accompanied by the formation of an elongated zone with higher filtration properties. After the formation of such a channel, the formation and propagation of the reaction fronts occurs and are associated with the transformation of the mineral composition of the original rock.

How to cite: Frendak, A., Khakimova, L., Aranovich, L., and Podladchikov, Y.: Multicomponent Fluid Flow in Deforming and Reacting Porous Rock in the Earth’s crust: hydro-mechanical-chemical model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8862, https://doi.org/10.5194/egusphere-egu24-8862, 2024.

EGU24-10501 | Orals | GD7.2 | Highlight

Modelling focused fluid flow in the subsurface: its controlling factors and the formation of seismic chimney  

Lawrence Hongliang Wang and Viktoriya Yarushina

Seismic chimneys, prevalent along continental margins, intricately contribute to Earth's degassing processes, facilitating fluid migration from the deep Earth to the surface. This phenomenon carries significant implications for subsurface storage utilization. Among the principal mechanisms driving seismic chimney formation is the fluid flow instability within porous subsurface rocks. While numerical studies of geodynamical two-phase flow have successfully replicated vertical fluid flow structures, many of these models overlook elastic compaction, advection of solid and poro-space, and geological heterogeneity, thereby limiting their applicability in subsurface scenarios. In addressing these limitations, this study incorporates a viscoelastic rheology into the geodynamical two-phase flow model to explore the controlling factors influencing the formation of focused fluid flow, accounting for various rock properties, including geological heterogeneity. Initial investigations into the impact of elastic compaction by varying Deborah numbers reveal a limited influence on fluid flow compared to viscous compaction. Through a comparative analysis of models with and without advection, we observe the potential importance of solid advection in fluid migration, particularly under conditions of high background porosity (≥0.1) and relatively low permeability. This effect is accentuated when the solid matrix undergoes significant deformation. Channel widths range from 2-3 compaction lengths to a maximum of 5-10 compaction lengths, primarily contingent on the viscosity ratio between shear and bulk viscosity and the fluid supply. Further simulations involving fluid flow encountering a horizontal block with rock heterogeneity and geological heterogeneity demonstrate the potential for fluid penetration through the structure or deflection to the side, contingent upon rock properties and block size. Finally, we apply our model to a specific seismic chimney at Loyal Field in Scotland, UK, successfully reproducing the observed upward-bending structure in the seismic image with a consistent width-height ratio. This comprehensive investigation sheds light on the complex interplay of various factors influencing focused fluid flow, including geological heterogeneity, thereby contributing valuable insights to the understanding of seismic chimney formation in real-world geological settings.

 

How to cite: Wang, L. H. and Yarushina, V.: Modelling focused fluid flow in the subsurface: its controlling factors and the formation of seismic chimney , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10501, https://doi.org/10.5194/egusphere-egu24-10501, 2024.

Seeking to better investigate the mechanism of transformational faulting (i.e. dynamic olivine phase transition considered as the main earthquake mechanism in the deep Upper Mantle), experiments were carried out in a 1-atm rig using synthetic samples of peridotite analogues. The samples consisted of Mg2GeO4 with minor MgGeO3. In brief, using Ge instead of Si allows studying deep processes without increasing the confining pressure. At 1 atm, γ-Mg2GeO4 (high-pressure olivine polymorph) transitions to α-Mg2GeO4 (olivine) at 810 °C. The hope was to generate and document strain localization features due to local phase transition and/or locally nucleate the phase transition due to strain localization. Working with this material in this apparatus between 760 and 860 °C could have appeared clever.

The experimental setup allowed runs lasting a few hours up to a full day. However, after one day at 800 °C and an axial stress > 300 MPa, the synthetic samples, characterized by a small grain size and a high homogeneity, remained perfectly elastic. Runs were too cold and dry for any nucleation of the high-pressure phase γ-Mg2GeO4. Due to both kinetic and rheological issues, beginning to observe strain localization would have taken months, which would most probably have killed the apparatus in only one run due to the corrosion of the external furnace. 

This failed experimental journey turned into an opportunity to study something else: the temperature window was shifted to 950-1250°C. Some experiments revieled a significant viscosity reduction in a narrow temperature window (1000-1150°C), which we propose to interpret as an analogue of the lithosphere-Asthenosphere boundary (LAB). Until recently, melting was the only “transformation” considered in the interrogations about the reduced viscosity of the LAB. In this study, based on our unexpected experimental results, we document a solid-state viscosity reduction that seems to be associated with grain-boundary instability in the context of a competition between diffusive and displacive processes (i.e. premelting). We propose to broaden the discussion including solid-state transformations and potential metastable phases that are not yet fully understood. Although the most studied mineral, olivine has not revealed all its secrets. Additional experiments are required to fully understand what happened.

How to cite: Ferrand, T. P. and Deldicque, D.: Unexpected softening of a synthetic peridotite analogue (magnesium germanate) in a narrow temperature window: the Lithosphere-Asthenosphere Boundary accidentally reproduced?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10931, https://doi.org/10.5194/egusphere-egu24-10931, 2024.

EGU24-14329 | Orals | GD7.2 | Highlight

Generation of Felsic Crust: A Fluid Transport Perspective 

Leonid Aranovich, Lyudmila Khakimova, Andrey Frendak, and Yury Podladchikov

Continental crust consists mainly of felsic rocks rich in silicon and aluminum, and is formed in subduction zones via processes linked to plate tectonics. Most recent models of the felsic crust formation rely on differentiation of basaltic magma generated via partial melting of mantle wedge peridotite under influence of a fluid phase liberated from subducting hydrated oceanic crust. Here we present an alternative model that invokes metasomatic alteration of mantle peridotite due to interaction with a water-rich fluid phase. The model is based on calculations of solid phase assemblages in equilibrium with a fluid saturated in major elements at varying pressure-temperature conditions. Calculations employed THERMOLAB software [1] along with thermodynamic properties of solids (both the standard state and mixing) according to [2,3] and aqueous solution models [4]. The calculations reveal that the SiO2 content in the fluid exerts major control on the solid phase assemblage. On decompression path from 2.5 to 0.2 GPa at 700oC in the model system NCMASH it changes from a six-mineral assemblage olivine (Ol) + orthopyroxene (Opx) + pargasite(Parg) + diopside + biotite + clinochlore to a three-phase Ol+Opx+Parg. The system Si/O ratio along the path increases from 0.26 (close to that of Ol, Si/O=0.25) to 0.28, thus pre-conditioning mantle protolith for subsequent melting that would generate diorite-granodiorite-granite melts.

How to cite: Aranovich, L., Khakimova, L., Frendak, A., and Podladchikov, Y.: Generation of Felsic Crust: A Fluid Transport Perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14329, https://doi.org/10.5194/egusphere-egu24-14329, 2024.

We present undated results of a numerical model of pressure increase in a quasi-isochoric magma system due to the flotation of bubble-crystal clusters (vesicular mafic enclaves), that are common in silicic rocks that experience magma chamber refill by water and CO2-saturated basaltic magma. The model accounts for water solubility and diffusion and utilizes measured size distributions of mafic enclaves in volcanic and plutonic rocks around the world. These mafic enclaves have sizes ranging from (~1 to >30 cm), lognormal size distribution that we explain by flotation. They have lower densities (density difference =10-30%) than silicic hosts due to bubbles. The principal results of the model are: 1) enclaves are capable of rapid (days-months) flotation leading to pressurization of shallow magma chambers over cracking limit (100 MPa) using fluid rise mechanisms below; 2) The dynamics of pressure increase is strongly non-linear and is determined by the initial size distribution of enclaves, and other parameters; 3) Diffusion of water out of enclaves is slower than the rise time for most realistic viscosities of the silicic host melt. We consider cases when overpressuring causes density reversal due to solubility increase, and consider the role of convection. We present examples of high concentrations of enclaves within silicic domes that we explain by pre-eruption accumulation by flotation to the roof 

Bindeman I.N., Podladchikov Y.Y., Inclusions in volcanic rocks and a mechanism for triggering volcanic eruptions, Modern Geology, 19, 1-11, 1993.
Steinberg, G.S., Steinberg, A.S., Merzhanov A.G., Fluid mechanism of pressure growth in volcanic (magmatic) systems, Modern Geology, 13, 257-265, 1989a.
Steinberg, G.S., Steinberg, A.S., Merzhanov A.G., Fluid mechanism of pressure growth and the seismic regime of volcanous prior to eruption, Modern Geology, 13, 267-274, 1989b.
Steinberg, G.S., Steinberg, A.S., Merzhanov A.G., Fluid mechanism of pressure rise in volcanic (magmatic) systems with mass exchange, Modern Geology, 13, 275-281, 1989c.

How to cite: Podladchikov, Y. and Bindeman, I.: Vesiculated basaltic enclave flotation as a mechanism of fluid pressure increase in magma chambers during silicic-basaltic magma mixing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14561, https://doi.org/10.5194/egusphere-egu24-14561, 2024.

EGU24-14845 | ECS | Posters on site | GD7.2

Multicomponent Pore Fluid Transport by Hydration Porosity Waves in the Litosphere: A Model for Continental Crust Formation 

Lyudmila Khakimova, Andrey Frendak, Leonid Aranovich, and Yury Podladchikov

Revealing of continental crust formation mechanism is a fundamental problem. There are metamorphic based theories and leading magmatic ones. Most recent models rely on differentiation of basaltic magma generated by partial melting of peridotite under influence of a fluid escape from subducting hydrated oceanic crust.

Here we present hypothesis of alternative mechanism of continental crust formation which invokes the multicomponent pore fluid transport by reactive porosity waves through the base of the Lithosphere. It includes partial hydration of mantle peridotite due to interaction with aqueous solutions transported through fluid-rich channels-like structures in rocks undergoing visco-elastic deformation coupled with reactions, phase transformations, volume and density changes.

To support the hypothesis, we propose a coupled hydro-mechanical-chemical model for simulating the filtration of multicomponent fluid through deforming mineral matrix treating zero porosity limit. Along with a number of constitutive relations, this model is closed by tabulated thermodynamic data, which are to be preliminarily calculated using linprog minimization in ThermoLab. We present 2D numerical implementation utilizing accelerated pseudo-transient numerical scheme. Results illustrate hydration porosity wave propagation witj peridotite alteration and the visco-elastic deformation of the zero porosity mineral matrix, with reference to the system up to 12 components including the corresponding solid and aqueous solutions.

How to cite: Khakimova, L., Frendak, A., Aranovich, L., and Podladchikov, Y.: Multicomponent Pore Fluid Transport by Hydration Porosity Waves in the Litosphere: A Model for Continental Crust Formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14845, https://doi.org/10.5194/egusphere-egu24-14845, 2024.

EGU24-15095 | ECS | Posters on site | GD7.2

Control of buoyancy forces and thermal softening on the emplacement of low-angle thrust sheets during continental collision 

Olga Dubina, Stefan Schmalholz, and Yury Podladchikov

A characteristic feature of some collisional orogens, such as the Alps, are low-angle thrust sheets. The most prominent thrust sheet in the Alps is likely the Glarus nappe that has been displaced at least 30 to 40 km. The Glarus thrust has been studied for more than 150 years and these studies created much knowledge of, for example, rock deformation, strain localization, and softening mechanisms. However, the type of forces and the mechanisms that drive the tens of kilometers displacement at a low angle during continental collision remain unclear. Furthermore, the relative importance of softening mechanisms at the base of the thrust sheet is still disputed and proposed mechanisms include fluid overpressure, grain size reduction, or fluid release caused by shear heating.

In this study, we investigate the formation of low-angle thrust sheets and nappes with two-dimensional thermo-mechanical numerical models. We consider a lithosphere-mantle system with a continental crust that exhibits initially a horizontal variation in crustal thickness. The lithosphere is shortened by far-field convergence velocities. For simplicity, we apply thermal softening due to shear heating as the only softening mechanism since this mechanism requires the least assumptions in our thermo-mechanical model. The applied numerical algorithm is based on a staggered finite difference discretization and a matrix-free iterative pseudo-transient solver.

Preliminary numerical results indicate that buoyancy forces due to lateral crustal thickness variations can trigger the formation of sub-horizontal thrusting and a switch from a locally pure shear-dominated to a simple shear-dominated deformation. Without lateral thickness variations and associated buoyancy forces, thermal softening causes thrusting with 45-degree angles and, hence, no low-angle thrusting. We perform systematic numerical simulations and dimensional analysis to evaluate the conditions that are required to generate low-angle thrusting during lithospheric shortening.

How to cite: Dubina, O., Schmalholz, S., and Podladchikov, Y.: Control of buoyancy forces and thermal softening on the emplacement of low-angle thrust sheets during continental collision, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15095, https://doi.org/10.5194/egusphere-egu24-15095, 2024.

EGU24-15242 | ECS | Posters on site | GD7.2

Numerical modelling and classification of thermo-hydro-mechanical convective regimes 

Boris Antonenko, Lyudmila Khakimova, and Yury Podladchikov

The simulation and visualization of geodynamical processes poses a major challenge for due to spatial and time scales spanning many orders of magnitude and highly nonlinear phenomena. Modeling and solving such processes are necessary in order to accurately predict changes in natural systems. Two-phase models of fluid flow in deformable porous media are widely used to explain the various processes that occur in the Earth’s interior and subsurface. However, thermal processes, especially volume changes caused by thermal expansion, are typically ignored.

In this study, numerical simulation methods were used to describe a mathematical model of heat transfer processes in a porous media. The purpose of these studies is to determine the influence of nondimensional parameters (Rayleigh numbers) on the convection regimes (free and porous convections). To study these problems, numerical modeling of a nonlinear thermo-hydro-mechanical processes in porous materials filled with a fluid under gravity. The finite difference staggered grid discretization and a graphics processing unit based pseudo-transient solver are utilized in the numerical simulation.

We perform systematic numerical simulations and dimensional analysis to classify the regimes of convection.

How to cite: Antonenko, B., Khakimova, L., and Podladchikov, Y.: Numerical modelling and classification of thermo-hydro-mechanical convective regimes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15242, https://doi.org/10.5194/egusphere-egu24-15242, 2024.

EGU24-15390 | ECS | Posters on site | GD7.2

Numerical modelling of antigorite dehydration at 3 GPa: reaction-induced stress variations and effects of tectonic forcing 

Kristóf Porkoláb, Evangelos Moulas, and Stefan Schmalholz

Dehydration reactions at high pressures are considered as sources of stress perturbations potentially leading to the nucleation of intermediate-depth earthquakes. Dehydration reactions entail the release of water and significant solid volume changes, while solid deformation, fluid flow, and the migration of the reaction front interact with each other. Observation-based quantification of such complex interactions is challenging; hence, the exact mechanisms of dehydration-induced seismicity remain unclear. One of the most prominent dehydration reactions in subducted slabs, that may contribute to intermediate-depth seismicity, is the breakdown of antigorite at high pressures. To improve the understanding of this process, we quantify interactions between the metamorphic reaction, solid deformation, and fluid flow for the phase transformation of antigorite --> enstatite + forsterite + water. We present a two-phase, hydro-mechanical-chemical model that is based on the coupled solution of rock deformation, Darcy-flow of pore fluids, and equilibrium thermodynamics of the dehydration reaction (assuming isothermal conditions). We consider total and non-volatile mass conservation, while solid and fluid densities are based on thermodynamic lookup tables. We investigate the magnitude of reaction-induced stresses and test the effects of kinematic boundary conditions and rheological heterogeneities via a broad parameter study. We relate our findings to natural examples of antigorite dehydration and discuss implications for dehydration-induced earthquakes.

Acknowledgements

The reported investigation was financially supported by the National Research, Development and Innovation Fund, Hungary (PD143377).

How to cite: Porkoláb, K., Moulas, E., and Schmalholz, S.: Numerical modelling of antigorite dehydration at 3 GPa: reaction-induced stress variations and effects of tectonic forcing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15390, https://doi.org/10.5194/egusphere-egu24-15390, 2024.

EGU24-15613 | Posters on site | GD7.2

Numerical simulation of multicomponent multiphase reactive fluid flow in porous media 

Anna Isaeva, Lyudmila Khakimova, and Yury Podladchikov

Multicomponent multiphase reactive transport in porous media controls various phenomena in geological formations such as carbonization, fluid flow in a petroleum reservoir, mobility of radioactive waste in repositories, etc. Despite the obvious differences between these geological processes, they have much in common from a numerical simulation point of view.

We draw parallels between mathematical models of processes from two different areas of research. Firstly, we study the process of carbonization. Secondly, we consider the process of retrograde condensation, which is known to occur when natural gas flows in reservoir rock (during isothermal pressure reduction). Retrograde condensation is a property of multicomponent mixtures, such as natural gas. 

Both systems considered exhibit complex behavior and phase  transitions. But both systems can be described by the same generalized equations. We discuss the differences and similarities between these mathematical models.

How to cite: Isaeva, A., Khakimova, L., and Podladchikov, Y.: Numerical simulation of multicomponent multiphase reactive fluid flow in porous media, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15613, https://doi.org/10.5194/egusphere-egu24-15613, 2024.

EGU24-15739 | Posters on site | GD7.2

Occurrence of eclogite in felsic continental rocks as a natural consequence of burial 

Johannes C. Vrijmoed, Yury Y. Podladchikov, Marcin Dabrowski, and Lyudmila Khakimova

The occurrence of eclogite enclosed in felsic continental rocks have been subject of intense discussion over several decades. The eclogite facies mineralogy preserves the only evidence that the rocks were buried to great depth and therefore this has significant consequences for the understanding of geodynamic processes in continental collision zones. However, often the enclosing felsic gneiss lacks evidence of this high-pressure metamorphism.

This apparent conflict in metamorphic pressure is founded on experimental phase equilibria studies in which pyroxene and plagioclase in igneous mafic rocks transform at high pressure to the characteristic garnet and omphacite assemblage of eclogite. In contrast, the felsic rocks preserve a mineral assemblage expected to equilibrate at lower pressure. A common explanation is that the enclosing felsic gneiss was retrogressed on the exhumation path, whereas eclogite has been preserved due to slower reaction kinetics in mafic rocks. The preservation of original igneous structures of various mafic rocks and incomplete reactions in metagabbro may also be attributed to metastability. Subsequently, it has been shown that large areas of the enclosing felsic gneiss have retained their original low-pressure mineral assemblage (e.g. Peterman et al., 2009). Consequently, large areas of felsic gneiss were never metamorphosed in the eclogite facies. It is firmly established that fluids play an important role in metamorphic reactions. In contrast, the role of mechanics and the heterogeneity of rock mechanical properties during metamorphism has received less attention.

Mechanical properties of mafic rocks can be different from the surrounding felsic lithologies. Therefore, a mechanical model was proposed for a mafic inclusion in felsic continental rock in which the entire domain was subjected to burial (Podladchikov & Dabrowski, 2017). The model predicted a much higher pressure in the mafic inclusion than in the felsic matrix. The overpressure in the mafic inclusion resulted from difference in compressibility between the mafic and felsic lithologies. This may explain the contrast in high pressure eclogite compared to the enclosing lower pressure felsic continental rocks.

In this study, we combine the mechanical model with thermodynamic calculations using Thermolab (Vrijmoed & Podladchikov, 2022) and apply it to ultra-high-pressure rocks in western Norway. We retrieve density, compressibility, and thermal expansivity for observed rocks from phase equilibria calculations as input into the mechanical models. With Thermolab, complex fluids including more than 40 aqueous species, and multi-component melt and solid solution models, can be conveniently coupled to reactive transport and mechanical models to quantify the effect of burial overpressure.

References:

Podladchikov, Y. Y., Dabrowski, M., (2017), Overpressure by burial, Geophysical Research Abstracts, Vol. 19, EGU2017-18976, 2017, EGU General Assembly 2017.

Vrijmoed, J.C. and Y.Y. Podladchikov, (2022), Thermolab: A Thermodynamics Laboratory for Nonlinear Transport Processes in Open Systems. Geochemistry Geophysics Geosystems, 2022. 23(4).

Peterman, E. M., Hacker, B.R., Baxter, E. F. (2009), Phase transformations of continental crust during subduction and exhumation:Western Gneiss Region, Norway, Eur. J. Mineral. 2009, 21, pp. 1097-1118

How to cite: Vrijmoed, J. C., Podladchikov, Y. Y., Dabrowski, M., and Khakimova, L.: Occurrence of eclogite in felsic continental rocks as a natural consequence of burial, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15739, https://doi.org/10.5194/egusphere-egu24-15739, 2024.

EGU24-16643 | ECS | Posters on site | GD7.2

Multistep Numerical THMC Reactive Porosity Waves Transport Model to Explain Intraplate Volcanism and Mantle Metasomatism. 

Marko Repac, Lyudmila Khakimova, Yury Podladchikov, Kurt Panter, Stefan Schmalholz, and Sebastien Pilet

Ongoing debates persist regarding the role of the lithospheric mantle in the generation of intraplate volcanoes. Most geochemical models propose that these volcanoes originate from magmas formed in the asthenosphere. Intraplate basalt composition, particularly their high content of trace elements, implies that these magmas are produced at low degree of partial melting. However, the melt migration through the lithospheric mantle remains largely unexplored. As these small quantities of magma traverse the lithosphere, their limited heat transport results in rapid cooling due to the lithosphere's strong geotherm (McKenzie, 1989), casting doubt on their ability to directly reach the surface. In contrast, this process induces a chemical effect characterized by the metasomatic enrichment of the lithospheric mantle, observed across oceanic, continental, and cratonic environments.

Here, we developed a numerical finite difference model, incorporating thermo-hydro-chemical-thermal (THMC) processes, to investigate melt migration across the lithosphere. The model includes conservation equations for mass, fluid, and solid momentum, featuring a non-linear porosity-permeability relation for decompaction weakening and reactive porosity waves essential for flow channelization. Thermodynamic calculations employed Thermolab (Vrijmoed & Podladchikov, 2022), a versatile Gibbs energy minimizer. Amphiboles and phlogopites are crucial phases for mantle metasomatism and alkaline magma generation. We successfully model these phases within expected PT ranges. Using both solution models and fixed composition phases.

The model progresses through multiple steps, initiating at the asthenosphere-lithosphere boundary. Initial melt, present there if volatile content is sufficient, migrates upward with a decreasing volume but increasing volatile content as the pressure and temperature decrease. At a given point, the freezing effect of volatiles on mantle melting temperature is no longer sufficient to stabilize melt in equilibrium with the surrounding mantle. Melt migration concludes with the formation of hydrous phases like pargasite or phlogopite depending on the pressure. The second step, addressing excess volatiles after hydrous phases crystallization, involves their further upward transport as fluid, metasomatizing the overlying mantle until depletion of fluid. This process explains several aspects of metasomatism, such as hydrated phase formation and cryptic metasomatism associated with fluid migration. On the other hand, our model confirms that magma does not seem capable of crossing the lithosphere without reacting with the surrounding mantle and crystallizing. To take this further, we consider the hypothesis that the process of melt transport in the lithosphere occurs through the repeated migration of several pulses of magma from the asthenosphere. The emplacement of the first porosity wave is fundamental in establishing a pathway through which all successive pulses will traverse. Following this intricate process, a more extensive segment of the lithosphere undergoes metasomatism. Additionally, the recurrent influx of melt/fluid gradually elevates temperatures in the metasomatized area, potentially leading to the subsequent re-melting of hydrous phases, thereby engendering alkaline melts observed at the surface.

  • McKenzie, D. (1989). Some remarks on the movement of small melt fractions in the mantle. Earth and Planetary Science Letters, 53-72.
  • Vrijmoed & Podladchikov. (2022). Thermolab: A Thermodynamics Laboratory for Nonlinear Transport Processes in Open Systems .G3, 23, e2021GC010303

How to cite: Repac, M., Khakimova, L., Podladchikov, Y., Panter, K., Schmalholz, S., and Pilet, S.: Multistep Numerical THMC Reactive Porosity Waves Transport Model to Explain Intraplate Volcanism and Mantle Metasomatism., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16643, https://doi.org/10.5194/egusphere-egu24-16643, 2024.

EGU24-16982 | ECS | Posters on site | GD7.2

Microstructural relationships from locally equilibrated domains in UHP eclogites (Snieznik Massif, NE Bohemian Massif) 

Malgorzata Nowak, Lucie Tajcmanova, Jacek Szczepanski, and Marcin Dabrowski

The Snieznik eclogites experienced peak ultrahigh-pressure (UHP) metamorphism in around ~770°C at ~3.2 GPa followed by isothermal decompression and amphibolite-facies retrogression during Variscan Orogeny. The well-preserved peak metamorphic assemblage of these UHP eclogites comprises garnet + omphacite + kyanite + phengite + rutile + coesite. The mineral assemblage connected with the isothermal decompression episode is present in the form of diopside-amphibole-plagioclase symplectites that are locally disintegrating the main foliation.

Here, we investigate plagioclase rims developed around kyanite at the interface with quartz and diopside-plagioclase symplectite. They are present only around kyanite occurring in the vicinity of zones developed during the isothermal decompression event. In some parts, the plagioclase rims are locally replaced by the diopside-plagioclase symplectite. The monomineralic plagioclase rims, having max. 20 µm radial thickness, are polycrystalline. They consist of individual plagioclase grains (each 2-15 µm in diameter) with different crystallographic orientations. The rims as a whole exhibit zoning with the highest Ca content observed at the contact with the kyanite grains. The measured CaO content increases from ~2% near quartz and diopside-plagioclase symplectite to ~6% at the kyanite boundary.

In this contribution we investigate the chemical and mechanical effects, that might have contributed to the preservation of the observed zoning and the microstructural heterogeneity of the rims.

How to cite: Nowak, M., Tajcmanova, L., Szczepanski, J., and Dabrowski, M.: Microstructural relationships from locally equilibrated domains in UHP eclogites (Snieznik Massif, NE Bohemian Massif), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16982, https://doi.org/10.5194/egusphere-egu24-16982, 2024.

EGU24-17074 | ECS | Posters on site | GD7.2

Thermal porosity waves 

Ludovic Räss, Ivan Utkin, and Yuri Podladchikov

Fast vertical fluid transfers in the crust play a crucial role in transporting elements and energy from deep environments into the shallow subsurface. These fluid transfers also impact magmatic processes, metamorphism, and heat distribution. Heat distribution in the subsurface is key for temperature-dependent geological processes, geothermal energy, and reservoir operations. Therefore, assessing the efficiency of heat transport by localised fluid flow is important.

Nonlinear porosity waves, resulting from hydro-mechanical interactions, provide a mechanism for fast vertical fluid transfers in the subsurface. However, their ability to transport heat has not been fully explored yet.

In this study, we investigate the coupling of hydro-mechanical processes with thermal processes to assess the efficiency of heat transport by porosity waves in a porous subsurface environment. We use numerical simulations to solve the coupled thermo-hydro-mechanical equations and present high-resolution modeling results. We also evaluate the role of a consistent and conservative formulation. Our preliminary findings suggest that porosity waves do not significantly enhance heat transfer in the subsurface. Additionally, we discuss the influence of parameters such as porosity, permeability, and fluid properties on the efficiency of heat transport.

How to cite: Räss, L., Utkin, I., and Podladchikov, Y.: Thermal porosity waves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17074, https://doi.org/10.5194/egusphere-egu24-17074, 2024.

Numerous studies emphasize the significance of thermal softening induced by shear heating and the concurrent generation of ductile shear zones in geological processes spanning various spatial and temporal scales. Thermal softening is proposed as a primary mechanism in the formation of tectonic plate boundaries and as a potential mechanism of intermediate-depth and deep-focused earthquakes, where large confining pressure inhibits brittle fracture. In the latter scenario, seismic velocities during shearing are achieved through the spontaneous viscous dissipation of stored elastic energy, a phenomenon known as self-localizing thermal runaway (SLTR) [1].

Resolving SLTR poses a formidable numerical challenge due to the multiscale nature of the process. The slow initial stage of differential stress buildup and strain localization is succeeded by the rapid development of a thin shear zone, necessitating high spatial and temporal resolution. Prior numerical studies of self-localizing thermal runaway were confined to 1D, restricting applications to less realistic geometries and simpler model setups.

In this study, we explore the viscoelastic effects of spontaneous flow localization through numerical modeling in 2D. We develop a fully coupled thermo-mechanical solver utilizing a novel conservative energy formulation. Our work demonstrates the potential for SLTR instability in various 2D model setups. Through systematic numerical experiments, we compare the onset of localization with 1D predictions. Additionally, we investigate the role of heterogeneities in the distribution of material properties on the development of a ductile shear zone.

[1] Braeck, S., & Podladchikov, Y. Y. (2007). Spontaneous thermal runaway as an ultimate failure mechanism of materials. Physical Review Letters98(9), 095504.

How to cite: Utkin, I.: Spontaneous strain localisation in a viscoelastic material owing to thermal softening , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17292, https://doi.org/10.5194/egusphere-egu24-17292, 2024.

EGU24-19341 | Posters on site | GD7.2 | Highlight

Reactive porosity waves in a dehydrating and deforming slab: a scale invariant fluid release process 

Timm John, Liudmila Khakimova, Konstantin Huber, Johannes Vrijmoed, Yuri Podladchikov, and Marco Scambelluri

Subduction of hydrated lithosphere slabs into the mantle leads to the release of hydrous fluids, which contribute to a wide range of subduction zone phenomena, such as arc volcanism and seismicity. The efficiency of slab devolatilization is crucial for maintaining the overall stability of the Earth's chemical reservoirs over geological timescales. The formation of channelized fluid flow structures during dehydration, such as olivine veins observed in the Erro Tobbio meta-serpentinites (Italy), enhances the efficiency of fluid release from the subducting slab and might be crucial for devolatilization to keep up with the rate of plate subduction.

Observed olivine-rich vein assemblages and the presence of mineral-bound H2O in the matrix is indicative of high temperatures and partial dehydration. Porosity structures develop into vein-like structures at the onset of dehydration due to intrinsic chemical heterogeneities [1], with connectivity being already reached at low porosities [2]. As dehydration progresses, the fluid pressure in the porous network rises, and buoyancy forces lead to an upward fluid flow in the rock. Porosity waves are a potential mechanism to explain fluid flow focusing structures in rocks undergoing viscous deformation.

This work presents a 2D hydro-mechanical-chemical model for reactive porosity waves in a dehydrating and deforming serpentinite that is part of a subducting slab. Based on [3], we chose SiO2 as the metasomatic agent in a MgO-FeO-SiO2 system with H2O in excess. As model input, we use chemical data of serpentinites from the Mirdita ophiolite (Albania) that has not entered a subduction zone. The 2D chemical mapping of the sample from outcrop down to µm-scale shows scale-invariant heterogeneities of SiO2 and FeO. Similar heterogeneities occur on the km-scale where they manifest as lithological differences between serpentinized harzburgites and dunites. This dataset of chemical maps ranging continuously from the µm- to dm-scale represents a scale-independent pattern of chemical heterogeneities in a dehydrating slab.

Numerical results using this data as input show spontaneous formation of fluid-rich high-permeable channels in deforming and dehydrating serpentinite associated with further olivine formation during the reactive flow of Н2О−SiО2 fluid carrying low SiO2 concentration. The numerical simulations show similar pattern to field observations from Erro Tobbio. We conclude that the formation of a fluid channeling network takes place from the µm- up to km-scale and provides the main fluid escape mechanism in subduction zones.

 

[1] Plümper, O. et al. Fluid escape from subduction zones controlled by channel-forming reactive porosity. Nat Geosci 10, 150–156 (2017).

[2] Bloch, W. et al. Watching dehydration: Seismic Indication for Transient Fluid Pathways in the Oceanic Mantle of the Subducting Nazca Slab. Geochem Geophy Geosy 19, doi:10.1029/2018gc007703 (2018)

[3] Huber, K. et al. Formation of olivine veins by reactive fluid flow in a dehydrating serpentinite. Geochem Geophy Geosy, 23, e2021GC010267 (2022).

How to cite: John, T., Khakimova, L., Huber, K., Vrijmoed, J., Podladchikov, Y., and Scambelluri, M.: Reactive porosity waves in a dehydrating and deforming slab: a scale invariant fluid release process, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19341, https://doi.org/10.5194/egusphere-egu24-19341, 2024.

EGU24-19434 | Posters on site | GD7.2

Numerical assessment of effective bulk moduli of porous rocks using high-performance computing on GPUs 

Maxim Yakovlev and Victoriya Yarushina

The coupled process models incorporate fluid flow, chemical transport, and mechanical deformation equations. These equations adhere to the thermodynamic principles ensuring the preservation of mass and energy within the system. However, for accurate predictions, it is crucial to establish closure equations that provide additional information and ensure the model's completeness. Closure equations are derived either from extrapolating experimental data or from micromechanical models that consider processes at the scale of individual grains or particles. Microscale models are often based on simplified analytical solutions obtained for idealized conditions, which may not fully capture the complexity of real-world situations. For instance, these models may assume a dilute concentration of voids or pores, neglecting interactions between the pores. While this assumption may be suitable for very small porosities below 1%, it may not accurately reflect interactions at porosities around 10%, influencing the compaction process. One approach to address this challenge is to derive more sophisticated analytical solutions, which may sometimes be impractical. Alternatively, a common strategy is to retain simplified solutions and validate them against numerical simulations that include multiple interacting voids. Effective bulk modulus, frequently employed to describe compaction-driven fluid flow in porous rocks, relies on effective media models. We propose a new effective media model based on a Representative Volume Element consisting of multiple interacting pores. To address stress and strain field interactions caused by multiple pores in an elastoplastic matrix, we utilize the numerical simulator CAE Fidesys, implementing classical associated plastic flow laws with von Mises and Tresca yield criteria. For viscoplastic rocks, the correspondence principle is applied. We derive 2D effective stress-strain relations for porous viscoelastoplastic rocks under a general non-hydrostatic stress field and compare the results with existing and novel analytical solutions.

How to cite: Yakovlev, M. and Yarushina, V.: Numerical assessment of effective bulk moduli of porous rocks using high-performance computing on GPUs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19434, https://doi.org/10.5194/egusphere-egu24-19434, 2024.

EGU24-19660 | ECS | Posters virtual | GD7.2

Role of pore fluids in time-dependent deformation and microcracking of rock under high deviatoric stress 

Nikita Bondarenko, Roman Makhnenko, and Yury Podladchikov

Rock underground may be exposed to elevated deviatoric stress over prolonged time period resulting in time-dependent deformation and microcracking. This process of subcritical time-dependent deformation is sensitive to environmental conditions, such as applied state of stress, presence and chemical composition of pore fluids, and drainage conditions. To improve the understanding of processes occurring at subcritical stress, the laboratory brittle creep experiments are conducted on Berea sandstone specimens under various conditions. Strong correlation between time-dependent deformation and microcracking activity is observed in all conducted tests. Significant variation of magnitude-frequency relation of the acoustic emission signals occurs during macroscopic failure preparation, which can serve as a potential prognostic feature. The collected data on time-dependent deformation is interpreted by introducing viscosity as a coefficient of proportionality between deviatoric strain rate and applied deviatoric stress. It appears that viscosity is exponentially decreasing when the state of stress is approaching critical conditions associated with macroscopic failure. Empirically-based relationship is established describing the impact of mean and deviatoric stress on viscosity in wide range of applied stress. The presence of non-aqueous fluids (oil or CO2) appears to have significantly weaker impact on the creep deformation compared to aqueous fluids (deionized water and water with dissolved CO2). Finally, the drainage condition appears to be essential. If the mass of pore fluid inside the specimen remains constant throughout the experiment (undrained condition), the microcracking results in phenomena similar to dilatant hardening of the material observed at constant applied state of stress. This effect might be qualitatively similar to the ones occurring in the off-fault plasticity zones and provide the fault stabilization mechanism.

How to cite: Bondarenko, N., Makhnenko, R., and Podladchikov, Y.: Role of pore fluids in time-dependent deformation and microcracking of rock under high deviatoric stress, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19660, https://doi.org/10.5194/egusphere-egu24-19660, 2024.

EGU24-22551 | Orals | GD7.2 | Highlight

Thermal softening in the ductile and brittle lithosphere 

Dániel Kiss

Plate tectonics on Earth is characterized by a largely localized distribution of lithospheric strain, both in the ductile and in the brittle regimes. While deformation in brittle or elastic materials is generally localized, in homogenous ductile or viscous materials some strain localization requires a softening mechanism. Here we will focus on thermal softening, a consequence of the conversion of mechanical work into heat (i.e. shear heating) and the temperature dependence of rock viscosities.
First, I briefly list the fundamental features of ductile shear zone evolution due to thermal softening driven by steady-state background deformation. (1) After an initial transient period, the maximum temperature and stress in the shear zone converges to a (quasi-)constant value (temperature increase and stress drop). (2) The steady-state maximum temperature can be estimated using a scaling law. (3) With ongoing deformation, the high-temperature zone and consequently the shear zone widen, which indicates that shear zone width is controlled by conduction time scales.
Second, I demonstrate that thermal softening is a feasible mechanism of lithospheric scale ductile strain localization by comparing geological observations and model results of subduction initiation, ophiolite emplacement, and high-temperature metamorphic nappes.
Finally, I will investigate the possible occurrence and importance of thermal softening in the brittle, elastoplastic domain, often associated with much shorter time scales such as slow slip events and earthquakes. Data from rock deformation experiments indicate that steady-state friction angle becomes primarily velocity-dependent at high slip rates, which is consistent with thermal softening. Numerical models of Maxwell visco-elastic deformation show that thermal softening can be an efficient mechanism of limiting elastic stress build-up, often resulting in a rapid stress release, often referred to as thermal runaway.  

How to cite: Kiss, D.: Thermal softening in the ductile and brittle lithosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22551, https://doi.org/10.5194/egusphere-egu24-22551, 2024.

EGU24-22558 | ECS | Posters on site | GD7.2 | Highlight

Influence of intracrystalline deformation on chemical diffusion in garnet around coesite inclusions 

Cindy Luisier, Lucie Tajcmanova, Thibault Duretz, Larissa Lenz Lenz, and Liudmila Khakimova

Coesite inclusions in garnets are emblematic observations, typical of Ultra-High-Pressure (UHP) rocks.  While small inclusions may fully preserve coesite, sufficiently large inclusions undergo partial transition of coesite to quartz. Here, we focus on samples from UHP rocks from Dora Maira Massif (Western Alps). Classical petrographic analysis indeed reveals the coexistence of quartz and coesite as well as deformation of the surrounding garnet (radial fractures). In addition, microprobe analysis further shows chemical zoning in garnet around partially transformed inclusions. This observation suggests a link between chemical zoning and deformation related to the phase transition. Such an observation provides a unique opportunity to investigate the relation between multi-component diffusion and garnet deformation using both microprobe analysis and quantitative modelling.

How to cite: Luisier, C., Tajcmanova, L., Duretz, T., Lenz, L. L., and Khakimova, L.: Influence of intracrystalline deformation on chemical diffusion in garnet around coesite inclusions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22558, https://doi.org/10.5194/egusphere-egu24-22558, 2024.

EGU24-22560 | ECS | Orals | GD7.2 | Highlight

Application of reaction front propagation modelling to amphibolite-facies plagioclase hydration: an example from the Bergen arcs, Norway 

Jo Moore, Sandra Piazolo, Andreas Beinlich, Håkon Austrheim, and Andrew Putnis

Fluid inflitration along brittle presursors is commonly with associated with hydration and deformation of the host rock. In many cases the relative timing of fracturing, fluid infiltration, reaction, and deformation is unclear, making it difficult to disentangle the relative importance of processes that facilitate advancement of the hydration front. Here we present the transition from an anhydrous and relatively undeformed precursor rock into a highly deformed and hydrated plagioclase-rich rock. The studied outcrop preserves both (1) the interface between the anhydrous granulite-facies parent lithology and a statically hydrated amphibolite-facies rock, and (2) a transition from statically hydrated amphibolite to the sheared amphibolite-facies lithologies. Detailed petrography, quantitative mineral chemistry and bulk rock analyses have been applied to investigate compositional variations and assemblage microstructure across both interfaces. Here, we produce hydro-chemical numerical models based on local equilibrium thermodynamics in an attempt to reproduce the characteristics of the hydration and deformation interfaces. Here, we present a comparison between the observed characteristics of the hydration front and those produced by modelling of the reaction front propagation.

How to cite: Moore, J., Piazolo, S., Beinlich, A., Austrheim, H., and Putnis, A.: Application of reaction front propagation modelling to amphibolite-facies plagioclase hydration: an example from the Bergen arcs, Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22560, https://doi.org/10.5194/egusphere-egu24-22560, 2024.

GMPV5 – Building economic ore deposits

EGU24-127 | ECS | Orals | GMPV5.1

Simultaneous precipitation of U4+ and U6+ in quartz-pebble conglomerate in the Singhbhum Craton, India. 

Smruti Prakash Mallick, Amit Mondal, and Kamal Lochan Pruseth
  • Uranium is generally mobilized in solutions in U6+-complexes and gets precipitated as compounds containing the U4+ ion. Here we report hydrothermal remobilization of U, and the simultaneous precipitation of U6+ and U4+ in the Paleoproterozoic quartz-pebble conglomerate (QPC) from the Mankarchua basin, Singhbhum Craton, India. Uranium occurs associated with vein pyrite in the basal QPC of the Mankarchua basin, suggesting a clear hydrothermal origin of the mineralization. The pyrites occur linearly in veins and are replaced U-bearing minerals. Detrital monazites are the source of U. Newly formed fine-grained U-free monazites are observed along with crandallite series minerals (Ca,Ba,Sr,Pb)Al3(PO3.5(OH)0.5)(OH)6., suggesting alteration of detrital monazite by moderately oxidising acidic fluids. The remobilized U precipitates when it encounters pyrite and apatite. Brannerite (UTi2O6, containing U4+) forms concomitantly with the oxidation of pyrite, while autunite (Ca(UO₂)₂(PO₄)₂·10–12H₂O, containing U6+) forms by replacement of apatite. Thus, detrital or hydrothermal apatite enriched zones with or without pyrite may serve as U-traps for potential mineralization.

How to cite: Mallick, S. P., Mondal, A., and Lochan Pruseth, K.: Simultaneous precipitation of U4+ and U6+ in quartz-pebble conglomerate in the Singhbhum Craton, India., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-127, https://doi.org/10.5194/egusphere-egu24-127, 2024.

EGU24-514 | ECS | Posters on site | GMPV5.1

Textural studies of Magnetite from the rocks of Beldih, Purulia, West Bengal  

Reeya Ghosh and Manoj Kumar Ozha

Kiruna-type Fe-oxide-apatite (IOA) mineralization is a potential source of phosphorous, iron rare earth elements (REEs), and other elements (Ag, Cr, Co, and U) of economic importance. In such deposits, textures associated with ore minerals provide important insights that can aid in characterizing the primary/secondary phases vis-à-vis the process of mineralization. Accordingly, apatite-magnetite veins (associated with calcite-bearing ultramafic rocks) from the Beldih area (South Purulia Shear Zone) of Eastern India were studied to appraise the formation of Fe-oxides and sulfide minerals hosted within these rocks. The present work integrates preliminary Petrological studies (both under microscope and Backscattered electron: BSE imaging) to comprehend the texture/s of Fe-Ti oxides and associated sulfides. The major/dominant phases in the samples comprise magnetite and ilmenite (among the Fe-Ti oxides) and pyrrhotite, pyrite, chalcopyrite, sphalerite, cobaltite, and gersdorffite (as sulfide phases). These rocks in the study area preserve varied textural assemblages/associations of magnetite: (a) Magnetite (Mag1) in the samples is coarse-grained with euhedral/polygonal grain boundaries, in which larger grains preserve two different sets of fine lamellae of ilmenite (in addition to individual grains) exhibiting both Trellis intergrowth and Widmanstatten texture; and (b) medium-sized, discrete grains of magnetite (Mag2) and ilmenite at the boundary of large pyrrhotite grains (associated with pyrite and chalcopyrite). Both these textural types include euhedral grains of apatite embedded on clusters of calcite, associated with minor REEs (allanite and monazite) and silicate phases (amphibole, biotite, muscovite, and titanite). Pyrite grains (exhibiting sharp boundary) in the rock are found both as inclusions and at the grain boundary of large (anhedral) pyrrhotite grains, indicating possible alteration of pyrite to form pyrrhotite. Inclusions of gersdorffite are also seen within a few pyrrhotite grains. Thus, from the afore-discussed textural assemblage of magnetite (Mag1), it stands to reason that high-fO2 environment prevailed during its formation and the possible difference of pressure in the solid solution between magnetite and ilmenite. The formation of Fe-oxides, calcite, apatite, and silicates is consistent with the primary crystallization of these minerals possibly from a silicate melt (by liquid immiscibility process) or from a high-T magmatic-hydrothermal fluid. Subsequently, the formation of secondary discrete magnetite (Mag2) and associated ilmenite grains (in addition to various sulfide phases), indicates possible ingress of a hydrothermal fluid into the system.

How to cite: Ghosh, R. and Kumar Ozha, M.: Textural studies of Magnetite from the rocks of Beldih, Purulia, West Bengal , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-514, https://doi.org/10.5194/egusphere-egu24-514, 2024.

The Sangan mining district consists of 14 iron ore deposits at the contact of Eocene granitoids to Mesozoic sedimentary rocks. Syenite, syenogranite and granite represent the fertile Sarnowsar intrusion and monzogranite to syenogranite barren Sarkhar and Bermani intrusions. LA-ICP-MS U-Pb zircon ages of fertile syenogranite samples are between 39.6 ± 0.7 and 39.1 ± 0.4 Ma corresponding to lithospheric thinning by Eocene flare-up magmatism. Barren Sarkhar and Bermani intrusions (monzogranites at 41.7 ± 0.6 and 41.9 ± 0.3 Ma; syenogranites between 37.4 ± 1.8 and 37.9 ± 1.7 Ma were emplaced contemporaneous with flare-up magmatism.

Plots of Nb vs. Ta, Y vs. Yb/Sm and Y vs. Ce/Ce* classify studied zircons as granitoid-type as parental magma. Uniformly high Hf contents of zircons indicate crystallization from a more evolved felsic magma, especially the Sarkhar and Bermani intrusions. In the U/Yb versus Hf and U versus Yb discrimination diagrams, all data plot in the continental-series and are clearly distinguishable from ocean crust zircons. In the U/Yb versus Nb/Yb diagram, both the whole-rock and zircon compositions show the characteristics of a magmatic-arc array. The Nb content of arc magmas is depleted relative to within-plate settings. As such, arc zircons possess lower Nb/Hf and higher Th/Nb ratios with a similar degree of magmatic fractionation. Bivariate discrimination diagrams such as Th/U versus Nb/Hf and Th/Nb versus Hf/Th indicate that most zircons plot in the orogenic field, signifying a magmatic arc or orogenic setting and a calc-alkaline parent magma. Fertile intrusions are characterized by a higher zircon Eu (>0.3) and Ce (>100) anomalies, 10,000*(Eu/Eu*)/Y (>1), (Ce/Nd)/Y (>0.001), and slightly lower Dy/Yb ratios (0.21 to 0.38) than zircons in barren intrusions with Dy/Yb ratios (0.2 to 0.51) and lower Eu and Ce anomalies. The chondrite normalized zircon Eu/Eu* ratio correlates with whole rock La/Yb and has been used to estimate the crustal thickness. Our results reveal that fertile Sarnowsar granitoids formed in thicker crust (48 to 66 km) than barren Sarkhar and Bermani (25 to 38 km) granitoids. As the granitoids formed in adjacent areas, these differences in crustal thickness imply either a heterogeneously composed crust, or the iuxaposition of units across a major fault, or hitherto unknown complications with the method. The zircon/rock partition coefficients of REEs, and Y, Nb, Ta, Th, and U contents indicate that the trace element patterns of the studied granitoids are controlled by the liquid composition at the magmatic crystallization. Compared to Sarkhar and Bermani magmatism, Sarnowsar magmatism has a higher temperature (736 to 915 °C), higher zircon/rock partition coefficient of REEs, Y and Th (up to 2770 for Zr), and it was formed in higher oxidant conditions (△FMQ values between -0.06 to 17.01). This indicates that the fertile intrusions are interpreted to indicate extremely high magmatic water content and oxidized like fertile porphyry systems. We suggest that oxidized and I-type magmas are more favorable to porphyry-skarn mineralization under arc tectonic settings. Such a conclusion could be used in regional exploration for porphyry-skarn mineralizations in the Cenozoic arc-related magmatism of Iran and elsewhere.

How to cite: Ghasemi Siani, M. and Neubauer, F.: Discrimination of fertile and barren skarn-related magmatism from Sangan Fe Skarn, NE Iran: Constrains from whole-rock geochemistry, zircon chemistry and crustal thickness, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-661, https://doi.org/10.5194/egusphere-egu24-661, 2024.

Especially in the context of renewable energy, vanadium (V) is an important component of energy storage technology. Gabbroic rocks in crustal environments may host a considerable amount of V-bearing minerals such as magnetite, and ilmenite. This study focuses on primary V occurrences in Precambrian-Cambrian aged meta-gabbroic rocks of the Alaşehir-Manisa area in the central part of the Menderes Massif (Türkiye). The primary purpose of the study is twofold; 1) to determine the V potentiality of meta-gabbro and 2) to reveal the enrichment mechanism by determining the mineralogical and geochemical properties of gabbroic formations. The meta-gabbroic rocks in the study area can be divided into three subgroups based on the size distribution (fine, medium, and coarse) of the minerals. The ore-bearing minerals observed in the meta-gabbroic rocks are construed by magnetite, ilmenite, titanomagnetite, rutile, pyrite, and hematite. The high-grade metamorphism of Menderes Massif progressively affected the gabbroic rocks resulting in the partial and complete transition of ilmenite minerals to rutile. However, the effect of metamorphism gradually decreases from outward to inward zones of the intrusion allowing an intact vanadiferous ilmenite-rich core in the entire gabbro body. 

The V enrichments are both hosted by oxide and sulphide-bearing phases. While the oxide phases are constituted by ilmenite and Ti-magnetite exsolutions, the sulphide minerals are pyrite and minor chalcopyrite. The V content of the studied meta-gabbro range from 281 to 628 ppm, with an average of 514 ppm. Contents of SiO2, Al2O3, Fe2O3, MgO, TiO2, and P2O5 are between 68.8-38.9%, 7.93-15.4%, 6.87-17.8%, 3.21-8.86%, 1.24-5.64%, 0.19-1.13%, respectively. V shows moderate to strong correlation with Ti, Zn, and Ga (R2= 0.51, 0.86, and 0.87, respectively) and there is a lack of correlation with Fe, Ni, and Cu indicating V3+ ion substituted Fe3+ in magnetite and Ti3+ in ilmenite. The other meta-gabbro intrusions of Menderes Massif generally lacked Ti-V enrichments, therefore Alaşehir meta-gabbro intrusion may gain economic importance in case of a tighter supply trend of these critical elements.

Keywords: Vanadiferous gabbro; Magnetite; Ilmenite; Menderes Massif; Alaşehir-Manisa (Türkiye)

How to cite: Sutcu, N. M., Doner, Z., Unluer, A. T., and Kumral, M.: Vanadium Enrichments of Meta-Gabbroic Rocks in central part of the Menderes Massif (Türkiye): The Incremental Effect of Magmatism and Metamorphism in Highly Siderophile Environments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-716, https://doi.org/10.5194/egusphere-egu24-716, 2024.

EGU24-1579 | Orals | GMPV5.1

Mineralogical characteristics of a Fe-Ni-Co-Cu sulphide mineralization in Sebuku Island, Indonesia. 

Antje Fuchs, Guillaume Jacques, Torsten Graupner, Yoseph Swamidharma, Andhi Cahyadi, Yudhi Krisnanto, Ernowo Ernowo, Arifudin Idrus, and Agata Vanessa

Critical raw materials (e.g., Co, Ni, Pt, Sc…) are very important resources for high technology applications (e.g., renewable energies, modern electronic devices, e-mobility, medical). Most of these minor and trace elements are produced as by-products of base metal mining. Magmatic Ni-Cu sulphide ore deposits are of great economic relevance worldwide. The BMBF-funded project “StratOre” (FKZ 033R278) aims to study the high-tech element potential of newly found sulphide deposits in ophiolite sequences in Indonesia, a country, which is well known for its large number of mineral deposits. Here we present the first results of our study addressing the nature of the Sebuku Island Fe-Ni-Co-Cu sulphide ore and the distribution of base and precious metals in different minerals.

Sebuku Island (SE-Kalimantan) is part of the Cretaceous accretionary Meratus collision complex and represents an obducted ophiolite at the convergent boundary of Sundaland in the NW and the compressing Paternoster microcontinent in the SE. This ophiolite complex consists of mafic-ultramafic layers and rocks of the upper mantle of Permian to Jurassic age. Cretaceous intrusions, meta-sediments and mafic-intermediate intrusions are overlain by Tertiary and Quaternary sediments. Serpentinization started prior to obduction and became affected by cretaceous magmatism and alteration. One of the Early Cretaceous intrusions is supposed to represent a mantle wedge and is marked by high-temperature serpentine (Sulistyohariyanto and Soesilo, 2017, Cahyadi et al., 2017, Imani et al., 2020).

Massive Fe-Ni laterite (mined since 2000 by PT SILO) is overlying a recently observed Fe-Ni-Co-Cu sulphide mineralization, which is hosted by high-temperature serpentinite in the cumulus zone of the ultramafic ophiolite complex. Our sample material is taken from 14 drill cores within depths of 22 m to 109 m. The studied mineralization occurs as massive, erratic and disseminated sulphides. Formation of the ore body is probably resulted from subsequent magmatic and hydrothermal processes. The base metal sulphide-ore mineralogy is represented mainly by pentlandite, pyrrhotite, pyrite, chalcopyrite and cobaltite; a large number of further sulphides and arsenides are observed as well. We highlight the extraordinary enrichment of Co in Fe-S, Fe-Ni-S and Ni-S minerals, as well as the extraordinary enrichment of Ni in pyrrhotite and pyrite. Platinum-group elements are not enriched in any of the ore types.

How to cite: Fuchs, A., Jacques, G., Graupner, T., Swamidharma, Y., Cahyadi, A., Krisnanto, Y., Ernowo, E., Idrus, A., and Vanessa, A.: Mineralogical characteristics of a Fe-Ni-Co-Cu sulphide mineralization in Sebuku Island, Indonesia., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1579, https://doi.org/10.5194/egusphere-egu24-1579, 2024.

EGU24-1668 | ECS | Orals | GMPV5.1

Quantitative mineralogy and lithium distribution in the upper part of the Beauvoir granite 

Steven Kahou, Michel Cathelineau, and Marie-Christine Boiron

The albite-lepidolite-topaz granite of Beauvoir is the last intrusion in a peraluminous granitic complex of Variscan age composed of three successively emplaced units: the hidden granite of La Bosse, the two-micas granite of Colettes, and the Beauvoir granite consisting of 3 units B1 to B3. Compared to similar Li-F-rich igneous bodies, the Beauvoir granite is highly enriched in Sn (200-1400 ppm), Ta (20-400 ppm) and Be (20-300 ppm). The B1 unit is composed of abundant albite and lepidolite laths forming a framework filled with globular quartz, K-feldspar, and rare crystals of topaz, Li-phosphates and Sn-Nb-Ta oxides. This work presents a quantitative mineralogical study of the Beauvoir granite (B1 unit) and detailed textural and chemical characterization of the Li-bearing micas from the cores from the PER and EMILI drilling campaigns. The first approcah of this work consisted in estimating the proportion of minerals, and thus determine their abundance by comparing estimates from in situ thin section mapping from micro-XRF and the calculation of mineral phase proportion from whole rock geochemistry on drill cores. The main trend is a "mix", for the fresh rocks, between an albite pole (> 35 %), and a quartz (~25 %) - lepidolite (~15-25 %) pole. The micas are represented, in the fresh facies, by trioctahedral lepidolite while the altered facies shows i) dioctahedral muscovite replacing the feldspars and lepidolite, and ii) lepidolite replaced partially or totallly by muscovite. Trace element composition of the lepidolite show high Li content with average 28000 ppm for lepidolite from the fresh facies and 24000 ppm for those from the altered facies. Compared to lepidolite, muscovite is not a Li-bearing but Sn-rich mineral. Our study shows that hydrothermal greisen alteration has almost no impact on the lithium content of the lepidolite but decrease the population of the lepidolite. The results obtained, combining to drilling data, will lead to a mineralogical model block of the Beauvoir quarry and better understand the magmatic-hydrothermal evolution of the deposit.

How to cite: Kahou, S., Cathelineau, M., and Boiron, M.-C.: Quantitative mineralogy and lithium distribution in the upper part of the Beauvoir granite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1668, https://doi.org/10.5194/egusphere-egu24-1668, 2024.

Beryllium (Be) is among the most important rare metals in the world and is used to produce complex alloys and ceramics critical for the telecommunication, aerospace, medical, and defense industries. Global Be supplies are primarily obtained from bertrandite [Be4Si2O7(OH)2] mined from the Spor Mountain deposit, Utah, U.S.A, in a region dominated by Miocene-Oligocene alkaline rhyolitic tuffs and lavas. Ore occurs primarily in lithic-rich, phreatomagmatic, base-surge deposits containing carbonate debris in a basal tuff. The tuff is part of a package of rare-metal-rich rhyolite lava flows, pyroclastic deposits, and discordant fluorite-bearing pipes. Pb-Nd-Sr isotope and trace element data, together with mineral associations (1) map the flux of Be, Li, F, REEs, and U in the magmatic-to-hydrothermal system, (2) reveal the role of fluid-rock interactions and recrystallization processes in concentrating metals, and (3) place constraints on timescales of bertrandite-fluorite-opal precipitation. Geochemical models indicate that high-grade ore formed under pH-buffered conditions when F-rich fluids leached metals from glassy tuff, reacted with carbonate xenoliths, and deposited Be and other rare metals in complexly layered nodules composed of Mn-oxide, Li-smectite, calcite, fluorite, opal, and bertrandite. U-Pb age dates and coupled 29-element analyses of discrete opal layers by the SHRIMP-RG method show an almost continuous record of opal deposition. The results establish timescales of high-grade opaline ore formation with major influxes of Be, F, REEs, and Li from ~16 Ma to 10 Ma and of Mn and U at <6 Ma. The interplay of periodic infusions of Be-rich magma, ash, and gas with shallow-circulating, heated fluids led to large-scale remobilization of Be and concentration of high-grade Be ore in the tuff. Fluid-rock interaction and recrystallization had limited effects on other rare elements (Li, REEs) in tuff and rhyolite. These new data shed light on the magnitude of the metallogenic processes and magmatic-to-hydrothermal system required to form a world-class volcanic-hosted beryllium deposit. Additional Be occurrences in Utah, Nevada, New Mexico, and Texas highlight the potential for additional resources of volcanic-related Be and co-product Li-F-REEs in the western United States and globally.

How to cite: Foley, N. K., Ayuso, R. A., Jackson, J. C., Indela, R., and Bickerstaff, D. P.: Volcanic-hosted Be-(Li-F-REEs-U) mineralization at the world-class Spor Mountain deposit, Utah, USA: Insights into source rocks, geochemical signatures, and macro-to-microscale concentration processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2161, https://doi.org/10.5194/egusphere-egu24-2161, 2024.

EGU24-2550 | Posters virtual | GMPV5.1

Petrographical And Geochemical Characteristics of The Zeolitic Akdere Tuff (Demirci, Western Anatolia) 

Nimet Coskun, Bala Ekinci Sans, and Fahri Esenli

One of the important Neogene basins of Western Anatolia (Turkey) is the NE-SW trending Demirci Basin. The Miocene sequence, consisting of approximately 1000 m thick clastics and volcanics, is unconformably located on the Paleozoic-Menderes Metamorphic Massif (gneiss, schist, marble). The lower part of Miocene sequence contains block–pebble–sand size of clastics. They are continued upward with sandstone, claystone, marl, limestone, mudstone, and shale lithologies laterally transition with pyroclastic rocks at the top. Pyroclastic rocks (Akdere Tuff) are covered by a lacustrine unit consisted of sandstone, mudstone, bituminous shale limestone and tuffite. Akdere tuff, with rhyodacite character, light beige-gray-green color, 10-70 m thickness, is highly zeolitized (heulandite-clinoptilolite). At the bottom of the tuff unit, there are 25-30 m thick, fine-coarse grained, pumiceous, glassy, and glassy-crystalline ash tuffs containing rare lithic fragments. These are overlain by 20-25 m thick glassy dust-ash tuffs. At the top there is a 5 m thick pumicite level with lateral transitions. Zeolitic Akdere tuff petrographically contains small and rare amounts of mineral and lithic fragments in a matrix consisting of glass fragments with concave, sharp straight or curvilinear edges and rarely pumice fragments. Mineral fragments (2-25 %) are feldspars (albite-oligoclase type of plagioclases and K-feldspar) quartz, biotite, muscovite, amphibole, and opaque minerals. According to the X-ray diffraction (XRD) results, the mineralogical composition throughout the samples is 'heulandite-clinoptilolite (hul-cpt) + opal-CT + opal-A + smectite + illite-mica + quartz + feldspar’. The heulandite-clinoptilolite ratio in the samples examined varies between 0-95 percent. The glassy groundmass of the tuffs is almost completely zeolitized. Heulandite-clinoptilolite grains, formed by the transformation of volcanic glass, are in the form of monoclinic plates, shorter than 15 µm according to the results obtained from scanning electrone microscope (SEM) studies. SEM studies also showed that devitrification of volcanic glass formed firstly a gel-like phase before the formation of heulandites-clinoptilolites. Cationic values ​​(Si/Al and Na+K/Ca+Mg ratios) taken from heulandite-clinoptilolite grains by Energy dispersive X-ray spectroscopy (SEM-EDX) gave the composition of both heulandite and clinoptilolite. However, thermal stability results indicated clinoptilolite, and clinoptilolite did not deteriorate at 550 oC. Whole-rock chemical values ​​and some chemical parameters of the zeolitic Akdere Tuff are as follows. SiO2: 68.45-76.50 %, Al2O3: 10.10-14.30 %, SİO2/Al2O3: 4.82-7.19, K2O: 1.34-4.46 %, Na2O: 0.13-2.92 %, CaO: 0.70-2.92 %, MgO: 0.59-4.85 %, Fe2O3: 0.68-1.82 % and (Na2O+K2O)/(CaO+MgO): 0.33-5.63. The chemical composition of zeolitized tuffs in the Demirci region is a function of selectivity of zeolite minerals additionally to the primary composition of the volcanism. Tuff samples containing high amounts of hul/cpt have higher values ​​for CaO, H2O, and most trace elements and REEs than the samples containing little or no zeolite.

 

Key words: Clinoptilolite, Demirci, Geochemistry, Turkey, Zeolitization.

 

How to cite: Coskun, N., Ekinci Sans, B., and Esenli, F.: Petrographical And Geochemical Characteristics of The Zeolitic Akdere Tuff (Demirci, Western Anatolia), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2550, https://doi.org/10.5194/egusphere-egu24-2550, 2024.

The granites associated with large-scale W and Sn deposits generally have high concentrations of U, Th, and K, including but not limited to the Cornubian Batholith in Southwest England, the Krušné hory/Erzgebirge Batholith in Central Europe, the Sardinian Batholith in Italy, and the Gejiu Batholith and the Qianlishan granitic complex in South China. These granites can be classified as high heat producing (HHP) granites (>5 μW m-3) because of high radiogenic heat production. However, how long radiogenic heat can prolong the suprasolidus lifetime of magmas and whether radiogenic heat exerts an influence on later W and Sn mineralization is poorly understood.

To answer these questions, finite element numerical modeling was established to link magma cooling by heat conduction with diffusion of W, Sn, and H2O from silicate melts to coexisting aqueous fluids before the solidus is reached. The magma size (vertical thickness of 4–5 km and horizontal length of 20 km) is constrained by the granites associated with large-scale W and Sn deposits. The modeling results suggest that the suprasolidus lifetimes of HHP magmas are positively correlated with the heat production and magma thickness and negatively correlated with the solidus temperatures and the thermal conductivity of host rocks. Average radiogenic heat of 5–10 μW m-3, together with decreased solidus temperatures due to magmatic differentiation and a moderate thermal conductivity of host rocks, can prolong the suprasolidus lifetime of HHP magmas by 49–427 ka (1 Ma = 1000 ka), corresponding to 11–85 % of the suprasolidus lifetime of equally sized magmas with normal radiogenic heat (2 μW m-3). From the available gravity modeling data, over half of the granites associated with large-scale W and Sn deposits are at least 1 km thicker than the values calculated from the empirical power–law equation, and the modeling results indicate that an increase of 500–1000 m in magma thickness prolongs the suprasolidus lifetimes of HHP magmas (5 μW m-3) by 50–74 %. During magma cooling before solidus is reached, the diffusion of W and Sn is at least several orders of magnitude slower than that of H2O in hydrous melts; thus, the equilibrium partitioning of these two metals between silicate melts and coexisting aqueous fluids is not reached, and the metal diffusion from melts is a rate-limiting step. The prolongation of the suprasolidus lifetimes by radiogenic heat and decreased solidus temperatures can allow extraction of 17–95 % more W and Sn from silicate melts before the solidus is reached and increase the possibility of producing W and Sn mineralization at later stages. Therefore, the coexistence of HHP granites and large-scale W and Sn deposits is not accidental.

How to cite: Liu, X.-C. and Zhang, D.-H.: The links between high heat producing granites and large-scale W-Sn deposits: insight from numerical modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2829, https://doi.org/10.5194/egusphere-egu24-2829, 2024.

High-grade hematite mineralization is widely developed in banded iron formations (BIFs) worldwide. However, in the North China craton where Neoarchean-Paleoproterozoic BIFs are abundant, economic high-grade hematite ores are scarce. High-grade hematite ores hosted in the Paleoproterozoic Yuanjiacun BIFs represent the largest occurrence of this type of ore in the North China craton. It was once viewed that the lack of high-grade hematite ores in the North China was due to the lack of prolonged epigenetic weathering-leaching conditions, but that could not explain the fault-controlled characteristics of high-grade hematite orebodies in Yuanjiacun. On the basis of field contact relationship, petrological and mineralogy analysis, the in-situ U-Pb dating of monazite and xenotime and the fluid inclusion analysis of quartz intergown with hematite was both carried out. The results show that, the timing of high-grade hematite mineralization was at 1.41 to 1.34 Ga, revealing that the deposition of hematite was probably related to tectonic extension in the North China craton related to the breakup of the Columbia/Nuna supercontinent. Petrography and microthermometry of primary fluid inclusion assemblages indicate that the high-grade hematite ore formed from hot (313°–370°C), CO2-rich, and highly saline (about 20 wt % NaCl equiv) hydrothermal fluids. These fluids channeled along faults, which concentrated iron through interaction with the BIFs—a process similar to typical hematite mineralization elsewhere. By comparing to the typical iron deposits worldwide, and combining with the views of the predecessors, we argue that the high-grade hematite ores formed in lower metamorphic-grade BIFs at shallower depths than magnetite mineralization and was largely eroded during later exhumation and uplift of the craton. The determination of ore genesis of the Yuanjiacun high-grade hematite ores  is of theoretical and practical significance to enriching the mineralization process of high-grade iron ores and futher prospecting exploration for high-grade iron ores in the Yuanjiacun area.

How to cite: Meng, J. and Li, L.: Monazite and xenotime U-Pb geochronology constraints on the genesis of the Paleoproterozoic Yuanjiacun banded iron formation-hosted high-grade hematite ores of the North China craton, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3013, https://doi.org/10.5194/egusphere-egu24-3013, 2024.

EGU24-3046 | Orals | GMPV5.1

Abovyan – an enigmatic Kiruna-type apatite-magnetite deposit in Armenia 

Nikolai Nekrylov, Samvel Hovakimyan, Robert Moritz, Christian Bergemann, Karen Hambaryan, and Khachatur Meliksetian

The Abovyan deposit in Armenia represents a unique example of relatively young, Late Miocene age Kiruna-type apatite-magnetite mineralization in the region. Initially identified in 1947 by a team of Armenian geologists, based on the well-pronounced magnetic anomaly, it remains largely obscure outside the confines of Soviet-era scholarly literature. This deposit resides within a magmatic formation predominantly of intermediate composition, comprising andesites and dacites, and characterized by disseminated and massive magnetite ores and transitional varieties between them. The deposit is fully covered by several dozens of meters of younger, Pliocene-Quaternary volcanic rocks, so the samples for our study were collected from drill cores. These specimens, encompassing both host rocks and ores, retain critical insights into the processes governing ore segregation and accumulation, despite having a large influence of the autometasomatic alteration. The young age (~6-7 Ma, K-Ar, Sarukhanyan, 1969) and, consequently, the absence of later metamorphic events in the area is the main advantage of the Abovyan deposit over the majority of Kiruna-type deposits around the world in terms of preservation of the initial textures and other mineralogical and petrological features. Several generations of the magnetite-apatite ores could be clearly distinguished in the ores, which include (1) magnetite melt-like droplets in the host-rocks, (2) massive magnetite apatite ores, (3) magnetite-hosted breccias of the altered host-rocks and (4) several generations of late hydrothermal veins. Notably, the apatite within these ores exhibits a remarkable enrichment in light rare earth elements (REEs), reaching concentrations as high as 4 wt.%. This level of enrichment is notably higher than that observed in other Kiruna-type deposits (Frietsch, Perdahl, 1995) and is accompanied by the other critical metals’ mineralization (e.g., Th). Ongoing research on the geochemistry and geochronology of the Abovyan deposit may be a key to understanding the formation of the Kiruna-type deposits and their REE potential, in particular.

This study was funded by the Science Committee of RA (Research projects №23PostDoc-1E001 and  № 22IRF‐08), and by the Swiss National Science Foundation (grant 200021_188714).

Frietsch, R., Perdahl, J. A., 1995. Rare earth elements in apatite and magnetite in Kiruna-type iron ores and some other iron ore types. Ore Geology Reviews, 9, 6, 489-510.

Sarukhanyan, L.B., 1969. Some questions about the genesis of the Abovyan apatite-magnetite deposit. Proceedings of the Armenian SSR Academy of Science, Earth Sciences, 3, 40-49 (in Russian)

How to cite: Nekrylov, N., Hovakimyan, S., Moritz, R., Bergemann, C., Hambaryan, K., and Meliksetian, K.: Abovyan – an enigmatic Kiruna-type apatite-magnetite deposit in Armenia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3046, https://doi.org/10.5194/egusphere-egu24-3046, 2024.

EGU24-3657 | ECS | Orals | GMPV5.1

The Zn-Pb(-Cu-Fe) mineralization in the northern Sila Massif (Calabria, southern Italy): Genetic constrains from trace element concentrations in sphalerite 

Antonio Ciccolella, Vincenzo Festa, Giovanni Ruggieri, Emanuela Schingaro, Fabrizio Tursi, Gennaro Ventruti, and Rosa Anna Fregola

The occurrence of Zn-Pb(-Cu-Fe) mineralization in the northern Sila Massif (Calabria), primarily in Longobucco (LGB) and Fonte Argentila (FAR) areas, is not a novelty (e.g., Fregola et al., 2023). However, the genesis of this mineralization and its relation to the geological evolution of the Sila Massif are still unknown. These issues are addressed in the present study. Detailed mineralogical and geochemical analyses were carried out on ore-samples collected from mineralized faulted bodies within the granodiorite of the Sila batholith. The mineral association, common to both areas, consists of sphalerite (Sp), as main ore-mineral, galena (Gn), quartz (Qz) and calcite (Cal). Samples from the FAR site also contain chalcopyrite (Ccp), pyrite (Py), and fluorite (Flr). Mineral composition and microstructures were characterized using SEM, EPMA and m-Raman spectroscopy techniques. In addition, trace element distribution in sphalerite and chalcopyrite were determined with LA-ICP-MS. The sphalerite is Fe-poor (Fe up to 11.3 wt%; 0.21 mol% FeS) and shows the associated color and chemical zonings mainly due to variations in Fe concentrations. The following trace elements have been identified in sphalerite: Mn, Co, Cu, Ga, Ge, Ag, Cd, In, Sn, Sb, Hg, Tl, Pb, Bi. The reconstructed paragenetic sequence comprises five growth stages for both areas. During stage-1, precipitation of massive, light-colored and Fe-poorer Sp1 occurred, whereas in stage-2 a darker, Fe-richer Sp2 formed in association with euhedral Qz1. The latter shows color and chemical zonings related to variations in Al, Na, K, Ca content. Fracturing characterized stage-3, along with precipitation of massive Cal (in LGB) and Flr (in FAR). The calcite in LGB hosts synchysite, with grain sizes between 20 and 60 µm, and ΣREE (Ce, La, Y, Nd, Sm, Pr, Gd, Dy) ranging from 2.40 to 42.6 wt%. Stage-4 was characterized by diffuse recrystallization of colorless Sp3 and Qz2. During the stage-5 an almost pure Gn, Ccp and Py formed at the expense of the previous minerals. Formation temperatures ranging between 150 and 200°C were derived for Sp1 and Sp2 using the GGIMFis sphalerite geothermometer (Frenzel et al., 2016). These predicted values will be compared with those obtained from ongoing fluid inclusion analyses. Anyway, such low formation temperatures are also supported by the Zn/Cd (195–267), Ga/In (190–596), and In/Ge (0.24–1.20) average ratios in the sphalerite, indicative of a low-temperature ore-forming fluid. Our mineralogical and geochemical results are comparable with those of either the vein-type or the MVT deposits, although the examined mineralization in the northern Sila Massif occur in a different geological context and registers slightly higher temperatures than those typical of the MVT deposits (that is, 100–150°C).

How to cite: Ciccolella, A., Festa, V., Ruggieri, G., Schingaro, E., Tursi, F., Ventruti, G., and Fregola, R. A.: The Zn-Pb(-Cu-Fe) mineralization in the northern Sila Massif (Calabria, southern Italy): Genetic constrains from trace element concentrations in sphalerite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3657, https://doi.org/10.5194/egusphere-egu24-3657, 2024.

EGU24-4062 | Posters on site | GMPV5.1

Anoxic Ocean inhibited the formation of porphyry copper deposits 

Min Sun, Xiangsong Wang, and Guochun Zhao

Abundant porphyry copper deposits (PCDs) are distributed in the Central Asian Orogenic Belt (CAOB), but the majority are concentrated in the Circum-Balkhash and Tuva-Mongolia micro-continents (BM), limited deposits have been identified in the Circum Junggar Collage (CJC), the mechanisms that drive uneven distributions of PCDs remain controversial. We provide a compilation of published elemental and isotopic data of magmatic rocks from the CAOB, which show that the CJC arc rocks possess lower Cu concentrations, V/Sc and Sr/Y ratios, and zircon ∆FMQ values, but higher zircon δ18O values compared to the BM rocks, demonstrating the CJC rocks has lower porphyry ore potential and magmatic oxidation states that were triggered by the addition of reduced sediments. Substantial biogenic sediments within the accretionary complex belts in the CJC imply widespread anoxia of the Junggar ocean due to isolation from wider Paleo-Asian Ocean, which promoted the generation of reduced arc magmas and further inhibited the formation of PCDs. The arc magmatic oxygen fugacity shift indicates that the ocean redox state was recorded in the deep Earth and significantly control the generation of PCDs in arcs.

Acknowledgements: The present study was financially supported by Hong Kong Research Grant Council Joint Laboratory Funding Scheme (JLFS/P-701/18), NSFC Major Project (41890831) and Hong Kong RGC grants (17307918 and 17308023), and HKU Internal Grants for Member of Chinese Academy of Sciences (102009906) and Distinguished Research Achievement Award (102010100). This work is a contribution of the Joint Laboratory of Chemical Geodynamics between the University of Hong Kong and Guangzhou Institute of Geochemistry, Chinese Academy of Sciences.

 

How to cite: Sun, M., Wang, X., and Zhao, G.: Anoxic Ocean inhibited the formation of porphyry copper deposits, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4062, https://doi.org/10.5194/egusphere-egu24-4062, 2024.

EGU24-4167 | ECS | Posters on site | GMPV5.1

Geology, mineralogy and geochemistry of ultramafic-mafic hosted Ni-Co mineralization; Gunes Ophiolite (Eastern Central Anatolia, Türkiye) 

Ali Erdem Bakkalbaşı, Tolga Oyman, and Ramazan Sarı

The Güneş Ophiolite is located in Eastern Central Anatolia, contains number of mineralization in different types in different settings. Nickel-Cobalt-Copper mineralization are generally in association with large mantle-derived igneous complexes or basic igneous rocks of the ophiolitic sequences. Relatively high Ni, Co and Cu contents in addition of sulphur from different sources prompted to form sulphide minerals as a result of gravity segragation coupled with fractional crystallization. Since the Late Cretaceous Güneş Ophiolite’s Ni-Co-Cu potential had been confirmed, through the drilling of the first exploration hole, further drilling programs were conducted by different companies for several years. Ophiolitic sequence is composed of tectonites (harzburgite and orthopyroxenite), cumulates (clinopyroxenite, olivine gabbro), and their serpentinized equivalents, pegmatitic gabbro, massive gabbro, sheeted dike complex and basaltic lava from bottom to top. Whole sequence is cut by sub-volcanic diabasic intrusion and younger distal dykes which differs in terms of lithology but with similar strucural condition. Dykes in association with mineralization strikes generally ENE-WSW and dips 50 to 60° NW.  Three settings of mineralization were identified; a) mineralization occurs in the contact zone between the dykes and ultramafic host rocks as massive, semi-massive and net textured b) in fractures of the dyke c) veins and fissure-fillings with disseminations in ultramafic host rock. Alteration minerals are represented by phlogopite-biotite in the proximal (potassic) part of the mineralization, amphibole group actinolite, tremolite and chlorite are observed towards the middle parts as a result of uralitization of pyroxenes. The distal parts are represented by albite, epidote, chlorite and serpentine associated with unmineralized ultramafics. Ni values in the rock samples vary between 500-4700 ppm and the Co values range between 50-1050 ppm, in the soil samples these ranges are 250-4500 ppm and 50-700 ppm, respectively. Pyrrhotite (Fe1-xSx), pyrite (FeS2), pentlandite ((Ni,Fe)9S8) and chalcopyrite (CuFeS2) were identified in core samples as representative of  primary ore mineralization stage. Early stage oxide minerals are represented by magnetite (Fe3O4), rutile (TiO2) and ilmenite (FeTiO3). According to field and drill core observations, it is though that nickel-saturated ultramafic rocks of Güneş Ophiolite were cut by diabasic dykes of a sub-volcanic intrusion and younger acidic dykes from different origin. In this situation nickel in ultramafics were leached by diabasic and more acidic apophyses and remobilized along ENE-WSW trending structures and dykes. Based on geological setting and structural evolutution and spatial distribution, we suggest that mineralization is mostly related to acidic dykes at the upper parts, whereas at the lower parts, it is mostly associated with highly altered diabasic dykes. It seems like that the enrichment of the main ore minerals shows direct relationship with the thickness of the enclosed individual dyke and it also reflects proximity to the main body of subvolcanic intrusion, in addition to the nickel saturation rate of the ultramafic rock.

Keywords: Ni-Co deposits, Ophiolites, Ultramafics, Ore petrography, Eastern Central Anatolia, Turkey.

 

How to cite: Bakkalbaşı, A. E., Oyman, T., and Sarı, R.: Geology, mineralogy and geochemistry of ultramafic-mafic hosted Ni-Co mineralization; Gunes Ophiolite (Eastern Central Anatolia, Türkiye), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4167, https://doi.org/10.5194/egusphere-egu24-4167, 2024.

EGU24-4292 | ECS | Posters virtual | GMPV5.1

Strain fringes in Hiriyur Formation of rocks, Chitradurga greenstone belt, Karnataka: Implications with ore formation  

Manju Sati, Rajagopal Krishnamurthi, and Sakthi Saravanan Chinnasamy

Paramanahalli gold prospect lies in the Chitrdurga greenstone belt, India; the mineralization found in altered rocks characterized by the mineral assemblage of chamosite (Fe-rich chlorite) + annite (Fe-biotite) + ankerite + quartz + pyrite + gold ± chalcopyrite ± pyrrhotite ± magnetite. Strain fringes are developed with the pyrite and magnetite of the Banded Iron Formation and phyllite of the study area. Strain fringes are indicators of the low-pressure zones parallel to the least compressive stress. These features are massive and monomineralic adjacent to a rigid object (pyrite, magnetite) and are usually composed of a different material than the rigid object. Pyrite and magnetite are euhedral in shape and medium-coarse-grained (20-80 µm) in size. Fringes contain information on flow and style of deformation in their internal and external shape and are helpful kinematic indicators in the mineralized zone. The Hiriyur Formation rocks metamorphosed up to greenschist facies that can retain the pre-deformed shapes. This study illustrates the variety of strain fringes, studied in detail to understand deformation patterns and gold-sulfide mineralization in the research area. Fringe-1 is face-controlled, uneven, made up of fibrous quartz, and associated with rigid magnetite. The uneven nature of extended fringes infers simple shear. Fringe-2 is a face-controlled, variable extended fiber made up of quartz. Fringe-3 is a displacement-controlled fringe consisting of quartz that is similar on both sides and shows typical wing-type features. These stain fringes indicate a sense of rotation after the hydrothermal fluid precipitates ore minerals (pyrite/ magnetite). The presence of strain fringes with pyrite (± gold) infers the remobilization and recrystallization of sulfides during/after a deformation event at Paramanahalli prospect, Karnataka. The current work points toward a strong link between the development of microstructures and ore formation. Based on petrological and microstructural evidence, it is proposed that there was a syn-ore formation / main mineralization event responsible for the precipitation of sulfides, later affected with deformation that leads to the formation of such features.

How to cite: Sati, M., Krishnamurthi, R., and Chinnasamy, S. S.: Strain fringes in Hiriyur Formation of rocks, Chitradurga greenstone belt, Karnataka: Implications with ore formation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4292, https://doi.org/10.5194/egusphere-egu24-4292, 2024.

EGU24-5713 | ECS | Orals | GMPV5.1

The Ouarmdaz region: A new copper-silver potential of the Igherm inlier (Western Anti-Atlas, Morocco). 

Abouttarouk Ayoub, Alikouss Saida, Morsli Yousra, Ennabir Mohamed, Abidi Mohamed, Ouhoussa Lhoussayn, Tahar Rachid, Zerhouni Youssef, Samir Mohamed, and Baroudi Zouhir

The Western Anti-Atlas belt is globally renowned for hosting metallic ore deposits, including large copper-silver deposits. The Ouarmdaz-Chikh Imi Nrfi area is located southwest of the Precambrian Ighrem inlier, approximately 168 km east of the city of Agadir. This area is known for its stratiform copper-silver mineralization along the contact between the Precambrian basement and the infracambrian cover. This level is of particular interest on a regional scale because of its spatial extension.

The Igherm inlier comprises Precambrian basement formations, including polygenic conglomerates, red sandstones, and andesitic lava. The cover consists of a siltstone-sandstone series capped by Tamjout dolomites and lower limestones. These terrains are cross-cut by the Ighrem doleritic dyke and are affected by extremely discrete brittle deformation and very pronounced ductile deformation, indicating highly mineralized zones.

This area is characterized by polymetallic mineralization with copper, silver, lead sulfides, and iron oxides. These mineralizations are hosted in the infracambrian cover. Paragenesis is stratiform, vein-type, or in geodic cavities. The mineralized structures are mainly oriented NE–SW, with a dip of 30° to 50° toward the southwest.

The paragenetic study of mineralization has enabled us to identify the different metallic phases and propose a paragenetic succession. The primary paragenesis comprises pyrite, chalcopyrite, bornite, and galena. The primary mineral phases underwent metasomatism, giving rise to secondary parageneses represented by chalcocite, covellite, malachite, azurite, and iron oxides, including hematite and goethite. This mineralization features complex textures (myrmekitic, collomorphic, carrie, and continent).

The analytical data by (ICP) indicated relatively high levels of copper and copper oxide (<25.4%). Silver with concentrations ranging from 7 to 176 g/t, demonstrates a positive correlation with copper.

Scanning electron microscopy (SEM) analysis revealed that the highest copper concentrations were recorded in the malachite-rich zones. Iron and copper oxides of the delafossite type have also been identified in association with dolomite.

Keywords: Western Anti-Atlas, Ighrem, Ouarmdaz-Chikh Imi Nrfi, Mineralization, stratiform, Copper-silver deposits, ICP, SEM.

How to cite: Ayoub, A., Saida, A., Yousra, M., Mohamed, E., Mohamed, A., Lhoussayn, O., Rachid, T., Youssef, Z., Mohamed, S., and Zouhir, B.: The Ouarmdaz region: A new copper-silver potential of the Igherm inlier (Western Anti-Atlas, Morocco)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5713, https://doi.org/10.5194/egusphere-egu24-5713, 2024.

EGU24-7622 | Posters virtual | GMPV5.1

Geochemistry of Banded Iron Formations (BIFs) from the Central Bundelkhand Craton, India: Implication for depositional setting 

Vivek Prakash Malviya, Harel Thomas, Sanjeet Kumar Verma, Mahendra Shukla, Muduru Lachhana Dora, and Alok Kumar

The depositional environment of the Banded Iron Formations (BIFs) is highly controversial. The BIFs are type of chemical precipitates characterized by presence of alternating layers of iron and silica-rich. Paleo-Mesoarchean BIFs of the Central Bundelkhand Greenstone Belt (Babina-Mauranipur-Mahoba) occur along with the E–W trending of the Bundelkhand Tectonic Zone (BTZ) gives us opportunity to study the depositional environment during Archean Eon. The lithological association of BIFs in the Babina and Mauranipur areas consists of pillowed basic–ultrabasic volcanics and metasediments whereas the Mahoba´s BIFs and quartzite occur within basic volcanics. The bulk geochemical composition of BIFs shows the high content of FeOt with an average of 51.57 wt. %. The Babina´s BIFs show relatively lower concentration of V, Cr and Co in comparison to the Mauranipur and Mahoba. The significant negative Ce anomaly implies the signature of a deep marine source of the Bundelkhand BIFs. The samples from Babina show less Y/Ho ratios, along with lack of relativelyhigh Zr, Th, and Hf suggest that terrestrial material input was insignificantor very less during BIFs precipitation. Most of the BIFs from the Mauranipur and Mahoba show intermediate Y/Ho ratio suggesting chemical precipitation of BIFs from a mixture of seawater and high-temperature hydrothermal fluids generated from a back-arc spreading centre. The geochemical characteristics indicate that these BIFs are formed by volcanogenic hydrothermal activity in aback-arc tectonic setting. The Rare Earth Elements (REE) patterns suggest the role of high-T hydrothermal fluid for the deposition of BIFs in the Babina and Mauranipur greenstone belts whereas low-T hydrothermal fluid is responsible for the Mahoba greenstone belt deposition. Their geochemical variation also suggests the shallowing of the proto-basin from the Babina (west) to Mahoba (east).

How to cite: Malviya, V. P., Thomas, H., Verma, S. K., Shukla, M., Dora, M. L., and Kumar, A.: Geochemistry of Banded Iron Formations (BIFs) from the Central Bundelkhand Craton, India: Implication for depositional setting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7622, https://doi.org/10.5194/egusphere-egu24-7622, 2024.

EGU24-8251 | ECS | Orals | GMPV5.1

A metasomatized lithospheric mantle contribution to the genesis of Li-rich magmas in slab-window settings 

Erwin Schettino, Igór González-Pérez, Claudio Marchesi, José María González-Jiménez, Michel Grégoire, Fernando Gervilla, Idael Blanco-Quintero, Alexandre Corgne, and Manuel Schilling

The geological factors controlling Li abundances in the mantle and mantle-derived magmas rising through the continental lithosphere, as well as their implications for Li ore genesis in the shallow crust, are still under debate. Here, we look from the mantle source perspective at those mechanisms that may boost the Li inventory in continental arc magmas, by characterizing a set of sub-arc mantle xenoliths from the southern Andes (Coyhaique volcanic field, western Patagonia). The mineral trace element signatures and oxygen fugacity estimates (FMQ > +3) in these peridotite xenoliths are consistent with those expected for a mantle wedge fluxed by oxidizing, subduction-related silicate melts rich in slab-derived volatile components. However, our data support that subduction-related metasomatism did not enhance significantly the Li inventory of the sub-arc lithospheric mantle, at odds with the generally claimed major role of slab-derived fluids in enriching Li in the supra-subduction mantle wedge. Major and trace element compositions of minerals also record transient thermal and chemical anomalies fingerprinting the interaction with OIB-type alkaline melts, which percolated through the shallow (7.2-16.8 kbar) and hot (952-1054 °C) mantle wedge in response to the opening of an asthenosphere slab window and ridge collision. This alkaline metasomatism produced exceptionally high Li abundances (6-15 ppm) in metasomatic clinopyroxene, promoting the generation of a Li-rich and fertile lithospheric mantle wedge. A numerical model suggests that low degrees (< 10%) of partial melting of this alkaline-metasomatized sub-arc lithospheric mantle generates primitive melts having Li abundances (⁓13 ppm) much higher than average subduction-zone basalts. Extreme differentiation by fractional crystallization of these Li-rich magmas may provide an effective pathway for enhancing the fold enrichment process required for a magmatic rock to effectively source ore deposition in the shallow arc crust.

How to cite: Schettino, E., González-Pérez, I., Marchesi, C., González-Jiménez, J. M., Grégoire, M., Gervilla, F., Blanco-Quintero, I., Corgne, A., and Schilling, M.: A metasomatized lithospheric mantle contribution to the genesis of Li-rich magmas in slab-window settings, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8251, https://doi.org/10.5194/egusphere-egu24-8251, 2024.

EGU24-8552 | ECS | Posters on site | GMPV5.1

Evidence of boiling in ore-forming process based on quartz textures and fluid inclusions studies, a case study in Mamouniyeh Cu deposit, Iran 

Mohammad Goudarzi, Hassan Zamanian, Urs Klötzli, and Matee Ullah

Boiling is one of the common processes that lead to the formation and enrichment of precious metal deposits. The investigation of the spatial relations between fluid boiling and deposition of precious metals is a valuable tool in exploration of epithermal deposits. Fluid boiling, isothermal mixing and surface dilution of fluids processes are important factors for the instability of chloride and sulphide complexes, which lead to the simultaneous deposition of Fe-Cu and then deposition of sulphide phases in the final stages of mineralization which are caused by a sudden decrease in pressure in the fractures. To investigate evidence of boiling and its role in mineralization we have studied fluid inclusions and quartz textures in the Mamouniyeh Cu deposite in the middle part of Urumieh-Dokhtar magmatic arc in Iran. Evidence for fluid boiling, such as different liquid-vapor ratios of fluid inclusions, the coexistence of fluid inclusions with different salinities and co-existing liquid single-phase fluid inclusions with vapor single-phase fluid inclusions and breccia, crustiform and colloform textures of quartz indicate that boiling process occurred during the formation and growth of minerals. The study of 138 fluid inclusions in ore-bearing silica veins shows the similar density values from 0.8 to 1 g/cm3 for quartz with pyrite + chalcopyrite, chalcopyrite and chalcopyrite + specularite ± pyrite ± chalcocite mineralization systems. Adjacency of multiphase fluids with vapor-rich fluid inclusions indicates that fluids are trapped at the boiling point, that is, in the state where the vapor is in equilibrium with the liquid. As a result of this boiling part of the Cu in the fluids was deposited as chalcopyrite. Evidence shows this process probably occurred at a depth of about 700 meters below the water table and lithostatic pressure of about 16 MPa. In the case study area, boiling, mixing of magmatic fluids with meteoric fluids and cooling process by oxide and sulphide complexes, that this mixing process has reduced the temperature and salinity in the system and caused oxide-sulphide mineralization include chalcopyrite, pyrite, bornite, specularite, and secondary ore minerals include chalcocite, covellite, azurite, malachite, chrysocolla, goethite, and limonite which related to granodiorite, monzonite and gabbro-diorite intrusive rocks.

How to cite: Goudarzi, M., Zamanian, H., Klötzli, U., and Ullah, M.: Evidence of boiling in ore-forming process based on quartz textures and fluid inclusions studies, a case study in Mamouniyeh Cu deposit, Iran, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8552, https://doi.org/10.5194/egusphere-egu24-8552, 2024.

EGU24-9186 | Orals | GMPV5.1

Back to the Otjosondu manganese deposit: an integrated structural, petrological and geochronological study 

Alexis Plunder, Benjamin Le Bayon, Florence Cagnard, Marc Poujol, Nathan Cogné, and Laurent Bailly

The Otjosondu area contains one of the most important Manganese deposit of Namibia. An exploration campaign in the late 2000’s acquired an extensive dataset (fieldwork, drillholes, geophysics and petrological data) to improve our knowledge of the deposit. The geological history is however, ill-studied and the deposit is classically attributed to banded iron formation of the Sturtian Chuos formation from the Damara sequence.

Using samples from drillholes, we here provide Pressure-Temeprature-time constrain using thermodynamic modelling and LA-ICP-MS U-Pb ages on zircon, monazite and apatite to decipher the regional metamorphic evolution. Our petrological study concludes that the Otjosondu Mn deposit is affected by a HT-MP metamorphic event, estimated at ~670°C and 0.6. This HT-MP metamorphism is associated to a strong ductile deformation with development of shear zones, and multiple-scale intense folding. These metamorphic and structural features totally preclude the description of a typical sedimentary sequence, on which the previous authors had based their classical lithostratigraphic comparison. We date this HT metamorphic event at ca. 525Ma using U-Pb ages on monazite in paragneisses and in a granite, and U/Pb ages on zircon in the same granite.

Detrital U-Pb ages on zircon reveal that the maximum deposition age is at ca. 540Ma. This excludes the attribution of the gneisses surrounding the Mn deposit to the Sturtian Chuos Formation challenging the prevailing interpretation of this ore deposit. Detrital U-Pb ages on zircon also record older magmatic events at ca. 620 and 585 Ma, which are well-known regionally, but were not previously documented in the Otjosundu area. Finally, U-Pb ages on apatite (490+/-3Ma) highlight a late thermal event (hydrothermal or static metamorphism). Results of this study illustrates the importance of characterizing the entire geological history of an ore deposit, to improve the future exploration.

How to cite: Plunder, A., Le Bayon, B., Cagnard, F., Poujol, M., Cogné, N., and Bailly, L.: Back to the Otjosondu manganese deposit: an integrated structural, petrological and geochronological study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9186, https://doi.org/10.5194/egusphere-egu24-9186, 2024.

EGU24-10027 | ECS | Orals | GMPV5.1

Antimony isotope composition of the bulk silicate Earth 

Andreas Kaufmann, Marina Lazarov, Ingo Horn, Juraj Majzlan, and Stefan Weyer

Antimony is an incompatible chalcophile element. Its concentration in the Earth’s mantle was estimated to ~0.14 μg g-1 Sb [3], while the Sb estimates for the upper continental crust scatter between 0.2 to 0.8 μg g-1 [4]. Recent analytical advances in the precision and accuracy of stable Sb isotope analyses allowed to assess the potential of δ123SbNIST3102a as a proxy for ore forming [1] and oxidation/weathering [2] processes. Application of this proxy, however, is limited by the lack of knowledge of the Sb isotope composition of the Earth and its fractionation during high-temperature cycling.

Here, we present bulk rock Sb isotopic compositions of a range of basic and ultrabasic USGS reference materials (n = 12) from different settings and a suite of basic rocks (n = 3) from Hawaii, aiming to estimate the Sb isotopic composition of the bulk silicate Earth (BSE).  The sample suite shows an isotopic range (all values expressed hereafter as δ123SbNIST3102a) from -0.10 to +0.27 ‰. Two of the fifteen samples display an isotopic composition of > +0.24 ‰ which are, however, marked by low Nb/U, Ce/Pb, and elevated Zr/Nb, indicating crustal contamination in the magmatic source [5]. Excluding these two samples our analyzed sample suite shows an average δ123SbNIST3102a value of +0.01 ± 0.08‰ that we suggest as a preliminary reference value for the Sb isotope composition of the bulk Earth. Our findings furthermore provide first insights for Sb isotope variations in high-temperature rocks that may be related to recycling processes in the mantle.

[1] Zhai et al. (2021), GCA. 3016, 84-97.

[2] Ferrari et al. (2023), Chem. Geol. 641, 121788.

[3] McDonough and Sun (1995), Chem. Geol. 120, 223-253.

[4] Majzlan and Filella (2023), Geochem. In press, 126072.

[5] Hofmann et al. (1986), EPSL. 79(1-2), 33-45.

How to cite: Kaufmann, A., Lazarov, M., Horn, I., Majzlan, J., and Weyer, S.: Antimony isotope composition of the bulk silicate Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10027, https://doi.org/10.5194/egusphere-egu24-10027, 2024.

The European Kupferschiefer Province contains multiple sediment-hosted stratiform copper (SSC) deposits and has been mined for many centuries. The mineralized rocks of the Kupferschiefer are stratabound and hosted by a stratigraphic succession of Late Permian terrestrial sandstones (Rotliegend Formation) and transgressive marine mudstones and limestones (Zechstein Formation). The formation of the Kupferschiefer deposits has been described by various genetic models, which primarily differ in terms of the timing of ore stage sulfide formation relative to host rock deposition (i.e. syn-genetic vs. epigenetic). In this study, samples from two drill cores in the Spremberg-Graustein Kupferschiefer deposit (eastern Germany) are described. Reflected light and scanning electron microscope (SEM) petrography has been used to determine key paragenetic relationships and in situ sulfur isotope values of pyrite and chalcopyrite (secondary ion mass spectrometry; SIMS) have been generated to determine pathways of sulfide formation. The extensive replacement of carbonate and feldspar by ore stage sulfides provides evidence that hydrothermal activity post-dated the formation of diagenetic phases in all units. The highly negative δ34S values of pyrite (–41.9‰ to –35.7‰) and chalcopyrite (–38.9‰ to –34.5‰) indicate that reduced sulfur was generated via open system organoclastic sulfate reduction (OSR). The indistinguishable δ34Schalcopyrite values preserved in the Rotliegend sandstones and Zechstein mudstones suggest a common origin of sulfides in distinct lithologies. To reconcile the petrographic evidence of host rock replacement with the isotopic evidence of open system sulfate reduction requires an external source of bacteriogenic sulfur, most likely in the form of a low temperature sulfur rich brine. The infiltration of low temperature brines transporting bacteriogenic sulfur is a key feature of genetic models in other sediment hosted systems (e.g., Irish Zn Ore Field). If this model is applied to the Kupferschiefer district, exploration programs should target subbasins with evidence of low temperature brine circulation from marginal sedimentary facies.

How to cite: Magnall, J., Liu, Y., Gleeson, S., and Rocholl, A.: The origin of the Kupferschiefer mineralization (eastern Germany): constraints from petrography and analysis of stable sulfur isotopes of pyrite and chalcopyrite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10634, https://doi.org/10.5194/egusphere-egu24-10634, 2024.

EGU24-10804 | ECS | Posters on site | GMPV5.1

Microchemical analyses of the alteration and sulfide minerals associated with the Şirindere gold mineralization at the Central Menderes Massif, West Turkiye 

Hatice Nur Bayram, Mustafa Kumral, Amr Abdelnasser, Ali Erdem Bakkalbasi, and Mustafa Kaya

The present study focuses on the mineral chemistry data of hydrothermal alteration and sulfide minerals that are related to gold mineralization in the Şirindere area of the Ödemiş-Kirazlı tectonic unit of the Menderes Massif polymetamorphic complex, located in WestTurkiye. The study area contains paragneiss, orthogneiss, and various types of schists (muscovite-, tremolite-, and actinolite-schists) of the Pan-African basement rocks that constitute the central part of the Menderes Massif complex. Additionally, there are Permian garnet-mica schist and marble lenses, as well as Triassic orthogneiss, which are part of the Paleozoic cover series. The Şirindere gold mineralization occurred as gold-bearing quartz carbonate veins hosted within the garnet-mica schist. The veins exhibit boudinage patterns that run parallel to the schistosity direction within the shear zone, which has a N-S orientation, include two types of quartz crystals.The main types of hydrothermal alteration that occurred adjacent to the auriferous quartz-carbonate veins are silicification, chloritization, and sericitization, with subordinate carbonatization alteration types. The ore mineralogy includes pyrite and chalcopyrite associated with free native gold and native copper. The minerals albite, biotite, calcite, chlorite, garnet, sericite, and quartz have been analyzed using an electron microprobe, together with chalcopyrite, pyrite, and gold. According to the EPMA data, the biotite is categorized as magmatic and re-equilibrium Fe-biotite that originated from both crustal and crust-mantle sources within the peraluminous suites. Chlorite is mostly classified as Fe-chlorite (chamosite), which is formed within a temperature range of 249°C to 355°C with an average temperature of 275°C. Sericite has a larger proportion of muscovite (XMs) ranging from 0.89 to 0.96 (average XMs = 0.94), with a phengite content ranging from 0.35% to 1.55%. The EPMA trace element analyses of the pyrite minerals are plotted in the fields of magmatic-hydrothermal and carlin-type gold deposits. This pertains to sulfur derived from juvenile magmatic and/or upper mantle sources with slightly sedimentary origins. Furthermore, these pyrite minerals serve as the primary source of gold, as they include small mineral inclusions like visible gold and chalcopyrite. The pyrite has high amounts of gold, with maximum values reaching 270 ppm. It is hypothesized that the pyrite undergoes longer-term crystallization and co-precipitates with native gold and chalcopyrite. The Şirindere region has been affected by many metamorphic episodes and deformational events caused by various orogenies, including M1, M2, M3, and M6, as well as D3 and D4. During M6, which was represented by the Main Menderes Metamorphism (MMM) that occurred along the Alpine orogeny, it is believed that the gold mineralization in the study area resulted from the metamorphic fluid that formed due to the hydration and decarbonization of volcano-sedimentary rock. This fluid leached gold from the previously formed mafic rock, specifically the tremolite-actinolite schist (metagabbro) in the study area. The gold then migrated upwards along the N-S extensional shear (D3–D4). Hence, the evolution of gold-sulfide mineralization in the Şirindere area may be attributed to the regional metamorphism and deformation caused by the Alpine orogeny, which affected the pre-existing Pan-African basement units.

Keywords: EPMA data, geochemistry, gold-bearing quartz-carbonate veins, Menderes Massif, Şirindere(Aydın,Turkiye)

How to cite: Bayram, H. N., Kumral, M., Abdelnasser, A., Bakkalbasi, A. E., and Kaya, M.: Microchemical analyses of the alteration and sulfide minerals associated with the Şirindere gold mineralization at the Central Menderes Massif, West Turkiye, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10804, https://doi.org/10.5194/egusphere-egu24-10804, 2024.

EGU24-11484 | ECS | Posters on site | GMPV5.1

Mineral chemistry of sphalerite from volcanogenic massive sulphide deposits: genetical implications 

Botond Géza Gereczi and Gabriella B. Kiss

Though sphalerite is a common mineral in hydrothermal ore mineralization, there are still several open questions in terms of its mineralogical characterization. Many elements may appear in its structure such as Fe, Mn, Cu, Cd, Co, Hg, Ga, Ge, Ag, In, Tl, Se, etc. and some of them may correlate with the formation conditions (e.g., the amount of Fe strongly depends on formation T). For this reason, it is expected that composition of sphalerite my fingerprint the ore deposit type, although, until now only a few attempts were made to investigate this topic. As even technological/critical metals could be enriched in sphalerite (e.g. Co, Ga, Ge, Mn, In, etc.), this topic should be in the spotlight of modern research.

As a contribution to this field, we selected to study sphalerite from volcanogenic massive sulphide (VMS) deposits. Our investigation areas were chosen from the Neothethyan realm: Xylagani from the Hellenides, Greece; Gjegjan from the Dinarides, Albania and Lasail from the Semail Ophiolite, Oman. While Xylagani and Lasail has been identified as Cyprus-type VMS, the classification of Gjegjan ore deposit is uncertain. Our study supports its VMS related origin (more precise classification would need more detailed studies), but its host basalt formed most likely during the Triassic, advanced rifting stage, rather than during the oceanic stage of the Neotethys.

We performed petrographic microscopic, SEM-EDS and EPMA studies on sphalerite-bearing samples, aiming to characterise their texture, their mineral paragenesis, their mineral precipitation series and the mineral chemistry of sphalerite. It has been found that sphalerite mostly precipitated at the early stage of mineralisation, during the upbuild of the hydrothermal system, though at some places it also formed as a late product, during the waning of the system. Early sphalerite often suffered “chalcopyrite disease”, caused most likely by later Cu-rich fluid impulses. All studied sphalerite precipitated from a 238 °C to app. 60 °C warm fluid, characterised by an intermediate sulphidation state (logfS2). We identified chemical anomalies in sphalerite, like Co in Lasail (up to 1230 ppm in massive suphide lens) and Ga in Gjegjan (up to 840 ppm in distal part of the mineralization). Fe (1,039–3,973 wt.%), Cd (950–3220 ppm), Mn (b.d.l.–2680 ppm) and Pb (b.d.l.–1260 ppm) was also presented in all samples and good correlations (R2 > 0,64) were found between Fe–Zn, Cu–Zn, Fe/Cd–Zn and Fe/S–Zn.  Extreme Co enrichment of sphalerite could have been caused by a sudden change in the fugacity of S2 and/or O2 in the massive sulphide lens, while high Ga content favours low temperature conditions and may be accompanied by Ge anomaly as well. The identified Co and Ga anomalies not only may represent a new source of extractable raw materials for the investigated ore deposits, but understanding the reasons for enrichment of these critical raw materials can help to make mining more economical when exploring other similar ore deposits.

How to cite: Gereczi, B. G. and B. Kiss, G.: Mineral chemistry of sphalerite from volcanogenic massive sulphide deposits: genetical implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11484, https://doi.org/10.5194/egusphere-egu24-11484, 2024.

EGU24-11597 | ECS | Orals | GMPV5.1

The Setting and Timing of Copper Mineralization in the Timna Igneous Complex, southern Israel. 

Alon Elhadad, Elisha Bar, Yevgeny Vapnik, Itai Haviv, Andrew Kylander-Clark, Tzahi Golan, and Yaron Katzir

The absence of primary sulfides challenges the interpretation of metal ore genesis, particularly where ore is hosted within several separate stratigraphic horizons. In the Timna Valley, S Israel, copper ore bodies occur mostly in Cambrian and Cretaceous sandstones and rarely in the underlying late Neoproterozoic Timna igneous complex (TIC), as secondary Cu-sulfides in veins and nodules and more abundantly as Cu-hydroxides. The timing and setting of copper mineralization in the TIC and its relation to the sedimentary ore are unknown. Quartz phenocryst-hosted fluid inclusion assemblages (FIA) in quartz porphyry (QP) stock and dykes are associated with sulfide inclusions of pyrite, chalcocite, and chalcopyrite, indicating a magmatic-hydrothermal genetic relationship. Mineralization-associated fluid inclusion assemblages (FIAs) in QP are: (FIA.a) <12 wt% NaCl eq., CO2 vapor-rich arrays with and homogenization temperatures (Ths) of 270­­­­­­­­­­­­–500°C; ­­­­­(FIA.b) immiscible 30–35 wt%. NaCl eq. aqueous liquid and a CO2 vapor-rich fluid trapped at 193–266°C; (FIA.c) secondary H2O liquid-rich arrays (0-11 wt% NaCl eq.), Th of 115–256 ⁰C. Mineralization-associated zircon and rutile in QP yielded U–Pb ages of ~595 Ma, overlapping alkaline felsic dykes in S Israel. Rapid cooling below 220°C is evident by average rutile (U–Th)/He age of 595 ± 46 Ma found in QP and adjacent quartz monzonite and porphyritic granite. Zircon (U–Th)/He ages record Carboniferous heating at 180 ⁰C ≤ T ≤ 220 ⁰C and hydrothermal alteration. This indicates temperatures in the TIC did not exceed ~180 ⁰C after the Carboniferous. Primary copper mineralization in the TIC is attributed to QP emplacement, during A-type granite intrusions, possibly scavenging copper and other metals from earlier calc-alkaline crust. This was followed by lower temperature (<220°C) hydrothermal events.

How to cite: Elhadad, A., Bar, E., Vapnik, Y., Haviv, I., Kylander-Clark, A., Golan, T., and Katzir, Y.: The Setting and Timing of Copper Mineralization in the Timna Igneous Complex, southern Israel., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11597, https://doi.org/10.5194/egusphere-egu24-11597, 2024.

EGU24-13247 | Posters on site | GMPV5.1

 Re-equilibration processes in magnetite from an Iranian BIF deposit. 

Christiane Wagner, Omar Boudouma, Nicolas Rividi, Beate Orberger, Ghassem Nabatian, and Maryam Honarmand

Magnetite is common in various iron ore deposits including BIF, Fe-skarn, IOGC (iron oxide-copper-gold), IOA (iron oxide-apatite) and porphyry Cu-Au deposits. Magnetite incorporates a number of trace elements in tetrahedral and octahedral site in its structure. Its trace element composition has been used in numerous studies to fingerprint deposit type and ore genesis and to provide a guide for mineral exploration, based on a series of discriminant diagrams (e.g. [1]). However, the applicability of such diagrams must be carefully evaluated as the composition of magnetite can be modified by various processes. In this study we present textural and compositional data for magnetite from a late Ediacaran BIF in NW Iran[2] to illustrate complex re-equilibration processes.

Three stages of magnetite (Mt) has been identified. Mt1 forms large (≤1 mm) inhomogeneous dark grey grains surrounded and locally invaded by a light grey porous Mt2. The Mt1/Mt2 boundary is irregular and sharp, consistent with replacement textures. Bright Mt3 forms needle-like bands (10-80 µm width) aligned along fracturing planes. Mt3 contains rare hematite relicts and is porous in close proximity to hematite.

Mt1 shows a variable trace element composition and contains the highest Si (average 1.14 wt.%), Al and Ca (0.28 wt.%), Mg (0.13 wt.%) and the lowest Fe (68 wt.%) contents. Both Mt2 and Mt3 show a restricted range of composition. Mt2 has lower Si (0.68 wt.%), Al (0.14 wt.%), Ca (0.15 wt.%) and Mg (0.08 wt.%) contents, while Mt3 is characterized by the lowest Si (0.16 wt.%), Al and Ca (0.05 wt.%) and Mg (0.01 wt.%) and the highest Fe (71.1 wt%) contents. The three magnetite have low Mn (≤0.03 wt.%), and Ti (≤0.02 wt.%), and Ni and Cr are mostly below the detection limit.

The silician dark Mt1 magnetite likely forms in a rather reduced Si-rich environment. The presence of structural silicon is supported by correlations / antithetic correlations with R2+/R3+ cations and the lack of inclusions. The incorporation of Si may cause lattice defects or deformation facilitating fluid alteration. A fluid-assisted coupled dissolution of Mt1 and precipitation of Mt2 (CDR process) is supported by close spatial relationship, sharp compositional boundaries, similar crystallographic structure of MT1 and Mt2 and abundant porosity in Mt2. The increase in porosity promotes the infiltration of hydrothermal fluids and further advances the CDR process. By removing trace elements from the early Mt1 this process increases the iron grade of Mt2.

Micro-fracturing allows the penetration of a more oxidized fluid along cleavage planes and formation of needle-like bands of hematite. Then porous mushketovite Mt3 formed after hematite under a more reduced fluid composition by a redox transformation supported by the volume decrease.

All these processes significantly modified the texture and composition of the magnetite and point to a predominant imprint of hydrothermal fluid, thus causing difficulties in using magnetite as a genetic indicator.

 [1] Dupuy and Beaudoin, 2011; [2] Honarmand et al, in press.

How to cite: Wagner, C., Boudouma, O., Rividi, N., Orberger, B., Nabatian, G., and Honarmand, M.:  Re-equilibration processes in magnetite from an Iranian BIF deposit., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13247, https://doi.org/10.5194/egusphere-egu24-13247, 2024.

EGU24-15044 | ECS | Orals | GMPV5.1

Role of sedimentary sulfates in the genesis of massive Ni-Cu-PGE deposits - constraints from the Sakatti Cu-Ni-PGE deposit, Northern Finland 

Henri Höytiä, Petri Peltonen, Tapio Halkoaho, Juha Karhu, and Pertti Lamberg

The Paleoproterozoic (c. 2054 Ma) Sakatti Cu-Ni-PGE deposit is one of the most significant metal discoveries in Europe during the 21st century with the resource of 44.4 Mt @ 1.9 wt.% Cu, 0.96 wt.% Ni, 0.05 wt.% Co, 0.64 g/t Pt, 0.49 g/t Pd and 0.33 g/t Au. The deposit lies in the municipality of Sodankylä, northern Finland, that is emerging as a Ni-Cu-PGE mining camp, already including the Kevitsa Ni-Cu-PGE mine (Boliden) and several subeconomic magmatic sulfide deposits. The Sakatti ore mainly consists of massive Ni- and Cu-dominated ore lenses (Cu/Ni < 0.5, Pd/Pt ≈ 4, and Cu/Ni ≈ 9, Pd/Pt ≈ 1, respectively). These massive ore shoots are surrounded by a veil of Cu-rich disseminated sulfides (Cu/Ni ≈ 7, Pd/Pt < 1) hosted by olivine cumulates and coarse-grained gabbronorites. In the upper parts of the deposit, massive ore lenses grade into Cu-rich stockwork vein ore (Cu/Ni > 100, Pd/Pt ≈ 2) that partly sits in olivine cumulates and partly in flanking komatiitic lavas. The sulfide deposit is underlain by tens of meters thick anhydrite-carbonate rock unit that represent a Paleoproterozoic meta-evaporite based on carbon and sulfur isotope values. Sulfate-bearing sediments are a legitimate source of sulfur for magmatic Ni-Cu-PGE deposits, as demonstrated by major Ni-Cu(-PGE) deposits, e.g., Noril‘sk-Talnakh (RUS), Bushveld and Uitkomst Complexes (RSA), Munali in Zambesi belt (ZMB) and Quill Creek Intrusive Complex in Slave Craton (CAN).

The ore and host rocks in Sakatti exhibit chaotic magma-sulfate interaction textures, salt crystal pseudomorphs, and crustal contamination trends that are evident in major and trace element geochemistry as well as in isotope geochemistry. The Sakatti deposit contains typical indicator minerals such as marialitic scapolite, albite, chlorapatite, pargasite and phlogopite-biotite resulting from the interaction of magma with sulfate evaporites and/or saline brines derived after dissolution of evaporites. Sulfur isotope ratio from different ore types is rather uniform (δ34SCDT c. 3-4 ‰) suggesting a mainly non-mantle source for sulfur and isotopically homogeneous sulfide phase, either due to homogeneous source composition or complete mixing of sulfur from multiple sources before its precipitation as sulfide. Assimilation of sulfate and conversion to a sulfide ore is a complex process likely facilitated by a co-existing fluid phase due to the degassing caused by assimilation. Recent melting experiments using Noril’sk picrite and sedimentary rocks have demonstrated how sulfate incorporation into mafic-ultramafic magmas by diffusion does not unequivocally lead to precipitation of sulfides but instead to a sulfate-rich magma, that further requires interaction with a reductant such as carbon-rich sediments, before sulfides may precipitate. Recognizing the role of sulfates in formation of a magmatic sulfide ores is detective work, as pristine sulfate evaporites tend to vanish from the geological record in structurally complex Precambrian metamorphic terrains, leaving only cryptic marks to the mineral deposits, including skarns, Cl-alterations, pseudomorphs, breccias and heat-resistant sulfates (e.g., anhydrite).

How to cite: Höytiä, H., Peltonen, P., Halkoaho, T., Karhu, J., and Lamberg, P.: Role of sedimentary sulfates in the genesis of massive Ni-Cu-PGE deposits - constraints from the Sakatti Cu-Ni-PGE deposit, Northern Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15044, https://doi.org/10.5194/egusphere-egu24-15044, 2024.

The Börzsöny mountain is part of the neogene Inner Carpathian volcanic belt and located in north of Hungary, close to the Central Slovakian Volcanic Field. The andesitic-dioritic rocks of the mountain host ore deposits of a porphyry hydrothermal system, but most of these ore bodies are barely known.

The complex volcanic history of the Börzsöny took place in the middle miocene. According to the K/Ar dating of the host and overlapping volcanic rocks, the ore formation is related to the first, mostly explosive and finally intrusive stage of the volcanic activity (15.2 – 14.8 Ma) (Korpás et. al, 1998). The elevated position of the crystalline basement in the central part of the Börzsöny showed by different geophysical measurements and endomagmatic rock inclusions suggest the presence of a large dioritic intrusive body at a depth of about 2.5 km from the surface (Csillagné Teplánszky et. al., 1980). The ore deposits discovered until now fall on a ring-shaped structure left over from the uplift (Korpás et. al, 1998).

The best investigated part of the ore complex is the central epithermal ore deposit called Rózsabánya. During geological research of two decades, a weak porphyry copper deposit was discovered below Rózsabánya at a depth of about 1.2 km (Csillagné Teplánszky et. al., 1980).

Based on ore petrography and SEM measurements, the multistage paragenesis of Rózsabánya started with the mineralization of arsenopyrite with some cobalt content, native gold and bismuth. This first stage was followed by a Zn-Cu-Pb-Ag-Sn-In mineral association mostly related to galena, sphalerite and chalcopyrite, that could be found as remnants in later minerals in almost all cases. In the third stage, the former minerals were partly consumed by a large amounts of pyrrhotite, which altered to different degrees to pyrite±marcasite. The next stage is characterised by galena, chalcopyrite and sphalerite mineralization, without Sn and In. The mentioned minerals are often replaced by pyrite±marcasite, Bi-sulphides and –sulphosalts, occasionaly arsenopyrite (with some cobalt and nikkel content) and finally by siderite. In some cases, where the alteration of pyrrhotite to pyrite and marcasite was intensive, the mineralization is associated with chloritization.

Based on the observed textures and paragenesis of Rózsabánya, some of the important thermodynamic parameters of the system could be estimated. After the mineralization of a low sulphidation state epithermal mineral assemblage, increasing temperature (around 400 – 450 °C according to the mol fraction of FeS of the pyrrhotite) and/or decreasing sulphur and oxigene fugacity caused the pyrrhotite mineralization. With cooling and elevation of sulphur and oxigene fugacity, the system crossed the pyrrhotite-pyrite reaction line, the sulphidation state of the system changed to intermediate and native gold and bismuth were partly dissolved during this process. While the bismuth re-precipitated as native bismuth, bismuth-sulphide and –sulphosalts (at slightly acidic-neutral pH), gold was carried to longer distances.

The presence of geochemical barriers where gold could be precipitated, the cause of the mentioned changes in the hydrothermal system and the relation of these processes to the deep level and the surrounding epithermal deposits are the subjects of further research.

How to cite: Mészárosné Turi, J.: Geological and geochemical investigation of ore bearing deposits in the Börzsöny mountains, N-Hungary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15759, https://doi.org/10.5194/egusphere-egu24-15759, 2024.

EGU24-16622 | ECS | Orals | GMPV5.1

The mineralizations of the Allumiere-Tolfa District (Central Italy) 

Francesca Corrado, Germano Solomita, Giuseppina Balassone, Angela Mormone, Barbara Marchesini, Stefano Tavani, Eugenio Carminati, Monica Piochi, and Nicola Mondillo

The Allumiere-Tolfa district is located approximately 60 kilometers northwest of Rome (Italy) and has been characterized by a long mining history for base metals (Pb, Fe), alunite and kaolinite mineralizations dating from prehistoric times (Field & Lombardi, 1972).

These deposits are genetically associated with the emplacement in arc setting of a Plio-Pleistocene volcanic dome consisting of latites and rhyolites, which intruded sedimentary carbonate and siliciclastic country rocks. The intrusive event first produced contact metasomatism of the limestones, and lately triggered hydrothermal activity, which caused a widespread epithermal alteration of the volcanic rocks, resulting in the alteration of the volcanic rocks and emplacement of polymetallic proximal association of Hg-Sb, Pb-Cu, Fe, Zn, Ag, Ba-Sr, F and distal U, Th, Ce, La, Be, Ba, Sr mineralizations (Masi et al., 1980, Della Ventura & Patanè, 2020).

The present work is part of a bigger project investigating various geological features of the Allumiere-Tolfa district (Marchesini et al., 2023) and aims to deepen previous knowledge and investigate in detail the nature of the polymetallic mineralizations of the area. Samples, collected in old pits and outcrops, were analyzed through various techniques: optical microscopy, X-ray diffraction, SEM-EDS analysis, and chemical analysis.

In the area, it was possible to identify distinct alteration facies, residual silica, advanced argillic and argillic facies, with specific ore minerals. The residual silica facies is commonly sulfide-bearing, containing pyrite, As-pyrite, cinnabar, with sphalerite, galena and chalcopyrite. In the advanced argillic facies, pyrite is disseminated in between the aggregates of planar crystals in veins and cavities. Pyrite is also associated with smectite and dickite in the argillic alteration zone. The metasomatized carbonates contain several sulfides such as pyrite and cinnabar with molybdenite, Sr-sulfates, thorutite, thorianite and fluorite. Supergene alteration affected this epithermal assemblage bringing to the formation of gossans with Fe-oxy-hydroxides and secondary sulfides. Preliminary bulk-rock chemical analyses report trace to ultra-trace concentrations of Au.

The identified alteration zones and ore minerals in outcropping rocks indicate low-temperature ore-forming conditions, similar to those occurring in epithermal ores (Simmons et al., 2005), suggesting that possibly the mineralized system extends in depth.

References

Della Ventura G. & Patanè A., 2020. Le miniere dei Monti della Tolfa-Allumiere. Memorie Descrittive Della Carta Geologica D’Italia 106, 23-32.

Field C. & Lombardi G, 1972. Sulfur Isotopic Evidence for the Supergene Origin of Alunite Deposits, Tolfa District, Italy. Mineral. Deposita (Berl.) 7, 113-125.

Marchesini B., Tavani S., Mercuri M., Mondillo N., Pizzati M., Balsamo F., Aldega L., Carminati E., 2023. Structural control on the alteration and fluid flow in the lithocap of the Allumiere-Tolfa epithermal system. Journal of Structural Geology, 105035.

Masi U., Ferrini V., O’Neil J. R. & Batchelder J.N., 1980. Stable Isotope and Fluid Inclusion Studies of Carbonate Deposits from the Tolfa Mountains Mining District (Latium, Central Italy). Minerl. Deposita (Berl.) 15, 351-359.

Simmons S.F., White N.C. & John D.A., 2005. Geological Characteristics of Epithermal Precious and Base Metal Deposits. Economic Geology 100th Anniversary Volume, 485-522.

 

 

How to cite: Corrado, F., Solomita, G., Balassone, G., Mormone, A., Marchesini, B., Tavani, S., Carminati, E., Piochi, M., and Mondillo, N.: The mineralizations of the Allumiere-Tolfa District (Central Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16622, https://doi.org/10.5194/egusphere-egu24-16622, 2024.

EGU24-19401 | ECS | Posters on site | GMPV5.1

Origin and geochemical variability of massive sulfide veins in the Permian Kupferschiefer Formation: insights from the Fore-Sudetic Monocline, Poland  

Katarzyna Derkowska, Piotr Wojtulek, Marina Lazarov, Jakub Kierczak, Jakub Ciążela, and Paweł Derkowski

The Fore-Sudetic Monocline, stretching from southwestern Poland to central Germany, hosts significant sediment-hosted copper deposits associated with the Kupferschiefer formation. While the Kupferschiefer generally displays dispersed mineralization in sandstone, black shale, and dolomite layers, massive mineralization is rare but noteworthy. Our investigation focuses on the Lubin district and aims to enhance understanding of the formation of massive sulfide veins and their setting in the complex stages of Kupferschiefer development.

Four mineralogically distinct types: chalcopyrite-pyrite, chalcopyrite-galena, galena, and chalcocite veins are identified. Each forms complex structures with mineralogical overgrowths, replacements and minor occurrences of bornite, pyrite, sphalerite, tennantite, and tetrahedrite. The diversity extends to geochemistry, with observed variations in bulk trace element concentrations, where strong Hg, Co, and Mo enrichment in the chalcopyrite-galena zone (3500-7000 ppm, >2000 ppm, 25-50 ppm, respectively), Zn, Hg, and Cd in the galena zone (3-5 wt%, 0.5-1.5 wt%, 90-210 ppm, respectively), and Re in the chalcocite zone (200-1000 ppm) is observed. Chalcocite and galena veins show significantly stronger REE depletion, compared to the chalcopyrite-dominated ones. Finally, differences in Cu, As (pyrite), Pb, Ag, Co, Ga (pyrite and chalcopyrite), Zn (chalcopyrite), and Co (galena) concentrations are noted within the minerals from different mineralogical zones.

The complex mineralogy of the veins exhibits isotope variations based on in-situ Cu isotope analyses. The δ65Cu in chalcopyrite, chalcocite, and bornite (chalcopyrite-pyrite and chalcocite veins) spans from approximately -1‰ to +~0.5‰, with lower δ65Cu in chalcopyrite compared to other minerals within a sample. This data suggests complex chalcopyrite formation and its subsequent alteration, mostly to secondary bornite. Relatively small differences between minerals within the sample result from the isotopic equilibration with the ambient fluid responsible for the vein’s origin. However, the disparity between various samples in their Cu isotope composition indicates differences in the ambient fluid origin, i.e. possible time-related separation in veins formation or the isotope fractionation process that took place after sulfides precipitation process.

The study was funded by the National Science Centre grant to KD (2019/35/N/ST10/04524).

How to cite: Derkowska, K., Wojtulek, P., Lazarov, M., Kierczak, J., Ciążela, J., and Derkowski, P.: Origin and geochemical variability of massive sulfide veins in the Permian Kupferschiefer Formation: insights from the Fore-Sudetic Monocline, Poland , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19401, https://doi.org/10.5194/egusphere-egu24-19401, 2024.

EGU24-19743 | ECS | Orals | GMPV5.1

The role of volatiles in forming high-grade porphyry Cu deposits: learnings from apatite inclusions in zircon 

Giulia Consuma, Anthony Kemp, Laure Martin, Brian Tattich, Steffen Hagemann, and Marco Fiorentini

Volatiles, such as H2O, S, Cl and CO2, play a crucial role in regulating volcanic emissions and contribute significantly to the genesis of ore deposits. However, a comprehensive understanding of their role presents a significant challenge due to the intricate task of quantifying the volatile budget and assessing the timeframe linked to magma ascent and volatile exsolution in ore systems.

Apatite, Ca5(PO4)3(F,Cl,OH), stands out as a well-established repository of various volatile species (H2O, CO2, S, halogens) in addition to numerous trace elements, making it an excellent mineral to study the volatile budget of magmas. When encapsulated in zircon, apatite inclusions can preserve a unique record of the abundance of volatile ore-forming constituents, eliminating potential influences from diffusion, degassing, and alteration effects associated with late-stage melts and/or hydrothermal fluids.

Our investigation focuses on thoroughly examining such inclusions, alongside groundmass apatite from the Escondida porphyry Cu-Mo±Au district in Northern Chile, which represents one of the most significant high-grade porphyry copper districts in the world. The ore-forming magmatism of the Escondida district took place in the framework of the protracted late Eocene-Oligocene arc magmatic activity, favouring the emplacement of multiphase porphyry stocks.

To resolve the volatile budget of the melt/fluid responsible for the Cu-Mo±Au mineralization in Escondida, we selected a suit of minimally altered samples from mineralized felsic-intermediate igneous intrusions as well as barren counterparts that are spatially associated with the copper mineralization but do not contain metals in sufficient quantity to be extracted and sold at a profit.

The employed multi-microanalytical approach on apatite (SEM-BSE-CL imaging, EPMA, δ34S by SIMS) and the host zircon (Ti-in-zircon geothermometry, U-Pb geochronology), allowed us to determine:
a) the concentrations of halogens in the melt, which contribute to our understanding of the initial, optimal volatile composition for high-grade copper mineralization; b) the pathway and relative timing of volatile exsolution during the magmatic-hydrothermal stage; c) the hydrothermal volatile record of apatite associated with the mineralization stage.

Our work provides new insights into the role of volatiles in arc magmatic settings, demonstrating their potential in shaping economically viable deposits, a crucial cornerstone for a sustainable and environmentally conscious future.  

 

 

How to cite: Consuma, G., Kemp, A., Martin, L., Tattich, B., Hagemann, S., and Fiorentini, M.: The role of volatiles in forming high-grade porphyry Cu deposits: learnings from apatite inclusions in zircon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19743, https://doi.org/10.5194/egusphere-egu24-19743, 2024.

EGU24-20021 | ECS | Posters on site | GMPV5.1

Petrogenetic constraints of the W-Sn-bearing Abraveses granite (Viseu, Central Portugal) 

Carla Carvalho, Iuliu Bobos, and Fernando Noronha

The Abraveses massif consists of a syn- to late-D3 two-mica granite which crops out along the core of the NW-SE-trending Porto-Viseu D3 antiform. Multiple W-Sn mineralizations are spatially associated with this granitic massif. From a geochemical standpoint, the Abraveses granite is characterized by a strongly peraluminous signature (A/CNK = 1.25 - 1.51), suggesting it was produced by partial melting of a metasedimentary protolith in mid crustal levels (S-type affinity). The low CaO/Na2O ratio (0.1 - 0.2) and high Rb/Sr (12.2 - 18.5) and Rb/Ba (3.4 - 5.3) ratios indicate that the respective magma was derived from a metapelitic (plagioclase-poor) protolith. The granitic samples present low REE contents (ΣREE = 69.19 - 91.33 ppm). The respective chondrite-normalized pattern is moderately fractionated, showing a relative enrichment in LREE (LaN/YbN = 9.02 - 10.86) and a negative Eu anomaly (Eu/Eu* = 0.32 - 0.39). The LREE fractionation is higher compared to the HREE fractionation (LaN/SmN = 2.75 - 3.30; GdN/YbN = 1.82 - 2.17). The UCC-normalized spidergram shows a strong enrichment in Rb, Cs, U and Ta. A significant depletion in Ba, Sr and Ti is also observed. These geochemical features are consistent with the presence of biotite in the crustal source. The strong ore-forming potential of the Abraveses granite is confirmed by its remarkable enrichment in Sn (51 - 106 ppm), W (4 - 17.8 ppm) and ore-transporting volatiles such as F and B. Specialized peraluminous granites from northern and central Portugal typically contain Sn and W concentrations close to those obtained in our study.

How to cite: Carvalho, C., Bobos, I., and Noronha, F.: Petrogenetic constraints of the W-Sn-bearing Abraveses granite (Viseu, Central Portugal), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20021, https://doi.org/10.5194/egusphere-egu24-20021, 2024.

EGU24-20409 | ECS | Orals | GMPV5.1

Extreme enrichment of lithium in granitic pegmatite by liquid immiscibility 

Xiao-Dong Chen and Bin Chen

Single-stage partial melting modeling of meta-sediments or extreme fractional crystallization is inadequate for producing melts with the required Li content (>5000 ppm) for spodumene saturation. Therefore, multi-stage partial melting or fractional crystallization processes have been simulated to achieve the necessary Li content. However, these modeling approaches have overlooked the phenomenon of liquid immiscibility, which has been widely observed in the formation of spodumene-rich granitic pegmatites through studies of melt/fluid inclusions. In this study, we investigate the contribution of liquid immiscibility to the enrichment of lithium in granitic pegmatites by conducting elemental micro-analysis and melt inclusion Raman mapping on multi-stage apatite (Ap) samples from the Dangba large spodumene pegmatite deposit (NW China). The apatite samples are categorized into magmatic Ap1, transitional Ap2, hydrothermal Ap3a, and Ap3b based on the presence of exclusive melt, coexisting melt/fluid, liquid-rich, and vapor-rich fluid inclusions, respectively. The observed increase in Li content from Ap1 (median 43.4 ppm) to Ap2 (median 92.1 ppm) can be attributed to melt-melt immiscibility and subsequent fluid exsolution, as evidenced by the occurrence of coexisting water-rich/-poor melt and fluid inclusions. Furthermore, the significant surge in Li content from Ap2 to Ap3a (median 364 ppm) may result from fluid-fluid immiscibility, supported by the presence of coexisting liquid- and vapor-rich fluid inclusions, complementary negative (Ap3a) and positive (Ap3b) Eu anomalies in the chondrite-normalized rare earth element (REE) patterns, and the lowest Li contents found in Ap3b (median 12.3 ppm) among all apatite types. Considering the partition coefficients of Ap-melt (DLiAp/melt < 0.05) and Ap-fluid (DLiAp/fluid << 0.05), both the melts and fluids associated with Ap2 and Ap3a contain sufficient Li content for spodumene saturation. In conclusion, our findings highlight the significant role of liquid immiscibility in the extreme enrichment of lithium during the formation of granitic pegmatites.

How to cite: Chen, X.-D. and Chen, B.: Extreme enrichment of lithium in granitic pegmatite by liquid immiscibility, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20409, https://doi.org/10.5194/egusphere-egu24-20409, 2024.

As conventional hydrocarbon resources become depleted and theoretical innovations in hydrocarbon exploration advance, unconventional resources have gained substantial attention from researchers and explorers in recent decades. In the global energy consumption structure, unconventional shale gas progressively assumes a crucial role in the overall energy landscape. This research is motivated by the high probability of deriving gas accumulations encountered in drilling on the northwestern Anatolia (Akcakoca area) offshore from Paleozoic-aged rocks. Studied black shales from the Silurian Findikli Formation in the Sakarya region of northwestern Anatolia are one of the alternative unconventional resources.

Working with outcrop samples, this work evaluates the unconventional gas potential by performing geochemical characterization of these black shale samples. Studied samples were analyzed by Rock-Eval Pyrolysis. The present-day total organic carbon (TOCpd) contents range from 0.54 to 1.57 wt.%. High Tmax (up to 504oC) and low Hydrogen Index (HI) values (4-38 mg HC/g TOC) indicate that these shales are thermally over-mature and seem to be a spent hydrocarbon source rock. The remaining hydrocarbon generative potential (S1+S2) of 0.06–0.49 mg HC/g rock also supports this assessment. The recent organic matter type is Type IV kerogen which can yield limited gas products plotting on the H/C versus O/C atomic ratios on the modified Van Krevelen diagram. According to the interpretive of shale gas potential parameters based on Jarvie’s equation reconstructed these black shales originally may have good to very good source rock potential, with the calculated average original values of TOCo being 1.72 wt.% and HIo is 448 mg HC/g TOC. It can be concluded that the characteristics of studied shales seem to be nearly compatible with those of Utica shales in terms of the hydrocarbon generative potential. The studied black shales have lost 95% of their original hydrocarbon potentials, and seem to be a spent hydrocarbon source rock, indicating good risk for gas. However, the source rock may be very deep and deformed from the past to the present day, considering the paleogeographical location and geological evolution of the study area. Further research is required.

Keywords: Unconventional Gas Potential, Source Rock, Geochemical Characteristics, Silurian Black Shales, Northwestern Anatolia (Türkiye)

How to cite: Doner, Z.: Unconventional Gas Potential of Black Shales from Silurian Findikli Formation in northwestern Anatolia, Türkiye: Characterization of Geochemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-738, https://doi.org/10.5194/egusphere-egu24-738, 2024.

EGU24-820 | ECS | Orals | ERE4.1

Machine Learning-based Mineral Prospectivity Mapping: Exploring the Role of Negative Training Labels to Enhance Predictive Models 

Nyah Bay, Kyubo Noh, Mohammad Parsasadr, and Andrei Swidinsky

Mineral Prospectivity Mapping (MPM) is an important tool to identify areas with significant potential to host mineral deposits. Recent advancements in computational sciences, especially the advent of Machine Learning (ML), have enhanced MPM's capabilities. ML techniques enable a higher degree of data integration and extraction compared to traditional statistical methods such as Weights of Evidence, enhancing the accuracy and efficiency of identifying mineral exploration zones. When using ML techniques for MPM, the influence of negative training labels (ie. barren areas with no mineralization) remains a neglected research area, and this study investigates the influence of such label selection to optimize predictive models for Canadian critical mineral exploration.

Previous approaches to ML-based MPM often adopted a random assignment of negative training labels wherever positive training labels were absent. This study aims to refine this method, striving for a more systematic approach in negative label selection. The evolution of MPM, transitioning from traditional statistical methods to modern ML algorithms, signifies a shift towards heightened accuracy and efficiency. Prior research underscores the importance of balanced representation between mineralized and non-mineralized labels in ML models. Techniques such as Synthetic Minority Over-Sampling (SMOTE) and Positive and Unlabelled Learning (PUL) have been highlighted in previous studies, emphasizing the necessity of effectively handling negative training labels to prevent biases and enhance model performance. While SMOTE and PUL synthetically balance datasets by either oversampling minority classes or considering only positive and unlabeled instances, this study focuses on leveraging public exploration data to identify real negative training labels and provide a more authentic representation of non-mineralized areas without synthetic augmentation.

Using datasets compiled by the Geological Survey of Canada containing discoveries & occurrences of magmatic Ni (±Cu ±Co ±PGE), this research incorporates geological, geochemical, and geophysical data from established sources. Public exploration data will be used to identify areas devoid of magmatic Ni (±Cu ±Co ±PGE). These locations will serve as negative training labels for this study. Our particular choice of ML model is a Gradient Boosting Machine (GBM), and validation involves comprehensive evaluation techniques such as confusion matrices and receiver operating characteristic curves to assess model performance.

How to cite: Bay, N., Noh, K., Parsasadr, M., and Swidinsky, A.: Machine Learning-based Mineral Prospectivity Mapping: Exploring the Role of Negative Training Labels to Enhance Predictive Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-820, https://doi.org/10.5194/egusphere-egu24-820, 2024.

EGU24-1272 | Orals | ERE4.1

Geochemical behavior of gold and critical metals in the Goongarrie Ni-laterites, Western Australia 

Walid Salama, Louise Schoneveld, and Michael Verrall

The Goongarrie South, situated northwest of Kalgoorlie in Western Australia, hosts a global resource (60Mt) of lateritic Ni-Co deposits at 1% Ni and 0.07% Co. The Goongarrie lateritic Ni-Co deposit extends over a strike length of 7.5 km and averages approximately 800m in width and 40m in thickness. These deposits originated from the weathering of serpentinized dunite. The lateritic profile is subdivided into lower saprolite, dominated by carbonate, talc, serpentine, chlorite, and mica, and upper ferruginous saprolite, representing the economic Ni-Co laterite, and dominated by goethite and hematite. The ultramafic index of alteration (100 x [(Al2O3+Fe2O3(T)/(SiO2+MgO+Al2O3+Fe2O3(T)]) for the Ni-Co laterite is >60, contrasting with <60 in the lower saprolite and saprock. The laterite profile thickens up to 120 m over shear zones. In this study, we investigated the geochemical behavior of gold and some critical metals (REE, PGE, Sc, Ni, Cr, Mn, Co) in the Goongarrie South lateritic nickel deposits, using bulk and in-situ mineralogical, and geochemical methods. Our results show that gold and critical metals are concentrated in different horizons of the lateritic profile. Gold underwent leaching by acidic, halogen-rich, hypersaline groundwater, and has been enriched near the contact between the Ni-Co laterite and lower saprolite and saprock over shear zones, where the pH gradient increased. Additionally, gold is concentrated in paleoredox fronts within the Ni-Co laterite. The Au mineralization is Ag-poor, and occurs as cavity-filling, microcrystalline grains, and aggregates, indicating its supergene origin. Laser ablation ICP-MS mapping indicates that Ni was released from olivine in the lower saprolite and reprecipitated in nimite (Ni chlorite), while Sc is concentrated in serpentine and mica in the lower saprolite. In the Ni-Co laterite, Cr, Ti, V, Sc, Sb, and Y remained immobile; these elements are bound to Fe oxides and clays. Mobile elements such as Ni, Co, Li, Mo, W, Zn, Ce, Ru, and Pb are associated with Mn oxides at the base of the lateritic profile. The ΣREEs content in the laterite profile reaches up to 375 ppm. Cerium shows a weak positive correlation with the rest of REE, while positive Ce anomalies are associated with zones of Mn and Ce oxide enrichment. While there is no known magmatic sulfide mineralization associated with the host rock, chromite with Ru <0.15 ppm and inclusions of gold, Ni-Co-Cu-PGE-bearing sulfides, and sulfarsenides emerge as potential indicators for sulfide saturation. 

How to cite: Salama, W., Schoneveld, L., and Verrall, M.: Geochemical behavior of gold and critical metals in the Goongarrie Ni-laterites, Western Australia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1272, https://doi.org/10.5194/egusphere-egu24-1272, 2024.

EGU24-2491 | Orals | ERE4.1

Assessment of geophysical methods in the discovery of karst bauxite deposits in the Dinarides 

Franjo Šumanovac, Josipa Kapuralić, Luka Perković, and Ivica Pavičić

 

Geophysical exploration was carried out on karst bauxite deposits in the Posušje area in Bosnia and Herzegovina, which generally represent the problem of researching bauxite deposits in the Dinarides and similar geological models in the Mediterranean. Karst-type bauxite deposits are found in very complex geological models and were deposited in depressions in carbonate bedrock during numerous emersions on the Adriatic carbonate plate. Carbonate or clastic rocks can be found as the hanging wall of the deposits. Due to the complex lithological and structural relations, very irregular shapes of the deposits and their relatively small dimensions, the discovery of karst-type bauxite deposits is a very demanding geophysical task. That is why the published literature falls short in offering solutions for this very complex problem. So, the fundamental question is whether very irregular bauxite deposits whose dimensions are generally small can be detected by geophysical exploration?

Basic near surface geophysical methods, electrical resistivity tomography and seismic refraction, as well as magnetometry were applied in the exploration, which was carried out in two phases. In the first phase, geophysical methods were applied to already discovered bauxite deposits in order to determine whether geophysical responses correlate with bauxite deposits and to evaluate the efficiency of each method. Geophysical measurements were performed at several microlocations, and in the area of Mratnjača were carried out immediately after the deposit discovery, which was subsequently mapped with a very dense network of exploratory boreholes and was very well defined. In the second phase, measurements were performed in an microlocation selected by geological prospecting in order to discover potentially new bauxite deposit.

The characteristic responses of bauxite deposits are expressed on the resistivity models of tomographic profiles as zones of lower resistivities within carbonate rocks, and on the velocity models of refraction profiles as velocity inversions. The responses are much clearer on resistivity models, so the electrical tomography should be considered as a fundamental method in the exploration of karst bauxite deposits. Seismic refraction can contribute to a better characterization of deposits and reduce the interpretation ambiguity, thereby increasing the efficiency of geophysical exploration. In the last case, the electrical tomography can be applied independently to give satisfactory exploration results. On the other hand, the seismic refraction should be combined with the electrical tomography, because in some cases the depth coverage is greatly reduced due to distinct velocity inversions. Unfortunately, magnetometric measurements showed there are no magnetic anomalies that could be associated with bauxite deposits, that is, there are no magnetic minerals in the deposit.

Acknoledgments

This exploration was carried out in the AGEMERA project (Agile Exploration and Geo-modelling for European Critical Raw Materials) which has received funding under the European Union's Horizon Europe research and innovation programme under grant agreement No 101058178.

How to cite: Šumanovac, F., Kapuralić, J., Perković, L., and Pavičić, I.: Assessment of geophysical methods in the discovery of karst bauxite deposits in the Dinarides, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2491, https://doi.org/10.5194/egusphere-egu24-2491, 2024.

EGU24-3882 | ECS | Orals | ERE4.1

The delineation of graphite deposits in Lower Austria using the Transient Electromagnetic method 

Jorge Luis Monsalve Martinez, Lukas Aigner, Adrian Flores-Orozco, Clemens Moser, Philipp Högenauer, and Alexander Römer

The European Commission classifies graphite as a critical raw material, given its importance in refractory and high-tech applications, including the production of lithium-ion batteries. Many of Austrias graphite deposits are situated in and around the so-called “Drosendorf-Deckensystem” in Lower Austria. As those sites have been extensively mined out in the near-surface and are heavily weathered, the current interest of the potential assessment primarily focuses on the spatial extent of the graphite deposits, with particular interest in the deep continuation of these graphite deposits. Geological cross-sections are a standard approach for understanding subsurface graphite distribution, relying on available structural, geochemical, and/or lithological data. However, such information is primarily derived from surface observations, limited to exposed surfaces or outcrops. Geophysical methods can play a crucial role in extending the interpretation of geological cross-sections both horizontally and vertically. Due to the high electrical conductivity of graphite, electromagnetic and electrical methods like the Transient Electromagnetic (TEM) and the Induced Polarization (IP) are commonly applied for exploration. The IP method complements traditional electrical resistivity methods by measuring not only subsurface conductivity but also variations in the electrical capacitive properties (polarization) at low frequencies. In this study, we explore the feasibility of integrating the interpretation of IP and TEM measurements. The latter is known for its cost-effective coverage of large areas with high resolution and depth of investigation, compared to other geophysical methods. For that purpose, multiple TEM soundings were acquired in a ca. 4 km long profile between Berging and Kochholz in Lower Austria, situated in the geological section called “Drosendorf-Deckensystem”. The inversion of TEM data revealed distinct high-conductivity anomalies (100 – 200 mS/m) at approximately 40 m depth, attributed to the presence of graphite. A parallel comparison with two 160 m – 250 m long Time-Domain IP profiles confirms the graphite presence, attributed by high conductivity and high polarization (σ’ > 200 mS/m, σ” > 20 mS/m). Integrating these results along a geological cross-section improved the delineation and understanding of graphite deposits at depth and their correlation with lithological features in Lower Austria. Furthermore, these findings confirm that acquiring physical property models related to TEM and IP surveys has the potential to enhance mineral exploration.
This research work was co-financed by the Federal Ministry of education, science and research and supervised by the Federal Mining Authority of Austria within the framework of the VLG83 project (Raw Material research initiative).

How to cite: Monsalve Martinez, J. L., Aigner, L., Flores-Orozco, A., Moser, C., Högenauer, P., and Römer, A.: The delineation of graphite deposits in Lower Austria using the Transient Electromagnetic method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3882, https://doi.org/10.5194/egusphere-egu24-3882, 2024.

EGU24-4856 | Posters on site | ERE4.1

Multiple suppression for marine seismic data with strong shielding layer 

Jiajia Yang, Xiaojie Wang, Huaning Xu, Hong Liu, Zhonghui Yan, and Jianwen Chen

The study of multiple wave suppression methods has always been a difficulty of marine seismic data processing. At present, multiple wave suppression methods can be roughly divided into two categories: the first type is filtering methods, the second type is the wave dynamics and kinematic theory method. When the water depth in the study area is shallow, and strong seabed oscillations are formed between the seabed and the sea surface. The surface multiple suppression method (SRME) is not ideal for suppressing such short period seabed multiples. The deterministic seabed multiple prediction method (DWMP) can more accurately predict shallow water seabed periodic multiples. Long period multiples other than seabed multiples require surface multiple prediction (SRME) to suppress multiples.

When the research area is not only shallow in water depth, but also has a strong wave impedance interface in the formation, the difficulty of suppressing long-period multiples further increases. This is because various types of strong energy multiples, such as surface multiples, seabed multiples, and interlayer multiples, are formed between the sea surface and the strong wave impedance interface. The energy of multiples is one order of magnitude higher than that of weak effective reflections below the strong wave impedance interface. The strong energy of wide-angle multiples in the mid to far triangular region affects the effective utilization of reflected waves at mid to far offset distances. Diffraction multiples are developed in areas with severe fluctuations in the impedance interface of strong waves. Diffraction multiples are difficult to suppress using conventional multiples, and strong energy diffraction multiples can produce migration phenomena, affecting imaging in mid to deep layers. The effective suppression of various multiples is the key and difficult point in seismic data processing under strong shielding layer conditions.

Based on the characteristics of multiples under strong shielding layer conditions in shallow water, targeted suppression strategies were studied: using three methods to predict multiple wave models: deterministic seabed multiple prediction, deterministic seabed multiple prediction and surface multiple prediction, and surface multiple prediction. Firstly, frequency division combined with adaptive subtraction was used to achieve simultaneous suppression of short period seabed multiples and long period surface multiples. Then, application of CMP domain for high precision radon removal of multiples with dynamic calibration time difference. Finally, residual multiple suppression method is applied in the common offset domain to remove strong energy diffraction multiples. Through the suppression strategy proposed in this article, various types of multiples under the conditions of shallow water strong shielding layers can be effectively suppressed, thereby obtaining weak reflection signals in the middle and deep under the strong shielding layer. Through the calculation examples in the study area, it can be seen that the suppression strategy proposed in this article can suppress multiples interference while protecting effective reflection information. It is of great significance for imaging inside buried hill, imaging under volcanic shielding layers, and imaging under gypsum-salt layer.

How to cite: Yang, J., Wang, X., Xu, H., Liu, H., Yan, Z., and Chen, J.: Multiple suppression for marine seismic data with strong shielding layer, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4856, https://doi.org/10.5194/egusphere-egu24-4856, 2024.

EGU24-6515 | Posters on site | ERE4.1

Towards AI-driven real-time deposit modeling: a case study in southern Brazil 

Ítalo Gonçalves and Everton Frigo

Mineral exploration and resource estimation play pivotal roles in the mining industry, driving the need for accurate and comprehensive data about mineral deposits. Traditionally, drill core samples have been the primary means of obtaining crucial information regarding the size, shape, and mineral composition of deposits. However, the cost associated with drilling limits the number of samples that can be acquired, posing challenges to achieving a thorough understanding of a mineralized area. In response to these challenges, the mining industry is increasingly turning to cutting-edge technologies to enhance exploration efficiency and reduce costs, such as aerial photogrammetry, hyperspectral imaging, and core scanning. These technologies offer the advantage of acquiring data over larger areas in a relatively short period, providing valuable insights into the geological characteristics of a site. In the context of developing mines, each round of blasting uncovers fresh rock surfaces that harbor new geological information. Leveraging this opportunity to gather real-time data presents an exciting prospect for optimizing mineral exploration. By systematically collecting and processing information from newly exposed surfaces, it becomes possible to enhance the insights obtained from conventional core samples. This research introduces a case study exemplifying the implementation of this paradigm shift in a marble quarry located in southern Brazil. Here, a convolutional neural network is employed to interpret geological features in aerial photographs. Subsequently, the interpreted data is fed into a photogrammetry software, generating a labeled point cloud that complements information derived from traditional core samples. The synergy between aerial data and core sample information allows for the creation of highly detailed lithology models, enabling more accurate short-term forecasting of stripping ratios. A key aspect of this work involves the development and utilization of an in-house Gaussian process implementation for lithological modeling. This technique not only provides insights into the size and shape of the orebody but also offers an invaluable uncertainty estimate. The results from this case study demonstrate the potential of this paradigm shift in mineral exploration and mining practices. Ultimately, this research aims to showcase a pathway towards a more economical, environmentally friendly, and sustainable future for the mining industry.

How to cite: Gonçalves, Í. and Frigo, E.: Towards AI-driven real-time deposit modeling: a case study in southern Brazil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6515, https://doi.org/10.5194/egusphere-egu24-6515, 2024.

EGU24-6901 | ECS | Orals | ERE4.1

Predicting global porphyry copper prospectivity using positive-unlabelled machine learning 

Christopher Alfonso, Dietmar Müller, Ben Mather, and Tristan Salles

The majority of the world’s known copper reserves is contained in porphyry copper deposits. These deposits are understood to form along subduction zones within the magmatic arc, though the exact contributions to this process of different factors within the subducting and overriding plates are not entirely certain, hampering efforts to develop large-scale prospectivity models for this deposit type. Previous efforts to tackle this problem through the use of data-driven machine learning methods have shown promise, but have been hindered by the relative paucity of fully labelled data required for training classification models. Here we present a suite of models trained using a semi-supervised positive-unlabelled (PU) algorithm, allowing the classifier to be created from data of which only a small subset of one class is labelled: in this context, known porphyry copper deposit locations. These models can be used to create time-dependent prospectivity maps representing the probability of a deposit forming at a given place and time, while model inspection can provide deeper insight into the processes behind the genesis of these deposits, at both a global and regional scale. Furthermore, deep-time erosion rate estimates extracted from global landscape evolution models are used to explore the uplift and erosion histories of known porphyry copper deposits in order to better understand the potential for these deposits to survive to the present day. These two factors of deposit formation and preservation are combined into a powerful prospectivity model, with the potential to facilitate the identification of possible new prospective zones along the world's subduction zones through time and help minimise the environmental and financial costs of mineral exploration.

How to cite: Alfonso, C., Müller, D., Mather, B., and Salles, T.: Predicting global porphyry copper prospectivity using positive-unlabelled machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6901, https://doi.org/10.5194/egusphere-egu24-6901, 2024.

EGU24-7758 | Orals | ERE4.1

FIELD VNIR-SWIR SPECTRORADIOMETRY FOR CLASSIFICATION OF MATERIALS IN THE VALDEFOREZ DEPOSIT (SPAIN) ACCORDING TO THE Li CONTENTS. 

Emilia García Romero, Santos Barrios, David Valls, and Mercedes Suárez

The Li mineralization of Valdeflórez (Cáceres province, Spain) is related to an extensive metasomatism of Ordovician metasedimentary rocks due to the circulation of B- and Li-rich magmatic hydrothermal fluids associated probably with a granite dome (Torres-Ruiz, et al., 1996). Li-rich micas mainly, and other Li-rich minerals like amblygonite-montebrasite, appear as consequence of this hydrothermal alteration. The aim of this study is to evaluate the use of the VNIR-SWIR spectroradiometry to the materials classification according to the Li content during the exploitation mining works and to the mining prospection in similar areas. The results of a study conducted by VNIR-SWIR portable spectroradiometry on 335 samples coming from representative cores of the mineralized area are shown. Complementary, a mineralogical study by XRD and chemical analysis by ICP were performed. Visible and infrared wavelength ranges were studied separately, and a classification of the high-resolution spectra was done to compare with the chemical and mineralogical composition of the samples. The spectra were classified into six groups according to their morphology in the near and short-wave IR range, and these groups correspond to a different mineralogy of major components, as logical.  However, there is not a clear relation among these groups and the Li-content because Li is mainly in micas as octahedral substitutions, which influence on the spectral features is neglectable. A higher content in micas does not imply a higher content in Li. Consequently, a spectral signature of Li could not be determined, because Li is not directly related to the content of a certain mineral, micas in this case. As a conventional spectral signature is not useful in this case, because it classified mineralogy but not Li-content, a detailed study of the hight resolution spectra obtaining different parameters (both from the spectra and from the second derivatives of the spectra) was performed. The joint statistical treatment of the hyperspectral, mineralogical, and chemical data allowed us to find a plot of the materials classification according to the Li content from the spectral data which means a very fast procedure for classification that could be automatized though IA.

Acknowledgement: TED2021-130440B-I00 funded by MCIN/AEI/10.13039/501100011033 and European Union NextGenerationEU/PRTR

Torres-Ruiz, J., Pesquera, P., Gil, P., Casas, J. 1996. Tourmalinites and Sn-Li mineralization in the Valdeflores area (Cáceres, Spain). Mineralogy and Petrology 56:209-223.

How to cite: García Romero, E., Barrios, S., Valls, D., and Suárez, M.: FIELD VNIR-SWIR SPECTRORADIOMETRY FOR CLASSIFICATION OF MATERIALS IN THE VALDEFOREZ DEPOSIT (SPAIN) ACCORDING TO THE Li CONTENTS., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7758, https://doi.org/10.5194/egusphere-egu24-7758, 2024.

EGU24-7868 | ECS | Posters virtual | ERE4.1

Advanced Computational Analysis of Roof Stability in Highwall Phosphate Mining Operations 

Mohamed Yassir Sadki, Murat Karakus, Khalid Amrouch, Bouazzaoui Eljabbar, and Abdelhadi Khaldoun

Abstract:
Strip mining is typically preferred for near-surface, tabular deposits such as phosphate. 
Khouribga, home to Morocco’s largest phosphate deposit, contributs significantly to the 
nation’s phosphate output. However, a slight dip in the phosphate deposit suggests that strip 
mining may become less viable in the future. To sustain phosphate production efficiently, 
transitioning from surface to underground mining through highwall mining could be an 
effective solution. This method, involving the recovery of phosphate using continuous miners, 
necessitates stable roof conditions.
To evaluate roof stability in highwall mining, both with and without web pillars, we will employ 
a three-dimensional finite difference method. Firstly, field rock mass properties, including joint 
frequency, persistency, infills and orientations and mechanical parameters, will be determined 
for inclusion in the numerical model. The generalized Hoek-Brown failure model, in 
conjunction with the Geological Strength Index (GSI), will be utilized to analyze rock mass 
behavior. For intact rock behavior, triaxial tests will be conducted to acquire Hoek-Brown 
failure parameters. These parameters will inform the construction of realistic 3D models using 
FLAC3D software, enabling the simulation of various underground working scenarios to 
identify the optimal mine layout that ensures high production rates and minimizes roof stability 
issues.
An economic analysis will also be conducted to assess the feasibility of this method. This 
analysis will help in optimizing the dimensions of highwall mining parameters and selecting 
the best scenario through the Mineable Shape Optimizer (MSO). This planning tool will 
additionally aid in forecasting the recovery and dilution rates associated with the 
highwall mining method.
Keywords:
Highwall mining, Phosphate, Khouribga, Roof stability, GSI, Rock mass classification, HoekBrown failure model, Economic analysis, MSO

How to cite: Sadki, M. Y., Karakus, M., Amrouch, K., Eljabbar, B., and Khaldoun, A.: Advanced Computational Analysis of Roof Stability in Highwall Phosphate Mining Operations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7868, https://doi.org/10.5194/egusphere-egu24-7868, 2024.

EGU24-7969 | ECS | Orals | ERE4.1

Predicting petrophysical properties from hyperspectral borehole data 

Akshay Kamath, Moritz Kirsch, Samuel Thiele, and Richard Gloaguen

Recent research has highlighted significant correlations between hyperspectral data and the petrophysical properties of geological formations. Petrophysics acts as the link between geology and geophysics, and is crucial for constraining geophysical inversions, regional characterisation and mineral exploration. In this study, we employ various machine learning methods to predict P-Wave velocities using hyperspectral borehole data, with a focus on cross-validation between different boreholes in the same region. Our dataset includes 4022 paired observations of P-wave velocities, obtained from downhole sonic logging in one borehole, and corresponding hyperspectral data spanning visible-near (380–970 nm), shortwave (970–2500 nm), midwave (2700–5300 nm), and long-wave (7700–12300 nm) spectra, averaged over a 10 cm x 5 cm area. We utilised principal component analysis (PCA) for dimensionality reduction. The initial PCA stage extracted 10 principal components from each sensor type, which were then integrated. A subsequent PCA stage was conducted to reduce inter-sensor correlation, yielding 10 composite features that represent the variability across the complete VNIR-LWIR spectrum.

To validate our model, we conducted tests using 1160 pairs of analogous measurements from a different borehole within the same geological region. The model demonstrated impressive predictive capabilities, particularly with Support Vector Regression (SVR) and Artificial Neural Networks (ANN). The test set yielded R2 scores of 0.758 for SVR and 0.811 for ANN, indicating strong predictive accuracy. Building upon this success, our future work will expand the scope of prediction to include various other petrophysical properties critical to geophysical characterization and mineral exploration, such as S-Wave velocity, magnetic susceptibility, and rock density, properties which are critical for geophysical characterization and mineral exploration.

How to cite: Kamath, A., Kirsch, M., Thiele, S., and Gloaguen, R.: Predicting petrophysical properties from hyperspectral borehole data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7969, https://doi.org/10.5194/egusphere-egu24-7969, 2024.

On a global level, clean transition, energy transition and electrification of transport, among other things, require a lot of strategic or critical raw materials. In Europe, too, the importance of increasing the self-sufficiency of raw material production has come to light in order to secure the operating conditions of industry supporting the green transition.

For promoting the sustainable use of raw materials in Eastern and Northern Finland, it has been decided to intensify cooperation between regional, national and international actors.

In the regional level, the development of the mineral industry is carried out by the regional Mining Hubs. Nationally, it will be significant in Finland during 2024 to develop a new mineral strategy to promote the growth of the mineral and battery cluster in order to enable a clean and digital transition. The aim of the new strategy is to produce a common view of the current situation of the Finnish mineral cluster, policy objectives, main lines and necessary measures, including the development of a circular economy. At the European level the new Critical Raw Materials Act aims to ensure the EU's access to a secure, diversified, affordable and sustainable supply of critical raw materials and also strengthening Europe's strategic autonomy.

Between the actors of regional, national and EU level, the R&I and training organisations play a key role in developing cooperation. In the Eastern and Northern Finland region, the Geological Survey of Finland, the University of Oulu, Kajaani University of Applied Sciences and The Federation of Education in Central Ostrobothnia have decided to join forces to enable this collaboration. A special tool for this is the JTF project “Development of the mining sector in Lapland, Northern Ostrobothnia, Kainuu and Central Ostrobothnia” (KAKE).  The planned measures include e.g. international networking, competence development, workshops, innovating new R&I projects and linking companies to project activities.

How to cite: Pihlaja, J.: Development of mineral sector cooperation in Eastern and Northern Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10182, https://doi.org/10.5194/egusphere-egu24-10182, 2024.

The Mineral Prospectivity Mapping (MPM) methodology can be used to delineate favorable mineral exploration areas and minimize time and costs. The mineral deposits in Finland are an ideal testing ground for these methods due to limited outcrops, thick overburden because of soil cover and dense vegetation and snow cover during long winters. Here, we apply MPM to predict favorable areas for Iron Oxide-Copper-Gold (IOCG) deposits in the Kolari region, northwestern Finland. We use a GIS-based knowledge-driven approach (fuzzy logic overlay), which is integrating evidential layers derived from geological (scale-free geology map), geochemical (till and bedrock samples), and geophysical data (magnetic, radiometric, electromagnetic measurements and gravity worms). The regional-scale analysis aimed to evaluate various mineral system components specified for IOCG deposits, including the anomalies of elements in till and rock geochemistry (i.e., Au, Cu, Co, Fe, and Th), pathways, energy sources/drivers, traps, and the relevant geological factors influencing the ore-forming processes. Utilizing the Centered Log-Ratio transformation (CLR) proves beneficial in enhancing the identification of weak anomaly areas and improving the prospectivity assessments by directing attention to relevant geological features. The produced prospectivity map shows a positive association between known IOCG deposits and high-favorability areas, and it also indicates new promising targets. Receiver Operating Characteristic (ROC) analysis and average Area Under the Curve (AUC) values consistently yielded scores > 0.7 which could be considered favorable outcomes (promising targets).

How to cite: Khammar, F.: Translating mineral systems criteria into a prospectivity model; Kolari region, Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12082, https://doi.org/10.5194/egusphere-egu24-12082, 2024.

EGU24-12933 | ECS | Orals | ERE4.1

In situ Rhenium (Re) quantification by pXRF in Molybdenite from porphyry-epithermal deposits (Thrace, NE Greece) 

Marjolène Jatteau, Jean Cauzid, Alexandre Tarantola, and Panagiotis Voudouris

Even if natural occurrence of Re can be found as rheniite (ReS2), most Re substitutes to Mo in molybdenite (MoS2), which explains why Re is usually a by-product of Cu-Mo deposits. In Thrace region (NE Greece), molybdenite can be enriched up to 4.7 wt% in Re in porphyry-epithermal deposits (Voudouris et al., 2013). Now, spectroscopic portable tools (e.g. pXRF) allows to directly detect Re in the field. First qualitative results obtained by pXRF show that is possible to know in which deposits from Greece the molybdenite is the most enriched without the necessity of long and costly laboratory measurements (EDS-SEM or EPMA). The X-250 pXRF (SciAps) used in this study do not include Re in its quantification program. Moreover, the spot diameter (4 mm) is generally larger than the molybdenite size in this area. Hence, Re cannot be quantified and even if it were, the value would be that of Re in the analytical spot and not in molybdenite only. The aims of this study is to (1) directly quantify Re with the pXRF and (2) determine the concentration in Re within the molybdenite.

In Energy-dispersive XRF, there is an interference between the Zn-Kα emission line (8.6389 keV) and the Re-Lα emission line (8.6524 keV). If Zn is quantified and Re not included into the analytical program, the Re signal will be interpreted as Zn quantities. That is the case with our X-250 pXRF. In Thrace region, molybdenite occurs in quartz veins sometimes associated with few feldspar or pyrite but no Zn-bearing minerals. When measuring molybdenite-bearing veins, all the Zn quantitatively measured by the pXRF corresponds to a Re signal. That effect can be corrected by applying a correction factor on the Zn value to convert it into a Re quantity in situ by using calibration curves. A specific user method can also be easily implemented into the tool. In case Zn-bearing minerals are also found in the molybdenite-bearing veins, the in situ method requires a multilinear correction of signal obtained from the ROIs of Zn and Re. That is more difficult to implement and in the meanwhile, one can obtain signals from Zn and Re separately by proceeding to spectral decomposition using the PyMCA software (Solé et al., 2007). Once separated, these signals can be converted into concentrations of each elements with calibration curves. These curves have been built from the measurement of reference samples consisting in chosen proportions of SiO2 (considered as the matrix), MoS2, Re and Zn powders. That enabled to evaluate the impact of each parameter on detection limit, precision and accuracy of the Mo, Re and Zn concentrations. The calibration curves were tested by the use of a set of validation samples.

In our case study, Re and Mo are only within molybdenite. The quantity of Re in the analysed area is mainly induced by the quantity of molybdenite, thus Mo, in the same area. The effect of Re-enrichment in molybdenite appears as a second order phenomenon. With these developments, Re-enrichment in molybdenite becomes a mapable parameter.

How to cite: Jatteau, M., Cauzid, J., Tarantola, A., and Voudouris, P.: In situ Rhenium (Re) quantification by pXRF in Molybdenite from porphyry-epithermal deposits (Thrace, NE Greece), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12933, https://doi.org/10.5194/egusphere-egu24-12933, 2024.

    The Wenchang Formation and Enping Formation in the Pearl River Mouth Basin have huge oil and gas potential, but the migration and accumulation characteristics are not clear, which seriously restricts the large-scale exploration and development of oil and gas.In combination with thin section,scanning electron microscope and high-pressure mercury injection, physical modeling experiments of oil charging were conducted to find out laws and affecting factors of oil migration and seepage in reservoirs using core samples from reservoir beds of the Wenchang formation and Enping formation in Zhu-I Depression, Pearl River Mouth Basin. The growth curve of oil saturation presents three stages: rapid growth, slow growth and stabilization, and the final oil saturation ranges from 30% to 80%. Reservoir pore types are mainly intergranular pore, dissolution pore and fracture, and reservoir can be divided into three types: high porosity-high permeability, high porosity-low permeability and low porosity-low permeability. At the same time,The growth modes of oil saturation can also be divided into three types: Type Ⅰ is rapid speed growth-high saturation type, corresponding to high porosity-high permeability reservoir; The Type Ⅱ is medium speed growth- medium saturation type, corresponding to high porosity-low permeability reservoirs. The Type Ⅲ is slow speed growth-low saturation type, corresponding to low porosity-low permeability reservoir. The microscopic model diagram of oil charging shows that with the change of reservoir type from high porosity-high permeability to low porosity-low permeability, the main pore types of charging change from intergranular pore and dissolution pore to dissolution pore and fracture, and the growth mode of oil saturation also changes from type I to type III. The accumulation process and flow characteristics of crude oil are dominantly influenced by the injection pressure and pore structure of reservoirs.The injection pressure is a prerequisite for the increase of oil saturation,and pore structure is the main factor to control the growth pattern of oil saturation. Based on the experimental results,the relationship diagram of porosity-permeability- charging pressure-oil saturation is established. According to the distribution of residual pressure and the relationship diagram,the lower porosity-permeability limit of the reservoir to reach the specific oil saturation under different residual pressure can be determined. This is conducive to the dynamic analysis of oil and gas charging process and the prediction of oil saturation under different physical properties and dynamic conditions.

How to cite: zhao, X., liu, H., and liu, J.: Physical simulation on oil charging process and controlling factor in reservoirs of Wenchang formation and Enping formation in Zhu-I Depression, Pearl River Mouth Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13801, https://doi.org/10.5194/egusphere-egu24-13801, 2024.

EGU24-14928 | Orals | ERE4.1

Towards hyperspectral exploration vectors in the Central European Kupferschiefer district 

Moritz Kirsch, Samuel Thiele, Yuleika Madriz, Filipa Simões, Atilla Basoglu, Yonghwi Kim, and Richard Gloaguen

Europe holds significant potential for crucial metals essential for renewable energy and digital advancements. However, there is a need for a deeper understanding of the European subsurface, coupled with a requirement to reduce the environmental impact of exploration activities. We employ hyperspectral scanning of legacy drill cores to develop innovative indicators of mineralization in the Central European Kupferschiefer district, home to Europe's largest copper and silver resources. Hyperspectral imaging, capturing spectral reflectance and emission across numerous spectral bands, allows for non-invasive, high-resolution mineral mapping of drill cores. Initial findings showcased the technique's ability to identify critical redox boundaries and alteration minerals, aiding ore deposit characterization. In the framework of two research projects, we scanned 2400 meters of drill core from 87 boreholes across the Spremberg–Graustein Kupferschiefer deposit in Germany. For data acquisition, we deployed a drill-core scanner with a full suite of hyperspectral sensors covering the visible and near-infrared (400 to 970 nm), shortwave (970 to 2500 nm), mid-wave (2700 to 5300 nm), and longwave infrared (7700 to 12300 nm) ranges. The collected data were processed through a novel, open-source software pipeline, which enables i) real-time correction, processing, and analysis, ii) efficient data management and storage, and iii) comprehensive visualization and integrative interpretation of the hyperspectral drill core data. We upscaled mineral abundances across all of the scanned drill cores using a supervised learning model trained on quantitative mineralogical data from select samples. Initial analyses, particularly the visual alignment of hyperspectral derivatives at the base of the Kupferschiefer marker horizon, indicate geographical patterns in dolomite content and correlations between carbonate, clay, and mica compositions and copper grade. The hyperspectral data will eventually be integrated with geological, geophysical, and geochemical constraints to create accurate 3D subsurface and 4D mineral system models, aimed at enhancing our understanding of geological processes and resource management strategies in similar geological settings worldwide.

 

Acknowledgements: This research has received funding from the European Union’s Horizon Europe research and innovation programme under grant agreement nº 101058483 (VECTOR), and from the Geological Survey of Saxony (Sächsisches Landesamt für Umwelt, Landwirtschaft und Geologie, LfULG) under agreement nº 4-0912014LFULG01-88.

How to cite: Kirsch, M., Thiele, S., Madriz, Y., Simões, F., Basoglu, A., Kim, Y., and Gloaguen, R.: Towards hyperspectral exploration vectors in the Central European Kupferschiefer district, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14928, https://doi.org/10.5194/egusphere-egu24-14928, 2024.

EGU24-15110 | ECS | Posters on site | ERE4.1

Big data techniques for real-time hyperspectral core logging 

Samuel Thiele, Moritz Kirsch, Sandra Lorenz, and Richard Gloaguen

Hyperspectral imaging is gaining widespread use in the resource sector, with applications in mineral exploration, geometallurgy, and mine mapping. However, the sheer size of many hyperspectral datasets (>1 Tb), and associated data correction and analysis challenges, limit the integration of this technique into time-critical exploration and mining workflows. We present an overview of several newly developed  real-time processing capabilities to mitigate these challenges, and so provide hyperspectral data and derived products (e.g., mineral abundance estimates) in near real-time. This allows for efficient, timely, and automated delivery of hyperspectral data to enhance geological activities.

Hyperspectral data generally needs to be corrected, coregistered, cropped and masked, before derivative results can be generated, visualized and stored. To achieve real-time processing, each of these steps, which can involve the computationally intense manipulation of several Gb worth of spectral data, need to be completed within the 1-3 minutes a typical instrument or scanner takes to capture a data cube. To help with this, we have developed a python-based asynchronous processing pipeline, crunchy, that uses a file-discovery-based triggering mechanism to spawn parallel processing workflows that automatically perform these tasks. Coregistered and radiometrically corrected results are then stored using a directory-based data structure managed by a second python utility, hycore, that facilitates (1) consistent data storage, (2) file-based out-of-core processing, and (3) management of the various metadata required to localize and give meaning to hyperspectral drill core data. We have also developed a third python tool, hywiz, to enable an easy browser-based interaction with hycore databases. This includes the visualisation of sensor results and analysis products for individual trays and drillhole mosaics. Additional data such as assays, logging notes or downhole geophysical data can be overlain on these to enable integrated interpretation of otherwise disparate datasets. 

We hope that these tools will enable greater use of hyperspectral data in research and industry, and facilitate e.g., hyperspectrally enhanced core-logging, sample selection, vectoring and, potentially, realize self-updating 3-D geological models.

How to cite: Thiele, S., Kirsch, M., Lorenz, S., and Gloaguen, R.: Big data techniques for real-time hyperspectral core logging, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15110, https://doi.org/10.5194/egusphere-egu24-15110, 2024.

EGU24-15719 | Orals | ERE4.1

Challenges of in-line, sensor-based characterisation of recycling streams 

Margret Christine Fuchs, Sandra Lorenz, Yuleika Carolina Madriz Diaz, Andrea de Lima Ribeiro, Elias Arbash, Jan Beyer, Christian Röder, Nadine Schüler, Kay Dornich, Johannes Heitmann, and Richard Gloaguen

Optical sensors are a key enabler for an in-line, real-time characterisation, quality control and monitoring in industrial, conveyor-based raw material processing. Innovators are actively exploring non-invasive optical sensing to solve current problems in economic, socially acceptable and ecologic resource handling with high efficiency. Despite the evident advantages, integrating available optical technologies into sensor systems poses various challenges. A detailed understanding of physical parameters as well as smart solutions are required to mitigate or circumvent some of the limitations. Realistic solutions for the industry rely on understanding what is possible, where are the key limiting factors and which of the challenges can be overcome in the future.

In this contribution, we present four examples from our HELIOS lab research projects in the field of recycling of society-relevant material streams to discuss the major challenges. Our focus lies on the suitability of optical sensor systems for industrial applications. We emphasize the pathways from scientific setups to industrial demonstrators and highlight the relevant parameters, when operating sensors such as RGB, hyperspectral reflectance imaging (HSI), laser-induced fluorescence (LiF) together with Raman scattering, x-ray fluorescence (XRF) and laser-induced breakdown spectroscopy (LIBS).  

Extremely relevant to the industry is speed (or material throughput). Common conveyor belt speeds of several meters per second imply low signal integration times for the optical sensors (or high frame rates in the case of cameras). While industrial high-speed RGB cameras are well suitable, HSI cameras rely on longer integration times to collect signals with adequate intensities across hundreds of detection bands. Current HSI technology is successful in a variety of conveyor belt applications (2D dynamic setup) at a few meters per second, however, a transfer to applications for material detection in air flows (3D dynamic setup) outlines the trade-off between signal quality and acquisition speed. Similarly, signals of very low intensities as seen in laser-induced fluorescence hyperspectral scanning highlight the multi-parameter trade-off between integration times, acquisition speed and excitation power, where the latter is largely dependent on available optical components.

Most of our consumer products are not made of pristine, pure material but come with coating, as compounds and/or with additives to improve appearance and performance of the materials. For recycling, this poses significant challenges for material separation and processing. Using optical sensors in recycling operations then often implies extrapolating the surface properties as representative of the actual material. We demonstrate with examples from several projects, how coating and additives affect the spectral signatures in polymers (esp. black polymers) and metals (steel and aluminum), and how a combination with additional validation sensors (e.g. Raman, LIBS) can provide important information in materials. This information is essential for an adequate and high-quality recycling process.

The given examples and related research are based on collaborations with the industry and aim at developing and testing new concepts and evaluating corresponding tools for data acquisition and real-time processing in recycling facilities. We gratefully acknowledge project funding for RAMSES-4-CE (KIC RM 19262), Digisort (03XP0337B), Car2Car (19S22007B) and FINEST (KA2-HSC-10).

How to cite: Fuchs, M. C., Lorenz, S., Madriz Diaz, Y. C., de Lima Ribeiro, A., Arbash, E., Beyer, J., Röder, C., Schüler, N., Dornich, K., Heitmann, J., and Gloaguen, R.: Challenges of in-line, sensor-based characterisation of recycling streams, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15719, https://doi.org/10.5194/egusphere-egu24-15719, 2024.

EGU24-15856 | ECS | Orals | ERE4.1

Unveiling the temporal dynamics: A spatiotemporal prospectivity model for porphyry systems in Papua New Guinea and the Solomon Islands 

Ehsan Farahbakhsh, Sabin Zahirovic, Brent I. A. McInnes, Sara Polanco, Fabian Kohlmann, Maria Seton, and R. Dietmar Muller

The tectonic setting of porphyry systems is influenced by the subduction style and history that impact the distribution and concentration of copper (Cu), gold (Au), and molybdenum mineralisation. Typically linked to the intrusion of arc-related magma into the upper crust along subduction zones, the formation of porphyry ore deposits is currently understood primarily through geological and geophysical observations of the overriding plate, creating a knowledge gap regarding arc metallogenic processes in convergence zones over time. In this study, we address this gap by investigating the connection between the formation of porphyry Cu-Au deposits and the evolution of subduction zones, utilising a range of features derived from a plate motion model and oceanic crust age grids. Incorporating 47 Cenozoic intrusion-related Cu-Au deposits located in Papua New Guinea and the Solomon Islands, we employ a spatiotemporal mineral prospectivity framework that leverages advanced machine learning methods to map prospective arc terranes. The model successfully predicts all known mineral occurrences in the testing set and identifies the most important features for predicting potential areas of porphyry mineralisation.
We observe that the obliquity angle of the relative motion vector in subduction zones plays a crucial role in distinguishing between mineralised (highly prospective) and barren areas (low prospective). This feature is recognised for its significant influence on a spectrum of geological processes, encompassing fluid flow dynamics, magmatic processes, and stress regimes. This influence extends to the transport of mineralising elements and the creation of favourable conditions for ore deposition, with the range of 25 to 90 degrees correlating with mineralised zones, suggesting that oblique subduction zones are more likely to be rich in mineralisation in the study area. Additionally, the length and curvature of arcs emerge as important features for identifying mineralised areas, with tightly curved arcs associated with higher compressional stress and fractures facilitating magma ascent and porphyry formation. The orthogonal component of the downgoing absolute plate velocity is also identified as a significant feature, with higher magnitudes associated with mineralisation, indicating that rapid convergence rates are optimal for porphyry system formation due to accelerated metasomatism and partial melting processes in the overriding plate.
The seafloor spreading rate of the subducting crust, computed at the time when the crust originally formed, is an additional important feature linked to mineralised areas. This preferentially occurs when crust formed in the range of 25 to 55 mm/yr (half spreading rate) is subducted. At lower spreading rates, there is a higher proportion of serpentinised mantle peridotite, adding water and carbon to the plate, which will be expelled during subduction, contributing to increasing hydrous melting in the mantle wedge and acting as a catalyst for porphyry deposits. In conclusion, the performance of our model underscores the potential of integrating plate motion models and machine learning to advance mineral exploration along subduction zones. This approach holds promise for more efficient, accurate, and sustainable exploration strategies in these geologically active areas.

How to cite: Farahbakhsh, E., Zahirovic, S., McInnes, B. I. A., Polanco, S., Kohlmann, F., Seton, M., and Muller, R. D.: Unveiling the temporal dynamics: A spatiotemporal prospectivity model for porphyry systems in Papua New Guinea and the Solomon Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15856, https://doi.org/10.5194/egusphere-egu24-15856, 2024.

EGU24-16838 | Posters on site | ERE4.1

VNIR-SWIR spectral signatures of the Cu-Co-Ni mineralization and the host rocks of El Aramo (Asturias, España). 

Mercedes Suarez, José Daniel Ramírez, Ángel Santamaría, and Juan Morales

The mineralization of the Aramo Plateau is a carbonate-hosted deposit with major Cu-Co-Ni sulphides and arsenides and minor precious metals. There are a few studies on the deposit, but according to Paniagua et al., (1988), it is an epithermal mineralization with an evolutive sequence involving temperatures from 85ºC to 170ºC whose hydrothermal systems were related to the distensive Late-Variscan tectonic activity in the region. Weathering and oxidation of primary sulfides in ore and waste rock materials has resulted in the formation of secondary minerals such as goethite, hematite, malachite, azurite, and others, causing the release of elements, such as Cu or As, to soils, waters or stream sediments (Loredo et al., 2008).

This study is a part of the S34I project (Secure and Sustainable Supply of raw materials for EU Industry) which research and innovate new data-driven methods to analyze Earth Observation data, supporting systematic mineral exploration and continuous monitoring of extraction activities with the aim to increase European autonomy regarding raw materials. This work shows the preliminary results of a study conducted by X-ray diffraction and field VNIR-SWIR spectroscopy related to 1) the identification the mineralogical composition of a very wide group of representative samples from old mines in the area and from the surface of the Aramo Plateau, both outcropping rocks and soils; 2) the spectral response in the VNIR-SWIR wavelength range (the same range that hyperspectral remote sensors use); and 3) the determination of the spectral signatures of the different paragenesis of the mineralization, the host rocks and the soils in which supergenic processes could occur.

Financial support by S34I project (DOI: 10.3030/101091616) is acknowledged.

How to cite: Suarez, M., Ramírez, J. D., Santamaría, Á., and Morales, J.: VNIR-SWIR spectral signatures of the Cu-Co-Ni mineralization and the host rocks of El Aramo (Asturias, España)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16838, https://doi.org/10.5194/egusphere-egu24-16838, 2024.

EGU24-17303 | Orals | ERE4.1 | Highlight

First results from the SEEMS DEEP seismic survey conducted over the Koillismaa Igneous Complex, Northern Finland 

Brij Singh, Yousef Amirzadeh, Uula Autio, Andrzej Gόrszczyk, Suvi Heinonen, Michał Malinowski, and Marek Wojdyła and the SEEMS DEEP Working Group

The Koillismaa layered igneous complex (KLIC) in northern Finland spans a large distance from the Finnish-Swedish border to the Finnish-Russian border. It has been an area of interest for several decades among geologists due to its potential to host several critical raw materials including cobalt & nickel which are key materials required for lithium-ion batteries. The KLIC intrusion comprises outcropping Koillismaa and Näränkävaara layered complex mafic-ultramafic intrusions that are interestingly connected by a zone of high gravity and magnetic anomalies. Extensive petrophysical and lab studies were conducted by the Geological Survey of Finland on a 1.7 km long deep drillhole located within the area of our interest. A pre-existing low-fold seismic study indicated the reflectivity of the ultramafic rocks. Drillhole study further established the fact that the contacts with mafic intrusion rocks having the potential to host mineralization are causing observable seismic reflections at 1.4 km depth. The ongoing SEEMS DEEP project (2022-2025), an ERA-MIN 3 sponsored project comprises an integrated approach of using seismics and electromagnetics studies to substantially improve the geomodel of the Koillismaa area which will help in better decisions in exploration drilling. In this study, we are focussing on the seismic part of the project. In August 2023, an irregular-sparse 3D seismic and two regional 2D seismic lines, roughly in the direction of E-W and NNE-SSW were acquired under the SEEMS DEEP project. The overall aim of the 2D seismic lines was to constrain large-scale information about the geological architecture of the study area, whereas the 3D survey was conducted to highlight the detailed information from the rock volumes near the deep drill hole. The acquired data, both 2D (~10 Km and ~12 Km) and 3D (~5 Km x 6 Km), are of good quality with reflections visible in the raw data. An 8-tonne Mark IV Vibroseis truck was used as a seismic source for both surveys, with sweep frequency ending at 160 Hz. Almost 3000 single-component receivers (Strydes) were deployed in varying subarctic terrains defined by swamps and forests for the 3D survey. For 2D profiles, over 700 three-component receivers (GSBs) were used next to the existing gravel roads utilized by the Vibroseis truck. For the 3D survey, receiver spacing was kept at 30 m with inline spacing of 200 m. Shot points were located mainly following the existing roads within the forest. For the 2D survey, a uniform receiver spacing of 15 m and a shot spacing of 30 m was used. Seismic data processing was applied with the overall aim of suppressing noise, boosting signal-to-noise ratio, and improving reflectivity in the data. Special emphasis was put on handling the highly heterogeneous near-surface weathering layer. Final results revealed several reflectors at various depths, which have preliminarily been interpreted to originate from mafic intrusions, diabase veins, and faults cross-cutting the intrusion.

How to cite: Singh, B., Amirzadeh, Y., Autio, U., Gόrszczyk, A., Heinonen, S., Malinowski, M., and Wojdyła, M. and the SEEMS DEEP Working Group: First results from the SEEMS DEEP seismic survey conducted over the Koillismaa Igneous Complex, Northern Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17303, https://doi.org/10.5194/egusphere-egu24-17303, 2024.

EGU24-19207 | ECS | Orals | ERE4.1 | Highlight

The Horizon Europe AGEMERA Project: Innovative Non-Invasive Geophysical Methodologies for Mineral Exploration 

Jari Joutsenvaara, Marko Holma, Pasi Kuusiniemi, Markku Pirttijärvi, Barbara Stimac Tumara, Martin Schimmel, and David Martin

The AGEMERA project [1], which is an acronym for Agile Exploration and Geo-Modelling for European Critical Raw Materials, employs three non-invasive survey methods for mineral exploration: a passive seismic method to assess bedrock hardness and rock type boundaries; an integrated, multi-sensing fixed-wing drone system for measuring conductivity, magnetism, and radioactivity; and a multidetector system based on muon detection for detailed 2D, 3D, and 4D density profiles of large-volume rock bodies (with the 4th dimension being time). The technologies are designed to map geological structures in scenarios where traditional methods are either environmentally unsound or socially challenging. By the project's conclusion, these methods are anticipated to achieve a Technological Readiness Level (TRL) of 5 within a three-year timeline.

The technologies vary in their operational capacities, including acquisition time, depth penetration, area coverage, and volume assessment. The multi-sensing drone effectively probes to 300-500 meter depth and can survey vast areas, up to hundreds of square kilometres, in a single campaign. Muography, on the other hand, can reach depths of up to 1000 metres and cover large volumes, up to a cubic kilometre. Passive seismic analysis, meanwhile, can survey any area and depth while a larger depth usually implies a lower resolution. While these techniques, especially when combined with deep 3D muography, may require extended periods for data collection, the valuable insights they offer make them a worthwhile investment.

After conducting these innovative, non-invasive geophysical surveys, the findings will be consolidated in a web-based data repository. This repository will be accessible for in-depth analysis to enhance our understanding of critical raw material distribution.

The project receives funding from the Horizon Europe program (Grant agreement ID: 101058178).

 

[1] AGEMERA project homepage, www.agemera.eu (accessed 9.1.2024)

How to cite: Joutsenvaara, J., Holma, M., Kuusiniemi, P., Pirttijärvi, M., Stimac Tumara, B., Schimmel, M., and Martin, D.: The Horizon Europe AGEMERA Project: Innovative Non-Invasive Geophysical Methodologies for Mineral Exploration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19207, https://doi.org/10.5194/egusphere-egu24-19207, 2024.

EGU24-20261 | ECS | Orals | ERE4.1

REE (re)cycle: a multi-sensor investigation from rocks to tailings 

Andréa de Lima Ribeiro, Titus Abend, Margret Fuchs, Christian Röder, Jan Beyer, Kimmo Kärenlampi, Yang Xiao Sheng, Johannes Heitmann, and Richard Gloaguen

Rare earth elements (REE) are key constituents in electronic devices (e.g. smartphones, batteries), being present in both end-user and industrial applications. The rapid innovation cycles of electronic devices, combined with the increasing demand for new technological applications (e.g. mobility and e-cars) pose a challenge for the supply of REE, which are considered as Critical Raw Materials (CRM). This scenario calls for rapid, non-invasive methods that enable the identification of new REE-rich mining resources. Furthermore, the high supply risks associated with CRM such as REE drive technological developments to compensate and overcome market fluctuations by turning previously not mined co-resources into valuable and economic modalities, such as re-mining materials.

We present an investigation focused on the identification of REE in waste rocks and tailing materials from the mine of Siilinjärvi (Finland). The deposit in the area consists of alkaline-carbonatite rocks, with the most important REE-bearing minerals being apatite (average REE concentration: 0.4% (wt%)) and monazite (REE concentration: up to 67% (wt%)). Mining activities focus on extraction of phosphate from fluorapatite, and the chemical reactions involved in this extraction generate phosphogypsum (PG) as a by-product. Literature reports indicate that REE can be incorporated to the PG matrix in the crystallisation process, with the most relevant examples including Nd, Ce, La, Sm, Gd, Tb, Dy, and Eu. 

Our goal is to highlight how the sequential acquisition by multiple optical methods (multi-sensor approach) can trace REE contents for individually identified REE from pristine rocks to processing waste dumped in tailings. Each material type was scanned by two fast hyperspectral imaging (HSI) sensors integrated in a conveyor-belt system:  a reflectance-based HSI sensor operating in the visible to near-infrared and short-wave infrared (Specim AisaFenix); and an innovative laser-induced fluorescence line scan sensor (HSI-LiF, Freiberg Instruments). The optical sensing results were validated by mineralogical methods (mineral liberation analysis (MLA)). MLA results for PG indicate the presence of REE-bearing minerals including gypsum, apatite, and monazite (respective abundances (wt%): 97.4, 0.6, and 0.08).

Optical features characteristic of Nd were identified on rocks and tailings samples by both HSI-reflectance and HSI-LiF sensors. Spectral signatures were detected in HSI-LiF spectra for an additional REE group including Sm, Er, and Pm.

We highlight that efficient, non-invasive optical sensing can detect and re-evaluate tailing materials as a baseline for economic considerations according to market needs. The results confirm that REE detected on the pristine rocks of the mine can be traced through the mineral processing route to be found again in the tailings material. The multi-sensor optical detection based on HSI-reflectance and HSI-LiF, accordingly, provides an efficient non-invasive tool for exploring both mining and re-mining potential by providing immediate results on REE types and their spatial abundance, when employed as scanning techniques.

This investigation was performed within the scope of EIT-funded projects (inSPECTOR and RAMSES-4-CE).

How to cite: de Lima Ribeiro, A., Abend, T., Fuchs, M., Röder, C., Beyer, J., Kärenlampi, K., Xiao Sheng, Y., Heitmann, J., and Gloaguen, R.: REE (re)cycle: a multi-sensor investigation from rocks to tailings, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20261, https://doi.org/10.5194/egusphere-egu24-20261, 2024.

EGU24-21098 | ECS | Posters on site | ERE4.1

Impact of using a 3.5 μm film to analyze the chemical composition of crystal samples with a handheld X-Ray Fluorescence equipment 

Filipa Dias, Ricardo Ribeiro, Alexandre Lima, Filipe Gonçalves, Encarnación Roda-Robles, and Tânia Martins

Some potassium-feldspar crystals from lithium-rich aplite-pegmatites from Northern Portugal have been analyzed with a handheld X-Ray-Fluorescence (XRF) equipment. This study compares the impact of analyzing the samples with an XRF film versus analyzing them without it. The film used was a Hitachi Poly-S High Performance XRF Sample Film of 3.5 μm, commonly used for analyzing samples in cups and powders. Although Hitachi alerts for the unsuitability of the film for analyzing light elements, this study helps understand the extent of error that this film can cause when analyzing this type of sample. 15 cleaned potassium feldspar crystals with a size between 1-3 cm have been analyzed with a Bruker S1 TITAN 600 containing an X-ray tube with a 2 W and 5-100 μA Rh anode. The Geomining factory calibration was used for the sample analysis.

The results show that the potassium-feldspars analyzed with the film had their major elements drop by 20-40% for silica (SiO2), 30-50% for aluminum (Al2O3) and 10-20% for potassium (K2O). As for the trace elements, calcium (Ca) dropped by 20-30%, phosphorous (P) by 20-40% and rubidium (Rb) and iron (Fe) have small errors that can vary from plus 0-10% to minus 0-10%. Knowing the film impact will hopefully be of assistance for the correct interpretation of portable XRF results during field campaigns for mineral exploration.

This study was financially supported by FCT, I.P., in the framework of the ICT (UIDB/04683/2020 and UIDP/04683/2020), by the PhD project (2020.05534.BD) and by national funds from MCTES, through FCT, co-financed by ESF through POCH and NORTE 2020. This work is also supported by the Greenpeg project, reference 869274, funded by the Horizon 2020 framework program of the European Union.

How to cite: Dias, F., Ribeiro, R., Lima, A., Gonçalves, F., Roda-Robles, E., and Martins, T.: Impact of using a 3.5 μm film to analyze the chemical composition of crystal samples with a handheld X-Ray Fluorescence equipment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21098, https://doi.org/10.5194/egusphere-egu24-21098, 2024.

EGU24-21276 | Orals | ERE4.1

Application of innovative technologies for increasing gold production in Kyzylkum province of Uzbekistan 

Alexander Antonov, Vladimir Tsoy, and Bakhtiyar Nurtaev

The Kyzylkum province in Southern Tien Shan, Uzbekistan, which includes the world's largest gold deposit Muruntau, is among the world's major gold provinces. Analysis of all available geological and geophysical data has revealed ten linear trends controlled by regional strike-slip shear zones in the ore-bearing sand-shale sediments O₂-S₁. Analogies were made with gold trends in North-Eastern Nevada (Carlin trend and others). Gold is present predominantly as microinclusions in pyrite and arsenopyrite in both provinces. A significant part of inclusions is represented by invisible nano-sized gold particles.

Opportunities of increasing gold output in the Kyzylkum province are connected with the reduction of losses of "invisible" gold in the process of ore concentration and processing. Innovative technologies and modern laboratory equipment were used to determine nano-sized gold concentration. Another source of increasing gold production is exploration and development of ore-controlling structures overlapped by younger sediments. Remote sensing methods are widely used to identify promising parts of the structures.

 

How to cite: Antonov, A., Tsoy, V., and Nurtaev, B.: Application of innovative technologies for increasing gold production in Kyzylkum province of Uzbekistan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21276, https://doi.org/10.5194/egusphere-egu24-21276, 2024.

EGU24-369 | ECS | Posters on site | ERE4.8 | Highlight

Potential lithium enrichment in pyrites from organic-rich shales 

Shailee Bhattacharya, Michael C. Dix, Shikha Sharma, Albert S. Wylie, and Tom Wagner

In order to meet the technological needs of the energy transition, batteries of all scales, particularly those that power electrical vehicles, have become increasingly important. Lithium-ion batteries are in wide use at present, and continued research to improve them has been a focus of energy engineering. This, in turn, has greatly increased the demand for lithium (Li) as a natural resource. While the primary ores of Li (pegmatite, salar brine, and volcanic-associated clay) are generally well-understood, it would be desirable to identify additional Li sources that could be safely and economically exploited. Using material from previous industrial operations (e.g., mine tailings or drill cuttings) as a source of additional Li would be attractive as it would generate little or no new waste material.

Our study was carried out on 15 Devonian shale samples of varying organic richness from wells drilled in the Appalachian basin (USA). Sequential extraction of the samples was performed to measure Li recovery from targeted rock-forming phases, namely the carbonates, Fe-Mn oxyhydroxides, pyrites, and organic matter. The mineralogy of the post-leaching residue was found to be dominated by silicates and anatase, suggesting the target phases were successfully leached out of the whole rock.

Unsurprisingly, the data shows higher whole-rock Li values are observed in samples with a higher total clay content. The lowest whole-rock Li contents correspond to samples having higher contents of total organic carbon (TOC) and pyrite. Unexpectedly, however, samples with relatively lower Li contents (22 ppm) can liberate up to 54% of the total lithium from pyrite alone. Furthermore, we observe a positive correlation between pyrite content and %Li recovery in the pyrite leachate (r2= 0.732). These initial findings suggest that pyrite in conjunction with organic matter may play a previously unrecognized role in the Li distribution in organic-rich shales. The geochemical processes that might cause Li enrichments associated with pyrite are not well-understood. However, since Li mobility is highly sensitive to small increases in temperature, the very high thermal maturation of the studied shale sequence may have significantly impacted Li remobilization during the smectite-to-illite clay-mineral transformation. The common Li-mineral that can coexist with different phases of FeS is Li2S at temperatures ⩽ 75°C – 135°C. Several reaction mechanisms have been proposed, but there is little known about the rate kinetics and reaction steps involved in Li association with pyrite in shales.

This study suggests the possibility that some Li may be sequestered in pyrite in organic-rich shales. As pyrite is a common mineral in the Appalachian Basin, this has implications for exploiting shale pyrite in the Devonian sequence if the Li proves economically extractable. Drill cuttings from past and current oil and gas operations are a ready material upon which to test the feasibility of this concept.

How to cite: Bhattacharya, S., Dix, M. C., Sharma, S., Wylie, A. S., and Wagner, T.: Potential lithium enrichment in pyrites from organic-rich shales, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-369, https://doi.org/10.5194/egusphere-egu24-369, 2024.

EGU24-3754 | Posters on site | ERE4.8

Evaluating the potential source of contamination from sulfide minerals in major rocks in South Korea 

Gil-Jae Yim, Seung-Jun Youm, Hyeop-Jo Han, Seon-Yong Lee, and Jin-Young Lee

The utilization of surrounding rocks is required in human living areas, and these development activities create large cut slopes and generate large amounts of cut rocks as construction materials. If these development areas are strata containing sulfide minerals (pyrite, etc.), contamination may occur, causing environmental pollution problems in the development site and surrounding areas. Several methods have been studied for the preliminary identification of potentially contaminated rocks, including Acid Base Accounting (ABA), Modified ABA procedures, Carbonate Neutralization Potential determinations, Humidity cell tests, Column tests, Batch reactor (Shake flask) tests, and Field tests (Orava, 1997; USEPA and Hardrock Mining, 2003). Studies on rock samples have resulted in most of the samples being classified as Non-Acid Forming (NAF), with some samples containing sulfide minerals (such as pyrite) being classified as Potentially Acid Forming (PAF). It can be expected that future development of these rocky areas may affect the surrounding environment or rock utilization. Therefore, these rock areas are considered to be in need of management. It would be desirable to investigate the occurrence of pollution sources caused by mineral sulfides in advance and take appropriate countermeasures. It is expected to reduce the economic losses that may occur in the future, and it is judged that the pollution problem of the surrounding environment can be further reduced.

How to cite: Yim, G.-J., Youm, S.-J., Han, H.-J., Lee, S.-Y., and Lee, J.-Y.: Evaluating the potential source of contamination from sulfide minerals in major rocks in South Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3754, https://doi.org/10.5194/egusphere-egu24-3754, 2024.

The assessment in accordance with the Water Framework Directive and the EU Water Framework Directive continues to show poor chemical status for around one third of groundwater bodies in Germany due to excessive nitrate concentrations. In many regions, this is due to high nitrogen fertiliser intensities that have been applied to agricultural land for decades.

Nitrate input and degradation processes in aquifers are modelled using step-by-step hydrogeochemical continuous stirred tank reactors (CSTR) sequences with PHREEQC. This makes it possible to show how the overall water quality is characterised by the interaction of hydrogeochemical sub-processes such as nitrogen and lime fertilisation, substance releases from grassland ploughing, denitrification via organic carbon (heterotrophic degradation) and most importantly pyrite (lithotrophic degradation) and sulphate reduction, but also nitrate breakthroughs and well clogging.

CSTR models are not discretised spatially or temporally; their focus is on identifying and quantifying the relevant hydrogeochemical reactions. The advantage of this method is much shorter and more manageable calculation times than with fully coupled reactive transport models. They provide the user with a comprehensive hydrogeochemical understanding of nitrate degradation by pyrite oxidation processes in groundwater. In addition to reaction kinetic aspects, this also includes the effects of a loss of nitrate degradation capacity [1]. In the focus is the dissolution of pyrite and its re-precipitation and a reaction front developing into the system [2]. Moreover, concentrations of pyrite dissolution products (iron, sulphate, trace metals) can be understood.

Hydrogeochemical modelling in this sense is initially retrospectively oriented based on measurements and the longest possible time series. However, a hydrogeochemical CSTR sequence has been checked for plausibility and validated with sensitivity and parameter studies can then also be used to forecast water quality [3]. This provides a "tool" with which the effects of anthropogenic interventions in a geosystem can be calculated with regard to the effects on groundwater and raw water quality.

 

[1] Wilde, S., Hansen, C. & Bergmann, A. Nachlassender Nitratabbau im Grundwasser und deren Folgen – abgestufte modellgestützte Bewertungsansätze. Grundwasser 22, 293–308 (2017). https://doi.org/10.1007/s00767-017-0373-0

[2] Kübeck, C., Hansen, C., König, C. et al. Ableitung der Reaktivität von organisch gebundenem Kohlenstoff in redoxzonierten Grundwasserleitern – Hydrogeochemische Modellierung kinetisch angetriebener Reaktionssysteme. Grundwasser 15, 103–112 (2010). https://doi.org/10.1007/s00767-009-0136-7

[3] Jesußek, A., Hansen, C. & Wilde, S. Identifikation und Regionalisierung von Nitratabbauprozessen in einem Grundwasserleiter – Möglichkeiten und Nutzen für die Wassergewinnung. Grundwasser 21, 333–344 (2016). https://doi.org/10.1007/s00767-016-0337-9

How to cite: Hansen, C. and Kühn, M.: Pyrite and its role in the development of nitrate pollution and raw water quality in water catchment areas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5822, https://doi.org/10.5194/egusphere-egu24-5822, 2024.

EGU24-6083 | ECS | Posters on site | ERE4.8

Pyrite-based trace element fingerprints for methane and oil seepage 

Daniel Smrzka, Zhiyong Lin, Patrick Monien, Wolfgang Bach, Jörn Peckmann, and Gerhard Bohrmann

Pyrite forms at marine hydrocarbon seeps as the result of the microbial oxidation of methane, organic matter, and crude oil coupled to sulphate reduction. Redox sensitive and nutrient trace elements in pyrite may hold valuable information on present and past seepage events, the evolution of fluid composition, as well as the presence of heavy hydrocarbon compounds from crude oil. This study uses the trace element compositions of pyrite that formed at methane seeps and crude oil-dominated seeps to constrain element mobilities during the sulphate reduction processes, and to which degree specific trace elements are captured by pyrite. Pyrite forming at oil seeps shows high Mn/Fe ratios and high Mo content compared to pyrite from methane seeps. These patterns suggest either more intense or persistent sulphidic conditions, or an intensified manganese (oxy)hydroxide shuttle process at oil seeps. Copper and Zn are enriched in oil seepage-derived pyrite while Ni and V enrichment is less pronounced, suggesting either a selective uptake of specific elements by pyrite, or varying trace element compositions of organic compounds oxidized via microbial reduction.   

How to cite: Smrzka, D., Lin, Z., Monien, P., Bach, W., Peckmann, J., and Bohrmann, G.: Pyrite-based trace element fingerprints for methane and oil seepage, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6083, https://doi.org/10.5194/egusphere-egu24-6083, 2024.

EGU24-8617 | ECS | Orals | ERE4.8

What can we learn from pyrite about the hydrogeology of argillaceous formations? 

Marie Bonitz, Theresa Hennig, Anja Schleicher, Christof Kusebauch, David Jaeggi, and Michael Kühn

Argillaceous rock formations provide favourable properties to act as geological barriers for the disposal of high-level radioactive waste. Opalinus Clay is the chosen host rock in Switzerland and is also being considered in Germany. Pyrite is an ubiquitous mineral found in most argillaceous rock formations, and is also present in the Opalinus Clay and its adjacent units. For the long-term integrity of the disposal site, temporally and spatially stable geochemical conditions are essential. Pyrite might be one essential indicator how the sediment formation is influenced by surrounding aquifers. The appearance and composition of pyrite has been used to investigate different geological processes, such as depositional and diagenetic settings, paleoredox conditions and enrichment processes. The geochemical and mineralogical changes in rock formations provide information about processes in the past, and thus enable an assessment for the future. In this context the detailed analysis of pyrite might be a useful tool.

In May 2023, two boreholes were drilled (15 and 25 m deep) in the Mont Terri underground laboratory to investigate the water-bearing members of the Staffelegg Formation (Toarcian-Sinemurian) underlying the Opalinus Clay (Toarcian). The focus was hereby on the transition zones between the permeable and non-permeable rocks to detect alteration reactions and mobilisation processes. In addition to the analysis of the bulk mineralogy and geochemistry, pathways of groundwater and fracture zones have been investigated by analysing thick sections with X-ray and microscopic methods.

Two groundwater paths have been identified in the Staffelegg Formation with fracture zones and their fillings. Calcite and barite are distinguishable and represent two generations, revealing a change of the groundwater composition with supersaturation at different points in time. Therefore, the hydrogeological system experienced at least two events of advective transport. The analysis of pyrite addresses the question to which extent these events have altered and infiltrated the formations.

Pyrite has been formed diagenetically and potentially syngenetically and is present in varying morphologies: μm- to cm-sized euhedral crystals, framboids and nodules. The size and morphology of diagenetic pyrites provide information about the transport processes in the sediment. Euhedral crystals are found in diffusion dominated systems. Accumulations of microcrystals reflect conditions providing an initial nucleation burst, but further crystal growth is limited by restricted supply of Fe and S as it occurs in diffusion-limited regimes with minor advection. Nodules can form in gently advective or stagnant systems with good nutrient supply. The types of pyrite close to fractures and transition zones is used to characterize the predominant transport process at this position.

Diagenetic carbonates and sulphide or sulphate minerals control the concentration of major cations, and redox reactions. Therefore, they provide information about the succession of processes from deposition, to diagenesis, mobilisation and alteration. Their analysis has the potential to assess the long-term integrity of the Opalinus Clay as a host rock and the surrounding formations. The gained understanding of the hydrogeological influence on the geochemical conditions is to be transferred to other potential disposal sites in argillaceous formations.

How to cite: Bonitz, M., Hennig, T., Schleicher, A., Kusebauch, C., Jaeggi, D., and Kühn, M.: What can we learn from pyrite about the hydrogeology of argillaceous formations?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8617, https://doi.org/10.5194/egusphere-egu24-8617, 2024.

EGU24-9060 | Orals | ERE4.8

Quantifying key drivers of marine pyrite content and isotopic composition 

Jordon Hemingway, Cornelia Mertens, and Sarah Paradis

Microbial sulfate reduction (MSR) and subsequent pyrite burial in marine sediments plays a crucial role in Earth’s long-term carbon and oxygen budgets; by reducing sulfate and producing alkalinity, this process effectively increases atmospheric O2 and lowers CO2 levels. Given that MSR exhibits a large and reduction-rate-dependent sulfur-isotope fractionation, changes in pyrite sulfur-isotope compositions (δ34S values) through geologic time have long been interpreted to reflect global signals such as marine sulfate reduction rates, microbial community behavior, and the amount of sulfur buried as pyrite vs. evaporite minerals. However, recent research has demonstrated that marine MSR fractionation likely operates near an equilibrium limit regardless of reduction rate. These studies instead implicate local environmental and sedimentological factors as drivers of pyrite δ34S values. Despite this advancement, the sensitivity of pyrite formation rate and δ34S value to changes in environmental and sedimentological variables—both today and through geologic time—remains unconstrained due to the complex interactions between controlling variables.

To provide mechanistic and quantitative constraints, we developed and applied a non-dimensional diagenetic model that extracts the natural variables governing pyrite formation. Assuming equilibrium MSR isotope fractionation and using only locally measured or globally interpolated boundary values as inputs (i.e., no free parameters), our model accurately predicts all available modern observations (n = 216 cores) with an average root-mean square error of 0.3 wt % for pyrite content and 16.5 ‰ for δ34S. Extrapolating this result, we estimate global pyrite burial flux to be ~1.3 × 1012 mol FeS2 yr−1 with a weighted-average δ34S value of ~-21 ‰ VCDT.This flux is statistically identical to independent estimates of total riverine sulfate input (i.e., pyrite-oxidation and evaporite-dissolution derived), indicating the sulfur cycle currently operates in steady state. However, calculated pyrite burial exceeds pyrite-oxidation derived inputs, suggesting net atmospheric O2 release and CO2 consumption by the sulfur cycle.

Mechanistically, we conclude that pyrite formation rate is highly sensitive to local reactive iron input, whereas δ34S value is primarily controlled by organic carbon reactivity-to-sedimentation rate ratio (termed Da*, a modified Damköhler number) and organic carbon-to-sulfate ratio (termed Γ0). In contrast to previous models, we show that pyrite δ34S is largely insensitive to bioturbation due to counter-balancing impacts on Da* and Γ0. Rather, when combined with a geologic pyrite δ34S record, our interpretation requires an increase in Da* and decrease in Γ0 since the Paleozoic, possibly driven by changing organic matter reactivity and sulfate concentration through geologic time.

How to cite: Hemingway, J., Mertens, C., and Paradis, S.: Quantifying key drivers of marine pyrite content and isotopic composition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9060, https://doi.org/10.5194/egusphere-egu24-9060, 2024.

EGU24-14930 | ECS | Posters on site | ERE4.8 | Highlight

Microbial Pyrite Oxidation and Chemical Weathering to a Typhoon Precipitation and Discharge Event in Taiwan 

Jui-Ming Chang, I-Feng Wu, Li-Hung Lin, Aaron Bufe, Pei-Ling Wang, Hsi-Ling Chou, Niels Hovius, and Tung-Chou Hsieh

Microbially mediated pyrite oxidation is considered a crucial element of the global weathering engine. However, observations of bacterial pyrite oxidation in nature remain scarce due to limited field sampling, particularly during typhoon precipitation and discharge events. In this study, we present a time series of water chemistry at three-hour intervals from the Sinwulyu River, southeast Taiwan, across the typhoons Nesat (0-27th hours) and Haitung (30th-60th hours) in 2017. The cumulative precipitation for the two typhoons ranged from 18 to 78 mm and 59 to 227 mm in the catchment, resulting in discharge increases from 6 to 122 c.m.s. and 53 to 1,207 c.m.s. at the catchment's outlet. The Sinwulyu River drains a catchment underlain by metamorphosed passive-margin sediments that are rapidly exhuming. Integrating measurements of major ions, δDH2O, δ18OH2O, δ34SSO4, δ18OSO4, and simulations of discharge, we find dynamic changes in the source of solutes to the stream water across the typhoons. Our findings indicate that all chemical solutes experienced dilution by 30-80% during typhoon discharge. δDH2O and δ18OH2O values were more negative with increasing discharge, suggesting that the discharge is driven by a combination of precipitation and groundwater injection into the river. δ34SSO4 and  δ18OSO4 ranged from -3.9 ‰ to -7.1 ‰ and from -1.9 ‰ to -6.5 ‰, respectively, suggesting that the majority of riverine sulfate is sourced from oxidative weathering of pyrite. In addition to variations of the water chemistry, we also found substantial changes in the concentrations of sulphur-oxidizing bacteria, Thiobacillus and, Sulfuricurvum (anaerobic microorganisms) emerged as the dominant genera during typhoons. The peak concentration of Thiobacillus occurred at the first typhoon at the 27th hour (1.17×107 copies/L), while Sulfuricurvum peaked at the 48th hour during the second typhoon (2 hours before peak discharge) with a concentration of 2.32×108 copies/L, coinciding high ranges of sediment concentrations and representing 241 and 1,570 times the background level before typhoons, respectively. Both peak concentrations were sudden appearances, indicating that some pools of concentrated microorganisms were quickly depleted by typhoon precipitation/discharge. Notably, the highest abundance of Sulfuricurvum coincided with an increase in chemical solutes. As the discharge rose from 714 to 1,092 c.m.s. (45-48th hour), the concentration of sulfuricurvum increased around tenfold, coupled with an 8%, 7%, and 7% increase in the concentrations of SO4-2, Ca+2, and Mg+2, respectively. However, other chemical solutes maintained a similar concentration. These observations suggest the typhoon mobilized a specific reservoir of elevated pyrite oxidation for carbonate weathering under anaerobic conditions. Through discharge simulation, the high concentration of solute and Sulfuricurvum mobilized substantially at hourly precipitation rates of over 20 mm/hr. We propose that an ample amount of precipitation is essential to flush out the previously inaccessible pool with anaerobic bacterial pyrite oxidation and subsequent carbonate weathering in the stream.

How to cite: Chang, J.-M., Wu, I.-F., Lin, L.-H., Bufe, A., Wang, P.-L., Chou, H.-L., Hovius, N., and Hsieh, T.-C.: Microbial Pyrite Oxidation and Chemical Weathering to a Typhoon Precipitation and Discharge Event in Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14930, https://doi.org/10.5194/egusphere-egu24-14930, 2024.

EGU24-15524 | ECS | Orals | ERE4.8

Pyrite trace element proxies for magmatic volatile influx in submarine subduction-related hydrothermal systems 

Jan J. Falkenberg, Manuel Keith, Karsten M. Haase, Reiner Klemd, Martin Kutzschbach, Anna Grosche, Maria Rosa Scicchitano, Harald Strauss, and Jonguk Kim

Seafloor massive sulfides represent modern analogues to ancient volcanogenic massive sulfide deposits, which can be particularly enriched in volatile and precious metals (e.g., Te, Au, Ag, Cu, Bi, Se) in subduction-related systems. However, it remains unclear whether the influx of magmatic volatiles has a systematic control on the metal endowment of submarine hydrothermal mineralization on the plate-tectonic scale. Using a novel microanalytical approach based on the coupling of SIMS δ34S with trace element LA-ICP-MS on a scale of ~25 µm in pyrite from 11 submarine hydrothermal systems, we could demonstrate for the first time that the Te, As, and Sb contents and the ratios of these elements vary systematically with the δ34S composition of hydrothermal pyrite and native S. In contrast to trace element concentrations, Te/As and Te/Sb show a more significant correlation with δ34S in pyrite, indicating that element ratios provide a more robust record of metal sourcing. On this basis, we define a quantitative trace element threshold of high Te/As (>0.004) and Te/Sb (>0.6) ratios in pyrite that can be used to identify the influx of magmatic volatiles to submarine subduction-related hydrothermal systems independent of δ34S isotope measurements. Two-component fluid mixing simulations further suggest that even small amounts (<0.5 to ~5%) of magmatic volatile influx drastically change the Te/As (and Te/Sb) ratio of the modelled fluid, but only slightly modify its δ34S composition. Hence, Te/As and Te/Sb ratios are more sensitive in recording the influx of magmatic volatiles into submarine hydrothermal systems than S isotope systematics, which are typically influenced by seawater-derived S leading to ambiguous δ34S signatures. We conclude that Te/As and Te/Sb systematics in pyrite provide a robust proxy to evaluate the metal sources in submarine hydrothermal systems from the grain to plate-tectonic scale.

How to cite: Falkenberg, J. J., Keith, M., Haase, K. M., Klemd, R., Kutzschbach, M., Grosche, A., Scicchitano, M. R., Strauss, H., and Kim, J.: Pyrite trace element proxies for magmatic volatile influx in submarine subduction-related hydrothermal systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15524, https://doi.org/10.5194/egusphere-egu24-15524, 2024.

EGU24-15652 | ECS | Orals | ERE4.8

The role of pyrite surface area and thermochemical sulfate reduction in clastic-dominant Zn Deposits.  

Peter Berger, Joseph Magnall, Michael Kühn, and Sarah Gleeson

It is vital to keep up with the demand for critical minerals during the transition to sustainable energy systems. Doing so requires expanding our knowledge of ore depositional processes. Pyrite is a common gangue mineral in clastic dominated (CD) deposits, which are the highest value Zn deposits. In CD-type deposits, pyrite is often part of the pre-, syn-, and post-ore paragenesis and can therefore provide an important redox buffer and potentially a source of sulfur during ore deposition. The distribution of syn-ore pyrite beyond economic mineralization can also form an important mineralogical halo around CD-type deposits.

In this study we investigate the role of fluid interaction with different types of pyrite on ore formation in the Teena deposit (Australia). The host unit for the Teena deposit is an organic rich, variably pyritic, dolomitic siltstone. We created a series of 2D, reactive transport models using the software X2t (Geochemists Workbench) to investigate the role of pyrite surface area as a major control on ore deposition.

Similar to many CD-type deposits, the main type of pre-ore diagenetic pyrite in the host unit is framboidal, which has a high surface area, whereas syn-ore generations of pyrite tend to be coarser grained. In the models, pyrite surface area was varied from 100 (syn-ore) to 10,000 cm2/g (diagenetic). Organic matter provided a drive for thermochemical sulfate reduction (TSR) in the models, and TSR rates were varied over several orders of magnitude in accordance with laboratory measured values.

As the incoming hydrothermal fluid reacted with the host unit, pyrite and dolomite are dissolved and sphalerite is precipitated. The surface area of pyrite evolved as it dissolved and reprecipitated in the form of a more massive, lower surface area, hydrothermal pyrite.

Models using the higher surface area values for diagenetic pyrite resulted in more compact and higher grade ore deposition. The pyrite at the inlet in this scenario dissolved completely. As the pyrite reprecipitated, it formed more extensive halo ahead of the sphalerite reaction front than in models using the lower hydrothermal surface area. Slower rates of TSR also broadened the pyrite halo and decreased the sphalerite ore grade. Low pyrite surface area coupled with low TSR rates resulted in a disseminated deposit. Based on these results, the paragenetic evolution of pyrite over the course of hydrothermal alteration and the resulting changes in surface area are an important control on ore grade and the extent of halo formation.

How to cite: Berger, P., Magnall, J., Kühn, M., and Gleeson, S.: The role of pyrite surface area and thermochemical sulfate reduction in clastic-dominant Zn Deposits. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15652, https://doi.org/10.5194/egusphere-egu24-15652, 2024.

EGU24-21083 | Orals | ERE4.8 | Highlight

The shelf life of pyrite - effects of pyrite weathering in exposed continental shelves on global CO2 and O2 

Martin Kölling, Ilham Bouimetarhan, and Matthias Zabel

During times of low sea-levels in glacials there is evidence of large-scale pyrite oxidation on exposed continental shelves. While this process directly reduces atmospheric oxygen levels, acid drainage generated by this reaction increases the release of CO2 through carbonate buffering within the previously marine shelf sediments. Although this scenario is expected to result in negative feedback, sea-level and atmospheric CO2 levels have co-varied throughout most of the last 800 thousand years (ka) for which direct records of CO2 exist. Only during peak glacial conditions with sea-levels as low as 125 m lower than today, CO2 levels have reached an apparent lower limit around 190 ppm independent of decreasing sea-levels. Here we show that pyrite driven release of CO2 and decline of O2 during six of the last nine glacial-interglacial cycles are focussed in 10 ka to 40 ka-long periods preceding glacial terminations.

Using a sea-level driven model of pyrite weathering in drained continental shelves, we demonstrate that repeated sea-level low-stands force pyrite oxidation to ever greater depths. This occurs whenever the duration of an interglacial is insufficient to restock the shelf pyrite inventory through sulphate reduction in the shelf sediments. During the Quaternary, the decreasing amount of pyrite in the exposed shelf sediments represents a discharging 'acid capacitor' (Kölling et al., 2019). This model was inspired by experience from modelling pyrite weathering in open-pit lignite mine overburden material which may be interpreted as a scaled-down model of glacial continental shelf exposure during sea-level low-stands.

If pyrite oxidation forced CO2 release specifically at low sea-levels was sufficient to amplify the orbitally driven climate forcing and trigger glacial terminations, the absence of CO2 release caused by exposed pyrite rather than an astronomically controlled '100 ka pacing' might have extended the length of glacial-interglacial cycles from one to two or three obliquity cycles. Future ocean drilling specifically aiming to recover long cores on shelves could reveal the existence of a 'pyrite gap' that should exist between surficial young pyritic layers and deeper old pyritic sequences with indications of acid leaching.

 

Kölling, M., Bouimetarhan, I., Bowles, M.W. et al. Consistent CO2 release by pyrite oxidation on continental shelves prior to glacial terminations. Nat. Geosci. 12, 929–934 (2019). https://doi.org/10.1038/s41561-019-0465-9

How to cite: Kölling, M., Bouimetarhan, I., and Zabel, M.: The shelf life of pyrite - effects of pyrite weathering in exposed continental shelves on global CO2 and O2, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21083, https://doi.org/10.5194/egusphere-egu24-21083, 2024.

The formation of pyrite has been extensively studied because of its abundance in many anoxic environments such as marine and river sediments, groundwater aquifers, and peat lands, and hence its importance in both iron and sulfur cycling. It forms over a wide pH interval, ranging from acidic to alkaline. It is generally regarded that sulfide reacting with iron-containing minerals forms metastable iron sulfide minerals before eventually transforming into pyrite in the presence of different sulfur.

In this contribution, I will discuss the importance of sulfidation of ferric (oxy)hydroxides (FeOOH), i.e. the reaction between aqueous sulfide and the surface of FeOOH, to stimulate pyrite formation and compare this process with other pathways and kinetics of pyrite formation described in the literature. Sulfidation of FeOOH initially leads to formation of surface bound FeS-species and its transformation to pyrite is controlled by either the availability of FeOOH or the supply rate of sulfide. These kinetic constraints define the environments were rapid pyrite formation occurs to be suboxic, rich in FeOOH and shaped by cryptic sulfur cycling. Under these conditions, highly reactive pyrite precursor species are forming that also affect trace metal cycling.

How to cite: Peiffer, S.: Controls on recent pyrite formation in aquatic systems and its relevance for environmental processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21260, https://doi.org/10.5194/egusphere-egu24-21260, 2024.

EGU24-21310 | Posters on site | ERE4.8

Partitioning of trace elements between hydrothermal fluids and pyrite 

Christof Kusebauch, Joseph Michael Magnall, and Sarah Gleeson

Pyrite is the most abundant sulfide on Earth and can host a large variety of trace elements including Au, Co, Mo, Cu, Pb, As, Se, Te, Bi and Sb. Trace element variations in pyrite have been used to study various processes during ore formation, to reconstruct paleo-seawater composition and to understand hydrothermal systems. Furthermore, element enrichment in pyrite can reach high enough concentrations that pyrite itself becomes an ore mineral and can be mined. For example, the enrichment of Au in As-bearing pyrite can reach up to several thousand ppm in the giant Au deposits of the Carlin trend (Nevada, USA). In this case the coupled partitioning of Au and As is considered to be an ore forming process1. The high variability of trace elements in pyrite makes it potentially a powerful tool for the reconstruction of fluid compositions in hydrothermal settings. Nevertheless, the lack of partition coefficients of trace elements between hydrothermal fluids and coexisting/newly forming pyrite hinders a wider use of pyrite as a fluid proxy. Also, the underlying processes controlling the incorporation into the crystal structure and the interplay of different trace elements during partitioning are not well understood.

Here, we present results of hydrothermal batch experiments at 200°C studying the partitioning of Co, Cu, Pb, Se, Bi, As and Sb between aqueous solutions and newly formed pyrite. We use the replacement of siderite to crystalize euhedral pyrites large enough to be measured by LA-ICPMS for their trace element content2. The initial trace element concentration in the experimental fluid varied from 0.1 to 10 ppm. To study the influence of As in pyrite on the D values, As concentration in the experiments was varied independently, whereas all other tracers had a constant ratio. 

Concentrations of trace elements in hydrothermal pyrite range between 10 ppm and 1200 ppm, and depend strongly on the initial fluid composition. Partition coefficients for Sb and Se are in the range of 20-300. Co, Cu, Pb, Bi have lower but more variable D values ranging from 0.1 up to 50. Almost all studied elements show a high compatibility in the pyrite structure, replacing most likely either S (i.e, Se, Sb) or Fe (i.e., Co, Cu, Bi, Pb) in the crystal lattice. Unlike Au, partitioning of studied trace metals is not coupled to the As concentration of newly formed pyrite. Nevertheless, D values of Co, Cu, Se and Sb from experiments with a high concentration of trace elements (i.e., 10 ppm) decrease compared to D values from experiments done at lower concentrations (i.e. 0.1 and 1 ppm). This behavior indicates either a solubility limit of the particular element in the pyrite structure or results from an over-occupation of the potential crystal sites by other trace elements. The partition data from our experiments will help to unlock the potential to use the pyrite composition as a proxy for hydrothermal fluids.      

 

References:

1 Kusebauch et al., (2019) SciAdvances; 10.1126/sciadv.aav5891

2 Kusebauch et al., (2018) Chemical Geology; 10.1016/j.chemgeo.2018.09.027

How to cite: Kusebauch, C., Magnall, J. M., and Gleeson, S.: Partitioning of trace elements between hydrothermal fluids and pyrite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21310, https://doi.org/10.5194/egusphere-egu24-21310, 2024.

EGU24-21650 | ECS | Orals | ERE4.8

Geochemical interactions of Np and Pu with pyrite heterogeneities in Opalinus Clay in the context of deep geological repositories 

Markus Breckheimer, Samer Amayri, Dario Ferreira Sanchez, Daniel Grolimund, and Tobias Reich

The safety case for the final disposal of high-level radioactive waste in a deep geological repository involves a thorough understanding of the geochemical interactions of the potentially mobilized waste inventory with components of a proposed multi-barrier concept.

Argillaceous rock is considered as a potential host rock and final barrier to the biosphere. Opalinus Clay (OPA) from the Mont Terri rock laboratory (St-Ursanne, Switzerland) serves as a reference material for a natural clay rock. As a sedimentary rock and porous medium, OPA exhibits characteristic properties such as a low hydraulic conductivity, limiting the transport of solutes to diffusion, as well as structural and compositional heterogeneities in a range of length scales [1].

To address the influence of the potentially reactive microstructure on solute transport, spatially resolved sorption and diffusion studies of Np(V) and Pu(V,VI) with bulk OPA samples were performed, utilizing synchrotron-based microscopic chemical imaging at the microXAS beamline (Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland), simultaneously obtaining chemical information about the OPA microstructure as well as the distribution and transport patterns of Np and Pu [2-5].

In these studies, domains of pyrite, contained in OPA to about 1 wt. % as microstructural, Fe(II)-bearing heterogeneities, were identified exhibiting an enhanced reactivity regarding redox transformation and immobilization of the solute species as reduced, predominantly tetravalent and therefore less mobile species.

Further sorption studies with isolated pyrite heterogeneities, extracted from the OPA matrix as sub-100 µm sized particles, indicate a reactivity depending on the morphology of the heterogeneities, including the crystallite size distribution (framboidal) and cementing phase of these pyrite aggregates.

The results of these studies should add to an enhanced understanding of reactive transport in a natural clay rock in the context of a deep geological repository.

 

References

[1] Nagra (2002). Tech. Ber. 02-03. Projekt Opalinuston. Wettingen, Switzerland.

[2] Fröhlich, D.R., Amayri, S., Drebert, J., Grolimund, D., Huth, J., Kaplan, U., Krause, J. and Reich, T. (2012). Speciation of Np(V) uptake by Opalinus Clay using synchrotron microbeam techniques. Anal. Bioanal. Chem. 404: 2151-2162.

[3] Kaplan, U., Amayri, S., Drebert, J., Rossberg, A., Grolimund, D. and Reich, T. (2017). Geochemical interactions of Plutonium with Opalinus Clay studied by spatially resolved synchrotron radiation techniques. Environ. Sci. Technol. 51: 7892-7902.

[4] Börner, P.J.B. (2017). Sorption and diffusion of Neptunium in Opalinus Clay. PhD thesis. Johannes Gutenberg-Universität Mainz, Mainz, Germany.

[5] Kaplan, U., Amayri, S., Drebert, J., Grolimund, D. and Reich, T. (2024). Plutonium mobility and reactivity in a heterogeneous clay rock barrier accented by synchrotron-based microscopic chemical imaging. Sci. Rep., accepted.

 

Acknowledgements

Funding from the German Federal Ministry of Education and Research (BMBF) under contract number 02NUK044B, from the Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection (BMUV) under contract numbers 02E11415A and 02E11860A, and from the European Union’s Horizon 2020 project EURAD (WP FUTuRE), EC Grant agreement no. 847593, is acknowledged.

How to cite: Breckheimer, M., Amayri, S., Ferreira Sanchez, D., Grolimund, D., and Reich, T.: Geochemical interactions of Np and Pu with pyrite heterogeneities in Opalinus Clay in the context of deep geological repositories, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21650, https://doi.org/10.5194/egusphere-egu24-21650, 2024.

EGU24-21668 | ECS | Orals | ERE4.8

Pyrite oxidation rates and timing of weathering in supergene deposits: new insights from XPS approach 

Julien Poot, Alexandre Felten, Julien L. Colaux, Rachel Gouttebaron, Guillaume Lepêcheur, Gaëtan Rochez, and Johan Yans

Pyrite is one of the most common sulfides on Earth and occurs in many Cu, Pb and Zn sulfides (hypogene) ore deposits. By using XPS (X-ray Photoelectron Spectroscopy) surface and depth analyses, we propose a new experimental approach to determine the oxidation rate of pyrite in three exposure/conditions: i) air, ii) water and iii) water drip (Figure 1). Pyrite samples are almost pure and were collected from the Danube–Bouchon quarry (Hautrage, Belgium), in Barremian black clays of the Wealden facies sediments in the Mons Basin. These pyrites are nodules with cubic aggregates on the surface which were used for the different experiments.

The results reveal a maximum oxidation rate of 11.7 ± 1.8 nm day−1 for drip exposure associated with the precipitation of Fe-sulfates or/and oxides depending on the experimental conditions. These data can be extrapolated to the different zones of weathering profiles (gossan, saprolite and cementation zone). The extrapolation shows a maximum rate of 4.3 ± 0.6 m Ma−1, values consistent with those obtained by other methods such as isotope dating of weathering profiles (e.g. [1,2]). The oxidation in natural systems can vary following different factors, such as the nature of the host rock (protore) and the primary mineralogy, the porosity/permeability and fractures, the presence of an oxidizing environment, climate change over time, the action of bacteria as catalysts, …

Figure 1 - Macroscopic evolution of pyrite oxidation over time in the different experiments [3]

 

References

[1] De Putter T, Ruffet G, Yans J, Mees F (2015) Ore Geol Rev 71:350–362. https://doi.org/10.1016/J.OREGEOREV.2015.06.015

[2] Vasconcelos PM, Conroy M (2003) Geochim Cosmochim Acta 67:2913–2930. https://doi.org/10.1016/S0016-7037(02)01372-8.

[3] Poot J, Felten A, Colaux JL, Gouttebaron R, Lepêcheur G, Rochez G, Yans J (2024) Environ Earth Sci 83:9. https://doi.org/10.1007/s12665-023-11325-z

How to cite: Poot, J., Felten, A., Colaux, J. L., Gouttebaron, R., Lepêcheur, G., Rochez, G., and Yans, J.: Pyrite oxidation rates and timing of weathering in supergene deposits: new insights from XPS approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21668, https://doi.org/10.5194/egusphere-egu24-21668, 2024.

EGU24-21967 | Posters on site | ERE4.8

Pyrite in Dutch peat - influence of  paleoenvironment and current land use  

Alwina Hoving, Josh Guyat, Thilo Behrends, and Jasper Griffioen

Peatlands in the Netherlands contain high amounts of sulfur (S). Drainage of these peatlands has led to oxidation of the peat, more recently enhanced through extended drought periods from the result of climate change. Oxidation of peat leads to the mobilization of S and elevated sulfate levels in surface waters. High sulfate concentrations are considered a water quality problem and can enhance eutrophication. In this study, the S content and S speciation in Dutch peats were investigated and their relation to paleoenvironment and current land-use.

Peat samples from eight locations in an east-west section, varying over paleoenvironment, peat type, proximity to the River Rhine and the North Sea, and current land‑use were analyzed. Sequential sulfur extraction was performed to fractionate iron-monosulfide, pyrite and organic-bound sulfur. Porewater was analyzed for sulfate, iron and nitrate concentrations to investigate their influence on the S speciation.

The analytical results could be split into 3 groups. The first group consisted of peats of marine paleoenvironment which had the highest total S content. Due to limited availability of iron (Fe), sulfur was predominantly present as organic-S and <10% of S was present as pyrite. Group 2 consisted of peat from fluvial paleoenvironment origin. In these groundwater fed, nutrient rich, minerotrophic fens, pyrite made up a larger portion of total S. In group 3, the peat was influenced by the river ‘Oude Rijn’. This river was polluted with higher sulfate concentrations, relative to rain water, and also carried clay particles rich in ferrous iron. Flooding events brought Fe to the peat-forming system resulting in pyrite formation. The influence of land-use was only visible in the top layers; high concentrations of nitrate in combination with a low pyrite content and elevated sulfate concentrations were likely caused by the input of fertilizer and subsequent denitrification and oxidation of pyrite.

Overall, paleoenvironment was found to be the predominant factor controlling S content and S speciation in Dutch peats in the Western Netherlands. Particularly the presence of pyrite was related to the presence of fen reed peats and dependent on a nearby Fe source during peat formation.

How to cite: Hoving, A., Guyat, J., Behrends, T., and Griffioen, J.: Pyrite in Dutch peat - influence of  paleoenvironment and current land use , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21967, https://doi.org/10.5194/egusphere-egu24-21967, 2024.

GMPV6 – Critical metals and minerals – formation, recovery, sustainability

EGU24-652 | ECS | Orals | GMPV6.1

Circular economy in extractive industry: challenge and chance to recover fine particles produced in marble quarries exploitation 

Antonio Tazzini, Francesca Gambino, Marco Casale, and Giovanna Antonella Dino

Stone industry plays a significant role in the global economy. The 2015 production was placed in the order of 82.6 million tons with a percentage of the waste extraction and processing amount to over 70% of the gross quantity. Carbonate stones (such as marble, limestone and travertine) account for 58 % of the whole production of dimension stone, serving as primary materials for construction and ornamental uses since ancient times. Approximately 50% of waste is generated during mining operation and around 15% during processing. The disposal of marble powder, a very fine material produced by the marble industry, is one of today's global environmental problems affecting stone industry. Even if the ultra-fine calcareous particles contained in marble sludge have applications in most major industries, thanks to their chemical and physical characteristics, in most cases these materials are landfilled because of the difficulties in recovering, mainly related to local legislation and lack of appropriate protocols.
The need to reduce the use of non-renewable natural resources and, at the same time, to minimize the negative impacts on the environment, has led to an increasing interest in recovery and recycling, in line with the expressed EU policy in the Europe 2020 strategy to reduce Europe's efficiency and in the EU strategy for sustainable development. The Carrara marble basin is one of the most emblematic cases in the Italian stone industry, and it includes about one hundred quarries of colored and white marble, exploited from Roman times. Even if the new technologies have improved efficiency in quarrying and reduced the production of waste, around 50% of the extracted marbles in the Carrara basin still result in waste. Modern cutting technologies generate greater amount of finer materials and sawing residue, varying in size from sand to silt. Due to this very fine particle, it’s easy to see how this characteristic can cause problems with the stability of landfills, with consequent difficulties for their management. The aim of this research is to provide a comparison between different characteristics of marble fine waste in Carrara, both sludges deriving from quarry-cutting and stone processing, to demonstrate the feasibility of their recovery and utilization in different industrial application (i.e., mineral fillers, high value-CaCO3 products, building sector). The results obtained from analysis are promising and could lead to a possible reuse of the materials, in line with the circular economy approach. The reuse of marble waste can bring the double benefit of giving a new value to this by-product and, at the same time, partially eliminate the environmental problem caused by it. The combination of all these insights could lead to sustainable mining of the ornamental stones industry.

How to cite: Tazzini, A., Gambino, F., Casale, M., and Dino, G. A.: Circular economy in extractive industry: challenge and chance to recover fine particles produced in marble quarries exploitation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-652, https://doi.org/10.5194/egusphere-egu24-652, 2024.

EGU24-948 | ECS | Orals | GMPV6.1 | Highlight

Alternative ways to supply Rare Earth Elements: extractive waste recovery. 

Marco Casale, Xinyuan Zhao, Faten Khelifi, Alessandro Cavallo, Elio Padoan, Ke Yang, and Giovanna Antonella Dino

Rare Earth Elements (REE) are considered to be highly "critical" by the European Commission because the concentration of global supply and their use in a wide range of emerging technologies (e.g. smart phones, electric cars and wind turbines) and this at a time of increasing geopolitical tensions. According to the European Commission’s assessment, the demand for rare earth elements is expected to increase more than fivefold by 2030. Today, Europe is dependent on imports of these minerals, where China completely dominates the market, a factor which increases the vulnerability of European industry. Alternative sources of REE in Europe, such as recovery of quarrying and processing waste, are being considered.

This research, part of an italian project NODES, wich has received funding (PNRR) from the EU, about circular economy and recovery of mineral waste, focuses on the possibility to recover REE from extractive waste. The investigated area cover Piedmont Region in northern Italy. Waste materials from gneisses and granites (ranging from blocks up to residual sludge) used as dimension stones were characterized for volume, chemistry, mineralogy, and texture.

Based on the first analyses carried out, the most interesting contexts are those related to gneisses in Luserna Stone and Verbano Cusio Ossola quarrying area and to quartzites of Monte Bracco quarrying area.

Thanks to a proper treatment activity (grinding, screening and magnetic separation), these materials, present in past extractive waste facilities and in extractive waste coming from exploitation and working activities, could be used to recovery of REE. After the first phase, connected to “waste” characterisation, the following activities will be linked to processing of the richest samples to exploit (at Laboratory level) REE, and to economic issues.

An additional step will include leaching extraction tests (always at laboratory scale) to identify the best and most sustainable technique to extract and separate REE from the sampled extractive waste.

 

Key words: Rare Earth Elements, Critical Raw Materials, Supply-chain, extractive waste, mining waste, leaching, magnetic separation.

How to cite: Casale, M., Zhao, X., Khelifi, F., Cavallo, A., Padoan, E., Yang, K., and Dino, G. A.: Alternative ways to supply Rare Earth Elements: extractive waste recovery., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-948, https://doi.org/10.5194/egusphere-egu24-948, 2024.

EGU24-1809 | ECS | Posters on site | GMPV6.1

The occurrence and distribution of Scandium resources in the world-class Bayan Obo REE-Nb-Fe deposit, China 

Shuangliang Liu, Mingshi Wang, Zhaoyang Gao, Xuan Liu, Hong-Rui Fan, Alan Butcher, Yann Lahaye, Radoslaw Michallik, Ester Jolis, and Sari Lukkari

Scandium (Sc) is famous as a rare-scattered element in nature but can be anomalously enriched by the carbonatite system, especially in the Bayan Obo deposit (~0.14 Mt). However, the Sc distribution of Bayan Obo deposit is rarely revealed, which hinders resource utilization and the understanding of Sc mineralization. Thus, we comprehensively analyze the occurrence and distribution characteristics of Sc resources of Bayan Obo deposit, from deposit scale to mineral scale, based on 236 samples and 13 representatives. In the deposit scale, the Sc contents are 301-2 ppm (banded/massive type ores), 273-91 ppm (vein-type ores), 77-17 ppm (ore-hosting dolomite), and 281-1 ppm (slate/schist) for different rock types, respectively. Among them, the high-Sc rocks usually occur in the vicinity of the contact zone between the H9 slate/schist and the ore-hosting dolomite, which represents the most intently fenitization area in Bayan Obo. In the rock scale, Sc is heterogeneously scattered in rock with a small volume ratio (less than 0.1‰) of extremely high-Sc domains (Sc contents >0.3 wt. %). In contrast, Sc resources are more commonly found in aegirine and Na-amphibole, ranging from hundreds to thousands of ppm, sometimes reaching several weight percent, of banded/massive type ores and vein-type ores, and in biotite and titanite of altered slate/schist, typically in dozens of ppm. Notably, in the mineral scale, three types of individual Sc minerals are first distinguished in the Bayan Obo carbonatite deposit, that is thortveitite, aegirine-jervisite solid solution, and bazzite. Their metasomatism texture and mineral associations record two Sc migration and precipitation events in this deposit. These new reports reveal that the hydrothermal process is the main controlling factor of Sc resources in the Bayan Obo carbonatite system, and provide a scientific basis for the rational and effective utilization of Sc resources in this deposit.

How to cite: Liu, S., Wang, M., Gao, Z., Liu, X., Fan, H.-R., Butcher, A., Lahaye, Y., Michallik, R., Jolis, E., and Lukkari, S.: The occurrence and distribution of Scandium resources in the world-class Bayan Obo REE-Nb-Fe deposit, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1809, https://doi.org/10.5194/egusphere-egu24-1809, 2024.

EGU24-6141 | Posters on site | GMPV6.1

Sustainable restoration mortars in a circular economy perspective 

Susanna Mancini, Francesca Gambino, Antonio Tazzini, and Giovanna Antonella Dino

The present research focuses on one of the most complex and challenging applications of 'sustainable' mortar use in restoration. The study stems from the context of the PNRR NODES project – Spoke 2, coordinated by the University of Turin and promotes sustainable development and technologies for a “greener” future.

In modern construction, the use of mortars demands a finished product that is suitable for its use, with good aesthetic properties and durability over time. These characteristics are even more crucial in a restoration project, where compatibility with the old material comes into play. The sustainability of 'raw' materials, in this case secondary raw materials, is an issue that characterises the current historical moment. In this context, the characterisation of ancient mortars plays a fundamental role in establishing correlations with their sources and for the creation of new formulations.

The sustainability of 'alternative' mortars refers to the valorisation of local products, the use of waste materials and fully recyclable compounds, and reduced impact on human health and the environment. One of the potential compounds to use for mortar production can be collected from extractive waste associated to marble and limestone exploitation. Indeed, lime is alkaline and non-toxic, well-known as antiseptic and disinfectant. In addition, due to the low burning temperature and partial reabsorption of carbon dioxide during setting, lime, especially quicklime, is characterised by lower permanent CO2 emissions.

In this study different protocols are carried out, compared, and analysed in detail, with the aim of systematising 'alternative' restoration mortar formulations. These are based on the use of 'geomaterials', like waste from mining industry and construction and demolition. In particular, the lime-based binder is obtained from the calcination of white marble waste (quarry sludge, sawdust, etc.) from two different quarries located in Tuscany and Val d'Aosta. The aggregate used for the skeleton of the mortars can be obtained from quarry waste in Piedmont and Val d'Aosta (e.g. gneisses, granites, marbles, limestone, etc.) and/or concrete selected from treatment plants that recycle construction and demolition waste.

Finally, each formulation is evaluated regarding performance, compatibility with historic mortars and potential contribution to the circular economy.

The results of this research activity are an example of a multidisciplinary approach to the conservation and sustainable management of cultural heritage sites, where issues of scientific research, art, green building and circular economy are intertwined.

How to cite: Mancini, S., Gambino, F., Tazzini, A., and Dino, G. A.: Sustainable restoration mortars in a circular economy perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6141, https://doi.org/10.5194/egusphere-egu24-6141, 2024.

EGU24-6851 | Posters virtual | GMPV6.1

Critical metals distribution in Bauxite Residues: a Compositional Data Analysis approach 

Ouafi Ameur-Zaimeche, Rabah Kechiched, Paola Mameli, Ernesto Mesto, Giovanni Mongelli, Abdelhamid Oulad mansour, and Emanuela Schingaro

This research explores the major element control on the distribution of critical metals (CM) in red muds (RM), the residues of the Bayer process developed on bauxite ore, sampled at the Porto Vesme disposal site, Sardinia, Italy. RM represent an environmental challenge due to their high alkalinity and storage issues. The relationships between major elements and CM were assessed by Compositional Data Analysis (CoDa).

X-ray powder diffraction (XRPD) revealed predominant minerals including hematite, gibbsite, boehmite, anatase, cancrinite, sodalite, and quartz, consistent with previous studies on RM from the same site (Castaldi et al., 2008; Mombelli et al., 2019). Inductively Coupled Plasma Mass Spectrometry (ICP-MS) assessment reported the major oxides composition (wt %): SiO2 (11.9 – 22.6), Al2O3 (17.4 – 24.9), Fe2O3 (22.2 – 30.3), MgO (0.7 – 4.7), CaO (2.6 – 5.9), Na2O (3.5 – 11.5), K2O (0.2 – 0.7). Iron content averaged at 25.8 wt%, underscoring i considerable presence of iron in bauxite residues, while alumina averaged at 20.75 wt% is consistent with the large amount of Al-hydroxides detected by XRPD. Among CM, specifically the LREE, the Ce abundance (93 – 258 ppm) is a notable feature.

CoDa involved Principal Component Analysis after a transformation of raw data into centred log ratio. The PC1 and PC2 association revealed significant influence from TiO2 and Na2O on critical metals such as HREE, LREE, Sc, and Co. Noteworthy is the Bayer process involving high-temperature pressure leaching of bauxite ores with sodium hydroxide solution for the Al recovery, leaving TiO2 in the resulting residue. Other CM, such as V and Ga, are predominantly controlled by MgO.

This preliminary study suggests that RM could be a promising geo-material for a strategic CM recovery and efficiently reusing the secondary byproduct, providing a sustainable and environmentally friendly alternative to its mere disposal (Liu and Naidu, 2014).

How to cite: Ameur-Zaimeche, O., Kechiched, R., Mameli, P., Mesto, E., Mongelli, G., Oulad mansour, A., and Schingaro, E.: Critical metals distribution in Bauxite Residues: a Compositional Data Analysis approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6851, https://doi.org/10.5194/egusphere-egu24-6851, 2024.

EGU24-7191 | ECS | Orals | GMPV6.1

Rare earth elements and yttrium in Oligocene coals of Makum coalfield, Assam (North-east India) 

Shivam Sharma, Debabrata Das, Prakash Tiwari, and Ramkrishna Mondal

Rare earth elements and yttrium have attracted considerable attention in recent decade due to their crucial roles in modern technology, particularly in the production of electronics, magnets, and batteries. These elements are of particular importance for developed and developing countries, as they play a significant role in clean energy as well as their growth and development. The concentration, distribution, and modes of occurrence of rare earth elements and yttrium in coal from the Oligocene formation in the Makum coalfield were investigated in this study. The study found that the coal samples from the Makum coalfield have a low ash and high sulfur content. Furthermore, the study revealed that the total concentration of rare earth elements and yttrium in the coal samples ranged from 1.48 to 77.61 ppm, with an average of 27.49 ppm. Based on the analysis of the coal samples. Average concentration of rare earth elements and yttrium in the Makum coalfield, as observed in this study, is lower than the concentration found in world average coals. it was observed that the 60ft coal seam had a higher average LREE/HREE ratio compared to the 20ft and 8ft coal seams. This indicates variations in the distribution patterns of rare earth elements and yttrium within the different coal seams. Coals from this region show a positive europium anomaly and have a weak negative cerium anomaly, indicating a significant marine influence during their formation. The sequential leaching used in this study provided valuable insights into the modes of occurrence of rare earth elements and yttrium in the coal samples from the Makum coalfield. Having a comprehensive understanding of the proportions of rare earth elements and yttrium in different forms, such as organic, silicate-aluminate, acid soluble, ion-exchangeable, and water soluble, is crucial for the development of effective methods and technologies for the extraction of these critical elements from coal.

How to cite: Sharma, S., Das, D., Tiwari, P., and Mondal, R.: Rare earth elements and yttrium in Oligocene coals of Makum coalfield, Assam (North-east India), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7191, https://doi.org/10.5194/egusphere-egu24-7191, 2024.

EGU24-7319 | ECS | Orals | GMPV6.1

LA-ICP-MS imaging technique application on Estonian sedimentary phosphorites: Revealing REE enrichment stages and advanced ore characterisation 

Sophie Graul, Vincent Monchal, Rémi Rateau, Lauri Joosu, Marko Moilanen, Mawo Ndiaye, and Rutt Hints

The importance of rare earth elements (REEs) in high-tech industries and the growing demand for raw materials have spurred interest in exploring unconventional deposits. Sedimentary phosphorite deposits are among the most prospective, with REE extraction as a P by-product. However, these ores are highly diverse regarding ΣREE content, distribution, and nature of phosphatic materials. This study focuses on the Estonian phosphorites of the Baltic paleobasin, which constitute one of Europe's largest phosphate rock reserves and are characterised by phosphatic shell fragments deposited in nearshore settings.

Geochemical investigations were conducted on carbonate-cemented phosphorites from Toolse and Aseri deposits. The determination of REE distribution and uptake mechanisms within apatites and carbonates was addressed by LA-ICP-MS in situ imaging technique developed by Drost et al. (2018), which allows identification and discrimination of mineral phases by integrating semiquantitative compositional data through the stepwise elemental distribution. Diagenetic enrichment stages were assessed using the following pathfinder elements as pooling channels: Sr and U.

Shelly apatites have homogenous REE-distribution patterns, MREE-enriched up to 15-fold compared to the PAAS, with positive Y and Ce anomalies indicative of an early digenetic overprint traceable by the Sr distribution. The average REE content in studied apatite is 2149ppm. However, the extent of diagenetic overprint and enrichment varies locally. In Toolse, shells show lesser recrystallised textures, and the Sr- and U-depleted stages allow the tracing of pristine signals prior to deposition. In Aseri, U-sorting reveals a second, alteration-driven enrichment in which fragment edges present a ΣREE up to 7020ppm. This alteration stage is less pronounced in Toolse, where REE content reaches only 4150ppm. The distinction between Sr and U-driven enrichment is less evident due to the lower input of hydrogenic or lithogenic REE carriers. The carbonates from both localities were found to be REE depleted compared to PAAS.

Based on these observations, the compositions of the apatite species could be distinguished and modelled to characterise the deposit. The diagenetic enrichment of REE was mainly driven by the upwelling of nutrient-rich waters, Fe and Mn-(oxyhydr)oxide reductive desorption, and secondary phosphatisation and homogenisation of shells. Fluctuations of redox gradients and Fe-Mn cycles led to slight local REE variability. Developing euxinic conditions and lithogenic input endorsed a later alteration-driven uptake, resulting in highly REE-rich edges. Despite differences in enrichment level, the two deposits' REE distribution patterns are similar. Main REEs are Ce (33%), Y (21%), La (12%), Nd (16%) and Dy (3%), and are considered among the most critical elements. On average, U concentrations are 92ppm in Aseri and 31ppm in Toolse, and toxic elements (Cd, Zn, Th) are found in trace amounts.

The study introduces a combined technique based on LA-ICP-MS and empirical distribution function data analyses as a powerful, accurate, cost-effective tool for determining REE distributions. It allows visualisation at different scales, representative measurements and a first approach to semi-quantifying elements. The method could provide insights into factors that control genesis in low-grade sedimentary ores and determine their potential valorisation routes.

How to cite: Graul, S., Monchal, V., Rateau, R., Joosu, L., Moilanen, M., Ndiaye, M., and Hints, R.: LA-ICP-MS imaging technique application on Estonian sedimentary phosphorites: Revealing REE enrichment stages and advanced ore characterisation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7319, https://doi.org/10.5194/egusphere-egu24-7319, 2024.

The Sardinia region has a longstanding tradition in ornamental granite extraction, reaching its production peak in the 1990s when it became Italy's leading granite producer, accounting for 90% of the national production [1]. However, the industry faced a decline starting from the mid-2000s due to the entry of other competitors into the global market and due to significant infrastructure issues on the island [1]. The 2008 financial crisis further reduced global granite demand and in the subsequent years, compounded by the events of the COVID-19 pandemic, prolonged the crisis in the sector. In Italy, granite production plummeted from over 2 million metric tons in 2011 to just under 200,000 metric tons in 2022 [2].
Granite extraction has a striking impact on the Sardinian landscape, with landfills of granite blocks, visible from kilometers away, contributing to significant landscape degradation. These, in addition, affect plans to develop the unique archaeological sites of the Domus de Janas and contribute to soil depletion. 
The European Critical Raw Materials Act to future supply chains is crucial for Europe's green and digital transition, in line with the European Green Deal that identified recycling as part of the supply solution. In this context, recognizing potential opportunities for recycling these waste materials could aid in advancing the objectives of the European Union, enhance the aesthetic quality of the Sardinian landscape, and contribute to revitalize the granite extraction industry in Sardinia.
This study focuses on the circular economy in a granite quarry located in the municipality of Buddusò (province of Sassari, Sardinia). Active for about 40 years, this quarry has accumulated significant amounts of granite waste from which feldspar, quartz and rare earth elements can be extracted. This research presents the results of geochemical, petrographic, and mineralogical analyses conducted on granite waste samples from the quarry under study. In addition, potential recycling solutions for this material in the context of Critical Raw Material supply are discussed.

References:

[1] Careddu, N.; Siotto, G.; Marras, G. The Crisis of Granite and the Success of Marble: Errors and Market Strategies. The Sardinian Case. Resources Policy 2017, 52, 273–276. https://doi.org/10.1016/j.resourpol.2017.03.010.
[2] Istituto Nazionale di Statistica - Istat. Production in Value and Quantity per Single Product - Granite and Similar Rocks, Rough, without Shape. Accessed 18/12/2023. https://esploradati.istat.it/databrowser/#/it/dw/categories/IT1,Z0600IND,1.0/IND_PRODUCTION/DCSP_PRODCOM/IT1,115_168_DF_DCSP_PRODCOM_2,1.0

How to cite: Aquilano, A., Marrocchino, E., and Vaccaro, C.: Granite waste produced in quarries exploitation in northern Sardinia (Italy): recycling chances within the context of Critical Raw Material supply, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8434, https://doi.org/10.5194/egusphere-egu24-8434, 2024.

SEM-EDS and polarized optical microscopy analysis of granite blocks taken from decorative rocks quarry waste landfills in Sardinia were used in mining prospecting to evaluate potential unconventional sources of critical raw materials (CRMs). Achieving the goals outlined in the European Green Deal regarding the green and digital transition may face significant challenges due to the substantial increase in demand for CRMs in the near future so access to CRMs is a strategic security issue for the European Union.

Because of the similar chemical properties that characterize Rare Earth group elements among themselves, there are few effectively exploitable deposits in the world. Predominantly in carbonatite complexes and pegmatitic granitoid bodies, the subtle variations in the properties of RE (Rare Earth) group elements allow significant fractionation and economically exploitable enrichment of small intrusive bodies and/or intrusive veins consisting of one or more REE minerals, such as allanite, REE oxides, apatites, and carbonates.

Sardinia's ornamental granite quarries have in the past generated high concentrations of unmarketable waste (mostly pegmatite bodies and veins with REE-enriched late-magmatic and deuteric mineralogical phases). The huge amount of these waste accumulations has resulted in high land consumption and landscape distortions, but with the increased REE demand they now represent an important resource, as they can contribute to the implementation of the EU Critical Raw Materials Act.

This study reports the results of SEM-EDS investigations combined with polarized optical microscope observations conducted on thin sections of granite obtained from waste samples from the numerous leucogranite quarries of Buddusò (Northern Sardinia, Italy). These granites are composed primarily of quartz, plagioclase, K-feldspar, and biotite, with accessory minerals including zircon, epidote, titanite, ilmenite, apatite, and xenotime. Feldspars have recently been included in the list of Critical Raw Materials[2]; therefore, the identification of solutions for their exploitation (which represent a significant portion of the rocks investigated) could provide a strong contribution to the needs of the European Union. Epidotes often appear in these rocks as allanite enriched in light rare earth elements.

In this context, it could be very interesting to evaluate the possibility of applying physical mineral separation methodologies to obtain, on the one hand, mineral concentrates containing Rare Earth Elements for the extractive metallurgy industry. On the other hand, feldspars have recently been included in the list of Critical Raw Materials [1]; therefore, identifying solutions for their exploitation (which represent a significant portion of the investigated rocks) could provide a strong contribution to the needs of the European Union.

This study of the quartz and feldspar phases and REE concentrations in accessory minerals will be useful in optimizing the physical separation methodologies of minerals useful to obtain CRMs for industry and the ceramic and glass manufacturing sectors.

Reference:

[1] Grohol, M., C. Veeh, DG GROW, e European Commission. «Study on the Critical Raw Materials for the Europe - Final Report». Luxembourg: European Union, 2023.

How to cite: Vaccaro, C., Aquilano, A., and Marrocchino, E.: SEM-EDS and Polarized Optical Microscope Analysis of Granite Quarry Waste to Reveal Potential Unconventional Sources of Critical Raw Materials, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8511, https://doi.org/10.5194/egusphere-egu24-8511, 2024.

EGU24-16645 | Posters on site | GMPV6.1

Geochemical tracing of Nd magnets – a possible future tool to improve sustainable sourcing of critical raw materials? 

Jakob K. Keiding, Nolwenn Coint, Benjamin Heredia, Nynke Keulen, Yann Lahaye, and Xuan Liu

Raw material supply chains are intricate and complex systems that often suffer from a lack of transparency. To enhance sustainability in mineral supply, there is an urgent need to rectify this transparency deficit. Traceability, which involves tracking a product through different stages of production, transformation, and commercialization, from its origin to its end-of-life, including potential recycling, could be a crucial facilitator for increased transparency.

Nd magnets (also known as NdFeB magnet) are the strongest permanent magnet type known and serve as critical components in green technologies like windmill turbines and electric motors for vehicles. While Nd magnets offer numerous advantages, their production involves the use of rare earth elements (REE), critical raw materials that lack supply chain transparency, standards, and certification schemes regarding environmental and social impacts, and governance. The objective of this study is to investigate whether there are distinct chemical characteristics associated with Nd magnets and to determine the feasibility of establishing a correlation between a magnet and unidentified information, potentially linking it to a plausible source.

Nd magnets have been systematically collected for the purpose of tracing their material origins. Two distinct categories of Nd magnets were assessed for this investigation. The first category comprises novel magnets with documented production years (ranging from 1999 to 2023) and varying grades marked by different Nd contents. The second category consists of magnet scraps lacking specific information. Our study employed a comprehensive approach, incorporating automated quantitative mineralogy (AQM), Scanning Electron Microscope spectroscopy element mapping (SEM-EDS) to examine microtextures and major element content, and LA-ICP-MS analyses for trace elements and Nd isotopes.

Analyzing these magnets revealed noticeable compositional distinctions among samples, both in terms of manufacturing sources and production years. Four distinct groups of trace elements were identified in the novel magnets, aiding in the differentiation of various production year groups. These groups include Ti, Cr, Se, La, Cr, Nd, Gd, Yb (Group 1), B, Eu, Tb (Group 2), Al, As, Ge, Pr, Sm, Dy, Tm (Group 3), and Mn, Ho (Group 4). Nd isotope analyses indicated a broad present-day epsilon Nd values, ranging from -30 to -7, with some degree of inter-sample overlaps. This extensive range appears to surpass the typical coverage of REE deposits. Higher values suggest the potential incorporation of REEs from South China ion-absorption deposits, while lower values hint at the involvement of REEs from Olympic Dam (Australia) and/or Mountain Pass (US).

These preliminary findings contribute with valuable insights into the diverse origins and compositions of Nd magnets, suggesting that geochemical fingerprinting could emerge as a pivotal traceability tool for assessing the origin of Nd magnets in the future.

How to cite: Keiding, J. K., Coint, N., Heredia, B., Keulen, N., Lahaye, Y., and Liu, X.: Geochemical tracing of Nd magnets – a possible future tool to improve sustainable sourcing of critical raw materials?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16645, https://doi.org/10.5194/egusphere-egu24-16645, 2024.

EGU24-16673 | ECS | Orals | GMPV6.1

Use of Interferometric Synthetic Aperture Radar Techniques as a remote tool for Mineral Extraction Sites Monitoring  

Francesco Falabella, Antonio Pepe, Krištof Oštir, and Fabiana Calò

This work addresses the preliminary achievements of the Horizon Europe European project S34I1 (Secure and Sustainable Supply of Raw Materials for EU Industry) (https://s34i.eu) that aims to increase the autonomy of Europe over raw materials resources through research and development of new data-driven methods devoted to the analysis of Earth observation data.

Among the different activities of the project, one of the major contributions is related to the systematic monitoring of mining site instabilities by developing and applying advanced multi- temporal interferometric SAR (InSAR) techniques for the generation of long-term deformation time series. To this purpose, an InSAR multi-grid technique for efficient processing of sequences of differential SAR interferograms (particularly, phase unwrapping operations) has been carried out directly at the native high-resolution spatial grid without any model or assumption on deformation.

Experiments were carried out at the Gummern, Austria, extraction site by processing two sets of ascending and descending SAR datasets collected by the EU Copernicus Sentinel-1A/B sensors from October 2014 to March 2023. The line-of-sight (LOS)-projected ground displacement time series were generated by inverting the unwrapped single-look interferograms using the Small BAseline Subset (SBAS) algorithm. Consequently, non-linear and seasonal patterns that could indicate a sudden failure of the surface can be identified with millimetre precision. A post-operation step was also performed over the group of georeferenced common targets as seen from complementary geometries (i.e., ascending and descending orbits) to compute from LOS-projected ground deformations the long-term 2-D (up-down, east-west) ground displacement time series. To this aim, conventional and new combination methods are applied by assuming the north-south displacements do not significantly contribute to the observed LOS measurements.

1This study is funded by the European Union under grant agreement no. 101091616, project S34I – SECURE AND SUSTAINABLE SUPPLY OF RAW MATERIALS FOR EU INDUSTRY, coordinated by Ana C. Teodoro.

How to cite: Falabella, F., Pepe, A., Oštir, K., and Calò, F.: Use of Interferometric Synthetic Aperture Radar Techniques as a remote tool for Mineral Extraction Sites Monitoring , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16673, https://doi.org/10.5194/egusphere-egu24-16673, 2024.

EGU24-17463 | ECS | Orals | GMPV6.1

Stirred-tank reactor bioleaching of nickel and cobalt from Brazilian laterite ores 

Stefanie Hetz and Axel Schippers

Laterite ore deposits in Brazil and other tropical countries harbor large amounts of nickel and cobalt resources, along with other critical raw materials. The conventional methods of recovering nickel and cobalt, such as pyrometallurgy or high-pressure acid leaching, entail high energy, reagent costs, and expensive equipment. To address this, the German-Brazilian project BioProLat aims to develop an integrated, low-energy, and environmentally friendly biohydrometallurgical process for metal recovery from Brazilian laterite ores.

The process involves leveraging acidophilic bacteria that use sulfur as an electron donor, coupling sulfur oxidation to the reduction of ferric iron, ultimately converting insoluble metal compounds into water-soluble forms. This generates sulfuric acid, creating the necessary acidic conditions to keep iron and other metals soluble. Laboratory-scale bioreactor experiments optimized parameters like pH, temperature, and a suitable bacterial consortium for bioleaching nickel and cobalt. Results from aerobic bioleaching of laterite with a consortium of Acidithiobacillus thiooxidans strains showed an extraction of 85% for both cobalt and nickel. Mineralogical and geochemical analyses were conducted to identify mineral phases, which are attacked by bioleaching, and estimate the portions of cobalt and nickel released by bioleaching of different mineral phases. The goal is to scale up the optimized process, converting untapped ores and limonite stockpiles into valuable resources and unlocking new raw material reserves by enhancing metal recovery from existing mines.

How to cite: Hetz, S. and Schippers, A.: Stirred-tank reactor bioleaching of nickel and cobalt from Brazilian laterite ores, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17463, https://doi.org/10.5194/egusphere-egu24-17463, 2024.

EGU24-19639 | Orals | GMPV6.1 | Highlight

Quarry dust an essential component in the pyrometallurgical recovery of valuable materials from mixed fine-grained waste 

Axel D. Renno, MD Naziat Hossain, Anna Magdalena Baecke, Abrar Kabir, and Stefan Dirlich

Within the FINEST project (https://finest-project.de/) we tackle the use and management of finest particulate anthropogenic material flows in a sustainable circular economy. Subproject 3 "FINEST Disperse Metals" has set itself the goal of safely mixing various fine and ultra-fine-grained material flows that accumulate as waste during various industrial processes and extracting metallic raw materials from them in a subsequent multi-stage pyrometallurgical process, as well as generating a safe slag that can be disposed of without monitoring.

The idea of mixing different fine-grained waste streams arose from the experience that the search for economically and ecologically sustainable forms of recycling for the individual types of waste often failed despite promising approaches. This is usually due to individual parameters of the chemical or phase composition. The mixing we are aiming for allows us to select the technological parameters much more freely and to react to the rapid changes that are typical of waste streams.

We will implement this concept using three different material streams:

  • So-called shredder fines from plastics, car and WEEE recycling
  • Metallurgical fly ash from non-ferrous metallurgy
  • Quarry dust and dust from concrete recycling.

 

The experimental work is preceded by a comprehensive characterization of the material flows in terms of chemical and phase composition, general physical parameters such as particle size distribution, particle shapes and flowability as well as any potential hazards. Based on this, both the mixing behavior and the pyrometallurgical parameters are modeled.

We use quarry dust for two main purposes. Their main contribution is to act as slag formers in the pyrometallurgical processing of the mixtures in the plasma furnace. This should be combined with the lowest possible liquidus temperatures and viscosities of the slag system. We are currently using four different quarry dusts from active quarries in the Free State of Saxony for our investigations (1 granite, 2 granodiorites and 1 amphibolite) as well as material from the concrete recycling of an extensive demolition project in Dresden.

Optimized mixing ratios between the individual quarry dusts and various metallurgical flue dusts were determined as part of the modeling using FactSageTM.  The behavior during mixing of the material flows was initially investigated theoretically using model materials. The mixing steps were visualized using X-ray computed tomography.

How to cite: Renno, A. D., Hossain, M. N., Baecke, A. M., Kabir, A., and Dirlich, S.: Quarry dust an essential component in the pyrometallurgical recovery of valuable materials from mixed fine-grained waste, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19639, https://doi.org/10.5194/egusphere-egu24-19639, 2024.

EGU24-21695 | ECS | Orals | GMPV6.1 | Highlight

Recovery of Metals from Municipal Solid Waste Incineration Plants Wastes: A Comparative Case Study of Pre- and Post-Pandemic Periods 

Junaid Ghani, Katerina Rodiouchkina, Ilia Rodushkin, Enrico Dinelli, Valerio Funari, Thomas Aiglsperger, Lena Alakangas, and Emma Engström

Municipal Solid Waste Incineration (MSWI) plants are of great concern, generating solid by-products, namely Fly Ash (FA) and Bottom Ash (BA). These MSWI residues have received significant attention for environmental concerns and the recovery of valuable elements, minerals, and secondary raw materials. The potential recovery of elements in MSW are crucial for circular economy and environmental sustainability (Han et al, 2021; Funari et al, 2016). Therefore, available types of fly ashes samples, i.e., lime- and soda-doped fly ash from bag filters following electrostatic precipitation, and quenched BA samples were sampled during pre- (2013, 2020) and post-pandemic period (2021, 2022) from two grate-furnace MSWI plants, located in Ferrara (FE) and Forlì (FC) cities in Italy. The sample preparation and elemental analysis were performed at ALS Scandinavia laboratory as a part of an international research collaboration between University of Bologna, Luleå University of Technology, and ALS Scandinavia. In this study, we aimed to determine and compare the elemental composition in MSWI samples by Inductively Coupled Plasma-Sector Field Mass Spectrometry (ICP-SFMS) to assess metal abundance by enrichment factor and elemental flows using substance flow analysis and MSWI systems’ mass balance (Brunner and Rechemberg, 2004). Our results showed that recovery of valuable elements (Al, Fe, Si, Zn, and Cu) was high after strong digestion method for all the FA and BA samples. Overall, little variation in elemental composition of FA and BA in both selected periods (pre-pandemic vs post-pandemic) suggests a similar input flow of urban waste. Enrichment factors (EF) show enrichment of Zn, Cu, Al, Fe, Mg, Ca, Na, K, and potentially toxic elements like Pb, Cd in both FA and BA. The chondrite normalized REE patterns of FA and BA are relatively similar suggesting that the BA and FA feeding material are mostly geogenic materials, with possible anthropogenic fluctuation for Ce, Tb, and Yb. The upper continental crust (UCC) normalization patterns were consistent for most elements. In contrast, Ba, K, P, and La patterns vary, likely showing an anthropogenic signal. Mass balance assessment showed that the waste streams can host from low to high concentration of strategic elements as an alternative source of value in the circular economy.

 

References

  • Funari, V., Bokhari, S.N.H., Vigliotti, L., Meisel, T. and Braga, R., 2016. The rare earth elements in municipal solid waste incinerators ash and promising tools for their prospecting. Journal of Hazardous materials, 301, pp.471-479.
  • Han, S., Ju, T., Meng, Y., Du, Y., Xiang, H., Aihemaiti, A. and Jiang, J., 2021. Evaluation of various microwave-assisted acid digestion procedures for the determination of major and heavy metal elements in municipal solid waste incineration fly ash. Journal of Cleaner Production, 321, p.128922.
  • Brunner, P.H., Rechberger, H., 2004. Methodology of MFA. In: Practical Handbook of Material Flow Analysis. Lewis Publishers, Boca Raton London New York Washington, D.C., pp. 34–166, ISBN: 1-5667-0604-1.

How to cite: Ghani, J., Rodiouchkina, K., Rodushkin, I., Dinelli, E., Funari, V., Aiglsperger, T., Alakangas, L., and Engström, E.: Recovery of Metals from Municipal Solid Waste Incineration Plants Wastes: A Comparative Case Study of Pre- and Post-Pandemic Periods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21695, https://doi.org/10.5194/egusphere-egu24-21695, 2024.

GMPV7 – Advances in igneous petrology

EGU24-530 | ECS | Orals | GMPV7.1

Water content in primary magma compositions and mantle source of chromitites in Mesoarchean Nuggihalli greenstone belt (India) 

Haitao Ma, Jingsui Yang, Pengjie Cai, Mudlappa Jayananda, Dongyang Lian, and Krishnasamy Ravindran Aadhiseshan

Chromitites, found in Archean greenstone belts as the oldest ultramafic rocks, offer critical insights into the early Earth's evolution. Water plays a fundamental role in aggregation and mineralization of chromite, yet the water content of parental magma of chromitite remains unclear. This study present petrologic and elemental data on chromitites from the 3.3-3.1 Ga Nuggihalli greenstone belt, Western Dharwar craton (India), and address origin of chromitites in Archean greenstone belts particularly water contents in primary magmas. Major and trace element data of chromites and clinopyroxenes from chromitites coupled with thermobarometry, and hygrometry calculation, as well as numerical modeling reveal that the chromites are high-Cr chromites (Cr# 68.1-78.6) with low TiO2 (0.19%-0.29%), Al2O3 (9.10%-13.13%), and Ga (4.24-10.37 ppm), similar to the parental melts of high-Cr podiform chromites and boninites in modern ophiolites. The clinopyroxenes are augites with high Mg# (93-95) which corresponds to equilibrated melts with the Nuggihalli chromitites having high Mg# values (79-86), resembling ancient komatiitic or picritic magmas (75-90), crystallized in a primary magma environment. Thermobarometry and hygrometry calculation suggest that the clinopyroxenes could form at temperatures of 1194-1221℃ and pressures of 0.7-5.8 kbar with high water contents (~2.4-2.6 wt.%), exceeding water contents in mid-ocean basalts (MORB) and oceanic island basalts (OIB) source. Numerical modeling of rare earth elements indicates that moderate degrees of partial melting (1%~20%) of hydrated spinel lherzolite mantle (water content: ~478-5408 ppm). The primary magmas of the 3.3-3.1 Ga Nuggihalli chromitites are characterized by enrichment of water contents (~2.4-2.6 wt.%) and high field strength elements (HFSEs, e.g., Nb and Hf), demonstrating high comparability with boninites and arc magmas. Furthermore, the rock associations including ultramafic rocks with chromitites, high-Mg basalts and sheets of gabbro-anorthosites in the Nuggihalli greenstone belt may represent the relic of oceanic lithosphere. This declares that the 3.3-3.1 Ga Nuggihalli chromitites could have formed at a forearc basin on a subduction system.

How to cite: Ma, H., Yang, J., Cai, P., Jayananda, M., Lian, D., and Aadhiseshan, K. R.: Water content in primary magma compositions and mantle source of chromitites in Mesoarchean Nuggihalli greenstone belt (India), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-530, https://doi.org/10.5194/egusphere-egu24-530, 2024.

EGU24-1730 | ECS | Orals | GMPV7.1

Unravelling metal mobilising processes in the Kolumbo volcano Au-rich SMS using Pb isotopes. 

Simon Hector, Qasid Ahmad, Clifford G. C. Patten, Massimo Chiaradia, Stephanos Kilias, Paraskevi Nomikou, and Jochen Kolb

Gold-rich seafloor massive sulfides (SMS) form in various marine hydrothermal environments, including continental volcanic arcs, where magmatic fluids may contribute significantly to the metal budget of the hydrothermal system. To track the origin of metals and unravel the mineralising processes at play in Au-rich SMS formation (i.e. hydrothermal leaching of country rocks or magmatic degassing), we investigated the volcanic/basement rocks and Au-rich SMS of the Kolumbo submarine volcano (Greece). We combine in-situ Pb isotope analysis of the sulphide mineralisation and whole rock Pb isotope analysis of volcanic and basement rocks. During magmatic evolution, crustal material assimilation slightly shifts Pb isotope ratios toward more radiogenic values defining a differentiation trend from andesite to rhyolite. The mineralisation, dominated by pyrite with episodic galena, sphalerite, chalcopyrite and Sb-Pb sulfosalts formation, has Pb isotopes ratios pointing toward an igneous source. Galena and Sb-Pb sulphosalts have Pb isotopes ratios similar to volatile-saturated trachytic magma indicating Pb mobilisation during magmatic degassing, while Pb isotopes ratios in pyrite matches volatile-poor post-degassing rhyolite, suggesting Pb mobilisation by hydrothermal leaching of rhyolite. Lead isotope ratios reveals that Pb at Kolumbo is sourced from igneous rocks but the mechanisms for metal transfer vary from rhyolite leaching by hydrothermal fluid circulation to episodic input of magmatic fluid able to provide Ag, As, Au, Cu, Hg, Pb, Sb, Tl in addition to Pb. The magmatic evolution of Kolumbo highlights the diversity and complexity of metal mobilising magmatic-hydrothermal processes involved in Au-rich SMS formation.

How to cite: Hector, S., Ahmad, Q., Patten, C. G. C., Chiaradia, M., Kilias, S., Nomikou, P., and Kolb, J.: Unravelling metal mobilising processes in the Kolumbo volcano Au-rich SMS using Pb isotopes., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1730, https://doi.org/10.5194/egusphere-egu24-1730, 2024.

EGU24-3818 | Posters on site | GMPV7.1

Fluid-flux versus decompression melting – the Tonga arc – Lau back arc system 

Christoph Beier, Simon Turner, Philipp A. Brandl, and Karsten M. Haase

Subduction zones are key regions of mass exchange between the Earth’s crust and mantle, and magmas in the sub-arc mantle form as a result of the release of volatiles from the subducting slab, i.e. fluid-flux melting. Introducing unique geochemical tracers (e.g., Large Ion Lithophile Elements) into the depleted mantle wedge allows tracing of the flow of material underneath the island arcs. Back arc spreading centres form as a result of slab-rollback, and here melts form due to decompression melting similar to those forming at mid-ocean ridges. Back arc systems situated angular to their adjacent island arc encompass a range of slab depths and provide a unique means to assess the compositional changes as a function of distance to the active arc and above the subducting slab. The Valu Fa Ridge (VFR), Eastern Lau (ELSC) and Central Lau (CLSC) spreading centres are situated at an increasing distance from the active Tonga arc from south to north. Here, we present new major, trace and volatile element data along with radiogenic isotope and U-Th-Ra disequilibria along the VFR and ELSC and across the VFR. A systematic change of, e.g., Ba/Nb, Nb/La, H2O contents and Pb isotopes with increasing distance between the back arc and the Tonga arc could be interpreted to reflect the slab-related metamorphic dehydration reactions. However, we do not observe a gradual change in geochemical compositions at a distance <100 km between the arc and the backarc, suggesting that the decompression and fluid-fluxed melting regimes overlap. At distances of >100 km between the arc and back arc, the occurrence of (230Th/238U) excess suggests that melting is due to decompression and that the systematic decrease in subduction influence observed with increasing distance is likely the result of melting of hydrous, ancient slab remnants during rollback. We conclude that the melting regimes between the ELSC and Tonga island arc separate at ~100 km total distance, as evident from the stepwise change in trace element and isotope geochemistry. The decrease in subduction-related signatures along the VFR and ELSC results from an overlap of the melting regimes and melt mixing between the arc and back arc in which the melting of the depleted mantle underneath the back arc becomes more prominent with increasing distance.

How to cite: Beier, C., Turner, S., Brandl, P. A., and Haase, K. M.: Fluid-flux versus decompression melting – the Tonga arc – Lau back arc system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3818, https://doi.org/10.5194/egusphere-egu24-3818, 2024.

EGU24-3858 | ECS | Orals | GMPV7.1 | Highlight

Determining the relative potential of future igneous activity in Germany – a multi-criteria approach 

Lisa Rummel, Alexander Bartels, Franz May, Maximilian O. Kottwitz, and Tobias S. Baumann

Future volcanic activity within or around distributed volcanic fields is difficult to determine, as many processes affect the melt formation in the mantle and the ascent of melt through the lithosphere. Depending on the external and internal forces and mechanisms, the igneous activity (i.e., shallow intrusive along with extrusive magmatism) can be long lasting or be interrupted by several phases of dormancy. To determine the long-term (i.e., next 1 Myr) relative potential of igneous activity in Germany we therefore suggest to consider the characteristics of various parameters including, among others, seismic anomalies in the mantle, earthquakes, degassing of mantle fluids, ground motion, depth of Moho and LAB, tectonic activity, modelled melt potential based on numerical simulations, and past volcanic eruptions. Thereby, numerical simulations can be used to quantify uncertainties of various parameters describing the structural and thermal state of the lithosphere and the upper mantle. Melt potential calculations including these uncertainties as well as compositional variations of mantle rocks can be used to identify areas of actual critical state with regard to possible future volcanic eruptions below Central Europe.

Based on all 20 parameters investigated, a semi-quantitative multi-criteria method was developed and finally applied to differentiate regions of relative potential for future igneous activity in Germany. Although, most parameters are not uniquely related to magmatic processes, the presence of values exceeding the defined thresholds of any single parameter enhances the potential of future igneous activity at specific locations. Parameter properties are scaled between 0 and 10 within their range of significance (above/below a defined threshold value) to allow their comparison and combination. Weighting factors for individual parameters are used based on the results of expert surveys. However, an index map with statistically determined weighting factors shows the insensitivity of the proposed method in terms of chosen weighting factors.

The results of the multi-criteria method can be used to identify suitable regions for a safe repository for high-level radioactive waste, where areas have to be excluded, which might be directly affected by future magmatic processes. In this context, we computed Germany-wide index (“hazard”) maps, where the index values represent a combination of all 20 parameters. The resulting index maps show that a higher relative potential of future igneous activity occurs not only in regions affected by Quaternary volcanism, but also in and around older Cenozoic volcanic fields or even in regions that have not been affected previously by Cenozoic volcanism. These observations indicate the possible longevity of a geodynamic framework that facilitates magmatic activity over large time scales (millions to tens of millions of years).

How to cite: Rummel, L., Bartels, A., May, F., Kottwitz, M. O., and Baumann, T. S.: Determining the relative potential of future igneous activity in Germany – a multi-criteria approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3858, https://doi.org/10.5194/egusphere-egu24-3858, 2024.

Petrographic studies of the multi-textured layered gabbro series of the lower crustal section recovered from U1415P were conducted to determine the mechanism of orthopyroxene formation in lower crustal gabbros drilled in the Hess Deep rift near the East Pacific Rise. In a particular horizon of the series (U1415P 6R-1 to 6R-2), homogeneous medium-grained troctolite and fine-grained spinel-bearing heterogeneous olivine gabbro occur in proximity.

The samples from the Hole1415P 6R are divided into homogeneous troctolite parts with medium-grained equigranular textures and spinel-bearing heterogeneous olivine gabbro parts with poikilitic textures (irregularly shaped fine-grained plagioclase characrysts enclosed in Ol-oikocrysts and Cpx-oikocrysts). The wide variation in TiO2 content against nearly constant Mg# and Cr2O3 of clinopyroxene in these rocks is quite different from the compositional trend of clinopyroxene in layered mafic intrusions explained by the fractional crystallization of magma.

Recently, Yang et al. (2019) conducted a reaction experiment between MORB melts and troctolite and reported microtextures and mineral chemical compositions of the experimental products. In the experiment, fine-grained plagioclase was found to be poikilitically enclosed in olivine and clinopyroxene in the melt infiltration zone within troctolite near the boundary between troctolite and melt. The poikilitic textures and the oikocristic clinopyroxene compositional variations in the Hess Deep spinel-bearing olivine gabbro are very similar to those in the reaction experiment by Yang et al. (2019). These indicate that the heterogeneous olivine gabbro of the Hess Deep was formed by a melt-rock (or crystal mush) reaction.

              In addition, the multiphase solid inclusions of Cpx-Pl assemblage with basaltic magma composition and Opx-bearing multiphase solid inclusions with composition of high-Mg basaltic-andesite to andesite are enclosed in Cr-spinel from the spinel-bearing heterogeneous olivine gabbro. The presence of Opx-bearing multiphase solid inclusions indicate that the injection of SiO2-rich melt different in composition from the troctolite-forming magma has occurred. The SiO2-rich melt reacted with the troctolite to form spinel-bearing heterogeneous olivine gabbro. Our results may suggest that the sheeted sills model, in which magma of various compositions intrudes into the crust, is a more appropriate mechanism for the formation of the lower oceanic crust.

How to cite: Hoshide, T. and Kondo, K.: Formation of spinel-bearing layered gabbros by the reaction between the basaltic crystal mush and high-Mg andesitic melts in the lower oceanic crust, East Pacific Rise (IODP Exp. 345 U1415P) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4328, https://doi.org/10.5194/egusphere-egu24-4328, 2024.

EGU24-5290 | ECS | Posters on site | GMPV7.1

From build-up to caldera collapse: High resolution modelling of large scale magmatic systems 

Pascal Aellig, Albert de Montserrat, and Boris Kaus

In order to understand the cause of a caldera-forming eruption, it is crucial to study the pre-eruptive processes, from build-up to the collapse. In recent years, the cyclicity of large-scale magmatic systems and their corresponding caldera collapses has been described through various geochemical and petrological studies. Numerical modelling studies have investigated the collapse stage using a pressurised cavity or gas-filled chamber, studying the evolution of the surrounding lithosphere by inflating and deflating the chamber. Another modelling approach involves investigating the displacement effects of moving a piston-shaped object.

In this study, we use a multi-physical numerical modelling approach to investigate different aspects of the caldera cycle, including the accumulation of magma, the evolution of stress, the strain rate and the dynamics within the forming magmatic system. To achieve this, we couple an open-source thermal evolution magma intrusion code with a Stokes solver. The coupling allows for the evaluation of thermal and volumetric changes in the magmatic system, taking into account the complex interaction between magma dynamics and the surrounding host rock. The use of nonlinear visco-elasto-plastic rheology enables the assessment of fracturing and thermal effects on the lithosphere, which create downward propagating weak zones that are later utilised as eruption channels. These faults not only provide pathways but are also associated with the caldera collapse stage of the eruption cycle, which leads to geomorphological transformations of the surface.

Our approach is also applicable for assessing the evolution of current magmatic systems taking into account their topography. The model is applied to the well-studied area of the Toba caldera in Sumatra. The magma is injected into areas where seismic inversion studies have identified a melt phase. This allows for an assessment of the system's evolution and provides insights into an active magmatic system. Additionally, it serves as a reference for correlating and referencing our model with observational data.

How to cite: Aellig, P., de Montserrat, A., and Kaus, B.: From build-up to caldera collapse: High resolution modelling of large scale magmatic systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5290, https://doi.org/10.5194/egusphere-egu24-5290, 2024.

EGU24-7044 | ECS | Orals | GMPV7.1

Voluminous low-temperature S-type granite formation in the New England Orogen, eastern Australia during back arc evolution 

Xiaofang He, Martin Hand, Laura J. Morrissey, and William J. Collins

Crustal melting leading to the formation of S-type granite is typically considered a characteristic of collisional regimes. However, the formation of S-type granites does not necessarily require overt crustal thickening. Instead, voluminous granite generation can occur where burial of fertile H2O-rich material occurs in high heat flow environments. One obvious setting that has these attributes is rapidly developing back arc regimes. Settings such as these are ideal to generate large volumes of S-granite without necessarily requiring appreciable crustal thickening.

The Bundarra and Hillgrove granite intrusions in the southern New England Orogen, eastern Australia are part of an Early Permian garnet/cordierite-bearing S-type granite batholith (>1800km2) generated in a back-arc setting linked to the easterly (outboard) migration of a W-dipping subduction zone. This setting facilitated rapid and thick accumulation of compositionally immature detritus from the active arc and the inboard continent, creating a fertile system for granite genesis driven by back arc high heat flow. Deposition of the precursor sedimentary volume occurred between 360 and 300 Ma, with partial melting and batholithic-scale melting and granite accumulation occurring between ca. 298-288 Ma. Seismic reflection data suggests the currently preserved crustal column in places comprises ~30% granite, with the current level of denudation ranging between ~ 3-5kbar.

Ti in zircon and quartz, and zircon saturation temperatures suggest granite-formation temperatures may have been as low as 700-750 °C. Mineral equilibria modelling using protolith compositions considered presentative of the sedimentary protoliths suggest melting at the scale indicated by regional mapping and geophysics is only possible in a water rich environment, either from trapped water that was not expelled during burial in the back arc, or for an external source.

The geochemistry of the Bundarra and Hillgrove suites shows significant variability in their maficity. When comparing the modelled magma/melt compositions at different water contents the variation in maficity shows the granites are more mafic than the modelled melt compositions, suggesting much of the mafic content is entrained from the source. This is supported by the occurrence of hexagonal shaped biotite aggregates which contain occasional garnet relics.

We interpret that water-fluxed melting played an important role in the genesis of back arc hosted S-type granites in eastern Australia, and it may apply to the genesis of many other S-type granite batholiths. Variable entrainment of the residual mineral assemblage within a cool, hydrous silicic melt can probably explain the compositional range of New England and other S-type granite batholiths.

How to cite: He, X., Hand, M., Morrissey, L. J., and Collins, W. J.: Voluminous low-temperature S-type granite formation in the New England Orogen, eastern Australia during back arc evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7044, https://doi.org/10.5194/egusphere-egu24-7044, 2024.

South Shetland Islands (western Antarctica) host widespread magmatism through the Meso-Cenozoic as a result of the subduction of the Phoenix plate along the South Shetland trench. With the logistical support of the Czech Antarctic Research Center and in-kind assistance from TÜBİTAK MAM Polar Research Institute, geological fieldwork was conducted on the Fildes Peninsula in order to understand the magma evolution beneath western Antarctica. This study presents preliminary results from field, petrographic and geochemical studies obtained from the volcanic and intrusive rocks in Fildes Peninsula- King George Island.

Fildes Peninsula represents the southwestern parts of King George Island which is located at the northeastern tip of the South Shetland Islands. The dominant lithologies in the study area are Paleocene- Eocene volcanic and intrusive rocks, with a minor presence of sedimentary rocks. The volcanic rocks cropping out on Fildes Peninsula are referred to as the Jasper Hill, Agate Beach, Block Hill and Long Hill formations. They mostly display similar compositions changing from basalt to basaltic andesite lavas and accompanied by pyroclastic rocks (tuffs and volcanic breccias). Intrusive rocks are composed of gabbro-micro gabbro stocks and diabase dykes. Petrographic investigations show that volcanic and intrusive rocks in the area mostly display disequilibrium textures such as sieve textures and embayments in plagioclase and pyroxenes, patchy and oscillatory zoning in different generations of plagioclases. Geochemically, all volcanic rocks show similar characteristics; they are represented by basic rocks that mostly display tholeiitic affinity. Their MgO and SiO2contents range from 3.04 to 6.18 and 44.80 to 48,47wt. %, respectively. The samples are slightly enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE) compared to N-MORB and they display depletions in Nb and Ti elements which are the typical indicators of subduction zone magmatism. All volcanic rocks display low Y and high Sr/Y contents which are typical for adakites.  These adakites are specifically represented by “low-silica adakites” due to their low SiO2 (<48 wt. %). They also have low Zr and high Zr/Y abundances suggesting garnet in their source. These major- trace element characteristics and published Sr-Nd-Pb isotope compositions may collectively suggest that the adakites of Fildes Peninsula were originated from the partial melting of the mantle-wedge which was metasomatized by subduction processes along the South Shetland trench.

How to cite: Ünal, A., Altunkaynak, Ş., and Nývlt, D.: Source characteristics of the adakitic lavas and intrusions in Fildes Peninsula, King George Island (South Shetland Islands, Antarctica), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8392, https://doi.org/10.5194/egusphere-egu24-8392, 2024.

Tertiary migmatizations are pivotal events in the geologic history of the Menderes Massif, one of the world's most extensively studied core complexes. In northern Menderes Massif (Gördes Submassif) several granitic intrusions were emplaced into the migmatitic core rocks. They are mostly monzogranitic and granodioritic in composition and cut by associated pegmatitic dikes. These granitoids exhibit holocrystalline granular and porphyritic textures, characterized by plagioclase and, occasionally, biotite phenocrysts. The mineral composition of the granodiorites comprises 35–45% plagioclase, 30–35% quartz, 15–25% K-feldspar, and 5–10% biotite, with ± 5–8% muscovite. In contrast, the monzogranites are distinguished by a reduced plagioclase/K-feldspar ratio. Secondary phases include opaque minerals and sericite, with muscovite also observed. Accessory phases are zircon minerals. The granites exhibit an ASI index between 1 and 1.1, classifying them as slightly peraluminous I-type granites. They predominantly display high-K calc-alkaline characteristics and, less frequently, calc-alkaline nature. The Eu/Eu* ratio of these granites varies from 0.8 to 1.4. Trace element patterns suggest a possible derivation from basaltic and greywacke source rocks. Notably, high LaN/YbN ratios (reaching up to 107 ppm) and elevated Sr/Y ratios (up to 108 ppm) imply the presence of garnet or amphibole in the source. DyN/YbN and LaN/YbN ratios and their relationships specifically indicate the presence of garnet, rather than amphibole in the mafic source region. These data imply the crucial role of lower crustal melting in the formation of granitoids and the evolutionary history of the Menderes Core Complex.

How to cite: Kamacı, Ö., Ünal, A., and Altunkaynak, Ş.: Geochemical Implications for Tertiary Lower Crustal Melting in Northern Menderes Massif (Western Anatolia): Preliminary results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9011, https://doi.org/10.5194/egusphere-egu24-9011, 2024.

EGU24-9163 | ECS | Orals | GMPV7.1 | Highlight

The 2021-23 Fagradalsfjall fires: geochemical and petrological insights 

Alberto Caracciolo, Edward W. Marshall, Enikő Bali, Heini H. Merill, Sæmundur A. Halldórsson, Simon Matthews, Olgeir Sigmarsson, Sóley M. Johnson, Guðmundur H. Guðfinnsson, Jóhann Gunnarsson Robin, Araksan A. Aden, and Byron F. Pilicita Masabanda

After 7000 years of quiescence, three eruptions occurred in 2021, 2022 and 2023 AD in the Fagradalsfjall volcanic system, in Reykjanes peninsula in southwest Iceland. Looking at the eruptive history of the peninsula in the past 4000 years, characterized by ~400-year-long rifting episodes at time intervals of 800-1000 years, the current magmatic reactivation could mark the onset of a new rifting episode. The 2021 eruption, which is a olivine tholeiite lava (mean WR MgO=9.5 wt%), was directly sourced from Moho depths, providing unique insights into the deep parts of the Fagradalsfjall volcanic system1. Furthermore, the 2021 eruption featured remarkable geochemical changes in the first 50 days, characterized by great variability in geochemical tracers used as a proxy for mantle enrichment such as K2O/TiO2  and La/Yb, in the range 0.14-0.26 and 2.1-4.51. After this period and to the end of the eruption, incompatible element ratios record only minor fluctuations2. The 2022 and 2023 AD lavas have lower WR MgO, in the range 8.4-8.7 wt%, with the 2023 eruption being slightly less differentiated. Incompatible element ratios do not change throughout the 2022 AD and 2023 AD eruptions. However, the 2022 and 2023 lavas are slightly more enriched than any 2021 lava, with K2O/TiO2 and La/Yb in the range 0.24-0.28 and 4.3-4.9 respectively. Hence, the 2022 and 2023 lavas are very similar to the most enriched 2021 lavas. The crystal cargo in the Fagradalsfjall lavas is made of plagioclase, olivine and clinopyroxene macrocrysts, with olivine and clinopyroxene becoming increasingly rare in the 2022 and 2023 products. Plagioclase macrocryst cores are in the range An84-91 throughout the 2021, 2022 and 2023 eruptions, without significant variability between eruptions. Conversely, the olivine and clinopyroxene cargo varies over the course of the Fagradalsfjall fires. In the 2021 products, they are mostly in the range of Fo86-89 and Mg#84-91, respectively—more primitive than in the 2022 and 2023 eruptions and out of equilibrium with the melts that carried them to the surface. In the 2022 and 2023 products, most of olivine and clinopyroxene crystals are in the range Fo84-87 and Mg#83-86, respectively. These are found to be in chemical equilibrium with carrier melts, suggesting that they likely represent true phenocrysts of the 2022-23 crystal cargo, as opposed to plagioclase crystals. This compositional variability of the crystal cargo suggests different mush erosion and/or incorporation processes throughout the Fagradalsfjall fires, with preferential incorporation of mush plagioclase crystals and less efficient mush erosion processes over time.

1Halldórsson, S. A. et al. Rapid shifting of a deep magmatic source at Fagradalsfjall volcano, Iceland. Nature 609, (2022).

2Marshall, E. W. et al. Rapid geochemical evolution of the mantle-sourced Fagradalsfjall eruption, Iceland. Abstract, AGU 2021.

How to cite: Caracciolo, A., Marshall, E. W., Bali, E., Merill, H. H., Halldórsson, S. A., Matthews, S., Sigmarsson, O., Johnson, S. M., Guðfinnsson, G. H., Gunnarsson Robin, J., Aden, A. A., and Pilicita Masabanda, B. F.: The 2021-23 Fagradalsfjall fires: geochemical and petrological insights, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9163, https://doi.org/10.5194/egusphere-egu24-9163, 2024.

EGU24-11344 | ECS | Posters on site | GMPV7.1

Magma Storage, Differentiation and Transfer in Vertically Extensive Magmatic Systems 

Catherine Booth, Matthew Jackson, Steve Sparks, and Alison Rust

Geophysical, geochemical, and petrological studies indicate that magma storage and chemical differentiation can occur at various depths in the continental crust. Examination of exposed ancient magmatic systems reveal a continuum from a refractory lower crust to a silica-rich upper crust, prompting a debate on the mechanisms governing magma storage and differentiation in vertically extensive magmatic systems.

Conceptual models for magma storage and chemical differentiation within the crust range from (i) a low crystallinity magma body, where differentiation occurs primarily by fractional crystallisation and partial melting of the crust, to (ii) a trans-crustal high crystallinity ‘mush’ reservoir consisting of a porous crystal matrix with melt in the pore space. Chemical differentiation in these mush reservoirs is driven by the compaction of the crystal matrix, buoyant upward reactive flow of melt, and partial melting of the surrounding crust.

We use a numerical model to investigate magma storage and chemical differentiation in the continental crust. The model assumes a magmatic system sustained by the intrusion of mantle-derived basalt into the lower crust.  We find that intrusion of basalt creates a high crystallinity reservoir in the lower crust. Reactive flow and compaction cause melt to accumulate at the top of the reservoir, creating a layer of low crystallinity, chemically differentiated magma.  Buoyancy overpressure causes this magma to  evacuate via dikes and we assume the magma intrudes the mid-crust to form a second high crystallinity mush reservoir. Reactive flow and compaction once again lead to the accumulation of low-crystallinity, evolved magma at the top of the reservoir that can evacuate and intrude the upper crust, driving volcanic eruptions or forming shallow plutons.

The compositional evolution of magma as it ascends through the system is influenced by the flux of the parental basalt and the fertility of the crust. A higher basalt flux leads to warmer reservoirs that evacuate less evolved magma. Reservoirs in infertile crust that cannot melt are formed only of hot, parental magma, and also evacuate less evolved magma. Partial melting of fertile crust allows melt to percolate upwards and accumulate in cooler crust, leading to the evacuation of evolved (silicic) magma.

In most of our simulation cases, the reservoirs remain as discrete bodies in the lower- and mid-crust, with magma transfer occurring via dikes; a trans-crustal reservoir does not form. The lower-crust reservoir evacuates mafic to intermediate magma, whilst the cooler mid-crust reservoir primarily evacuates evolved, silicic magma, consistent with vertical compositional trends in exposed, ancient magmatic systems. Both reservoirs comprise primarily low-melt fraction mush, consistent with geophysical imaging of contemporary systems.  Layers of accumulated low-crystallinity magma are transient and likely too thin to resolve in geophysical data. The predicted volume, composition, and frequency of episodic magma intrusions into the upper crust are consistent with observed data from large volcanic eruptions. Our results suggest that reactive flow in multiple mush reservoirs controls magma storage and differentiation.

How to cite: Booth, C., Jackson, M., Sparks, S., and Rust, A.: Magma Storage, Differentiation and Transfer in Vertically Extensive Magmatic Systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11344, https://doi.org/10.5194/egusphere-egu24-11344, 2024.

EGU24-11411 | ECS | Posters on site | GMPV7.1

Study of the variations of the feeding system at Mt. Etna during the paroxysmal activities by using infrasonic data. 

Gabriele Amato, Vittorio Minio, Mariangela Sciotto, Laura Spina, Leighton M. Watson, and Andrea Cannata

The maim objective of this work is to investigate the structure of the superficial portion of the plumbing system at Mt. Etna in terms of interconnection among the conduits and internal variations linked to eruptive activity. For this purpose, the lava fountains that occurred in the years from 2011 to 2015 were taken into consideration, for a total of 51 events, and the infrasonic signals recorded by two stations were analysed. We extracted the infrasonic events, and analysed the evolution in time of the spectral content by using normalized and non-normalized pseudospectrograms, peak and mean frequency values. In addition, the sources of the events were located. We noted how, although the eruptions took place at South-East and Voragine craters, the infrasonic events recorded before and after the lava fountains are mostly generated by the North-East Crater. Most of the energy of these events is comprised in the frequency range 0.1 – 2 Hz. Furthermore, in most of the lava fountain episodes, we observed a decrease in the frequency peaks of the infrasonic events after the eruptions. To interpret the variations of the plumbing system responsible for these spectral changes, as well as the interconnection among the conduits feeding the main craters, we model the infrasonic events from the North-East Crater as an acoustic resonance of the crater and conduit, whose length changes with time as magma ascends or descends in the conduit.

How to cite: Amato, G., Minio, V., Sciotto, M., Spina, L., Watson, L. M., and Cannata, A.: Study of the variations of the feeding system at Mt. Etna during the paroxysmal activities by using infrasonic data., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11411, https://doi.org/10.5194/egusphere-egu24-11411, 2024.

The composition of MgO-rich basalt produced during the six-months long 2021 eruption at Fagradalsfjall, Reykjanes Peninsula, varied from those with low K2O/TiO2 and incompatible element contents to basalt enriched in incompatible elements with high K2O/TiO2 over a timespan of a month, explained by binary mixing of different mantle melts (Halldórsson et al., 2022). For the rest of the eruption, the basalt composition varied in a periodic manner as illustrated by long-lived radiogenic isotope ratios. For example, the periodicity of 87Sr/86Sr from early May to middle of September 2021 was 52 days, likely representing the time elapsed from the final melt mixing at depth (the moment of acquiring the measured isotope composition) until eruption at surface. Preliminary results on Th isotope ratios in the 2021 Fagradalshraun yield relatively high Th isotope ratios [(230Th/232Th) = 1.30] in the first lava emitted (the low K2O/TiO2 basalt) relative to basalt erupted at the end of the eruption [(230Th/232Th) = 1.18]. While this observation could be explained by slower mantle melting, excellent correlation between Th and Nd isotope ratios confirms the importance of binary mixing of melts from a depleted mantle source (with high Th and Nd, and low Sr isotope ratios) with melt(s) from enriched mantle lithology (having lower Th and Nd, and higher Sr isotope ratios) before magma ascent and eruption. Consequently, mantle heterogeneity, melt aggregations and mixing dominate the composition of the erupted basalt, rather than the duration of mantle melting. Correlation between Sr isotope ratios and time-averaged discharge rate indicate mantle source fertility control on the discharge rate during the 2021 eruption.  Both the 2022 and the summer 2023 eruptions started with a stronger discharge rate than that of 2021 and produced basalt of similar composition as that emitted in September 2021, interpreted as a result of an establishment of crustal magma accumulation zone since at the end of the 2021 eruption. Moreover, whether the exhaustion of the low K2O/TiO2 and 87Sr/86Sr magma reservoir led to the end of the 2021 eruption remains to be explored.

How to cite: Sigmarsson, O.: Basaltic magma dynamics during the 2021-2023 eruptions at Reykjanes Peninsula, Iceland, constrained by Sr, Nd and Th isotope ratios, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12434, https://doi.org/10.5194/egusphere-egu24-12434, 2024.

EGU24-13197 | ECS | Orals | GMPV7.1

The transcrustal plumbing system of Large Igneous Provinces: Insights from glomerocrysts and melt inclusions 

Manfredo Capriolo, Sara Callegaro, Frances Deegan, Renaud Merle, Heejin Jeon, Martin Whitehouse, László Aradi, Malte Storm, Paul Renne, Don Baker, Jacopo Dal Corso, Robert Newton, Csaba Szabó, Bruna Carvalho, Nasrrddine Youbi, and Andrea Marzoli

The magma plumbing system throughout the entire transcrustal section of Large Igneous Provinces (LIPs) is still poorly understood. Among the most voluminous LIPs, the Central Atlantic Magmatic Province (CAMP [1], ca. 201 Ma) and the Deccan Traps (DT [2], ca. 66 Ma) coincided in time with end-Triassic and end-Cretaceous mass extinctions, respectively. Glomerocrysts containing abundant primary melt inclusions from both CAMP and DT basaltic lava flows were investigated via a multi-analytical approach (confocal Raman microspectroscopy for volatile species within bubbles, electron microprobe for major element compositions, secondary ion mass spectrometry for oxygen isotope compositions, Synchrotron X-ray microtomography and optical microscopy for microstructural analysis). The analysed glomerocrysts are dominated by augitic clinopyroxenes, and represent portions of crystal mushes. The analysed melt inclusions consist of an intermediate to felsic composition glass and CO2-bearing bubbles, and represent relics of interstitial melts and fluids entrapped during the evolution of these crystal mushes. The different volume proportions in terms of bubbles within melt inclusions indicate a heterogeneous entrapment, implying that melts were entrapped along with already exsolved fluids. The MgO-rich composition of glomerocrysts and whole rocks is in contrast with the SiO2-rich composition of melt inclusions, unveiling disequilibrium conditions of entrapment, as supported by thermodynamic modelling too. The oxygen isotope compositions of clinopyroxene in glomerocrysts indicate that they crystallized from mafic melts with normal (i.e., mantle-like) to mildly low δ18O values. However, the oxygen isotope compositions of glass in melt inclusions indicate that they entrapped distinct, intermediate to felsic melts with normal to extremely high δ18O values, which may be explained by variable degrees of crustal assimilation and partial mixing in an open system. Hence, the oxygen isotope compositions of glass in melt inclusions also suggest that the CO2 within their coexisting bubbles may be derived partly from the mantle and partly from assimilated crustal melts as well. Overall, geochemical data and microstructural observations reveal the presence of multiphase (i.e., solid + liquid + gaseous phases) crystal mushes within the magma plumbing system of both CAMP and DT, and shed light on the origin of carbon and its transfer from the mantle to Earth’s surface.

 

[1] Marzoli et al. (1999), Science 284, 616–618.

[2] Sprain et al. (2019), Science 363, 866–870.

How to cite: Capriolo, M., Callegaro, S., Deegan, F., Merle, R., Jeon, H., Whitehouse, M., Aradi, L., Storm, M., Renne, P., Baker, D., Dal Corso, J., Newton, R., Szabó, C., Carvalho, B., Youbi, N., and Marzoli, A.: The transcrustal plumbing system of Large Igneous Provinces: Insights from glomerocrysts and melt inclusions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13197, https://doi.org/10.5194/egusphere-egu24-13197, 2024.

EGU24-13201 | ECS | Posters on site | GMPV7.1

The importance of magmatic degassing at a mineralized, submarine volcano: The case of Conical Seamount, Papua New Guinea 

Louis-Maxime Gautreau, Thor Hansteen, Maxim Portnyagin, and Philipp Brandl

Conical Seamount is an active submarine volcano of the Tabar-Lihir-Tanga-Feni island chain (TLTF) in north-eastern Papua New Guinea. This island chain is located within the New Ireland Basin and the related alkaline to shoshonitic magmas are ascending through a thick sedimentary sequence. The TLTF hosts several Cu-Au mineralized volcanic centers. Conical Seamount is a rare example of a submarine epithermal-style mineralization and is considered to be a juvenile analogue of the Ladolam world-class gold deposit located on the nearby island of Lihir.

Recent research assessed important crustal magmatic processes as precursors for the mineralization at Conical Seamount. More specifically, the presence of a degassing crustal magma chamber has been found to be critical for the metal concentration and transfer into the epithermal system. This may explain why other seamounts in the TLTF island chain remain barren (unmineralized).

Here we present new volatile (H2O, CO2, F, Cl, S) as well as major and trace element data of clinopyroxene-hosted melt inclusions. These data along with fluid inclusion data allow us to further constrain the volcanic plumbing system, more specifically the pressure (i.e., depth) of the crustal magma chamber, the degassing stage and sulfide saturation processes. Chalcophile elements and Au in particular are scavenged within sulfides concomitant with the magmatic fluid exsolution, leading to ideal conditions for the transfer of metals into the ore-forming system.

 

How to cite: Gautreau, L.-M., Hansteen, T., Portnyagin, M., and Brandl, P.: The importance of magmatic degassing at a mineralized, submarine volcano: The case of Conical Seamount, Papua New Guinea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13201, https://doi.org/10.5194/egusphere-egu24-13201, 2024.

EGU24-13352 | ECS | Orals | GMPV7.1

Quantifying crustal growth in the Lau arc-backarc system through gravity inverse modelling 

Christopher Galley, Alan Baxter, Mark Hannington, Michael King, Erin Bethell, Peter Lelièvre, Marc Fassbender, and John Jamieson

The formation and evolution of arc-backarc systems govern crustal production in some of the most volcanically and hydrothermally active environments on Earth. Geologic mapping of these systems is increasingly possible by interpretation of emerging ship-based and global geophysical datasets. Although specific rock types cannot be confidently identified from a single physical property, the relative density changes across a region can provide information about the composition of the crust and how it was formed, for example, indicating whether old crust was produced along the volcanic arc or at a back-arc spreading center. This study presents the first complete three-dimensional density model of the Lau Basin and Tofua arc-backarc system in the southwest Pacific Ocean. Seafloor density and crustal thickness maps were produced that reveal changes in crustal composition and growth rates throughout the basin and along the volcanic arc. Crustal thickness varies greatly between the different centers of accretion (indicated here by assemblages), reflecting seafloor spreading and subsurface melt accumulation below volcanic fields. Volumetric growth rates were calculated for each assemblage, corresponding to their respective contribution to basin expansion. The highest crustal density and growth rates are thought to be related to a mantle-derived melt source entering the basin from the north around the edge of the subducting Pacific Plate. The inverse modelling approach used in this study can be applied to global gravity datasets to characterize and quantify the density and thickness of the crust anywhere in the oceans.

 

How to cite: Galley, C., Baxter, A., Hannington, M., King, M., Bethell, E., Lelièvre, P., Fassbender, M., and Jamieson, J.: Quantifying crustal growth in the Lau arc-backarc system through gravity inverse modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13352, https://doi.org/10.5194/egusphere-egu24-13352, 2024.

EGU24-13454 | ECS | Posters on site | GMPV7.1

Eruption age and magma evolution history of the Sinsudo Tuff in the Cretaceous Gyeongsang Basin, Korea 

Yong-Un Chae, Youn-Joong Jeong, Jong-Sun Kim, Sujin Ha, Young Ji Joo, Seungwon Shin, and Hyoun Soo Lim

On the Korean Peninsula, located in the eastern region of East Asia, the Gyeongsang Basin, a representative sedimentary basin formed during the Cretaceous Period, occupies about a fourth of South Korea. In the Gyeongsang Basin, the Kusandong Tuff (ca. 103 Ma; Kim et al., 2013), a representative marker bed, is distributed across approximately 200 km from north to south. About 2.5 m-thick tuff layer also develops in Sinsu and Changseon islands, located in the southern part of the basin. There is controversy as to whether it is the southernmost extension of the Kusandong Tuff or a separate tuff body. To resolve this, a total of 4 samples were collected from two islands, and LA-MC-ICP-MS zircon U-Pb dating was performed. As a result, all samples were slightly contaminated with common lead, and lower intercept ages of ca. 99 Ma were calculated, indicating a systematically younger than the reported ages of Kusandong Tuff (ca. 103 Ma). And zircons used in age calculations are largely divided into two domains accoring to the significant differences in brightness in cathodoluminescence (CL) images. Based on the combination of these domains, zircons show: 1) dark overall, 2) dark in the core with bright rims (known as reverse zoning), and 3) only bright oscillatory zoning with/without some inherited cores. In general, dark domains have a uranium content of ca. 3000-7000 ppm, while bright ones range from 34-541 ppm. And in the CL image, some boundary of the dark domains in the cores had melted and infiltrated by bright ones. To understand the evolutionary history of the magma that formed these zircons, trace and rare earth elements were analyzed using LA-ICP-MS. The results indicate that the dark domains of zircons were formed in relatively highly evolved and cooler magma, while the bright domains of zircons were formed in less evolved and hotter magma. To summarize the magma evolution model, crystallization of dark domains occurred first in relatively highly evolved magma, and then domains showing bright and distinct oscillatory zoning were formed with the injection of less evolved magma from deeper sources. At the same time, bright domains grew on the rims of existing dark zircons due to the injected magma. It is thought that the new magma injected into the existing magma chamber caused an increase in internal pressure, which ultimately led to the volcanic eruption. Considering the dating results, it is believed that all of these processes occurred over a short period of time, roughly limited to about 99 Ma on the geological time scale.

How to cite: Chae, Y.-U., Jeong, Y.-J., Kim, J.-S., Ha, S., Joo, Y. J., Shin, S., and Lim, H. S.: Eruption age and magma evolution history of the Sinsudo Tuff in the Cretaceous Gyeongsang Basin, Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13454, https://doi.org/10.5194/egusphere-egu24-13454, 2024.

EGU24-14492 | ECS | Posters on site | GMPV7.1

Geochemistry of the Northern Andean Volcanic Zone, Colombia 

María P. Marroquín-Gómez, Mauricio Ibañez-Mejía, and Aleisha C. Johnson

The North Volcanic Zone of the Andes is the result of an overall uniform subduction of the Nazca Plate beneath the South American Plate in Ecuador and Colombia; however, age, composition, and thickness of the continental crust and the distance between the trench and arc, among other components of this subduction system, vary significantly along this segment of the Andes (Stern, 2004). Those changes are most likely responsible for differences in the geochemical characteristics of volcanic products in different parts of the Colombian arc as discussed in Monsalve (2020). Although several works related to the isotopic geochemistry of the volcanic products have been carried out in Ecuador (Bryan et al., 2006; Chiaradia et al., 2009, references therein), there are few records of the same type of data for Colombia and those available focus on the SW part of the arc (Marín-Cerón, 2007). This study seeks to fill the gap and use this new data to elucidate processes of magma generation and differentiation currently occurring under the northern Andes. Whole rock major elements, trace elements, and 176Hf/177Hf analyses from main volcanic centers along the Colombian arc are used to track lithospheric and crustal processes of mixing, assimilation, and fractional crystallization as well as the main source materials and contributions in magma generation in the subduction zone. From a broader view, this new data helps to discuss regional comparisons of the geochemical expressions in the Andean arcs caused by different tectono-magmatic processes.

 

Bryant, J.A., Yogodzinski, G.M., Hall, M.L., Lewicki, J.L. & Bailey, D.G. (2006). Geochemical constraints on the origin of volcanic rocks from the Andean Northern Volcanic Zone, Ecuador. Journal of Petrology, 47(6): 1147–1175.

Chiaradia, M., Müntener, O., Beate, B., & Fontignie, D. (2009). Adakite-like volcanism of Ecuador: lower crust magmatic evolution and recycling. Contributions to Mineralogy and Petrology, 158, 563-588.

Marín–Cerón, M.I. (2007). Major, trace element and multi–isotopic systematics of SW Colombian volcanic arc, northern Andes: Implication for the stability of carbonate–rich sediment at subduction zone and the genesis of andesite magma. Doctoral thesis, Okayama University, 140 p. Okayama, Japan.

Monsalve–Bustamante, M.L. (2020). The volcanic front in Colombia: Segmentation and recent and historical activity. In: Gómez, J. & Pinilla–Pachon, A.O. (editors), The Geology of Colombia, 97–159.

Stern, C.R. (2004). Active Andean volcanism: its geologic and tectonic setting. Revista geológica de Chile, 31(2), 161-206.

How to cite: Marroquín-Gómez, M. P., Ibañez-Mejía, M., and Johnson, A. C.: Geochemistry of the Northern Andean Volcanic Zone, Colombia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14492, https://doi.org/10.5194/egusphere-egu24-14492, 2024.

EGU24-14593 | ECS | Posters on site | GMPV7.1

Crystallisation history of magmatic sulphide droplets in intra-oceanic arcs 

Wiebke Schäfer, Manuel Keith, Marcel Regelous, Reiner Klemd, and Martin Kutzschbach

Valuable understanding regarding the behaviour of chalcophile elements in magmatic systems can be gained by examining magmatic sulphide droplets, which are the solidified remnants of previously immiscible sulphide liquids [1-2]. We analysed the trace element composition of sulphide droplets by LA-ICP-MS, creating a comprehensive data set for volcanic and plutonic rocks from intra-oceanic arcs.

We observed a significant enrichment of elements like Zn, Cd, Sn, Te, and Bi in sulphide droplets from lava samples compared to those hosted by gabbro xenoliths, which cannot be attributed to the fractionation of olivine, spinel, or magnetite [3-5]. These compositional differences are likely the result of changing sulphide droplet composition during cooling and solidification of the silicate melt. This process involves continuous sulphide segregation or re-equilibration with the silicate melt. A key aspect of our suggested model is sulphide droplets' resorption or partial remelting, particularly of the Cu-Fe-rich intermediate solid solution proportion. This process is driven by pressure decrease during magma ascent, leading to an increase in sulphur solubility in the silicate melt [6], which potentially liberates elements like Cu, Au, Zn, Bi, Te, and Ag from the sulphide droplet to the silicate melt. Our findings further suggest that subsequent magma stagnation and fractional crystallisation lead to a second stage of sulphide saturation, likely dominated by the elements previously liberated from the intermediate solid solution.

The complex crystallisation history indicates that sulphide droplet formation during silicate melt evolution in subduction-related settings is a non-equilibrium process. We further propose that volatile saturation preceding the second stage of sulphide segregation from a silicate melt enriched in chalcophile elements liberated from intermediate solid solution could result in particularly metal-rich fluids (e.g., Cu, Au, Bi, Te) with a high ore-forming potential in magmatic-hydrothermal environments.

 

[1] Wood, B. J. and Kiseeva, E. S. (2015), Earth and Planetary Science Letters, 424, 280-294. [2] Patten, C. et al. (2013), Chemical Geology, 358, 170–188. [3] Distler, V. V. et al., (1983), Initial Reports of the Deep Sea Drilling Project, 69, 607-617. [4] Keith, M. et al. (2017), Chemical Geology, 451, 67–77. [5] Schäfer, W. et al., in prep. [6] Peach et al. (1990), Geochimica et Cosmochimica Acta, 12, 3379-3389.

How to cite: Schäfer, W., Keith, M., Regelous, M., Klemd, R., and Kutzschbach, M.: Crystallisation history of magmatic sulphide droplets in intra-oceanic arcs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14593, https://doi.org/10.5194/egusphere-egu24-14593, 2024.

EGU24-15105 | ECS | Orals | GMPV7.1 | Highlight

Impact of crystallinity evolution on volatile phase transport in hydrous magmatic intrusions during the magmatic-hydrothermal transition 

Thierry Solms, Thomas Driesner, Olivier Bachmann, and Isabelle Chambefort

Exploiting high-enthalpy geothermal systems is an important component of expanding low-carbon electricity generation in volcanically active regions. One possibility to enhance power production is harnessing supercritical geothermal resources that underlay conventional high-enthalpy systems, but utilizing them requires a deeper understanding of the physical and chemical processes taking place at the magmatic-hydrothermal transition immediately below the supercritical reservoir.         
In water-rich, silicic magma bodies, the exsolution of a magmatic volatile phase (MVP) can result from magma crystallization. In a certain crystal fraction range, the MVP can be abundant enough to percolate through permeable pathways within the magma mush and coalesce at the intrusion’s apex, where fluid pressure build-up can lead to hydro-fracturing.   
For the case of a prolate, shallow-seated (situated at 4 to 7 km, 0.94 km width), water-rich silicic magma body, we conducted 2D numerical fluid flow simulations, exploring the transient patterns of MVP exsolution and flow inside and out of the cooling intrusion, and hydrothermal fluid flow outside of it. We examined the impact of varying temperature-crystallinity trends on the timing of MVP production, the formation of permeable pathways, overpressure build-up and hydro-fracturing.       
Our findings show that for silicic magmas, where crystallization primarily takes place at low magmatic temperature (near the haplogranitic solidus), permeable pathways (“channels”) form within the mush, but fluid pressures at the intrusion apex are not sufficient to expel MVPs forcefully. In contrast, for chemically less evolved melts, with crystallization shifted to higher temperatures, overpressure build-up is large enough to periodically release MVPs via hydro-fractures into the ductile carapace around the intrusion and beyond.       
This periodic MVP release from the magma contributes a small fraction of the total water in the geothermal system above the cooling intrusion, where it is mixed with meteoric water. At typical borehole depths for conventional, high-enthalpy geothermal systems (e.g. 2 km), the contribution of magmatic water is usually ≤ 5%, and its thermal effect is negligible. 
The observed degassing patterns could elucidate differences in degassing style between hydrous magmatic systems of different chemical compositions, e.g. the silicic intrusions of the Central Taupō Volcanic Zone versus the more mafic Whakaari White Island volcano (both in New Zealand). Further, these insights into the timing and extent of hydro-fracturing and the related advection of metals and ligands are key to understand the conditions relevant to the formation of magmatic-hydrothermal ore deposit such as granite-related tin-tungsten deposits and porphyry-copper deposits.

How to cite: Solms, T., Driesner, T., Bachmann, O., and Chambefort, I.: Impact of crystallinity evolution on volatile phase transport in hydrous magmatic intrusions during the magmatic-hydrothermal transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15105, https://doi.org/10.5194/egusphere-egu24-15105, 2024.

The origin and extent of crustal material in arc magmas are critical for tracing the crust-mantle interaction at subduction zones. Arc volcanic rocks often have a characteristic range of trace elements and isotopic compositions that constrain the influx of crustal material, such as hydrous fluids derived from slab dehydration, melts of the subducted plate's veneer sediments, or heterogeneous mélange. Especially, the traditional geochemical proxies struggle to investigate the contribution of tectonic melange into the enriched subarc mantle source. Lithium and molybdenum isotope compositions provide a potential means of tracing the different components to the mantle wedge in subduction zones.

Here, we report Li-Mo isotope compositions of the Fushui mafic complex in the Qinling orogen, central China, to trace their source nature and to constrain metasomatic component(s) transferred during the early Paleozoic subduction event. The Fushui mafic rocks exhibit typical arc-type trace element features and enriched radiogenic isotope compositions, suggesting a mantle source had incorporated subducted compenents. The Fushui rocks also exhibit a light Li isotope composition providing direct evidence for the contribution of dehydrated serpentinites and eclogite. The variable Mo isotope values further suggest the mantle source has been metasomatized by aqueous fluid and hydrous melt. This study, therefore, confirms the transportation of dehydrated oceanic plates from footwall to hanging wall and its critical role in the subarc mantle source. The interpretation provides a new perspective to study the recycling of subducted oceanic lithosphere and associated petrogenesis of arc magmatism.

How to cite: Hu, P.: Lithium and molybdenum isotope systematic for Fushui complex and implications for the recycled oceanic crust in the source of arc magmatism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15179, https://doi.org/10.5194/egusphere-egu24-15179, 2024.

EGU24-16851 | ECS | Orals | GMPV7.1

Numerical simulation of the effect of solidifying crusts on lava propagation and arrest 

Janine Birnbaum, Einat Lev, Marc Spiegelman, Jackie Kendrick, and Yan Lavallée

Silicate melts have highly temperature-dependent viscosity and at low temperatures, crystalize and/ or vitrify. The development of a solid rind or carapace results in a transition in deformation mechanism from dominantly viscous to elastic or plastic. This transition has a significant impact on the rate and style of emplacement of lava flows and domes, including on the construction of channelized flows, over-steepened margins, and advance due to lava flow breakouts. These processes are especially important in subaqueous, subglacial, and extraterrestrial environments in which cooling is accelerated, resulting in a current lack of models specifically calibrated for these environments.

We develop a numerical model, Viscous-Elastic Numerically Unified Solver for Solidifying flows (VENUSS), for cooling and solidifying free surface flows. The model couples a viscous fluid interior with an elastic shell whose thickness grows in response to cooling. We use a numerically unified approach that solves for the velocity field in the viscous and elastic fields together. Interface tracking is provided using the level set method combined with an extended finite element (XFEM) approach to avoid costly remeshing. Simulations are performed in two-dimensional planar or axisymmetric conditions which allows for modeling natural geometries such as lava flows and lava domes. This approach presents an improvement upon existing models of lava flow and dome evolution that either neglect or greatly simplify the mechanical effects of a crust.

As a validation/test of our model, we simulate the advance of meter-scale experimental lava flows from the Syracuse Lava Project. We find the flow propagation is highly sensitive to the boundary conditions applied at the flow base. Under no-slip conditions, the simulated flow arrests more quickly than the experiments. No-stress conditions at the flow base produce plug-like flow that propagates too quickly. Adding an imposed ruptured condition (no solidification and viscosity appropriate to the flow interior) in a thin layer at the flow base produces a lobate morphology that qualitatively resembles observations of natural and experimental flows.

In our models, flows are slowed and stopped by the development of a coherent crust at the flow front, whereas natural flows would continue to propagate via rupture of the skin or crust, highlighting the importance of including these mechanisms in models. However, crust development and rupture are usually omitted from lava flow models, in which propagation and arrest are usually controlled by an increase in viscosity through the entire flow thickness. Our new model allows for investigation into the development and arrest of lava flows that depends on geometry, the competition between flow advance and cooling, and the mechanical properties of a solidified skin or crust. Such insight can be embedded into flow field scale models and allow for physics-based, complex flow fields impacted by breakouts, ooze-outs, channelization, and other critical crust-dominated processes.

How to cite: Birnbaum, J., Lev, E., Spiegelman, M., Kendrick, J., and Lavallée, Y.: Numerical simulation of the effect of solidifying crusts on lava propagation and arrest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16851, https://doi.org/10.5194/egusphere-egu24-16851, 2024.

EGU24-16936 | ECS | Posters on site | GMPV7.1

Towards fully-coupled thermodynamic-thermomechanical two-phase flow models of transcrustal magmatic systems 

Lorenzo G. Candioti, Chetan L. Nathwani, and Cyril Chelle-Michou

The modern view of magmatic systems includes transport and storage of melt at depths within the solid crust. Parameters that control the depths and duration of magma storage include the rheology (especially the depth of the brittle-ductile transition) and chemistry of the melt and solid, the crustal heat budget, and the tectonic setting. Understanding the large spatio-temporal variation in the magmatic output of volcanic arcs, therefore, requires consideration of solid deformation, melt transport, and chemical differentiation in transcrustal magmatic systems.

 

We present preliminary reactive transport models of transcrustal magmatic systems in the ductile limit. The model couples deformation of a compressible solid and Darcy-flow of melt through the solid matrix to phase equilibria calculations. The thermomechanical solver is self-developed in the Julia language and employs a matrix-free pseudo transient solution technique (e.g., Raess et al. 2022). Julia solves the two-language problem and allows for rapid transition from the development stage to massively parallelized production simulations. The thermomechanical two-phase flow equations are numerically discretized on 1D and 2D cartesian finite difference grids. Two different approaches of thermodynamic-thermomechanical coupling are implemented: (i) On-the-fly calculation of stable mineral phases using the Gibbs energy minimization software MAGEMin (Riel et al. 2022) and (ii) interpolation from a precompiled phase diagram.

 

MAGEMin is parallelized and shipped with a Julia wrapper. These features allow near seamless integration of thermodynamic calculations into the newly-developed geodynamic algorithm. The following workflow is applied: (1) Stable mineral phases are calculated at each numerical grid point as a function of local pressure and temperature values using MAGEMin. A starting bulk rock composition characteristic to arc magmas is used for the first time step. (2) The densities as well as the predicted major-oxide fractions of the solid and melt are used in the two-phase flow algorithm to solve for solid deformation, porosity evolution, and major-oxide transport. (3) The local major-oxide fractions predicted by the thermomechanical solver are used as new starting compositions in MAGEMin for the next time step. 

 

For the second approach, we compiled data from published fractional crystallization experiments at relevant pressure and temperature conditions. The data set contains the major-oxide fractions as well as calculated melt and solid densities. During the thermomechanical solution procedure, the data is interpolated from this phase diagram according to local pressure and temperature conditions at each grid point. A detailed comparison of the two approaches and potential implications for natural systems are presented.

 

 

References:

 

 

Räss, L., Utkin, I., Duretz, T., Omlin, S., & Podladchikov, Y. Y. (2022). Assessing the robustness and scalability of the accelerated pseudo-transient method. Geoscientific Model Development, 15(14), 5757-5786.

 

Riel, N., Kaus, B. J., Green, E. C. R., & Berlie, N. (2022). MAGEMin, an efficient Gibbs energy minimizer: application to igneous systems. Geochemistry, Geophysics, Geosystems, 23(7), e2022GC010427.

How to cite: Candioti, L. G., Nathwani, C. L., and Chelle-Michou, C.: Towards fully-coupled thermodynamic-thermomechanical two-phase flow models of transcrustal magmatic systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16936, https://doi.org/10.5194/egusphere-egu24-16936, 2024.

Water-rich high-alumina basalts are widely implicated in models of subduction zone magma genesis and porphyry copper mineralisation, yet their phase relationships at high pressures have been very little studied since the pioneering work of Yoder and Tilley (1963). To fill this gap an experimental study has been carried out on water-saturated phase relationships of a high-alumina basalt (HAB) from St. Kitts, Lesser Antilles volcanic arc (Eastern Caribbean), in the pressure range 1.5 to 20 kbar. Experimentally produced glasses, mineral compositions and mineral assemblages match whole rock data of Lesser Antilles high-alumina basalts and high-alumina basaltic andesites, phenocryst assemblages and mineral chemistry. I show that the liquidus silicate mineral phase changes from olivine and plagioclase at low pressures, through clinopyroxene and amphibole at intermediate pressures, to garnet above 14 kbar. Experimentally produced mineral assemblages correspond well to plutonic xenolith found in Lesser Antilles and change from dunnite, and olivine and hornblende gabbro dominated lithology at pressure ≤ 10 kbar to hornblende pyroxenite, hornblendite and eclogite at pressures ≥ 10kbar.

Melt compositions describe liquid lines of descent that resemble those of many magmatic arc sequences; only alumina shows any strong correlation with pressure. Water saturation (as determined by the difference method) is lower than predicted by most solubility models. The evolved melts generated at low crustal conditions from these experimental series do not resemble silicic melts associated with porphyry copper deposits.

I also address the long-debated origin of high-An plagioclase (An > 90), which occurs in many volcanic and plutonic rocks associated with arc magmatism. Additional experiments on HAB at water-undersaturated and fluid-saturated experiments with 2M CaCl2 solution and CaCO3 have been carried out at 7 kbar to evaluate fluid composition and aH2O on An content of plagioclase. These experiments, combined with existing experiments on broadly basaltic compositions, demonstrate that high-An plagioclase (An ≥ 90) crystallises readily from fluid-saturated high-alumina basaltic melts at pressures of 1 to 10 kbars and temperatures 850 – 1100 ºC. However, the limit of An content produced by experiments is An96. Addition of CaCl2 to the fluid and CaCO3 to the system does not have a significant effect on An content. To produce plagioclase with An content more than 96 mol% a secondary process such as re-melting/re-crystallisation must be involved (Melekhova et al 2022).

Melekhova E., et al. (2022) Journal of Petrology 63.5 (2022): egac033.

How to cite: Melekhova, E.: An experimental study of high-alumina basalt differentiation and the effect of H2O and pressure on plagioclase – melt equilibria , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18369, https://doi.org/10.5194/egusphere-egu24-18369, 2024.

EGU24-408 | Posters on site | GMPV7.2

Tracking Crystal-Melt Segregation and Accumulation in the Intermediate Magma Reservoir 

Jianfeng Ma, Xiaolei Wang, Alexandra Yang Yang, and Taiping Zhao

The genesis of intermediate intrusions is highly controversial, and one of the hot topics is whether they represent frozen melts or cumulates in the evolution of magmatic systems. Distinguishing accumulation from crystallization melt differentiated along the liquid line of descent is the key issue. The Paleoproterozoic intermediate intrusions in southern North China Craton provide an excellent case to decipher this issue. Multiple lines of evidence, including mineral textures, geochemistry as well as alphaMELTS modeling, indicate disequilibrium between whole-rock and minerals, with melt extraction occurring at temperatures of 760°–820°C and with 10–40 wt.% of trapped melts. Effective water storage, revealed by amphibole and clinopyroxene hygrometers, plays a crucial role in promoting crystal-melt segregation in pluton-sized reservoirs in the upper crust. This study demonstrates that the accumulation in intermediate magmas can be identified even without evident complementary initial and extracted melts and provides deep insights into the genesis of intermediate continental crust.

How to cite: Ma, J., Wang, X., Yang, A. Y., and Zhao, T.: Tracking Crystal-Melt Segregation and Accumulation in the Intermediate Magma Reservoir, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-408, https://doi.org/10.5194/egusphere-egu24-408, 2024.

EGU24-460 | ECS | Orals | GMPV7.2

Source peritectic crystal entrainment to mantle magmas produced Earth’s largest chromite deposit 

Tahnee Otto, Gary Stevens, Jean-Francois Moyen, Matthew Mayne, and John Clemens

The mechanisms responsible for the formation of the mineral deposits and complex layered stratigraphy in layered mafic intrusions from cratonic environments have remained elusive, largely because the nature of the mantle melting processes that generated the parental magmas are poorly understood. The largest chromium deposits reside within the mafic-ultramafic Rustenburg Layered Suite (RLS) of the Bushveld Complex, South Africa, as laterally continuous layers of chromitite. The RLS has complex, small-scale chemical stratigraphy (Mg#, An#, Sr(i), etc.) and has surprisingly evolved Sr-isotopic compositions. Due to the low solubility of chromium in the basaltic melts theorised as parental to the suite, several models attempt to explain the chromium enrichment. Perhaps the most plausible hypothesis yet proposed to account for the origin of the RLS chromitites, as well as the associated ferromagnesian silicate layered package, is that the suite was produced from hybrid magmas that formed though the assimilation of Kaapvaal craton rocks by komatiitic magmas. As komatiites arise by high degrees of mantle melting, they carry high concentrations of all strongly compatible elements that are enriched in the mantle, but have very low abundances in crustal rocks. However, average RLS compatible trace-element ratios are not similar to mantle values, with Cr/Ni and V/Ni indicating massive enrichment of chromium and vanadium over nickel. Using phase-equilibrium modelling techniques, this study investigated the possibility that the layering and chromitite formation in the RLS are a consequence of the entrainment of components of the magma source rocks. Results reveal a wedge-shaped domain in pressure-temperature space in the subcratonic mantle in which chromium-bearing orthopyroxene is produced as a peritectic product of incongruent melting of various fertile mantle source compositions. Given the ease of orthopyroxene nucleation and the high rates of plume-driven melt production apparent in the formation of large igneous provinces, entrainment of this orthopyroxene in the melts, on extraction from their mantle sources, seems unavoidable. During ascent, magmas with entrained peritectic orthopyroxene crystallise peritectic olivine and chromite due to reaction of the orthopyroxene with melt – a double-peritectic mechanism. These chromite- and olivine-bearing magmas intrude the upper continental crust as sills of crystal-melt slurry and can produce chromite and dunite layers by density separation immediately after emplacement, even if no further cooling occurs before melt drainage. If metasomatism of the mantle source by crustally-derived fluids (ideally ancient and of low volume) is accepted as plausible, then the very high ratios of chromium and vanadium to other compatible elements for average RLS is a superior fit with the formation of the suite by broadly basaltic melts that entrained peritectic orthopyroxene, rather than formation by reactive assimilation of crust by komatiitic magmas. Thus, this study presents a novel, chemically and thermodynamically constrained model that is a simple, first order, source-dependent alternative to the complex petrogenetic models of the current paradigm.

How to cite: Otto, T., Stevens, G., Moyen, J.-F., Mayne, M., and Clemens, J.: Source peritectic crystal entrainment to mantle magmas produced Earth’s largest chromite deposit, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-460, https://doi.org/10.5194/egusphere-egu24-460, 2024.

EGU24-673 | ECS | Posters on site | GMPV7.2

Geology, petrography and emplacement conditions of the Esenköy Pluton (NW Anatolia) 

Gökçenur Bayram, Esra Tükel, Işıl Nur Güraslan, Alp Ünal, and Şafak Altunkaynak

One of the least studied plutons in NW Anatolia, the Esenköy pluton intruded into the Palaeozoic Armutlu metamorphics. Along its southwestern boundary with the Esenköy pluton, basement rocks are found as "roof pendants". Both the Esenköy pluton and the Armutlu metamorphics are cut by aplite and diorite porphyry dykes. The pluton is mainly granodioritic in composition and is made up of 45-50% plagioclase, 25-30% quartz, 12-15% alkali feldspar, 6-9% hornblende, and 3-5% biotite. It exhibits predominantly holocrystalline porphyritic texture, and graphic-granophyric textures are also widespread throughout the main plutonic body. Diorite porphyry dykes display micro-granular porphyritic texture, while aplite dykes commonly show micro-granular texture.

Chemical analyses of plagioclase and amphibole minerals in granodiorite samples reveal that plagioclases are predominantly andesine (An35-50) in composition. Zoned plagioclases generally show normal zoning with a decrease in calcium ratios from the core to the rims of the crystals. Amphiboles are all calcic in composition and are represented by magnesio-hornblende. Geothermobarometric calculations, using the chemistry of amphiboles and plagioclases from the same samples, yield pressure values ranging from 1.12 to 1.41 kbar and temperature values ranging from 741 to 787 °C. These temperature and pressure conditions suggest that the Esenköy pluton is emplaced at depths of 3.37-4.23 km within the crust. Contact relationships, textural properties and geothermobarometric calculations collectively indicate that the Esenköy pluton is an epizonal pluton that was emplaced into shallow levels of NW Anatolian crust.

How to cite: Bayram, G., Tükel, E., Güraslan, I. N., Ünal, A., and Altunkaynak, Ş.: Geology, petrography and emplacement conditions of the Esenköy Pluton (NW Anatolia), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-673, https://doi.org/10.5194/egusphere-egu24-673, 2024.

EGU24-744 | ECS | Posters on site | GMPV7.2

Gel wax and Ultrasound Transmission Gel as upper and lower crustal rheology analogue 

Uddalak Biswas, Atin Kumar Mitra, and Nibir Mandal

The laboratory modelling of upper and lower crustal rocks has been challenging in terms of rheological scaling for geologists. Upper and lower crusts have been considered as coulomb-brittle or elastic and viscous rheological material, respectively, by the analogue modeller in simulating several deformation related phenomena. However, in nature, they are not purely viscous or elastic, or plastic. Rather, they behave visco-elasto-plastically. This work introduces two new materials of complex visco-elastic and visco-elastoplastic rheology i) Gel wax and, ii) Ultrasound Transmission Gel (USTG). Gel wax is a commercial wax which is composed of mineral oil and hydrocarbon-based polymer. It is used for making transparent, long-lasting candles with melting temperatures of 70-80°C. On the other hand, USTG is a gel-like substance made mainly of Carbopol powder and water.

In this present work, we performed amplitude and frequency sweep tests in a rheometer for both the Gel wax and USTG to understand their complex rheology. The results suggest that Gel wax can be an appropriate analogue material to simulate upper crustal experiments. Similarly, visco-elastoplastic rheology of USTG is analogous to lower crustal rocks.

Considering these materials as crustal analogues, we conducted a few dike emplacement experiments following proper geometric, kinematic and dynamic scaling. The experimental results revealed remarkable 3D dike geometry as both the materials are transparent. Finally, we matched these patterns with a few exposed dikes observed in the field, which supports the applicability of Gel wax and USTG as crustal rock analogues.

How to cite: Biswas, U., Mitra, A. K., and Mandal, N.: Gel wax and Ultrasound Transmission Gel as upper and lower crustal rheology analogue, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-744, https://doi.org/10.5194/egusphere-egu24-744, 2024.

EGU24-2048 | ECS | Orals | GMPV7.2

Accretion of the lowermost oceanic crust at fast-spreading ridges: Insights from the East Pacific Rise (Hess Deep, IODP Leg 345) 

Valentin Basch, Alessio Sanfilippo, Jonathan Snow, Matthew Loocke, and Alberto Zanetti

At mid-ocean ridges, melts formed during adiabatic melting of a heterogeneous mantle migrate upwards and ultimately crystallize the oceanic crust. In this context, the lower crustal gabbros represent the first crystallization products of these melts and the processes involved in the accretion of the lowermost crust drive the chemical evolution of the magmas forming two thirds of Earth’s surface. At fast-spreading ridges, elevated melt supply leads to the formation of a ⁓6 km-thick layered oceanic crust. Here, we provide a detailed petrochemical characterization of the lowermost portion of the fast-spread oceanic crust drilled during IODP Leg 345 at the East Pacific Rise (IODP Site U1415), together with the processes involved in crustal accretion. The recovered gabbroic rocks are primitive in composition and range from olivine-rich troctolites to troctolites, olivine gabbros, olivine gabbronorites and gabbros. Although textural evidence of dissolution-precipitation processes is widespread within this gabbroic section, only the most interstitial phases record chemical compositions driven by melt-mush interaction processes during closure of the magmatic system. Yet, the occurrence of primitive orthopyroxene in most of the olivine-bearing samples indicates that reactive processes allowed for its local saturation within the percolating MORB-type melt. Comparing mineral compositions from this lower crustal section with its slow-spreading counterparts, we propose that the impact of reactive processes on the chemical evolution of the parental melts is dampened in the lowermost gabbros from magmatically productive spreading centres. Oceanic accretion thereby seems driven by in situ crystallization in the lowermost gabbroic layers, followed by upward reactive percolation of melts towards shallower sections. In addition, we here furnish a first estimate of the trace element composition of the parental melts that led to the accretion of the lower crust at Hess Deep, Atlantis Massif and Atlantis Bank; we show that the primary melts of the East Pacific Rise are more depleted in incompatible trace elements compared to those formed at slower spreading rates, as a result of higher melting degrees of the underlying mantle.

How to cite: Basch, V., Sanfilippo, A., Snow, J., Loocke, M., and Zanetti, A.: Accretion of the lowermost oceanic crust at fast-spreading ridges: Insights from the East Pacific Rise (Hess Deep, IODP Leg 345), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2048, https://doi.org/10.5194/egusphere-egu24-2048, 2024.

EGU24-2731 | Orals | GMPV7.2

Plutonic Nature of a Transcrustal Magmatic System: Evidence from Ultrahigh Resolution Sr-Disequilibria in Plagioclase Microantecrysts from the Southern Taupo Volcanic Zone, New Zealand 

Georg Zellmer, Daniel Coulthard Jr, Raimundo Brahm, Charline Lormand, Naoya Sakamoto, Yoshiyuki Iizuka, and Hisayoshi Yurimoto

The residence timescales of antecrystic minerals contribute a key piece of information regarding the petrologic evolution of transcrustal magmatic systems and may be inferred using a combination of observations derived from microanalytical chemistry and diffusion modelling. Here, we present state-of-the-art stacked CMOS-type active pixel sensor (SCAPS) isotopographic images of tephra-hosted plagioclase microantecrysts from Tongariro Volcanic Centre in the southern Taupo Volcanic Zone, New Zealand. These crystals exhibit high-frequency Sr and anorthite zonation at sub-micron spatial resolution. We also find that all crystals display high-frequency intracrystalline Sr chemical potential variations, indicating that they have not resided at magmatic temperature for diffusive relaxation to advance significantly. To quantify crystal residence times at the well-constrained magmatic temperatures of these tephras, we first forward-modeled intracrystalline Sr diffusion over time using numerical methods. Results were then analyzed using novel spatial Fourier-transform techniques developed to understand the systematics the diffusive decay of Sr disequilibria in the spatial frequency domain. This ultimately permitted the estimation of Sr concentration profiles at crystal formation, prior to uptake into the carrier melt at the onset of eruption. Our data imply residence times of days to weeks for the studied microantecrysts. This is inconsistent with long antecryst residence times in magmatic mushes at elevated temperatures, pointing instead to a cool plutonic nature of the magmatic plumbing system beneath the southern Taupo Volcanic Zone.

How to cite: Zellmer, G., Coulthard Jr, D., Brahm, R., Lormand, C., Sakamoto, N., Iizuka, Y., and Yurimoto, H.: Plutonic Nature of a Transcrustal Magmatic System: Evidence from Ultrahigh Resolution Sr-Disequilibria in Plagioclase Microantecrysts from the Southern Taupo Volcanic Zone, New Zealand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2731, https://doi.org/10.5194/egusphere-egu24-2731, 2024.

Understanding the processes involved in the transformation of juvenile basaltic oceanic arc crust into mature continental crust remains a key challenge in Earth sciences. In this contribution, we present a comprehensive synthesis of in situ zircon U-Pb age and Hf-O isotope data for Paleozoic intrusions within the West Junggar oceanic arc, NW China. Our study reveals four distinct pulses of magmatic activity: Early Cambrian to Early Ordovician (515 to 486 Ma); Late Ordovician to Middle Devonian (445 to 392 Ma); Early Carboniferous (343 to 310 Ma) and Late Carboniferous to Middle Permian (309 to 259 Ma). These pulses have varied spatial and temporal distributions. All magmatic rocks display consistently high zircon Hf and whole-rock Nd isotope values, but substantial variations in zircon O isotopes. There are two groups of intrusions: those with high zircon δ18O (>6.5‰) and those with mantle-like zircon δ18O (ca. 5.5‰). The high zircon δ18O intrusions are predominantly concentrated in the southern West Junggar and their Hf and Nd isotopes indicate the involvement of supracrustal material and juvenile basaltic crust in their petrogenesis. Binary mixing calculations indicate a contribution from the supracrustal rocks ranging from 10% to 50%. The intrusions with mantle-like zircon δ18O are found primarily in northern West Junggar with a small amount occurring in southern West Junggar. The intrusions record a variety of magma sources and processes as demonstrated by Hf-O isotope and geochemical data. These data indicate partial melting of metasomatized depleted mantle, mixing of depleted mantle and juvenile crust, and partial melting of trapped juvenile oceanic crust or mafic lower crust. Hf model ages reveal significant crustal growth in the West Junggar, characterized by three distinct episodes of crust formation occurring at approximately 656-684 Ma, 524-536 Ma, and 441-471 Ma, involving periodic remelting of igneous material derived from a depleted mantle source. This newly-formed crust maintains a mantle-like oxygen isotope composition despite being repeatedly sampled by magmas for up to 0.26 Ga. Since the timing of crustal growth occurred independently of the major magmatic pulses, the latter reflect primarily reworking and remelting processes. Two significant episodes of magmatic activity, the late Silurian to early Devonian and the late Carboniferous to early Permian, preserve a signature of ocean ridge subduction. High-temperature magmatism during these periods promoted extensive melting of the mafic lower crust, oceanic crust, and supracrustal rocks, leading to the compositional transformation from basaltic to felsic continental crust. This comprehensive compilation provides valuable insights into granite petrogenesis, crustal evolution, and the diverse processes involved in the maturation of oceanic arc crust and its contribution to continental crust formation and evolution.

 

How to cite: Yin, J., Wang, T., and Huang, H.: Ocean arc to continental crust: zircon Hf-O isotopes and crustal evolution of West Junggar, NW China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2959, https://doi.org/10.5194/egusphere-egu24-2959, 2024.

Ferro-basaltic liquids intersect a binode during fractionation, splitting into two immiscible silicate liquids, one Si-rich and the other Fe-rich. The two liquids have very different physical properties: the Si-rich liquid is more buoyant and viscous, preferentially wetting plagioclase, whereas the Fe-rich liquid preferentially wets grains of mafic minerals and Fe-Ti oxides. The density difference means that when a crystal-poor magma body intersects the binode, it is likely to undergo compositional stratification, with implications for the compositions of any eruptions. When the interstitial liquid in a crystal mush unmixes, the density difference is compounded by the differences in wetting properties, leading to complex behaviour if capillary forces act in a different direction to that of gravity. The extent and scale of differential migration of unmixed liquids may thus play an important role in the genesis of the Daly Gap, while the preferential partitioning of P, PGE and REE into the Fe-rich conjugate has significant implications for formation of economically important deposits.

The Skaergaard Intrusion of East Greenland records abundant evidence for differential migration of immiscible silicate liquid conjugates. At the intrusion scale, the roof rocks are more silica-rich than the cumulates at the floor, consistent with intersection of the binode by the bulk magma leading to the accumulation of the buoyant Si-rich conjugate in the roof mush. This is supported by the localised presence of reverse modal layering on the floor, interpreted as bodies of dense Fe-rich liquid ponded at the top of thin (<1m) mush. Large-scale lateral migration of Fe-rich liquid along fractures developing in the solidifying wall mush may have been the underlying cause of metasomatism to form localised 100m-scale patches of replacive pyroxenite. Evidence of metre-scale differential migration within the crystal mush on the intrusion floor is provided by paired silicic and mafic late-stage segregations, recording downwards penetration and disruption of the floor mush by dense Fe-rich liquid, coupled with limited upwards flow of viscous Si-rich liquid. Further evidence of metre-scale differential migration is provided by compositional rims developed on the tops and bases of (almost) fully-solidified blocks in the floor cumulates of material solidified at the roof, fragmented and released during contemporaneous seismic activity. The mafic rims at their tops formed by the ponding of downwards-moving Fe-rich liquid while the felsic rims at their bases formed by the ponding of upwards-moving Si-rich liquid against the impermeable autoliths, consistent with the extent of rim development being a function of autolith shape, rather than composition. Differential migration on the cm-scale, driven by capillarity and the differences in wetting properties of the two immiscible conjugates, is suggested as the mechanism by which poorly-defined cm-scale micro-rhythmic layering is superimposed on graded modal layering.

The Skaergaard examples of differential migration provide the opportunity to constrain the length- and time-scales of differential migration of unmixed immiscible silicate conjugates, to quantify the effects of capillarity and emulsion coarsening, and to assess the more general importance of liquid immiscibility on petrogenetic evolution.

How to cite: Holness, M., Nielsen, T., and Namur, O.: Differential migration of immiscible liquids in gabbroic crystal mush: the Skaergaard Intrusion, East Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3983, https://doi.org/10.5194/egusphere-egu24-3983, 2024.

EGU24-4426 | Posters on site | GMPV7.2

A mantle source for water in Appinite complexes: implications for genesis of granitoid batholiths and crustal growth 

J. Brendan Murphy, Christopher J. Spencer, Donnelly B. Archibald, and William J. Collins

Appinite plutonic rocks range from ultramafic to felsic in composition, are characterized by idiomorphic hornblende as the dominant mafic mineral in all lithologies, and by spectacularly diverse textures, including planar and linear magmatic fabrics, multiple comb layers, mafic pegmatites and widespread evidence of mingling between mafic and felsic compositions. These features suggest that they are anomalously water-rich mafic magmas.  

The ca. 607 Ma Greendale Complex in the Antigonish Highlands of Nova Scotia is typical of appinite complexes which commonly occur as small (~2 km diameter) plutons adjacent to major deep crustal faults along the periphery of voluminous granitoid plutons emplaced in the waning stages of regional arc activity. Isotopic data from hornblendes in the Greendale Complex yield δD values ranging from -61 to -72 and δO18 from 3.7 to 7.0, indicating the water in the appinite magma has a strong mantle component. These data suggest the appinites may represent aliquots of hydrous basaltic magma derived from mafic underplates originally emplaced along the base of the crust during protracted subduction. Transfer of heat and fluids to the base of the crust triggered generation of coeval (615-604 Ma) granitoid magmas by partial melting in the overlying MASH zone. The granitoid magmas were emplaced in the shallow crust when transient stresses activated favourably-oriented structures which became conduits for magma transport. The ascent of late mafic magmas within the Antigonish Highlands was impeded by the rheological barriers created by the structurally overlying granitoid magma bodies. Magmas that form the Greendale Complex evaded those rheological barriers because they preferentially exploited the deep crustal Hollow Fault that bounded the plutonic system.

Collectively, these mineralogical, textural and geochemical features suggest a complex magmatic history involving repeated water saturation episodes within the plumbing system as mafic, mantle-derived magmas ascended and differentiated at mid-to-upper crustal levels (ca. 3-5 kbar). More generally, the most mafic components of appinite complexes may provide a window into the composition of the mafic underplate and insights into processes that generate granitoid batholiths and crustal growth in arc systems.

 

How to cite: Murphy, J. B., Spencer, C. J., Archibald, D. B., and Collins, W. J.: A mantle source for water in Appinite complexes: implications for genesis of granitoid batholiths and crustal growth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4426, https://doi.org/10.5194/egusphere-egu24-4426, 2024.

EGU24-5671 | ECS | Posters on site | GMPV7.2

Geochemistry and geochronology of Midyan terrane granitoids, NW Saudi Arabia: Implications for growth of the Arabian-Nubian Shield 

Wafa AL-Hakimi, Sabyasachi Chattopadhyay, Faris Sulistyohariyanto, Scott A. Whattam, Hossein Azizi, Keewook Yi, and Fatemeh Nouri

 The 900–550 Ma Arabian-Nubian Shield (ANS) represents the northern part of the East African Orogen (EAO) and was generated by Neoproterozoic juvenile crust addition and ultimately, collision of eastern and western Gondwana ca. 600 Ma. The ANS  encompasses the greatest volume of Neoproterozoic juvenile crust preserved on Earth and embodies over 610,000 km2 across NE Africa and the western part of the Arabian Peninsula. The ANS comprises stacks of thin-skinned nappes resulting from oblique convergence of bounding plates and resulting amalgamation of intra-oceanic arcs generated within the Mozambique Ocean. As such, the ANS is a classic example of an accretionary orogen. Final accretion and ANS consolidation were accompanied and followed by emplacement of within-plate alkaline plutons c. 640–550 Ma, which represent the largest volume of alkaline granitoids on the planet. Overall, ANS tectonic evolution encompasses an orogenic cycle beginning with the fragmentation of Rodinia (870–800 Ma) and ending with amalgamation of eastern and western Gondwana in the Cambrian.

This study combines field observations, petrography, whole rock major-and-trace element chemistry, along with U-Pb zircon geochronology and Sr-Nd-Pb isotope data of four granitoid suites of the northwestern part of the Midyan terrane (Ifal, Muwylih, Midyan, and Lawaz), that provides an excellent opportunity for further understanding of the factors influencing the shift from A- to I-type granitoids. Samples are mostly granite-granodiorite-diorite with subordinate gabbro and gabbro diorite. Seven samples are A-type, while the remaining 26 are I-type. Petrographically, I-type rocks consist of K-feldspar, quartz, albite, mica, amphiboles, and sodic-pyroxene as major minerals with a variety of accessory minerals, including Fe-oxides and zircon. Major oxide abundances such as CaO, TiO2, and P2O5 manifest a clear decrease with increasing SiO2 content, except for K2O, which indicates fractionation of, for example, plagioclase, Fe-Ti oxides, and apatite. Whole rock data shows clearly distinct characters of the A-type being metaluminous, enrchied in ∑REE with an average of 355 µg/g. In contrast, the I-type is meta-luminous-peraluminous, which only has an average of ∑REE 197 µg/g. The chondrite-normalized patterns of the A-type show lower negative Eu anomalies (Eu/Eu*=0.61) in comparison to the I-types (Eu/Eu*=0.86), depicting the different degrees of plagioclase fractionation. The primitive-mantle normalized patterns show depletions in  Sr and Ti, indicating fractionation of feldspar and Fe-Ti phases in both types. The U-Pb zircon ages indicate two distinct pulses of granitoid magmatism.  The first pulse is attributed to A2 (post collision)-type ca. 634–640 Ma, followed by a second pulse of I-type in nature ca. 618–598 Ma. The A and I-type Sr-Nd isotope data attest to the juvenile nature of the crust from the ANS (εNd =4.88–5.15), while some I-types (εNd =3.91) are derived from partial melting of a pre-existing crust. We conclude that the magmatism in the Midyan terrane area is shown to have shifted from a within-plate setting associated with orogenic collapse and partial melting of the lower crust into volcanic arc affinity with a more depleted source.

 

How to cite: AL-Hakimi, W., Chattopadhyay, S., Sulistyohariyanto, F., Whattam, S. A., Azizi, H., Yi, K., and Nouri, F.: Geochemistry and geochronology of Midyan terrane granitoids, NW Saudi Arabia: Implications for growth of the Arabian-Nubian Shield, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5671, https://doi.org/10.5194/egusphere-egu24-5671, 2024.

EGU24-5812 | Orals | GMPV7.2 | Highlight

Visualising magma plumbing systems in 4D 

Craig Magee

Significant advances have been made in using a wide variety of geophysical techniques to track melt migration, image the structure of active and ancient magma plumbing systems, and constrain emplacement mechanics. In particular, integrating traditional petrological and geochemical results with such geophysical data and modelling has afforded exciting insights into the development of entire magmatic systems. However, divisions between the scales and physical settings over which these methods are applied remain. To characterise these differences and promote the benefits of further combining geophysical, petrological, and geochemical datasets, I discuss how geophysical techniques can be utilised to provide structural context and place physical constraint to the chemical evolution of magma plumbing systems. I am no expert in many geophysical techniques and thus lean on the work of many others, showcasing the importance of collaboration to pushing the boundaries of our science. Here, I will examine on what we can do with some geophysical and geodetic techniques, whilst importantly highlighting what we cannot do with them, and discuss how their application can help us solve some of the key questions within our field. Overall, I hope to show that approaching problems concerning magma plumbing systems from an integrated petrological, geochemical, and geophysical perspective, brought together with various modelling methods, will yield important scientific advances and provide exciting future opportunities for the entire volcanological community.

How to cite: Magee, C.: Visualising magma plumbing systems in 4D, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5812, https://doi.org/10.5194/egusphere-egu24-5812, 2024.

EGU24-5981 | Orals | GMPV7.2

The 3D anatomy of magma transport in fast-spreading oceanic crust of the Oman ophiolite 

Antony Morris, Andrew Parsons, Michelle Harris, Chris MacLeod, Benoit Ildefonse, Charlotte Atton, Simon Allerton, and Derya Gürer

At fast-spreading oceanic ridges such as the East Pacific Rise, divergence between tectonic plates is accommodated almost exclusively by magmatic accretion. A robust understanding of magmatic accretion during seafloor spreading is therefore necessary to model the structure and composition of oceanic lithosphere and exchanges in heat and mass at a global scale over geological time. Whereas most models consider magmatic accretion in 2D, variations in ridge axial morphology and magmatic compositions highlight the occurrence of ridge-parallel variations in magmatic processes along fast-spreading systems. This suggests that magmatic accretion may be a 3D process involving significant ridge-parallel magma transport.

To constrain the process of magmatic accretion at fast-spreading ridges, we present our on-going investigation of magma transport in the Oman ophiolite. The first order structure and composition of the ophiolite, defined by a sheeted dyke complex with an underlying axial melt lens of variable thickness on top of foliated gabbro, is analogous to the East Pacific Rise. This provides a unique opportunity to investigate magmatic accretion processes above and below an axial melt lens system in three dimensions at ridge segment- to grain-scales for the first time.

We present new data constrains the directions of magma transport in the crust of the Oman ophiolite. This includes analyses of foliated gabbros and sheeted dyke complexes from the Fizh, Salahi, and Sarami blocks, which define a complete ridge segment. Using anisotropy of magnetic susceptibility (AMS), we report the orientations of magnetic fabrics that serve as proxies for magmatic flow directions. Combining AMS data with paleomagnetic analyses of magnetic remanence directions allows us to restore magmatic flow directions to their paleo-ridge orientation, prior to obduction. Our results indicate that magmatic flow directions vary along the length of the ridge segment and cannot be explained by simple 2D models. Our data show that ridge-parallel lateral flow is a common phenomenon in both the sheeted dykes and foliated gabbros over the length of a ridge segment. Our results also have important implications for competing models of crustal accretion.

How to cite: Morris, A., Parsons, A., Harris, M., MacLeod, C., Ildefonse, B., Atton, C., Allerton, S., and Gürer, D.: The 3D anatomy of magma transport in fast-spreading oceanic crust of the Oman ophiolite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5981, https://doi.org/10.5194/egusphere-egu24-5981, 2024.

EGU24-6145 | ECS | Orals | GMPV7.2

Geodetic observations of simultaneous rift-scale magma inflow in multiple sills in the Central Afar rift 

Alessandro La Rosa, Carolina Pagli, Hua Wang, Freysteinn Sigmundsson, Virginie Pinel, and Derek Keir

During plate spreading, large volumes of magma can be extracted from the upper mantle and intrude the crust. Geophysical and geochemical studies at active magmatic rifts and passive margins show that crustal intrusions mainly occur in the form of transient sill-like bodies. The sills pond at various crustal levels, potentially feeding shallower plumbing systems, dike intrusions and surface eruptions. Trans-crustal magma migration and intrusion thus have a key role in controlling extension, strain localization and subsidence during rifting. However, a clear understanding of the mechanisms of sill intrusion, their connection to upper mantle processes, as well as the spatial and temporal response of the sills to a new arrival of magma is still limited by the paucity of direct observations. In this study, we provide one of the few direct InSAR observation of rift-scale deformation caused by magma inflow from the upper mantle to multiple crustal sills in the Central Afar (CA) rift.

We used InSAR time-series from 255 ESA Sentinel-1 interferograms during 2014-2021 and combined them with available GNSS measurement to retrieve the 3D velocity field and the temporal evolution of surface deformation in CA. We observed four uplift patterns with rates of ~5 mm/yr, that we inverted using four inflating Okada tensile dislocation sources (sills). Our best-fit model shows four sills elongated in a NW-SE direction, similar to the rift trend, and opening rates ranging between 16 and 44 mm/yr. The sills are located at various crustal depths but mainly in the mid-to-lower crust, following the thinning of the crust imaged seismically in CA. Cross-correlation of time-series also show that the uplift above the four sills starts simultaneously in December 2016 and continue until March 2021.

We interpreted the simultaneous inflation of four distant sills as the result of a shared pressurization event caused by an episodic magma inflow from a common source in the upper mantle. Our results show that magma supply from the mantle beneath continental rifts is episodic, and occurs across large spatial scales but short temporal scales over which deep crustal magma ponding takes place. Such process could explain how the thick intruded crust common at magma-rich rifted margins is created and could help in understanding the long-term dynamics of rifting episodes and volcanism.

How to cite: La Rosa, A., Pagli, C., Wang, H., Sigmundsson, F., Pinel, V., and Keir, D.: Geodetic observations of simultaneous rift-scale magma inflow in multiple sills in the Central Afar rift, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6145, https://doi.org/10.5194/egusphere-egu24-6145, 2024.

EGU24-6844 | ECS | Posters on site | GMPV7.2

Quaternary Magmatism in NW Svalbard: Refining the Architecture and Evolution of Sverrefjellet Volcano 

Dmitrii Zastrozhnov, Sverre Planke, John Millett, Rafael Horota, Agnes Kontny, Kim Senger, Sebastian Tappe, Anniken Helland-Hansen, Maria Telmon, Peter Betlem, Alexander Minakov, and Horst Kaempf

Sverrefjellet is the remnant of an extinct alkali basaltic stratovolcano located in NW Svalbard, representing a distinctive phase of Quaternary magmatism in the High Arctic. It is part of the Bockfjorden Volcanic Complex, which consists of several eruption centers within the Woodfjorden-Bockfjorden area. The volcanism occurred during the northern hemisphere’s glaciations and reveals evidence for magma interactions with glaciers. The Quaternary eruption centers are localized along the Breibogen Fault and were probably linked to the evolution of the Knipovich mid-oceanic ridge, yet the exact age of the magmatic activity remains uncertain. Sverrefjellet is renowned for its high abundance of mantle-derived xenoliths, which have become a focal point in most publications on this volcano to date. However, the magmatic architecture and physical volcanology of Sverrefjellet have received only limited attention after the initial mapping by Skjelkvåle et al. (1989).

In July 2023, an international multi-disciplinary geoscientific expedition to Woodfjorden-Bockfjorden was undertaken. One of the primary objectives was to perform detailed mapping and systematic sampling of volcanic-related units within Sverrefjellet volcano, with the aim of exploring and refining magma emplacement processes. To facilitate this, drones were utilized to acquire high-resolution 3D digital textured models over the best-exposed outcrops of the volcano. The in-field sampling of the main volcanic units was accompanied by extensive (∼100) magnetic susceptibility measurements with a hand-held Kappameter (SM-30). In total, 20 rock samples have been prepared for petrographic, SEM and EPMA analyses.

We observed the presence of mantle-derived xenoliths in all volcanic units, which include dyke intrusions, pillow basalts with associated lava tubes, basaltic lava flows, and various volcanogenic sediments. The slopes of the extinct volcano display predominant frost weathering, with the southern slope adorned with olivine sand and gravel sourced from 'bomb-shaped' nodules or clasts that typically contain peridotite xenoliths as their cores. The presence of pillow lavas and associated 1 to 2 meter large lava tubes suggests subglacial magma emplacement. This is supported by their relatively high elevation at 200-300 meters above sea-level, which makes interaction with seawater highly unlikely.

In between lava flows and dykes, texturally distinctive zones characterized by platy tops and bottoms as well as numerous flattened boulder-sized xenolithic nodules were observed. Petrographic and SEM analyses of xenoliths and host basalts revealed no preferred alignment of crystals within the platy zones, suggesting that these schistose textures developed due to rapid magma cooling and subsequent freeze-thaw action rather than tectonic shearing. The basalts display typical ferrimagnetic susceptibilities (average: 3.24 × 10-3 SI), whereas the volcanogenic sediments exhibit low paramagnetic susceptibility (0.38 × 10-3 SI), indicating rapid magma quenching during fragmentation, which is characteristic of subglacial emplacement.

Our preliminary results support a subglacial origin for the Sverrefjellet eruptions. Ongoing detailed mapping and thorough magnetic mineralogy analyses, coupled with geochronological and geomorphological studies, will enhance our understanding of subglacial volcanic processes at the extinct Sverrefjellet volcano and more broadly. Additionally, these findings will contribute to a better understanding of the nature and origin of High Arctic Quaternary magmatism and its paleogeographic setting.

How to cite: Zastrozhnov, D., Planke, S., Millett, J., Horota, R., Kontny, A., Senger, K., Tappe, S., Helland-Hansen, A., Telmon, M., Betlem, P., Minakov, A., and Kaempf, H.: Quaternary Magmatism in NW Svalbard: Refining the Architecture and Evolution of Sverrefjellet Volcano, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6844, https://doi.org/10.5194/egusphere-egu24-6844, 2024.

EGU24-7511 | Orals | GMPV7.2

Imaging the magma plumbing system of Ciomadul volcano and the Perşani Volcanic Field and constraining postcollisional magma dynamics  

Matthew J. Comeau, Graham J. Hill, Svetlana Kovacikova, Jochen Kamm, Réka Lukács, Ioan Seghedi, Alexander Grayver, István Bondár, and Harangi Szabolcs

There are indications that some long-dormant or seemingly inactive volcanoes may have potentially active magma storage systems. One such system is Ciomadul volcano, which is located at the south-eastern terminus of the Carpathian volcanic chain (Romania). With the last eruption occurring at ~30 ka, this is the youngest volcano in eastern-central Europe. Understanding the nature and structure of the magma plumbing system is crucial to elucidating the evolution of the volcano and to assessing its hazard potential. This includes the depth, size, and geometry of the magma storage region, the amount and composition of the melt present, and the link between mantle and crustal processes.  

Ciomadul is situated in a geodynamically active region about 50 km from the Vrancea zone, where deep earthquakes are frequent. These earthquakes may represent the descent of a dense lithospheric slab beneath a continental collision zone and this may imply an asthenospheric upwelling due to return flow of mantle material. To the north-west of Ciomadul lies a chain of older volcanic complexes, the Călimani–Gurghiu-Harghita volcanic complex; about 40 km west of Ciomadul towards the Transylvanian Basin, a monogenetic basaltic volcanic region was developed at 1.2–0.5 Ma (Perşani volcanic field). Seismic tomography has revealed low-velocity columns through the lithosphere beneath both Ciomadul and Perşani. However, high-resolution images of the complex geometry of the system are lacking.  

We report here on a 3-D electrical resistivity model of the region that was generated from 41 magnetotelluric measurements acquired in 2022 that form a 75 km by 75 km array. The data typically had reliable periods from 128 Hz to 4,100+ s. Choosing appropriate locations for measurement was critical, away from sources of cultural electromagnetic noise that can contaminate the signals, as was careful data processing, including applying data pre-selection schemes and manual time windows in addition to standard approaches using robust statistics.  

Phase tensor analysis suggests that the data are 3-D at all scales. The 3-D electrical resistivity model reveals conductive anomalies (<10 ohm-m) in the subvolcanic crust. These are interpreted as melt-bearing magma reservoirs distributed in the mid-lower crust (depths of ~10–25 km) and a quasi-vertical conduit extending to the near surface. The crustal reservoir is oriented north-south, has its western margin beneath the surface vent of Ciomadul, and extends ~20 km eastward. These results are consistent with the quantitative petrological models placing the upper melt-bearing silicic crystal mush reservoir at a depth of 5–20 km beneath Ciomadul, and a magma-generation area in the asthenosphere (85–105 km depth). In contrast, no strong conductive anomaly is observed in the crust below Perşani, which fits the magma evolution model, i.e. small batches of mantle-derived magmas ascend rapidly through the crustal column. Our results suggest that Ciomadul, a seemingly inactive volcano, is still underlain by a melt-bearing magma body and therefore can be regarded as having potential for reactivation and further volcanic eruptions.  

How to cite: Comeau, M. J., Hill, G. J., Kovacikova, S., Kamm, J., Lukács, R., Seghedi, I., Grayver, A., Bondár, I., and Szabolcs, H.: Imaging the magma plumbing system of Ciomadul volcano and the Perşani Volcanic Field and constraining postcollisional magma dynamics , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7511, https://doi.org/10.5194/egusphere-egu24-7511, 2024.

EGU24-7717 | ECS | Orals | GMPV7.2

Plumbing system architecture, magma differentiation, and volatile element evolution in an active rift segment: Constraints from melt inclusions in Asal rift (Djibouti, Afar). 

Juliette Pin, Lydéric France, Gilles Chazot, Etienne Deloule, Yafet Gabrewold Birhane, Raphaël Pik, and Irene Schimmelpfennig

The Asal Rift, situated within the Afar region, presents a unique opportunity to study continental rifting and ongoing break-up mechanisms. Here we present a comprehensive study based on volatile element contents of magmas within the Asal rift's segment. Samples were gathered from various volcanic sub-segments within the active part of the Asal rift, and a subset was collected to document the successive steps of the recent 1978 Ardoukoba eruption. Altogether our new sampling is offering a chronological framework crucial to understanding this magmatic system and the eruptive sequences. Quenched pyroclastic deposits (scoria) were used as they are more likely to preserve the magma's volatile content without significant degassing upon cooling at surface than lava flows. By analyzing over 400 melt inclusions within plagioclase and olivine crystals of 15 new samples, we provide insight into the pre-eruptive volatile content of Asal magmas. The melt inclusions volatile contents (H2O, CO2, Cl, and S) were quantified through SIMS analyses at CRPG. Sample preparation for SIMS measurements was carefully achieved to avoid any contamination or volatile loss. After estimation of the volatile migration through the shrinkage bubbles of the melt inclusions by Raman spectroscopy, and correction from post-entrapment crystallization processes, we reconstructed the initial magmatic volatile content at the reservoir depth. This content, combined with detailed petrographic study, field observations, and new dating, allows us to propose a comprehensive picture of the Asal Rift plumbing system architecture, and to discuss its spatial variability and temporal evolution. The wealth of data allowed us to highlight a relative homogeneity of the reservoir volatile contents over the recent Asal rift segment erupted magmas, and to discern the depth range of the Asal igneous reservoir that spans from approximately 5 km to 25 km (based on solubility models of VESIcal (1)). Furthermore, volatile data, combined with in-situ major and trace element analysis, provides insights into magma differentiation, degassing, and into the volatile content of the mantle source. We investigate 3 potential steps of degassing and their effect on volatile, trace and major element: within the plumbing system (during the differentiation), during magma ascent, and at the surface during the eruption (unlikely given the sampling method). Finally, our study focused on the 1978 Ardoukoba eruption within the Asal rift. With a sampling of the entire eruptive sequence, we were able to highlight the evolution of the volatile content during this eruption, showing that the initial differentiated magma reservoir underwent a recharge event before eruption. In conclusion, this new in-situ high-resolution volatile, trace and major element extended dataset 1/ delineated the extensive depth range of the magmatic reservoir, 2/ allows a better understanding of the dynamics of magma reservoirs that feed continental rift systems, and 3/ provides new constraints on the magma evolution, differentiation, and degassing at depth within such a system.

(1) Iacovino, K., Matthews, S., Wieser, P. E., Moore, G. M., & Bégué, F. (2021). VESIcal Part I: An Open‐Source Thermodynamic Model Engine for Mixed Volatile (H2O‐CO2) Solubility in Silicate Melts. Earth and Space Science, 8(11).

How to cite: Pin, J., France, L., Chazot, G., Deloule, E., Gabrewold Birhane, Y., Pik, R., and Schimmelpfennig, I.: Plumbing system architecture, magma differentiation, and volatile element evolution in an active rift segment: Constraints from melt inclusions in Asal rift (Djibouti, Afar)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7717, https://doi.org/10.5194/egusphere-egu24-7717, 2024.

EGU24-7781 | ECS | Orals | GMPV7.2

What modulates eruptive styles and timescales at Villarrica and Osorno volcanoes (Chile)? 

Sri Budhi Utami, Jacqueline Vander Auwera, Tonin Bechon, Paul Fugmann, and Olivier Namur

Villarrica and Osorno are two active stratovolcanoes in the Central Southern Volcanic Zone (CSVZ) of the Chilean Andes that share several geochemical characteristics: near-primary, tholeiitic parent magmas (50-53 wt. % SiO2), overlapping major/trace element differentiation trends, and comparable storage conditions [1-4]. Yet, their current or recent eruptive styles diverge significantly. Villarrica is a steady-state, open-vent volcano with a lava lake that produced ~100 moderate-intensity, Strombolian eruptions since 1579; Osorno is a closed-vent volcano with 10x less eruptions for the same period. Our initial hypothesis proposed that differences in eruptive style and frequency could be due to a relatively higher degree of crustal permeability under Villarrica than Osorno [5]. Although preliminary data shows that some differences exist in olivine chemistry and textures between Villarrica (Fo72-87) and Osorno (Fo66-82) [4,5,6], both volcanoes have broadly similar compositional ranges and multimodal distributions, with comparable diffusion timescales. This suggests the degree of crustal permeability underneath both volcanoes are likely comparable, prompting us to consider other parameters, such as magma supply rate. In this contribution, we discuss and evaluate the role of magma supply rate and other parameters in modulating eruptive styles at Osorno and Villarrica, based on an updated dataset of magma storage conditions, diffusion timescales, and inferences drawn from published literature. We aim to further current understanding of subduction zone magmatism and geodynamics, with implications on volcanic hazard reduction.

1. Vergara et al. (2004). J. S. Am. Earth Sci. 17: 227-238. 2. Morgado et al. (2015). JVGR, 306: 1-16. 3. Pizarro et al. (2019). JVGR. 384: 48-63. 4. Bechon et al. (2022). Lithos. 106777. 5. Utami et al. (2023) Goldschmidt 2023 Abstract 6. Romero et al. (2022). Bull. Volc. 85 (2).

How to cite: Utami, S. B., Vander Auwera, J., Bechon, T., Fugmann, P., and Namur, O.: What modulates eruptive styles and timescales at Villarrica and Osorno volcanoes (Chile)?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7781, https://doi.org/10.5194/egusphere-egu24-7781, 2024.

EGU24-9055 | ECS | Posters on site | GMPV7.2

Continuous Subsidence of Dallol Volcano (Danakil Depression) as a result of magmatic and hydrothermal interaction: Insights from InSAR Observation 

Birhan Kebede, Carolina Pagli, Derek Keir, Alessandro La Rosa, and Freysteinn Sigmundsson

Axial rift volcanoes characterised by an active magmatic and hydrothermal system offer a unique opportunity to study the interaction between these processes. The Dallol volcanic and hydrothermal area is situated in the Afar rift, on the axis of Erta Ale ridge, in a depressed salt plain. Dallol has been experiencing deformation at least since the first dike intrusion observed by InSAR in 2004. Here, we present the results of a new InSAR analysis of Dallol between 2014 and 2023, and inverse modelling of the observed deformation. We used SAR data from the ESA´s Sentinel 1A/B ascending (014) and descending (079) orbits to produce over 651 interferograms. Then we obtained InSAR average velocity maps revealing the presence of three closely spaced and concentric deformation signals of a range increase, consistent with subsidence, of up to 40 mm/yr in the satellite Line-of-Sight (LOS). The main deformation signal corresponds to the Dallol crater, while the two smaller maxima occur on the bishophite precipitating Black Mountain area south of Dallol and at the location of a circular pool at the edge of the salt plain, west of the crater. Our modelling results indicate that the deformation sources can be explained by contractions of three Okada tensile dislocation sources situated at different shallow depths, ranging between 0.7-1.7 km, with a length of 1-3 km and volume decrease of 1-3x10-4 km3/yr. Time series analysis also shows that the subsidence pattern was about linear while small seasonal fluctuation patterns are identified at the two smaller maximas. We interpret that the main subsidance at the Dallol crater is likely caused by the depressurisation of shallow sills, while a possible contribution to the defomration from the hydrothermal system due to seasonal flooding is envisaged for the other two maximas.

How to cite: Kebede, B., Pagli, C., Keir, D., La Rosa, A., and Sigmundsson, F.: Continuous Subsidence of Dallol Volcano (Danakil Depression) as a result of magmatic and hydrothermal interaction: Insights from InSAR Observation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9055, https://doi.org/10.5194/egusphere-egu24-9055, 2024.

To understand the style, longevity and hazards of volcanic fissure eruptions, we need to understand the magma flow dynamics governing their feeder dykes. Microstructural analysis through optical microscopy and electron backscatter diffraction (EBSD) can be used to observe crystal alignment, shape and size from dyke samples to investigate magmatic fluid flow and deformation processes during the ascent of magma. Plagioclase is a mineral ubiquitously found in volcanic rocks that forms throughout magma crystallisation at a wide range of temperatures (~1300-400°C), and is therefore a mineral commonly used to investigate magma flow dynamics in dykes and sills. In particular, microlites of plagioclase (<0.1 mm) are amongst the last crystals to form at shallow crustal depths so have the potential to record the near surface flow behaviour and deformation processes that can lead to eruption.

Here we examine elongate plagioclase microlites from oriented samples of a basaltic dyke from the Budj Bim Volcanic Complex, the only known fissure-fed eruption in the Newer Volcanics Province, south east Australia. Extensive quarrying of the Little Mount scoria cone has provided excellent exposure of the internal architecture of its feeder dyke. Optical microscopy observations show the dyke is comprised of zoned olivine phenocrysts (20%, <0.5 mm diameter), pyroxenes (20%, <0.1 mm diameter) and a fine-grained plagioclase-rich groundmass with minor oxides (5%, <0.05 mm diameter). EBSD of the plagioclase microlites shows they share a strong shape preferred orientation (SPO) and crystallographic preferred orientation (CPO). Plagioclase microlite orientation can be used as an indicator of magma flow, as elongate crystals may reorient due to flow and/or pure shear within the ascending magma. Using these novel data, we propose a model for plagioclase orientation, and therefore potential magma flow dynamics in the Little Mount dyke. Understanding the physical and chemical processes governing historic fissure eruptions such as the Budj Bim Volcanic Complex enables us to inform hazard mitigations for future fissure eruptions worldwide. 

How to cite: Hrintchuk, J. A., Kavanagh, J. L., and Mariani, E.: Plagioclase preferred orientation provides insights into magma flow dynamics of a basaltic dyke from the Budj Bim Volcanic Complex, Australia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9775, https://doi.org/10.5194/egusphere-egu24-9775, 2024.

EGU24-10207 | Orals | GMPV7.2

Transcrustal, interconnected, or isolated magma reservoirs, can we tell the difference? 

Fidel Costa and Jean-Philippe Metaxian

The organization of melts below active volcanoes plays a large role on the size, composition, and character of the ensuing eruptions. In principle it should be possible to determine the distribution of melts with geophysical data, such as inversion of seismic velocity, density, and gravity. In practice, it appears that the size and distribution of the melts have a topology that only allows for very approximate information, typically made of “hot big potatoes” where melts are likely to reside. This is specially the case for many calderas and large stratovolcanoes from subduction zones, and unfortunately such view is not good enough to address the likely size of future events. Petrological studies of erupted crystals can, also in principle, provide a view of the depth and possible variety storage areas. However, geothermobarometry data tend to have large errors on pressure, and in a similar manner to most geophysical data many calderas and stratovolcanoes show a very wide distribution of depths (transcrustal systems?). Notwithstanding, many systems show a broad agreement between the petrological and geophysical data, with three or more storage areas, roughly at 30 km (or deeper), 7-10 km, and 1-3 km. Moreover, the configuration of the distribution of the melts may change over time, and crystal-kinetic and some geophysical data suggest that in mafic volcanoes new connections and merging of melts from different environments may occur days prior to eruption, whereas large-scale amalgamation melts from multiple reservoirs to a much larger one can occur in years to decades in silicic eruptions from calderas. Yet, data from geophysical and petrological studies of several recent monogenetic dike-fed eruptions, show simpler magma plumbing configurations, with well-defined areas of isolated magma storage and connections between them near-real time, from which magmas of different compositions are erupted. In this presentation we will review the data on magma plumbing structure and dynamics from different datasets and discuss how could progress be made for their use in mitigation of volcano hazards.

How to cite: Costa, F. and Metaxian, J.-P.: Transcrustal, interconnected, or isolated magma reservoirs, can we tell the difference?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10207, https://doi.org/10.5194/egusphere-egu24-10207, 2024.

The Qinling Orogen, as the most prominent mountain belt in the central part of China, has experienced multiple tectonic-magmatic thermal events. Abundant granitoids were developed in response to the tectonic regime transformation during Mesozoic. These granitoids serve as valuable indicators to reflect the process and dynamic mechanism of the orogeny, as their growth process hold important structural information about the tectonic evolution. Although some geochronological and geochemical data exist from this region, it lacks systematic and sufficient tectonomagmatic information to develop a regionally coherent and viable geodynamic model for the Mesozoic magmatic evolution of the Qinling Orogen.

This study strategically focuses on the Mesozoic Taibai pluton in the Qinling Orogen, aiming to investigate the relationship between tectonics and magmatism and their variation in time and space during Mesozoic. Through multiscale structural analysis and geochronology methods, we have delineated three deformation phases, with representative rock samples reflecting mid-high temperature deformation conditions, evident in both microscopic observations and EBSD analysis, The quartz’s dynamic recrystallization and c-axis fabric analysis revealed that the Houzhenzi Shear Zone (HSZ, south of the Taibai pluton) experienced deformation under green-schist facies conditions at ∼400–550 °C. The results of Anisotropy of Magnetic Susceptibility indicate that the HSZ deformed in response to pure shear-dominated transpression and top-to-NW shear sense, exhibiting two superimposed phases of shear deformation. Together with previously published data, our results concluded the relationship between the Taibai pluton and the structural features of shear zones. The research indicates that the Qinling Orogen was dominated by compressional tectonics during the Late Mesozoic, Taibai pluton was obliquely extruded under the influence of surrounding shear zones. This research contributes to a more comprehensive understanding of the complex processes involved in continental tectonics and magmatic evolution. This work was financially supported by NSFC projects (grants 4217020371, 4180020120).

How to cite: Yan, S., Li, Y., Tao, W., Liu, Y., and Liu, F.: Structural Study of the Taibai Pluton in the Qinling Orogen, Central China: Implications for Relationship between Tectonics and Granite Magmatism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10396, https://doi.org/10.5194/egusphere-egu24-10396, 2024.

EGU24-10782 | ECS | Posters on site | GMPV7.2

Complex magma flow dynamics within fossil dykes: linking multi-method observations across scales from the Reyðarfjörður dyke swarm, eastern Iceland. 

Stefano Urbani, Janine Kavanagh, Tegan Havard, Dawid Rybak, Katharine Gilchrist, Simon Martin, Andrew Biggin, Elisabetta Mariani, and Steffi Burchardt

Since dykes represent the main mechanism for magma movement from the Earth’s crust to the surface, understanding how they generate a path to feed an eruption is crucial for volcanic hazard assessment. To this purpose, key information can be obtained by studying fossil dykes in extinct and eroded volcanic systems where dykes show a variety of shapes, segmentation, and propagation paths due to a suite of pre-, syn- and post-emplacement physical processes (e.g. heat transfer, host rock layering, local stress variations).

To discern the factors that control these complex geometries and reveal how they affect the dynamics of magma transport, we used a multi-method approach on a N-S trending fossil dyke from the Reyðarfjörður dyke swarm (eastern Iceland). We collected meso-scale geometric data from drone photogrammetry, and rock magnetic, petrographic and microstructural laboratory analyses were conducted on oriented rock cores and samples to reveal microscopic magma flow indicators (e.g., magnetic fabrics and crystal alignment). Rock cores were sampled both across the thickness and along the breadth of the dyke segments, also recording the core position relative to different cooling surfaces (i.e. from the dyke margin to its interior).

The studied dyke is exposed for ˜900 m across its breadth in ˜300 m height. It comprises several segments showing different shapes (from straight to curved paths), thickness (spanning from 0.5 to 5 m) and linkage pattern (i.e. connected or not connected segments). The photogrammetry and geological field observations show the curved segments are more frequent in the shallower and thicker portions of the dyke, whereas the amount of offset, overlap and spacing between the segments is higher in the shallower portions of the dyke exposure. Anisotropy of magnetic susceptibility (AMS) and anisotropy of anhysteretic remanent magnetization (AARM) were used to identify magnetic fabrics that may be related to magma flow in the rock cores. These results show that the magnetic data record complex magma flow dynamics spanning from sub-horizontal to subvertical along the dyke path, which is inferred for adjacent connected segments and from the dyke margin to its interior.

We relate the geometrical variability of the dyke segments to the far-field stress (controlled by regional extension) versus the near- field stress (controlled by local magma overpressure), the latter being dominant in the shallower (and thicker) portions of the dyke. This generates a mixed mode fracturing during dyke propagation, reflecting its geometrical variability, that also controls a complex magma flow pattern within the dyke. Microstructure analysis is in progress and it is expected to complement magnetic fabric analysis and fieldwork in the interpretation of magma flow dynamics. Current results already show that a multimethod approach aimed at linking observations from the mesoscale to the microscale is required to better capture small scale and complex propagation paths and magma flow patterns providing more reliable insights on dyke propagation.

How to cite: Urbani, S., Kavanagh, J., Havard, T., Rybak, D., Gilchrist, K., Martin, S., Biggin, A., Mariani, E., and Burchardt, S.: Complex magma flow dynamics within fossil dykes: linking multi-method observations across scales from the Reyðarfjörður dyke swarm, eastern Iceland., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10782, https://doi.org/10.5194/egusphere-egu24-10782, 2024.

Dikes supply magma to most volcanic eruptions. Understanding under what conditions propagating dikes reach the surface to erupt or, alternatively, become arrested (stop their propagation) or deflected so as to propagate primarily laterally or change into sills, is thus one of the fundamental tasks of volcanology. Many dike segments injected from magma sources do not reach the surface to feed volcanic eruptions. Instead, the dike segments become arrested, commonly at or close to contacts between mechanically dissimilar layers/units, at various crustal depths. This means that many and perhaps most volcanic unrest periods with dike injections do not result in eruptions. There are several conditions in the crust that make dike arrest likely, but the main one is layering where the layers have contrasting mechanical properties. Such layering means that local stresses are heterogeneous and anisotropic and thus in some layers unfavourable (e.g., because the layers act as stress barriers) for vertical dike propagation, resulting in dike arrest, lateral dike propagation beneath the stress barrier, or dike deflection into a sill. Here I show that once a dike has formed, its very existence tends to make the local stress field along the dike homogeneous (with invariable orientation of principal stresses) and favourable (with dike-parallel orientation of the maximum compressive principal stress) for later dike injections. This means that a later-injected dike may use an earlier-injected dike as a path, either along the margin or the centre of the earlier dike, thereby generating a multiple dike. Because earlier feeder-dikes form potential paths for later-injected dikes to the surface, many volcanic eruptions are fed by multiple dikes. Multiple dikes thus tend to favour dike propagation to the surface, thereby facilitating dike-fed eruptions. Examples of multiple-dike-fed eruptions include recent ones in Etna (Italy) and Kilauea (Hawaii), as well as in the Icelandic volcanoes Krafla and Hekla. Here, however, the focus is on several eruptions in the past few years on the Reykjanes Peninsula, Iceland. In particular, I discuss the eruptions of 2021, 2022, and 2023 in the volcano Fagradalsfjall as well as the 2023 eruption along the volcanic fissure Sundhnukar (close to the town of Grindavik), all the eruptions occurring on the Reykjanes Peninsula.

Gudmundsson, A., 2022. The propagation paths of fluid-driven fractures in layered and faulted rocks. Geological Magazine, 159, 1978-2001.

Gudmundsson, A., 2023. Multiple dikes make eruptions easy. EarthArXiv, https://doi.org/10.31223/X5M67Q

 

How to cite: Gudmundsson, A.: How multiple dikes facilitate volcanic eruptions, with application to recent events on the Reykjanes Peninsula, Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12898, https://doi.org/10.5194/egusphere-egu24-12898, 2024.

EGU24-13447 | Posters on site | GMPV7.2

Advances in Igneous Petrology: Coupled chemical maps & thermodynamic models to tackle mushes crystallization dynamics 

Lydéric France, Aurore Toussaint, and Valentine Charvet

The assemblage and evolution in time through various differentiation processes of igneous reservoirs shapes magmatism expressions at depth and at surface. Our knowledge of those systems largely relies on theoretical or applied thermomechanical and kinetic models, on geophysical data from active systems, and on structural and petrological data from active and fossil systems. Petrological approaches commonly use textures, thermodynamic models, chemical compositions of major and trace elements to decipher on the dynamics of complex igneous processes. Although chemical maps are more and more common, the overwhelming of the published data reposes on punctual measurements.

Here by using the example of a basalt crystallizing from liquidus to solidus in closed system, we present a new petrological approach that couples chemical maps to thermodynamic models to provide the first maps of thermodynamic parameters with a value attributed to each pixel (e.g., temperature or melt fraction maps in plutonic rocks). If the cooling rate is quantified by other means (e.g., diffusion chronometry), then the first of its kind movies of the crystallization evolution can be built from the first crystal to form to the last melt drop crystallization. We will present such results, allowing the igneous petrologist to explore their data in a new perspective. As an example the studied samples could be observed at various stages of the crystallization path highlighting a heterogeneous interstitial melt spatial distribution during magma solidification. This result has potentially important implications on melt segregation at the scale of the igneous reservoir. The presented results highlight that such a heterogeneous melt distribution was already present at the magma/mush transition. Additional simplified numerical crystallization models suggest that this heterogeneous a melt distribution is related to an early heterogeneous nucleation process, and may be common in volcanic and igneous plumbing systems.

Overall, this new approach will eventually help to make progress in our understanding of igneous systems.

How to cite: France, L., Toussaint, A., and Charvet, V.: Advances in Igneous Petrology: Coupled chemical maps & thermodynamic models to tackle mushes crystallization dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13447, https://doi.org/10.5194/egusphere-egu24-13447, 2024.

EGU24-14370 | Orals | GMPV7.2

Magmatic Structure and Melt Storage beneath the Katmai Volcanic Group, Alaska 

Graham Hill, Paul Bedrosian, Bethany Burton, Jade Crosbie, Bennett Hoogenboom, Michael Mitchell, Jared Peacock, and Erin Wallin

The Katmai volcanic group (KVG) within the Alaskan Aleutian arc is an unusually dense group of active volcanic centres (Mounts Martin, Mageik, Trident, Katmai, Griggs, Snowy, and Novarupta). The KVG was the locus of the largest eruption of the 20th century. During the 1912 eruption, rhyolite was erupted from a new vent (Novarupta) contemporaneous with the collapse of nearby Mount Katmai (10 km away). A hydraulic connection has been hypothesized between the two vents based on the above observation and on a small volume of juvenile andesitic magma with the geochemical signature of Mount Katmai that erupted from Novarupta at the onset of the three-day eruption. Unanswered questions about the structure and dynamics of the KVG include the origin and storage zone for the 1912 erupted rhyolite, its connection (if any) to the dense group of andesitic stratovolcanoes surrounding the Novarupta vent, the cause for off-arc centres such as Mount Griggs, and the reason for enhanced magmatic flux beneath the KVG relative to other segments of the arc. Our recent wideband (1 kHz – 1 mHz) magnetotelluric survey of the region encompasses the entire Katmai group of volcanoes (110 sites) and is bisected by an arc-perpendicular profile crossing the Alaska Peninsula (18 sites) and spanning subducting slab depths of 60-200 km. Coast effects are present in the magnetotelluric data; however, qualitative analysis of the data indicates the Jurassic sedimentary section upon which the arc is built, the highly resistive arc itself, and a swath of elevated conductivity beneath the arc axis that likely reflects melt storage. 3D inversion of the data is ongoing.

How to cite: Hill, G., Bedrosian, P., Burton, B., Crosbie, J., Hoogenboom, B., Mitchell, M., Peacock, J., and Wallin, E.: Magmatic Structure and Melt Storage beneath the Katmai Volcanic Group, Alaska, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14370, https://doi.org/10.5194/egusphere-egu24-14370, 2024.

EGU24-14687 | ECS | Posters on site | GMPV7.2

The geochemical evolution of an extreme rejuvenated lava: A case study on Aitutaki of the Cook-Austral island chain   

Angus Rogers, Oliver Nebel, Hugh O'Neill, Greg Yaxley, Yona Nebel-Jacobsen, and Xueying Wang

Aitutaki is a basaltic Ocean Island in the South-Central Pacific Ocean, a region densely populated with age-progressive islands and seamounts considered to be a result of three or more overlapping mantle plumes. Recent (~1.9 Ma) volcanic activity at Aitutaki is difficult to reconcile with direct melting of a mantle plume, and may instead be an example of rejuvenation, whereby volcanism reappears after an extended hiatus. We have analysed samples of 21 lavas collected from Aitutaki for whole-rock major and trace elements and radiogenic isotopes, with electron probe microanalysis (EPMA) of olivine crystals and xenocrysts. Whole-rock MgO in these samples ranges from 10.3 to 13.9 wt. %. Petrographic examination and EPMA data indicate olivine accumulation is not the cause of these high values. Evidently, very little fractionation occurred during melt ascent through the volcanic plumbing network. Direct eruption of high-MgO (>10 wt.%) primitive magma is unusual in Ocean Island basalts, except among rejuvenated volcanics.

Our radiogenic isotope data closely overlap in Pb-isotope space with the nearby Samoan rejuvenated lavas from Savai’i and Tutuila, and otherwise have an EM1-FOZO signature. The major elements, trace elements and radiogenic isotopes all distinguish two populations of lavas, indicating the lavas are sourced from different regions or source materials in the asthenosphere. By analysing the spatial distribution of these chemical anomalies on the island, we observe the least evolved and most trace-element enriched samples (lowest SiO2, highest Th/Y) concentrate in geographically distinct regions on the island. Without a geochemical continuum between these two populations, we suggest the surface distribution of the enriched and depleted lavas may reflect spatial isolation of the mantle sources. Aitutaki produced multiple pulses of geochemically diverse lavas with extreme compositions throughout a short-lived (~50 ka) rejuvenated eruption cycle, exemplifying the processes responsible for producing rejuvenated lavas and challenging our understanding of the petrogenesis of such volcanism.

How to cite: Rogers, A., Nebel, O., O'Neill, H., Yaxley, G., Nebel-Jacobsen, Y., and Wang, X.: The geochemical evolution of an extreme rejuvenated lava: A case study on Aitutaki of the Cook-Austral island chain  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14687, https://doi.org/10.5194/egusphere-egu24-14687, 2024.

EGU24-15239 | Orals | GMPV7.2

Modelling multi-phase flows in magmatic systems 

Tobias Keller

Magmatic systems in the Earth's mantle and crust range from melt-poor partially molten rock, to mush bodies at intermediate melt fractions, and lenses of melt-rich, eruptible magma suspensions. Previous process-based models, however, have represented magmatic systems as either porous flows at low melt fractions (<20%) or suspension flows at high melt fractions (>60%). A lack of theoretical basis to represent mush flows at intermediate phase fractions has thus far hindered investigations into the dynamics of crustal mush bodies. Previous theories were formulated specifically for two-phase flows of melt-solid mixtures, hence not allowing for the inclusion of a third, volatile or other fluid phase. My contribution addresses this gap by presenting a comprehensive theoretical model [1] of magmatic multi-phase flows across all phase fractions at the system scale, rooted in mixture theory. I substantiate its applicability with a numerical implementation utilising a finite-difference staggered-grid approach [2]. 

 

Numerical experiments replicate expected behaviours for two-phase flows including rank-ordered porosity wave trains in 1D, and porosity wave breakup in 2D in the porous flow regime, as well as particle concentration waves in 1D, and mixture convection in 2D in the suspension flow regime. In the mush regime, numerical experiments show strong melt localisation into lenses and stress-aligned melt-shear bands. A further application to a three-phase flow problem of immiscible melt segregation from a crystallising magma body demonstrates the versatility of the theoretical model and its numerical implementation. The model code is available open source at github.com/kellertobs/pantarhei.

 

References

[1] Keller & Suckale, GJI, 2019. https://doi.org/10.1093/gji/ggz287.

[2] Wong & Keller, GJI, 2022. https://doi.org/10.1093/gji/ggac481.

How to cite: Keller, T.: Modelling multi-phase flows in magmatic systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15239, https://doi.org/10.5194/egusphere-egu24-15239, 2024.

EGU24-16269 | Orals | GMPV7.2

Direct coupling of petrological and thermo-kinematic modelling: application to magmatic chambers 

Nicolas Riel, Boris Kaus, Hendrik Ranocha, Pascal Aellig, and Eleanor Green

Understanding how magmatic systems work is of interest to a wide range of Earth Scientists. One of the key components when studying magmatic systems is the ability to predict stable mineral assemblage. These predictions allow retrieving critical information such as mineral stability, fraction and composition of melt.

However, the dynamic evolution of magmatic chambers, including the cycling between magmatic recharge and extraction in and out of the reservoir, imply that compositions of crystals and melts are constantly evolving. Hence, the use of phase equilibrium parameterization or look-up-tables of fixed bulk-rock composition is inappropriate to predict the dynamic chemical evolution of magmatic systems, and we instead need methods that can take the evolving chemistry into account.

Here, we present an updated version of our in-house Gibbs energy minimization package, MAGEMin [1,2]. MAGEMin is ideally suited so simulate the chemical evolution of magmatic systems by incorporating a range of recently developed thermodynamic melting models suitable to simulate both melting of magmatic arcs and of pelitic crustal rocks. Through its Julia wrapper, MAGEMin_C, it is particularly easy to perform (parallel) pointwise computations, and couple it with other thermal or thermomechanical codes.

We have made several additions to MAGEMin which include a) adding more thermodynamic databases, b) developing a new web-based graphical user interface, MAGEMin_app, which simplifies creating publishable phase diagrams and c) coupling MAGEMin with dynamic codes.

The ability to couple MAGEMin with other codes is demonstrated by linking it with the MagmaThermoKinematics.jl Julia package [4,5] that simulates the thermal evolution of magmatic systems following the intrusion of dikes and sills, in 2D, 2D axisymmetric and 3D geometries. For this to be efficient, we develop a new system in which we dynamically create a database of pre-computed points as a function of pressure, temperature and chemistry that is updated on the fly. This allows simulating the evolving chemistry of a crustal-scale mush system.

 

[1] Riel, N., Kaus, B.J.P., Green, E.C.R., Berlie, N., 2022. MAGEMin, an Efficient Gibbs Energy Minimizer: Application to Igneous Systems. Geochem Geophys Geosyst 23. https://doi.org/10.1029/2022GC010427

[2] https://github.com/ComputationalThermodynamics/MAGEMin

[3] https://github.com/ComputationalThermodynamics/MAGEMin_C.jl

[4] Schmitt, A.K., Sliwinski, J., Caricchi, L., Bachmann, O., Riel, N., Kaus, B.J.P., de Léon, A.C., Cornet, J., Friedrichs, B., Lovera, O., Sheldrake, T., Weber, G., n.d. Zircon age spectra to quantify magma evolution. Geosphere 19. https://doi.org/10.1130/GES02563.1

[5] https://github.com/boriskaus/MagmaThermoKinematics.jl

How to cite: Riel, N., Kaus, B., Ranocha, H., Aellig, P., and Green, E.: Direct coupling of petrological and thermo-kinematic modelling: application to magmatic chambers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16269, https://doi.org/10.5194/egusphere-egu24-16269, 2024.

Carbonatite deposits are rare magmas which represent the primary source of Rare Earth Elements (REE) on Earth; those are often associated with alkaline silicate magmas. A unique opportunity to investigate the natural carbonatite system exists through the study of the only active extrusive carbonatite volcano on Earth, the Oldoinyo Lengai (Tanzania). It has been proposed that carbonatites could be produced by low-degree partial melting of upper mantle domains associated with protracted differentiation that eventually form phonolite together with immiscible carbonatite melts. In such a model, the primitive magmas are proposed to be melilitites or Mg-nephelinite. However, a comprehensive study of the crystallization and immiscibility processes related to those parental melts is still missing.

In this study, we performed equilibrium and fractional crystallization experiments in order to understand the differentiation behaviour of carbonatites' parental magmas at high-pressure, and to decipher on the role of both melilitites or Mg-nephelinite in carbonatite genesis. Volatiles were introduced to both melilitite and Mg-nephelinite starting compositions, and the initial volatile contents (1.2 wt.% of H2O and 0.6 wt.% of CO2) were referred to the previous melt inclusion study by Mourey et al. (2023). The conditions of the first fractional crystallization experiments were established to be just below the liquidus temperature of each composition, i.e., for melilitite = 1250 °C and for Mg-nephelinite = 1200 °C and the subsequent experiments are performed by decreasing the temperature by 15 to 30 °C in each step. At each step, the melt composition in equilibrium with crystallized minerals is determined using an electron microprobe and, mass balance calculations for volatiles. All the experiments were performed at a nominal pressure of 1 GPa (relevant for lower crustal conditions in the Oldoinyo Lengai system), using a piston-cylinder apparatus. A double capsule setup made of AuPd was used to avoid iron and volatile losses during the experiments.

Equilibrium crystallization has not been able to produce phonolite magmas, the evolved term that is observed in the natural system in equilibrium with immiscible alkaline carbonatites. The fractional crystallization experiments of Mg-nephelinite composition highlight an evolution towards the alkaline-rich phonolites after 60% of fractionation, while the evolution of melilitite experiments seems to follow chemical trends that are not consistent with the natural liquid line of descent. The alkaline silicate melt remains abundant in all the fractional crystallization experiments (>65%), which facilitates an efficient equilibrium with silicate minerals and oxides, such as olivine, spinel, clinopyroxene, magnetite, perovskite, phlogopite, melilite and garnet. Mineral assemblages present along the liquid line of descent are consistent with the natural record that has been documented at Oldoinyo Lengai by cognate plutonic samples. Experiments are still ongoing to explore the potential occurrence of carbonatite-silicate melt immiscibility at later stages of the crystallization sequence.

How to cite: Abeykoon, S., France, L., Condamine, P., and Dalou, C.: Fractional crystallization of melilitite and Mg-nephelinite at 1 GPa: An experimental study on the petrogenesis of phonolite and related immiscible carbonatite magmas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18599, https://doi.org/10.5194/egusphere-egu24-18599, 2024.

EGU24-20364 | ECS | Posters on site | GMPV7.2

Plutonic formation through sills stacking and amalgamation: The case of Beauvoir rare-metal granite 

Nicolas Esteves, Lyderic France, Pierre Bouilhol, and Michel Cuney

To better constrain the assembly, evolution and magmatic differentiation associated kinematics of granitic intrusions, we took advantage of a 1 km long drilled core of the Echassières-Beauvoir rare metal granite, allowing a high resolution sampling of a fully recovered plutonic body. Structural and textural data, coupled with high-resolution major and trace element composition of the mineral phases (in-situ measurements and chemical map), provide constraints on the differentiation processes and its dynamics. As Li-mica (lepidolite) is a liquidus phase present all along melt evolution, their compositions allow tracking melt batches and their differentiation state. We show that the granite formed through the stacking of deca- to hectometric crystal-poor sills, defining different sub-units within the granite. As each sub-units are compositionally different, the detailed study of mineral composition provides a dynamic record of the pluton assembly: although globally constructed from bottom to top, sill emplacement can also occur through off-sequence intrusion within or beneath partly crystallized sub-units. Those sub-units seem to be the result of the amalgamation of smaller sills; the latter displaying similar mineral composition from one to the other.

Once intruded these sills crystallize an assemblage of quartz-topaz-mica and alkali-feldspar, recording differentiation trends from core to rim. This differentiation leads to the formation of a quartz-rich mush and associated albite-saturated interstitial residual melts enriched in incompatible elements (e.g. Li, F, P). A part of these residual melts has been extracted from the quartz-rich mush under the form of differentiated magma channels. Now fully crystallized, those channels correspond to albite-rich segregates, forming lobate contacts with the surrounding granite. Locally, these albite-rich segregates are accumulated beneath the overlying subsequently intruded sill, indicating a protracted plutonic construction faster than the solidification of a single sill. Ultimately, the protracted differentiation of the last and upper sub-unit (≈130 m thick) has led to the accumulation of weakly-viscous evolved melt in the upper-part of magmatic reservoir. This newly formed liquid-rich lens could then be mobilized as erupted silica-rich magma, potentially corresponding to rhyolitic intruding the surrounding host-rocks.

How to cite: Esteves, N., France, L., Bouilhol, P., and Cuney, M.: Plutonic formation through sills stacking and amalgamation: The case of Beauvoir rare-metal granite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20364, https://doi.org/10.5194/egusphere-egu24-20364, 2024.

Mid-oceanic ridge basalts (MORBs) are frequently grouped as depleted (D-MORBs), normal (N-MORBs), or enriched (E-MORBs) based on the abundances of highly incompatible elements. E-MORBs, characterized by enriched in incompatible elements, were first noted near mantle plumes, so that enrichment of highly incompatible elements was initially understood as a result of infiltration of plume-related melts into the MORB plumbing system. But for E-MORBs far from plumes, it is still controversial of the lithology of enriched components of these E-MORBs. Two major explanations are proposed that the enriched components are generated by the melting of entrained recycled crust (pyroxenite) beneath ridges or by the melting of refertilized peridotites from subducted slabs. The reason for this problem is that melting of the ambient refractory peridotite along with the enriched component will dilute the signals recorded in MORB. Therefore, the in-situ analyses of minerals and/or melt inclusions will shed new light on this question.

Here high-precision in-situ analyses were conducted on olivine and plagioclase in the studied samples. According to the major and minor element contents of olivine phenocrysts, we found they have similar Ni, Mn and Ni/(Mg/Fe) contents with those from N-MORB at a given Fo, indicating a peridotitic source. Furthermore, in-situ Sr isotope in plagioclase phenocrysts and in-situ Pb isotope of plagioclase-hosted melt inclusions are also reported to constrain origin of parental magma. The isotopic results show that unlike the uniform whole-rock 87Sr/ 86Sr and 206Pb/204Pb ratios, the plagioclase phenocrysts record highly Sr and Pb isotopic heterogeneity. Strontium isotopic heterogeneity is observed between crystals even in a single thin section. Based on the high An contents of plagioclase phenocrysts and chemical disequilibrium between plagioclase phenocrysts and groundmass, we propose they crystallized early in the magma chamber and were most likely formed in different batches of mantle-derived melts. The enrichment of LREE and negative correlations between La/Sm and Pb isotopes melt inclusions, suggest that ancient continent lithosphere materials are likely present in the sub-ridge mantle of the east of the Melville FZ, SWIR. Collectively, we proposed that the continent lithosphere materials were slabbed into the upper mantle under MOR as refertilized peridotites.

How to cite: Li, J., Chen, L., and Dong, Y.-H.: Constraints on the mantle lithology of enriched components: evidence from E-MORB of Southwest Indian Ridge, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21561, https://doi.org/10.5194/egusphere-egu24-21561, 2024.

EGU24-21736 | ECS | Posters on site | GMPV7.2

Fe-valence in magmatic clinopyroxene and the redox state of oceanic basalts – perspectives from natural samples and experiments 

Alex G Stewart, Margaret E Hartley, Rhian H Jones, Jon W Fellowes, and David A Neave

The redox state of magmatic systems controls important physico-chemical properties and processes on the Earth, such as the composition of volcanic gases, the rheology of magma, and the transport and deposition of critical metals. In natural silicate magma, Fe is the most abundant multivalent element, and the redox state of the system can be determined if the relationship between Fe valence and fO2 is known. Popular oxybarometers (e.g., Fe3+/FeT in glass or Fe-Ti oxide pairs) can accurately determine the redox state of magmatic systems but suffer limitations such as beam damage during analysis or the requirement of specific phases to be present.

Clinopyroxene is a common igneous mineral that plays a key role in chemical cycling on Earth and is found in igneous rocks ranging from near-primary basalts to rhyolites. Clinopyroxene can incorporate both Fe2+ and Fe3+ and may capture a record of magmatic redox state upon crystallisation. However, attempts to quantify how Fe valence varies in clinopyroxene as a function of redox state are limited, partly due to the inability to routinely measure Fe valence using electron probe microanalysis (EPMA).

To remedy this, we are exploring the utility of the “flank method” [1] and conventional stoichiometric estimates for determining Fe valence using EPMA. Using a suite of Mössbauer calibrated clinopyroxene standards, preliminary “flank method” analyses demonstrate that the FeO content of clinopyroxenes ranging from diopside (FeOT = 3 wt%) to aegirine (FeOT = 28 wt%) can be determined with a RMSE of 0.03 wt%. Additional standards with FeOT from 2 – 10 wt% are being collated to improve the performance of this method when applied to augitic clinopyroxene. Furthermore, it is possible to obtain 3σ uncertainties on Fe3+/FeT of 3-7% using conventional stoichiometric estimates if EPMA analyses are sufficiently precise [2].

Using high-precision EPMA and stoichiometric estimates of Fe3+, we demonstrate that clinopyroxene crystals in oceanic basalts from the Reykjanes Ridge, Iceland and the Canary Islands have Fe3+/FeT of 0.1 – 0.7. Olivine-glass and olivine-spinel pairs constrain the redox state of these oceanic basalts to be equivalent to FMQ, FMQ+1.5 and FMQ+2, respectively, in line with independent estimates from the literature. The partitioning of Fe3+ between clinopyroxene and melt (KD Fe3+cpx-melt) ranges from 0.50 – 1.4 in tholeiitic to alkali basalts, and we show that clinopyroxene Fe3+/FeT increases concomitantly with estimates of redox state.

However, there is currently limited experimental data in which Fe3+ has been measured with sufficient accuracy or precision to fully understand the controls on Fe3+ partitioning in basaltic systems, precluding the use of clinopyroxene as a probe for magmatic redox at present. An experimental campaign is currently underway to help refine models of Fe3+ partitioning, ultimately contributing to the development of a clinopyroxene based Fe-oxybarometer, and to shed light on the poorly defined role of Fe3+ in the chemical evolution of basaltic magmatic systems.

 

[1] Hofer & Brey, 2007. Am Min, 92, pp.873-885.

[2] Neave et al., 2024. CMP, 179, 5. doi: 10.1007/s00410-023-02080-2

How to cite: Stewart, A. G., Hartley, M. E., Jones, R. H., Fellowes, J. W., and Neave, D. A.: Fe-valence in magmatic clinopyroxene and the redox state of oceanic basalts – perspectives from natural samples and experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21736, https://doi.org/10.5194/egusphere-egu24-21736, 2024.

EGU24-53 | ECS | Posters on site | GMPV7.4

Rapid trans-crustal movement of arc magma under Pagan volcano, Northern Mariana 

Xiaohan Huang, Alexandra Yang Yang, Mingdao Sun, Siyu Zhao, Wei Tan, Yoshihiko Tamura, and Taiping Zhao

Nearly 800 million people worldwide are exposed to volcanic hazards, with two-thirds of these areas located in subduction zones. Studying the movement of arc magma in subduction zones is particularly essential for volcanic hazard prevention. In particular, rapid trans-crustal movement of arc magma from the mantle can lead to volcanic eruptions with little warning, which would pose a high risk, yet research in this area is scarce. This paper reports for the first time the rapid trans-crustal movement of arc magma in the Izu-Mariana Arc. Systematic analyses on the volatile contents of melt inclusions in primitive olivine from the Pagan arc volcano yield exceptionally high CO2 contents of up to 6000 ppm with H2O contents of 3.7 wt%, which record magma storage at near-Moho depth of ~20 km. Diffusion chronometry of Fo, Ni and Mn in the host olivine, on the other hand, reveals that the parental magma took 15-125 days to ascend from near-Moho storage before its eruption. Such a rapid ascent of high Fo olivine from Moho to eruption is rare in arcs. That is because arc magma mostly has high water contents which would lead to viscous stalling during ascent and then delay the eruption. However, magma under Pagan volcano stored at a deeper depth than other arc volcanoes with similar water content, still ascended to eruption at a high rate. High CO2 content and exsolution in Pagan magma, compared to other arc magmas, which could provide additional buoyancy or significant overpressure through continuous CO2 degassing, and then result in rapid ascent.

How to cite: Huang, X., Yang, A. Y., Sun, M., Zhao, S., Tan, W., Tamura, Y., and Zhao, T.: Rapid trans-crustal movement of arc magma under Pagan volcano, Northern Mariana, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-53, https://doi.org/10.5194/egusphere-egu24-53, 2024.

EGU24-297 | ECS | Posters on site | GMPV7.4

Multi-level magma storage and continuous mafic recharge controlling explosive activity in Raung volcano, Indonesia: Evidence from thermobarometric estimate 

Mradipta Lintang Alifcanta Moktikanana, Tsukasa Ohba, Agung Harijoko, and Haryo Edi Wibowo

The study of magma plumbing system underneath a volcano is important to understand eruption triggers, estimate the probability of another eruption, and predict future eruptive behavior. Raung Volcano, located in East Java, Indonesia, is a very active volcano with a long-established basaltic to dacitic magma system. The most recent activity in 2022 was dominated by andesitic Strombolian explosions. However, several Plinian eruptions in the VEI-4 to VEI-5 scale had been documented in both andesite and dacite composition. Despite its variety of eruptive behaviors and potential hazards, Raung magma plumbing system is poorly understood. We investigate the depth and temperature of magma storage underneath Raung volcano by applying several thermobarometer models, including clinopyroxene-melt thermobarometry, orthopyroxene-melt thermobarometry, plagioclase-melt thermobarometry, and olivine-melt thermometry. Our findings reveal that there are five levels of crystallization below Raung from the upper crust to the crust-mantle boundary, at depths of 1.5 – 11 km, 11 – 15 km, 15 – 22 km, 18 – 26 km, and 26 – 30 km. These depths correspond to the major lithological boundary of East Java's sediment thickness (10 – 15 km), crust thickness (10 – 25 km), and Moho depth (25 – 39 km). This suggests that Raung magma storage is controlled by crustal structure. Textural features such as mantled pyroxene, sieved plagioclase, and oscillatory zoned crystals indicate a significant rate of continuous hotter, mafic magma recharge, supplying heat and volatiles into shallower reservoir. These features imply that multi-level magma storage and highly dynamic magma plumbing system play major roles in triggering Raung explosive eruption. Better understanding of Raung complex magma system is important for forecasting the timing and explosivity of potential eruptions, as well as improving long-term hazard mitigation.

How to cite: Moktikanana, M. L. A., Ohba, T., Harijoko, A., and Wibowo, H. E.: Multi-level magma storage and continuous mafic recharge controlling explosive activity in Raung volcano, Indonesia: Evidence from thermobarometric estimate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-297, https://doi.org/10.5194/egusphere-egu24-297, 2024.

EGU24-459 | Posters on site | GMPV7.4

The influence of carbonate assimilation and deformation regime on the multiphase rheology of a phonotephritic melt from Vesuvius 

Gabriele Giuliani, Fabrizio Di Fiore, Silvio Mollo, Claudia Romano, Danilo Di Genova, and Alessandro Vona

The emplacement of magma chambers within a carbonate basement promotes a sequence of thermochemical reactions that progressively evolve from the carbonate wall-rock towards the magma, altering the chemical composition of the overall system (crystal + melt). Recent petrological and experimental studies highlight that varying degrees of limestone/dolostone assimilation controls the liquid line of descent of magmas, promoting or hindering the crystallization onset of distinct mineral phases.

In this study, we investigate how differing degrees of limestone/dolostone assimilation and deformation regimes impact the rheology of a leucite-bearing phonotephrite magma from Somma-Vesuvius (Italy). Using starting materials doped with 0, 10, or 20 wt.% of CaO and CaO+MgO, mimicking the effects of limestone/dolostone assimilation, we conducted two sets of crystallization experiments at 1180°C under static and dynamic conditions (shear strain rate of 1 and 5 s-1).    

We observe distinct rheological behaviours among melts as a function of composition and applied shear rate, displaying significant differences in terms of crystallizing mineral phases (±clinopyroxene±melilite±leucite±nepheline in the CaO-doped samples and ±clinopyroxene±melilite±olivine±leucite±nepheline, in the CaO+MgO-doped ones) and final crystal contents. Increased alkaline earth content (both Ca and Ca+Mg) alongside higher shear rates foster crystallization, leading to heightened crystal fractions (up to 51%) and larger crystals. Consequently, in heavily doped samples and under high shear rates, viscosity increased of up to 1.5 Log Pa s due to crystallization, causing the rheological transition from coherent flow to shear localization, culminating in physical separation (i.e., viscous rupture).  

This study underscores the significant influence of deformation on magma, affecting both mineralogical assemblages and crystallization efficiency. These effects compound the pivotal role played by changing magma composition due to carbonate assimilation, governing magma’s crystallization capability, transport properties, and flow behaviour during its ascent from depth to surface.

How to cite: Giuliani, G., Di Fiore, F., Mollo, S., Romano, C., Di Genova, D., and Vona, A.: The influence of carbonate assimilation and deformation regime on the multiphase rheology of a phonotephritic melt from Vesuvius, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-459, https://doi.org/10.5194/egusphere-egu24-459, 2024.

EGU24-551 | ECS | Orals | GMPV7.4 | Highlight

Medieval eruptions in the Reykjanes Peninsula, Iceland: magma storage depths and SO2 emission potentials for future eruption hazard assessment  

Alberto Caracciolo, Enikö Bali, Eemu Ranta, Saemundur A. Halldórsson, and Guðmundur H. Guðfinnsson

The Reykjanes Peninsula, in southwest Iceland, has recently undergone magmatic reactivation with the 2021, 2022 and 2023 AD Fagradalsfjall eruptions. Considering the eruptive history of the peninsula in the past 4000 years, characterized by ~400-year-long rifting episodes at time intervals of 800-1000 years, the current magmatic reactivation could mark the onset of a new rifting episode in the most populated area of Iceland. In this contribution, we present results about magma plumbing configurations1 and SO2 emission potentials2 during past eruptions across the peninsula, which are vital aspects for interpreting pre-eruptive signals and assessing the impact of sulfur release on human health, respectively. We target 16 basaltic lava units erupted in the volcanic systems of Reykjanes, Svartsengi, Krýsuvík and Brennisteinsfjöll during the last medieval rifting episode: the 800-1240 AD Fires. We analysed major and minor element contents of glasses, mineral phases and melt inclusions, and we reconstructed magma storage depths and SO2 emission potentials across Reykjanes Peninsula. Independent clinopyroxene-melt and melt-based barometry show consistent results and suggest that magmas from the western part of the peninsula were extracted from magma reservoirs located at about 5-10 km depth. In contrast, and similar to observations from recent eruptions at Fagradalsfjall, the easternmost system, Brennisteinsfjöll, was fed from deep crustal reservoirs, at about 14-21 km depth. Starting from published lava volumes, we calculate SO2 emission potential across the peninsula to be in the range 0.004-7.4 Mt. These estimates correspond to daily SO2 emissions in the range 600-53000 tons, higher than the mean SO2 field measurements of 5240 ± 2700 tons/day during the 2021 AD Fagradalsfjall eruption. Also, we develop an empirical approach to calculate end-member SO2 emission potentials of any past or ongoing RP eruption of known volume or effusion rate. We conclude that the potential sulfur emissions across the RP can be significantly higher than observed during the 2021 AD Fagradalsfjall eruption, mainly because of the more evolved nature and higher sulfur contents of magmas erupted during the 800-1240 AD Fires. In the light of the ongoing magmatic unrest at Svartsengi, our work emphasizes the significance of petrological and geochemical studies of past eruptions for interpreting future pre-eruptive signals and developing future eruption mitigation strategies.

1 Caracciolo, A. et al. Magma plumbing systems and timescale of magmatic processes during historical magmatism on Reykjanes Peninsula. Earth and Planetary Science Letters  621, 118378 (2023). https://doi.org/10.1016/j.epsl.2023.118378

2 Caracciolo, A. et al. Reykjanes Peninsula's historical eruptions: SO2 emissions and future hazard implications (GPL, under review). Preprint https://doi.org/10.31223/X5TX05

How to cite: Caracciolo, A., Bali, E., Ranta, E., Halldórsson, S. A., and Guðfinnsson, G. H.: Medieval eruptions in the Reykjanes Peninsula, Iceland: magma storage depths and SO2 emission potentials for future eruption hazard assessment , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-551, https://doi.org/10.5194/egusphere-egu24-551, 2024.

EGU24-1016 | ECS | Posters on site | GMPV7.4

Petrological and geochemical characterization of the Golja Ignimbrite (Main Ethiopian Rift) 

Federica Langone, Zara Franceschini, Riccardo Avanzinelli, Eleonora Braschi, Francesca Forni, and Raffaello Cioni

The Plio-Pleistocene volcanism of the Main Ethiopian Rift (Ethiopia) is characterized by a bimodal distribution with abundant mafic and felsic compositions and rare intermediate magmas, a feature commonly known as the Daly Gap. The Quaternary activity is characterized by large explosive eruptions associated with caldera collapses that define a regional paroxysm of silicic and basaltic volcanism. The genesis of the evolved compositions and their relationship with the basalts still represents a matter of debate, with interpretations ranging from pure fractional crystallization to more complex scenarios involving magma mixing and crustal melting. Here, we present the first volcanological, petrological and geochemical characterization of a pyroclastic sequence, located in the Central Main Ethiopian Rift, the Golja Ignimbrite (GI). GI is a crystal-poor (<10% crystals of qtz+K-feld+pl+cpx+aen), low aspect ratio ignimbrite that crops out over ~400 km2 and has an estimated bulk-tephra volume of ~100 km3. The pyroclastic sequence is characterized from bottom to top by: 1) a coarsening upward basal fallout layer; 2) an obsidian vitrophyre with rare, scattered fiammae; 3) a weakly to partially welded, lithic-rich PDC deposit and 4) a thick, unwelded PDC deposit containing different types of juvenile material including white, banded pumices and fiamme, as well as dark scoria. Analyses of matrix glass and melt inclusions from all juvenile types reveal a broad compositional spectrum ranging from basalts (found only in the pl-hosted melt inclusions) to rhyolites. Remarkably, we report the occurrence of intermediate compositions (basaltic trachyandesites to trachydacites) found within the mingled pumices and dark scoria. In-situ 87Sr/86Sr analyses of plagioclase display homogeneous isotopic composition with mantle-like signatures akin to the Afar Plume mantle source while Sr isotopic analyses of bulk matrix glasses from the different compositions show both mantle-like and crustal isotopic signatures akin to the Pan African Upper Crust. Bulk 143Nd/144Nd isotopic compositions of matrix glasses do not show significant variations between compositions. Overall, our data indicate a complex geochemical and isotopic evolution, involving fractional crystallization, magma mixing and assimilation of old crustal material. Our data represent the first geochemical characterization of this large ignimbrite and contribute to a better understanding of silicic magmatism in the Central Main Ethiopian Rift.

How to cite: Langone, F., Franceschini, Z., Avanzinelli, R., Braschi, E., Forni, F., and Cioni, R.: Petrological and geochemical characterization of the Golja Ignimbrite (Main Ethiopian Rift), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1016, https://doi.org/10.5194/egusphere-egu24-1016, 2024.

EGU24-1079 | ECS | Orals | GMPV7.4

Discussing the timescales of pre-eruptive gas accumulation beneath Hekla volcano, Iceland, from 210Pb-226Ra systematics. 

Garance Hervé, Olgeir Sigmarsson, and Guðrún Larsen

The last five eruptions at Mt Hekla, Iceland (1947, 1970, 1980, 1991 and, 2000) occurred at a frequency ranging from several decades to every ten years since 1970. The eruptions start with an explosive sub-Plinian phase during which most tephra is emitted. A decrease in eruptive intensity cause basalt-andesite lava emission (SiO2~54 wt%). Hautemann et al. (2017) linked the regular dynamic of Hekla to the accumulation of gas in a deep plumbing system (< 10 km) during periods of quiescence between eruptions. In this study we determine whether the proposed gas accumulation affected 210Pb-226Ra radioactive disequilibrium.

Radon being a noble gas has great affinity for the gas phase, but due to its low concentrations in magma is not able to form a mobile bubble. However, if a major gas phase such as CO2 is released, Radon can diffuse rapidly into the gas-bubble and therefore appears to be a good tracer for tracking a potential gas accumulation. One of its radioactive isotopes present in the 238U series is 222Rn (half-live 3.82 days). It is produced by the decay of 226Ra (half-live 1600 yrs) and quickly decays to form 210Pb. Because 210Pb has a half-life of 22.3 years and higher affinity for the melt phase than Rn, it can be measured in the erupted products. If gas accumulates at the top of the basalt andesite magma chamber, 222Rn carried by the major gas phase should accumulate in the upper part of the reservoir and disintegrate rapidly to 210Pb The first erupted products could thus register an excess of 210Pb over its parent isotopes, 226Ra.

The alpha and gamma spectrometry analysis of the initial tephra from the five most recent eruptions at Hekla volcano reveals a (210Pb/226Ra) of 1.057±0.014 (2σ), (210Pb/226Ra)=1.093±0.020 (2σ) for the 1947 and 1970 eruptions, respectively, while a radioactive equilibrium is observed for the 1980, 1991 and 2000 eruptions. Recalculated to the time of eruption, the ratios amount to (210Pb/226Ra)0=1.58±0.14 (2σ), (210Pb/226Ra)0=1.47±0.09 (2σ) and equilibrium, respectively. These results are consistent with an accumulation of Radon at the top of the magma chamber reflecting CO2 accumulation. At first glance, the rate of gas accumulation seems to be linked to the quiescent time between eruptions. However, other factors, including decrease of the mass of the degassing deep magma may affect this accumulation phenomenon. Evidence of gas accumulation is restricted to the tephra whereas (210Pb/226Ra)0 is equal to unity in the lava, which magma neither accumulated nor degassed Radon. Therefore, a deeper magma (basalt) contributed the CO2 and Radon to the Hekla plumbing system. The decrease in the (210Pb/226Ra)0 in the tephra over the past 70 years coincides with the decline in tephra volume, strongly suggest diminishing mass of deep degassing basalt. The decrease in gas supply and accumulation may explain the current dormancy of Hekla volcano.

References:

Hautmann, Stefanie, I. Selwyn Sacks, Alan T. Linde, and Matthew J. Roberts. 2017. « Magma Buoyancy and Volatile Ascent Driving Autocyclic Eruptivity at Hekla Volcano (Iceland) ». Geochemistry, Geophysics, Geosystems 18 (9): 3517‑29. https://doi.org/10.1002/2017GC007061.

How to cite: Hervé, G., Sigmarsson, O., and Larsen, G.: Discussing the timescales of pre-eruptive gas accumulation beneath Hekla volcano, Iceland, from 210Pb-226Ra systematics., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1079, https://doi.org/10.5194/egusphere-egu24-1079, 2024.

EGU24-1116 | ECS | Posters on site | GMPV7.4

Control of effusive and explosive eruptions of Ciomadul volcano: constraints by apatite composition 

Krisztina Hajdu, Réka Lukács, Razvan-Gabriel Popa, Julien Marius Allaz, Emese Páncél, Barbara Cserép, Olivier Bachmann, Elemér Pál-Molnár, Ioan Seghedi, and Szabolcs Harangi

The Ciomadul Volcanic Complex, Eastern Carpathians, Romania is the youngest volcano in the Carpathian-Pannonian region, eastern-central Europe, where volcanic activity occurred between 160 ka and 30 ka. It is a typical long-dormant volcano, where active stages were divided by several 10’s ka quiescence. Geophysical studies indicate that it is still underlain by a potentially active magma storage (PAMS volcano). Two main stages of volcanism are distinguished that was separated by ca. 40 ka dormancy: the first one (160–95 ka) was characterized by lava dome extrusions, whereas the second one (56–30 ka) was mostly explosive. Magma composition, however, remained homogeneous, i.e., high-K dacitic, which contains plagioclase, amphibole, biotite as well as accessory apatite, titanite and zircon. In this study, we focus on the variation of apatite composition, particularly the changes in the volatile content and its effects on the type of eruptions.

We analyzed the chemical composition of apatite microphenocrysts and inclusions enclosed by amphibole and biotite phenocrysts by microprobe, with special attention to the volatile contents (Cl, F, OH). Samples represent different eruption ages, and both effusive and explosive eruption types. In the xCl/xOH vs. xF/xOH diagram, a breakpoint in the compositional variation of apatite indicates the change of water-saturation state in the magma reservoir, due to the different behavior of Cl and F in water-saturated and unsaturated magmas. Fluorine remains in the melt during water-saturation state, and follows the same trend as in water-undersaturated conditions. In contrast Cl shows similar incompatible behavior in water-undersaurated state, but in water-(over)saturated conditions it enters to the gas phase, so its content in the melt (and in crystal lattice of apatite) is buffered or decreased. We also used MgO content of apatite to follow the behavior of the halogens during the magma differentiation, where high amount of MgO represents the less evolved magma.

We interpret our results that effusive eruptions occurred when the magma reached water-(over)saturated state (constant Cl content). In that case, the eruption triggering recharge event was not able to return the magma to water-undersaturated condition. On the other hand, the explosive events were characterized by magmas became in water-undersaturated state. In the case of the three oldest explosive eruptions the less evolved recharge material was able to return the already saturated magma to water-undersaturated state before the eruptions. The or one of the youngest explosive eruption of the Ciomadul (Bixad) was also explosive, but in this case water-saturated state was not detectable by the apatite record. Similarly to earlier studies of the Ciomadul, our results on apatite composition also indicate the role of mafic magma recharge in the petrogenesis of the rocks and shows that it could have turned the system to water-undersaturated state that eventually led to explosive eruptions.

This study belongs to the K135179 NKFIH-OTKA research project.

How to cite: Hajdu, K., Lukács, R., Popa, R.-G., Allaz, J. M., Páncél, E., Cserép, B., Bachmann, O., Pál-Molnár, E., Seghedi, I., and Harangi, S.: Control of effusive and explosive eruptions of Ciomadul volcano: constraints by apatite composition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1116, https://doi.org/10.5194/egusphere-egu24-1116, 2024.

EGU24-1683 | Posters on site | GMPV7.4

Dynamics of magma mixing and magma mobilisation beneath Mauna Loa – insights from the 1950 AD Southwest Rift Zone eruption  

Maren Kahl, Daniel J. Morgan, Carl Thornber, Richard Walshaw, Kendra J. Lynn, and Frank A. Trusdell

Eruptions from Mauna Loa’s Southwest Rift Zone (SWRZ) pose a significant threat to nearby communities due to high eruption rates and steep slopes resulting in little time for evacuation. Despite the large body of research done on Mauna Loa, knowledge of the timing and duration of magma residence and transfer through its internal plumbing system is still poorly constrained. This study presents a first quantitative look at thermochemical conditions and timescales of potentially deep storage, and disaggregation of magmatic mush during the run-up to the voluminous 1950 AD SWRZ eruption. Details of heterogeneous compositions and textures of the macrocryst and glomerocryst cargo in 1950 AD lavas suggests magma mixing and crystal recycling along the entire plumbing system. Furthermore, the crystal cargo contains evidence for the direct interaction between primitive, deeply stored magma and pockets of more evolved magma stored at shallow to intermediate depths. An enigmatic attribute of 1950 near-vent lava is the near-ubiquitous presence of subhedral, unreacted Mg-rich orthopyroxene phenocrysts (Mg#>80). Phase-relations of Mauna Loa olivine-tholeiite indicate that orthopyroxene joins olivine as a primary phase at pressures higher than 0.6 GPa Coexisting Mg-rich olivine and orthopyroxene and the occurrence of harzburgitic (olivine-orthopyroxene) glomerocrysts provide evidence for cognate crystallization at near-Moho (~18km) depths (Thornber and Trusdell 2008).  Petrogenetically diverse populations of glomerocrysts and macrocrysts alongside evidence of multilevel magma storage indicate a network of ephemeral and possibly interconnected magma pockets from near-Moho depths to the upper/mid-crust. Fe-Mg diffusion chronometry applied to 1950 AD olivine populations implies rapid mobilization and transport of large volumes of magma (376×106 m3) from near-Moho storage to the surface within less than 8 months, with little residence time (~2 weeks) in the shallow (3-5km) plumbing system.

 

Thornber CR, Trusdell FA (2008). Field, petrologic and experimental evidence for rapid transport of large magma volumes from great depths during the 1950 eruption of Mauna Loa, Hawai‘i. IAVCEI General Assembly, August 2008, Reykjavik, Iceland.

How to cite: Kahl, M., Morgan, D. J., Thornber, C., Walshaw, R., Lynn, K. J., and Trusdell, F. A.: Dynamics of magma mixing and magma mobilisation beneath Mauna Loa – insights from the 1950 AD Southwest Rift Zone eruption , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1683, https://doi.org/10.5194/egusphere-egu24-1683, 2024.

EGU24-1798 | ECS | Posters on site | GMPV7.4

Distinct Magma Differentiation Pathways for the Eastern Snake River Plain and Craters of the Moon, Idaho, from Zircon Geochronology and Geochemistry 

Carlos A. Angeles-De La Torre, Axel K. Schmitt, Michael McCurry, Martin Danisik, Oscar M. Lovera, Andreas Hertwig, and Axel Gerdes

The Snake River Plain plateau and the adjacent Columbia River and Yellowstone volcanic fields form one of the world largest flood basalt provinces. Eruptive centers migrated eastward since the late Cenozoic following the Yellowstone hotspot, erupting an archetypical bimodal volcanic suite with compositions ranging from olivine-tholeiite to rhyolite. Up to 80% of the ~1600 km2 eastern portion of the Snake River Plain (ESRP) is covered by mafic lava flows, from which four prominent Pleistocene rhyolite domes emerge. Closely associated with the ESPR is the Craters of the Moon (COM) volcanic field, which is considered the largest Holocene lava field in the ESRP and the United States, with more than 60 eruptions over the past ~15,000 years. Geochemically, COM lavas range from basalt and trachybasalt to trachyte.

To elucidate processes and timescales of evolved magma production, zircon from Quaternary rhyolites from the ESRP was investigated along with zircon from three of the most recent and evolved COM lava flows and those from a COM crustal xenolith. Approximately 300 individual zircon crystals were analyzed for U-Pb and U-Th geochronology, respectively, and paired with crystal-scale δ18O, ɛHf, and trace element analyses. Composite zircon separates from a COM lava flow were also analyzed by combined (U-Th)/He and U-Th dating to constrain its eruption age.

U-Pb zircon dating indicates crystallization ages between 1.54 ±0.01 Ma in the oldest and 0.335 ± 0.003 Ma in the youngest ESRP rhyolite dome, with ages increasing from west to east. For COM trachyte lavas, zircon U-Th disequilibrium corresponds to an age of  ka which along with an indistinguishable (U-Th)/He zircon age demonstrates that zircons crystallized in the evolved magma shortly before the eruption. With the exception of rare Precambrian basement-derived xenocrysts, evolved COM lavas have zircon δ18O values ranging from +5.33 to +6.02, consistent with fractionation from ESRP mantle-derived mafic magmas. On the other hand, δ18O(VSMOW) zircon composition between +1.73‰ to +4.51‰ for ESRP agree with low δ18O Yellowstone rhyolites with decreasing values from west to east. COM lavas display ɛHf zircon values between -12.0 to -8.9, whereas ESPR rhyolite ɛHf zircon ranges from -6.3 to -1.3. The crustal xenolith from COM yielded U-Pb zircon ages between 1.9 and 3.4 Ga, consistent with low ɛHf > -35. These results indicate different pathways of evolved magma production that differ between ESRP and COM.

How to cite: Angeles-De La Torre, C. A., Schmitt, A. K., McCurry, M., Danisik, M., Lovera, O. M., Hertwig, A., and Gerdes, A.: Distinct Magma Differentiation Pathways for the Eastern Snake River Plain and Craters of the Moon, Idaho, from Zircon Geochronology and Geochemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1798, https://doi.org/10.5194/egusphere-egu24-1798, 2024.

EGU24-1847 | ECS | Orals | GMPV7.4

What happens before eruption? Effect of strong crystal content and time dependence of permeability at very low gas content in immobile silicic magmas 

Anna Theurel, Marielle Collombet, Alain Burgisser, Caroline Martel, Laurent Arbaret, and Rémi Champallier

Magmatic outgassing plays a crucial role in the eruptive dynamics of silicic volcanoes. Gas escape from the volcanic conduit is facilitated by the coalescence of gas bubbles, leading to permeable bubble chains that are usually constrained by a crystalline framework within the magma. Our research provides experimental evidence of decompression-induced permeability in gas-poor crystal-rich silicic magmas that are not subjected to external strains. Synthetic samples were produced in Internally Heated Pressure Vessels (IHPV) to constrain and compare gas behavior with varying crystal content and size, and dwelling time. The permeable samples have a mean gas permeability of 10-14 m² for bulk porosity lower than 10% and bulk crystal contents of up to 75 vol%. Our results show that outgassing is possible in stagnant conduit at greater depths than initially assumed. This outgassing occurs even at low gas content, provided that the high crystallinity contains at least a microlite population with possible phenocrysts. Results also reveal a strong time dependence of the permeable bubble-chain lifetime in a closed magmatic system. If the dwelling time is too short, the coalescence process is incomplete, whereas if it is too long, the bubble chains resorb and become impermeable. Even with no magma deformation, the phenomenon of coalescence and percolation, therefore, remains dynamic. Our findings imply a new mechanism of deep outgassing for immobile magmas dominated by capillary forces, which has key implications on the explosive–effusive transition.

How to cite: Theurel, A., Collombet, M., Burgisser, A., Martel, C., Arbaret, L., and Champallier, R.: What happens before eruption? Effect of strong crystal content and time dependence of permeability at very low gas content in immobile silicic magmas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1847, https://doi.org/10.5194/egusphere-egu24-1847, 2024.

EGU24-2154 | ECS | Orals | GMPV7.4

The mildly explosive to caldera-forming transition at Colli Albani volcano  

Mónica Ágreda López, Corin Jorgenson, Luca Caricchi, Guido Giordano, and Maurizio Petrelli

The effusive-explosive transition in mafic systems is a complex and still largely debated phenomenon in volcanology. Understanding this transition is crucial for hazard assessment and risk mitigation since explosive eruptions can pose significant dangers to nearby populations and infrastructure. In this study, we investigate this transition focusing on a natural study case: the Colli Albani volcano. The Colli Albani is an ultrapotassic caldera complex located 30 km SE of Rome. This volcano has exhibited a wide range of eruptive behaviours throughout its history, ranging from effusive activity to highly explosive eruptions (Giordano & CARG Team, 2010). Here, two main eruptive sequences were selected: The Fontana Centogocce formation (SLV) and the Villa Senni ignimbrites (VSN). SLV represents a period of effusive to mild-explosive eruptions and preceded the emplacement of the 50 km3 Villa Senni ignimbrites (VSN), which represent the last caldera-forming event of the volcano.

This study integrates field and petrographic observations, clinopyroxene textural and chemistry analyses and machine learning thermobarometry to understand and constrain the variables influencing the shift from mildly-explosive to caldera-forming eruptions. We present a reconstruction of the volcanic plumbing system's architecture and offer insights into how the system rebuilds in its interim after one of these large events.

 

Giordano, G., & CARG Team. (2010). Stratigraphy, volcano tectonics and evolution of the Colli Albani volcanic field. In: Funiciello, R., Giordano. G. (eds). The Colli Albani volcano. Special Publications of IAVCEI, vol 3, Geological Society, London, 43-98.

How to cite: Ágreda López, M., Jorgenson, C., Caricchi, L., Giordano, G., and Petrelli, M.: The mildly explosive to caldera-forming transition at Colli Albani volcano , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2154, https://doi.org/10.5194/egusphere-egu24-2154, 2024.

EGU24-2569 | Posters on site | GMPV7.4

Quantifying dendritic crystallization in hydrous basaltic magmas through 4D experiments with in situ view: implications for magma mobility within the Earth’s crust 

Fabio Arzilli, Margherita Polacci, Giuseppe La Spina, Nolwenn Le Gall, Edward W. Llewellin, Richard A. Brooker, Rafael Torres-Orozco, Danilo Di Genova, David A. Neave, Margaret E. Hartley, Heidy M. Mader, Daniele Giordano, Robert Atwood, Peter D. Lee, and Mike R. Burton

The mobility and the rheological behaviour of magma within the Earth’s crust is controlled by magma viscosity. Crystallization and crystal morphology strongly affect viscosity, and thus mobility and eruptibility of magma, by locking it at depth or enabling its ascent towards the surface. However, the relationships between crystallinity, rheology and eruptibility remain uncertain because it is difficult to observe dynamic magma crystallization in real time.

Here we show the results of in situ 3D time-dependent, high temperature, moderate pressure experiments performed under water-saturated conditions to investigate crystallization kinetics in a basaltic magma. 4D crystallization experiments with in situ view were performed using synchrotron X-ray microtomography, which provides unique quantitative information on the growth kinetics and textural evolution of pyroxene crystallization in basaltic magmas.  Crystallization kinetics obtained with 4D experiments were combined with a numerical model to investigate the impact of rapid dendritic crystallization on basaltic dike propagation, and demonstrate its dramatic effect on magma mobility and eruptibility.

We observe dendritic growth of pyroxene on initially euhedral cores, and a sur- prisingly rapid increase in crystal fraction and aspect ratio at undercooling ≥30 °C. Rapid dendritic crystallization favours a rheological transition from Newtonian to non-Newtonian behaviour within minutes. Modelling results show that dendritic crystallization at moderate undercooling (30-50 °C) can strongly affect magma rheology during magma ascent within a dike with important implications for the mobility of basaltic magmas within the crust. Our results provide insights into the processes that control whether magma ascent within the crust leads to eruption or not.

How to cite: Arzilli, F., Polacci, M., La Spina, G., Le Gall, N., Llewellin, E. W., Brooker, R. A., Torres-Orozco, R., Di Genova, D., Neave, D. A., Hartley, M. E., Mader, H. M., Giordano, D., Atwood, R., Lee, P. D., and Burton, M. R.: Quantifying dendritic crystallization in hydrous basaltic magmas through 4D experiments with in situ view: implications for magma mobility within the Earth’s crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2569, https://doi.org/10.5194/egusphere-egu24-2569, 2024.

EGU24-3468 | Posters on site | GMPV7.4 | Highlight

The 2021-22 volcanic unrest at Vulcano Island (Italy) inside of 50 years of activity observed with geophysical data. 

Laura Privitera, Alessandro Bonforte, Salvatore Gambino, and Francesco Guglielmino

Vulcano Island is characterized by transitions from phreatomagmatic to minor magmatic activity. The last eruption in 1888–90 saw powerful explosive pulses and this eruption defines what we call today ‘vulcanian’ also for other volcanoes worldwide. Since then, volcanic activity at Vulcano has been limited to the form of fumarolic emanations of variable intensity and temperature, mainly concentrated at “La Fossa” crater and on its northern slope.

In September 2021, La Fossa entered a new phase of unrest with a sudden and significant increase of degassing activity from the crater and with outstanding variations to fumarole gas composition, temperature, plume emissions, diffuse soil CO2 degassing, local seismicity and ground deformation.

We discuss a set of geophysical monitoring parameters which started evidencing changes since middle 2018, and showed an important expansion of La Fossa Cone in 2021 as the result of an increased activity inside the shallow hydrothermal system just below La Fossa.

We discuss the 2021 episode within 50 years of ground deformation and seismicity data collected by INGV, trying to define the elements of comparison, similarities and differences with the hydrothermal unrests already observed during the late 1970s to early 1990s.

How to cite: Privitera, L., Bonforte, A., Gambino, S., and Guglielmino, F.: The 2021-22 volcanic unrest at Vulcano Island (Italy) inside of 50 years of activity observed with geophysical data., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3468, https://doi.org/10.5194/egusphere-egu24-3468, 2024.

Most eruptions tap magmas from a range of pressures and storage environments within the crust and potentially even in the mantle. In this context, early crystallizing phases, such as olivine, provide a unique perspective into the deeper parts of many eruptions. When considering large olivine populations, compositional spectra of those populations serve as proxies for the different batches of magma that constitute the sometimes complex assembly of an eruption. While major element compositions in olivine provide links to melt compositions, minor and trace elements fingerprint deviations from simple liquid lines of descent. Moreover, Fe-Mg isotope signatures demonstrate whether magmas equilibrated diffusively or whether some mineral zoning retains growth histories prior and during assembly.

To reveal the full picture of the assembly of an eruption and potentially changes during the eruption it is essential to collect olivine “interviews” from a large population as they exit the volcano. Here I show that such magma assembly prior to eruption varies greatly from one eruption to the next and that simple monogenetic cones may contain much more complex histories as they quickly pass the crust and may extract crystal cargo from a variety of locations and conditions, while many volumetrically larger more long-lived systems retain a simpler story despite their polybaric magma storage.

How to cite: Ruprecht, P.: Olivine exit interviews – gaining insights into magma assembly from olivine populations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4346, https://doi.org/10.5194/egusphere-egu24-4346, 2024.

EGU24-5141 | Orals | GMPV7.4

Magma ascent in active Australian intraplate basaltic volcanic provinces 

Heather Handley, Ray Cas, Thomas England, and Eric Hellebrand

Australia hosts at least two active continental basaltic volcanic fields with Holocene eruption ages yet very little is understood about magma ascent and mantle to surface ascent pathways and timescales. In this study we use textural and chemical information stored within minerals from two of the youngest volcanic eruptions in northeast and southeast Australia to investigate magmatic plumbing systems and magma ascent in Australia’s intra-plate volcanic fields. Volcanic rock samples from the three main eruptive phases at Mt Schank volcano in the Newer Volcanics Province, South Australia, reveal textural and mineralogical differences throughout the evolution of the eruption that correspond to variations in eruption style and the availability of external water. Crustal xenoliths (e.g., quartz and limestone) are abundant in the middle, maar-forming phase of the eruption. The lack of mantle-derived xenoliths and xenocrysts throughout the eruption, olivine compositions and sector and oscillatory zoned, euhedral clinopyroxene suggest a more stalled ascent pathway of magma compared to the mantle xenolith-bearing volcanoes in parts of the Victorian sector of the province. Skeletal olivine crystals and dendritic clinopyroxene microlites indicate moderate degrees of undercooling at Mt Schank during magma ascent. In northeast Queensland, interaction of magma with mantle xenolith’s are used to determine magma ascent dynamics. Disequilibrium and quench textures and chemical zoning patterns in olivine, clinopyroxene, orthopyroxene and spinel on xenolith margins and within host glass reveal a detailed and complex history of magma ascent.

How to cite: Handley, H., Cas, R., England, T., and Hellebrand, E.: Magma ascent in active Australian intraplate basaltic volcanic provinces, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5141, https://doi.org/10.5194/egusphere-egu24-5141, 2024.

EGU24-5289 | Posters on site | GMPV7.4

Shock-tube experiments and high-speed Schlieren shadow photography for low viscosity analogue materials 

Giuseppe La Spina, Jacopo Taddeucci, Laura Spina, Francesco Pennacchia, and Piergiorgio Scarlato

Volcanic eruptions show a wide range of eruptive stiles, from low intensity effusive eruption to energetic and powerful explosive eruptions. Different styles of activity can be also seen during the same volcanic eruption, particularly when low viscosity magmas, such as basalts, are involved. Yet, the conditions by which fragmentation of basaltic magmas is achieved (and thus the generation of explosive eruption) are not fully understood. This poses a real challenge to policymakers tasked with mitigating the risks associated with eruptions of basaltic volcanoes.

In order to better understand the fragmentation of low viscosity magma, we employed a brand new apparatus combining a shock-tube apparatus together with a high-speed Schlieren shadow photography and acoustic sensors.

We present preliminary results obtained with this new apparatus performing experiments either with water or different analogue materials. We performed experiments varying also parameters, such as the length and the diameter of the conduit, the fractal dimension of the tube and the pressure gradient.

How to cite: La Spina, G., Taddeucci, J., Spina, L., Pennacchia, F., and Scarlato, P.: Shock-tube experiments and high-speed Schlieren shadow photography for low viscosity analogue materials, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5289, https://doi.org/10.5194/egusphere-egu24-5289, 2024.

During magma ascent, the growth, ascent, and bursting of bubbles play a pivotal role, intricately linked with the rheological properties of magma. In the realm of this complexity, viscoelasticity stands out as a crucial factor influencing infrasound generation resulting from bubble bursting in volcanic systems. The linear Maxwell model, a fundamental representation of magma viscoelasticity, serves as a starting point for our investigation.

In this study, we explore acoustic wave generation induced by bubble bursting in two distinct fluids: a Maxwell-type viscoelastic fluid (CTAB) and a Bingham-type yield-strength fluid (GEL). Despite both fluids exhibiting similar rigidity in the linear elastic regime, their fracture and flow behaviors diverge significantly. The acoustic signals generated by these fluids display pronounced variations, contingent upon factors such as flux (Q) and the depth of air injection (h).

In the case of CTAB, bursting sounds are observed exclusively in the brittle regime at elevated Q, characterized by successive fractures within the fluid. At shallow injection depths, these fractures extend from the nozzle to the fluid surface, creating distinct acoustic waves. Deeper air injection results in crack growth, detachment from the nozzle, ascent to the surface, and subsequent acoustic wave generation. Interestingly, a round cavity, exclusive to small Q, does not produce acoustic waves.

In contrast, GEL consistently forms a round air cavity, with the initial bursting being silent within the same range of Q and h as observed in CTAB. Brittle fractures are notably absent, and acoustic wave generation occurs only with continued air injection, indicating that rigidity alone does not dictate bursting sound; rather, it hinges on fluid brittleness and gas-flow conditions, including rate, depth, and injection history. This experimental exploration sheds light on the nuanced interplay between fluid properties and gas-flow dynamics in the context of acoustic wave generation during bubble bursting.

           

How to cite: Sánchez, C., Ichihara, M., and Muramatsu, D.: Viscous-Flow-to-Fracture Transition in Linear Maxwell Fluids vs. Yield-Strength Materials: Implications for Magma Fracturing and Acoustic Emission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5456, https://doi.org/10.5194/egusphere-egu24-5456, 2024.

EGU24-6291 | Orals | GMPV7.4

SEM-EBSD reveals crystal plasticity in pyroclasts 

Jacopo Taddeucci, Corrado Cimarelli, Giacomo Pozzi, Jackie E. Kendrick, and Piergiorgio Scarlato

Electron BackScatter Diffraction can be used to measure misalignment in the lattice of crystals. Non-reversible crystal lattice deformation by migration of dislocations, i.e., crystal plasticity, has been observed and recreated under controlled experimental conditions in effusive volcanic rocks. There, crystal plasticity increases with increasing stressing of the magma, and precedes crystal failure. Here, we present the first observation of crystal plasticity in pyroclasts. We found lattice misalignment mainly in plagioclase microlites within ash- and lapilli-sized pyroclasts of mafic composition from explosive eruptions of Etna (Italy), Paricutin (Mexico), and Cumbre Vieja (Spain) volcanoes. Misalignment is found both in visibly curved and apparently undeformed crystals, its magnitude increasing with increasing aspect ratio of the crystals. Plastically deformed crystals are unevenly distributed within the pyroclasts, and often clustered. Similar to observations made in effusive rocks, crystal plasticity in pyroclasts is marked by the presence of broken crystals. But unlike the effusive case, fragments of broken crystals in pyroclasts show little or no plastic deformation, while more deformed crystals are found around zones with broken crystals. Textural evidence from natural and experimental samples show that these zones underwent localized damage by brittle fracturing. Coexisting broken and plastically deformed crystal reveal millimetre-scale patterns of stress localisation in magma during fragmentation

How to cite: Taddeucci, J., Cimarelli, C., Pozzi, G., Kendrick, J. E., and Scarlato, P.: SEM-EBSD reveals crystal plasticity in pyroclasts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6291, https://doi.org/10.5194/egusphere-egu24-6291, 2024.

EGU24-6405 | Orals | GMPV7.4

How H2O transport and trapping affect the dynamics of magmatic systems from melt generation to eruption triggering 

Catherine Annen, Roberto Weinberg, Virginie Pinel, and Alain Burgisser

H2O and other volatiles play a major role in the dynamics of magmatic systems from magma source to volcanic eruption. At the source, H2O facilitates melting and within the crust, H2O fluxing of hot rocks favours the formation and stabilisation of magma mush. H2O dissolved in melt lowers its viscosity and density and thus helps melt extraction and transport. H2O exsolution during magma transport causes crystallisation and stalling of the magma, while further exsolution in a crystallizing magma chamber increases pressure on the chamber walls and facilitates chamber failure and eruption. During the magma final journey towards the surface, formation and expansion of bubbles fragment the magma, increasing the explosivity of the volcanic eruption.

We have developed numerical simulations that model flux melting in the deep crust, and other simulations that model H2O exsolution in a growing and crystallising magma chamber in the upper crust. A parameter that is crucial in both processes is the permeability of the magma, mush, and solid rocks through which H2O is moving.

Our flux melting models show that due to complex interactions between the effect of H2O and heat, the amount of melt produced by flux melting depends on how fast H2O is transferred relative to heat. By absorbing latent heat, H2O flux melting decreases temperatures and promotes heat transfer in the melting areas. The extent of the melting region depends on the competition between the transfer of H2O, which induces melting and cooling, and the transfer of heat that smooths temperature anomalies. The amount of crustal melting also depends on permeabilities contrast. The presence of an impermeable layer above a more permeable layer increases the production of melt by trapping H2O in the permeable layer.

The ease of transfer of exsolved H2O within a crystallising magma body depends on crystal fractions. Our models of magma chambers growth and solidification show that preferential transfer of H2O through the mush that surrounds a magma chamber results in the formation of H2O layers at the top the mush and in the chamber’s roof. If the permeability of the country rocks is low, the H2O layers grow, their buoyancy increases, and the pressure eventually exceeds the yield strength of the country rock and causes fracturing. Depending on how well the H2O layers connect to the liquid magma in the chamber below, fracturing of the country rock can result either in the release of H2O only and possibly causes a bradyseismic crisis, or in the release of H2O, mush, and magma, and triggers a crystal-rich eruption.

We know from volcano degassing and from petrological data that magmas are rich in H2O. However, our knowledge of how this H2O is transferred from magmas and through the crust is limited. This knowledge is important though as our simple numerical models indicate that the modalities of H2O transport and accumulation strongly affect the dynamics of a magmatic system.

How to cite: Annen, C., Weinberg, R., Pinel, V., and Burgisser, A.: How H2O transport and trapping affect the dynamics of magmatic systems from melt generation to eruption triggering, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6405, https://doi.org/10.5194/egusphere-egu24-6405, 2024.

We use a one-dimensional numerical model to investigate how the presence of a volatile phase such as water impacts the creation and dynamics of a magma reservoir in the mid- to lower crust. We assume that the reservoir is created and sustained by the repeated intrusion of mantle-derived basalt sills containing a few wt% volatiles. Our numerical model solves the equations governing heat transfer by conduction and advection; two- and three-phase flow of the solid, melt and volatile phases assuming porous flow and compaction at low melt fraction and hindered settling at high melt fraction; and handles phase exchange using a two-component (SiO2 and volatile) chemical model fitted to experimental melting data.  The solidus and liquidus temperatures are functions of bulk SiO2 content and melt volatile content. The volatile exchange between solid and melt phases is modelled using a partition coefficient and the maximum volatile content of the solid phase is capped based on mineralogical data. The melt phase has a maximum volatile saturation above which a free volatile phase is formed. There is no direct transfer of volatiles from the solid to the volatile phase.

We find that the highly non-linear coupling between melt volatile content and the solidus and liquidus temperatures, flow of melt and (when present) volatile phases, and the exchange of latent heat, gives rise to complex emergent behaviour.  We do not observe a simple, upwards propagating volatile front below which melt is always present in a stable mush column as has been proposed in some previous studies.  Rather, we observe the formation of transient, high melt fraction, evolved and volatile-rich layers interspersed with refractory and volatile-poor mush.  The high melt fraction layers can propagate upwards, merge and split.  The layers are typically thin and likely below geophysical resolution.  The dynamics of mush reservoir growth are strongly influenced by the fertility of the overlying crust: if the crust can melt in response to the addition of heat and volatiles, then the top of the reservoir migrates upwards until it reaches mid-crust depth, creating a reservoir that spans the lower- to mid-crust and hosts numerous melt-rich layers.  Our results so far suggest a highly dynamic magmatic system characterized by significant melt fraction variations in time and space.  Much of this dynamic complexity is lost in geophysical images that are interpreted to suggest reservoirs have low and uniform melt fraction.

How to cite: Hu, H., Jackson, M., and Booth, C.: Effects of a volatile phase on the Creation and Dynamics of Lower Crustal Magma Reservoirs: A Three-Phase Numerical Model Study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6455, https://doi.org/10.5194/egusphere-egu24-6455, 2024.

EGU24-6616 | Orals | GMPV7.4

Why not drill into magma to understand the “dynamics and timescales in magmatic reservoirs”? 

John Eichelberger, Amel Barich, Bjorn Gudmundsson, Yan Lavallee, John Ludden, Bjarni Palsson, Paolo Papale, and Freysteinn Sigmundsson

How can we not afford to scientifically probe magma? Fifteen years of accidental drilling encounters with magma have shown that it can be done safely with recovery of magmatic and partial melt samples quenched in situ. More could be gained if preceded by thorough scientific preparation and followed by long-term monitoring. Through the panoply of instruments now available, we can measure temperature, pressure, strain, heat and mass transport and changes over time. In 2009, the Iceland Deep Drilling Program well #1 reached rhyolitic magma at 2100 m depth under Krafla Caldera. The project was exemplary in sharing provocative results, but only hints at what is possible. Equilibrium temperatures were estimated by traditional petrologic techniques to be 850 – 1100 C. Pressure estimates range from 40 – 90 MPa with both extremes seemingly problematic, because for the first time we know the depth of a magma body to 4 significant figures. The lowest value is below lithostatic and the highest could be inherited from deeper levels. Now it appears that the lower pressure is what magma “feels”. But without drilling, would traditional estimates be good enough? Magma is somewhere between 1500 – 4000 m depth and with temperature corresponding to some type of magma? Actually, we would not even know that shallow magma is there but now in hindsight we see it geophysically. Ground-truth testing is how methodologies are improved. Our situation is like speculating about the nature of the Moon without sampling it. The cost of probing Earth’s magma is high and the probability of success uncertain, but far less so on either count than for extraterrestrial exploration. On Earth we are more restrained by self-imposed limits than by our technical capabilities. Besides understanding the differentiation of our planet, we have two compelling reasons for bold exploration: 1) We need the baseload, magma resource with its far higher temperature, energy density, and more extensive thermal fracturing than conventional geothermal; 2) We need to raise the level of reliability of eruption forecasts by testing our magma-dynamic models directly, thereby saving countless lives. As with other endeavors that are expensive for a single country to undertake but that benefit all humankind, a way forward is through an international infrastructure, where teams of scientists can conduct experiments with magma and superhot fluids. This is analogous to particle accelerators and the complement to outer space travel: inner space.  The Krafla Magma Testbed is a much-needed step and an opportunity for all planetary, magma, volcano, and hydrothermal scientists to test their methods and ideas. KMT will drill a doublet of wells to magma for long-term monitoring and experimentation, respectively. The project, now organized as a legal entity within the Iceland Geothermal Research Cluster (GEORG), in partnership with the National Power Company of Iceland (Landsvirkjun), Iceland Energy GeoSurvey (ISOR), and a multinational team of scientists and engineers, under the aegis of the International Continental Scientific Drilling Program (ICDP), is ready. Magma could have been intentionally explored before. It is time to ask, “Why not now?”

How to cite: Eichelberger, J., Barich, A., Gudmundsson, B., Lavallee, Y., Ludden, J., Palsson, B., Papale, P., and Sigmundsson, F.: Why not drill into magma to understand the “dynamics and timescales in magmatic reservoirs”?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6616, https://doi.org/10.5194/egusphere-egu24-6616, 2024.

EGU24-6695 | ECS | Posters on site | GMPV7.4

Petrology and Geochemistry of the Kula Volcanic Field, Western Turkey 

Megan Watfa, Lorna Anguilano, Philip Collins, Francesca Forni, and Marilena Moroni

Small-scale monogenetic volcanic systems are the most widespread type of volcanism we experience on Earth and occur in a range of different tectonic settings, including intraplate, extensional, and subduction-related plate tectonics. Formed by a single surface eruption where small batches of magma erupt effusively and explosively, these features present a range of characteristics, including eruption frequency, volume, and duration, which can be linked to local and regional tectonic regimes. This volcanism is represented by tens to hundreds of associated volcanic vents where lava can unexpectedly penetrate the crust, with a new vent forming in an unknown location. Monogenetic volcanic fields (MVFs) are incredibly important to study, as each vent represents the pathway for magma to the upper mantle. These structures however are incredibly understudied and poorly constrained in terms of volcanic eruptive histories, and questions about the origin, longevity, and spatial distribution of vents are subject to uncertainty.

A wonderful example of where this can be investigated is the Kula Volcanic Province (KVP) in Anatolia, Western Turkey, exhibiting three periods of Quaternary basaltic volcanism between 2 Ma and 10 Ka. The three periods, namely the Burgaz, Elekçitepe, and DivlitTepe have been identified as silica-undersaturated alkaline volcanism exhibited as cinder cones, parasitic cones, spatter cones, lava flows, lava tunnels and maars. Turkey is situated in one of the most seismically active regions of the world, with Western Turkey one of the most spectacular regions of widespread active continental extension. The Kula volcanics are Na-dominant in character whereas other older volcanic rocks of Western Anatolia are generally definitive K-dominant rocks, representing a unique example of volcanism, and a rationale to investigate the significant geochemical signatures.

Within this study, we present new petrological and geochemical data (XRF, XRD, SEM) between magma products from the different eruptive periods, and provide an inclusive textural, chemical, and elemental investigation evaluating magma chamber dynamics, as well as exploring the temporal and spatial variations of the 80+ volcanic cones.  In addition to this, we plan to further use core and rim analysis of the main mineral phases to identify compositional variations of major (EPMA) and trace (LA-ICP-MS) elements which will be used to develop geochemical diagrams showing the relationships between specific elements and infer any geochemical processes that may have occurred.

This work aims to contribute to understanding future volcanic scenarios for intraplate volcanism which can be applied to other comparable tectonic environments and is a fundamental rationale for understanding magma chamber processes such as magma generation, magma evolution, crystallisation pathway, and likely tectonic environment.

How to cite: Watfa, M., Anguilano, L., Collins, P., Forni, F., and Moroni, M.: Petrology and Geochemistry of the Kula Volcanic Field, Western Turkey, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6695, https://doi.org/10.5194/egusphere-egu24-6695, 2024.

EGU24-7627 | ECS | Posters on site | GMPV7.4

In situ nanoscale insights on magma viscosity and explosive eruptions 

Pedro Valdivia, Alessio Zandonà, Jessica Löschmann, Dmitry Bondar, Cécile Genevois, Aurélien Canizarès, Nobuyoshi Miyajima, Alexander Kurnosov, Tiziana Boffa Ballaran, Fabrizio Di Fiore, Alessandro Vona, Claudia Romano, Mathieu Allix, Joachim Deubener, and Danilo Di Genova

Explosive volcanic eruptions pose significant threats to populated areas by injecting substantial amounts of gas and ash into the atmosphere. These events, resulting from magma fragmentation, are triggered by factors such as limited bubble expansion and relatively high strain rates during ascent, predominantly controlled by chemical composition. Less evolved melts, like andesites and basalts, present challenges in achieving fragmentation conditions due to their inherently low viscosities. Despite this, explosive activity of these magmas occurs. Recent studies highlight the role of Fe-Ti-oxide nanocrystals (nanolites) in increasing viscosity during laboratory measurements. Interestingly, nanolites have been found in natural volcanic products erupted during explosive events. However, the mechanisms and the extent to which nanolite formation affects magma viscosity remain a subject of ongoing debate. Here, we present the first in situ imaging observation of nanolite formation in andesitic melt and thoroughly quantify the impact on melt viscosity. To establish a robust point of comparison, we develop multiple novel viscosity models exclusively using viscosity data from nanolite-free samples. Our findings reveal that above the glass transition temperature, iron oxidation and nanocrystallization readily occur, inducing structural heterogeneities in the nanoscale. The precipitation of magnetite nanocrystals induces a heterogeneous distribution of elements in the residual melt, generating a relatively SiO2-enriched matrix and Al-enriched shells around the nanolites. This phenomenon results in a substantial, up to 30-fold, surge in magma viscosity at eruptive temperatures. This noteworthy increase in magma viscosity has profound implications for the physical properties of andesitic plugs and domes and could play a critical role in driving the magma towards fragmentation during eruption.

How to cite: Valdivia, P., Zandonà, A., Löschmann, J., Bondar, D., Genevois, C., Canizarès, A., Miyajima, N., Kurnosov, A., Boffa Ballaran, T., Di Fiore, F., Vona, A., Romano, C., Allix, M., Deubener, J., and Di Genova, D.: In situ nanoscale insights on magma viscosity and explosive eruptions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7627, https://doi.org/10.5194/egusphere-egu24-7627, 2024.

EGU24-8840 | Posters on site | GMPV7.4

The February-March 2021 lava fountains events of Mt. Etna South-East crater: insights from clinopyroxenes.  

Chiara Maria Petrone, Rosa Anna Corsaro, and Buret Yannick

Mt. Etna is the most active volcano in Europe with four active vents in the summit area. The South-East Crater (SEC) is the most active crater of the last 20 years and is characterised by episodic eruptions, i.e. sequences of paroxysmal lava fountains with rather variable frequency and duration from a few weeks to months. Between December 2020 and February 2022, the SEC produced over 60 paroxysmal events divided into a first phase (December 2020 – April 2021) and a second phase (May 2021 - February 2022).

We investigated textural and chemical characteristics of the clinopyroxenes population to constrain frequency of magma recharge episodes and eruption triggering mechanisms of 6 paroxysms representative of the first phase, from February 16 to March 10 2021, including the February 28 paroxysm which erupted the most primitive magma.  Clinopyroxenes show frequent sector zoning superimposed on complex concentric zoning showing two main compositional domains: 1) augitic composition (Mg# 68-75) which mostly characterises rims and is less frequent in cores and mantles; 2) diopsidic composition (Mg# 74-80) mainly found in cores and less abundant in mantle and rims. Barometric estimates using the new GAIA deep learning-based thermobarometry (Chicchi et al., 2022 EPSL) indicate a shallow reservoir (0.4-1.0 ± 0.3 kbar) for the augitic domain and a deeper reservoir (1.7-2.7 ± 0.5 kbar) for the diopsidic domain. Fe-Mg diffusion timescales point to the occurrence of multiple episodes of mafic recharges starting in December 2020 and up to a few days prior eruption in agreement with monitoring data.

How to cite: Petrone, C. M., Corsaro, R. A., and Yannick, B.: The February-March 2021 lava fountains events of Mt. Etna South-East crater: insights from clinopyroxenes. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8840, https://doi.org/10.5194/egusphere-egu24-8840, 2024.

EGU24-10251 | ECS | Posters on site | GMPV7.4

Multiparametric exploration of active magma degassing at Mt. Etna in 2023 

Clothilde Biensan, Jacopo Taddeucci, Tullio Ricci, Elisabetta Del Bello, Piergiorgio Scarlato, and Danilo Palladino

Active magma degassing is the release of slightly over-pressurized gas pockets from volcanic vents. This activity can shed light on the geometry of the shallow plumbing system of volcanoes and its internal dynamics. During a summer 2023 field campaign, we conducted comprehensive recordings, including thermal infrared, high-speed, and high-resolution video, as well as broadband microphone signals, capturing ten consecutive days of active degassing events at the Bocca Nuova crater of Mt. Etna. Two distinct vents exhibited notable degassing activity. The first, henceforth referred to as 'Sboffer,' was a crater characterized by the emission of loud, low-frequency sounds accompanying each degassing event (hence the name). The second vent, smaller than the first one and designated as 'Ringer,' took the form of a circular pit on the Bocca Nuova crater floor, emitting volcanic vortex rings—reminiscent of smoke rings (hence the name)—during events. We focused our analysis on the thermal data, characterizing emissions from both vents by examining brightness temperature anomalies along horizontal measurement lines in the thermal video recordings. Both vents exhibited a bimodal distribution in the intensity and duration of events. Specifically, Sboffer produced larger events with a mean amplitude of 100-160°C and a recurrence time of approximately 500 seconds, along with smaller events with amplitudes of 20-24°C occurring every 200-400 seconds. Ringer, on the other hand, featured larger events with amplitudes of 70-100°C and smaller events with amplitudes of 20-23°C, occurring at much higher frequencies of every 4 and 1.5 seconds, respectively. The maximum temperature recorded during the larger events reached nearly 600°C for Ringer and 500°C for Sboffer. The exit velocities for large events were measured at 15 m/s for Sboffer and 10 m/s for Ringer. Remarkably, all parameters at both vents remained consistently stable throughout the ten-day observation period. Preliminary investigations were conducted to explore potential correlations between the acoustic signal and thermal data. The aim was to ascertain the depth of the explosive events and examine potential correlations with temperature variations and the intensity of the explosions.

How to cite: Biensan, C., Taddeucci, J., Ricci, T., Del Bello, E., Scarlato, P., and Palladino, D.: Multiparametric exploration of active magma degassing at Mt. Etna in 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10251, https://doi.org/10.5194/egusphere-egu24-10251, 2024.

EGU24-10731 | ECS | Orals | GMPV7.4

Petrographic and geochemical investigation of magma reservoir processes at Rabaul Caldera, Papua New Guinea 

Melina Hoehn, Brendan McCormick Kilbride, and Margaret Hartley

Rabaul is a large caldera system located at the northeastern tip of the island of New Britain, Papua New Guinea. Historically, it has been the most active volcano in Papua New Guinea. Rabaul is capable of large volume, high intensity caldera-forming eruptions (high-risk, low-probability events occurring every ca. 2 ka, most recently the Rabaul Pyroclastics event ca. 1400 years ago) and lower intensity but more frequent intra caldera eruptions. All eruptions at Rabaul pose a significant risk to nearby populations and settlements [1,2].

Rabaul’s volcanic rocks vary in composition from basaltic andesite to rhyolite and mostly lie on a common liquid line of descent, controlled by fractional crystallization under reducing conditions [1,2,3,4]. Magma mixing and mingling are common, evidenced by basaltic enclaves and mafic minerals in andesitic and dacitic eruption products [1,2,4]. These enclaves signify regular mafic recharge of the main dacitic reservoir, which primes the system for eruptions [4]. Seismic tomography imaging suggests the presence of an extensive, tabular magma body at a depth of 3-6 km with a volume of about 15-150 km3 [5,6].

The main goal of this study is to determine how the petrology and geochemistry vary between magmatic products erupted from different intervals in the caldera cycle of Rabaul volcano. In addition, we aim to get a better understanding of the primitive magmas that feed and sustain volcanism at the Rabaul Caldera Complex. Furthermore, we identify the key magma chamber processes influencing mineral chemistry and texture.

Here, we present EPMA mineral analysis and thermobarometry model outputs for products of the 1937, 1994 and 2014 eruptions as well as for the most mafic eruption products known, the Kombiu basalts. Our thermobarometry data complement existing geophysical observations of the structure of Rabaul’s magma plumbing system. Furthermore, we present SEM imagery to reveal how mineral textures (zoning, resorption, grain size, grain boundaries) in samples from different eruptions at Rabaul reflect magma chamber processes such as mafic recharge, magma mixing and crystallisation.

 

References: [1] Patia H et al. (2017) J Volcanol Geotherm Res 345:200-217; [2] Fabbro G et al. (2020) J Volcanol Geotherm Res 393:106810; [3] Wood CP et al. (1995) J Volcanol Geotherm Res 69:285-302; [4] Bouvet de Maisonneuve C et al. (2016) GSL; [5] Finlayson et al. (2003) J Volcanol Geotherm Res 124: 153-171; [6] Bai and Greenhalgh (2005) Phys. Earth Planet. Inter. 151: 259-275

How to cite: Hoehn, M., McCormick Kilbride, B., and Hartley, M.: Petrographic and geochemical investigation of magma reservoir processes at Rabaul Caldera, Papua New Guinea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10731, https://doi.org/10.5194/egusphere-egu24-10731, 2024.

EGU24-11135 | Orals | GMPV7.4

Pre-eruptive magmatic reservoir conditions controlling explosivity of a trachytic Plinian eruption: case for the Rungwe Pumice (Tanzania) 

Lorenzo Cappelli, Paul A Wallace, Evelyne Mbede, Shimba Kwelwa, Edista Abdallah, and Karen Fontijn

The eruptive style and explosivity of volcanic eruptions primarily depend on conduit dynamics (e.g., ascent rate and degassing efficiency) and the rheological behaviour of the pre-eruptive magma, which is controlled by its composition and conditions within the reservoir. In the case of highly alkaline magmas (i.e., agpaitic index > 1), the depolymerisation of silica bonds exerted by alkaline elements promotes a relatively low-viscosity rheological response and therefore theoretically less explosive eruptive behaviour, even for silica-rich magmas. However, several well-studied eruptions show that peralkaline magmas, like trachyte and phonolite, can also experience highly explosive Plinian events, suggesting other parameters might influence the eruption style. In the East African Rift, several such volcanoes with peralkaline magma compositions have erupted both explosively and effusively in the past. We investigated the pre-eruptive magmatic system of the Plinian eruption that produced the Rungwe Pumice (RP) deposit in southern Tanzania. The type section of the RP consists of a ~2.5 m thick fall deposit of peralkaline trachytic/phonolitic pumices. Syn-eruptive volatile exsolution is a crucial parameter controlling the eruptive style and is related to the volatile budget within the reservoir. Therefore, water concentrations in haüyne-hosted melt inclusions (MIs) were characterised using transmitted Fourier-transformed infrared spectroscopy. Preliminary results indicate substantial water concentrations within the reservoir (i.e., 2.60-5.59 wt.%) while the water retained by the glassy matrix of pumices reveals that the magma was almost entirely degassed during ascent. The modelled evolution of magmatic composition within the reservoir suggests closed conduit fractional crystallisation (~80% fractionation) of a parental mafic magma to generate the RP trachyte/phonolite within a compositionally homogeneous magmatic reservoir. Finally, by applying petrological models, we estimated a MI entrapping temperature of ~1147 ± 92 K and a minimum lithostatic pressure ranging from ~28 to 184 MPa (~1-7 km depth).

How to cite: Cappelli, L., Wallace, P. A., Mbede, E., Kwelwa, S., Abdallah, E., and Fontijn, K.: Pre-eruptive magmatic reservoir conditions controlling explosivity of a trachytic Plinian eruption: case for the Rungwe Pumice (Tanzania), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11135, https://doi.org/10.5194/egusphere-egu24-11135, 2024.

The preservation of volcanic and plutonic records holds the potential to improve our comprehension of plumbing systems. It is widely accepted that numerous magmatic complexes are fed by crystal-rich magma ponding at mid to shallow crustal depth, which is periodically remobilized by the intrusion of hotter melts over extended periods. However, these mechanisms are rarely recorded in plutons. The Dolomites (Southern Alps; Italy) host large volumes of Middle Triassic volcanic and plutonic outcrops, characterized by an excellent state of preservation. This condition enables us to deeply investigate the plumbing system dynamics and connect the effusive and intrusive components of the Middle-Triassic magmatism in the Southalpine domain. In this study, a detailed textural and compositional investigation of clinopyroxene crystals in shallow crustal pyroxenites and gabbros has been done to link plutonic features to the already investigated volcanic counterparts (Nardini et al. 2022). Augitic clinopyroxene is the dominant mineral phase, with euhedral to subhedral crystals up to cm-sized dimensions. Its compositions show Mg# [MgO/(MgO+FeOtot) mol%] from 62 to 75 coupled with low Cr2O3 concentration (< 0.1 wt.%) and 0.5-1 wt.% of TiO2. The crystals occasionally show step zoning patterns towards diopsidic domains having high-Mg# (80-90), higher Cr2O3 and lower TiO2 (both from 0.1 to 0.5 wt.%) organised as outer rims, intermediate bands or as resorbed cores. These preliminary data confirm what recorded by the volcanic counterparts, suggesting a periodical mixing between trachyandesitic and trachybasaltic melts (see Nardini et al. 2022). The remarkable preservation of zoning patterns in the plutonic rocks, coupled with the consistency of clinopyroxene composition and zoning in alignment with the lavas and dykes, provides a powerful volcano-plutonic link. The analyses of exposed plutonic rocks, chemically associated with the erupted materials, provide concrete evidence of the magmatic processes that are inferred through petrogenetic modelling in volcanic rocks, with the potential to deepen our understanding of the plumbing system dynamics.


References
Nardini, N., Casetta, F., Ickert, R. B., Mark, D. F., Ntaflos, T., Zanetti, A., & Coltorti, M. (2022). From the Middle Triassic Cima Pape complex (Dolomites; Southern Alps) to the feeding systems beneath active volcanoes: Clues from clinopyroxene textural and compositional zoning. Journal of Volcanology and Geothermal Research, 422, 107459.

How to cite: Nardini, N., Casetta, F., Coltorti, M., and Ntaflos, T.: Shedding light on the volcano-plutonic link: evidence of magma mixing dynamics in the shallow crustal plutonic rocks from the Dolomites (Southern Alps; Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11166, https://doi.org/10.5194/egusphere-egu24-11166, 2024.

EGU24-11281 | ECS | Orals | GMPV7.4

Source depth of basaltic andesite magma beneath La Soufrière, St Vincent. 

Beitris Morrison-Evans, Elena Melekhova, and Jonathan Blundy

Many volcanoes erupt a limited compositional range of magmas over their lifetime. The composition of these erupted magmas is thought to be buffered by the crystal-rich mush from which melts are sourced (Blundy, 2022). Identifying the origin of erupted magmas helps us to constrain possible locations of melt accumulation in the mush and improve our interpretation of geophysical signals at restless volcanoes.

La Soufrière volcano, St Vincent (Eastern Caribbean), has throughout its lifetime produced predominantly basaltic andesite magmas, including most recently in 2020-21. We explore the origin and phase relations of these erupted magmas by performing a series of high-pressure, high-temperature experiments. Melt extracted from a mush will be multiply-saturated on its liquidus with the mush mineral assemblage at the P-T-fO2-XH2O conditions at the time of segregation. In a system with relatively low thermodynamic variance, for example, five or six independent chemical components (as determined by principal component analysis), a large number of coexisting mineral phases (e.g. plag+cpx+amph+oxides) and a well-constrained fO2, multiple saturation can be reduced to an invariant point on the liquidus of the melt in P-T-H2O space. The approach of finding liquidus multiple saturation for igneous rocks offers a novel magma source thermobarometer and hygrometer.

Equilibrium high-pressure, high-temperature experiments were performed at 3-8 kbar and 980-1200ºC, fO2 ≈ Ni-NiO buffer, with initial H2O contents of 2-10 wt%. Plagioclase, clinopyroxene and magnetite are found to be ubiquitous in the melt source region. Amphibole is a peritectic phase and forms on the rim of clinopyroxene, with decreasing temperature, in experiments with high water contents. The peritectic reaction involving amphibole is also observed in St Vincent xenoliths (Brown, 2023). Orthopyroxene is stable at high pressures (8 kbar) and low water contents (≤ 6wt% H2O), with its stability field decreasing with pressure. Five-phase multiple saturation at the liquidus (melt fraction ≥85%) is found for initial H2O contents of 7-8 wt%, at 6 kbar pressure (~22 km depth) and temperatures of 1030-1050ºC. The saturating assemblage is a hornblende-gabbro (cpx+plag+amph+Fe-Ti oxides), consistent with the mineralogy of plutonic xenoliths from historic eruptions of St Vincent (Tollan et al., 2012; Fedele et al., 2021). Mineral compositions in these multiply-saturated runs (e.g. very calcic plagioclase An75-85) are similar to those in the xenoliths. Temperatures agree with mineral geothermometry estimates of the 2020-21 eruption (Weber et al., 2023), suggesting little cooling of the magma during ascent from its source region. Seismicity prior to the 2020-21 eruption is also consistent with mid-crustal source depths (Joseph et al., 2022). Magmas sourced from similar depths can account for the limited compositional diversity of La Soufrière over its volcanic history (Fedele et al., 2021).

 

References

Brown, JR. (2023) Doctoral dissertation, Durham University. 

Blundy, J. (2022) Journal of Petrology63(7), egac054.

Fedele et al. (2021) Lithos, 392, p.106150

Joseph et al. (2022) Nature Communications13(1), p.4129.

Tollan et al. (2012) Contributions to Mineralogy and Petrology163, pp.189-208.

Weber et al. (2023) Geological Society, London, Special Publications, 539(1), pp.SP539-2022.

How to cite: Morrison-Evans, B., Melekhova, E., and Blundy, J.: Source depth of basaltic andesite magma beneath La Soufrière, St Vincent., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11281, https://doi.org/10.5194/egusphere-egu24-11281, 2024.

EGU24-11586 | ECS | Posters on site | GMPV7.4

Petrological monitoring of persistently active basaltic volcanoes: the case study of Stromboli (Aeolian Islands, Southern Italy) 

Beatrice Schiavon, Chiara Maria Petrone, Francesca Forni, Alessio Pontesilli, Elisabetta Del Bello, Piergiorgio Scarlato, Manuela Nazzari, Massimo Tiepolo, and Silvio Mollo

Investigating the dynamics and timescales of magmatic processes in active volcanoes is crucial for understanding explosive eruptions and assessing volcanic hazards. In this context, we are currently conducting a petrological survey of the Stromboli volcano (Aeolian Islands, Southern Italy), whose persistent activity is characterized by periodic and mildly explosive “Strombolian” eruptions, alternating with episodic lava effusions and more violent eruptive events, namely major explosions and paroxysms. The plumbing system is characterized by a vertically-extended mush column in which the shallow magmatic reservoir (highly porphyritic or Hp-magma) is continuously refilled with mafic recharges (low porphyritic or Lp-magma) rising from depth. During the paroxysmal events, sustained injections of Lp-magmas produce ample and continuous H2O-rich gas phases that are released with great energy through the vent, together with ash, scoriaceous spatters, bombs and lithics traveling over long distances. With the final scope of deciphering mutual relationships between Hp- and Lp-magmas, as well as magma-mush interplay within the shallow plumbing system, we present in situ microchemical analyses of plagioclase phenocrysts from nineteen scoria clasts ejected during mild to violent explosions at Stromboli over a timespan of ~18 years, from 2003 to 2021. Major and trace element compositions, as well as Sr-isotopic data have been integrated with thermometric modeling and Mg-in-plagioclase diffusion chronometry to constrain the physicochemical changes within the plumbing system and the timescales of magmatic processes. Through this approach, a new eruptive cycle at Stromboli volcano has been identified, where more energetic open-conduit dynamics are associated with an increased intensity and frequency of eruptions due to mush disruption by sustained injections of mafic recharge magmas from depth.

How to cite: Schiavon, B., Petrone, C. M., Forni, F., Pontesilli, A., Del Bello, E., Scarlato, P., Nazzari, M., Tiepolo, M., and Mollo, S.: Petrological monitoring of persistently active basaltic volcanoes: the case study of Stromboli (Aeolian Islands, Southern Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11586, https://doi.org/10.5194/egusphere-egu24-11586, 2024.

EGU24-12270 | Posters on site | GMPV7.4

CatVolc: A new database of geochemical and geochronological data of volcanic-related materials from the Catalan Volcanic Zone (Spain) 

Adelina Geyer, Martín Miranda-Muruzábal, Meritxell Aulinas, Helena Albert, Miquel Vilà, Fus Micheo, Xavier Bolós, Dario Pedrazzi, Guillem Gisbert, and Llorenç Planagumà

The Catalan Volcanic Zone (CVZ) in northeastern Spain constitutes an intraplate alkaline volcanic region linked to the opening of the Western Mediterranean and the development of the European Rift System. Volcanic activity in the CVZ started in the L’Empordà area (ca. > 12 - 8 Ma), extended to La Selva (7.9 - 1.7 Ma), and finally migrated to the Garrotxa Volcanic Field (< 0.7 - 0.01Ma). Despite ongoing scientific interest in the CVZ dating back to the early 19th century, certain aspects remain insufficiently defined. These include a comprehensive understanding of the spatial and temporal evolution of the magma plumbing system(s) and ascent mechanisms, as well as the chronology of volcanism across the CVZ. Unraveling these unresolved questions requires geochemical, petrological, and geochronological data, which, in the case of the CVZ, are scattered and have never been integrated or analysed within a unified framework. This study introduces the CatVolc (Catalan Volcanism) database, consolidating existing geochemical and geochronological data of volcanic-related materials within the CVZ. The current version of the database incorporates geochemical analyses from 405 rock samples (296 juvenile magmatic rocks -including lavas and pyroclasts- and 109 xenoliths), and radiometric/thermoluminescence dating data from 57 rocks (55 volcanogenic and two dykes), 4 paleosols samples developed between volcanic deposits and 1 sample from sediments. Each entry in the CatVolc database provides general information about the sampling site, sample lithology, whole-rock analyses (including major and trace elements), isotopic ratios, mineral chemistry, and radiometric/thermoluminescence dating details, if available. An initial analysis of the information contained in the CatVolc database highlights the critical limitations of the current state of knowledge and allows suggesting potential future directions for volcanic-driven investigations in the CVZ. Furthermore, the outcomes affirm the CatVolc database as an essential tool for understanding the spatial and temporal evolution of magmatic systems and volcanic activity in the CVZ, particularly within the Garrotxa Volcanic Field. This validation is crucial for advancing the assessment of volcanic hazards in the region and gaining a comprehensive understanding of future volcanic activity.

This work has been developed under the financial support of the Institut Cartogràfic i Geològic de Catalunya (ICGC), the Parc Natural de la Zona Volcànica de La Garrotxa (PNZVG), the Fundación General CSIC's ComFuturo programme and the Marie Skłodowska-Curie grant agreement No. 101034263, the collaboration grant 2021 COLAB 00367 funded by the MEFP,  and the grant PID2022-139047NA-I00 funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe”.

How to cite: Geyer, A., Miranda-Muruzábal, M., Aulinas, M., Albert, H., Vilà, M., Micheo, F., Bolós, X., Pedrazzi, D., Gisbert, G., and Planagumà, L.: CatVolc: A new database of geochemical and geochronological data of volcanic-related materials from the Catalan Volcanic Zone (Spain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12270, https://doi.org/10.5194/egusphere-egu24-12270, 2024.

EGU24-12812 | ECS | Posters on site | GMPV7.4

Magma differentiation in dynamic mush domains from the perspective of multivariate statistics: open- vs closed-system evolution 

Alessio Pontesilli, Fabrizio Di Fiore, Piergiorgio Scarlato, Ben Ellis, Elisabetta Del Bello, Daniele Andronico, Jacopo Taddeucci, Marco Brenna, Manuela Nazzari, Olivier Bachmann, and Silvio Mollo

Open-conduit conditions characterize several of the most hazardous and active volcanic systems of basaltic composition worldwide, persistently refilled by magmatic inputs. Eruptive products with similar bulk compositions, chemically buffered by continual mafic inputs, exhibit nevertheless heterogeneous glass compositions in response to variable magma mixing, crystallization, and differentiation processes within different parts of the plumbing system. Here we document how multivariate statistics and magma differentiation modeling based on a large data set of glass compositions can be combined to constrain magma differentiation and plumbing system dynamics. Major and trace elements of matrix glasses erupted at Stromboli volcano (Italy) over the last twenty years provide a benchmark against which to test our integrated petrological approach. Principal component analysis, K-means cluster analysis, and kernel density estimation reveal that trace elements define a multivariate space whose eigenvectors are more readily interpretable in terms of petrological processes than major elements, leading to improved clustering solutions. Comparison between open- and closed-system differentiation models outlines that steady state magma compositions at constantly replenished and erupting magmatic systems approximate simple fractional crystallization trends, due to short magma residence times. Open-system magma dynamics imply lower crystallinities pervade the magmatic storage than those associated with closed-system scenarios, allowing efficient crystal-melt separation toward the top of the reservoir, where eruptible melts continuously supply the ordinary activity at the volcano. Conversely, a mush-like environment constitutes the bottom of the reservoir, in which poorly evolved magmas result from mixing events between mush residual melts and primitive magmas injected from deeper crustal levels. 

How to cite: Pontesilli, A., Di Fiore, F., Scarlato, P., Ellis, B., Del Bello, E., Andronico, D., Taddeucci, J., Brenna, M., Nazzari, M., Bachmann, O., and Mollo, S.: Magma differentiation in dynamic mush domains from the perspective of multivariate statistics: open- vs closed-system evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12812, https://doi.org/10.5194/egusphere-egu24-12812, 2024.

Tenerife island (Canary Islands, Spain), home to nearly a million inhabitants and attracting over 5 million tourists annually, hosts one of Europe's potentially most hazardous volcanic systems. Current volcanic activity on the island is primarily located in its central region comprising the Teide-Pico Viejo volcanic complex, and extends along the Santiago del Teide and Dorsal ridges towards the NW and NE, respectively. Understanding the volcanic stratigraphy, petrology, and geochemistry of the different eruptions within the central complex and their correlation with the rift systems is crucial to comprehend how this complex volcanic system will behave in the future, thereby improving hazard assessment for the island.

In this study, we provide a comprehensive review of the geochemistry of eruptive products associated with events that occurred in the area over the last 180ka, following the El Abrigo eruption, the island's latest caldera-forming event. Special emphasis is given to Holocene eruptions sourced at the Teide-Pico Viejo volcanic complex and the two adjacent rifts. To facilitate this, we have constructed the GeoTeRi database, which includes an exhaustive compilation of whole-rock major and trace elements analyses, along with isotopic data available in the literature (over 49 consulted references). Additionally, a review of the chronostratigraphy of the eruptions included in the database was conducted, drawing on published volcanostratigraphic maps and/or existing radiometric data.

The GeoTeRi database currently includes information from 651 rock samples, comprising over 500 major and trace elements analyses, and 176 isotopic analyses. This database aims to serve as a tool for reconstructing the geochemical evolution of the active volcanic system on the island of Tenerife and it will provide a starting point for future studies. Additionally, a detailed statistical analysis of this database is planned to evaluate its robustness, the representativeness of the analysed samples, and possible knowledge gaps in the understanding of the active system.

This research was partially funded by E.G., grant EVE (DG ECHO H2020 Ref. 826292) and the Intramural CSIC grant MAPCAN (Ref. 202130E083). OD was supported by an FPU grant (FPU18/02572) and a complementary mobility grant (EST19/00297) from the Ministry of Universities of Spain.



How to cite: Dorado, O., Geyer, A., and Marti, J.: GeoTeRi: A new geochemical database of post-caldera (< 180 ka) eruptions of Teide-Pico Viejo central complex and adjacent rift systems (Tenerife, Canary Islands), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12896, https://doi.org/10.5194/egusphere-egu24-12896, 2024.

To address the nature of mantle-derived melts and submarine geohazards of the Japan Sea, we present new in-situ compositions for clinopyroxene (trace elements) and plagioclase (trace elements and Sr isotopes) from Sites 794 and 797 tholeiitic basalts. Plagioclase and clinopyroxene from Upper Site 797 and Lower Site 794 are characterized by relatively lower incompatible elements relative to those of Lower Site 797 and Upper Site 794. Lower Site 794 bulk-rocks and minerals have slight enrichment in Sr isotope compositions but depletion in trace element ratios. The observed zoning textures together with in-situ geochemical and isotopic diversity within individual plagioclase indicate fractional crystallization and the contribution of heterogeneous melt. In-situ Sr isotopic disequilibria between plagioclase phenocrysts and groundmass likely have important ramifications for the enriched compositional heterogeneity with the significant influence of recycled subduction-related oceanic fluid/sediment beneath the Japan Sea. The initial extension of the Japan Sea was relatively slow, resulting in the slow replenishment of depleted MORB-type melts derived from the upper mantle, and the extensive mixing of the migrating depleted melt with the preformed surrounding enriched melts. It thus forms the slight depletion of the highly incompatible elements but the enriched invariability of the isotopic compositions of Lower Site 794 bulk- rocks and minerals due to the relatively long half-life of the radiogenic elements. In summary, the expansion velocity of the Japan Sea varies from slow to rapid, which leads to time-progressive variations in the mineral and bulk-rock compositions beneath the Japan Sea. The maximum seismic depth of the earthquake decreases with the increase of the expansion velocity of the Japan Sea.

How to cite: Chen, J., Chen, S., and Cheng, Q.: The tectono-magmatic formation and submarine geohazards of the Japan Sea: Constraints from in-situ trace elements and Sr isotopes of plagioclase and clinopyroxene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13126, https://doi.org/10.5194/egusphere-egu24-13126, 2024.

EGU24-13229 | ECS | Orals | GMPV7.4

"Strombolian" explosions in Hawai'i 

Caroline Tisdale and Bruce Houghton

Eruptions labeled "Strombolian" – characterized by spaced discrete explosions that occur when gas pockets burst at the magma free-surface  – represent an endmember of basaltic volcanism, yet the term's applicability outside Stromboli volcano (Italy) itself remains controversial. The occurrence of Strombolian-like activity in diverse settings necessitates a more nuanced approach to classification and characterization. This study presents a quantitative analysis of transient short-lived (seconds to tens of seconds) mafic explosions from two eruptions: the 2011 Kamoamoa eruption of Kīlauea and the 2018 Lower East Rift Zone eruption of Kīlauea (USA, Hawai'i). Ground-based video recordings are the primary data source. Advancements in image processing allow for the efficient analysis of key eruption parameters including explosion frequencies, durations, and repose intervals, as well as 2D particle exit velocities, size distributions, and mass eruption rates and total mass per explosion. Preliminary results revealed that compared to “normal” Strombolian activity at Stromboli, discrete explosions at Kīlauea in 2011 and 2018 were often shorter lived, more closely spaced, and less intense. These findings suggest a spectrum of Strombolian-like behavior, influenced by factors such as magma composition, shallow conduit geometry, and most importantly gas behavior and flux. This diversity of activity challenges the application of the "Strombolian" label and emphasizes the need for quantitative characterization of discrete basaltic explosions outside of Stromboli.

How to cite: Tisdale, C. and Houghton, B.: "Strombolian" explosions in Hawai'i, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13229, https://doi.org/10.5194/egusphere-egu24-13229, 2024.

Inherited/xenocrystic zircons entrained in magmas offer a unique opportunity to identify cryptic magmatic episodes in the deep crust and thus to image lithospheric thickening and crustal evolution. We investigated zircon xenocrysts within igneous rocks (mostly granitoids) from the Northern Xinjiang region in the southwestern part of the Central Asian Orogenic Belt (CAOB) to evaluate their potential as a probe of crust evolution, by using the previously ignored information of our newly obtained and compiled dataset of xenocrystic/inherited zircons (e.g., U-Pb age and Hf-O isotopic data). Different ancient age distributions of these zircons and the varying U-Pb ages and heterogeneous Hf isotopes demonstrate the ancient magmatic pulses in the crust of NW CAOB. Combined with the information from detrital zircons, and through the published plate motion models, we further compare these ancient age peaks in variable time-slices, e.g., from Proterozoic to Paleozoic, to interpret the recycling and transport of continental material. This innovative approach enhances our understanding of orogenic processes, shedding light on imaging the recycling and transport of deep continental materials.

How to cite: Zhang, J., Wang, T., Tong, Y., Huang, H., and Song, P.: Combined analysis on information of xenocrystic/inherited zircons within igneous rocks of Northern Xinjiang in northwestern China: imaging the deep crustal components through time, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14289, https://doi.org/10.5194/egusphere-egu24-14289, 2024.

EGU24-15563 | ECS | Posters on site | GMPV7.4

Disequilibrium viscosity of Stromboli basalt: Implications for magma dynamics in active basaltic systems 

Fabrizio Di Fiore, Alessandro Vona, Danilo Di Genova, Alessio Pontesilli, Laura Calabrò, Silvio Mollo, Jacopo Taddeucci, Claudia Romano, and Piergiorgio Scarlato

Magma ascending through Earth's crust undergoes complex chemical and physical changes that may induce crystallization, a solidification process that deviates from the thermodynamic state of equilibrium. The diverse cooling and deformative regimes suffered by magmas heavily influence crystallization rates, solidification timescales, and consequently, the rheological evolution of magma. This, in turn, significantly impacts the dynamics of volcanic plumbing systems and the associated eruptive styles.

We investigate the rheological changes in Stromboli magma (Italy) during disequilibrium crystallization under non-isothermal sub-liquidus conditions. By systematically varying the cooling rate (1-10 °C/min) and the shear rate (1-10 s-1), we found that cooling rates significantly influence the solidification path of the basalt, while shear rates have a subordinate effect. By comparing our results with literature data on basalts from Mt. Etna (Italy), we observed distinct timescales and rates of solidification, contributing to unique eruptive dynamics in these volcanic plumbing systems.

How to cite: Di Fiore, F., Vona, A., Di Genova, D., Pontesilli, A., Calabrò, L., Mollo, S., Taddeucci, J., Romano, C., and Scarlato, P.: Disequilibrium viscosity of Stromboli basalt: Implications for magma dynamics in active basaltic systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15563, https://doi.org/10.5194/egusphere-egu24-15563, 2024.

EGU24-16330 | ECS | Orals | GMPV7.4

The role of pre-eruptive bubble characteristics in modulating andesitic magma fragmentation 

Daniel Weller, Cristian Montanaro, Donald Dingwell, Shane Cronin, and Bettina Scheu

Various processes involving nucleation, growth, and interaction of bubbles occur as water-rich magma —e.g., of andesitic composition— ascends through a volcanic conduit towards shallower depths. These mechanisms significantly affect the properties of the magma upon fragmentation, including porosity, permeability, and magma strength. Such properties, in turn, can influence the dynamics of fragmentation —such as its speed and efficiency— thus impacting eruptive behaviour. Precisely measuring and understanding how the pre-eruptive bubble size distribution and texture affect fragmentation dynamics poses a scientific challenge that lacks comprehensive quantification methods to date.

In this study, we employed a combination of analytical and experimental methods to explore the processes governing bubble formation and to quantify the impact of their size, distribution, and texture on andesitic magma fragmentation. Our investigation utilised a series of andesitic products originating from the AD 1655 Burrell eruption of Mt. Taranaki, New Zealand. The pyroclasts from this eruption exhibited varying porosity (10 – 80 %) and permeability (10-16 - 10-11 m²). Using scanning electron microscope imagery, we employed FOAMS, an image analysis software, to compute bubble size distributions. Subsequently, we performed rapid decompression experiments on selected samples, capturing the process of fragmentation and clast ejection using two synchronized high-speed cameras. This approach allowed us to track fracture location and evolution over time, enabling the assessment of fragmentation speed and fracture density. Further analyses involved examining the grain size distribution of generated clasts to evaluate the efficiency of fragmentation.

Our texture analysis unveiled that bubble nucleation and growth occurred concurrently during various eruption stages, as evidenced by changes in bubble number density, porosity, and polydispersivity. Correlating these results with the high-speed camera analysis, we observed a significant influence of bubble number density and average diameter on fragmentation speed. Moreover, large bubble clusters appeared to intensify fragmentation speed by weakening local rock strength. Both the number and diameter of bubbles exhibited additional relationships with particle size, efficiency of fragmentation, and fracture density in our samples.

Drawing from the correlation between bubble texture and petrophysical properties, we proposed a conceptual model elucidating the impact of bubble textures on fragmentation dynamics. Furthermore, we evaluated and discussed our findings in the context of previously developed eruptive models of Mt. Taranaki. Our findings, together with variation in the density of the expelled particle-gas mixture, align well with the model depicting a transition in eruptive behaviour and plume stability of Mt. Taranaki during the deposition of the Burrell formation.

 

How to cite: Weller, D., Montanaro, C., Dingwell, D., Cronin, S., and Scheu, B.: The role of pre-eruptive bubble characteristics in modulating andesitic magma fragmentation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16330, https://doi.org/10.5194/egusphere-egu24-16330, 2024.

EGU24-16546 | Orals | GMPV7.4

Amphibole breakdown rim textures as archivists of pre-eruptive magmatic processes 

Paul Wallace, Sarah H. De Angelis, Jessica Larsen, Luca Caricchi, and Yan Lavallée

Amphibole phenocrysts are common in intermediate to felsic magmas where they record information on magma evolution through breakdown rim textures marking shifts in pressure, temperature, volatile concentrations, oxygen fugacity and melt chemistry during ascent. Our ability to track these variables throughout the volcanic plumbing system (e.g., via phase equilibria experiments, geothermobarometry, disequilibrium textures, melt inclusions) has provided the means for interpretating eruption trigger mechanisms, yet a lack of calibrated data on their influence on amphibole stability (and thus reaction rim formation) makes unambiguously distinguishing the mechanism problematic. One such elusive example is the role of CO2 flushing, deemed a likely phenomenon in magmatic systems, precluding an accurate interpretation of natural rim formation, previously assigned to decompression or heating. We performed high-temperature (830–880ºC), high-pressure (120 MPa) experiments to investigate the effects of XCO2 (0.3–0.7) on amphibole reaction rim development in H2O-saturated silicic magmas in shallow volcanic systems, providing new insights for interpreting amphibole rim textures. Our experiments quantify the significant impacts of CO2 on rapidly triggering amphibole breakdown over shorter timescales compared to heating or decompression. 2D textural analysis of the breakdown rim microlites reveal that crystal size, aspect ratio, number density and preferential alignment, together with mineralogy, can be related to a distinct breakdown mechanism. Furthermore, we apply high-resolution electron backscatter diffraction (EBSD) analysis to >100 experimental and natural amphibole reaction rims (Soufrière Hills Volcano, Unzen Volcano, Bezymianny and El Misti). Quantitative mapping reveals systematic variations in crystallographic orientations of the rim microlites relative to the host amphibole, enabling the development of an EBSD criteria that differentiates decompression-, heating-, and CO2-induced amphibole breakdown. The distinct textures produced provides new markers and a new framework for the interpretation of natural rim formation processes. Application of this new quantitative approach over a range of magmatic systems worldwide will improve interpretations of intensive parameters, ascent paths, eruption triggers, and amphibole stability from crystal record archives.

How to cite: Wallace, P., H. De Angelis, S., Larsen, J., Caricchi, L., and Lavallée, Y.: Amphibole breakdown rim textures as archivists of pre-eruptive magmatic processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16546, https://doi.org/10.5194/egusphere-egu24-16546, 2024.

EGU24-16555 | ECS | Posters on site | GMPV7.4

Probing an active, exceedingly shallow rhyolite reservoir with experiments and petrological tools: the case of Krafla IDDP1 

Marize Muniz da Silva, Jonathan Castro, Jackie Kendrick, Paul Wallace, and Yan Lavallée

The discovery of a rhyolitic magma body at a depth of 2.1 km during drilling of the first well in the Iceland Deep Drilling Project (IDDP-1) at Krafla volcano, NE Iceland, presented an unprecedented opportunity to explore shallow magma properties and the root of geothermal systems. Yet, to safely access this near-magma energy, we require an in-depth understanding of magmas’ response to drilling activity and power plant operations, which we target here using the natural samples retrieved in-situ from the magma body during IDDP-1. The glassy fragments display a spectrum of colors (light brown to black), different vesicularities and crystals of plagioclase, pyroxene, Ti-magnetite, and apatite; some crystals exhibit zonation and embayment.

In this study we experimentally explore the stability of the rhyolitic magma to different P-T-X conditions to assess magma response to perturbations prompted by drilling. We tested pressures of 16, 35, and 45 MPa (between hydrostatic pressure and the pressure as estimated by dissolved H2O-CO2 concentration), temperatures ranging from 880 to 920°C, and durations spanning from 6 to 48 hours. All experiments were carried out under water-saturated conditions, with oxygen fugacity fixed by Ni and Co filler-rods to NNO+1 (more oxidized) or QFM (more reducing), respectively. We used the original glass chips (without remelting them) to see how the texture would evolve when subjected to different P, T, X. The main difference observed is when comparing experimental products at NNO+1 or QFM conditions which influenced glass color: darker hues appeared under NNO+1 condition and lighter hues prevailed under QFM condition. Whilst at NNO+1 the phases present in the original mineralogical assemblage were generally relatively stable (with one exception; see below). At 45 MPa, we observe no dissolution of the original phases but overgrowth of pyroxene in all charges. By reducing temperature from 900 ºC to 880 ºC or by increasing the oxygen fugacity (to NNO+1) we observed an increase in microlite content of the same original phases (except for apatite which did not crystallize). At the lower pressure of 35 MPa, the microlite content was higher than at 45 MPa; yet, the original mineralogical assemblage remained, whereby no dissolution took place and pyroxene overgrowth occurred. Again, by decreasing temperature from 920 ºC to 880 ºC or by increasing the oxygen fugacity the microlite content increased. Importantly, quartz crystallized at 880 °C, 35 MPa and under NNO+1 conditions; indicating that these conditions were likely not met during drilling. At 16 MPA, the experiments failed as the Au capsules ruptured due to pressure from excess fluids. Our initial findings suggest that the magma may reside in the crust at a minimum temperature of 900 °C, if at 45 MPa, or 920 °C, if at 35 MPa. This work establishes a “reference frame” for understanding shifts in magmatic parameters that may be triggered by drilling into active systems.

 

How to cite: Muniz da Silva, M., Castro, J., Kendrick, J., Wallace, P., and Lavallée, Y.: Probing an active, exceedingly shallow rhyolite reservoir with experiments and petrological tools: the case of Krafla IDDP1, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16555, https://doi.org/10.5194/egusphere-egu24-16555, 2024.

EGU24-16972 | Orals | GMPV7.4

Interpreting deformation conditions from crystal-plasticity in extrusive lavas  

Jackie E. Kendrick, Paul Wallace, Takahiro Miwa, and Yan Lavallée

The physical evolution of multiphase magmas during shear remains a critical question in volcanology. The presence of solid, liquid, and gaseous phases (with contrasting strength and rheology) serves to partition strain and concentrate stress on each phase when the system is subjected to deformation. For example, gas bubbles generally deform relatively easily, whilst melt can stress and relax repeatedly, erasing its deformation history, and crystals can accumulate stress and suffer permanent damage. In suspensions with high interstitial melt viscosity, high crystal content, or low vesicularity, large stresses may accumulate in the crystalline phase, which may result in crystal plasticity and rupture. All minerals may be subject to crystal plasticity if the conditions are suitable: Whereas diffusion creep may be common in deep magmas deforming slowly over long timescales; dislocation creep is likely more common in shallow magma mushes and erupting lavas.

Recent evidence from natural samples and controlled laboratory experiments suggests that even under very low confinement, the crystals present in lavas may deform by dislocation creep prior to failure. EBSD mapping of experimentally deformed, porous, crystal-rich dome lavas (at magmatic temperature) revealed that crystals underwent dislocation creep. For further analysis we focussed on plagioclase (which dominates the crystal assemblage), and found the misorientation of the crystal lattices within the microlites increased as a function of stress and strain, until rupture. Grain size reduction was seen synchronous to deformation, and fragments of broken microlites recorded the highest distortions; thus, crystals exhibit a plastic limit during dislocation creep. The systematic variation in plasticity with applied conditions demonstrates the key role of crystal plasticity in the deformation of crystal-rich lavas, and the possibility to interpret deformation from the imparted dislocations. To test this, we mapped crystal-plasticity across the shear zone at the margin of the lava spine erupted at Mount Unzen (Japan) in 1994−1995. We found that the degree of crystal lattice misorientation in plagioclase microlites increased systematically across the shear zone towards the marginal shear plane, and also that weak phenocrysts such as mica suffered substantial crystal plasticity.

Whilst the ostensible absence of crystal plasticity in deformed igneous bodies has previously been argued to indicate that melt accumulates all the strain during deformation (particularly if melt viscosity is very low), the lack of deformed crystals may also indicate post-deformation crystallisation or longer deformation timescales (i.e., slower strain rates) which would limit stress accumulation in the crystalline phase (due to both efficient rearrangement during flow and the inability for the melt phase to build stress at slow strain rates). Our work demonstrates how crystal plasticity can be utilised to detail strain localisation textures formed during magma deformation, and although, to date, insufficient data exists to define the stress–strain history of magmas and lavas from the vestiges of crystal-plasticity, there remains hope for its use as a strain marker in the future, with further systematic quantification. Our work further demonstrates that rheological models for multiphase suspensions require consideration of crystal-plastic deformation, which may contribute towards the apparent non-Newtonian behaviour of magmatic suspensions.

How to cite: Kendrick, J. E., Wallace, P., Miwa, T., and Lavallée, Y.: Interpreting deformation conditions from crystal-plasticity in extrusive lavas , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16972, https://doi.org/10.5194/egusphere-egu24-16972, 2024.

The Yali volcanic centre is a relatively young volcano that was active within the last 40,000 year and is part of the Nisyros-Kos volcanic field, representing the most recent evidence of magmatic activity in the western part of the South Aegean Active Volcanic Arc, together with the post-caldera lava dome activity occurred at the nearby Nisyros volcano.  

The Yali volcanic activity (bot explosive and effusive) is still poorly studied, and the plumbing system architecture and magma ascent pathways are barely defined, although it represents an important element to be considered for the evaluation of the volcanic hazard and the potential risk in the area, associated to the accumulation of evolving magma body in the crust.  

The aim of our study is thus to detail the nature of juvenile materials and the evaluation of the magmatic processes occurring in the plumbing system. This would provide important information to define the relationships between the different eruptive events that occurred during the Yali volcano evolution.  

The present-day edifice is constituted by the remnant of the original volcano after intense tectonic and erosion processes. It is composed by two distinct parts with difficult stratigraphic correlation due to the limited exposure and continuity of the deposits. The SW part is built up by a thick succession of pyroclastic materials, generated by the eruption of a submarine pyroclastic deposit (Lower Pumice -YLP) followed by a subaerial activity leading to the emplacement of a pumice-rich pyroclastic fallout (Upper Pumice-YUP) that is topped by two layers of reworked pumice-rich deposits (YRL), separated by a thin paleosoil. The NE part is formed by the eruption of large perlitic lava flows and obsidian lava domes associated to an explosive episode generating the Kamara tuff cone.   

The main volume of the erupted products (pumices and lavas) is composed by evolved juveniles of rhyolitic composition. All the pyroclastic deposits, including the Kamara tuff cone host a variable amount of mafic, crystal-rich clasts (SiO2 from 52.5 to 67.5 wt.%) suggesting the occurrence of mingling processes between different evolved magmas in the feeding reservoir/s, thus implying a mafic, deep, refill of the plumbing system. Our data show that the YLP and YUP pumice have similar homogeneous composition, with the latter having a slightly less evolved character. They also display a quite distinct major, trace elements and Sr-Nd isotopes behavior compared to pumices of the YRL. The lavas are even more evolved than pumices. Moreover, the mafic components reveal a heterogeneous composition and isotopic signatures, suggesting the presence of a complex plumbing system feeding the different explosive and effusive eruptions. 

How to cite: Braschi, E., Vougioukalakis, G. E., and Francalanci, L.: Petrologic constraints on the activity of the youngest explosive events at Yali volcano (South Aegean Active Volcanic Arc, Greece): plumbing system architecture and implication for hazard assessment., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17281, https://doi.org/10.5194/egusphere-egu24-17281, 2024.

EGU24-17296 | ECS | Posters on site | GMPV7.4

On the effect of Cr2O3 addition on the crystallization of trachybasaltic melt 

Stefano Peres, Thomas Griffiths, Fabio Colle, Stefano Iannini Lelarge, Matteo Masotta, and Alessio Pontesilli

Even small variations in minor element composition can affect the crystallization history of a magma, altering the final mineral assemblage and/or microstructural evolution during crystallization.

We discuss the results of two sets of crystallization experiments performed in a piston cylinder apparatus at 400 MPa and at fO2 close to NNO+2, using two synthetic trachybasaltic glasses, one with no Cr2O3 added (Glass 1) and one doped with 0.4 wt.% Cr2O3 (Glass 2). Experiments were carried out under both anhydrous (0 wt.% H2O) and hydrous conditions (2 wt% H2O).

Experiments were initially heated at 1300 °C for 30 minutes to ensure complete melting of the glass and then cooled at a rate of 80°C/min to the final resting temperature (Trest = 1150°C, 1100°C and 1050°C). Dwell time at Trest ranged between 5 minutes and 8 hours. The commonest crystal phases were always clinopyroxene (Cpx, up to 50 vol%) and spinel (up to 5 vol%, specifically chromite [Chr] and/or titanomagnetite [Tmt])

In all samples, some spinel grains are found isolated in the melt, while others are touching a Cpx. The ratio of isolated spinel to spinel in contact depends on the crystallization history of the sample, which varies according to the starting composition.

Experiments performed with Glass 1 consists of Tmt grains always in contact with a Cpx grain, decorating its edges and tips. More than 90% of all Tmt grains following clear crystallographic orientation relationships (CORs) with Cpx, implying heterogeneous nucleation of Tmt on Cpx.

In experiments performed with Glass 2 the amount of isolated Spinel crystals is higher. These grains are constituted by a Chr core and a Tmt rim. Even when these oxide grains are in contact with (or inside) a Cpx crystal, they rarely (<10 % of touching oxide grains) share CORs with Cpx, suggesting that the oxides were the first phases to crystallize, and were subsequently engulfed by Cpx. The rare oxide crystals sharing CORs with touching Cpx are located in the centre of the dendritic Cpx grains, suggesting that Cpx nucleated heterogeneously on the earlier-formed oxide.

We evidence that even small variations in Cr2O3 content can affect the crystallization history of a magma, thereby affecting the final mineral assemblage and the microstructural evolution during crystallization. In particular, by altering the mechanism of crystal nucleation, we speculate that the nucleation of spinel stimulated by subtle changes in the chemistry of magmas (or variations of the fO2 conditions) may result in substantial modification of magma rheology.

Funded by the Austrian Science Fund (FWF): P 33227-N

How to cite: Peres, S., Griffiths, T., Colle, F., Iannini Lelarge, S., Masotta, M., and Pontesilli, A.: On the effect of Cr2O3 addition on the crystallization of trachybasaltic melt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17296, https://doi.org/10.5194/egusphere-egu24-17296, 2024.

EGU24-19154 | ECS | Posters on site | GMPV7.4

Characterization and evolution of the magma reservoir beneath the Asal-Ghoubbet rift, Republic of Djibouti 

Araksan Ahmed Aden, Enikő Bali, Guðmundur Heiðar Guðfinnsson, Gylfi Páll Hersir, Kayad Moussa Ahmed, and Iwona Monika Galeczka

Determinations of the temperatures and pressures of volcanic products during their formation are helpful for understanding magmatic system behaviour and igneous processes. Whereas estimates of the former give insights into the thermal evolution of magmas, the latter provides estimation of the storage depth of magmatic reservoirs. Together they provide practical constraints for understanding the magma storage conditions beneath active volcanic areas and their implications in other research fields, such as geothermal exploration. The Asal-Ghoubbet rift is one of the emergent segments of the Aden Gulf oceanic ridge, which spreads westward on land into the triple junction zone of the Afar depression. The rift-in-rift area has witnessed repeated magmatic and tectonic activity over its ~1 Ma evolution. Most recently, in November 1978, a one-week-long basaltic fissure eruption led to the birth of the Ardoukôba volcano. Due to its active and unique location, the area has been subject to geothermal exploration since the 1970s. However, although intensive geological, geochemical, and geophysical studies have been conducted in the area, detailed knowledge is still lacking regarding the evolution of storage conditions in the magmatic system beneath the Asal-Ghoubbet rift. For this study, eleven samples, representing the time span from ~300 ka to today, were collected in the rift, and geochemical and geothermobarometric analyses were conducted. Two samples representing the oldest basalts in Djibouti (BD and BS) were also added for comparison. The rock samples are tholeiitic to transitional basalts with MgO contents between 3.3 and 10.2 wt%. The negative correlations of TiO2 and FeO contents, and positive of CaO, with MgO indicate that fractional crystallization is an important process in the magmatic system. The crystal cargo of the erupted lavas consists of plagioclase, clinopyroxene and olivine, in order of decreasing amount. Anorthite contents of plagioclase vary between 45and 89, with a main population at ~An85. Most crystals are in disequilibrium with their carrier melts. Clinopyroxenes have Mg# ranging from 47 to 87,with crystals of Dalha basalts (BD) being the most differentiated. Olivine cores and mantles are mostly primitive with a main composition of Fo84. The majority of clinopyroxenes and olivines are in equilibrium with carrier melts, except for BD. Based on geothermobarometric calculations, we propose the existence of two magma storage depths beneath the Asal-Ghoubbet rift. A mid-deep crustal reservoir is located at ~13 km with a mean temperature of 1200°C. It represents the main magma body with higher temperatures and where most of the minerals crystallized. The second one is found at shallow crustal level (5 to 7 km) with lower temperatures (~ 1120°C). Few crystals formed at this depth, which could indicate a smaller size reservoir. Textural and chemical variations of minerals suggest a connection between the two magma bodies, forming the magma plumbing system. Magma storage conditions appear to have been maintained over time, which implies the continuous renewal of the geothermal heat source in the Asal-Ghoubbet rift.

How to cite: Ahmed Aden, A., Bali, E., Heiðar Guðfinnsson, G., Páll Hersir, G., Moussa Ahmed, K., and Monika Galeczka, I.: Characterization and evolution of the magma reservoir beneath the Asal-Ghoubbet rift, Republic of Djibouti, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19154, https://doi.org/10.5194/egusphere-egu24-19154, 2024.

EGU24-19374 | ECS | Posters on site | GMPV7.4

Amphibole trace element signatures of magmatic environments  within the magmatic plumbing system of the 160–30 ka Ciomadul volcanic complex, Eastern Carpathians 

Barbara Cserép, Saskia Erdmann, Réka Lukács, Olivier Bachmann, Ioan Seghedi, Máté Szemerédi, and Szabolcs Harangi

Amphibole is a common mineral in arc magmas, occurring in a wide temperature and pressure range. Its composition is sensitive to the crystallization condition that helps to quantify the magma storage depth, temperature, and redox conditions as well as to characterize the equilibrium melt composition including the water content. It can also be used to reveal the magma evolution pathways and processes occurring in the magmatic reservoir system. We provide here a comprehensive characterization of amphibole formed at different stages of magma evolution in the complex magmatic plumbing system of Ciomadul volcano, the youngest one in eastern-central Europe. A central dacitic lava dome complex built-up 160–96 ka ago, and it was partly destructed by explosive eruptions in the youngest volcanic stage (56–30 ka). We have characterized amphibole compositions both for major and trace elements in the dacitic lava dome and pumice samples.

Amphibole populations can be well discriminated by major and trace element compositions. Amphibole compositions of the 160–90 ka dacites suggest two distinct magmatic environments. (1) A cold (670–750 C°), silicic (70–77 wt% meltSiO2) crystal mush with high crystallinity emplaced in the shallow crust at 8–15 km depths. These low-Al-Mg amphiboles show low Zr, Hf, Ti, Sr, Ba, Cr, and Ni concentrations, a negative Eu anomaly, moderate La/Sm ratio and high Nb, and Dy concentrations reflecting the evolved nature of the host melt. (2) A relatively mafic (52–60 wt% meltSiO2), hotter (940–980 Cº) magma, accumulated presumably in the lower crust. Amphibole crystallizing within this environment has high Al-Mg content and low Ni and Cr, moderate La/Sm ratio, lack of negative Eu-anomaly, and high Nb, Ta, Dy, Zr, Hf, Ti, Sr and Ba concentrations.

During the explosive eruption-dominated period (56–30 ka), the cold crystal mush environment remained, but amphibole records the presence of two additional, more primitive, hydrous and oxidized recharge magmas: (3) A magma with 56–69 wt% meltSiO2, 880–980 °C, with high Al-Mg amphibole having moderate Zr, Hf, Ti, Sr, Ba, Nb, Ta, Dy, Cr, Ni and without negative Eu-anomaly. (4) A mafic magma containing unique low-Al, high-Mg amphibole with high Cr–Ni concentrations. It crystallized at >800 °C temperature and has low Zr, Hf, Ti, Ba, Nb, Ta, Dy, and La/Sm ratio. Recharge of these mafic magmas into the felsic crystal mush initiated rapid remobilization, hybridization and thin amphibole overgrowth with transitional compositions during magma ascent. We demonstrate how amphibole compositions can be used to track deep to shallow fractionation within the magma plumbing system at various conditions. Notably, a compositional shift can be observed in the recharge magma amphibole compositions from the extrusive to the younger explosive eruption stage. The mafic magmas became more hydrous and oxidized with time that could contribute to the change in eruption style.

This study is supported by the ÚNKP-23-3 New National Excellence Program of the Ministry for Culture and Innovation and by the Hungarian National Research Fund project (K 135179).

How to cite: Cserép, B., Erdmann, S., Lukács, R., Bachmann, O., Seghedi, I., Szemerédi, M., and Harangi, S.: Amphibole trace element signatures of magmatic environments  within the magmatic plumbing system of the 160–30 ka Ciomadul volcanic complex, Eastern Carpathians, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19374, https://doi.org/10.5194/egusphere-egu24-19374, 2024.

EGU24-19483 | ECS | Orals | GMPV7.4

The evolution of a basaltic fissure eruption 

Ariane Loisel, Edward Llewellin, Richard Brown, Antonio Capponi, Tim Orr, and Matthew Patrick

Basaltic eruptions produce lava flows that have the potential to destroy local infrastructure and emit toxic gas and particles that may adversely impact public health. Predicting their style and evolution is therefore a key goal in volcanology. This requires an understanding of the multiphase flow processes that operate within the sub-volcanic system.

Field observations of both solidified and erupting basaltic fissures at Kīlauea volcano (Hawai‘i, USA) are synthesised with laboratory analogue experiments to determine the evolving organisation of gas-driven flow patterns within basaltic feeder dyke systems, and their effects on eruptions. Our laboratory kit was designed to perform scaled analogue experiments of bubbly flows in a 3.0 x 2.0 x 0.03 m glass-walled slot. This geometry mimics the geometry of dykes that feed most basaltic eruptions, whereas previous experimental studies have usually assumed a cylindrical conduit. The role that localization of fissure segments plays in shaping eruption behaviour is explored by occluding parts of the top of the slot. We also consider the role played by flooding of the vent with lava, focussing on long-lived systems that are reproduced by a conical vent geometry.  We collate the imagery acquired during our analogue experiments with recent monitoring datasets and a detailed field investigation of the spatial organization of vents and drain-back structures on solidified fissures at Kīlauea to improve our understanding of the controls on the eruptive behaviour of basaltic systems. This study will help interpret the underlying flow patterns within feeder dykes from real-time gas and erupted lava flux measurements.

How to cite: Loisel, A., Llewellin, E., Brown, R., Capponi, A., Orr, T., and Patrick, M.: The evolution of a basaltic fissure eruption, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19483, https://doi.org/10.5194/egusphere-egu24-19483, 2024.

EGU24-19813 | ECS | Posters on site | GMPV7.4

The ultimate 1631 CE sub-plinian eruption of Mt. Vesuvius: hints on pre-eruptive magmatic processes from zoned clinopyroxenes                                

Carlo Pelullo, Hélène Balcone-Boissard, Bruna Cariddi, Sumit Chakraborty, Massimo D'Antonio, Maddalena De Lucia, Sandro de Vita, Mauro Antonio Di Vito, Paola Petrosino, Monica Piochi, Nicolas Rividi, Germano Solomita, Domenico Sparice, Vittorio Zanon, and Ilenia Arienzo

The 1631 CE eruption is the most violent and destructive event of the last millennium at Mt. Vesuvius, followed by a persistent small magnitude activity that has lasted until the 1944 CE. Selected units of the proximal stratigraphic section cropping out at Cognoli di Ottaviano (Monte Somma), <2 km from the current Vesuvius crater, have been sampled. To retrieve information on types and timescales of magmatic processes and to possibly link them to precursory phenomena, the chemical composition of clinopyroxene crystals has been acquired. Mineral chemistry (Si, Ti, Al, Fe, Mg, Mn, Ca, Na and Cr) has been obtained on the core and the rim of 50 unzoned crystals well-characterized in terms of texture. Mineral microanlaysis were realized along core-to-rim transects, varying from 40 μm to 500 μm in length, in 59 zoned crystals using a beam diameter of 2 μm and 1 μm spacing between individual points.

The mineral composition allows to characterize the zoning patterns and provides information on the environments in which crystals grew. About 70% of the zoned crystals show patchy zoned cores with-or-without- complex zoning in the outer bands. The other crystals show normal zoning, normal-to-reverse zoning, reverse zoning and complex zoning (e.g., oscillatory zoning). Zoned clinopyroxenes have a diopsidic/Fe-diopsidic composition (Wo52-48-En47-30-Fs17-5). Mg# [molar Mg2+/ (Mg2+ +Fetot) *100] of the zoned clinopyroxene ranges between 90 and 62, with some differences observed in the different bands of the crystals.

The zoning pattern shows two or more bands with constant Fe-Mg and/or Al and/or Ti composition separated by both either sharp or diffuse boundaries. The occurrence of bands of constant composition in the zoning patterns of minerals suggests that crystal growth occurred for certain several periods of time under stable conditions, separated by events involving fast changes of thermodynamic variables (pressure, temperature, oxygen or water fugacity). Different compositional populations have been distinguished in the clinopyroxene zoning pattern, e.g., through the Mg# parameter, but also other elements concentrations such as Al2O3. Each population results from growth under a Magmatic Environment (ME), namely specific thermodynamic conditions. The connections between MEs recorded by clinopyroxene zoning pattern allow to accurately reconstruct the history of the magmatic processes across the clinopyroxene growth. As a whole, the zoned clinopyroxenes from the 1631 CE eruption record a huge variety of MEs, testifying to a complex history of crystallization under different conditions, reflecting long-lasting magmatic processes from mantle depth to shallow reservoir(s).

How to cite: Pelullo, C., Balcone-Boissard, H., Cariddi, B., Chakraborty, S., D'Antonio, M., De Lucia, M., de Vita, S., Di Vito, M. A., Petrosino, P., Piochi, M., Rividi, N., Solomita, G., Sparice, D., Zanon, V., and Arienzo, I.: The ultimate 1631 CE sub-plinian eruption of Mt. Vesuvius: hints on pre-eruptive magmatic processes from zoned clinopyroxenes                               , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19813, https://doi.org/10.5194/egusphere-egu24-19813, 2024.

EGU24-19962 | ECS | Posters on site | GMPV7.4

Vesteris Seamount - Magma plumbing dynamics and petrological evolution of an alkaline intra-plate volcano of non-plume and non-rifting origin 

Aaron Röhler, Christoph Beier, Andreas Klügel, Wolfgang Bach, and Karsten Haase

Vesteris Seamount is a solitary, alkaline intraplate volcano of non-plume and non-rifting origin located in the Norwegian-Greenland Basin. During RV Maria S. Merian Cruise MSM86 highly detailed sampling of the Seamount recovered over 70 rock samples from the whole volcanic edifice during TV-Grab and ROV Marum SQUID operations. Major- and trace element geochemical analyses of matrix compositions and phenocrysts were conducted by electron microprobe and laser ablation ICP-MS. To investigate the petrogenesis of the Vesteris rock suite and the magma plumbing dynamics the analytical results were applied to least-squares mass balance and clinopyroxene-liquid thermobarometry models.

Primitive basanites and alkali-basalts reflect individual melt batches from a deep mantle source. A tight liquid line of descent can be observed from basanitic to trachytic compositions. The main control on the magmatic evolution is exerted by fractional crystallization. Textural and chemical evidence indicate a more pronounced influence of magma mixing during the genesis of the evolved tephriphonolitic and trachytic compositions.

Results from our clinopyroxene-melt thermobarometry calculations show a bimodal pressure distribution that indicates upper mantle storage between 500 and 850 MPa (15-27 km depth) and shallower crustal storage between 250 and 460 MPa (7-14 km). The magmatic evolution of basanites and alkali-basalts by crystal fractionation began in the upper mantle and subsequently migrated into crustal levels where phonotephritic to trachytic magma compositions developed. A multi-stage model for the evolution of the magma plumbing system below Vesteris Seamount is proposed based on the geochemical and thermobarometric data.

Initially, dykes transported deep mantle melts to the surface. Subsequent dyke and sill emplacement and high magma fluxes led to the formation of a reservoir in the upper mantle and magma accumulation zone at the uppermost mantle to Moho levels. Progressive weakening of the crust and continuing high magma fluxes led to and development of a crustal storage zone. At a later stage volcanic activity became more episodic and magmatic evolution was controlled mainly by fractional crystallization. The basanites and phonotephrites were stored at upper mantle levels, evolved tephriphonolitic and trachytic magmas were stored at crustal levels prior to eruption. During episodes of increased volcanic activity, the crustal reservoir was recharged by batches of poorly differentiated melts and initiated magma mixing.

How to cite: Röhler, A., Beier, C., Klügel, A., Bach, W., and Haase, K.: Vesteris Seamount - Magma plumbing dynamics and petrological evolution of an alkaline intra-plate volcano of non-plume and non-rifting origin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19962, https://doi.org/10.5194/egusphere-egu24-19962, 2024.

EGU24-20705 | ECS | Orals | GMPV7.4 | Highlight

Ongoing unrest at Campi Flegrei, Italy: clues from the antecrystic records 

Charline Lormand, Luca Caricchi, Guido Giordano, and Roberto Isaia

The largest deformation since the start of the ongoing unrest at Campi Flegrei caldera, Italy, was recorded in 2023 with an average uplift rate of 17 cm/year [1]. This coincides with the exponential increase of seismic events since 2017 by a factor of 32 (i.e., 6065 events in 2023 versus 3181 in 2022, 2232 in 2021, 1520 in 2020, 799 in 2019, etc.). Such observations raise questions regarding the origin and the future of the ongoing unrest especially in determining if the underlying cause involves ascent of magmatic fluids only or if magma is also involved. To this end, a forensic approach focusing on the characterisation of crystal cargoes from past eruptions help understanding of the conditions and pre-eruptive processes that occur within magmatic plumbing system prior to eruptions of different styles and comparing these possible scenarios with the current unrest.

Juvenile clasts found in the base layer from deposits of past eruptions (e.g., Agnano-Monte Spina, Solfatara, Averno, Astroni, Monte Nuovo) of different eruption styles and size were collected. The 1538 eruption of Monte Nuovo is the ideal benchmark to link the petrological evidence to the precursory deformation documented, whereas the historical eruptions selected allow for consideration of a wider range of eruption scenarios. We will present machine learning thermobarometric data and chemical patterns inferred by clustering techniques used to constrain the temperature-pressure paths of the magma and to identify possible systematics during the period of magma migration to the surface preceding the eruption. Ultimately, we aim to link the petrological signatures conveyed by antecrysts with the deformation triggered during magma intrusion and expansion of volatiles upon ascent.

Reference: [1] INGV. Bollettini di sorveglianza dei vulcani campani. http://www.ov.ingv.it/ov/bollettini-campi-flegrei/ (2016-2023).

How to cite: Lormand, C., Caricchi, L., Giordano, G., and Isaia, R.: Ongoing unrest at Campi Flegrei, Italy: clues from the antecrystic records, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20705, https://doi.org/10.5194/egusphere-egu24-20705, 2024.

GMPV8 – Physical and chemical processes in volcanic systems

EGU24-5775 | Orals | GMPV8.1

Asphalt Volcanism versus Asphalt Seepage - Examples from the Campeche-Sigsbee Salt Province, Southern Gulf of Mexico 

Gerhard Bohrmann, Miriam Roemer, Yann Marcon, Thomas Pape, Chieh-Wei Hsu, Daniel Smrzka, and Ian MacDonald

Asphalt deposits have been described from several places of the ocean floor, like the Gulf of Mexico, the Santa Barabra Basin, the Angolan margin and the southwest Atlantic Ocean offshore Brazil. The term asphalt volcanism has been introduced as a novel type of hydrocarbon seepage after an area of approximately 1 km2 solidified asphalt was found on top of one of the Campeche Knolls in the southern Gulf of Mexico named Chapopote. Visual seafloor surveys revealed extensive surface deposits of solidified asphalt and light crude oil, emanating from sites along the rim of a crater-like structure in 2.900 m water depth. Large areas of the asphalt deposits were colonized by vestimentiferan tubeworms, bacterial mats, and other biological communities. Also discovered alongside the asphalt were locations of sediment/gas hydrate interlayering associated with emanating gas and oil bubbles from the seafloor. Seafloor mapping in the Southern Gulf of Mexico revealed various morphological elevations like knolls and ridges which all are related to salt diapirism of the underlying sediment sequences. Most of those features show crater like areas associated with seepage. During recent expeditions, the crater structures of Mictlan Knoll and Tsanyao Yang Knoll were measured in high resolution with an AUV and sampled in detail and visually examined with MARUM ROV QUEST4000. Although large areas are also covered with lava-like asphalt sheets, the asphalt seems not to be flown at higher temperatures. Extrusion of heavy liquid oil in form of whips or sheets were observed at several locations which indicate a slow consolidation of the liquid oil to form firm asphalt. After extrusion, chemical and physical changes in the asphalt generate increasing viscosity gradients both along the flow path and between the flow’s surface and core. This allows the asphalt to form pāhoehoe lava-like shapes and to support dense chemosynthetic communities over timescales of hundreds of years.

How to cite: Bohrmann, G., Roemer, M., Marcon, Y., Pape, T., Hsu, C.-W., Smrzka, D., and MacDonald, I.: Asphalt Volcanism versus Asphalt Seepage - Examples from the Campeche-Sigsbee Salt Province, Southern Gulf of Mexico, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5775, https://doi.org/10.5194/egusphere-egu24-5775, 2024.

EGU24-5963 | ECS | Posters on site | GMPV8.1

Impact of sedimentary environment on mechanism of mass, fluid and energy transport in the South Caspian basin  

Shalala Huseynova, Namaz Yusubov, and Ibrahim Guliyev

Mud volcanism represents one of the unique natural phenomenon that reflects subsurface processes characterized by movement of large volumes of sediments and fluids in the Earth’s crust. The significant part of world mud volcanoes is concentrated within the on- and offshore Azerbaijan, South Caspian basin (SCB).

The study integrates comprehensive geological, geophysical and geochemical database and presents the results of the analysis of the sedimentary environments in SCB to understand origin and development of mud volcanism in the context of the evolution of the basin. The interpretation of new 2D and 3D seismic data shows that the roots mud volcanoes do not extend below the base of Oligocene-Lower Miocene Maikop Group. The features of sedimentation were studied in details and the sedimentation model of Maikop Group was suggested.

According to the geochemical data and thermobaric conditions Maikop Group considered as the main hydrocarbon source rock within the South Caspian basin. Sedimentary environment during Oligocene-Early Miocene within the territory of Azerbaijan and adjacent Caspian Sea characterized by the complex interaction of various sedimentary processes resulted in the formation of a unique sedimentary complex. The accumulation of Maikop deposits is associated with the beginning of the formation of the folded mountain structures of the Greater Caucasus, the Kopetdag, and the Elbors mountain systems surrounding the SCB, which were the main provenance of clastic material. According to seismic data, the thickness of Maikop sediments currently reaches 3000 m indicating high sedimentation rates over such a relatively short period of geological time. The recent paleontological and geochemical data suggests that Maikop deposits accumulated mainly in the deep marine environment. The rapid burial and subsidence of Maikop sediments occurred because of subsequent intense (avalanche) sedimentation, especially in the Pliocene-Quaternary period. Due to rapid burial, Maikop sediments remain underconsolidated, water-saturated and represent a plastic clay mass, overlapped by thick sequence of denser sediments of the Low Pliocene Productive Series. Thus, as a result of deep subsidence and subsequent catagenic transformations Maikop medium turned into closed physico-chemical system characterized by specific elision processes. The sedimentary environment providing the 20.5 km thick sedimentary filling of the SCB controls mass, fluid and energy transfer within the basin, resulted in formation of mud volcanoes and hydrocarbon accumulations.

Structural interpretation of seismic and geological data, carried out over the past 25 years, indicates that the hydrocarbon deposits discovered in SCB are confined to rootless structures, i.e. injection folds. The formation of injection folds in the sedimentary cover occurs at different stages of basin development due to the alternation of transgressive and regressive series of sediments represented by the layers of clay and sand. All the folds are complicated with mud volcanoes indicating genetic relationship between them, thus the results of paleoreconstructions suggest that mud volcanism in the study area appears to be synchronized in time and space with the growth of anticlinal folds. The mechanism of mud volcano formation based on the gravitational instability has been suggested.

How to cite: Huseynova, S., Yusubov, N., and Guliyev, I.: Impact of sedimentary environment on mechanism of mass, fluid and energy transport in the South Caspian basin , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5963, https://doi.org/10.5194/egusphere-egu24-5963, 2024.

EGU24-8033 | ECS | Orals | GMPV8.1

Estimates of heat release to the atmosphere related to effusive volcanic eruptions and intrusive activity during the 1975-84 rifting episode of Krafla, NE-Iceland 

Patricia Fehrentz, Magnús Tumi Guðmundsson, Hannah Iona Reynolds, Sidney R. Gunnarson, Joaquin Munoz Cobo Belart, and Michaela Chodora

The heat transfer dynamics in volcanic geothermal areas determine the options for geothermal energy exploration. Intrusive and eruptive events provide additional heat input into the geothermal system, as cooling and solidification of the magma heats the surrounding host rock and water in the porous matrix. The evaporation of the water leads to convection and an advective rise of steam in the fissures. Steam rises further and diffuses into the atmosphere depending on wind conditions. The heat lost by steam released to the atmosphere is in many cases one of the significant parameters that determine the heat budget of a geothermal system.

The Krafla fires describe a period of volcanic activity at the Krafla volcano in North-East Iceland from 1975 to 1984 with nine volcanic eruptions and several more intrusive events. This activity was part of a major rifting episode where several meters of widening occurred along the Krafla fissure swarm. The rifting and associated intrusive activity had a significant effect on the geothermal system. Aerial photographs taken during or a few months after each eruption are used to determine the position and size of the fumaroles and associated steam generation. The heat output of the steam clouds is empirically related to its area, expressed as a power-law function (Hochstein & Bromley, 2001). The escape of water vapor, and thus the prevalence of fumaroles associated with these events, is mainly evident on the eruptive fissures. Surface alteration is prevalent and a sign of current or recent steaming. The results for heat lost to the atmosphere can be compared with the heat released by the cooling of the magmatic intrusions formed in the upper crust, providing heat to the existing geothermal area.

How to cite: Fehrentz, P., Guðmundsson, M. T., Reynolds, H. I., Gunnarson, S. R., Belart, J. M. C., and Chodora, M.: Estimates of heat release to the atmosphere related to effusive volcanic eruptions and intrusive activity during the 1975-84 rifting episode of Krafla, NE-Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8033, https://doi.org/10.5194/egusphere-egu24-8033, 2024.

EGU24-9133 | Posters on site | GMPV8.1 | Highlight

The Goshogake hydrothermal field (northern Japan): purely geothermal or hybrid sediment-hosted? 

Adriano Mazzini, Zhang Naizhong, Giuseppe Etiope, Mellinda Aimee Jajalla, Mayuko Nakagawa, and Alexis Gilbert

The Goshogake hydrothermal field in Tohoku, northern Japan, is located on the western flank of the Akita Yakeyama volcano. This N-S elongated field extends over ~20-25 acers and is placed over a tectonic discontinuity that controls the migration of hydrothermal fluids. A variety of surface degassing manifestations can be distinguished including small hydrothermal lakes, clustered bubbling pool fields, active mud erupting gryphons, sulfur-rich fumaroles and localized apparently oil-rich pools. So far it remains unclear if this system and the released gases are purely magmatic or if is also involved the migration of mantle-derived fluids interacting with buried sedimentary deposits. Here we report the result of field observations and fluid samples analyses. The measured temperatures of the active seepage sites range from 33 to 97 °C (in large part higher than 90 °C), while pH is overall low at all sites (i.e. ~2.5).

Gas analyses reveal that all the active sites are CO2-dominated with slightly higher CH4 content in the colder and mud seeping sites. While CO2 has a distinct mantle-derived isotopic signature, the origin of methane is still debated. The apparent d13C thermogenic signature of methane, could also be related to an abiotic origin which would be consistent with a CO2-dominated geothermal system. The presence of oil, if confirmed, could be related to shallow-sourced hydrothermal oil (e.g. similar to that described by Didyk and Simoneit (1989), or, more interestingly, could indicate that this active site is part of a petroleum system potentially linked with deeply buried lacustrine sediments that fill a 1-Ma-caldera formed after a ignimbrite eruption. The possible presence of these deposits in the erupted mud has been suggested by Komatsu et al., (2019) based on mineralogical analyses.

To further test this hypothesis, we are now conducting multiple analyses on the samples recovered from 6 locations at the Goshogake field, including the isotope analysis of water, gas, oil and mud compositions to unravel the source of these fluids as well as the reactions that took place at this site. If confirmed, Goshogake could potentially be the first example of known sedimentary hosted geothermal system in Japan. We speculate that targeted fieldworks would likely identify other hybrid systems in the country.

How to cite: Mazzini, A., Naizhong, Z., Etiope, G., Jajalla, M. A., Nakagawa, M., and Gilbert, A.: The Goshogake hydrothermal field (northern Japan): purely geothermal or hybrid sediment-hosted?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9133, https://doi.org/10.5194/egusphere-egu24-9133, 2024.

EGU24-10456 | ECS | Orals | GMPV8.1

Mud volcanism and mud breccia clasts: how did they reach the surface? 

Marlysa Vivier, Hongliang Wang, Viktoriya Yarushina, and Adriano Mazzini

Mud volcanism is a geological phenomenon broadly diffused in active and passive tectonic settings and it is typically associated with petroleum systems. The mechanisms driving this process are the overpressure resulting from the generation of hydrocarbons at depth combined with the gravitative instability (e.g., shale buoyancy and density inversion) of the more buoyant rapidly buried sediments.

Mud volcanoes experience episodic short-lived eruptive events during which the overpressured fluids and sediments are burst at the surface featuring spectacular explosive events. The erupted material is termed “mud breccia” and represents a mixture of all the lithologies that are intersected by the mud volcano conduit. The overpressured fluids driving the growing diapir promote the grinding and fracturing of the buried sedimentary formations throughout the conduit. As a result, the erupted mud breccia is a mixture of fine-grained sediments (i.e. matrix=clay, silt and sand) and larger clasts. Clasts can vary in size from few centimetres up to several cubic meters. So far it remained unclear how large clasts can travel from sedimentary sequences buried at several kilometers depth.

Here we present some numerical modelling experiments to simulate the rise of large blocks moving from the roots of the mud volcano feeder channel and ultimately reaching the surface during the powerful eruptions.

First, we study the slow rise of large clasts within the growing diapir of buoyancy sediment in the deep part of the mud volcano conduit. The geodynamical two-phase (solid + fluid) flow equations of mass balance, force balance and Darcy’s law are solved with Pseudo-transient method. The preliminary results shows that long distance (e.g. several km) transport of clasts within the diapir is possible, under the driven force provided by the buoyancy of the sediment and the upward fluid flow. The actual rise speed is dependent on the viscosity and the permeability of the solid matrix.

Second, we apply a Verlet method model to simulate the eruption phase. We assume that the eruptive events occur when at shallow depth within the conduit is reached an overpressure sufficient to overcome the overburden lithospheric pressure. When these conditions occur, and when the overpressured fluids are expelled at the surface, the fluidization of the sediments is triggered, and large clasts may be transposrted to their final destination at the surface. Preliminary results reveal that during this process large clasts can be transported. This method focuses on the movement of the clasts themselves. The viscosity of the surrounding fluids is taken into account with a linear drag force. Nevertheless, a method considering the movement of the surrounding fluids could be a possible improvement.

How to cite: Vivier, M., Wang, H., Yarushina, V., and Mazzini, A.: Mud volcanism and mud breccia clasts: how did they reach the surface?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10456, https://doi.org/10.5194/egusphere-egu24-10456, 2024.

EGU24-10620 | ECS | Orals | GMPV8.1

Combining ROV-based acoustic data and underwater photogrammetry to characterize Hakon Mosby Mud Volcano (Barents Sea) cold seep systems 

Luca Fallati, Giuliana Panieri, Claudio Argentino, Andrea Giulia Varzi, Stefan Bünz, and Alessandra Savini

Cold-seeps have a unique geo-ecological significance in the deep-sea environment. They impact the variability of present-day submarine sedimentary environments, affecting the evolution of the landscape over time and creating a variety of submarine landforms, one of which is Mud Volcanoes (MVs). MVs form due to mud, fluids, and gas extrusion, mainly methane, from deeper sedimentary layers. These natural gas seepage systems could significantly affect climate change and the global carbon cycle. We present a comprehensive method that combines ROV-based multibeam mapping and underwater photogrammetry to enhance the understanding of the physical relationships between geomorphic units characterizing the Hakon Mosby Mud Volcano (HMMV) and the distribution of associated habitats.

HMMV is indeed characterized by high thermal and geochemical gradients from its centre to the margins, resulting in a clear zonation of chemosynthetic communities. Our approach integrates multi-resolutions and multi-sources data acquired using a work-class ROV. The ROV-based microbathymetry data helped to identify the different types of fine-scale submarine landforms in the central part of HMMV. This revealed three distinct geomorphic units, with the central hummocky region being the most complex. ROV images were analyzed using a defined structure from motion workflow to study this area further, producing millimetric resolution 2D and 3D models. Object-Based Image Analysis (OBIA), applied on orthomosaics, allowed us to obtain a fine classification of main benthic communities covering a total area of 940m2, including the active seepage area of the hummocky rim. Four major substrate types were identified in these regions: uncovered mud, bacterial mats high-density, bacterial mats low- density, sediments and tubeworms. Their relationship with terrain morphology and seepage activity were investigated at different spatial scales, contributing to a deeper understanding the ecological functioning of cold seep ecosystems in MVs.

The proposed workflow and innovative processing techniques could serve as a model for future studies on cold-seep systems. These investigations aim to clarify the extent to which geomorphic, biogeochemical, and ecological processes occurring in extreme environments are inherently linked and marked by the spatial patterns found in associated habitats and sedimentary environments. 

How to cite: Fallati, L., Panieri, G., Argentino, C., Varzi, A. G., Bünz, S., and Savini, A.: Combining ROV-based acoustic data and underwater photogrammetry to characterize Hakon Mosby Mud Volcano (Barents Sea) cold seep systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10620, https://doi.org/10.5194/egusphere-egu24-10620, 2024.

EGU24-11343 | ECS | Orals | GMPV8.1 | Highlight

Geophysical characterisation of an actively gas-seeping pockmark on the West-Svalbard continental slope 

Irene Viola, Stefan Bünz, Panieri Giuliana, and Zattin Massimiliano

Seabed fluid flow is a globally significant natural process with implications for various aspects of the marine and global environment.

The study focuses on methane seeping from a newly investigated pockmark in one of the most significant seepage province in the world: the West Svalbard continental drift. The study was conducted on historical databases compared with new geophysical data acquired during Akma2 Ocean Senses expedition in may 2022. The expedition employed ROV technology, SBP data, heat flow and bathymetric data to uncover unprecedented insights into the geological and environmental factors at play. In particular, the study conducted on this active gas-seeping pockmark provided insight about its formation, migration, geothermal and gas exchanges and impact on the marine environment. The importance of understanding the mechanisms and identifying seabed fluid flow is emphasised for comprehending its distribution over time and space. The features associated with fluid flow are determined by fluid and migration mechanisms, influenced by the stress environment within sediments.

This study adds new information that can be used for understanding the impact of seabed fluid flow for addressing environmental hazards, evaluating energy resources, and climate changes.

How to cite: Viola, I., Bünz, S., Giuliana, P., and Massimiliano, Z.: Geophysical characterisation of an actively gas-seeping pockmark on the West-Svalbard continental slope, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11343, https://doi.org/10.5194/egusphere-egu24-11343, 2024.

EGU24-12897 | Posters on site | GMPV8.1

First indications on CH4 origin in the CO2-dominated gas discharges of the western Eger Rift (Czech Republic) 

Walter D'Alessandro, Kyriaki Daskalopoulou, Fausto Grassa, Andrea Vieth-Hillebrand, Martin Zimmer, Samuel Niedermann, and Heiko Woith

Tectonic structures such as faults and fractures act as preferential pathways for gas ascent and their consequent release into the atmosphere. Magma-derived gases are widespread throughout the western Eger Rift (Czech Republic), an intraplate region without active volcanism but with the occurrence of mid-crustal earthquake swarms. Geogenic COdischarges from the Počatky–Plesná fault zone (PPZ), Mariánské Lázně Fault (MLF), Bad Brambach (BB), and a deep local fault (DLF) have been sampled since 2021. Gases were analysed for their chemical (CO2, N2, O2, Ar, He, CH4, and H2) and isotopic contents (noble gases, CO2, and CH4). Results showed that CO2 is the dominant gas species (concentrations > 99.4%), with the remaining gases being present in minor amounts. The He isotopic composition for gas samples from the PPZ and MLF is typical for the subcontinental lithospheric mantle (SCLM - with 3He/4He ratios between 5 and 6 RA), while gases from BB and the DLF show a lower mantle input (3He/4He is 3.2 and 2.4 RA, respectively). δ13CCO2 data reflect a SCLM CO2 signature (-4 to -1 ‰ vs. V-PDB). First CH4 isotopic data present values between -52.0 and -47.1 ‰ vs. V-PDB for δ13CCH4 and between -307 and -284 ‰ vs. V-SMOW for δ2HCH4. With the exception of samples collected from the MLF that show a clear thermogenic CH4 origin, all the other samples present isotopic values and CH4/(C2H6+C3H8) ratios that suggest a likely biogenic origin, with secondary processes playing a crucial role on the gases’ isotopic signature. It should be noted that low CH4concentrations (<100 μmol/mol) correspond to low CH4/3He ratios (around 104) in CO2-rich magmatic gases, suggesting a possible common origin for these gases. Therefore, multiple origins of CH4 (biogenic and volcanic-geothermal) cannot be excluded.

This research is a part of the MoCa - “Monitoring Carbon” project and this work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 461419881.

How to cite: D'Alessandro, W., Daskalopoulou, K., Grassa, F., Vieth-Hillebrand, A., Zimmer, M., Niedermann, S., and Woith, H.: First indications on CH4 origin in the CO2-dominated gas discharges of the western Eger Rift (Czech Republic), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12897, https://doi.org/10.5194/egusphere-egu24-12897, 2024.

EGU24-14206 | ECS | Orals | GMPV8.1

Methane seeps features characterization on the Moñito continental shelf, Colombian Caribbean, through a multi-scale and multi-method approach 

Andrea Giulia Varzi, Giulia Galimberti, Aaron Micallef, Alessandra Savini, and Paula Andrea Ramirez Zapata

When referring to gas in marine sediment, we mean natural gas trapped in the sub-bottom sediments and escaping from the sub-seafloor into the marine environments. Among gases, methane is the most common one, and may have diverse origins, including both thermogenic or microbial sources. Natural seepages are globally distributed, with notable occurrences along  continental margins. They significantly affect the local marine ecosystems and the surrounding substrate, other than being a wake-up call in terms of geohazards.

Since the discovery of the Chuchupa and Ballenas fields in the 1970s, the offshore Colombian Caribbean has been considered a gas province mainly dominated by methane, most likely generated by microbial/thermogenic activities. Nevertheless, there is still little knowledge of this area. Since methane is a potent greenhouse gas, it is important to evaluate the contribution of seabed emissions to the global budget. This is particularly true when they are located in relative shallow waters since they represent an important source of the methane flux from lithosphere to hydrosphere and finally atmosphere. Moreover, methane-enriched environments are peculiar habitats and hot-spot of biodiversity.

The Colombian project “Methane Seep Hunting: a multi-scale and multi-method approach” aims at developing a multi-scale and multi method approach to detect methane seeps, determine their current/past seepage activity, and identify their source using the state of art technology in the Colombian Caribbean. Specifically, it aims at the characterization of the methane seeps discovered in the Moñito continental shelf.

Ship-based MEBS data collection over about 220 km2 of seafloor performed in May 2022 revealed the presence of more than 20.000 pockmarks, at places associated to the presence of flares in the water column. In addition, other positive morphologies have been recognized, depicting the presence of a past and/or present fluid flow system.

Keywords: geomorphology; methane seeps; pockmarks; fluid flow system; Colombian Caribbean; tropics; climate change 

How to cite: Varzi, A. G., Galimberti, G., Micallef, A., Savini, A., and Ramirez Zapata, P. A.: Methane seeps features characterization on the Moñito continental shelf, Colombian Caribbean, through a multi-scale and multi-method approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14206, https://doi.org/10.5194/egusphere-egu24-14206, 2024.

EGU24-15574 | Orals | GMPV8.1

The INGV-PROMUD Project: multidisciplinary monitoring of Mud Volcanoes  

Paolo Madonia and the The INGV-PROMUD team

Mud volcanoes (MVs) are geological structures built by the ejection of a multiphase mixture, composed of cold gases (principally methane), high salinity waters and clayey sediments, dragging rock fragments at the surface. This mixture ascends along lithological or structural discontinuities, creating features as cones or pools. Beyond MVs role in global warming (they are the second natural methane source), they can be a source for geohazards: their ordinary activity can be interrupted by paroxysmal events, characterized by gas blasts and sudden expulsions of huge amounts of mud, whose fallout and subsequent flow can damage facilities and endangering animal and human lives. In spite of the geo-risk associated to their activity, a surveillance protocol of MVs have never been implemented. Large earthquakes or hydrocarbon exploration drillings have been claimed as possible triggers of MVs paroxysms, but the related scientific debate have not led to unanimous conclusions.

The INGV-PROMUD project (https://progetti.ingv.it/it/promud) is aimed to investigate the indicators of the activity of MVs, with the ultimate goal of individuating possible precursors of paroxysmal events. It is a 3-years (2023-2025) multidisciplinary project, based on data acquired by both permanent networks and spot surveys in two main study sites in Italy: the Salse di Nirano (Northern Apennines, ) and the Maccalube di Aragona (Sicily), both managed as nature reserves by the regional governments of Emilia-Romagna and Sicily, respectively.

Research activities are subdivided in 5 Working Packages (WPs):

 WP1 - Seismology, Tectonics, Tilt, hydrology and vegetation analysis, deals with i) analysis of the background seismic noise wavefield and its role in the identification and monitoring of degassing sources and conduits; ii) response of MVs systems to earthquakes and links with regional tectonic structures; iii) tilt observations and their role in monitoring MVs activity; iv) hydrological regime and its influence on MVs activity; v) evolution of the river network as a consequence of MVs activity; vi) vegetation distribution as a marker of MVs evolution in space and time; vii) radio nuclides emissions by soil driven by MVs activity.

WP2 - Remote Sensing and Topography, performs remote sensing for terrain and surface modelling, aimed to identify deformation patterns related to changes in styles, amplitude and rates of MVs activity. It integrates ground data by GNSS with aerial surveys acquired by UAV, with the aim of identifying possible inflation/deflation cycles as proxies of MVs activity. In addition, historical documents and testimonies from the past will be collected and analysed for reconstructing events occurred also in the pre-instrumental era.

WP3 - Geochemistry, Stratigraphy and Rock Magnetism, aimed to measure flux/composition changes of emitted fluids as a proxy of MVs activity, and includes the study of active microbiological communities. Micropaleontological and stratigraphic study will be applied for depth determination of the mud source. The magnetic properties of mud and of the country rocks will be also studied.  

WP4 – Geophysics, is carrying out resistivity and magnetic surveys, for unravelling the geometry of buried structures.

WP5 - Scientific Outreach, manages the project website, produces multimedia material and performs risk education activities in schools.

How to cite: Madonia, P. and the The INGV-PROMUD team: The INGV-PROMUD Project: multidisciplinary monitoring of Mud Volcanoes , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15574, https://doi.org/10.5194/egusphere-egu24-15574, 2024.

EGU24-16796 | ECS | Posters on site | GMPV8.1 | Highlight

Exploring extreme environments at the Arctic seafloor: comprehensive studies integrating science, sustainability, and responsible resource exploitation  

Giuliana Panieri, Claudio Argentino, Alessandra Savini, Luca Fallati, and Eva Ramirez Llodra

The Arctic seafloor has emerged as a pivotal asset, playing a crucial role in fostering intensified exploitation activities and the incoming deep-sea mining industry, particularly in the so-called "extreme environments" where deep-sourced fluids reach the seafloor at hydrothermal vents and hydrocarbon seeps. Positioned as a promising frontier for resource extraction, exploring the Arctic seafloor is significant with the expanding reach of human exploitation. The ongoing reduction in sea ice coverage in the Arctic region facilitates resource exploration and opens up previously inaccessible areas for scientific investigation.

The paramount importance of comprehending the unique geological and ecological characteristics of the Arctic seafloor becomes evident in the quest for sustainable and responsible exploitation. As a response to this imperative, the integration of seafloor optical and acoustic seafloor and sub-seafloor imaging, and bio-geochemical analyses represents a pivotal approach. This integration allows the reconstruction of comprehensive models delineating geological processes, including the dynamics of hydrothermal and hydrocarbon systems.

This presentation aims to show the effectiveness of a multidisciplinary and multiscale approach in exploring extreme environments through a selection of case studies. Encompassing remote sensing, geochemistry, biology, and a range of seafloor imaging techniques, these studies highlight the complexity and unicity of these environments. Furthermore, we will show how those integrated studies equip both the public and policymakers with essential information, fostering a balanced approach that reconciles economic interests with environmental conservation in the realm of Arctic seafloor exploration.

How to cite: Panieri, G., Argentino, C., Savini, A., Fallati, L., and Ramirez Llodra, E.: Exploring extreme environments at the Arctic seafloor: comprehensive studies integrating science, sustainability, and responsible resource exploitation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16796, https://doi.org/10.5194/egusphere-egu24-16796, 2024.

EGU24-18259 | Posters on site | GMPV8.1

Inverse modelling as a powerful tool for gas flow emission rate estimation from stationary hydrothermal vents  (Vulcano Island, Aeolian archipelago, Italy) 

Gianluca Lazzaro, Agostino Semprebello, Salvatore Magazù, Maria Teresa Caccamo, Alessandro Gattuso, Domenico Traina, Sabina Morici, Cinzia Giuseppina Caruso, and Manfredi Longo

Submarine hydrothermal systems attract increasing interest from the scientific community, as they emit huge amounts of both elements and energy. However, in relation to their extreme environmental conditions (e.g. high temperature and pressure, low Ph) direct measurements can be challenging to perform.

In this context, passive hydroacoustics may represent a powerful technique for both short- and long-term monitoring as the typical source mechanisms of the hydrothermal fields, directly related to ascending fluids, radiate sound pressure following different acoustic modes.
Here we present preliminary results obtained by using a spectral approach for estimating the gas flow emission rate starting from the acoustic dataset collected between 22nd and 26th August 2022 on a stationary flux vent located at ~1.8 metres depth, inside the shallow hydrothermal field at Baia di Levante in Vulcano island (Aeolian Islands, Italy).

To carry out the estimation of the gas flow emission rate emitted by the hydrothermal vent, we implemented a customised inverse modelling algorithm based on a spectral method founded upon the assumption that the acoustic signature of a single bubble event evolves over time as a sinusoid that exponentially decays. According to this approach, we refined  the formulation of a forward model for the sound radiated by a stationary, high-flux  bubbles’ plume, then the path was backward analysed through the proposed inversion algorithm, which allowed us to obtain the estimated value of the flow emission rate.
High-resolution audio frames were recorded by using hydrophones [1 - 12800] Hz, that were deployed in the proximity of the investigated vent, collecting a total amount of  7  bursts of  ~10 hour-long each. 

Preliminary analyses of the Power Spectral Density (PSD) and Pressure Power Spectrum highlighted the presence of different persistent energetic frequency peaks over the environmental background noise coherently with the dynamics of the hydrothermal field. The most energetic ones, likely due to the acoustic signal radiated by a large, resonant bubble plume, consistently confirmed the coupling of the estimated radius with direct observations. 

The performed analysis allowed us to identify the main features of the vent, characterised by bubbles radii up to 0.03 m that produce the main energetic peak centred at ~100 Hz, along with smaller bubbles generating less energetic peaks up to 2 kHz. Therefore, the algorithm was set to work in a wide frequency range, spanning from 60 Hz to 2060 Hz, in order to estimate all the gas released by the vent.

The estimated flow emission rate  for the investigated period retrieved values spanning from 3.31 to 6.98 litres per minute, with a mean value of 4.97 litres per minute, in good agreement with the direct observations. These results confirm that passive acoustic methods represent a valid and robust tool for both monitoring and research activity in submarine hydrothermal fields, providing a long-lasting instrument able to detect the fluctuations connected to the variations of such natural systems.

How to cite: Lazzaro, G., Semprebello, A., Magazù, S., Caccamo, M. T., Gattuso, A., Traina, D., Morici, S., Caruso, C. G., and Longo, M.: Inverse modelling as a powerful tool for gas flow emission rate estimation from stationary hydrothermal vents  (Vulcano Island, Aeolian archipelago, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18259, https://doi.org/10.5194/egusphere-egu24-18259, 2024.

EGU24-21263 | ECS | Orals | GMPV8.1

Origin and composition of hydrothermal sediments at Aurora Vent Field, southern Gakkel Ridge (82.9°N) 

Claudio Argentino, Giuliana Panieri, Eivind Bjørnå, Pierre-Antoine Dessandier, Eva Ramirez-Llondra, and Stefan Buenz

The increasing number of active vents discovered worldwide, and new observations of basin-scale plumes suggest an underestimated role of hydrothermal systems in the ocean element cycling. This is especially true for slow-ultraslow spreading ridges which represent ca. 50% of the global mid-ocean ridge system and have only recently been recognized to host hydrothermal activity. Here, we present new data from sediment cores collected during HACON19 and HACON21 cruises at Aurora Vent Field, Arctic Ocean. We describe and interpret the hydrothermal signals recorded in the sediments at various distances from the active vents, based on core scanning (X-Rays, XRF, Multisensor scanner), and mineralogical and geochemical (XRF%) analyses on discrete samples. Metalliferous sediments surround the vents, with predominance of sulfide and (hydr)oxide minerals. Plume deposits are found several kilometers from the active vent, and their stratigraphic distribution in the longer gravity cores provided insights into the history and dynamics of vent activity since the last Ice age.

Acknowledgments: this research was supported by HACON project (Research Council of Norway grant No. 274330) and AKMA project (Research Council of Norway grant No. 287869).

How to cite: Argentino, C., Panieri, G., Bjørnå, E., Dessandier, P.-A., Ramirez-Llondra, E., and Buenz, S.: Origin and composition of hydrothermal sediments at Aurora Vent Field, southern Gakkel Ridge (82.9°N), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21263, https://doi.org/10.5194/egusphere-egu24-21263, 2024.

EGU24-21336 | Posters on site | GMPV8.1 | Highlight

Non-eruptive unrest and the role of magmatic brines, Vulcano, Italy. 

Matteo Lupi, Salvatore Alparone, Mimmo Palano, Tullio Ricci, Anthony Finizola, and Andrea Ursino

Although not all volcanic unrests lead to eruptions, it is generally accepted that magmatic activity is what causes volcanoes to awake. Alternatively, hydrothermal processes are often invoked to explain inflation and deflation dynamics. Magmatic brines have physical properties in between deep magmas and shallow hydrothermal fluids. Yet, to date we have no physical models accounting for geophysical signals that may be generated by the fluid flow of magmatic brines.

Vulcano, the southernmost island of the Aeolian Volcanic Archipelago, Italy, entered into unrest in September 2021. The island experienced intense ground deformation,  fumarole temperature and gas emissions increases, and a marked augmentation of seismicity.

For the first time since the deployment of broadband stations in 2005, very long period (VLP) seismic events were detected in the seismic records. Certain aspects of the geophysical signals recorded during the unrest are probably not fully compatible with traditional causal models involving fresh magma rising at depth or with a hydrothermal scenario.  In this contribution we discuss alternative scenarios and investigate whether fluid flow of magmatic brines may play a key role in understanding volcanic unrests.

How to cite: Lupi, M., Alparone, S., Palano, M., Ricci, T., Finizola, A., and Ursino, A.: Non-eruptive unrest and the role of magmatic brines, Vulcano, Italy., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21336, https://doi.org/10.5194/egusphere-egu24-21336, 2024.

EGU24-21768 | Posters on site | GMPV8.1

Multidisciplinary exploration for geofluids in small islands, the case study of the Formiche di Grosseto islets, Italy 

Chiara Del Ventisette, Domenico Montanari, Alessandra Sciarra, Adriano Mazzini, Marco Bonini, Franco Tassi, Federico Fischanger, Stefano Del Ghianda, Riccardo Lanari, Florence Begue, and Matteo Lupi

The Formiche di Grosseto are three islets, of about 1,500 m2, included in the Tuscan Archipelago, Italy. The islets rise abruptly from a seabed approximately 100 meters deep in correspondence of a structural high separating Neogene basins of the Tuscan Shelf. Onshore it is possible to observe hydrothermal breccias and speleothems. Offshore, CO2-rich submarine thermal fluids discharge from several springs with temperatures as high as 41°C. These submarine springs are mainly located along the Northern scarp at depths ranging from 6 to 32 m below the sea level.

To better understand the past and present nature of these fluid-driven systems extending offshore, a multidisciplinary exploration campaign was undertaken in the framework the TEMPEST and MIGRATE projects.

The main islet, offers a superb continuous outcrop of the Liassic carbonate rocks forming the backbone of the island.  Fault and fracture systems have been characterized across different scales to create a representative model. Multiple drone-flights have been performed to obtain an optical image for faults and fractures mapped over the islands. Drone-derived observations have been verified in the field and integrated in the structural model. Fractures and structural key geometries have been captured by means of a 2-D fracture network analysis with a circular sampling window. Connectivity within the fracture network have been parameterized by characterizing the different types of fracture terminations and intersections, which have been used to understand the structural architecture controlling the fluid flow. Rocks, hydrothermal breccias and calcitic precipitates have been analysed with cathodoluminescence and stable isotopes. Furthermore, a surface electrical resistivity (ERT) survey was carried out on the islet of Formica Grande di Grosseto - the main inslet - for the characterization of the subsoil up to 20-25 meters deep. The inversion shows a possible upflow of fluids, centred where the hydrothermal breccia has been found. Finally, CO2 diffuse-degassing soil flux measurements were also performed along these alignments.

The integrated study of the collected data pointed out that the northern part of the major islet is marked by upwelling of hot hydrothermal fluids. This was confirmed by a manual excavation that revealed rising thermal fluids - temperature of about 38°C- which was previously unknown on the island. Geochemical investigations have been conducted on the island's fluids, on the already known submarine thermal discharges as well as on the known thermal springs located inland, in the proximity of the Formiche di Grosseto area. 

The chemical compositions of the Formiche water samples are similar to those of seawater, although marked by significant enrichments of SO4, Ca and B and Mg depletion. These compositional characteristics are likely to be ascribed to the mixing of seawater with hydrothermal fluids. Our preliminary results aim to assess the origin of the discharged fluids and their relation with local and regional tectonics, providing an example of how multidisciplinary integrated exploration can be effectively conducted even in challenging contexts.

How to cite: Del Ventisette, C., Montanari, D., Sciarra, A., Mazzini, A., Bonini, M., Tassi, F., Fischanger, F., Del Ghianda, S., Lanari, R., Begue, F., and Lupi, M.: Multidisciplinary exploration for geofluids in small islands, the case study of the Formiche di Grosseto islets, Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21768, https://doi.org/10.5194/egusphere-egu24-21768, 2024.

EGU24-22432 | ECS | Orals | GMPV8.1 | Highlight

Development of a bio-indicator for extreme benthic ecosystem: the use of benthic foraminifera 

Clarisse Goar, Pierre-Antoine Dessandier, Giuliana Panieri, Erwan Roussel, Erwan Pelleter, Claudio Argentino, and Daniela Zeppilli

Here, we present data focusing on the diversity and ecology of benthic foraminifera from different hydrothermal vent fields on the Mid-Atlantic Ridge at low and high latitudes and mud volcanoes leaking methane. This study aims to understand the controlling factors ruling the communities’ structure, including environmental parameters (sediment nature, geochemical dynamic associated with seafloor massive sulfide areas) and food source (primary production and chemosynthetic microbial communities). This study aims to i) fulfil a lack of knowledge of hydrothermal vent biodiversity, ii) determine interactions between foraminifera and their ecosystem, and iii) establish a bio-indicator of extreme environments, environmentally dynamic.

We collected samples from two active vent sites, TAG and Snake Pit, in their periphery at low latitude and on the under-ice Aurora vent in the Arctic, showing contrasted mineralogy, pore water chemistry and organic matter compounds. The response of benthic foraminifera shows quite a stable community in the large periphery, while particular communities are observed in sediment with clear evidence of hydrothermal influence. For the mud volcano and active vents, a specific community of soft-body foraminifera and/or agglutinated species seems to be adapted to extreme environments, including species poorly known. Environmental data highlight a stronger impact of the habitat connected to microbial mats than organic matter availability. These preliminary results support the powerful use of benthic foraminifera in extreme environments to evaluate biodiversity and environmental changes but also highlight the need to improve the taxonomy of deep-sea soft-shelled foraminifera.  

How to cite: Goar, C., Dessandier, P.-A., Panieri, G., Roussel, E., Pelleter, E., Argentino, C., and Zeppilli, D.: Development of a bio-indicator for extreme benthic ecosystem: the use of benthic foraminifera, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22432, https://doi.org/10.5194/egusphere-egu24-22432, 2024.

EGU24-174 | ECS | Orals | GMPV8.2

Alteration and strength heterogeneity of the volcanic dome at La Soufrière de Guadeloupe (Eastern Caribbean) 

Agata Poganj, Michael J. Heap, and Patrick Baud

Hydrothermal alteration, which alters the chemical composition and physical state of volcanic rocks, can weaken a volcanic edifice, potentially leading to instability and collapse, thereby endangering the livelihoods of neighbouring residents. Instability scenarios can be modelled using large-scale numerical models, the accuracy of which depends on acquiring the physical and mechanical properties of volcanic rocks from laboratory measurements. Routinely, laboratory studies provide measurements for small sample suites (< 10) and, as a result, we do not fully grasp the range of rock properties that describe a particular unit or volume of the volcano, nor is it clear whether the few samples collected are representative. Here, we introduce a method that can help us select the most appropriate value, or range of values, for the physical and mechanical properties of volcanic rocks for large-scale numerical models.

We collected nearly 550 rocks from seven different sampling sites at La Soufrière de Guadeloupe, an active andesitic stratovolcano in the Eastern Caribbean. The rocks were assigned an alteration grade index, from 1 (least altered) to 5 (most altered), based on a visual assessment of their alteration. Their bulk densities were then measured in the field using the Archimedes method and, lastly, their strengths were measured using a point load tester, a field strength measuring apparatus. Alteration grade index ranges from 1 to 5 , bulk densities range from less than 1000 to 2700 kg/m3, and point load strength values span from 0.012 to 8.53 MPa . Point load strength and alteration distribution maps for the seven sampling locations show not only that rock physical properties vary greatly at an individual location, but also that the distributions of alteration and strength vary from place to place, highlighting the large heterogeneity of the dome at La Soufrière de Guadeloupe.

To calibrate these field data, we took small samples of the tested rocks back to the laboratory for porosity and uniaxial compressive strength measurements. Porosity measurements, ranging from 0.02 to 0.8, exhibited a strong correlation with field density values. The extremely altered rocks, deemed alteration grade index 5, despite having porosities ranging from 0.11 to 0.8, did not exceed point load strength of 2 MPa, suggesting that strength was not solely dependent on porosity. We also found that strength decreases as a function of increasing porosity and alteration grade index. Although uniaxial compressive strength tests revealed synchronicity with point load strength data, our current goal is to perform further tests to better constrain this relationship.

The point load test is a field method that can simplify the logistic problems behind strength assessments of volcanic domes, and likewise enlarge the sampling suite of individual studies. Calibrating field results to uniaxial compressive strength laboratory data will allow our data to be used in volcano stability models and accommodate direct conversion, from point load values to uniaxial compressive strength values, on-site. The potential abundance of available data, and spatial strength distributions, could make the large-scale models more realistic, and consequently more accurate and reliable.

How to cite: Poganj, A., Heap, M. J., and Baud, P.: Alteration and strength heterogeneity of the volcanic dome at La Soufrière de Guadeloupe (Eastern Caribbean), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-174, https://doi.org/10.5194/egusphere-egu24-174, 2024.

Rodingite is a calc-silicate rock containing garnet, diopside, and chlorite that develop via metasomatic replacement of ultramafic to felsic rocks. Rodingites are found in ophiolites subjected to low-grade metamorphism or hydrothermal serpentinization of the surrounding ultramafic rocks. Here we report a previously unrecognized volcanic environment for rodingite formation. Rodingites can result from skarn-like reactions between kimberlite and xenoliths of silicate country rocks.

We studied hypabyssal and pyroclastic kimberlites from Renard and Gahcho Kue clusters (Canada) and Orapa (RSA). The kimberlites entrain 20-90 vol.% of granitoid and gneiss (Renard 65, Gahcho Kue) and basalt (Orapa) xenoliths collectively called silicate country rocks. Skarn-like reactions triggered by gradients in the chemical potentials of Si, Al, Ca, and Mg across the xenolith–kimberlite contacts produce concentric reaction zones within the xenoliths and a reaction halo in the surrounding contaminated kimberlite. The original mineralogy of the unreacted xenoliths is replaced by prehnite, diopside, pectolite, wollastonite, serpentine, garnet, calcic hydrosilicates (hydrogarnet, xonotlite, amphiboles). In the kimberlite halo, diopside and phlogopite form, carbonate is leached out, olivine is completely serpentinized. Rodingites develop by moderate degrees of reaction, and are replaced with monomineral serpentine and chlorite if metasomatism advances further.

Petrographic evidence for post-emplacement, metasomatic development of rodingite assemblages in kimberlite matches the Perple_X phase equilibria calculations that model the formation of the reactive mineralogy in the subsolidus, at T<600oC. Mass transfer of major elements is demonstrated by bulk compositions, thermodynamic modelling, and conserved element ratio analysis. The xenoliths experience Si loss and gain of Ca and Mg; the opposite trends are observed in the adjacent kimberlite. A metasomatic rather than hydrothermal origin of the reactive mineralogy is suggested by the inability to model hydrogarnet and pectolite under fluid saturated conditions. The observed mineralogy is accurately reproduced only when H2O and CO2 are modelled as components controlled by the kimberlite composition.

Rodingite patches in kimberlites have many common characteristics with rodingites in ophiolites and serpentinites, i.e. 1) a wide range of protoliths; 2) a juxtaposition of different lithologies; 3) synchronicity with the proximal serpentinization; 4) local sources of elemental mass transfer; 5) a combination of desilication and Ca gain; 6) a low-T character; 7) a common replacement of garnet by hydrous sheet silicates in subsequent de-rodingization.

Rodingite formation in kimberlites is distinct from the classic rodingization in several aspects. In kimberlites, rocks of contrasting compositions are juxtaposed on the smaller scale creating centimeter-sized domains of rodingite mineralogy. An influx of H2O is not required, as the deuteric hydrous fluid is already in excess in the cooling kimberlite. In this environment, serpentinization is driven by the Si flux. Rodingites in kimberlites form at surface pressure. De-rodingization is not a result of gradually decreasing P-Ts, but is due to the continued mass transfer and cooling. Our observations suggest that hydration, serpentinization of clinopyroxene, decarbonation of marine sediments and moderate P= 3-6 kb are not pre-requisites for rodingite formation. A new geological environment of rodingite formation in kimberlites expands the range of parameters for rodingization.

How to cite: Kopylova, M.: A new geological environment for rodingite formation: Metasomatism in kimberlite volcanoes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2974, https://doi.org/10.5194/egusphere-egu24-2974, 2024.

Reductions to the permeability of a volcanic system can increase pore fluid pressure and, in turn, promote volcanic hazards such as erratic explosive behaviour and slope failure. Hydrothermal alteration, ubiquitous at volcanoes worldwide, is one mechanism thought to reduce permeability and therefore increase volcanic hazard potential. Turrialba, Poás, and Rincón de Vieja, active stratovolcanoes in Costa Rica, are characterised by erratic explosive behaviour thought to be the result of the formation, maturation, and rupture of hydrothermal seals that clog the conduit. To better understand this process, we present here a systematic study in which we assessed the textural, mineralogical, and physical properties of hydrothermal seals from Turrialba, Poás, and Rincon de Vieja volcanoes, ejected as ballistics following recent explosive activity. We first document the type and intensity of the hydrothermal alteration preserved in the collected ballistics using X-ray powder diffraction and scanning electron microscopy. All samples are characterised by pervasive acid-sulphate alteration. Prior to sample preparation, the permeability of these ballistics was first estimated using a TinyPerm III, a portable handheld air permeameter. We find that the hydrothermal seal is characterised by low values of permeability, between 10−15 and 10−13 m2. Cylindrical samples were then prepared for a systematic physical property (porosity, permeability, P-wave velocity, thermal properties, and mechanical strength) characterisation in the laboratory. These laboratory data, together with fluid flow modelling, highlight how alteration can create a low-permeability hydrothermal seal that promotes cyclic, but erratic, explosive volcanic behaviour.

How to cite: Heap, M., Avard, G., and Baud, P.: Hydrothermal sealing and erratic explosive behaviour at Turrialba, Poás, and Rincón de Vieja volcanoes (Costa Rica), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4420, https://doi.org/10.5194/egusphere-egu24-4420, 2024.

EGU24-4726 | ECS | Orals | GMPV8.2 | Highlight

Hydrothermally altered rocks of La Fossa, Vulcano island (Italy): Implications for flank instability from coupled drone photogrammetry and rock mechanical measurements 

Benjamin De Jarnatt, Thomas R. Walter, Michael J. Heap, Daniel Mueller, Julia Nikutta, and Antonino Fabio Pisciotta

Hydrothermal alteration is well recognized to change the physical and mechanical properties of volcanic rocks and promote instability and flank collapse. Here, we investigate La Fossa of Vulcano Island (Italy), the southernmost exposure of the Aeolian volcanic archipelago, and its associated regions of hydrothermal alteration. La Fossa’s accessibility, altered flanks, history of mass wasting events, and periods of escalating fumarole activity set an ideal environment for a natural laboratory. We used drone remote sensing methods coupled with field and ongoing laboratory rock property measurements to classify regions of hydrothermal alteration and assess their associated rock properties. Our results have (1) identified a heterogenous distribution of alteration intensity and alteration types, (2) distinguished a relationship between decreasing rock strength and increasing alteration, and (3) correlated regions with the weakest rock strength with hydrothermally altered flanks. This combined approach allows us to explore the relationships between hydrothermal alteration, rock strength, and flank instability of La Fossa. 

How to cite: De Jarnatt, B., Walter, T. R., Heap, M. J., Mueller, D., Nikutta, J., and Pisciotta, A. F.: Hydrothermally altered rocks of La Fossa, Vulcano island (Italy): Implications for flank instability from coupled drone photogrammetry and rock mechanical measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4726, https://doi.org/10.5194/egusphere-egu24-4726, 2024.

Reactions between aqueous fluids and rocks result in secondary mineral formation – alteration – that can block permeable pathways in the Earth’s crust and change the hydraulic properties of geological systems. The propensity, extent, and timescales of rock alteration are therefore important controls on crustal permeability. However, understanding the intricate relationships that result in rock alteration and changes in permeability - including dissolution, transport, and redistribution of chemical compounds - represents a technical challenge and remains a key unsolved problem in the Earth sciences. As a result, we do not fully understand how these processes modify the structure of permeable channels and over what timescales they may hamper crustal fluid flow, limiting, for example, our ability to effectively model the efficiency of geothermal reservoirs or forecast volcanic eruptions. The SNSF-funded ReSiDue project – Redistribution of Silica and Deposition under a volcanic edifice - addresses how the redistribution of the most common compound in the Earth’s crust - silica (SiO2) - changes the permeability of rocks under volcanically relevant conditions. Silica alteration is ubiquitous in volcanic systems and results in changes to rock structure and thus hydraulic properties. However, the processes that lead to silica alteration remain understudied, especially at high temperatures, because they involve complex feedbacks between fluid-rock interactions and petrophysics. Using a mix of detailed petrophysical, microstructural and geochemical characterization, and water-rock interaction experiments, we are quantifying 1) the physical and chemical conditions promoting silica alteration in volcanic edifices, 2) how fluid-flow pathways in rocks change over time as a result of silica alteration, 3) how these changes modify permeable flow, and 4) on what timescales these processes are active. The newly operational High temperature Reactive flOw permeabiLity Device – HAROLD – allows for in situ monitoring of permeability evolution over time, during reactive flow. This apparatus can operate at temperatures up to 500°C and confining and pore fluid pressures of 100 MPa and 20 MPa, respectively, allowing us to target conditions relevant to volcanic edifices and shallow geothermal reservoirs. This systematic understanding of how silica alteration changes the permeability of volcanic rocks will help refine volcanic outgassing models, with potential application to risk assessment and hazard mitigation efforts. However, beyond volcanology, this project sets the infrastructural, experimental and analytical foundation needed to more broadly study the relationships between rock-fluid interactions and crustal fluid flow, including in geothermal systems.

How to cite: Kushnir, A., Mikaelian, C., and Mazzeo, A.: ReSiDue: A coupled rock physics and geochemical approach to understanding how rock-fluid interactions change permeability in volcanic systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4729, https://doi.org/10.5194/egusphere-egu24-4729, 2024.

EGU24-5415 | Posters on site | GMPV8.2

Concealed hydrothermal alteration zones provide mechanical weaknesses within lava domes 

Valentin Troll, Thomas R. Walter, Herlan Darmawan, Michael J. Heap, Claire E. Harnett, Frances M. Deegan, Nadhirah Seraphine, Harri Geiger, and Daniel Müller

Catastrophic lava dome collapse is considered an unpredictable volcanic hazard because the physical properties, stress conditions, and internal structure of lava domes are not well understood. To better explain the locations of recent dome instability events at Merapi volcano, Indonesia (1), we combined geochemical and mineralogical analyses, rock physical property measurements, drone-based photogrammetry, and numerical modelling. We show that a linear fissure and a horseshoe-shaped alteration zone that formed in 2014 was buried by lava extrusion in 2018. The linear fissure controlled the location of the new lava dome, while the horseshoe shaped zone influenced subsequent instability. Geomechanical, mineralogical, and geochemical data suggest that such alteration zones are characterised by mechanically weak, hydrothermally altered materials, and we show that the new lava dome is collapsing along this now-hidden horseshoe shaped and comparatively weak alteration zone (2). To derive an improved general understanding of this phenomenon, we then combined recent laboratory data for the mechanical behaviour of dome rocks with discrete element method models to show that the presence of weak zones within lava domes increases instability, which is exacerbated when the size of the zone increases or when the zone is positioned off-centre (3). Our results highlight that improved understanding of dome architecture and compositional variations due to hydrothermal alteration within domes is essential for assessing hazards associated with dome and edifice failure at volcanoes worldwide.

How to cite: Troll, V., Walter, T. R., Darmawan, H., Heap, M. J., Harnett, C. E., Deegan, F. M., Seraphine, N., Geiger, H., and Müller, D.: Concealed hydrothermal alteration zones provide mechanical weaknesses within lava domes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5415, https://doi.org/10.5194/egusphere-egu24-5415, 2024.

EGU24-5948 | Orals | GMPV8.2

Hydrothermal alteration of lava domes: coupled contribution of experimentation and thermodynamic modelling 

Caroline Martel, François Décossin, Laurent Arbaret, Rémi Champallier, Michael Heap, Marina Rosas-Carbajal, and Jean-Christophe Komorowski

Flank collapse represents a significant hazard at explosive volcanoes. Hydrothermal alteration is considered to promote volcano instability, but there are few data and models to robustly assess this hypothesis. In the framework of the Mygale ANR project, a multidisciplinary approach that combines geological data, geophysical and geochemical techniques, laboratory measurements, and modelling is proposed to assess the role of alteration on the stability of La Soufrière de Guadeloupe (France). We focus here on the benefit of combining time-series and flow-through experiments with thermodynamic and kinetic modelling for constraining the alteration process below the lava dome of La Soufrière. Flow-through experiments under pressure and temperature provide in-situ permeability data during ongoing alteration of pristine andesite. Thermodynamic modelling is essential for evaluating the fluid phase composition driving rock alteration at depth. Kinetic modelling is precious for predicting the alteration sequence on timescales longer than experimentally achievable. Eventually combining such geophysical and geochemical data on natural and experimental samples will allow to propose a large-scale 4D numerical model to assess the influence of alteration on volcano stability and improve monitoring of volcano instability.

How to cite: Martel, C., Décossin, F., Arbaret, L., Champallier, R., Heap, M., Rosas-Carbajal, M., and Komorowski, J.-C.: Hydrothermal alteration of lava domes: coupled contribution of experimentation and thermodynamic modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5948, https://doi.org/10.5194/egusphere-egu24-5948, 2024.

EGU24-6347 | ECS | Posters on site | GMPV8.2

ROTTnROCK: a new ERC project to investigate the influence of hydrothermal alteration on volcano instability, eruption triggers and fault reactivation 

Claire Harnett, Michael Heap, Valentin Troll, and Thomas Walter

Hydrothermal alteration gradually and imperceptibly changes the chemical and physical state of the rocks inside a volcano, creating a soft and unstable (or 'rotten') interior. However, the link between 'soft' volcanoes and unpredictable volcanic events remains poorly resolved. ROTTnROCK is a 6-year ERC project, running from 2024-2030, funded through the European Research Council's Synergy Call. The growing ROTTnROCK team will investigate the role of hydrothermal alteration in unpredictable volcanic hazards, such as volcanic instability, alteration-induced eruption triggering, and caldera fault (re-)activation. Specifically, we will use remote sensing and geophysics to identify where and at what scales alteration is occurring. Laboratory investigations will study the chemical fingerprint of alteration and its effects on rock mechanical properties and strength. These approaches will be coupled with 4D volcano stability simulations to produce an innovative and optimised hazard assessment workflow. We will work at selected target sites that show evidence of strong hydrothermal alteration, either associated with flank collapse, collapsing lava domes, crater lakes, or active collapse calderas. This project will transform our understanding of hydrothermal alteration and its impact on volcanic hazards, and will pave the way for strategies to predict and mitigate unexpected volcanic events caused by hydrothermal alteration.

How to cite: Harnett, C., Heap, M., Troll, V., and Walter, T.: ROTTnROCK: a new ERC project to investigate the influence of hydrothermal alteration on volcano instability, eruption triggers and fault reactivation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6347, https://doi.org/10.5194/egusphere-egu24-6347, 2024.

EGU24-6565 | ECS | Posters on site | GMPV8.2

Investigating hydrothermal alteration in Copahue volcano (Argentina/Chile) using muography and laboratory measurements on rock samples 

Matias Tramontini, Marina Rosas-Carbajal, Fabio I. Zyserman, Pascale Besson, Jacques Marteau, and Michael Heap

Muography is a non-invasive geophysical method that relies on the detection of muons, which are subatomic particles generated by the interaction of cosmic rays with the Earth's atmosphere. The physical quantity estimated by this method is the opacity, which represents the amount of matter traversed by muons along their trajectories, resulting in energy loss and scattering for the particles. Thus, absorption muography consists of deploying a muon detector targeting the volcano and registering the muons traversing it per unit of time and trajectory. From these data, radiographs of average density of extensive rock volumes can be obtained using a single measuring instrument and from a singular measurement position.

Copahue volcano is located in the Andes mountain range and is considered the highest-risk volcano in Argentina due to its proximity to two towns situated within an 8 km radius of the volcano's crater. Additionally, the region attracts a significant number of tourists, leading to a substantial increase in the population of both localities. The latest eruptive cycle, initiated in 2012, has maintained a near-continuous state of activity, marked by ash emissions, crater explosions, and seismic activity. In this work, we study the hydrothermal alteration at Copahue volcano through a combination of muography and laboratory measurements of the chemical and physical properties of rock samples.

The muography dataset was acquired by installing a muon detector on the eastern flank of Copahue volcano, situated at an altitude of approximately 2500 meters above sea level. For the laboratory analyses, we collected rock blocks with the objective of representing a diverse spectrum of alteration stages within Copahue volcano. Through this selection process, we captured variations in mineralogical composition, geochemical signatures, and physical properties that correspond to different stages of hydrothermal alteration. We carried out a series of examinations on the rock samples extracted from the targeted flank, such as X-ray diffraction (XRD) and inductively coupled plasma mass spectrometry (ICP-MS) analyses that identified mineralogical compositions and geochemical signatures associated with hydrothermal processes. We also carried out additional measurements, including density, porosity, permeability, thermal properties, and uniaxial compressive strength, contributing to a comprehensive understanding of the physical properties of the samples. In addition, we performed microscopic examinations using a scanning electron microscope (SEM) to study the microstructural changes induced by hydrothermal alteration. This integrative approach, between muography and detailed laboratory measurements on rock samples, aims to reveal correlations between subsurface density variations and hydrothermal alteration observed at the microscopic and macroscopic scales.

How to cite: Tramontini, M., Rosas-Carbajal, M., Zyserman, F. I., Besson, P., Marteau, J., and Heap, M.: Investigating hydrothermal alteration in Copahue volcano (Argentina/Chile) using muography and laboratory measurements on rock samples, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6565, https://doi.org/10.5194/egusphere-egu24-6565, 2024.

EGU24-6858 | Orals | GMPV8.2 | Highlight

Linking hydrothermal alteration and volcanic rock mechanics through VNIR-SWIR spectroscopy   

Maia Kidd, Gabor Kereszturi, Michael Heap, Ben Kennedy, and Jonathan Procter

Volcanoes are dynamic and complex natural systems, constantly changing through eruptions, alteration, and erosion. Hydrothermal systems are ubiquitous on volcanoes, causing physical and mechanical change to rock properties via hydrothermal alteration. The most commonly measured rock physical properties are porosity and uniaxial compressive strength (UCS) as they provide insight as to their history and potential mechanical behavior. Porosity and UCS are affected by the primary properties and emplacement history (e.g., volatile content, crystallinity, cooling rate, composition, fragmentation type) and the post-emplacement conditions (e.g., surface weathering and hydrothermal alteration). This creates highly heterogenous rock masses, with variation occurring across mm to m scales. Currently, destructive testing is required to measure UCS and porosity (destructive of the wider sample) accurately and needs a large volume of samples to capture the heterogeneity of volcanic rock masses. This testing is cost and time prohibitive, requiring large sample volume, in terms of sample size and number, which often require shipping to specialist labs. Schmidt hammers can be used to estimate UCS non-destructively, however, they produce inaccurate results on soft rocks such as hydrothermally altered rocks. Here, we present a new non-destructive method for predicting porosity and UCS across a range of volcanic rocks, from non-altered to highly altered.

This study uses visible-near infrared (VNIR) to shortwave infrared (SWIR) wavelengths (350-2500 nm) reflectance spectroscopy to predict porosity and UCS via Partial Least Squares Regression (PLSR). Reflectance spectroscopy is a non-destructive method that is sensitive to both physical (surface roughness and crystal/particle size) and chemical (mineral species and abundance) properties of volcanic rocks. Because these rock attributes also influence the physical and mechanical properties of rock, reflectance spectroscopy could be used to quantitatively predict porosity and UCS. This study used experimentally deformed volcanic rocks from Ruapehu, Ohakuri, Whakaari, and Banks Peninsula (New Zealand), Merapi (Indonesia), Chaos Crags (USA), Styrian Basin (Austria), La Soufrière de Guadeloupe (Eastern Caribbean), Volvic (France), and Cracked Mountain (Canada) to evaluate the accuracy of PLSR-based predictions for porosity and UCS. The training samples encompass a wide range of volcanoes, alteration degree (non-altered, silicic, argillic, and phyllic alteration), mineralogical differences (initial composition from basalt to rhyolite and alteration products), and textural differences (original textures such as lava and pyroclastic, and alteration textures including veins). Model sensitivity is evaluated by adding randomly individual samples to the training database or performing leave one group out cross validation based on characteristics (e.g., alteration mineral types, textural features, or volcano location). From this analysis, specific alteration mineralogy can be evaluated for its effect on porosity and UCS predictions such as the role of phyllosilicate formation causing a reduction in UCS. The proposed non-destructive method via VNIR-SWIR spectroscopy can complement existing rock mechanical testing methods to better quantify highly heterogenous volcanic and hydrothermal systems and their rock successions.

How to cite: Kidd, M., Kereszturi, G., Heap, M., Kennedy, B., and Procter, J.: Linking hydrothermal alteration and volcanic rock mechanics through VNIR-SWIR spectroscopy  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6858, https://doi.org/10.5194/egusphere-egu24-6858, 2024.

EGU24-7009 | Orals | GMPV8.2

Vertical and lateral changes of hydrothermal alteration in andesitic composite volcanoes – Linking flank collapse with hydrothermal activity 

Gabor Kereszturi, Antonio M. Álvarez-Valero, Nessa D’Mello, Mercedes Suárez Barrios, Rachelle Sanchez, Craig Miller, and Daniel A. Coulthard

Andesitic composite volcanoes located at convergent plate margins can host extensive zones of hydrothermally altered rocks, which can influence their rock mechanics and potentially modulate eruptive activity. Hydrothermal minerals typically form along fractures and permeable zones above cooling and degassing magma bodies. A robust understanding of the vertical and lateral distribution of hydrothermal minerals can therefore reveal the location of (former) magma bodies/fluid source and can indicate areas susceptible for future flank collapse processes.

This study investigates the type and extent of hydrothermal alteration within the Wahianoa Formation (160-80 ky) of Ruapehu volcano in New Zealand by integrating field observations, Scanning Electron Microscopy (SEM-EDS), Shortwave Infrared (SWIR) reflectance spectroscopy, X-Ray Diffraction (XRD), sulfur isotope systematics and Inductively coupled plasma mass spectrometry (ICP-MS), thermodynamic modelling and airborne geophysics. Ruapehu shows a diverse suite of weathering and hydrothermal alteration minerals formed in relation to the present and fossil hydrothermal systems. Wahianoa Formation is one of the oldest formations, showing remarkable diversity of hydrothermal alteration that has never been studied before. The distal rock has only supergene alteration with abundant goethite, hematite and phyllosilicate mineral associations, while the hydrothermally altered rock are rich in phyllosilicates, Fe-oxides, pyrite, jarosite, alunite, gypsum anhydrite, and native sulphur. The latter is interpreted to be formed under intermediate and advanced argillic alteration conditions (>150 °C and low pH). In contrast, the some of the exposed outcrops within the upper Wahianoa valley show distinct mineralogy, that is rich in quartz, pyrite, illite(-chlorite) and tourmaline, indicating a transition from the advanced argillic conditions toward more phyllic alteration type (>220 °C and more neutral pH). Our results indicate a complex hydrothermal system developed within the Wahianoa Formation between 150-80 ky, providing a great example to study vertical and lateral mineralogical changes. A new model has been proposed to integrate hydrothermal alteration history into the Mt Ruapehu’s evolution that can better depict ongoing alteration processes and triggers for flank instability and volcanic hazards associated hydrothermal systems.

How to cite: Kereszturi, G., Álvarez-Valero, A. M., D’Mello, N., Suárez Barrios, M., Sanchez, R., Miller, C., and Coulthard, D. A.: Vertical and lateral changes of hydrothermal alteration in andesitic composite volcanoes – Linking flank collapse with hydrothermal activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7009, https://doi.org/10.5194/egusphere-egu24-7009, 2024.

EGU24-9520 | ECS | Posters on site | GMPV8.2

Imaging hydrothermal alteration with electrical resistivity tomography in La Soufrière de Guadeloupe volcano 

Aida Mendieta, Marina Rosas-Carbajal, Raphaël Bajou, Patrick Baud, Sébastien Deroussi, Tomaso Esposti Ongaro, Jean-Christophe Komorowski, Alexandra R.L. Kushnir, Marlène Villeneuve, and Michael J. Heap

Hydrothermal alteration plays a major role in volcanic instability. Improving techniques that allow us to better understand the timescales of alteration in active volcanoes is thus paramount. Since the reactivation of the fumarolic field at the top of the dome of La Soufrière de Guadeloupe (Guadeloupe, France) in 1992 and the expansion of its surface area in recent years, the area of study is subjected to prolonged variable alteration that has promoted past flank collapses and can also influence permeability and thus shallow depth overpressurization. During a field campaign in May 2022 we performed 25 electrical resistivity tomography (ERT) profiles in the summit of La Soufrière, next to active fumaroles and acid boiling ponds. These ERT profiles were inverted using the open-source code pyGIMLi. Thanks to the ERT profiles we are able to roughly map the altered areas to a depth of about 20 m in this zone of La Soufrière. Some of the byproducts of alteration that have been identified in La Soufrière are clays, sulfates and pyrite. Thus, we infer that the low electrical resistivity zones (<20 Ωm) correspond to alteration and high electrical resistivity (>1500 Ωm) corresponds to unaltered rock. Low electrical resistivity anomalies are observed north of the Breislack fault, near the fumaroles. The explored north-most region is characterized by higher values of electrical resistivity. We take into account ground temperature and spatial variability to interpret the electrical conductivity anomalies and we use this first high-resolution resistivity model to plan a repetition of our experiment. This time-lapse experiment will allow us to estimate the evolution of hydrothermal alteration in the volcano’s summit over a 2-year period in the context of the current ongoing multiparameter unrest.

How to cite: Mendieta, A., Rosas-Carbajal, M., Bajou, R., Baud, P., Deroussi, S., Esposti Ongaro, T., Komorowski, J.-C., Kushnir, A. R. L., Villeneuve, M., and Heap, M. J.: Imaging hydrothermal alteration with electrical resistivity tomography in La Soufrière de Guadeloupe volcano, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9520, https://doi.org/10.5194/egusphere-egu24-9520, 2024.

EGU24-9869 | ECS | Posters on site | GMPV8.2

Hydrothermal fluid circulation at La Soufrière de Guadeloupe inferred from soil CO2 degassing, thermal flux, and self-potential 

Amelie Klein, David E. Jessop, Franck Donnadieu, Joanny Pierre, and Roberto Moretti

Quantifying subsurface fluid circulation and the associated heat and gas fluxes provides crucial clues for interpreting the evolution of volcanic unrest in volcanoes with active hydrothermal systems. To better constrain the distribution of current hydrothermal activity on La Soufrière de Guadeloupe, we conducted repeated mapping of diffuse ground CO2 degassing, ground temperature, and self-potential on the dome summit in 2022-2023.

We produced maps by interpolating these data, which allowed us to identify areas of fluid recharge into the hydrothermal system and the areas of ascending hydrothermal flows. We were also able to quantify the convective and conductive ground heat fluxes and the area affected by ground heating.

Our measurements allowed us, for the first time, to quantify the ground CO2 flux of the dome, estimate the condensation depth of ascending fluids, and relate it to soil permeability. We found diffuse ground CO2 degassing corresponds to about half of the CO2 emissions from the summit fumaroles.

Further, we performed continuous self-potential measurements at the summit to analyse the temporal variability of underground fluid fluxes. The combination of these measurements and comparison with high-resolution thermal images taken in recent years allows us to track the spatial and temporal evolution of the shallow hydrothermal fluid circulation. Moreover, we were able to constrain the controlling factors of the observed changes in the surface manifestations in the NE sector of the summit, where a fumarole field has been developing since 2012. Our results imply that monitoring soil degassing and ground temperature gradients can enhance understanding of the sealing state of the dome, which is crucial for assessing potential hazards linked to fluid pressurisation.

How to cite: Klein, A., Jessop, D. E., Donnadieu, F., Pierre, J., and Moretti, R.: Hydrothermal fluid circulation at La Soufrière de Guadeloupe inferred from soil CO2 degassing, thermal flux, and self-potential, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9869, https://doi.org/10.5194/egusphere-egu24-9869, 2024.

EGU24-12269 | Posters virtual | GMPV8.2

Discovery of the “Lucky B” ultramafic-hosted hydrothermal field in the ultraslow-spreading Lena Trough, Arctic Ocean 

Elmar Albers, Felix Genske, Lilian Böhringer, Jessica N. Fitzsimmons, Shelby Gunnells, Tea Isler, Jonathan Mette, Jeffrey S. Seewald, Maren Walter, Gunter Wegener, Christopher R. German, and Vera Schlindwein and the R/V Polarstern PS137 Science Team

Deep-sea hydrothermal systems are particularly difficult to locate and investigate in the ice-covered Arctic Ocean. Here we report findings of a system in the ultraslow-spreading Lena Trough at 81°22’N, from Expedition PS137 of the icebreaker R/V Polarstern in the summer of 2023. The site, named ‘Lucky B’, was first discovered after the recovery of massive sulfides in a dredge haul in 1999 (Snow et al., 2001) on the western flank of the Lucky Ridge, a 130 km-long ultramafic topographic high.

We investigated the buoyant and non-buoyant parts of Lucky B’s hydrothermal plume making use of physical sensors and geochemical hydrothermal tracers. The non-buoyant plume was found at approx. 300–400 m above the seafloor and was characterized by high turbidity and pronounced anomalies in oxidation–reduction potential and temperature (up to ~80 mV and 0.02°C, respectively). In its buoyant part, the plume contained high dissolved H2 (~450 nmol/L) and CH4 (~250 nmol/L).

Our seafloor observations, using deep-sea robotics, revealed widespread traces of hydrothermal activity at approx. 3,000–3,300 m water depth. These included hydrothermally discolored rocks and sediment and local outflow of clear hydrothermal fluids with abundant macrofauna. Guided by our discoveries, follow-on operations with the Norwegian icebreaker R/V Kronprins Haakon resulted in ROV dives to a large black smoker vent field with a number of several m-high chimneys. The visual appearance of the suggests vent fluid temperatures similar to those of other high-temperature ultramafic-influenced systems (e.g., 365°C at Rainbow; Charlou et al., 2002).

Confirmation awaits comparison with ongoing analyses of hydrothermal plume samples (He isotope signatures, Fe and Mn concentrations, CH4:Mn ratios) and of sulfide chimneys dredged in 1999 (mineral assemblages).

In the Arctic, Lucky B is the first hydrothermal system that has been traced to its seafloor source that is associated with ultramafic rocks outcropping at the seafloor. Additional work will be required to conceive its role on biogeochemical cycles in the ice-covered ocean.

How to cite: Albers, E., Genske, F., Böhringer, L., Fitzsimmons, J. N., Gunnells, S., Isler, T., Mette, J., Seewald, J. S., Walter, M., Wegener, G., German, C. R., and Schlindwein, V. and the R/V Polarstern PS137 Science Team: Discovery of the “Lucky B” ultramafic-hosted hydrothermal field in the ultraslow-spreading Lena Trough, Arctic Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12269, https://doi.org/10.5194/egusphere-egu24-12269, 2024.

Ionization of water and speciation of aqueous electrolytes exerts important control on chemical composition, acid-base interaction, and fluid-mineral equilibria in hydrothermal systems. Several competing approaches are available to describe H2O, HCl and NaCl speciation under hydrothermal conditions: (i) electrostatic models using the Born theory (Tanger and Helgeson 1988; Shock et al. 1992, Djamali and Cobble 2009), (ii) semi-empirical correlations with H2O density (Marshall and Franck 1981, Mesmer et al. 1988, Holland and Powell 1998); (iii) hydration models (Pitzer 1982; Tanger and Pitzer 1989) and (iv) diverse theoretical models (e.g., Akinfiev and Diamond 2003, Lvov et al. 2018). Available models were compared to experimental data (n = 606) covering temperature from 0 to 800 °C and pressure of 1 to 8000 bar, with several measurements up to 1000 °C and 133 kbar. Various approaches consistently and accurately reproduce the experimental H2O ionization up to 400 °C and above 300 bar. By contrast, at higher temperatures or lower pressures the models substantially diverge and reveal conceptual deficiencies. For HCl dissociation, the electrostatic, density and virial models are accurate to 400 °C and 1500 bar, at higher temperatures remain consistent but rapidly inaccurate and at higher pressures they diverge. This critical evaluation identifies density models as most promising for formulating new equation of state for ionic species. Here we combine individual thermodynamic contributions representing intrinsic species properties, mechanical and electrostatic solute-solvent interaction during hydration, and standard-state conversion term. We use the experimental datasets for H2O, HCl and NaCl ionization to evaluate the performance and accuracy of optional functional forms for heat capacity, hydration compression and its coupling to the standard-state conversion term. Our preliminary results indicate that intrinsic enthalpy, entropy and volume coupled with heat capacity linearly dependent on temperature, compression and standard-state conversion terms, without involvement of electrostatic contribution or chemical hydration afford the most accurate description of thermodynamic properties of ionic species. This model provides basis for accurate prediction and modeling of mineral-fluid and melt-fluid equilibria in upper-crustal magmatic and hydrothermal systems.

References

Akinfiev N.N., Diamond L.W. (2003) Geochim. Cosmochim. Acta 67, 613-627.

Djamali E., Cobble J.W. (2009) J. Phys. Chem. 113, 2398-2403.

Lvov S.N. et al. (2018) J. Molecul. Liq. 270, 62-73.

Marshall W.L., Franck E.U. (1981) J. Phys. Chem. Ref. Data 10, 295–304.

Pitzer K.S. (1982) J. Phys. Chem. 86, 4704-4708.

Shock E.L. et al. (1992) J.  Chem. Soc. Faraday Trans. 88, 803-826.

Tanger IV J.C., Helgeson H.C. (1988) Am. J. Sci. 288, 19-98.

Tanger IV J.C., Pitzer K.S. (1989) J. Phys. Chem. 93, 4941-4951.

How to cite: Salomone, F. and Dolejš, D.: Critical evaluation and development of thermodynamic models for ionization of H2O, HCl and NaCl at high temperatures and pressures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15937, https://doi.org/10.5194/egusphere-egu24-15937, 2024.

EGU24-16537 | ECS | Orals | GMPV8.2 | Highlight

Subsurface soil and lithology alteration shaping degassing at Krafla caldera, Iceland 

Roberto Davoli, Katharina Engels, Cristian Montanaro, Tullio Ricci, Alessandra Sciarra, and Bettina Scheu

Alteration by rock-fluid interaction can significantly impact rock and soil properties influencing fluid flow within hydrothermal aquifers, and shaping surface features and degassing in geothermal settings over time. Hence, the understanding of the spatial distribution of thermal manifestations in correlation with the geological setting and alteration type remains essential for unravelling the processes controlling the transport of fluids from within the hydrothermal aquifers to the surface.

Previous studies focused on the effect of alteration within hydrothermal aquifers on a scale of hundreds of meters. In contrast, limited research has explored the influence of subsurface lithologies – including their intrinsic and altered permeability – and their spatial distribution on degassing activity. This study examines subsoil portions across the active geothermal fields of Krafla caldera in Iceland, to explore the relationship between various soils/lithologies and primary degassing areas. In particular, we investigate how hydrothermal alteration influences the petrophysical characteristics of these lithologies, thereby modulating surface-level fluid circulation.

In two field campaigns carried out in 2022 and 2023, we assessed the in situ petrophysical properties of over 200 samples across 22 sites in the Víti and Hveragil regions. Moreover, we conducted subsoil diffuse CO2 flux measurements for specific profiles. Field permeability ranged from 10-11 to 10-16 m2, with CO2 fluxes varying between 1.25 to 2628.33 g/m2 day. Additionally, we examined the grain size distribution and the componentry of selected subsoil layers.

Our findings delineate the presence of both active (thermal) and inactive (non-thermal) regions, depicting the variable impact of hydrothermal alteration on the subsoil properties. In active geothermal sites, the dominance of mineral dissolution/replacement facilitates the formation of preferential pathways for fluid flow. Within inactive areas, mineral cementation of pores and fractures appears to act as barriers to fluid movement. These outcomes offer crucial insights for comprehending and quantifying the effect of hydrothermal alteration on fluid dynamics, shedding light on the progression of surficial manifestations and degassing patterns within active geothermal areas.

How to cite: Davoli, R., Engels, K., Montanaro, C., Ricci, T., Sciarra, A., and Scheu, B.: Subsurface soil and lithology alteration shaping degassing at Krafla caldera, Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16537, https://doi.org/10.5194/egusphere-egu24-16537, 2024.

EGU24-16850 | ECS | Orals | GMPV8.2

Hydrothermal alteration at the Tolfa volcanic district (Latium, Italy): texture, mineral and isotope chemistry 

Germano Solomita, Francecsa Corrado, Giuseppina Balassone, Nicola Mondillo, Angela Mormone, Harald Strauss, and Monica Piochi

The Tolfa volcanic district (TVD, Latium, Central Italy) is an extinct hydrothermal setting where the effect of fluid-rock interactions can be studied also as a key to unravel the processes taking place in active volcanic systems. TVD is characterized by a sulfate alteration associated with a pervasive deposition of opaline and/or microcrystalline silica, consisting of mineral replacements, veins and agate druses, and argillic facies in the pre-existing volcanic host rocks (Conte et al., 2022; Lombardi and Sheppard 1977; Marchesini et al., 2023).

The TVD hydrothermal alteration products have received attention in the previous literature with some petrographic and isotopic studies of sulfates and clay minerals, as well as scattered and incomplete rock and fluid geochemistry (Cinti et al., 2011; Lombardi and Sheppard 1977). These early studies, however, suggest that TVD is of particular interest in terms of both alteration and mineralization features.

This study is part of a bigger project on the Allumiere-Tolfa district and focuses on the aluminium sulfate and kaolinite-rich deposits of the Tolfa hydrothermal alteration area, deepening the investigation of the processes that generated the alteration materials. We conducted a field campaign at Tolfa and Allumiere and in several surrounding localities up to the Santa Severa mountains. Various collected samples have been analyzed by integrating different techniques: X-ray diffraction (XRD), scanning electron microscopy with microanalysis by energy-dispersive spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FT-IR), whole-rock geochemistry and stable O- and S- isotope geochemistry.

The mineralogical analyses show a wide morphological and compositional variability of the sulfates mineralization. An alunite group mineral occurs as solid solutions. We identified natroalunite as well as walthierite, usually characterized by lamellar/tabular and pseudocubic habits; instead, alluminium-phosphate–alunite (APA) is present as pseudocubic crystals. Kaolinite group minerals have been also detected and, in particular, kaolinite is widespread, occurring in well-shaped grains, often in vermicular packages. Quartz is abundant in most of the samples, associating to alunites. Fe-Ti oxides contain Cr, V, Ni. Alunite can be characterized for high Ba or Sr content and a distinct P-rich core. The ẟ34S varies between 1.2 and 10.3‰ and the ẟ18O between -5.7 and 11.7‰, depending on mineral type. The preliminary data collected are useful (i) to improve the knowledge of mineral chemistry of these deposits and to characterize in detail alunite and kaolinite minerals; (ii) to constrain the sulfate mineralizations by the hydrothermal fluids, (iii) to have a background for the investigation of mineralization zones and processes, and (iv) to compare this case study with hydrothermal alteration and processes from extinct and quiescent volcanic districts, such as Campi Flegrei and Ischia in Campania.

Cinti D et al. (2011).  Chemical Geology 284, no. 1-2: 160-181.

Conte A. et al. (2022). Physics and Chemistry of Minerals, 49(10), p.39.

Lombardi G., Sheppard S.M.F. (1977) Petrographic and isotopic studies of the altered acid volcanics of the Tolfa-Cerite area, Italy: the genesis of the clays. Clay Miner 12(2):147–162.

Marchesini B. et al. (2023) Structural control on the alteration and fluid flow in the lithocap of the Allumiere-Tolfa epithermal system. Journal of Structural Geology, 105035.

 

How to cite: Solomita, G., Corrado, F., Balassone, G., Mondillo, N., Mormone, A., Strauss, H., and Piochi, M.: Hydrothermal alteration at the Tolfa volcanic district (Latium, Italy): texture, mineral and isotope chemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16850, https://doi.org/10.5194/egusphere-egu24-16850, 2024.

EGU24-17627 | ECS | Posters on site | GMPV8.2

Experimental and numerical thermos-kinetic modelling of hydrothermal alteration of volcanic rocks - Example of La Soufrière de Guadeloupe (Eastern Caribbean , France) 

François Décossin, Caroline Martel, Laurent Arbaret, Rémi Champallier, Philippe Penhoud, Mohamed Azaroual, Fabrice Muller, Jean-Christophe Komorowski, and Michael Heap

Volcano unrest associated to ascent of magmatic fluids (magma, brines, gases) at shallow depths in the presence of a very active hydrothermal system, can promote or enhance extensive hydrothermal rock alteration and form fragile discontinuities within the edifice. A process that can favour flank instability and culminate in partial flank collapse, engendering significant risks to the surrounding population. In the MYGALE ANR project, we focus on hydrothermal alteration timescales of andesitic rocks to better assess the hazard of volcano flank instability at La Soufrière de Guadeloupe (Eastern Caribbean, France). The conditions and kinetics of hydrothermal alteration reactions of the volcanic rocks of La Soufrière lava dome are determined by three approaches: mineralogical, experimental, and by modelling. Firstly, we characterized the natural alteration sequence of 20 samples from the lava dome and lava flows showing different degrees of alteration and porosity. SEM and XRD analyses of the samples show that the plagioclases are replaced by secondary minerals such as kaolinite, natroalunite, and amorphous silica. Secondly, we performed time-series fluid flow-through experiments, in which fluids are circulated through a pristine and porous andesite core (representative of the unaltered state of the present-day lava dome at La Soufrière). We varied temperature (200-250 °C), pressure (100-150 bar), duration (from days to months), and fluid composition (H2O-HCl mixtures). Rock permeability is measured in-situ and the mineralogical changes are characterized by post-experiment using various methods (SEM, EDS, EMPA, X-ray microtomography, and XRD). A sharp decrease in permeability of four orders of magnitude (from 10-14 to 10-18 m2) during the first 3-6 days was observed when using pure water as the percolating pore fluid. The cause of this large and fast decrease in permeability is currently being investigated. Experiments using H2O-HCl fluids are in progress attempting to reproduce the alteration sequence of the natural samples. Thirdly, we performed thermodynamic and kinetic numerical modelling using Perple_X, Phreeqc, and GEM-Selektor codes, in order to better constrain the conditions (especially the fluid phase composition) for hydrothermal alteration and to explore the alteration kinetics for timescales longer than those attained experimentally.

How to cite: Décossin, F., Martel, C., Arbaret, L., Champallier, R., Penhoud, P., Azaroual, M., Muller, F., Komorowski, J.-C., and Heap, M.: Experimental and numerical thermos-kinetic modelling of hydrothermal alteration of volcanic rocks - Example of La Soufrière de Guadeloupe (Eastern Caribbean , France), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17627, https://doi.org/10.5194/egusphere-egu24-17627, 2024.

EGU24-18301 | Orals | GMPV8.2

Characterization of the shallow hydrothermal system of Vulcano Island (Eolie islands, Italy)  through Electrical Resistivity Tomography (ERT) and Induces Polarization (IP) tomography. 

Antonio Troiano, Anna Mocerino, Claudio De Paola, Fabio Pagliara, Maria Giulia Di Giuseppe, Roberto Isaia, and Rosa Di Maio

The island of Vulcano is situated in the southern part of the Salina-Lipari-Vulcano ridge and, together with these two islands, constitutes the central sector of the Aeolian archipelago. It is a complex active volcanic system whose last eruption occurred between 1888 and 1890. Since then, intense fumarolic activity accompanied the various phases of unrest of the associated hydrothermal system, which made Vulcano the object of various geophysical, geochemical, and hydrogeological studies.

The aim of the study here presented was the investigation of the superficial hydrothermal system of Vulcano, specifically the northern sector of the island, where the ‘La Fossa’ caldera is located, which has been the main degassing area since the beginning of the last period of unrest. The survey has been conducted using geoelectrical methods because of the efficiency that these methods revealed in the previous studies on active volcanic systems, especially on Vulcano. The distribution of resistivity in the subsoil, indeed, is influenced by parameters such as temperature, permeability, porosity, presence of fluids and their salinity, which allow the reconstruction of the changes in the lithological and structural features with depth and the evaluation of the presence of discontinuity, such as faults, that have a fundamental role in the circulation of fluids.

During the survey, electric resistivity, chargeability, and self-potential data were jointly acquired along five profiles with lengths between 700 m and 2500 m and an investigation depth of approximately 200 m. The tomographies resulting from the data processing provide information on the evolution of the hydrothermal system, allowing us to identify the prominent resistivity anomalies and the pattern of hydrothermal fluid circulation. By integrating the results obtained with the ones emerging from previous studies conducted on the island, it is possible to implement a more exhaustive evaluation of the hydrothermal mechanism in the areas adjacent to the La Fossa caldera and how the flow is facilitated or hindered by the main fault system of Vulcano, that is necessary to analyze in order to previously verify the actualization of conditions favorable to the overpressure or decompression of the fluids, which could trigger an explosive eruptive event.

How to cite: Troiano, A., Mocerino, A., De Paola, C., Pagliara, F., Di Giuseppe, M. G., Isaia, R., and Di Maio, R.: Characterization of the shallow hydrothermal system of Vulcano Island (Eolie islands, Italy)  through Electrical Resistivity Tomography (ERT) and Induces Polarization (IP) tomography., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18301, https://doi.org/10.5194/egusphere-egu24-18301, 2024.

The island of Vulcano is one of the most exposed volcanic edifices of the Aeolian islands. Vulcano has been responsible for many eruptions, including at least three phreatic eruptions. The most recent eruption on the island occurred between 1888 and 1890 AD, and since then, Vulcano’s hydrothermal system has been the site of different volcanic unrest. In 2021, geochemical and geophysical parameters showed changes, suggesting a potential increase in magmatic fluid within the shallow geothermal system. GPS data revealed an expansion of the crater zone, consequently increasing the Vulcano alert level.

The main volcano-tectonic structures and geothermal fluid pathways have been resolved down to a depth of 2.5 km through a magnetotelluric (MT) survey conducted in 2022 (Di Giuseppe et al., 2023). A more detailed definition and mapping of the significant volcano-tectonic structures were subsequently acquired through a high-resolution Electrical Resistivity Tomography (ERT) and Induced Polarization (IP) investigation campaign conducted in 2023. These surveys provided original information regarding the main structure of the caldera and the related subsurface fluid circulation. The overall characterization of the link between the shallow geothermal system and the volcano activity furnished by the electromagnetic and electrical investigations represented the basis for developing thermo-fluid dynamic modeling of Vulcano island using the TOUGH2 numerical code. Adopting a conceptual model of the island mainly derived from the results of the MT and ERT investigations and considering literature and monitoring data collected immediately before and after the 2021 Vulcano unrest phase, a thermodynamic stationary state has been reconstructed, which likely represents a reliable description of the actual condition of the volcano. Subsequently, perturbation analysis of such a thermodynamical state has been performed to characterize the recent unrest phase involving Vulcano during the past two years and to reconstruct its primary mechanisms.

How to cite: De Paola, C., Di Giuseppe, M. G., Isaia, R., Pagliara, F., and Troiano, A.: Characterization of the 2021 unrest phase of Vulcano Island (Eolie islands, Italy) through numerical modelling: an integrated approach based on Electrical Resistivity Tomography and Magnetotelluric data., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18827, https://doi.org/10.5194/egusphere-egu24-18827, 2024.

Studies of deformation in volcanic settings are typically focused on active magmatic systems where inflation due to the injection of magma is an important indicator of potential eruptive activity. Phreatic eruptions are the result of the sudden flashing of trapped water to steam without the eruption of magma, and the resulting deformation is at a much smaller scale that is more difficult to detect. Rincon de la Vieja volcano is highly active system in northern Costa Rica that experiences frequent, predominantly phreatic and phreatomagmatic, eruptive activity. Multiple GNSS stations are set up and maintained by OVSICORI as part of their nationwide network including stations located 1 km south-west (summit station) and 5 km northwest (flank station) of the active vent. The summit station shows repeated movement towards the vent (northeast) 1-2 months prior to significant eruptions (infrasound magnitude > 4.5) on January 30th, 2020, April 15th, 2020, May 25th, 2020 and January 6th, 2022. Using a 30-day moving average, the north-south component appears to be the most reactive with repeated deformation of approximately 5 mm compared to ~2 mm for the east-west component. The vertical component does not show a similar signal prior to single events, however it does show significant uplift (up to 20 mm) during periods of high eruptive activity. This signal is most prominent in 2020 and 2022 when Rincon experienced hundreds of eruptive events per year resulting in a saw-tooth pattern of deformation. Similar signals are not visible on the flank station, potentially indicative of a shallow pressure source close to the vent itself and consistent with pressurization within the shallow hydrothermal system. To date, a phreatic eruption has not been successfully forecast owing to a lack of reliable precursory signals. Improved eruption forecasting likely requires a combination of measurements to document changes in gas flux, seismic signals, thermal signatures, and deformation.

How to cite: Mick, E., Muller, C., and Stix, J.: Ground Deformation Prior to Phreatic Eruptions at Rincón de la Vieja Volcano, Costa Rica Detected Using GNSS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11, https://doi.org/10.5194/egusphere-egu24-11, 2024.

EGU24-100 | ECS | Posters on site | GMPV8.6

 Deconstructing the role of hydrothermal alteration in 3D volcanic dome collapse in La Soufrière de Guadeloupe 

Kendra Ní Nualláin and Claire Harnett

Volcanic domes are inherently unstable structures as they grow incrementally, with varied extrusion rates, material properties, and directions of flow. These instabilities can bring about volcanic dome collapse, leading to turbulent and hot avalanches of material that can devastate communities surrounding a volcano, as well as affecting the volcano’s eruptive dynamics.

The objective of this research is to investigate the effect of hydrothermal alteration on dome stability, where hydrothermal alteration typically results in mechanical weakening of volcanic rock. To achieve this goal, it is important to understand the spatial distribution of alteration within a dome. The internal structure of the La Soufrière de Guadeloupe dome was mapped by Heap et al. (2021), whereby electrical conductivity surveys were carried out to obtain the rock porosity and therefore the density variation within the dome. The density contrasts were correlated with mechanical parameters (i.e., uniaxial compressive strength of volcanic rock) to obtain a 3D internal strength map of the volcano. We designed a novel methodology to input this geophysical data into a new 3D particle-based Discrete Element Method model. This involves creating a digital elevation model from satellite data and interpolating the geophysical data to assign strengths to each modelled particle.

We show here the results of alteration scenario testing. This involves varying the degree of alteration-induced weakening, the spatial extent, and the size of alteration zones. This allows us to make predictions on potential for collapse and direction of material flow, quantify collapse volumes, and explore small-scale to large-scale failures. In particular, we investigate the effect of ongoing alteration of the La Soufrière de Guadeloupe dome. Observations show pervasive hydrothermal alteration, particularly in an area in the south of the dome known as the “bulge”. This represents a potential detachment plane and thus is a focus for our collapse models.

Thus far, key findings from our investigations suggest that even near-surface alteration can cause deep-seated deformation. We also show varied weakening scenarios for a bulk rock strength of 10% and 50% of the original strength, with a focus on the southern flank of the dome. To date, no 3D dynamic models of stability exist and therefore these models are key to forecasting volcanic hazards as a result of hydrothermal alteration.

How to cite: Ní Nualláin, K. and Harnett, C.:  Deconstructing the role of hydrothermal alteration in 3D volcanic dome collapse in La Soufrière de Guadeloupe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-100, https://doi.org/10.5194/egusphere-egu24-100, 2024.

EGU24-543 | Posters virtual | GMPV8.6

Thermo-poro-elastic effects induced by fluid flow can explain the recent seismicity and deformation at Campi Flegrei (Italy) 

Massimo Nespoli, Anna Tramelli, Maria Elina Belardinelli, and Maurizio Bonafede

Thermo-Poro-Elastic (TPE) inclusions are suitable to model the mechanical effects induced by hot and pressurized hydrothermal fluids pervading a closed volume of rocks. In fact, modeling of TPE deformation sources finds application in both geothermal and vulcanological fields. Some recent works showed that a cylindrical TPE inclusion located at about 2 km of depth contributed to the large and rapid soil uplift observed during the ‘82-’84 unrest phase in the Campi Flegrei caldera. In the present work, we demonstrate that such a source of deformation can be responsible for a significant contribution even in the current unrest phase, that started in 2005 and it is still in progress. We show that the time-series of soil uplift observed in the last years can be reproduced by assuming the rising of hot and pressurized fluids, possibly exsolved by a deep magmatic source, within the same deformation source responsible of the ‘82-’84 unrest. The existence of such a TPE inclusion at Campi Flegrei was supported by previous tomographic studies and it is reinforced by the new analysis of the b-values. In fact, we found a sharp variation of the b-value in correspondence of the depth of the modelled TPE inclusion. The decrease of the b-values is consistent with the fact that within the TPE inclusion the induced shear stress is maximum and the occurrence of larger earthquakes is favored. The results support the existence and the importance of the mechanical effects of fluids flow, during the unrest phases of the Campi Flegrei caldera.

How to cite: Nespoli, M., Tramelli, A., Belardinelli, M. E., and Bonafede, M.: Thermo-poro-elastic effects induced by fluid flow can explain the recent seismicity and deformation at Campi Flegrei (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-543, https://doi.org/10.5194/egusphere-egu24-543, 2024.

The Late Devonian Mount Grace carbonatites outcrop as thin, laterally discontinuous strata-bound lenses within the deformed and metamorphosed Monashee cover sequence of the Canadian Cordillera. The identified lithofacies range from carbonatite tuffs to tuff breccias, in line with a pyroclastic origin resulting from phreatomagmatic eruptions forming in a field of maar volcanoes. Carbonatitic eruptions occurred in a transgressive shallow marine platform setting along the western margin of paleo-North America. The timing and distribution of the Mount Grace carbonatites correlate with regional Late-Devonian back-arc extension and other rift-related sedimentary exhalative deposits, alkalic volcanism, and carbonatite and alkalic intrusions. Whole-rock geochemistry of the Mount Grace carbonatites shows a strong positive Nb anomaly, moderate REE contents with high LREE/HREE, and strongly negative Zr-Hf anomalies that overlap with global rift-related carbonatite compositions. A positive correlation exists between REE content and LREE/HREE, and Nb/Ta and Zr/Hf in Mount Grace samples that indicate primary carbonate and pyrochlore crystallization, increasing in the more evolved compositions. The evolved compositions correspond with higher proportions of phoscorite (apatite, biotite, ferrorichterite, and pyrochlore). We invoke an ascent model for the Mount Grace carbonatites, similar to other carbonatite/phoscorite complexes where an ascending parental carbonate-phosphate/Fe oxide-rich melt undergoes liquid immiscibility of phoscorite-enriched carbonatitic magma, allowing the lower density residual phoscorite-poor carbonatite magma to ascend rapidly through the crust. Zircon Hf and apatite and pyrochlore Nd and Sr isotopes from the Mount Grace carbonatites have relatively depleted mantle signatures at 360 Ma, very close to Focal Zone (FOZO) and high mu (238U/204Pb; HIMU)-like mantle reservoir endmembers similar to global ocean island basalts and indicates a mantle source for these melts, potentially of great depths. Apatite and pyrochlore Nd and Sr isotopes from the Mount Grace carbonatites fall within the range of values for a depleted mantle reservoir presumably developed at ~3 Ga that sits beneath the Canadian Cordillera based on data from carbonatites emplaced from 2700 to 110 Ma in the Cordillera and Canadian Shield. Zircon Hf from Mount Grace carbonatites overlap with this depleted FOZO-HIMU mantle endmember and extend towards more enriched Hf values, reflecting their metasomatic origins. We infer that reactivated crustal-scale rifts allowed the emplacement of small-degree partial melts of an underlying, moderately depleted mantle source.

How to cite: Abdale, L., Groat, L., Russell, J. K., and Millonig, L.: The enigmatic Mount Grace extrusive carbonatites, southeastern Canadian Cordillera: volcanic architecture, mantle source, and tectonomagmatic framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1203, https://doi.org/10.5194/egusphere-egu24-1203, 2024.

EGU24-2645 | ECS | Orals | GMPV8.6

Fissure-type vents at 2021 Cumbre Vieja volcanic eruption  

David Sanz-Mangas, Inés Galindo, Raúl Pérez-López, Miguel Ángel Rodríguez-Pascua, María Ángeles Perucha, Carlos Camuñas, Julio López-Gutierrez, Juan Carlos García López-Davalillo, Carlos Lorenzo, Gonzalo Lozano, Juana Vegas, Rayco Marrero, Mario Hernández, José Francisco Mediato, and Nieves Sánchez

Multi-vent opening in monogenetic eruptions in the Canary Islands poses a threat considering the fast population increase over the last years. On the 19th of September of 2021 the last volcanic eruption of La Palma Island took place in the Cumbre Vieja volcanic ridge. The lava issued during the eruption affected more than 3000 buildings. The eruption was mainly concentrated along a main fissure that formed a cinder cone of approximately 200 m-high topped by several craters trending NW-SE. Although the geophysical data did not suggest the possibility of new vents opening far from the main fissure, more than 80 low effusion rate vents were opened following NW-SE, N-S and E-W directions. Effusive vents were opened as far as 3 km from the main fissure. Hawaiian style dominated in distal vents, and fast-flow pahoehoe lavas inundated new urban areas apparently out of danger to the south of the lava field. Previous historic eruptions show a similar pattern of several fissure-type vents extending over more than 4 km like Martín in 1642, El Charco in 1712 or San Juan in 1949.

In the 2021 eruption some possible precursors were observed previous to the distal vents opening such as CO2 diffuse gas anomalies, the opening of small fractures, local deformation, fumarolic activity and related small landslides before the feeder dike reached the surface. Since distal vents opening was unnoticed by the geophysical monitoring, we propose a detailed monitoring of diffuse gas emission and local fragile and ductile deformation in a radio of several kilometres from the main fissure. The previous knowledge of the detailed volcano-tectonic structure is also essential.

How to cite: Sanz-Mangas, D., Galindo, I., Pérez-López, R., Rodríguez-Pascua, M. Á., Perucha, M. Á., Camuñas, C., López-Gutierrez, J., García López-Davalillo, J. C., Lorenzo, C., Lozano, G., Vegas, J., Marrero, R., Hernández, M., Mediato, J. F., and Sánchez, N.: Fissure-type vents at 2021 Cumbre Vieja volcanic eruption , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2645, https://doi.org/10.5194/egusphere-egu24-2645, 2024.

Dikes represent magma filled fractures that may propagate from a magma chamber to the surface producing an eruption, or alternatively may stall at some depth resulting only in deformation and seismicity. A crucial parameter for the modeling of dike propagation is fracture toughness, which can be defined as the critical stress intensity factor that is necessary for a fracture to propagate. Despite the fact that fracture toughness is a well defined physical quantity adopted from material science, its meaning and possible variation in volcanic environments remains poorly understood. Dike volume can provide valuable information on the level of fracture toughness and on its balance with viscous flow that ultimately determines the dynamics of dike propagation. Recently it has been shown that intrusion volume can be derived from the cumulative seismic moment release of earthquakes that accompany dike propagation. Here it is shown that a similar methodology can be utilized in order to reconstruct the volume history of dikes using high-quality earthquake catalogs from 8 volcanoes (Augustine, Bardarbunga, Cumbre Vieja, Etna, Hierro, Kilauea, Okmok, Redoubt) spanning different volcanological and tectonic settings. The pre-eruption dike volume is compared to Monte Carlo simulations of critical volume performed for a range of fracture toughness and density difference using realistic values of elastic moduli and Poisson ratio. The volume history for each eruption is also utilized for estimating magma flux rate in the dike in order to infer whether fracture toughness or viscous flow dominates dike propagation. Results show that in all the volcanoes considered fracture toughness of 100 MPa m1/2 can explain pre-eruption volumes indepedently of volcano type and length scale of the dike. In 6 out of 8 eruptions studied dike propagation fluctuated between being dominated by fracture toughness and viscous flow, while only in two cases propagation was driven almost exclusively by viscous flow.

How to cite: Konstantinou, K.: When dikes go critical: Fracture toughness and propagation dynamics using earthquake catalogs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3311, https://doi.org/10.5194/egusphere-egu24-3311, 2024.

EGU24-3407 | Orals | GMPV8.6

Geophysical responses to an environmentally-boosted volcanic unrest 

Luca De Siena, Antonella Amoruso, Simona Petrosino, and Luca Crescentini

Campi Flegrei caldera, one of the most dangerous volcanoes in the world, is experiencing the strongest seismic and deformation unrest of the last 40 years. Geophysical, environmental, and geochemical responses during volcanic unrest at any volcano are difficult to couple: this is especially true at a caldera where deformation signals and earthquakes are attributed to magma and fluid/rock interactions at depths as well as tidal and meteoric forcing at the surface. Here, we applied Empirical Orthogonal Functions analysis, a technique developed within climatic and environmental Sciences, to GPS data. The technique allows the spatiotemporal separation of the dominant deep-sourced inflation from environmentally controlled signals associated with extension at Campi Flegrei caldera. This separation bridges the gap between deformation, seismic and geochemical responses, clarifying the processes that started the ongoing volcanic unrest. Persistent meteoric forcing during the 2017-18 hydrological year, located in the middle of a five-year drought, changed the decadal trend of seismic energy and secondary deformation components, pairing their spatial patterns. The result was a block in the carbon dioxide released in 2018 at Solfatara, the primary stress-release valve at the caldera. The subsequent overpressure weakened the fractured eastern caldera, opening pathways for hot materials produced by the dominant deep deformation source to reach the surface. Our results show how environmental forcing can favour volcanic unrest in pressurised calderas.

How to cite: De Siena, L., Amoruso, A., Petrosino, S., and Crescentini, L.: Geophysical responses to an environmentally-boosted volcanic unrest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3407, https://doi.org/10.5194/egusphere-egu24-3407, 2024.

EGU24-3516 | Orals | GMPV8.6 | Highlight

Patterns of deformation and connectivity at Western Galápagos Volcanoes 

Susanna Ebmeier, Eoin Reddin, Eleanora Rivalta, Marco Bagnardi, Scott Baker, Andrew Bell, Patrica Mothes, and Santiago Aguaiza

The Western Galápagos volcanoes of Alcedo, Cerro Azul, Darwin, Fernandina, Sierra Negra, and Wolf have exceptionally high rates of eruption and unrest.  Deformation rates measured using Interferometric Synthetic Aperture Radar are high magnitude during eruptions and episodes of magmatic intrusion, but also significant during inter-eruptive periods.  There are characteristic differences in deformation and unrest styles between the volcanoes that have persisted for at least three decades, indicative of the impact of topography, magmatic zone maturity and magmatic flux.   

Here, we focus on analysing the trends in displacements at these six volcanoes over the past three decades. These show correlations not only in long-term uplift and subsidence, but also in short term fluctuations in displacement rate.  Correlation is especially high during episodes of high melt flux into the shallow crust, indicating some degree of connectivity in the subsurface. We are able to rule out static stress changes, shallow hydraulic connections and radar processing artefacts, and suggest that the mechanism for connectivity lies in pore pressure diffusion at the base of the crust, as inferred at Hawai’i.

Volcanic deformation is generally interpreted in the context of shallow magmatic reservoirs treated as discrete independent systems.  However, in the Western Galápagos, and potentially many other places around the world, they are actually the most accessible expression of vertically extensive, heterogeneous magmatic systems.

How to cite: Ebmeier, S., Reddin, E., Rivalta, E., Bagnardi, M., Baker, S., Bell, A., Mothes, P., and Aguaiza, S.: Patterns of deformation and connectivity at Western Galápagos Volcanoes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3516, https://doi.org/10.5194/egusphere-egu24-3516, 2024.

EGU24-4510 | ECS | Orals | GMPV8.6

A New Dike Propagation Model Linking Seismicity and Rock Damage Mechanics 

Yan Zhan and Yiwen Huang

Dikes feed volcanic eruptions, causing devastating hazards and global impacts. Monitoring magma ascent through dike propagation can significantly enhance hazard assessment and mitigation. However, direct observation of dike propagation remains elusive. Among the available data, dike-induced earthquakes offer the best tracing of subsurface dike movement. These earthquakes may facilitate dike propagation by damaging the rock or slowing down the dike by releasing accumulated stresses. Yet, the relationship between these earthquakes and rock damage remains unclear. To clarify this relationship, we have developed a new dike propagation model that couples damage mechanics with porous flow to explore the local stress field's influence on fluid mobility within the dike. Our model's results show that the energy released during the rock-damaging process aligns with the seismicity induced by the dike. Furthermore, the model-calculated local stresses near the dike can explain the observed fault plane solutions associated with dike propagation. The new model also reveals the controls on magma ascent velocity, intrusion geometry, and surface deformation, with implications for other volcanic systems such as Bardarbunga, La Palma, and Piton de la Fournaise volcanoes.

How to cite: Zhan, Y. and Huang, Y.: A New Dike Propagation Model Linking Seismicity and Rock Damage Mechanics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4510, https://doi.org/10.5194/egusphere-egu24-4510, 2024.

EGU24-4731 | Posters on site | GMPV8.6

Is it really a Mogi or a mirage caused by the assumption of medium homogeneity? 

Antonella Amoruso and Luca Crescentini

Surface deformation in volcanic areas is often ascribed to inflation/deflation of pressurized cavities. Fast data inversion requires running many forward models based on the approximate computation of surface deformation due to selected expansive sources (sphere, spheroid, sill, and, more recently, scalene ellipsoid) embedded in a homogeneous elastic half-space. A simple very small spherical source (Mogi’s model; Mogi, 1958) often satisfy observations reasonably.

However, Earth is not homogeneous but characterized by vertical and horizontal heterogeneities; in many cases, vertical heterogeneities dominate and rigidity of the medium increases with depth. On the basis of these considerations, to highlight how the assumption of homogeneous elastic medium affects the inverted source parameters we (i) calculate the surface deformation due to point spheroids with vertical polar axis embedded in a layered half-space, and (ii) invert the computed surface deformations for the same source types (but with free geometry) embedded in a homogeneous half-space. In both forward and inverse modeling, the point source is schematized using an appropriate moment tensor (Davis, 1986); in forward modelling, we use Wang's Green functions (Wang et al., 2006) and, for comparison, also FEM. We consider two different examples of layering, which are approximately valid for Campi Flegrei (Amoruso et al., 2008) and Long Valley (velocity profiles from Biondi et al., 2023) respectively, and invert computed surface deformation (radial and vertical displacements) up to various distances from the source axis. We minimize both the mean square deviation (L2 norm) and the mean absolute deviation (L1 norm) of residuals.

The inversions show that:

1. as expected, the retrieved source appears shallower than the “real” source (i. e., focussing effect); the focussing effect depends on the source aspect ratio, generally increasing from prolate to oblate spheroids;

2. unless the “real” source is strongly vertically elongated (i. e. prolate), the retrieved source always appears very close to a spherical one (Mogi’s model); this effect depends on the source depth (less strong for shallow sources) and inversion norm (less strong for L1 norm).

Our results explain why a Mogi’s source so often satisfy deformation data, but also rise a big warning on the reliability of the inversions that provide it as a solution.

References

Amoruso, A., Crescentini, L., Berrino, G. (2008), Earth Planet. Sci. Lett., 272, 181-188.

Biondi, E. et al. (2023), Sci. Adv. 9, eadi9878.

Davis, P. M. (1986), J. Geophys. Res., 91, 7429-7438.

Mogi, K. (1958), Bull. Earthq. Res. Inst. 36, 99-134.

Wang, R., Lorenzo Martín, F., Roth, F. (2006), Comput. Geosci. 32, 527-541.

How to cite: Amoruso, A. and Crescentini, L.: Is it really a Mogi or a mirage caused by the assumption of medium homogeneity?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4731, https://doi.org/10.5194/egusphere-egu24-4731, 2024.

EGU24-5131 | Orals | GMPV8.6

Gas buffering of magma chamber contraction during persistent explosive activity at Mt. Etna volcano 

Daniele Carbone, Flavio Cannavò, Chiara Montagna, and Filippo Greco

Decrease of the local gravity field and ground deflation were observed at Mt. Etna through continuous measurements, during a 2-month period when more than 20 short-lasting explosive eruptions took place. Results from the joint inversion of the gravity and ground deformation data are cross-checked against the output of a numerical code providing independent geochemical insight on how the density of the magmatic liquid/gas mixture in the source reservoir varies as a function of the pressure. This cross-analysis provides a framework to explain why (i) the bulk volume reduction sensed by the ground deformation data is much lower than the volume of the erupted products and (ii) the observed gravity changes point to a strong mass decrease, that is incompatible with a pure mechanism of magma withdrawal. Contraction of the source reservoir was mostly buffered by pressure-driven exsolution and expansion of H2O and CO2, which compensated the withdrawal of magma and led to the inferred mass decrease.

How to cite: Carbone, D., Cannavò, F., Montagna, C., and Greco, F.: Gas buffering of magma chamber contraction during persistent explosive activity at Mt. Etna volcano, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5131, https://doi.org/10.5194/egusphere-egu24-5131, 2024.

Lava emplacement in a summit crater is often associated with unpredictable explosions and volcanic hazards, especially for volcanoes that are popular with tourists. The Lascar volcano, Chile, experienced a sudden eruption in December 2022, followed by the extrusion of lava. We acquired a series of Pleiades tri-stereo satellite images covering this new eruptive episode. Using a photogrammetric approach, we generated high resolution point clouds and orthomosaics from the satellite images. By directly comparing distances between point clouds, we are able to quantify morphological and structural details and changes. We find initial uplift of the crater floor due to lava extrusion and rockfall deposits, and evidence for subsidence and the formation of a funnel centered on the crater floor. To understand the mechanical factors controlling the uplift and subsidence of the crater floor, we designed a novel set of analogue experiments to simulate lava extrusion and subsidence inside a scaled 3D printed mould of the Lascar crater. We account for geometric and topographic effects by running these extrusion and subsidence models. Sand and sand-plaster mixtures extrude and subside from a vertical conduit at a constant rate, simultaneously recorded by a digital camera at 10-second intervals. We use particle image velocimetry (PIV) method to track and visualize displacements on the crater floor. The results show that extrusion and subsidence occurs along distinct shear faults, which are constrained by the diameter of the underlying conduit. The shear faults are represented as concentric fractures and are consistent with the ring features observed at Lascar. By comparing satellite observations with analogue models, we develop a conceptual model in which a lava extrusion is affected by withdrawal from the conduit, forming a funnel-shaped surface depression associated with inward-dipping radial erosion gullies. Thus, our observations and analogue models also help to define the position and dimensions of the volcanic conduit, which is essential for understanding future episodes of the ups and downs of the Lascar crater floor.

How to cite: Ai, L., Walter, T., and Aguilera, F.: The ups and downs of the Lascar crater floor, and the resulting fracture pattern analyzed by satellite stereo photogrammetry and 3D printed mould analog experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6041, https://doi.org/10.5194/egusphere-egu24-6041, 2024.

EGU24-6693 | Orals | GMPV8.6 | Highlight

Real-time forecasts of unrest at Campi Flegrei, Southern Italy, 2013-2023. 

Christopher Kilburn, Eric Newland, Nicola Alessandro Pino, Stefano Carlino, and Stefania Danesi

Large volcanic calderas can take decades or more to return to activity after centuries in repose. Their reawakening frequently triggers several, intermittent episodes of unrest before magma finally erupts. The non-eruptive episodes can divide scientific opinion about the cause of unrest and its outcome. The Campi Flegrei caldera is a remarkable example. Fifteen kilometres across, it is Europe’s largest active caldera and supports a population of more than 360,000 people to the west of Naples in southern Italy. It has been episodically restless since 1950, for the first time in four centuries. Uplifts in 1950-52, 1969-72, 1982-84 and since 2004 have created a caldera-wide bulge that, close to its centre, has raised the coastal town of Pozzuoli by more than 4 m, while tens of thousands of small earthquakes have shaken the volcano to depths of 4 km.

The behaviour is consistent with repeated rupture of the crust. The most recent rupture developed between 2013 and 2023. The rate of local volcano-seismic earthquakes evolved from an exponential increase, through a constant rate to a hyperbolic increase with time. This is the classic pre-rupture sequence for elastic-brittle rock being extended under an approximately constant rate of supplied stress.

We used changes in the sequence to forecast the approach to rupture in real-time. Observations followed the forecast trend through the first nine months of 2023, by which time the increase in seismicity was expected to continue until early 2024. Instead, the rupture sequence culminated in October 2023, since when the rates of seismicity have decayed. The end of rupturing was brought forward by an increase in the number of larger magnitude earthquakes, which accelerated rates of stress loss compared with previous months. Uplift had also slowed by December 2024.  Each rupture sequence increases the amount of damage in the crust. Other factors being equal, therefore, if any new magma can reach the shallow crust in the near future, it is likely to meet a lower resistance to eruption than has been the case since unrest began in 1950.

How to cite: Kilburn, C., Newland, E., Pino, N. A., Carlino, S., and Danesi, S.: Real-time forecasts of unrest at Campi Flegrei, Southern Italy, 2013-2023., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6693, https://doi.org/10.5194/egusphere-egu24-6693, 2024.

EGU24-7847 | Orals | GMPV8.6

Evolution of the plumbing system at Campi Flegrei caldera (Italy) during the 2007-2023 unrest 

Elisa Trasatti, Ana Astort, Marco Polcari, Luca Caricchi, and Mauro A. Di Vito

Campi Flegrei Caldera (Italy) is affected by a still ongoing unrest characterized by increasing seismicity rates, gas emissions and ground deformations. Multi-technique geodetic data (satellite, inland and seafloor GNSS measurements) are collected to understand the evolution of the unrest from its beginning in 2007 to the end of 2023, to get insights on the plumbing system. The data show increasing rates of deformation in the last 16 years, focusing in the caldera center. 3D finite element models are employed in a Bayesian inversion framework, including the elastic heterogeneous structure of the underlying medium based on the newest seismic tomography of the area. The analysis divides the whole period into seven distinct time intervals, based on the changes in ground displacement time series. The modeling approach implements a double-source plumbing system: a shallower source with its depth and geometry determined by the inversion framework, and a second deeper tabular source at 8 km depth, consistent with the petrological and geochemical evidence of melt and massive degassing from the deeper portion of the magmatic system. The results reveal that the shallower source beneath Pozzuoli exhibits a gradual decrease in depth, from 5.9 km during 2007-2010 to 3.9 km during 2015-2023. The shallower seismicity, above 3 km depth, is influenced by the long-term straining of the local crust due to the continuous inflation of the shallower source. Concurrently, the deeper tabular source at 8 km depth experiences a limited but constant deflation over time. The depicted plumbing system evidences a sequential growth of horizontal opening and volumetric expansion of the shallower source, likely fed by the deeper source for 16 years at least, for a total volume variation of about 60 million cubic meters. To determine whether the shallower source is fed by fluids and/or magma, we performed calculations of volatiles and/or magma transfer from 8 km upwards, considering different settings. The most plausible scenario accounts for magma ascent associated with degassing and outgassing. Indeed, the volumetric variation calculated from geodetic data for the shallower source reflects the injection of an equivalent volume of magma and a deep source that is continuously refilled by a flux of magma comparable to the ascending one.

How to cite: Trasatti, E., Astort, A., Polcari, M., Caricchi, L., and Di Vito, M. A.: Evolution of the plumbing system at Campi Flegrei caldera (Italy) during the 2007-2023 unrest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7847, https://doi.org/10.5194/egusphere-egu24-7847, 2024.

EGU24-8016 | ECS | Orals | GMPV8.6

Seismicity near Mayotte explained by interacting magma bodies: Insights from numerical modeling 

Clement de Sagazan, Lise Retailleau, Muriel Gerbault, Aline Peltier, Nathalie Feuillet, Fabrice J. Fontaine, and Wayne C. Crawford

Mayotte island experienced a large volcanic eruption 50 km offshore in 2018-2021, creating the submarine volcano “Fani Maoré”. The eruption was accompanied by intense seismicity at mantle depths (20-45 km), divided into a “proximal” and a “distal” cluster centered 10 and 30 km east from the island, respectively. Previous studies suggest that two separate magma reservoirs may lie at the top and bottom of the proximal cluster. Here, we assess whether two reservoirs are a mechanically viable explanation for the proximal cluster’s truncated conical shape.

We developed finite-element models of pressurized magma reservoirs in a 2D axisymmetric domain, modeling the reservoirs as compliant elastic ellipsoids embedded in an elastoplastic host rock. We find that, at these depths, extremely low friction is required to generate failure at realistically low reservoir pressures. This implies in turn that mechanical weakening must occur at these depths. The weakening could be induced by fractures or pore fluid overpressure in the volcanic system. We find that two superimposed reservoirs can generate a plastic domain between them, if they are spatially close enough. Several reservoir geometries (from spherical to sill-like) are plausible.

A conical fracture domain is more likely to appear for reservoirs with opposite pressure loads (i.e. one inflating, one deflating). Given the geometrical match with the proximal seismicity cluster at Mayotte, we suggest that the shallower (Moho-depth) reservoir is inflating, creating a potential hazard for Mayotte island. 

How to cite: de Sagazan, C., Retailleau, L., Gerbault, M., Peltier, A., Feuillet, N., Fontaine, F. J., and Crawford, W. C.: Seismicity near Mayotte explained by interacting magma bodies: Insights from numerical modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8016, https://doi.org/10.5194/egusphere-egu24-8016, 2024.

EGU24-8240 | ECS | Orals | GMPV8.6

Analysis of dike-induced stresses and deformation: new insights from Mt. Etna and SW Iceland 

Noemi Corti, Alessandro Tibaldi, and Fabio Luca Bonali

During eruptions, magma arrives at the surface through vertical dikes. However, dikes often arrest in the crust, not feeding an eruption. Moreover, their emplacement causes a concentration of tensile and shear stresses in the host rock, that can lead to fracturing and/or faulting at the topographic surface. The relation between magma intrusion and dike-induced surface deformation has been analysed in the last decades through analytical, analogue and numerical models, but mostly considering an elastic and homogeneous half-space. Realistic data should therefore be considered to overcome this limitation.

For this reason, in this work, field structural data are used as inputs for numerical modelling. Three case studies, all affected by shallow dike emplacement, are considered: the 1928 and 1971 eruptive fissures on Mt. Etna (Italy), and the Younger Stampar eruptive fissure in SW Iceland. On Mt. Etna, dike-induced brittle deformation is visible at the surface, in plan view for both cases, and in section view for the 1971 case study. In Iceland, two dikes (one feeder and one arrested) are exposed along a cliff; the tip of the arrested dike is only 5 m below the surface, but no brittle deformation is observed. These case studies allow us to investigate the parameters that i) favour/inhibit dike-induced brittle deformation at the surface, ii) affect the geometry of dike-induced graben faults, and iii) promote dike arrest at shallow depths.

We collected structural data integrating classical fieldwork and remote sensing analyses, using high-resolution 2D and 3D models, reconstructed through Structure from Motion photogrammetry from drone images and historical aerial photos. We used all these structural data as inputs for 2D Finite Element Method numerical models, using the software COMSOL Multiphysics. In the models, sensitivity analyses were run to analyse the parameters that affect dike propagation and the induced surface deformation.

This work underlines the role of layering on the formation of stress barriers and on the distribution of dike-induced stresses, that concentrate in stiffer materials and are suppressed in softer layers. Furthermore, it confirms the effects of dike overpressure and inclination on its propagation and on dike-induced stresses. Topography also affects the dike propagation path and the geometry of dike-induced graben faults. Finally, the role of lateral compression induced by nearby previous intrusions is investigated, showing how this can promote dike arrest and the lack of brittle deformation.

How to cite: Corti, N., Tibaldi, A., and Bonali, F. L.: Analysis of dike-induced stresses and deformation: new insights from Mt. Etna and SW Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8240, https://doi.org/10.5194/egusphere-egu24-8240, 2024.

EGU24-8401 | Orals | GMPV8.6

Linking the gap between seismic and geodetic observations during the 2020-2022 lava fountains at Etna volcano 

Gilda Currenti, Luigi Carleo, and Alessandro Bonaccorso

Lava fountains at Etna volcano are spectacular explosive eruptions consisting of powerful jets of gas and solid particles that cause a huge impact both to air traffic and urban areas due to ash dispersal and fall-out.

The evolution of a lava fountain at Etna is usually a gradual process that progresses from a weak strombolian activity, passes to a typical lava jet and ends with the formation of a sustained eruptive column. Typically, lava fountain events last from tens of minutes to few hours. The interaction of the magma with the surrounding rock during such eruptive episodes induces tremor (0.5 - 5 Hz) and ultra-small deformation (10-9 to 10-7) of the superficial crust and generates geophysical signals at a wide ranges of amplitudes and time scales. Seismometers can capture only the higher frequency content of such signals by measuring volcanic tremor. Due to the small amount of related deformation, the traditional geodetic methods, such as GPS and InSAR, are not able to reveal significant variations because of the low precision (GPS resolution > 1 cm) or very low sampling frequency (InSAR temporal resolution limited by satellite passages). This limit is overcome by using Sacks-Evertson strainmeter that measures the volumetric deformation of the surrounding rock with the highest achievable resolution (10-10 to 10-11) and in a very wide frequency range (10-7 to > 20 Hz). Thanks to its characteristics, the strainmeter is perfectly suitable to explore the full spectrum and the very small amplitudes of the strain signal exerted by the lava fountain episodes at Etna, covering the frequency gap between the seismic and the common geodetic techniques.

In this work, we analyzed the co-eruptive strain changes recorded by the borehole strainmeter network concurrently with more than 60 lava fountain events that occurred at Etna volcano between 2020-2022. We investigated all the lava fountain events, highlighting the main characteristics of the eruptive phases and their transition that characterize such eruptions, both in the high and in the low frequency band. These characteristics furnish fundamental constraints to improve the characterization of eruptive processes that lead to lava fountain events.

How to cite: Currenti, G., Carleo, L., and Bonaccorso, A.: Linking the gap between seismic and geodetic observations during the 2020-2022 lava fountains at Etna volcano, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8401, https://doi.org/10.5194/egusphere-egu24-8401, 2024.

EGU24-9979 | ECS | Orals | GMPV8.6

Understanding the long-term 4D Dynamics of the Seismic Velocity at Mount St Helens, WA, USA 

Peter Makus, Marine Denolle, Christoph Sens-Schönfelder, Manuela Köpfli, and Frederik Tilmann

Mt. St. Helens is an explosively erupting volcano located in close vicinity to major metropolitan centres on the US West Coast. In recent history, Mt. St. Helens (MSH) erupted twice, in 2004 and 1980, causing more than 50 fatalities and over one billion USD of damage. Here, we present a seismic velocity change time series (dv/v) of an unprecedented length covering the years 1998-2023 recovered from seismic ambient noise. We discuss challenges arising from the very heterogeneous nature of the dataset recorded on a variety of seismic stations and discuss methods to address them. To reconcile measurements from different periods, we rely on an approach that simultaneously normalises our measurements and allows us to locate our dv/v estimates in space. Finally, we compare our obtained results to a multitude of auxiliary measurements, including GPS, earthquake, and meteorological data.  By employing models that link dv/v to these mechanisms, we attempt to unravel the contribution of each mechanism to our velocity change estimate. At volcanoes like MSH, our ultimate goal is to reliably isolate the volcanic contribution to dv/v, thereby aiding the identification of potential volcanic precursors.

How to cite: Makus, P., Denolle, M., Sens-Schönfelder, C., Köpfli, M., and Tilmann, F.: Understanding the long-term 4D Dynamics of the Seismic Velocity at Mount St Helens, WA, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9979, https://doi.org/10.5194/egusphere-egu24-9979, 2024.

The lateral magma propagation is a common feature of rift zones, with vertical dykes flowing parallel to the rift direction and opening against the minimum compressive stress. Depending on the competition between vertical and lateral magma migration, these dykes may either feed an eruption or not. In this context, the topography which includes the edifice load acts against the rise of the magma and favor lateral migration radially away from the edifice central area, thus feeding peripheral vents. Here, we use the case of Nyiragongo volcano, a volcanic edifice located in the western branch of the East African Rift and culminating at 3,470 meter above sea level to study such combined effect of rifting-induced extension and topographic loading on both the orientation of vertical dykes and on the balance between lateral versus vertical magma propagation within the propagation plane. Using analytical and numerical models taking into account the effect of topography and the local West-East extension stress field, we show that the path of a dike coming from the volcanic edifice is first influenced by the load of the volcano, leading to a radial propagation while beyond 5 km, the extensional stress field dominates leading to a North-South propagation towards Lake Kivu. These results are consistent with the path of the magma deduced from geophysical observations for the last two eruptive events of the Nyiragongo volcano (2002 and 2021). Furthermore, the downward slope toward Lake Kivu and, to a lesser extent, the slight increase in southward rift extension both favour lateral magma propagation, but reduced magma buoyancy at shallow depths is required to explain the lateral propagation over more than 20 km, where the magma remains trapped beneath the lake.

How to cite: Pinel, V. and Mériaux, C.: Interplay between rifting-induced extension and surface loading effects illustrated by lateral magma propagation at Nyiragongo volcano, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10472, https://doi.org/10.5194/egusphere-egu24-10472, 2024.

EGU24-10865 | Orals | GMPV8.6

Linking long-term magma evolution and short-term volcano deformation  

Gregor Weber, Juliet Biggs, and Catherine Annen

Volcanoes often change shape over timescales of months to decades, and such signals are likely influenced by the long-term physical evolution of magmatic systems over hundreds of thousands to millions of years. The link between these different timescales is often overlooked. In this presentation, I will show how volcanic surface deformation in response to a sudden overpressure at depth evolves over the long-term history of magmatic systems. To do this, I integrate thermal models of large-scale magma system evolution with thermo-mechanical simulations of surface deformation. We examined how changes in magma flux, magmatism duration over hundreds of thousands of years, and the depth of an overpressure source impact post-injection viscoelastic surface movement over a 10-year period. Our findings show that the duration of the long-term magmatic activity and magma supply rate significantly affect surface deformation over timescales of years. The results show that due to thermal heterogeneity in the crust, asymmetrical patterns of surface deformation can emerge in time due to viscoelastic processes, potentially similar to temporal patterns of magma movement. When uplift originates from deep sources (around 10 or 15 km below the surface), deformation follows a consistent uplift trend, dissipating within a few years with little dependence on past magma flux or system lifespan. Conversely, shallow sources (around 5 km below) display a strong dependence on long-term magma supply rate and system lifespan, resulting in distinct patterns of post-intrusive subsidence and subsequent uplift for colder magma systems, or exclusive uplift for hotter and longer-lived systems. These findings align exceptionally well with the deformation behaviour and geophysical tomography at Tullu Moye and Aluto volcanoes in the East Africa Rift. In conclusion, understanding how long-term magmatic processes interact with short-term volcano deformation is crucial for interpreting signals of volcanic unrest.

How to cite: Weber, G., Biggs, J., and Annen, C.: Linking long-term magma evolution and short-term volcano deformation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10865, https://doi.org/10.5194/egusphere-egu24-10865, 2024.

EGU24-10901 | Posters on site | GMPV8.6

The dynamics of the Pernicana Fault System (Mt. Etna, Sicily) investigated by 4 decades of multiparametric ground deformation data: inferences on the interaction between flank and magma dynamics 

Alessandro Bonforte, Stefano Branca, Cubellis Elena, Salvatore Gambino, Francesco Guglielmino, Francesco Obrizzo, Laura Privitera, Giuseppe Puglisi, and Umberto Tammaro

Mt. Etna volcano is located along the eastern coast of Sicily. In this region, the general N-S compressive regime related to the Africa – Eurasia collision interacts with the WNW-ESE extensional regime associated to the Malta Escarpment dynamics, observable along the eastern coast of Sicily.

A general eastward motion of the eastern flank of the volcano has been measured with always increasing detail and its relationship with the eruptive and magmatic activity is being investigated. The complex interaction between regional stress, gravity forces and dike-induced rifting of Mount Etna, seems to have a role in the eastward movement of the Mt. Etna eastern flank. In this context the Pernicana Fault system identifies the northern boundary of the mobile sector.

It is formed by discrete segments, arranged in a right stepping en-échelon configuration, of a left-lateral shear zone that dissects the north-eastern flank of Etna. Its kinematics is related to shallow seismic crises (M ≈ 4.0) occurring along the western segment, with dip-slip displacement and left-lateral components. The eastern segment, ESE trending, shows only aseismic creep with purely left-lateral displacement.

The dynamics of the fault has been analyzed by a multi-disciplinary approach: levelling, tiltmeters, InSAR and GNSS.

The fault system shows clear traces on SAR interferograms and time series. InSAR data allows tracking the path of the Pernicana fault from the NE rift to the coastline; the eastwards motion abruptly disappears north of the fault, producing a left-lateral transcurrent kinematics at a rate of about 30 mm/y. Episodic accelerations are visible on GNSS and InSAR data from different sensors, related to seismic crises and eruptive activity. The dense GNSS network is measured periodically and has more than seventy benchmarks. The time series of this network began in 1988 and from then on its configuration has been continuously improved. Two GNSS networks lie across the eastern segment of the Pernicana fault. The first one, located in the “Rocca Campana” area, was installed in April 1997; the second one, located a few kilometers westward, in the “Rocca Pignatello” area, was measured for the first time in July 2002 upgrading an EDM network. The aim of these networks is to detail the structural framework and displacements along the aseismic sector of the Pernicana fault. Finally, the levelling route on Mt Etna, installed in 1980, is 150 km long and consists of 200 benchmarks. Part of the levelling route crosses the Pernicana fault, at an altitude of 1500 and 700 m asl. Measures on this network started on eighties and provide a high detail on the vertical kinematics allowing strong constraints in modelling the sources of slip episodes.

Integration of this wide spectrum of geodetic data allows strongly constrained ground deformation pattern to be defined and modeled. Furthermore, the very long time series available for the different datasets on the Pernicana fault, allows its behavior to be investigated in time and its role and relationships in the framework of flank instability and eruptive activity to better understood.

How to cite: Bonforte, A., Branca, S., Elena, C., Gambino, S., Guglielmino, F., Obrizzo, F., Privitera, L., Puglisi, G., and Tammaro, U.: The dynamics of the Pernicana Fault System (Mt. Etna, Sicily) investigated by 4 decades of multiparametric ground deformation data: inferences on the interaction between flank and magma dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10901, https://doi.org/10.5194/egusphere-egu24-10901, 2024.

EGU24-11005 | ECS | Orals | GMPV8.6

Numerical modelling of earthquake induced stress changes and dike migration preceding the 2018 eruption of Sierra Negra Volcano, Galápagos 

Lilian Lucas, Peter C. La Femina, Patricia M. Gregg, Matthew S. Head, Machel Higgins, and Andrew F. Bell

Studying the interactions between magmatic and volcano-tectonic processes is critical to understanding the behavior of volcanic systems and the triggering of eruptions. Sierra Negra Volcano, Galápagos is one of the largest basaltic calderas on Earth, and its latest eruption in 2018 marked the first time an eruption in the Galápagos was recorded by both GNSS and seismic networks. These unprecedented data sets provide a unique opportunity to investigate the dynamics of eruption triggering and test hypotheses for dike initiation and migration. Observational and modeling studies of Sierra Negra’s previous eruption in 2005 hypothesize that tensile opening induced by a Mw5.3 earthquake on the southern intra-caldera trapdoor fault system resulted in magmatic dike initiation and eruption along the northern rim of the caldera (Gregg et al., GRL, 2018). In the ~13 years following the 2005 eruption, the caldera of Sierra Negra uplifted ~6.5 m (Bell et al., Nat. Comm., 2021). Sierra Negra’s inflation coincided with an increase in Mw > 4 earthquakes located along the intra-caldera fault system from late 2017 to June 2018 and a Mw5.4 earthquake occurred ~9 hours prior to the first eruptive fissure opening on 26 June 2018 (Bell et al., JGR, 2021). The similarities between the 2005 and 2018 pre-eruption sequences provide important clues about the dynamics of eruption triggering at Sierra Negra. In this study, we build upon previous numerical analyses of the 2005 and 2018 eruption (Gregg et al., GRL, 2018; Gregg et al., Sci. Adv., 2020; Bell et al., Nat. Comm., 2021) to model stress changes associated with the 2018 pre-eruptive Mw5.4 earthquake and begin to investigate dike initiation and magma migration leading to the first fissure opening. Specifically, thermomechanical finite element models are implemented in COMSOL Multiphysics to test the hypothesis that the Mw5.4 thrust fault earthquake promoted tensile failure and dike rupture in the northern region of the magma system. Future numerical models will test the hypothesis that the resulting stress field of the Mw5.4 earthquake controlled the pathway of dike migration. Previous numerical deformation models which exclude fault rupture (e.g., Gregg et al., Sci. Adv., 2018) do not result in system failure leading to eruption (i.e., tensile failure in the model space between the magma chamber and surface). Our new numerical model includes a segment of the intra-caldera Trapdoor Fault, and we solve for fault rupture parameters of the 26 June 2018 Mw5.4 earthquake, such as fault geometry and slip, and calculate the resulting stress and strain. The best-fit earthquake parameters are estimated by comparing the observed (cGPS-derived) and modeled co-seismic deformation. The stress field induced by both magma system inflation and fault rupture is evaluated to investigate failure of the volcanic edifice and optimal dike propagation pathways. Preliminary results demonstrate the importance of including fault displacements in model calculations of Sierra Negra’s stress evolution. In future numerical models, we aim to model and constrain magmatic intrusion geometries using pre- and syn-eruptive cGPS data to better understand the impact of static stress transfer in eruption triggering.

How to cite: Lucas, L., La Femina, P. C., Gregg, P. M., Head, M. S., Higgins, M., and Bell, A. F.: Numerical modelling of earthquake induced stress changes and dike migration preceding the 2018 eruption of Sierra Negra Volcano, Galápagos, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11005, https://doi.org/10.5194/egusphere-egu24-11005, 2024.

EGU24-11227 | Orals | GMPV8.6

From subsidence to uplift at Campi Flegrei, with an eye to Vesuvio 

Luca Crescentini, Antonella Amoruso, and Adriano Gualandi

Geodetic data measure deformation of various origins (e.g., tectonic, volcanic, hydrological, human-induced). To attempt separating the different signals underlying the observations, data can be analysed as in a blind source separation (BSS) problem. A common technique to tackle BSS problems is the Independent Component Analysis (ICA), which decomposes the dataset into a set of independent components (ICs) under the assumption of a linear mix of the non-moving sources.

We use a variant of ICA (vbICA, variational Bayesian ICA; Choudrey and Roberts, 2003) to analyze ground displacement time series from ERS-ENVISAT SAR images in a large area including Campi Flegrei and Vesuvio volcanoes (Italy) between 1993 – 2010. The time series, which have gaps, were obtained through the SBAS technique and provided to us by IREA-CNR.

Our analyses evidence two significant ICs. Their spatial and temporal features indicate that one of the ICs (IC1 in what follows) is related to Campi Flegrei only and describes the subsidence occurred before 2000, the mini-uplifts started in 2000 and 2005, and a post-2005 uplift. The other significant IC (IC2 in what follows) is related to the subsidence occurred at Vesuvio after 2001 (Amoruso & Crescentini, 2023) and an additional (with respect to IC1) post-2001 Campi Flegrei dynamics.

The IC1 spatial pattern confirms the results in Amoruso et al. (2014): it is satisfied by the joint effects of two pressurized sources embedded in an elastic layered half-space, i. e. a sill at a depth of about 3.5 km and a small spheroid at a depth of about 2 km; the two sources satisfy large-scale and local (Solfatara fumarolic field) deformation, respectively.

The IC2 spatial pattern is consistent with Amoruso & Crescentini (2023) as regards Vesuvio. As for the Campi Flegrei area, it is quite complex and difficult to ascribe to a single source, even as general as a moment tensor. If the whole IC2 spatial pattern is inverted for small (with respect to depth) pressurized spheroids (point sources), two deep sources (depths larger than about 8 km) acting in the Campi Flegrei area are needed in addition to the deflating source beneath Vesuvio. The three sources appear inactive before 2000; afterwards the two deep sources beneath Campi Flegrei show opposite behaviour.

We show that the scenario outlined by our results is consistent with geophysical (e.g., gravity) and petrological data. It is also consistent with subsequent pressurization of a sill-like source at about 8 km depth, inflating at least since 2015 (Amoruso & Crescentini, 2022).

References

Amoruso et al. (2014), J. Geophys. Res: SE, 119, 858–879.

Amoruso, A., and Crescentini, L. (2022). Remote Sens., 14, 5698.

Amoruso, A., and Crescentini, L. (2023). Remote Sens., 15, 3038.

Choudrey, R., and Roberts, S. (2003). Neural Computation, 15(1), 213-252. 

How to cite: Crescentini, L., Amoruso, A., and Gualandi, A.: From subsidence to uplift at Campi Flegrei, with an eye to Vesuvio, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11227, https://doi.org/10.5194/egusphere-egu24-11227, 2024.

Space for magma intrusion in the subsurface is often created by uplifting and bending of overlying rock, producing a forced fold. This intrusion-induced forced folding can deform the free surface, driving ground movement at active volcanoes. Monitoring such ground movement using satellite- and ground-based instrumentation plays a key role in volcanic eruption forecasting. Specifically, modelling ground movement allows us to assess eruption threats, by estimating intrusion properties (e.g., geometry, depth, volume, and pressure), and understand of volcanic system evolution and behaviour. Yet building accurate ground movement models to reliably estimate intrusion properties requires knowledge of a volcano’s subsurface composition and structure; information which is often limited or unavailable. Many ground movement models therefore tend to use analytical or numerical approaches that embed simple intrusion geometries within a homogeneous, isotropic, and linearly elastic medium (i.e., a material of uniform composition and structure). To assess the reliability and validity of such ground movement models, it would thus be beneficial to identify scenarios where known and modelled intrusion properties can be confidently compared.

Seismic reflection data image Earths subsurface in 3D at metre- to decametre-scale resolutions and can thus capture the detailed geometry of ancient intrusions and overlying forced folds. Where such intrusion-fold pairs have been seismically imaged, these data show: (1) intrusion geometries are typically complex; (2) host stratigraphic sequences comprise multiple lithologies; and (3) forced fold amplitudes are often less than intrusion thicknesses, implying space for magma was generated by both uplift and internal fold deformation (e.g., compaction). Importantly, seismic reflection data uniquely allow us to measure and model syn-emplacement ground movement driven by forced folding, whilst independently determining the geometry, size, and depth of underlying intrusions. Here, we examine an Early Cretaceous laccolith and forced fold pair imaged in 3D seismic reflection data from the Exmouth Plateau, offshore NW Australia. We consider how post-emplacement, burial-related compaction has reduced the fold amplitude by using local borehole data, which describe the lithology and seismic velocity of the folded strata, to decompact the succession and recover estimates of the original fold geometry. From these estimates of the original fold geometry, we calculate possible vertical and horizontal displacement components of deformation; this displacement data can be considered akin to that acquired during monitoring of ground movement at active volcanoes. By applying standard analytical methods to estimate intrusion properties from this pseudo-ground movement data, we compare model outputs to the true location, geometry, and size of the seismically imaged intrusion.

How to cite: Magee, C. and Ebmeier, S.: Magma Accommodation and Ground Movement Analysis: testing the reliability of analytical volcano deformation models , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11296, https://doi.org/10.5194/egusphere-egu24-11296, 2024.

EGU24-11682 | ECS | Posters on site | GMPV8.6

Etna's paroxysmal activity in 2021: A deflation episode revealed by joint DInSAR and GNSS ground deformation analysis 

Alejandra Vásquez Castillo, Francesco Guglielmino, Flavio Cannavò, Alessandro Bonforte, and Giuseppe Puglisi

In the final months of 2020, the summit craters of Mount Etna displayed intense Strombolian-type activity as well as an increase in seismicity. In December 2020, a period of paroxysms with powerful, brief bursts of lava fountaining began, which intensified in February 2021 and lasted until April.

We used both ascending and descending Sentinel-1 SAR images along with daily GNSS solutions at 21 stations to evaluate the surface deformation at Mount Etna in order to understand the dynamics of the shallow plumbing system, which is probably related with the feeding of the observed paroxysmal activity. According to the InSAR and GNSS time series, the volcano edifice entered a period of intense and continuous deflation for almost three months, matching the prolonged paroxysmal activity characterized by the occurrence of 17 lava fountain episodes. To integrate the two data sets, we have applied the 3D SISTEM algorithm, which allows to estimate 3D ground displacements by combining GNSS measurements of deformation and differential Interferometric Synthetic Aperture Radar (DInSAR) maps of surface displacement. We have used analytical models to constrain the sources of the paroxysmal activity and to evaluate the deflating source parameters by inverting the displacement obtained with the 3D SISTEM algorithm. Preliminary results reveal a centripetal deformation pattern that might be linked to a shallow source below the summit craters area. However, a detailed analysis of the deformation pattern indicates the presence of contributions that are not related to the magmatic source, but are probably attributable to tectonic or geomorphologic processes.

The aim of this work is therefore twofold. First, to infer the shape and dynamics of the magmatic feeding system of Mount Etna and its magma discharging regime. Second, given the complexity of the deformation signals at Mount Etna, to analyze how to deal with their different contributions including volcanic‐, tectonic-, geomorphological processes, and atmospheric noise.

How to cite: Vásquez Castillo, A., Guglielmino, F., Cannavò, F., Bonforte, A., and Puglisi, G.: Etna's paroxysmal activity in 2021: A deflation episode revealed by joint DInSAR and GNSS ground deformation analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11682, https://doi.org/10.5194/egusphere-egu24-11682, 2024.

EGU24-11747 | Posters on site | GMPV8.6

Relating magma dynamics and ground deformation patterns at Mount Etna 

Owen McCluskey, Paolo Papale, Chiara Montagna, and Deepak Garg

We adopt a forward model approach to ground deformation through the use of GALES (GAlerkin LEast Squares) to simulate the mixing of magmas of variable compositions and temperatures, coupled with the elastodynamic response of the surrounding medium. GALES is a finite element parallel C++ code which solves for both the fluid and elasto-dynamic equations. Firstly, the mass, momentum and energy conservation equations are solved through GALES to simulate magma transfers across reservoirs connected through dykes. This allows the computation of the space-time stress distributions along the geometrically complex magma-rock boundary.

Such stress distributions are then employed by GALES as a set boundary conditions in elasto-dynamic simulations to compute the space-time distribution of rock displacement within the heterogeneous rock system and on the free surface. The computed synthetic time series for surface ground deformation at places corresponding to the position of actual receiver stations are finally analysed and compared to the real observational data at Mount Etna. 

The geometry of the plumbing system, the temperature and major oxide composition of the involved magmas, and their water and carbon dioxide contents, are constrained from the bulk knowledge at the highly investigated, highly monitored, well-known Etna volcano. The space-time dependent physical properties of the multiphase magmas are computed on the basis of the local composition and volatile partition between the gas and melt phases.

The results highlight the relationships between observations from surface monitoring networks and deep magma dynamics. In particular, they allow an in-depth investigation of ground oscillations with periods from seconds to hours, covering the intermediate range between seismic and geodetic observations which is being increasingly accessed to direct measurements. Such an intermediate frequency range emerges as being rich with new information on underground magma dynamics, potentially opening new perspectives and possibilities to magma monitoring and volcanic forecasts.

 

How to cite: McCluskey, O., Papale, P., Montagna, C., and Garg, D.: Relating magma dynamics and ground deformation patterns at Mount Etna, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11747, https://doi.org/10.5194/egusphere-egu24-11747, 2024.

EGU24-11770 | Orals | GMPV8.6

Interactions between an inflating magma chamber and caldera ring faults at Askja volcano, Iceland, during the 2021-2023 unrest episode 

Adriano Nobile, Hannes Vasyura‐Bathke, Daniele Trippanera, Jöel Ruch, and Sigurjón Jónsson

Unrest episodes at volcanic systems are often associated with ground displacements produced by the pressure changes inside magma chambers at depth. The interactions with preexisting faults can complicate the deformation pattern observed at the surface. Calderas are volcanic systems characterized by a surface depression formed when the roof block collapses along ring faults, triggered by the rapid depressurization of an underlying magma chamber. As caldera ring faults are zones of weakness in the subsurface, we can expect stress interactions between the magma source and the ring faults during unrest episodes or eruptions. An example of such interaction likely occurred at Askja volcano during the 2021-2023 unrest episode. 

The Askja volcanic system is located in the North Volcanic Zone of Iceland. It consists of a central volcano with three nested calderas in the middle of a fissure swarm. Geodetic data have shown that the Askja caldera floor continuously subsided from 1983 until August 2021, when the volcano entered a period of unrest with rapid uplift and increased seismic activity. The seismicity decreased after three months, while the uplift continued for two years until it substantially slowed down in September 2023.

We use Sentinel-1 SAR images to study the ground deformation at Askja volcano between 2016 and 2023. Only Summer acquisitions can be used since the area is covered by snow during the rest of the year, preventing retrieval of the deformation signal due to lack of coherence. The InSAR time series shows steady subsidence of the Askja caldera floor between July 2016 and July 2021, and then, in early August 2021, the displacement changed to uplift. In only one month, the uplift matched the subsidence of the previous five years. By September 2023, the maximum uplift reached ~70 cm in the center of Askja caldera. Deformation maps show an asymmetric pattern that follows the ring faults in the northwestern part of Askja caldera. The pattern is similar for both the subsidence and uplift periods, suggesting the same magma body deflated before the unrest and then inflated when the pressure increased in August 2021. 

Using boundary element models, we assessed the ground deformation resulting from the interaction between an inflating sill and the caldera ring faults. Then, we estimated the source parameters using Bayesian inference. While a magmatic sill source can account for the broad uplift, triggered ring fault movement localizes the deformation close to the caldera rim, yielding an asymmetric deformation pattern that better fits the observed data. 

Even if this unrest didn’t culminate in an eruption, it highlights the importance of closely monitoring this volcanic system with InSAR technique. Indeed, this provides spatial data, enabling us to observe the peculiar deformation pattern. In synergy with the mapped faults and fractures, this allowed us to better understand the volcano's behavior and interactions with the rift and obtain an accurate image of its magmatic system.

How to cite: Nobile, A., Vasyura‐Bathke, H., Trippanera, D., Ruch, J., and Jónsson, S.: Interactions between an inflating magma chamber and caldera ring faults at Askja volcano, Iceland, during the 2021-2023 unrest episode, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11770, https://doi.org/10.5194/egusphere-egu24-11770, 2024.

EGU24-12398 | Posters on site | GMPV8.6

Immersive Virtual Reality and numerical modelling application to study a dyke-induced asymmetric graben: the 1971 Mt. Etna (Italy) case 

Fabio Luca Bonali, Noemi Corti, Federico Pasquaré Mariotto, Emanuela De Beni, Sofia Bressan, Massimo Cantarero, Elena Russo, Marco Neri, and Alessandro Tibaldi

In the present study we integrated data collected using field and Immersive Virtual Reality surveys with numerical models, in order to characterise a unique dyke-induced graben system, exposed both in section and plan view, characterised by an unexpected asymmetric fault geometry. Such volcanotectonic feature was formed during the 1971 eruption and is located near the northern wall of the Valle del Bove, Mt. Etna, southern Italy.

We firstly created a new structural map obtained from the analysis of historical aerial stereophotos encompassing a time interval from before to after the 1971 eruption; afterwards, we collected quantitative data on high-resolution drone-derived 3D models and field surveys carried out in the summer of 2022. Data collection on the vertical cliff was entirely carried out thanks to Immersive Virtual Reality techniques.

In plan view, the graben is 2-km-long and its width ranges 27-143 m from the bottom to the upper part of the section view, with about 82 m of difference in elevation from top to bottom. Graben faults clearly show an asymmetric setting in terms of attitude, with one fault dipping 70° to the south, and the other one dipping 50° to the north. Vertical offset values are greater at higher elevations. We also ran a set of numerical models, aimed at investigating the distribution and orientation of stresses around the inferred dyke tip and within the host rock. Comparison between field data and numerical models suggests the key role played by the inclined topography, as shown in section view, in determining the orientation of dyke-induced σ1 and σ3 in the host rock. This, in turn, controls the geometry of the graben faults, resulting in the observed asymmetric setting. Additionally, dyke-induced stress concentrations and vertical offset values support the hypothesis of a downward propagation of the graben faults, from the surface down to the dyke tip.  

How to cite: Bonali, F. L., Corti, N., Pasquaré Mariotto, F., De Beni, E., Bressan, S., Cantarero, M., Russo, E., Neri, M., and Tibaldi, A.: Immersive Virtual Reality and numerical modelling application to study a dyke-induced asymmetric graben: the 1971 Mt. Etna (Italy) case, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12398, https://doi.org/10.5194/egusphere-egu24-12398, 2024.

EGU24-13052 | ECS | Posters on site | GMPV8.6

Characterisation of slow-spreading ridges: the Theistareykir and Fremrinamar rifts, Northern Volcanic Zone (Iceland) 

Martina Pedicini, Noemi Corti, Alessandro Tibaldi, Federico Pasquaré Mariotto, and Fabio Luca Bonali

The Northern Volcanic Zone (NVZ) of Iceland identifies the northernmost portion of the emerging Mid-Atlantic plate boundary. Its peculiar location enables us to observe the main features that characterise slow-spreading ridges directly on the field. Here we present the first outcomes on the characterisation of the structure of the NVZ, focusing on two out of the seven volcanic rifts that constitute the area, namely the Theistareykir and the Fremrinamar.

We linked field surveys and remote sensing analysis to identify and classify all the features constituting these areas (i.e. normal faults, extension fractures, and eruptive fissures) and to collect quantitative data. Information regarding structures’ azimuth, length and vertical offset (for the normal faults subset) were collected to obtain a comprehensive characterisation of the rifts’ surficial deformation. Moreover, fault-slip profiles have been realised, to evaluate the along-axis rift propagation within the studied fissure swarms.

For both rifts normal faults represent the most abundant subset, also characterised by the highest length values. The analysis of faults’ dip directions highlights a clear preponderance of E-dipping scarps within the Theistareykir rift against a predominance of W-dipping ones within the Fremrinamar rift, supporting the hypothesis that they represent rift shoulders. Within both rifts, we observed a decrease in the surficial deformation moving away from the rifts’ central volcanoes. Additionally, the interpretation of the fault-slip profile displayed the tendency of the along-axis rift deformation to move away from the central volcanoes. Within the Theistareykir, the rift intersects with the Husavik-Flatey transform Fault (HFF), generating structures showing right-lateral strike-slip components.  Within the Fremrinamar rift, however, the intersection of the rift within the Grimsey Oblique Lineament leads to a local re-orientation of structures’ strikes, without any strike-slip component. These data corroborate the hypothesis that the GRL represents the offshore propagation of the Fremrinamar rift towards the Kolbeinsey Ridge, thus having a different behavior than the HFF.

Our study could contribute to the general understanding of how slow-spreading ridges develop, with a particular focus on how volcanic and tectonic processes concur in defining rift structures.

How to cite: Pedicini, M., Corti, N., Tibaldi, A., Pasquaré Mariotto, F., and Bonali, F. L.: Characterisation of slow-spreading ridges: the Theistareykir and Fremrinamar rifts, Northern Volcanic Zone (Iceland), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13052, https://doi.org/10.5194/egusphere-egu24-13052, 2024.

EGU24-13366 | ECS | Posters on site | GMPV8.6

Seismic response to volcanic processes at Mount Etna: coupling thermomechanical simulations with seismic wave-equation modelling 

Michelle Bensing, Sergio Vinciguerra, Giuseppe Puglisi, and Luca De Siena

Mt. Etna, located in the north-eastern area of Sicily (Italy), is one of the most active and hazardous strato-volcano in the world, both in terms of paroxysmal events and continuous effusive activity from the summit area and hazardous flank eruptions. Long-term processes of deep magma recharge and storage within the upper crust, passive magma ascent along pre-existing weaknesses, and forceful dyke intrusions allow magma to rise to the surface. Past studies provided evidence supporting the view that the interplay between magma dynamics and storage and the thermomechanical response of the host medium control magma rise and the brittle seismic response of the volcano basement and edifice.

To investigate this interplay, we created a 3D thermomechanical geodynamic model of Etna and the ground deformation response to different geological processes such as magma intrusion, gravitational spreading and main fault systems, especially with regard to the sliding of the southeastern flank. We used the Lithosphere and Mantle Evolution Model (LaMEM) code and achieved a higher model resolution by containerizing the code on the Open Computing Cluster for Advanced data Manipulation (OCCAM), an HPC cluster operated by the University of Turin and the Sezione di Torino of the Istituto Nazionale di Fisica Nucleare.

The model domain covers 41 x 39 x 14km in x, y and z direction and has two greater crustal layers with a horizontal boundary at z = 3.6km, which are inferred from laboratory results, with real topography implementation. The geometry of the flank and the position of the northern and southern fault boundary layers are based on geological evidences. Below the flank is a similar geometry that should function as a weakzone and control the sliding of the flank. Geometry and position of the high-velocity and fluid/gas pockets are based on Vp and Vp/Vs. The position of the two magma storages are inferred from geodetic outcomes. As LaMEM framework allows retrieving both deformation and gravity responses to the final model, we are currently achieving model results that ideally fit the actual GPS data recorded over 20 years in order to determine the rheological laws driving the long-term deformation.

How to cite: Bensing, M., Vinciguerra, S., Puglisi, G., and De Siena, L.: Seismic response to volcanic processes at Mount Etna: coupling thermomechanical simulations with seismic wave-equation modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13366, https://doi.org/10.5194/egusphere-egu24-13366, 2024.

EGU24-13429 | Posters on site | GMPV8.6

Analyzing Seismic Signals of the 2021 Dayoukeng Mud Ejection in Northern Taiwan 

Ya-Chuan Lai, Min-Hung Shih, Cheng-Horng Lin, and Hsiao-Fen Lee

The research findings indicate that the Dayoukeng area is the most active region in the Tatun Volcano Group, Taiwan. In early 2022, mud ejecta was discovered near the main fumarole, indicating heightened activity. Comparative geochemical analysis revealed an abnormal increase in the cation concentration of hot spring at the end of 2021. Real-time webcam further identified additional steam activity above the main vent between Dec 12, 2021 and Jan 2, 2022. It is speculated that during this period, Dayoukeng may have experienced intensified steaming. A nearby network with dense seismic Zland nodes offers a unique opportunity to detect the signals during this anomalous activity in Dayoukeng. By scrutinizing and comparing the characteristics of these signals, we try to decipher the temporal variations of the sequence.

The data from nearby stations indicate a gradual increase in Dayoukeng’s activity starting from Dec 8, 2021. Initially, there is a gradual increase in signals, predominantly microearthquake within Dayoukeng. Subsequently, a notable increase in signals, characterized by a combination of seismic and acoustic signals, is observed. On Dec 12, microtremors possibly associated with mud ejections are detected. Following this, there is a repetitive occurrence of the previous seismo-acoustic observations, each enduring for several hours, persisting until a few days later. Such seismic data of dense short-period seismic network provides a chronological sequence of the Dayoukeng event, thereby facilitating the subsequent model for the entire event.

How to cite: Lai, Y.-C., Shih, M.-H., Lin, C.-H., and Lee, H.-F.: Analyzing Seismic Signals of the 2021 Dayoukeng Mud Ejection in Northern Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13429, https://doi.org/10.5194/egusphere-egu24-13429, 2024.

EGU24-13606 | ECS | Orals | GMPV8.6

The role of regional stress and pre-existing faults on collapse caldera onset and architecture 

Matias Villarroel, John Browning, Martin Schöpfer, Carlos Marquardt, and Pamela Jara

Collapse calderas form when the roof of the magma chamber collapses downwards as a consequence of magma withdrawal due to either over- or underpressure within the chamber during large eruptions. Caldera morphology, orientation, and internal architecture can be influenced by the tectonic conditions within the crust. Various theoretical, field, and modeling studies have suggested that collapse calderas are shaped by a combination of outward-dipping reverse faults and inward-dipping normal faults. However, the role of the regional stress field and pre-existing crustal faults in shaping a caldera or modifying the conditions of fault nucleation is less clear. This is important since many calderas form in areas that are subjected to regional stresses and of intense crustal faulting. This study utilizes two-dimensional Distinct Element Method (DEM) models to explore the influence of regional stresses and pre-existing structures on collapse caldera evolution and resulting geometric style. To do so we model a crustal segment comprised of a shallow magma chamber that gradually decreases in volume, mimicking the process of magma withdrawal. To address the interplay between the stress regime and the dynamics of caldera collapse we applied the Rankine Stress Limit to Coulomb's friction law, which relates the shear stress (τ) to the effective normal stress (σ’n). This provides both active (ka) and passive (kp) limit stress states for a cohesionless material, by assuming a critically stressed crust with a friction angle 𝜙, thus it is defined the earth pressure coefficient (𝑘) being the horizontal (σh) to vertical (σv) effective stress ratio: k = σh /σv. For a cohesionless rock mass with friction angle 𝜙 the coefficients are: ka = 1–sin𝜙/1+sin𝜙 = 1/kp. Therefore, k is 1 for the isotropic case, k < 1 for extension (ka) and k > 1 for compression (kp). The effective vertical stress is, for a normally pressurized rock mass, given by: σv = ρ’gh, where ρ’ = ρbulk–ρfluid is the buoyant density, g is gravity and ℎ the depth. Pre-existing faults are represented by cutting the rigid blocks and assigning contact properties to the resulting facets. Our findings demonstrate that both the critical underpressure for collapse onset and the internal architecture of calderas are significantly influenced by the regional stress field of the crustal segment in which they are embedded. Moreover, the pre-existing faults do change both the geometry and style of collapse indicating an important role during caldera formation. By testing various fault spacings and properties, we identified parametric ranges within which pre-existing faults either contribute to or refrain from influencing the overall collapse geometry. These findings hold significance in reconstructing the underlying processes from well-preserved collapse calderas and in comprehending the conditions required for future collapses at potential caldera volcanoes.

How to cite: Villarroel, M., Browning, J., Schöpfer, M., Marquardt, C., and Jara, P.: The role of regional stress and pre-existing faults on collapse caldera onset and architecture, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13606, https://doi.org/10.5194/egusphere-egu24-13606, 2024.

EGU24-14543 | Orals | GMPV8.6

Episodic events of oblique rifting using InSAR time series and seismicity (2016 – 2023), Reykjanes Peninsula (Iceland)  

Xingjun Luo, Nicolas Oestreicher, Wenbin Xu, and Joël Ruch

Oblique rift zones and bookshelf structures in the Reykjanes Peninsula are part of the intricate boundary that separates the North American from the Eurasian plates. Studying their evolution over several years provides a deeper understanding of plate tectonic processes and also aim to better understand the tectonic conditions that precede volcanic eruptions. After a period of dormancy lasting 800 years, the Reykjanes Peninsula has experienced strong episodic plate boundary motions since at least 2017 and four eruptions in 2021, 2022, and 2023 (twice). These events have been accompanied by significant seismic activity and ground displacement related to strain release at the plate boundary and around dike intrusions.

Here we employed D-InSAR, stacking-InSAR, and PSI time series to investigate the deformation occurring in the Reykjanes Peninsula from June 2016 to December 2023, covering the period before and during the onset of the eruption phases. Due to the fast deformation during large earthquakes and eruptions, we separately analyze dike intrusions before the four eruptions, five earthquake swarms, and seven time series between the above-mentioned events. The discretization of the observation period allows us to improve the InSAR process for different events and to avoid confusing the deformations originating from different events. Using InSAR and seismicity, we identifiund displacement and earthquake swarms in the Fagradalsfjall area in July 2017, July 2020, August 2020 and October 2020, highlighting an activation of localized portions of the plate boundary at least four years before the first eruption. The overall earthquake distribution aligns with the plate boundary (N070), but suggests a bookshelf structure composed of north-south fault ruptures.

We use the vbmethod to decompose the InSAR time-series into independent components of deformation such as intrusions, earthquakes, and tectonic plate motion. From the InSAR time series analysis, we observed that before each dike intrusion, the Southern Fagradalsfjall-Krysuvik () area exhibits an overall southeastward movement. The results of vbICA also suggest that this area has been accelerating since 2020.  

The comprehensive observations of tectonic and volcanic activity in the Reykjanes Peninsula, using both InSAR time series and seismicity over seven and a half years provide valuable insights to better understand the onset of oblique rifting events at divergent plate boundaries.

How to cite: Luo, X., Oestreicher, N., Xu, W., and Ruch, J.: Episodic events of oblique rifting using InSAR time series and seismicity (2016 – 2023), Reykjanes Peninsula (Iceland) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14543, https://doi.org/10.5194/egusphere-egu24-14543, 2024.

EGU24-16352 | ECS | Orals | GMPV8.6

Co-eruptive crustal deformation changes associated with the 2021 Fagradalsfjall eruption (SW-Iceland) 

Chiara Lanzi, Halldór Geirsson, Freysteinn Sigmundsson, Michelle Maree Parks, and Vincent Drouin

Ground deformation during an eruption may help to interpret physical processes related to the plumbing system. Here, we report the co-eruptive deformation of the Fagradalsfjall (SW-Iceland) eruption in 2021, that occurred in an oblique rift zone. The eruption lasted six months, 19 March - 21 September, following several weeks of intense seismic activity. The spatial and temporal analysis of Global Navigation Satellite System, GNSS, and Interferometric Synthetic Aperture Radar, InSAR, (by Sentinel-1) observations of ground displacements locate changes in the deformation pattern during the eruptive period. Three temporal changes in the subsidence rates and horizontal motion towards the eruptive area are identified: the first period, T1, 19 March–12 May; the second period, T2, 12 May–30 July, and the third period, T3, 30 July–21 September. The maximum deformation rate (20 mm/yr in line-of-sight) is observed in T2 and coincides with the average effusive rate increase (from 8 m3/s in March–April to 9–13 m3/s in May, Pedersen et al., 2022). We jointly inverted the GNSS and InSAR data to place constraints on the size and location of the source of subsidence during the six-month eruption. Initial modelling result (InSAR and GNSS) indicates a point-source at mid-crust level, 9.5-10.5 km depth and a volume decrease of 18-21 × 106 m3. The deflation volume estimated is significantly lower than that of the lava flow field, with a bulk volume of 150 ± 3 × 106 m3of lava (Pedersen et al., 2022). A residual signal is observed in our model, centered above the source location and around the eruptive center. Both the residual signal and the lower-than-expected volume change suggest additional inflow from a deeper source in agreement with evidence of physical mixing of magma from a mantle supply after the start of the eruption (Halldórsson et al., 2022). A link to a deeper source influences the influx rate of the magma and, consequently, the magma available. Both local seismicity rate and seismic moment release gradually decreases between the onset of the eruption and late April. Afterwards, both show a relatively constant rate, until the end of the eruption.

 

 

 

 

Pedersen, G., Belart, Joaquín M.C., Óskarsson, B., Gudmundsson, M. et al (2022). Volume, Effusion Rate, and Lava Transport During the 2021 Fagradalsfjall Eruption: Results From Near Real‐Time Photogrammetric Monitoring. Geophys. Res. Lett., 49. 10.1029/2021GL097125.

 

Halldórsson, S.A., Marshall, E.W., Caracciolo, A. et al. (2022). Rapid shifting of a deep magmatic source at Fagradalsfjall volcano, Iceland. Nature 609, 529–534 https://doi.org/10.1038/s41586-022-04981-x

How to cite: Lanzi, C., Geirsson, H., Sigmundsson, F., Parks, M. M., and Drouin, V.: Co-eruptive crustal deformation changes associated with the 2021 Fagradalsfjall eruption (SW-Iceland), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16352, https://doi.org/10.5194/egusphere-egu24-16352, 2024.

EGU24-16539 | ECS | Posters on site | GMPV8.6

Compaction and creep deformation of volcaniclastic material during burial  

Edgar U. Zorn, Anthony Lamur, Jackie E. Kendrick, Ulrich Kueppers, and Yan Lavallée

Volcaniclastic deposits compact during accumulation and burial, causing prolonged ground deformation, and potentially affecting edifice stability. Here we present the results of laboratory compaction experiments in which volcaniclastic material (in a confining cup) was progressively loaded with 0.1 MPa/min up to 20 MPa. We tested two lithologies consisting of natural basanitic scoria and crushed hyaloclastite, each sieved to a set of two grain sizes in the ash (0.5-2 mm) and lapilli (2-4 mm) range. During experiments, axial deformation and acoustic emissions were monitored, enabling us to quantify the progressive volume reduction and material properties. Two types of experiments were performed: dynamic loading tests and static creep test. The dynamic tests show that most of the deformation takes place within the first few MPa, decreasing non-linearly with load. Ultimately, samples compacted by up to 50 vol.% at 20 MPa (here equivalent to ~1,400 m depth). We use this compaction data to build a model of compaction and material properties as function of burial depth.

In repeat experiments, static tests were undertaken at select target loads (2, 5, 10 and 20 MPa) to measure time-dependent creep deformation at these loads over 6 hours. We find that compaction continues under static load as creep occurs in stages, displaying (1) initially rapid decline in compaction strain rates, which (2) then diminish more slowly over time and (3) eventually reach stable creep strain rates in most of our tests. Moreover, both total creep strains and stable creep rates are dependent on the applied load. Stable strain rates were highest between 5 and 10 MPa for all samples. The data shows that the lithology also influences the deformation behavior as we found the hyaloclastites compacted more efficiently during initial loading compared to the scoria, but in-turn creep strain rates were nearly an order of magnitude lower due to the more efficient compaction during loading. Our results highlight the relevance of gravitational material compaction for investigations of ground deformation and volcano flank instability (e.g., measured with InSAR) and introduce new material constraints to improve the interpretation and analysis of such signals. Deposit-specific compaction data may be integrated with ground deformation monitoring to interpret flank instabilities and assess collapse hazards, particularly in eruptions where deposition of new materials rapidly shifts overburden stresses.

How to cite: Zorn, E. U., Lamur, A., Kendrick, J. E., Kueppers, U., and Lavallée, Y.: Compaction and creep deformation of volcaniclastic material during burial , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16539, https://doi.org/10.5194/egusphere-egu24-16539, 2024.

EGU24-16777 | ECS | Posters on site | GMPV8.6

Hydrothermal alteration shifting brittle-ductile transition promotes volcanic flank collapses 

Jens Niclaes, Pierre Delmelle, and Hadrien Rattez

Volcanoes are inherently unstable, causing tremendous catastrophes, such as cities destruction or large tsunamis creation. These large flank collapses are not one-time events, it happens cyclically over the life of a volcano. One of the potential causes of such phenomena is hydrothermal alteration: Reactive fluids coexisting with a heat source interact with the host rocks and modify their mechanical properties. In most volcanoes, these hydrothermal alterations have a negative impact on the brittle-ductile transition of volcanic rocks, promoting a ductile failure behavior instead of a brittle one. However, the mechanisms behind large volcanic flank collapse are still obscure, especially when hydrothermal alteration is involved. The influence of the transition of mechanical behavior is rarely considered when the stability of the volcano is assessed. We performed Finite Element Method simulations, in dry and wet conditions, on 2D and 3D geometries of the Tutupaca volcano before its collapse at the end of the 18th century. To assess the stability, the strength reduction method was applied for each configuration allowing the obtention of the factor of safety and the most critical failure mechanism. The collapse is best reproduced when the volcanic rocks are modeled as a Mohr-Coulomb material with a compressive cap. The cap offers the consideration of the low brittle-ductile transition observed in previous experimental studies of altered volcanic rocks. Our results demonstrate that hydrothermal alteration influences the stability of a volcano through the brittle-ductile transition variation. These results are an entry point into assessing the instabilities of volcanoes because of hydrothermal alteration. They consider silicic and argillic alterations, but many others exist, and they might alter the rocks in a different way than reducing the brittle-ductile transition. These preliminary results are a basis to start adding complexity with, for example, external events such as earthquakes or meteorologic changes. 

How to cite: Niclaes, J., Delmelle, P., and Rattez, H.: Hydrothermal alteration shifting brittle-ductile transition promotes volcanic flank collapses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16777, https://doi.org/10.5194/egusphere-egu24-16777, 2024.

EGU24-17383 | ECS | Posters on site | GMPV8.6

What controls inter-rift volcanism? 

Valentina Armeni, Lorenzo Mantiloni, Valerio Acocella, Eleonora Rivalta, Bodo Bookhagen, and Manfred R. Strecker

Volcanic activity in extensional geodynamic settings manifests itself in in-rift, off-rift, and inter-rift areas; the latter coinciding with structurally complex transfer zones between two rift segments. While in- and off-rift volcanism has been associated with the competition between tensional crustal stresses and gravitational unloading pressure, volcanism in inter-rift zones is still not adequately understood.

Here, we combine modelling and data from natural cases to test whether topographic highs in the inter-rift zone may control magma trajectories. We performed six analogue experiments tracking the propagation of air-filled cracks in gelatine by imposing three boundary conditions: differential tensile stresses, pre-existing anisotropies, and asymmetric and symmetric inter-rift topography. Next, we compared our results with Digital Elevation Model (DEM) analyses of young volcanic provinces such as the Virunga complex (Rwanda), the Adda’do magmatic segment (Ethiopia), and the Eifel (Germany).

Analogue results show different outcomes depending on the imposed boundary conditions. When only a differential tensile stress is applied, the air-filled crack trajectories tend to align perpendicular to the least principal stress (σ3) and focus on the centre of the gelatine box. In contrast, where inter-rift topography exists, the high sectors progressively attract the trajectories along the strike of the rift. Therefore, when injection occurs below the rift centre, magma is deflected across-rift, toward an off-rift location. Conversely, when magma injection occurs below the rift tip, magma is deflected along-rift, in the inter-rift zone. Finally, the spatial patterns of the air-filled cracks obtained by our modelling are consistent with the results of the DEM analysis of the three study areas, where volcanic activity focuses on the inter-rift segments and shifts away from the rift tips and axis as the rift widens and deepens.

How to cite: Armeni, V., Mantiloni, L., Acocella, V., Rivalta, E., Bookhagen, B., and Strecker, M. R.: What controls inter-rift volcanism?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17383, https://doi.org/10.5194/egusphere-egu24-17383, 2024.

EGU24-17868 | ECS | Orals | GMPV8.6

A mechanical model for lava dome deformations using the visco-poroelastic damage rheology  

Mehdi Nikkhoo and Vladimir Lyakhovsky

The eruption style and structural stability of lava domes are determined by the mechanical strength (rigidity), porosity and temperature of their constituent magmas and the stress (pressure) and strain rates acting on them. Both rigidity and porosity of dome materials evolve with time as a result of (1) formation of new micro-fractures (damage) due to cooling and/or increasing strain rates (causing rigidity decrease and porosity increase) and (2) large effective pressures (causing porosity decrease and compaction) in lava domes. The interaction between damage and porosity may lead to different deformation modes including transition between brittle or ductile behavior in the same material even at constant temperature, pressure and strain rate. We use a visco-poroelastic damage model to quantify the evolution of damage and porosity and their interactions in lava domes. The model is based on thermodynamic principles and uses a non-linear continuum mechanics formulation which predicts different effective elastic moduli for a solid when the loading changes from tension to compression. The model accounts for the temporal evolution of damage and porosity, damage-porosity interaction and gradual accumulation of irreversible deformation due to damage-related viscosity. Thus, the model can simulate a wide range of deformation mechanisms including local damage increase and strain localization leading to brittle failure, and cataclastic flow characterized by homogeneous damage increase and porosity decrease (inelastic compaction). We apply this continuum damage-porosity model to lab experiments on lava samples form Volcán de Colima (Mexico) and Galeras volcano (Colombia). We show that the model allows us to distinguish the contributions of different deformation mechanisms in the course of each experiment. For each volcano, we compare the model parameters constrained by the lab experiments and discuss the implications of the results for up-scaling the model and performing natural-scale simulations of lava dome deformations. 

How to cite: Nikkhoo, M. and Lyakhovsky, V.: A mechanical model for lava dome deformations using the visco-poroelastic damage rheology , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17868, https://doi.org/10.5194/egusphere-egu24-17868, 2024.

EGU24-18083 | Orals | GMPV8.6 | Highlight

Interpreting seismicity and earthquake locations during the recent unrest on the Reykjanes Peninsula in SW-Iceland 

Kristín Jónsdóttir, Halldór Geirsson, Benedikt Halldórsson, Kristín Vogfjörð, Michelle Parks, Sigurlaug Hjaltadóttir, Vincent Drouin, Ragnar Heiðar Þrastarson, Benedikt G. Ófeigsson, Magnús Tumi Guðmundsson, Lilja Magnúsdóttir, Sara Barsotti, Freysteinn Sigmundsson, and Matthew Roberts

The Reykjanes Peninsula in SW Iceland is transacted by a divergent plate boundary with oblique spreading. Volcanic unrest periods, marked by fissure eruptions widely across the peninsula, seem to occur with regular intervals, approximately every 800-1000 years. These volcanic unrest periods have durations of 100 up to 400 years. In 2020, it became clear that magma was on the move again after 800 years of quiescence, as repeated uplift was measured in the vicinity of the Svartsengi geothermal area. Minor subsidence was recorded between uplift periods and seismicity increased again, only after the previous state of uplift had been surpassed, in line with the so-called Kaiser effect. A year later, a dike intrusion in Fagradalsfjall triggered earthquake activity tens of km away as stored tectonic stresses along the peninsula were released. After a clear decline in earthquake activity, an eruption took place in Geldingdalir, Fagradalsfjall, on 19 March 2021, the first one in over 6000 years in that region. At the time of writing, 4 volcanic eruptions have occurred since 2021 and in total roughly 20 magmatic intrusive events have taken place on the Reykjanes Peninsula.

Recently an escalation in volcanic activity has been observed. In late October 2023, the 5th period of uplift started in Svartsengi signifying faster magma inflow rates than previously inferred. Seismicity increased and was widespread in line with increased stresses above an inflating sill at about 5 km depth.  On 10-11 November, during nearly 12 hours of intense seismic activity, the magma found its way from the magma storage beneath Svartsengi some 2 km laterally  towards the center of an old crater row and creating a 15 km long shallow dike. Subsidence was observed above Svartsengi as the magma was drained from beneath and a graben formed beneath the coastal town of Grindavík where extensive faulting caused considerable damage. On 18 December, a similar but smaller magma intrusive event originating in Svartsengi occurred, causing an eruption approximately at the center of the original dike. This time, earthquakes only occurred about 90 minutes before the eruption onset and no clear trend of earthquakes migrating from Svartsengi towards the laterally offset dike were detected. At the time of writing (10 January, 2024), a similar amount of magma volume is inferred to have accumulated beneath Svartsengi since shortly before the last eruption, however, seismicity is still at normal background levels. 

The volcano monitoring team at the Icelandic Meteorological Office in close collaboration with geoscientists at the Insitute of Earth Science at the University of Iceland and HS Orka, have been under immense pressure to interpret the ongoing activity. A vital part has been to interpret seismicity rates and earthquake locations and any changes thereof, along with modeling dike and sill inflow rates from geodetic measurements. We show that meaningful interpretation of earthquake activity can only be done when jointly interpreted together with deformation and stress models as stress changes heavily influence earthquake locations and the temporal onset of earthquake activity.

How to cite: Jónsdóttir, K., Geirsson, H., Halldórsson, B., Vogfjörð, K., Parks, M., Hjaltadóttir, S., Drouin, V., Þrastarson, R. H., Ófeigsson, B. G., Guðmundsson, M. T., Magnúsdóttir, L., Barsotti, S., Sigmundsson, F., and Roberts, M.: Interpreting seismicity and earthquake locations during the recent unrest on the Reykjanes Peninsula in SW-Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18083, https://doi.org/10.5194/egusphere-egu24-18083, 2024.

EGU24-18235 | Orals | GMPV8.6

Deformation patterns of the Reykjanes Peninsula unrest 2020-2024, Iceland: evidence for interconnected neighboring volcanic systems 

Halldór Geirsson, Michelle M Parks, Freysteinn Sigmundsson, Vincent Drouin, Benedikt G Ófeigsson, Chiara Lanzi, Áslaug G Birgisdóttir, Cécile Ducrocq, Andrew Hooper, Páll Einarsson, Kristín Jónsdóttir, Sigrún Hreinsdóttir, and Sonja H M Greiner

Neighboring volcanic systems sometimes show evidence of some form of interconnection, for example by inflating or deflating either in phase or in anti-phase. We review here the course of events on the Reykjanes Peninsula (RP) in the ongoing unrest since approximately 2020, using volcano geodesy.

There are several volcanic systems on the RP, from west to east: Reykjanes, Svartsengi, Fagradalsfjall, Krýsuvík, Brennisteinsfjöll, and Hengill, with Fagradalsfjall being the least developed. All these volcanic systems, except Brennisteinsfjöll, have shown signs of unrest in the past years and decades: Three uplift episodes occurred at Svartsengi during 2020; one or two subtle deformation events further west on Reykjanes in 2020, and further uplift episodes at Svartsengi in May 2022, October 2023, November 2023, and December 2023 - January 2024. Inflation was observed at Krýsuvík during the summer of 2020; and a M5.6 earthquake occurred in Krýsuvík in October 2020.

As of beginning of 2024, three eruptions have occurred at Fagradalsfjall (in 2021, 2022, and 2023) and one eruption at Svartsengi in December 2023. Each eruption has been preceded by a dike intrusion, often intertwined with complex patterns of faulting, near-surface fracturing over wide areas, and creep along segments of the plate boundary. Additional dike intrusions in December 2021 in Fagradalsfjall and in Svartsengi in November 2023 did not breach the surface. The dike growth has spanned timescales of just over an hour to several weeks; furthermore, small dikelets accompanied new vent openings during the 2021 eruption. The dikes were emplaced in the brittle crust, above ~8 km depth, spanned several decimeters to meters in thickness, and released locally a great amount of plate-tectonic stresses. Re-inflation following each eruption or dike intrusion is usually observed, however, the temporal style of uplift rates varies considerably from time to time. Co-eruptive deflation was observed during the 2021 Fagradalsfjall eruption and the 2023 Svartsengi eruption.

The detailed deformation observations and modeling for the unrest periods reveal complex interactions of tectonics and magmatism across several volcanic systems on the RP. During 2020-2024, localized deformation and seismicity have alternated between different volcanic systems on the RP, such that only one system is inflating or erupting at a time. This observation may be interpreted in terms of deep pressure coupling between the systems. Furthermore, the deformation events cause significant stress changes at neighboring volcanic systems, affecting the probability of dike propagation and seismicity as well as conditions for magma accumulation. 

How to cite: Geirsson, H., Parks, M. M., Sigmundsson, F., Drouin, V., Ófeigsson, B. G., Lanzi, C., Birgisdóttir, Á. G., Ducrocq, C., Hooper, A., Einarsson, P., Jónsdóttir, K., Hreinsdóttir, S., and Greiner, S. H. M.: Deformation patterns of the Reykjanes Peninsula unrest 2020-2024, Iceland: evidence for interconnected neighboring volcanic systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18235, https://doi.org/10.5194/egusphere-egu24-18235, 2024.

EGU24-18471 | ECS | Posters on site | GMPV8.6

Gales: a multiphysics code for volcanic deformation 

Deepak Garg, Paolo Papale, Antonella Longo, and Chiara Montagna

Ground deformation in volcanic settings can reflect pressurizing/depressurizing subsurface magma bodies, which could have geometries ranging from spheroid-like fluid-filled reservoirs to complex networks of dikes, sills, and crystal mush regions.  Having accurate forward models of deformation is important for resolving magma storage geometries and understanding stress states that influence the stability of volcanic areas and any potential eruption activity. In this regard, the finite element method (FEM) has enjoyed wide popularity due to its robustness and accuracy of results in handling of arbitrary geometries.  

We have developed an open-source hpc multiphysics finite element code Gales for solving a wide variety of PDEs. The code is parallelized using OpenMPI, aimed at multi-node (distributed memory architecture) machines. The software is written in modern C++ and can be used on a single desktop as well as on large clusters. The code offers to do static, quasistatic, and dynamic analysis for linear and non-linear elastic rock deformation in 2D/3D. The software can account for heterogeneous rock properties, real topography, and geometrical complexities associated with multiple magmatic reservoirs, connecting dykes, and volcanic conduits. 

The equations are solved using standard Galerkin FEM. For transient problems, temporal discretization is done using the second-order accurate generalized alpha method. The code has been verified on several test cases covering engineering benchmarking to problems with analytic solutions.

A recent validation exercise on "Drivers of Volcano Deformation", participated by an ample community worldwide, demonstrated Gales as one of the best open-source codes for providing accurate solutions for all exercises, with performance comparable with that of the commercial Comsol software in any individual application.

How to cite: Garg, D., Papale, P., Longo, A., and Montagna, C.: Gales: a multiphysics code for volcanic deformation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18471, https://doi.org/10.5194/egusphere-egu24-18471, 2024.

EGU24-18593 | ECS | Orals | GMPV8.6

Evaluating the North-South deformation component from DInSAR data in volcanic framework. 

Andrea Barone, Maurizio Fedi, Antonio Pepe, Pietro Mastro, Pietro Tizzani, and Raffaele Castaldo

Nowadays, modeling ground deformation field is a widely used strategy for monitoring volcanic areas since Differential Synthetic Aperture Radar Interferometry (DInSAR) technique provides maps and time-series with satisfactory spatial and temporal resolutions. In particular, in the case of SAR images acquisitions along both satellites orbits, the estimated information is the East-West and vertical components of the related three-components ground deformation field. The deformation along the North-South direction (i.e., along track) is therefore usually not available; while different techniques have been proposed to solve this task, the resolutions and accuracies of these retrieved measurements are not always satisfactory.

We propose a novel methodology for the imaging of the North-South deformation related to volcanic environments and, therefore, the retrieval of the three-component ground deformation field. In particular, we employ the theory of the potential functions on deformation in order to use the integral transforms of potential fields and recover the North-South component.

The proposed workflow is here tested on simulated deformation datasets by considering the commonly used analytic volcanic deformation sources, such that Mogi’s, Okada’s and Yang’s models. The outcomes of the simulations prove that the use of the potential functions theory allows the imaging of the North-South component of deformation with negligible errors with respect to the expected one.

We finally use this new methodology for studying the Sierra Negra volcano (Galapagos Islands, Ecuador) and retrieving the three-component of ground deformation field occurred during the 2017 – 2018.5 unrest, which has preceded the eruption. Specifically, we perform a comparison with GNSS data by showing that the proposed technique is able to image the pre-eruptive North-South component of deformation with a mean error of about 5% for this case-study, which is a surprising result for this kind of application.

We conclude by specifying the next step of this study, which will be based on the modeling of volcanic deformation sources through the use of the inferred three-component ground deformation field.

How to cite: Barone, A., Fedi, M., Pepe, A., Mastro, P., Tizzani, P., and Castaldo, R.: Evaluating the North-South deformation component from DInSAR data in volcanic framework., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18593, https://doi.org/10.5194/egusphere-egu24-18593, 2024.

EGU24-19088 | Orals | GMPV8.6

Locating the Auckland Volcanic Field's magma reservoir through magma pathway retrogression 

Eleonora Rivalta, Lorenzo Mantiloni, Geoff Kilgour, Sigrún Hreinsdóttir, Jennifer Eccles, Ian Hamling, and Michael Rowe

The Auckland Volcanic Field (AVF) consists of ~53 volcanoes, distributed over an area of ~ 360 km2. Located within the AVF is Auckland City, New Zealand’s largest population centre (~1.7M people), highlighting the need to adequately model future pre-eruption scenarios for enhanced preparedness. Geological evidence shows that past eruptions were variably explosive and formed maars, lava shields, and tuff rings, largely controlled by the extent of magma-water interaction. Any future eruption from a new vent location within the AVF would cause significant socio-economic impacts, extensive evacuations, and national-scale impacts. Our work aims to constrain the next probable vent location using novel physics-based approaches.

Current approaches to identifying the next AVF vent location use statistical analysis to define probability maps. Here we use a novel approach based on physical understanding of dyke propagation and newly developed 3D numerical codes that consider crustal stresses as the main controls on the orientation of dyke pathways. We estimate regional stresses based on GNSS data and consider surface mass redistributions at the Hauraki Rift and other volcano-tectonic structures in the wider area to constrain the overall elastic stress field. We backtrack magma pathways from known vent locations downward through the crust. Pathways are oblique and reach below the Hauraki Gulf or Firth of Thames (~30 km E of Auckland City) at the inferred depth of magma dyke release (35-50 km). We infer a common magma source is physically plausible in that location.

Further work will improve the robustness of the model, constrain the spatial spread of vents over time, dyke propagation velocity, and implications for early identification of future volcanic unrest.

 

How to cite: Rivalta, E., Mantiloni, L., Kilgour, G., Hreinsdóttir, S., Eccles, J., Hamling, I., and Rowe, M.: Locating the Auckland Volcanic Field's magma reservoir through magma pathway retrogression, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19088, https://doi.org/10.5194/egusphere-egu24-19088, 2024.

EGU24-19494 | ECS | Posters on site | GMPV8.6

The influence of hotspot topography on mega-dyke propagation: theory and models 

Tim Davis, Richard Katz, Adina Pusok, and Yuan Li

Radial mega-dyke swarms, found on Earth, Mars and Venus, radiate away from a central source in an asterisk-like pattern. Individual mega-dykes can reach lengths of 100s of kms and up to 100 metres in width (Ernst and Baragar, 1992), yet this similarity in the characteristic length among dykes of an individual swarm over such long distances remains enigmatic. In this study, we present theory and numerical models of dyke length. Here we hypothesise that the level of neutral buoyancy is inclined, allowing dykes to flow downslope. We postulate that the source of this inclination is crustal doming above a rising hotspot swell.

Existing models of fractures perched at their level of neutral buoyancy show the final length of the fracture L is highly dependent on the initial chamber pressure p, L∝p7/2 (Bolchover and Lister, 1999). Changes in this pressure of 10’s of MPa can cause the final length of the fractures to extend between the metre scale to 1000’s of kilometres. This suggests that the chamber pressure would have to be very stable for the injection of all dykes in a given array. In our model we will show that when the dyke propagates downslope then the dyke length is less sensitive to this source pressure. In our model, the wall rock deforms elastically but breaks when the fracture toughness is exceeded. Lubrication theory is used to model the flow within the dyke and the magma is allowed to solidify on contact with the wall. We simulate the dykes using PyFrac (Zia and Lecampion, 2020) and a simplified scheme akin to a pseudo-3D hydro-fracture model (Adachi et al., 2010). We derive equations to describe the energy sources and sinks driving the dyke to propagate laterally.

We show how the dyke height and speed increases as the slope of the level of neutral buoyancy is increased. Using our energy analysis, we show that for a dyke propagating down a constant slope the dissipation is balanced by the gravitational potential energy, resulting in a near constant tip speed. Retrieving the dyke tip speed from the model we estimate the final length of the dyke. We show that for dykes driven laterally by a stress gradient the final length is less sensitive to the magma chamber pressure. Our results show quantitatively how radial mega-dyke arrays are related to ground deformation above a rising hotspot head.

Adachi, J.I., Detournay, E. and Peirce, A.P., 2010. Analysis of the classical pseudo-3D model for hydraulic fracture with equilibrium height growth across stress barriers. International Journal of Rock Mechanics and Mining Sciences, 47(4), pp.625-639.

Bolchover, P. and Lister, J.R., 1999. The effect of solidification on fluid–driven fracture, with application to bladed dykes. Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences, 455(1987), pp.2389-2409.

Ernst, R.E. and Baragar, W.R.A., 1992. Evidence from magnetic fabric for the flow pattern of magma in the Mackenzie giant radiating dyke swarm. Nature, 356(6369), pp.511-513.

Zia, H. and Lecampion, B., 2020. PyFrac: A planar 3D hydraulic fracture simulator. Computer Physics Communications, 255, p.107368.

How to cite: Davis, T., Katz, R., Pusok, A., and Li, Y.: The influence of hotspot topography on mega-dyke propagation: theory and models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19494, https://doi.org/10.5194/egusphere-egu24-19494, 2024.

EGU24-19503 | Posters on site | GMPV8.6

Structural elements from gravity and magnetic data in the Phlegrean Fields 

Giovanni Florio, Maurizio Fedi, Mauro Di Vito, Federico Cella, and Valeria Paoletti

A comprehensive analysis of the gravity and magnetic fields of the Phlegrean Fields volcanic area reveals a complex structural setting. High resolution techniques, including multiscale boundary analysis and field transformations, highlight the position of density and magnetization boundaries of the Phlegrean Fields. The structural elements of the two datasets appear in a general agreement, but at the same time present differences, so yielding a complex and rich picture of the collapsed Phlegrean caldera and of the surrounding areas. Inside the caldera, a good consistence among some structural elements identified from our analysis and the seismicity can be established. Some hypotheses about the geological significance of the gravity and magnetic anomalies in the frame of the Phlegrean volcanological context are finally set up.

How to cite: Florio, G., Fedi, M., Di Vito, M., Cella, F., and Paoletti, V.: Structural elements from gravity and magnetic data in the Phlegrean Fields, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19503, https://doi.org/10.5194/egusphere-egu24-19503, 2024.

ISVOLC is a 12 partner research project funded by the Icelandic Research Fund, addressing the effects of climate change-induced ice retreat on seismic and volcanic activity. The project started 1 April 2023, and has a duration of 3 years. It is led by the Icelandic Meteorological Office, in collaboration with the University of Iceland.

Glaciers in Iceland have been retreating since 1890 and climate change simulations predict that the majority may disappear within a few hundred years. Retreating ice caps cause glacial isostatic adjustment (GIA) as well as changes to the subsurface stress field. Glacier covered volcanic systems are most affected, but also crustal conditions outside glaciers as well as magma generation at depth. Eruption likelihood may be modified, as occurred during the Pleistocene deglaciation, as more melt accumulates under Iceland because of ice retreat. However, there are several uncertainties: i) if, how and when this new magma reaches the surface; ii) if stability of existing magma bodies is modified; iii) if deglaciation is already resulting in accumulation of larger volumes of melt within crustal reservoirs; iv) how induced variations in the stress field may affect future volcanic activity. ISVOLC is focussing on four active volcanoes in Iceland (Katla, Askja, Grímsvötn and Bárðarbunga), to address these research questions.

Katla volcano lies beneath Mýrdalsjökull ice cap in S-Iceland. It is capable of generating large explosive eruptions within its caldera, with ash plume heights between 14-20 km accompanied by major jökulhlaups. GNSS observations from stations on nunataks of the glacier, and the surrounding region, combined with seismicity and changes to ice-cauldrons suggests a combination of processes are occurring, including GIA and magma inflow.

At Askja volcano, inflation commenced at end of July 2021 after decades of subsidence. This was detected on both GNSS observations and Sentinel-1 interferograms. Geodetic modelling indicates the onset of unrest was triggered by migration of magma within the uppermost part of the volcano plumbing system, followed by influx of new melt from depth. At the time of writing (January 2024) inflation continues but at a lower rate.

In the Bárðarbunga volcanic system, the six-month long 2014-2015 Holuhraun eruption was accompanied by gradual caldera collapse of up to 65 m and preceded by a two-week period of 48 km long lateral dyke propagation with extensive seismicity and deformation. Geodetic observations show that re-inflation started in July 2015, immediately after the end of the eruption. This may be explained by a combination of renewed magma inflow and viscoelastic readjustment of the volcano. GNSS and seismic observations show an increase in rate of inflation and seismicity since early 2023.

Grímsvötn subglacial volcano is the most frequently erupting volcano in Iceland, with eruptions in 1998, 2004 and 2011. A GNSS station shows a prominent inflation cycle between eruptions. Deformation at this volcano has surpassed that observed prior to recent eruptions and its aviation color code was elevated to yellow in January 2024 due to a short-lived intense seismic swarm.

How to cite: Parks, M. and the ISVOLC Team: An update of recent geodetic observations and modelling results at key Icelandic volcanoes within the ISVOLC project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19525, https://doi.org/10.5194/egusphere-egu24-19525, 2024.

EGU24-19530 | Orals | GMPV8.6

La Palma (Canary Islands) eruption 2021: Forecast and hindcast of eruption duration 

Maria Charco, Pablo J. González, José L.G. Pallero, Laura García-Cañada, and Carmen Del Fresno

After 50 years of quiescence, the most voluminous eruption since historical records started at La Palma took place (September 19 – December 13, 2021, 85 days and 9 hours of duration). The observed deformation field during the eruption was consistent with a deflating reservoir located at Moho depth beneath Cumbre Vieja volcano. This reservoir has been previously studied and determined that magmas can stagnant and reside there over a wide range of time-scales varying from days-weeks to a few centuries. 

During the eruption, applying some basic principles we made a forecast of the eruption duration. Under the assumption of mass conservation in a close-system, the pressure drop, responsible for the observed deflation signal, controls eruption duration. On day 38th of the eruption and despite its simplicity, one of our models with a pressure drop equal to 1% of the initial reservoir overpressure provided an estimated duration of 86 ± 7 days. Therefore, less than halfway along the actual duration of the La Palma eruption, the proposed model was able to estimate a possible tight duration. This duration was consistent with historical records of eruption durations in La Palma ranging from 24 to 84 days. The lack of a priori bounds on the pressure drop necessary to cease the eruption made the forecast too uncertain to have operational impact. In hindsight, we empirically show that the pressure drop in the reservoir was actually limited by mass conservation. We conclude that the magma dynamics of the Moho reservoir was the dominant control on the eruptive volume evolution. This study demonstrates that near real-time forecasts of eruption durations will be possible in future similar eruptions at La Palma. Our study opens the possibility to explore the applicability of this method to other volcanoes.

How to cite: Charco, M., González, P. J., Pallero, J. L. G., García-Cañada, L., and Del Fresno, C.: La Palma (Canary Islands) eruption 2021: Forecast and hindcast of eruption duration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19530, https://doi.org/10.5194/egusphere-egu24-19530, 2024.

EGU24-19589 | Orals | GMPV8.6

Anomaly detection within the 2021-2023 deformation pattern of the Campi Flegrei (Italy) caldera through the analysis of DInSAR and GNSS data 

Flora Giudicepietro, Manuela Bonano, Claudio De Luca, Prospero De Martino, Federico Di Traglia, Mauro Antonio Di Vito, Riccardo Lanari, Giovanni Macedonio, Michele Manunta, Fernando Monterroso, Pasquale Striano, and Francesco Casu

The Campi Flegrei caldera (southern Italy) is an active volcano whose last eruption occurred in 1538. This caldera is characterized by ground displacements (subsidence or uplift), often referred to with the term "bradyseism". Over the last two decades the Campi Flegrei caldera was affected by a phase of uplift which became progressively more intense over time and was accompanied by increasing seismicity and geochemical anomalies. The Campi Flegrei deformation pattern generally shows a bell-like shape, with the zone of maximum uplift in the central area corresponding to Rione Terra, that is the historic district of Pozzuoli. In the 2021-2023 period the OV-INGV seismic network detected significant seismicity and the GNSS and DInSAR measurements highlighted a high uplift rate of the central area of the Caldera. In this period, seismicity was distinctly felt by the population several times (maximum magnitude Md = 4.2) and the uplift of the central sector of the caldera reached a level that made it difficult to enter the ancient fishermen's port of Pozzuoli (about 120 cm compared to the ground level in 2005). We have carried out a detailed analysis of the ground deformations relevant to the 2021-2023 time interval. Our study has highlighted a local anomaly of the caldera deformation pattern in the Solfatara-Pisciarelli-Olibano hydrothermal area. This anomaly became well recognizable in 2022 and it further developed during 2023. Moreover, it affects the area in which the earthquakes with greater magnitude occurred in the Campi Flegrei. We interpret this zone as a possible weakness area in the crustal structure of the Caldera and, therefore, we believe that a detailed monitoring of this zone is foreseen because it may provide some relevant insights on the caldera dynamics and the related hazard.

How to cite: Giudicepietro, F., Bonano, M., De Luca, C., De Martino, P., Di Traglia, F., Di Vito, M. A., Lanari, R., Macedonio, G., Manunta, M., Monterroso, F., Striano, P., and Casu, F.: Anomaly detection within the 2021-2023 deformation pattern of the Campi Flegrei (Italy) caldera through the analysis of DInSAR and GNSS data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19589, https://doi.org/10.5194/egusphere-egu24-19589, 2024.

EGU24-19913 | Orals | GMPV8.6

Changes in seismicity and observed deformation related to inflation at the Theistareykir high-temperature geothermal field, NE Iceland, in 2023-2024 

Egill Árni Gudnason, Vincent Drouin, Yilin Yang, Freysteinn Sigmundsson, Thorbjörg Ágústsdóttir, and Anette K. Mortensen

Theistareykir is one of five active volcanic systems of the Northern Volcanic Zone, NE Iceland, along with Krafla, Fremrinámar, Askja and Kverkfjöll, from north to south, respectively. The Theistareykir volcanic system includes a N-S trending rifting fissure swarm, approximately 70-80 km long and 7-8 km wide, extending through it. There are neither postglacial eruptive fissures nor a clear caldera formation at Theistareykir, with the latest eruption occurring ~2,400 years ago.

Theistareykir comprises a high-temperature geothermal system which has been systematically explored over the past 50 years, with around 20 exploration and production wells drilled to date. Since 2017, geothermal energy has been utilised at Theistareykir with a 90 MWe power station currently operated by Landsvirkjun, the National Power Company of Iceland. Extensive monitoring of the geothermal field is carried out through e.g., various geophysical measurements.

An inflation was observed to start at Theistareykir at the beginning of 2023, with the centre of uplift approximately 2.5 km west of the Theistareykir power plant. Earthquake activity in Theistareykir occurs in more or less three separated clusters, and coinciding with the start of inflation, an increase in seismicity rate was observed within the northernmost cluster, with the largest earthquake reaching ML 2.2 at 5.2 km depth. Earthquake depths within this cluster range between ~5-7 km, deepening towards north. No significant change is observed in faulting mechanisms within this cluster, despite the inflation, with oblique strike-slip events most common.

The vertical component of the continuous Global Navigation Satellite System (GNSS) station in Theistareykir (THRC), located ~0.5 km northeast of the uplift centre, indicates a best-fit onset time of the inflation around 9 February 2023, and an initial uplift of 21.5 mm/yr.

Synthetic Aperture Radar Interferometry (InSAR) of Sentinel-1 images was used to measure the inflation. The anomaly is ~10 km wide and the uplift in its centre is ~12-15 mm between the summers of 2022 and 2023. Knowing that the uplift started around the beginning of 2023, the actual uplift rate is therefore ~20-25 mm/yr at the uplift centre. This is similar to the two previous inflation episodes observed in the area in 1995-1996 and 2006-2009.

Geodetic modelling, using the InSAR data, indicates that a model with a point source pressure within a uniform elastic halfspace can explain the observations. The inferred source has a centre depth in the range of 4.4-6.2 km (95% confidence interval), and a volume change of (1.1-2.5) x 106 m3 (95% confidence interval) until the end of summer 2023.

Our aim is to understand better the activity and identify the driving processes, and their implications for the geothermal field. Results will be presented in the context of past earthquake and deformation data.

How to cite: Gudnason, E. Á., Drouin, V., Yang, Y., Sigmundsson, F., Ágústsdóttir, T., and Mortensen, A. K.: Changes in seismicity and observed deformation related to inflation at the Theistareykir high-temperature geothermal field, NE Iceland, in 2023-2024, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19913, https://doi.org/10.5194/egusphere-egu24-19913, 2024.

EGU24-20338 | Orals | GMPV8.6

Faulting activity during the 2021 oblique rifting event in the Reykjanes Peninsula (SW Iceland) 

Joël Ruch, Simon Bufferal, Elisabetta Panza, Stefano Mannini, Adriano Nobile, Birgir Óskarsson, Nils Gies, and Ásta Rut Hjartardóttir

The Reykjanes Peninsula is located at the boundary between the North American and the Eurasian plates. The Peninsula is experiencing an oblique rifting episode that started with a strong earthquake swarm the 24 February 2021, preceded by sparse swarm occurrences in the decade before. This activity has been followed by a volcanic eruption the 19 March 2021 and by three other eruptions in 2022 and 2023 after ~800 years of quiescence in this region. These series of events offer a unique opportunity to explore the relation between tectonic, faulting and volcanic activity in a highly oblique rift zone.

 

Here we focus on faulting activity during the onset period of the ongoing rifting episode, from February to March 2021. We use an extensive dataset of field observations and high resolution drone orthomosaics and DEMs over a ~30 km2 area to map, quantify and characterize the widespread ground fracturing associated with the oblique rifting activity. We mapped ~20’000 ground cracks of metric to decametric length, centimetric extensional offset, and clear dextral shear component, well-correlated to major earthquakes. Most fractures show en-échelons structures globally aligned along NS-striking fault zones up to 3-4 km long. By analyzing the timing of the ground fracturing thanks to our repeated field observations, seismic data and InSAR images, we relate most ground fractures to earthquakes of Mw ≥ 5.0 that occurred in the month preceding the March 2021 Fagradalsfjall eruption. Using optical image correlation from drone data and air photos, we further characterize in unprecedented details several NS fault zones that were reactivated up to three times during the event and were already existing before.

 

Our results show dominant strike-slip features, atypical in rift zones, that highlight the geometry of a bookshelf-mode activity along a diffuse and highly oblique plate boundary. These findings further question the relation between tectonic and magmatic activity at mid-oceanic ridges. Thanks to our immediate on-site response in early March 2021, we witnessed extensive ground fractures that have been quickly lost within a year due to erosion or recovered by lava flows, pointing out a potential under-representation of diffuse fracturing when studying oblique volcanic systems.

How to cite: Ruch, J., Bufferal, S., Panza, E., Mannini, S., Nobile, A., Óskarsson, B., Gies, N., and Hjartardóttir, Á. R.: Faulting activity during the 2021 oblique rifting event in the Reykjanes Peninsula (SW Iceland), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20338, https://doi.org/10.5194/egusphere-egu24-20338, 2024.

EGU24-20339 | ECS | Posters on site | GMPV8.6

Monitoring the surface deformation of an active volcano during a new unrest phase (Askja caldera, central Iceland) 

Nicolas Oestreicher, Joël Ruch, Þorsteinn Sæmundsson, Jón Kristinn Helgason, Nicolas Serrano Vega, Xingjun Luo, Patricia Leva, Jasmin Maissen, Michael Hohl, Jordan Aaron, Andrea Manconi, Halldór Geirsson, Daniel Mc Ginnis, Elisabetta Panza, Yohann Chatelain, and Frédéric Arlaud

In the summer of 2021, Askja caldera entered a renewed period of unrest, which was marked by a significant uplift of the caldera floor (over 70 cm in 2.5 y) and a slight increase in background seismicity. These indicators suggest the presence of magma rising from depth, potentially heralding an eruption in the months or years ahead. The renewed activity has increased the risk of landslides, particularly along the already unstable slopes of the eastern Öskjuvatn caldera. A major landslide in 2014 triggered a tsunami in the adjacent lake that inundated the lakeshore, reaching several tens of meters above its pre-event surface. To gain a deeper understanding of the unresting phase and its associated hazards that may lead to an eruption, the installation of a comprehensive monitoring system is key.

In the summer of 2023, a dense monitoring network was established to address these shortcomings. Three time-lapse cameras were installed to track ground movement along the unstable eastern caldera rim. Three corner reflectors were deployed to capture InSAR data, even during the snow-covered winters. A continuous GNSS instrument was also installed to monitor ground displacement continuously. We also covered the entire Öskjuvatn caldera rim with several drone surveys, in 2020, 2021 and 2023, obtaining high-resolution DEMs and orthomosaics to study ground deformation in the past few years.

However, arctic conditions prevail during winter months at Askja caldera. Extensive wind-sculpted ice structures have formed on the stations and prevent using the corner reflectors and time-lapse cameras at their full capacity. Storm- to hurricane-force winds have damaged highly exposed stations on the shoulders of the caldera ring faults. We propose technical improvements for extreme conditions and show preliminary results of our monitoring system. In particular, we show a detailed structural map based on our drone data and extensive field observations, thousands of fractures and other geological features providing a kinematic analysis for different parts of the caldera ring faults cliffs.

This collaborative effort between Swiss and Icelandic institutions has established an unprecedented monitoring system for an unresting volcano susceptible to eruptions and landslides. The multi-tools approach offers valuable insights into the behaviour of such calderas and could serve as a model for similar monitoring efforts worldwide.

How to cite: Oestreicher, N., Ruch, J., Sæmundsson, Þ., Helgason, J. K., Serrano Vega, N., Luo, X., Leva, P., Maissen, J., Hohl, M., Aaron, J., Manconi, A., Geirsson, H., Mc Ginnis, D., Panza, E., Chatelain, Y., and Arlaud, F.: Monitoring the surface deformation of an active volcano during a new unrest phase (Askja caldera, central Iceland), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20339, https://doi.org/10.5194/egusphere-egu24-20339, 2024.

Alkaline mafic magmas forming intra-plate oceanic islands are believed to be strongly enriched in CO2 due to low-degree partial melting of enriched mantle sources. However, until now, such CO2 enhancement has not been verified by measuring CO2 degassing during a subaerial eruption. Here, we provide evidence of highly CO2-rich gas emissions during the 86-day 2021 Tajogaite eruption of Cumbre Vieja volcano on La Palma Island, in the Canary archipelago. Our results reveal sustained high plume CO2/SO2 ratios, which, when combined with SO2 fluxes, melt inclusion volatile contents and magma production rates at explosive and effusive vents, imply a magmatic CO2 content of 4.5 ± 1.5 wt%. The amount of CO2 released during the 2021 eruptive activity was 28 ± 14 Mt CO2. Extrapolating to the volume of alkaline mafic magmas forming La Palma alone (estimated as 4000 km3 erupted over 10 Ma), we infer a maximum CO2 emission into the ocean and atmosphere of 1016 moles of CO2, equivalent to 20% of the eruptive CO2 emissions from a large igneous province eruption, suggesting that the formation of the Canary volcanic archipelago produced a CO2 emission of similar magnitude as a large igneous province.

How to cite: Burton, M. and the Tajogaite 2021 Gas Team: Exceptional eruptive CO2 emissions from intra-plate alkaline magmatism in the Canary volcanic archipelago, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5990, https://doi.org/10.5194/egusphere-egu24-5990, 2024.

EGU24-7479 | Posters on site | GMPV8.7

Nyiragongo eruption 2021 and its environmental impact: volcanic ash fallout and high levels of trace metals in drinking water 

Sergio Calabrese, Patrick Habakaramo Macumu, Sergio Bellomo, Nicole Bobrowski, Guillaume Boudoire, Filippo Brugnone, Giavanni Bruno Giuffrida, Lorenzo Brusca, Walter D'Alessandro, Mathieu Gouhier, Simone Lentini, Lorenza Li Vigni, Luciana Randazzo, and Dario Tedesco

Nyiragongo (D.R. Congo) is an active volcano known for its impressive persistent lava lake within its crater, and it is recognized as one of the most dangerous volcanoes in the world because more than two million people live on its slopes. Suddenly, on 22 May 2021, Nyiragongo produced three different lateral lava flows from the southern lower flanks, and significant amounts of volcanic gas and ash were emitted from the summit crater following the collapse of the crater floor. For a few weeks, the ash fallout impacted the main city of Goma and the numerous villages located in the vicinity of the volcano. 22 samples of volcanic ashes and 135 samples of drinking water (springs, rivers, rainwater, roof runoff) were collected before, during and after the eruption. From the leaching of the ashes and their direct observation through a field emission scanning electron microscope (FE-SEM), large quantities of soluble salts (e.g. sulphates, chlorides) on their surface were identified. The results showed that most of the drinking waters collected in the downwind villages (like Rusayo, Kingi, Sake) were heavily contaminated by volcanic emissions. In fact, fluoride, chloride, sulphur, and many potentially toxic elements (PTEs), including Al, As, Cd, Cr, Cu, Fe, Mn, Mo, Pb, Sb, Se, Te, Tl, and V, exceeded the suggested World Health Organization (WHO) drinking water limits during the eruptive period, exposing the population living in villages downwind of the preferential direction of the volcanic plume, to high health risks.

How to cite: Calabrese, S., Habakaramo Macumu, P., Bellomo, S., Bobrowski, N., Boudoire, G., Brugnone, F., Giuffrida, G. B., Brusca, L., D'Alessandro, W., Gouhier, M., Lentini, S., Li Vigni, L., Randazzo, L., and Tedesco, D.: Nyiragongo eruption 2021 and its environmental impact: volcanic ash fallout and high levels of trace metals in drinking water, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7479, https://doi.org/10.5194/egusphere-egu24-7479, 2024.

EGU24-7544 | ECS | Orals | GMPV8.7

Post-eruptive emission of metals and metalloids from basaltic lavas 

Nicolas Levillayer, Olgeir Sigmarsson, and Céline Mandon

During basaltic eruptions, degassing occurs both syn- and post-eruptively. The atmospheric loading resulting from the latter, taking place as the lava cools down and solidifies, is poorly characterised and its environmental impacts are largely unknown. Characterising post-eruptive degassing can be attempted either by direct sampling of the gas emitted at solidifying lava flow or by analysing the degassing structure (segregation veins and vesicles) from already crystallised lava bodies. The 2021-2023 eruptions at Fagradalsfjall on the Reykjanes Peninsula, Iceland, allowed sampling of both the syn- and post-eruptive gas phases. Segregation veins from prehistorical olivine tholeiite lavas of similar composition to that of Fagradalsfjall have been collected, together with their host lava. Major and trace volatile element concentrations, particularly those of the toxic volatile metals and metalloids (VMM), were analysed in the gas and rock phases. The gas analyses reveal distinct VMM composition of the gas emitted syn- and post-eruptively, with a clear tendency for Zn, Mo and Sb to degas after the eruption, whereas Te, Cd and Bi are predominantly released syn-eruptively. Among the segregation veins sampled, several showed anomalous enrichment in numerous VMM, indicative of the post-eruptive gas phase composition. Molybdenum is largely enriched in these veins whereas Cd enrichment is low, reflecting gas phase rich in the former but poor in the latter. Taken together, both approaches indicate substantial atmospheric loading of As, Pb, Sb and Mo post-eruptively resulting in potential hazard around newly erupted lava bodies.

How to cite: Levillayer, N., Sigmarsson, O., and Mandon, C.: Post-eruptive emission of metals and metalloids from basaltic lavas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7544, https://doi.org/10.5194/egusphere-egu24-7544, 2024.

The Laacher See volcano is one of the youngest volcanoes in Germany with its last eruption 13,006 ±9 years BP(1). About 6.3 km³ of hydrous phonolitic magma was explosively erupted by phreatomagmatic and plinian eruptions in less than 10 days(2). The eruption behavior of such volcanic systems is determined by the phase separation mechanism of H2O fluid from the supersaturated hydrous silicate melt during ascent. The number of fluid vesicles per unit volume of silicate melt (VND in mm-3) is a standard parameter used to quantify the efficiency of fluid-melt separation and thus the acceleration of magma ascent. According to the nucleation theory, the VND increases strongly with decompression rate(3) and is thus a suitable parameter for quantifying magma ascent velocity. Recently and specifically for phonolitic melts, the process of spinodal decomposition has been proposed, which manifests in the independence of VND from the decompression rate(4).

            To characterize the degassing behavior of the lower Laacher See phonolite, systematic decompression experiments were conducted in the internally heated pressure vessel. The melts were hydrated with 5.7 or 5.0 wt% H2O at 200 MPa and 1523 K for 96 h and then continuously decompressed at 1323 K with 0.064 – 1.7 MPa/s to final pressures between 110 MPa and 30 MPa. By reaching the final pressure, the samples were rapidly quenched to room temperature to preserve the vesicle textures and the residual H2O contents in the melts and to minimize vesicle shrinkage during cooling. The VNDs and the spatial distribution of the vesicles, as well as the H2O contents in the decompressed melts were analyzed with quantitative image analysis, transmission light microscopy, and FTIR-spectroscopy.

            Upon reaching sufficient supersaturation pressure of >80 MPa, all samples exhibit homogeneously dispersed and micrometer-sized vesicles in the sample center (Fig. 1). The results consistently show that the initial VND is independent of the decompression rate, with high logVNDs of 4.1 to 5.6 causing very fast near equilibrium adjustment of H2O concentration of the melt by degassing. Further decompression of the vesiculated melts leads to vesicle coalescence, resulting in a significant reduction of VND by orders of magnitude.

            These observations are consistent with that of Allabar and Nowak (2018), who determined a decompression rate independent logVND of ~5.2 ±0.5 for hydrous phonolitic melt of the AD79 Vesuvius white pumice composition. From this, a trend emerges that at least for hydrated phonolitic melts, spinodal decomposition plays a crucial role in the H2O degassing behavior of the melt and thus in the explosive eruption behavior of the volcanic systems.

 

 

(1)Allabar A., Nowak M. (2018) Message in a bottle: Spontaneous phase separation of hydrous Vesuvius melt even at low decompression rates. EPSL, 501, 192-201.

(2)Reinig F., et al. (2021) Precise date for the Laacher See eruption synchronizes the Younger Dryas. Nature, 595, 66-69.

(3)Toramaru A. (2006) BND (bubble number density) decompression rate meter for explosive volcanic eruptions. J. Volcanol. Geotherm. Res., 154, 303-316.

(4)Wörner G., Schmincke H.-U. (1984) Petrogenesis of the Zoned Laacher See Tephra. J. Petrol., 25, 805-835.

How to cite: Marks, P. L. and Nowak, M.: Decoding the H2O phase separation mechanism as the trigger for the explosive eruption of the Lower Laacher See phonolite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7723, https://doi.org/10.5194/egusphere-egu24-7723, 2024.

EGU24-9803 | Orals | GMPV8.7

Inverting thermal imagery of fumarole plumes to reveal gas fluxes 

David Jessop and Amelie Klein

The mass and heat fluxes emitted by fumarole vents form a large portion of the total degassing budgets at volcanoes undergoing unrest, particularly at hydrothermal volcanoes. For example, the fumarole fluxes at la Soufrière represent around 78% of the total heat budget (Jessop et al., 2021). Pitot-tube instruments provide perhaps the most reliable data for fumarole fluxes but require the user to directly contact the hot, acidic, and toxic gases. Flux estimations from MultiGAS traverses still require the user to be in contact with fumarole gases but at a distance from the vent where the plume is much cooler. The errors associated with this method are substantial (c. 40%).

Physically, fumarole plumes are similar to volcanic plumes produced by explosive activity in the absence of particles and hence similar models can be used (e.g. Woitischek et al., 2021). In this work, we propose using a wind-bent plume model (e.g. Woodhouse et al., 2013; Aubry et al., 2017) to match thermal images of the fumarole plume. Fumarole plumes typically are not opaque (see image) and so we develop a radiative model to account for this (cf. Cerminara et al., 2015). Our model requires the mass and heat flow rates to be specified at the vent. These parameters are retried by inverting our model with data extracted from thermal images acquired between 2017–2023 using a ground-based camera at the level of the vent. We find a slow but steady increase in vent flux over the period of study which is in keeping with data from MultiGAS and Pitot-tube measurements during the same period. The errors associated with our method are much lower than those of the MultiGAS traverse method and will allow for finer analyses of fumarole degassing data and its implications for understanding volcanic unrest.

Aubry, T. J. et al. (2017). “Turbulent entrainment into volcanic plumes: new constraints from laboratory experiments on buoyant jets rising in a stratified crossflow”. Geophys. Res. Lett. 44.20, pp. 10198–10207. DOI: 10.1002/2017GL075069.

Jessop, D. E. et al. (2021). “A multi-decadal view of the heat and mass budget of a volcano in unrest: La Soufrière de Guadeloupe (French West Indies)”. Bull. Volcanol. 3, p. 16. DOI: 10.1007/s00445-021-01439-2.

Cerminara, M. et al. (2015). “Volcanic plume vent conditions retrieved from infrared images: a forward and inverse modeling approach”. J. Volcanol. Geoth. Res. 300, pp. 129–147. DOI: 10.1016/j.jvolgeores.2014.12.015.

Woitischek, J. et al. (2021). “On the use of plume models to estimate the flux in volcanic gas plumes”. Nat. Commun. 12.1, p. 2719. DOI: 10.1038/s41467-021-22159-3.

Woodhouse, M. J. et al. (2013). “Interaction between volcanic plumes and wind during the 2010 Eyjafjallajokülleruption, Iceland”. J. Geophys. Res.-Solid Earth 118.1, pp. 92–109. DOI: 10.1029/2012JB009592.

 

How to cite: Jessop, D. and Klein, A.: Inverting thermal imagery of fumarole plumes to reveal gas fluxes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9803, https://doi.org/10.5194/egusphere-egu24-9803, 2024.

Volatile components, especially water and carbon dioxide, play a controlling role on practically any process and any property related to magmas and their dynamics, influencing to a first order volcanic eruptions and their related hazards. Consequently, knowing the partitioning of water and carbon dioxide among silicate melts and coexisting gas phases is one major objective in a variety of disciplines such as petrology, rock and fluid geochemistry, and magma and volcano physics and dynamics. Here I present the most updated, most comprehensive model of water and carbon dioxide solubility and saturation in silicate melts of virtually any composition spanning from two-component metal slags to natural magmas from the most iron and magnesium –rich, silica under-saturated, to the most chemically evolved ones found on Earth, the Moon, or Mars. The model rests on rigorous thermodynamic modelling, and on a robust calibration involving nearly 2000 individual saturation data – the entire set of appropriate existing data to my knowledge. Pressure and temperature of calibration also span wide ranges from one bar to several GPa, and from just above liquidus to above 2000 °C, respectively. I show here the capability of the model to properly account for virtually any aspect previously described from the experiments and related to the compositional-dependent water and carbon dioxide saturation surface in silicate melts; its capability to extend further that knowledge by revealing additional aspects not yet experimentally highlighted; and some examples of the use of the model to explore the characteristics of real magmatic systems and simulate their dynamics.

How to cite: Papale, P.: The P-T-X dependent water and carbon dioxide saturation in silicate melts of virtually any composition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9892, https://doi.org/10.5194/egusphere-egu24-9892, 2024.

EGU24-9973 | ECS | Orals | GMPV8.7

A novel model of volcanic plume evolution from high-temperature chemistry to reactive plume chemistry in the atmosphere 

Alexander Nies, Tjarda Roberts, Guillaume Dayma, Tobias Fischer, and Jonas Kuhn

The first seconds of the interaction of volcanic gases with the atmosphere have so far often been drastically simplified, e.g., by assuming thermochemical equilibrium. In this period, hot and reduced magmatic gases mix with ambient air and undergo rapid cooling. The in-mixture of atmospheric oxygen triggers fast oxidation processes which depend on the dynamic interplay of chemical kinetics, mixing and cooling.

We present a novel chemical box model, which can capture rapid chemical kinetics alongside cooling and mixing of the early plume. The model combines a chemical combustion mechanism with atmospheric chemistry mechanisms and includes sub-mechanisms for halogens, sulfur, reactive nitrogen and mercury, respectively. It is fast and flexible to test many different emission temperatures, mixing scenarios, eruption styles, and gas compositions.

Here, we focus on the formation of reactive halogen species (e.g. bromine oxide (BrO), bromine chloride (BrCl), hypobromous acid (HOBr), and atomic bromine (Br)) during the first seconds, minute to hours of plume evolution, which significantly influence atmospheric chemistry on a regional scale. We study the impact of the high-temperature initializations on ambient-temperature plume chemistry to capture for example the catalytic destruction of ozone by bromine chemistry in the cooled plume. The simulations show that up to 40% of the emitted bromine can be converted into reactive forms within seconds. It promotes fast formation of BrO in the early evolution of the volcanic plume, at magnitudes consistent with UV-remote sensing measurements.

We further assess the presence of reduced species (e.g. molecular hydrogen (H2) and carbon monoxide (CO)) in the cooled plume and potential implications for the interpretation of observations of redox pairs in the plume. Our kinetic model contrasts to previous thermochemical equilibrium assumptions of near-complete oxidation of H2 and CO. We identify emission temperatures and plume cooling conditions that allow these reduced species to persist whilst reactive bromine is formed, as well as conditions where the reduced species become oxidized.

The combustion-atmospheric model is a unique tool for analyzing volcanic plume composition measurements as it provides the link to the original composition of the magmatic gas by a kinetic treatment of the magma-atmosphere interface. Future applications include the study of aerosol formation by SO2-sulfate transformation, mercury and NOx-nitrate chemistry.   

How to cite: Nies, A., Roberts, T., Dayma, G., Fischer, T., and Kuhn, J.: A novel model of volcanic plume evolution from high-temperature chemistry to reactive plume chemistry in the atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9973, https://doi.org/10.5194/egusphere-egu24-9973, 2024.

EGU24-13196 | Posters on site | GMPV8.7

Diffuse CO2 degassing monitoring of the Tenerife North-South Rift Zone (NSRZ) volcano, Canary Islands 

Héctor de los Ríos, Léa Ostorero, Gladys V. Melián, Fátima Rodríguez, María Asensio-Ramos, Nemesio M. Pérez, Pedro A. Hernández, Eleazar Padrón, and Germán D. Padilla

Tenerife (2,034 km2), the largest and one of the most active islands of the Canarian volcanic archipelago, has registered six volcanic eruptions in the last 500 years. One of the main volcano-structural and geomorphological features of Tenerife is the triple junction-shaped rift system, as a result of inflation produced by the concentration of emission vents and dykes at 120º one to another. The oriented North South Rift Zone (NSRZ; 325 km2) is one of the three active volcanic rift-zones of the island and is characterized mainly by effusive activity of basaltic lavas forming spatter and cinder cones and comprising 139 monogenetic cones representing the most common eruptive activity occurred on the island during the last 1My. The main structural characteristic of the NSRZ is the apparent absence of a distinct ridge and a fan shaped distribution of these monogenetic cones. Since no visible degassing at Tenerife NSRZ surface occurs, a geochemical monitoring program at Tenerife NSRZ was established mainly consisting on performing diffuse CO2 emission surveys to evaluate the temporal and spatial variations of soil CO2 efflux values and the diffuse CO2 emission rate. Ten diffuse CO2 degassing surveys have been carried out at NSRZ of Tenerife since 2002, the last one in the summer period of 2023. Measurements of soil CO2 efflux were performed in situ by means of a portable non-dispersive infrared sensor following the accumulation chamber method at about selected 600 sampling sites to obtain a homogeneous distribution after taking into consideration the local geology, structure and accessibility. During the 2023 survey, soil CO2 efflux values ranged from non-detectable up to 55.5 g m−2 d−1. Statistical-graphical analysis of the 2023 data show three different geochemical populations; background (B), intermediate (I) and peak (P) represented by 93.9%, 5.4% and 0.7% of the total data, respectively. The geometric means of the B, I and P populations are 1.6, 11.4 and 36.6 g m−2 d−1, respectively. Most of the area showed B values while the P values were observed as multiple isolated anomalies in the study area. 100 equiprobable sequential Gaussian simulations were performed to construct the spatial interpolation map and to estimate the diffuse CO2 emission in tons per day released from Tenerife NSRZ in the 2023 survey. The diffuse CO2 output released to atmosphere by the NSRZ of Tenerife estimated in the 2023 survey was 884 ± 27 t d-1. This value overcomes the estimated background range (201 - 760 t d-1), and confirms the clear relationship  between the temporal evolution of the CO2 output released by the NSRZ and the seismic activity in and around Tenerife island. These geochemical observations are clear evidence of changes of processes operating deep in the hydrothermal-magmatic system of Tenerife. Monitoring the diffuse CO2 emission contributes to detect early warning signals in the activity of the Tenerife North-South Rift-Zone volcanic system.

How to cite: de los Ríos, H., Ostorero, L., Melián, G. V., Rodríguez, F., Asensio-Ramos, M., Pérez, N. M., Hernández, P. A., Padrón, E., and Padilla, G. D.: Diffuse CO2 degassing monitoring of the Tenerife North-South Rift Zone (NSRZ) volcano, Canary Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13196, https://doi.org/10.5194/egusphere-egu24-13196, 2024.

EGU24-15632 | Orals | GMPV8.7

Tracing Volcanic Degassing Dynamics During the 2021-2023 Eruptions on the Reykjanes Peninsula, Iceland, via OP-FTIR measurements 

Samuel Scott, Melissa Pfeffer, Clive Oppenheimer, and Andri Stefánsson

The recent eruptions on the Reykjanes Peninsula presented an exceptional opportunity for in-depth analyses of volcanic gas emissions. Utilizing Open-path Fourier Transform Infrared (OP-FTIR) spectroscopy, we analyzed the abundance of major and minor gas molecular species, including H2O, CO2, SO2, HCl, HF and CO, in the gas emissions on more than twenty occasions throughout the eruptions in 2021-2023. Predominantly water-rich emissions (60-95 mol % H2O) suggest fractional degassing and substantial CO2 loss at depth. Significant temporal variations in gas composition were observed, with lower H2O/CO2 and H2O/SO2 ratios and higher SO2/HCl ratios measured early in the early stages of the Fagradalsfjall eruption and higher H2O/CO2 and H2O/SO2 ratios and lower SO2/HCl ratios during later stages and subsequent eruptions. A unique set of measurements, conducted at close range and high temporal resolution during the 2021 lava fountaining phase, provided insights into the dynamics of gas segregation at shallow depths. These findings help explain the pulsatory nature of the lava fountaining, driven by pressure fluctuations in a shallow magma-filled cavity. Furthermore, the gas emission chemistry varied significantly with the degassing style, with gas emitted by surface lava flows characterized by higher H2O/CO2 and H2O/SO2 and lower SO2/HCl and SO2/HF ratios compared to gas emitted at actively erupting vents. This study underscores the effectives of OP-FTIR techniques for tracking the spatiotemporal evolution of basaltic magma degassing, offering valuable insights into volcanic processes.

How to cite: Scott, S., Pfeffer, M., Oppenheimer, C., and Stefánsson, A.: Tracing Volcanic Degassing Dynamics During the 2021-2023 Eruptions on the Reykjanes Peninsula, Iceland, via OP-FTIR measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15632, https://doi.org/10.5194/egusphere-egu24-15632, 2024.

EGU24-15859 | Posters on site | GMPV8.7

Impact of the hydrothermal activity on the seawater chemistry above the Kolumbo volcano (southern Aegean Sea - Greece) 

Manfredi Longo, Walter D'Alessandro, Fausto Grassa, Lars Eric Heimbürger-Boavida, Gianluca Lazzaro, Sergio Simone Scirè Scappuzzo, Paraskevi Nomikou, Paraskevi Polymenakou, and Andrea Luca Rizzo

Within the framework of SANTORY (SANTORini’s seafloor volcanic observatorY) project, funded by the Hellenic Foundation for Research and Innovation and with the financial support of the Municipality of Thira, three oceanographic cruises were performed in December 2022 and June and October 2023, with the research vessels PHILIA and AEGAEO of the HCMR at the submarine volcano Kolumbo, 7 km NE of Santorini. Kolumbo is considered to be one of the most active submarine volcanic complexes in the Eastern Mediterranean Sea, while being easily accessible from land.. The oceanographic surveys were mainly aimed at the deployment of a new generation observatory along with several multiple innovative sensors such as temperature sensors, inclinometers, pressure gauges, optical cameras, multispectral and stereo camera, radioactivity sensor gSniffer and the γ-radiation imager. During the surveys, several water column profiles were also performed in order to collect seawater samples for chemical analysis. At the bottom of the Kolumbo crater (500m depth), acidic and slightly reducing conditions prevail, due to the presence of several active hydrothermal vents. This agrees with previous studies and with the data recorded by the deployed observatory. Collected samples have been analyzed for the chemical and isotope (carbon, helium and argon) composition of the dissolved gases as well as for the major, minor and trace element concentrations. The results indicate that the morphology of the crater allows the buildup of persistent anomalies that extend from the bottom up to the lowest crater-rim level at about 250-meter depth. We will discuss the temporal variability of the Kolumbo venting dynamics and the explore in detail the resulting vertical gradients in the crater funnel.

How to cite: Longo, M., D'Alessandro, W., Grassa, F., Heimbürger-Boavida, L. E., Lazzaro, G., Scirè Scappuzzo, S. S., Nomikou, P., Polymenakou, P., and Rizzo, A. L.: Impact of the hydrothermal activity on the seawater chemistry above the Kolumbo volcano (southern Aegean Sea - Greece), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15859, https://doi.org/10.5194/egusphere-egu24-15859, 2024.

EGU24-15866 | ECS | Orals | GMPV8.7

Monitoring of rainwater chemistry during the recent volcanic unrest at Vulcano Island (Italy) 

Francesco Tripodi, Filippo Brugnone, Walter D'Alessandro, Sergio Bellomo, Lorenzo Brusca, Antonio Paonita, and Sergio Calabrese

Volcanoes are an important source of gas and particles into the atmosphere, during the eruptive periods or even during passive degassing activity. The study of volcanic gases is a robust geochemical tool to understand, monitor and predict the behaviour of volcano activity, but it is also important to evaluate the effects of volcanic emission on a local and regional scale. The study of the chemistry of atmospheric deposition can provide important information in this regard. Vulcano Island is a stratovolcano located in the southernmost sector of the Aeolian archipelago (Sicily). Since the last eruption occurred in 1888-1890, volcanic emissions are characterized by intense fumarolic activity localized on the northeastern rim of La Fossa crater. Several episodes of volcanic unrest have occurred over the past 130 years, and the most recent period of crisis was between 2021 and 2022. It was characterised by the increasing fumarole temperatures and gas fluxes, shallow long-period seismicity, and diffuse soil degassing around the main crater. This study reports on the chemical composition of rainwater samples collected from November 2021 to January 2023, during the last unrest period of Vulcano Island. Fifteen rainwater samples were collected through a network of three bulk collectors; two of them were placed inside the fumarolic field, and the last one was located near Vulcano Porto. Rainwater samples were analysed for major and trace element contents, and physicochemical parameters were also measured. The pH of rainwater collected near the summit area reaches very low pH values (min 1.63), with a mean value of 2.29, which is significantly lower respect to the mean value at Vulcano Porto (5.7). The concentrations of dissolved solutes in rainfall (expressed as Total Dissolved Solids) are inversely proportional to pH and reach extremely high values in the most acidic samples (up to 1133 mg/L). The most influenced samples by the volcanic emissions are strongly enriched in sulphate, chlorine and fluorine as a direct result of the dissolution of acid gases in rainwater. In addition to the major species, high concentrations of potentially toxic trace elements (Al, As, B, Cd, Fe, Pb, Sb, Te, Ti, Tl, and REE) were found. At the most distal site (Vulcano Porto) the impact of volcanic emissions on rainfall is much less pronounced and the dominant source is mainly related to marine aerosol. These preliminary results on trace element concentrations in rainfall at Vulcano highlight the importance of these studies to fully evaluate the potential impact of volcanic emissions on rainwater and consequently on other environmental matrices (e.g. soils and plants), especially during a period of intense outgassing.

How to cite: Tripodi, F., Brugnone, F., D'Alessandro, W., Bellomo, S., Brusca, L., Paonita, A., and Calabrese, S.: Monitoring of rainwater chemistry during the recent volcanic unrest at Vulcano Island (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15866, https://doi.org/10.5194/egusphere-egu24-15866, 2024.

EGU24-16089 | ECS | Posters on site | GMPV8.7

H2O-vesicle formation in the hybrid region of a bimodal melt system. An experimental progress. 

Laura Luenenschloss, Patricia Louisa Marks, and Marcus Nowak

The eruption behavior of magmas depends strongly on the volatile content of the melt. Dissolved H2O significantly affects magma ascent and the nature of volcanic eruptions. The formation and subsequent growth of fluid vesicles increases the magma volume and thus the internal pressure of the magma chamber. Consequently, the tensile strength of the overlying bedrock may be exceeded, triggering an eruption(1). Vesicle formation may be enhanced in volatile-rich bimodal magmatic systems, such as the Askja eruption in Iceland in 1875(2) and the 16.5 Ma Yellowstone eruption(3).

A bimodal magmatic system can result from a basaltic melt entering a volatile-rich rhyolitic magma chamber, leading to magma mixing, magma mingling, and magma ascent. Experimentally decompressed bimodal hydrous melts show a depletion of alkalis, especially Na2O, in the hybrid zone(4). This amplifies supersaturation of H2O and subsequently the enhanced formation of H2O vesicles in the hybrid zone, as H2O solubility closely correlates with the alkali content of a silicate melt(5).

In general, nucleation is considered as the driving mechanism for vesicle formation of volatiles in silicate melts(6). Nucleation describes the process of the formation of a critical vesicle in the thermodynamically metastable range, which can increase in volume due to diffusion processes, thereby achieving near equilibrium conditions(6). However, decompression rate independent vesicle number densities observed in experimentally decompressed phonolitic melts contradict the results of nucleation theory(7). Instead, the phase separation of H2O from the silicate melt may proceed in the thermodynamically unstable range, in which spontaneous spinodal decomposition is the controlling mechanism.

For further detailed investigation of the mechanisms behind enhanced H2O vesicle formation in the hybrid zone of bimodal melts, we synthesized glass with the hybrid melt composition given in (4).  Subsequently, H2O solubility experiments were conducted in the internally heated argon pressure vessel (IHPV). For this purpose, the hybrid melt was hydrated with H2O excess for 96 h at 1523 K and 60, 80, 100 or 200 MPa, further equilibrated at 1323 K for 0.5 h and then isobarically quenched with 16 or 97 K·s-1. The resulting solubility data are essential to conduct decompression experiments of initially slightly H2O undersaturated melts at rates of 1.7-0.17 MPa·s-1 to the final pressures of 60-100 MPa, followed by the analysis of the H2O vesicle number density, spatial distribution and H2O contents in the decompressed melts with quantitative image analysis and FTIR-spectroscopy and the calculation of the equilibrium porosity. A comparison of the data with the bimodal decompression experiments(4) could provide decisive information on the melt degassing mechanism of hybrid melt zones.

 

(1) Sparks, R. S. J. (1978) Volcanol. Geoth. Res., 3(1-2), 1-37.

(2) Sigurdsson, H., & Sparks, R. S. J. (1981) Petrol., 22(1), 41-84.

(3) Huang, H. H., et al. (2015) Science, 348(6236), 773-776.

(4) Marks, P. L. et al. (2023) J. Mineral., 35(4), 613-633.

(5) Allabar A. et al. (2022) Mineral. Petr., 177(52).

(6) Navon, O. & Lyakhovsky, V. (1998) Soc., Spec. Publ., 145(1), 27-50.

(7) Allabar, A. & Nowak, M. (2018) Earth Planet. Sc. Lett., 501, 192-201.

How to cite: Luenenschloss, L., Marks, P. L., and Nowak, M.: H2O-vesicle formation in the hybrid region of a bimodal melt system. An experimental progress., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16089, https://doi.org/10.5194/egusphere-egu24-16089, 2024.

EGU24-16145 | ECS | Orals | GMPV8.7

Evidence of rapid conduit sealing driving explosive activity at El Reventador (Ecuador) underpinned by a permanent SO2 camera installation. 

Thomas C. Wilkes, Silvana Hidalgo, Jean Battaglia, Tom D. Pering, Marco Almeida, Freddy Vásconez, Carlos Macías, and Dario García

El Reventador is a highly active stratovolcano located ≈90 km east of Quito (Ecuador). Since a paroxysmal eruption (VEI 4) in 2002, it has exhibited persistent open-vent degassing accompanied by frequent vulcanian-/strombolian-style explosions, as well as lava flows and small pyroclastic density currents. The relatively remote nature of this volcano, requiring 4-5 hours of arduous uphill hiking through thick jungle, hinders extensive research on this system. Furthermore, with changeable and often wet weather conditions in the region, reliable remote spectroscopic measurements of gas emissions can be particularly difficult to achieve. These complications highlight the importance of permanent instrument installations that can work autonomously, thus reducing the need for field campaigns and improving the chances of capturing high-quality data and/or interesting volcanic phenomena. Here, we present the first measurements from a permanent SO2 camera installation on El Reventador, focussed on a window of good measurement conditions lasting a few hours on 24th April 2022. During this period, explosions typically occurred at a sub-hourly rate, with varying sizes and repose periods. Prior to a number of the explosions we find a decrease in SO2 emissions suggestive of gas accumulating under a reduced-permeability magma seal in the upper conduit. Sealing appears to occur on the order of 10-20 minutes prior to explosions, although establishing a baseline emission rate for the freely degassing system is often precluded by the frequency of explosions. Indeed, we find periods where permeability in the upper conduit appears to begin reducing immediately after the previous explosion. 

How to cite: Wilkes, T. C., Hidalgo, S., Battaglia, J., Pering, T. D., Almeida, M., Vásconez, F., Macías, C., and García, D.: Evidence of rapid conduit sealing driving explosive activity at El Reventador (Ecuador) underpinned by a permanent SO2 camera installation., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16145, https://doi.org/10.5194/egusphere-egu24-16145, 2024.

EGU24-16170 | Posters on site | GMPV8.7

Volatile degassing at Stromboli Volcano: Continuous soil CO2 fluxes monitoring network and soils discrete measurements. Volcanic implications 

Fabio Vita, Claudio Inguaggiato, Agnes Mazot, Marco Corrao, Marianna Cangemi, and Salvatore Inguaggiato

The Stromboli volcano, Aeolian Islands, Italy, is characterized by persistent Strombolian activity. It is a perfect case study to investigate the relationship between outgassing activity and paroxysmal events.

The discrete soil CO2 degassing measurements, performed with the portable flux meter based on the accumulation chamber method, were carried out in the summit and peripheral zones. These measurements surveys allowed us to individuate the anomalous degassing areas (Scari, Piscità, and Pizzo Sopra La Fossa), coincident with the main structural faults respectively N64° and N41° as preferential paths for the rising of deep fluids.

Based on the information resulting from the discrete measurements a near-continuous (hourly frequency) geochemical network was installed on Stromboli Island and consists of three stations, one located in the summit part of the Pizzo Sopra La Fossa area (STR02), and two located in the peripheral zone STR01 and STR03 in the Scari and Piscità areas respectively. This network allowed us to acquire a large amount of soil CO2 flux data to investigate and model the plumbing volcanic system. The analysis of a large dataset of soil CO2 fluxes collected in the summit crater area (STR02), from 2000 to 2023, showed significant changes in degassing values and style before and in coincidence with major volcanic events like paroxysmal explosions caused by the rapid rise of volatile-rich magma and the changes from explosive to effusive eruptions. In particular, the soil degassing processes of CO2 peaks showed three main and peculiar behaviors:

  • A long-lasting modification, characterized by a slow and continuous increase in CO2 flux;
  • Transient changes, characterized by abrupt changes in the rate of CO2 outgassing;
  • Strong Increase in the Natural Daily Variation, highlighting drastic changes in the degassing style, a few months before the major paroxysmal events.

How to cite: Vita, F., Inguaggiato, C., Mazot, A., Corrao, M., Cangemi, M., and Inguaggiato, S.: Volatile degassing at Stromboli Volcano: Continuous soil CO2 fluxes monitoring network and soils discrete measurements. Volcanic implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16170, https://doi.org/10.5194/egusphere-egu24-16170, 2024.

EGU24-16322 | ECS | Posters on site | GMPV8.7

Reliable Ozone Measurements in Volcanic Plumes: A Way to Resolve the Volcanic Ozone Enigma 

Maja Rüth, Niklas Karbach, Nicole Bobrowski, Ulrich Platt, Bastien Geil, Thorsten Hoffmann, Ellen Bräutigam, and Jonas Kuhn

In addition to CO2 and sulphur dioxide (SO2), volcanic plumes also contain reactive halogen species. Bromine monoxide (BrO) can reliably be quantified by remote sensing measurements and is known to catalyse ozone (O3) destruction. Therefore, local O3 depletion is commonly assumed inside volcanic plumes.
Contrary to popular belief, a calculation comparing atmospheric turbulent mixing with the rate of O3 destruction inside the (young) plume suggests no significant halogen catalysed O3 loss (1% or less) in the plume.

So far, however, O3 and its concentration distribution in volcanic plumes have only been insufficiently determined since commonly used short-path ultraviolet (UV) absorption O3 monitors show a severe, positive interference with SO2, an abundant volcanic gas.
This interference problem can be overcome by using a chemiluminescence (CL) O3 monitor, a standard technique for O3 measurements in the 1970s (and still the standard instrument for air pollution monitoring), which shows no interference with trace gases in volcanic plumes and therefore allows reliable O3 measurements in volcanic plumes.
However, field measurements with existing CL O3 monitors are challenging, since they are usually heavy and bulky. We therefore designed an improved and lightweight version of the CL O3 instrument (1kg, shoebox size), which can be easily carried or mounted onto a drone, thus opening up completely new measurement possibilities.

After test measurements in Heidelberg, including ground-based as well as drone-based measurements, during which we determined vertical O3 profiles, we performed drone-based O3 measurements in the plume of Etna volcano. The latter data show an anti-correlation between O3 and simultaneously determined SO2, suggesting an O3 depletion of up to ~60% in the plume of Etna. This raises the question which – probably unknown - process leads to this observed O3 depletion.

How to cite: Rüth, M., Karbach, N., Bobrowski, N., Platt, U., Geil, B., Hoffmann, T., Bräutigam, E., and Kuhn, J.: Reliable Ozone Measurements in Volcanic Plumes: A Way to Resolve the Volcanic Ozone Enigma, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16322, https://doi.org/10.5194/egusphere-egu24-16322, 2024.

EGU24-17401 | Posters on site | GMPV8.7

Twenty three years of monitoring diffuse CO2 emission from the Tenerife North-West Rift Zone (NWRZ) volcano, Canary Islands 

Victoria Josefina Leal Moreno, Lottie Atton, Fátima Rodríguez, María Asensio-Ramos, Gladys V. Melián, Pedro A. Hernández, Germán Padilla, Nemesio M. Pérez, and Eleazar Padsrón

Tenerife (2,034 km2), the largest island of the Canarian archipelago, is characterized by three volcanic rifts oriented NW-SE, NE-SW and N-S with a central volcanic complex, Las Cañadas Caldera, hosting Teide-Pico Viejo volcanoes. The North West volcanic Rift Zone (NWRZ, 72 km2) of Tenerife is one of the youngest and most active volcanic systems of the island, where four historical eruptions have occurred: the volcanic eruption witnessed by Christopher Columbus in 1492, Boca Cangrejo in 16th Century, Arenas Negras in 1706 and Chinyero in 1909. In order to monitor the volcanic activity of NWRZ, since the year 2000, 56 soil CO2 efflux surveys have been performed at NWRZ (with more than 300 observation sites each one) to evaluate the temporal an spatial variations of CO2 efflux and their relationships with the volcanic-seismic activity. Soil CO2 efflux measurements were performed in accordance with the accumulation chamber method. Spatial distribution maps were constructed following the sequential Gaussian simulation (sGs) procedure. To quantify the total CO2 emission from the studied area, 100 simulations for each survey have been performed. We report herein the results of the last diffuse CO2 efflux survey at the NWRZ undertaken in summer 2023 to constrain the total CO2 output from the studied area. During this survey, soil CO2 efflux values ranged from non-detectable up to 34 g m-2 d-1. The total diffuse CO2 output released to atmosphere were estimated in 311 ± 11 t d-1, value higher than the background CO2 emission estimated on 151 t d-1. Since the 2000s, total CO2 output ranged between 52 and 867 t d-1. Long-term variations in the total CO2 output suggest the occurrence of subsurface magma degassing and magmatic fluid injection, perhaps due to strain-stress changes beneath the NWR zone (Hernández et al., 2017). Regular surveys of soil CO2 efflux seem to be an effective geochemical surveillance tool at the NWRZ, able to detect changes in the CO2 emission rate that might presage future episodes of volcanic unrest.

Hernández et al., (2017). Bull. Volcanol. 79:30.

How to cite: Leal Moreno, V. J., Atton, L., Rodríguez, F., Asensio-Ramos, M., Melián, G. V., Hernández, P. A., Padilla, G., Pérez, N. M., and Padsrón, E.: Twenty three years of monitoring diffuse CO2 emission from the Tenerife North-West Rift Zone (NWRZ) volcano, Canary Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17401, https://doi.org/10.5194/egusphere-egu24-17401, 2024.

EGU24-17761 | ECS | Posters on site | GMPV8.7

Boron and strontium isotopic signature in rainwaters from Mt. Etna, Italy 

Filippo Brugnone, Matteo Salvadori, Maddalena Pennisi, Walter D'Alessandro, Lorenzo Brusca, Francesco Parello, and Sergio Calabrese

The isotopic compositions of boron (δ11B‰) and strontium (87Sr/86Sr) were measured, for the first time, in 10 rainwater samples from Mt. Etna, Italy. The samples were collected during the paroxysmal sequence of 2021-2022. The chemical composition was determined using an ICP-MS, while the isotopic ratios of B and Sr were measured using a mass spectrometer MC-ICP-MS (Neptune Plus™), after specific pre-concentration procedures in clean rooms (class 100 - 1000). In the analysed rainwater samples, the concentrations of B and Sr were between 4.6 µg L-1 and 42.2 µg L-1, and between 9.7 µg L-1 and 541 µg L-1, respectively. Overall, the isotopic composition of B ranging from +1.29‰ ± 0.30‰ to +42.9‰ ± 0.20‰, with a median value of +22.0‰ ± 0.19‰. The lowest δ11B‰ values were measured in the site closest to the main active craters (3.6 km), with a median value of +11.4‰ ± 0.21‰; the highest was measured in the site close to the Ionian Sea (Zafferana Etnea), with a median value of +38.1‰ ± 0.21‰. Strontium (87Sr/86Sr) ratios were between 0.703728 ± 0.000008 and 0.710363 ± 0.000006, with a median of 0.707328 ± 0.000007. The highest and the lowest 87Sr/86Sr ratios were measured in the sites most and less affected by the contribution of the volcanic emissions, with median values of 0.704339 ± 0.000007 and 0.709583 ± 0.000007, respectively. Although exists few data of isotopic ratios of boron and strontium on fluids in volcanic systems (δ11B‰ between -9.3 to 21.4‰), there are no studies on rainwater influenced by volcanic emissions. Nevertheless, the data available in the literature are sufficient to attribute Etna's volcanic source as the major contributor to B and Sr emissions in the atmospheres of this area. The rainwater chemistry of the Zafferana Etnea site was partly influenced by the volcanic source, but the measured isotopic ratios at this site showed a strong contribution from the marine source. The results provide the first comprehensive study of B and Sr isotopes in Mt. Etna rainwater. Two main sources of atmospheric emissions of B and Sr were recognised: sea-salt aerosols and volcanic gases. This research also adds to the potential for the use of B and Sr isotopes as volcanic emissions contribution tracers.

How to cite: Brugnone, F., Salvadori, M., Pennisi, M., D'Alessandro, W., Brusca, L., Parello, F., and Calabrese, S.: Boron and strontium isotopic signature in rainwaters from Mt. Etna, Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17761, https://doi.org/10.5194/egusphere-egu24-17761, 2024.

EGU24-18297 | ECS | Posters on site | GMPV8.7

Dissolved Helium Estimation in the Casaglia Geothermal Reservoir: a Geological Active Area 

Silvia Balzan, Antonio Caracausi, Dario Buttitta, and Massimo Coltorti

Deep fluids and their isotopic signatures, especially He due to its inert nature, are powerful tools for investigating the processes occurring within the crust, as fluids- rocks interaction, storage and transfer mechanism. Numerous studies have emphasized the connection between local seismicity leading to widespread microfracturing processes and an increase in the release of 4He that was previously trapped within minerals. Thus, the episodic degassing of 4He through the crust can sustain the excess of He in natural reservoirs respect to the steady-state diffusion processes.

The aim of this study is to determine whether the quantity of He stored in the geothermal reservoir of Casaglia, an exploited mining concession located at the top of the Dorsale Ferrarese, which is a seismically active area in the Emilia-Romagna Region, can be attributable to long lasting diffusion process and to highlight the contribution that these geochemical approach can provide to enhance the understanding of underground phenomena, revealing changes in the stress field and related earthquakes.

We collect fluids from the reservoir and we analyse their chemical and isotopic composition. In particular, the helium abundance is very high, up to 3956 ppm. It is also characterised by a 3He/4He ratio of 0.02Ra, clearly indicating that the dominant component is attributable to radiogenic 4He produced by U and Th decay in the crust.

The measured total amount of He stored in Casaglia reservoir vary from 107 to 105 mol/km3 rocks, depending on the porosity. This data has been compared with the expected amount of helium accumulated over time under steady-state crustal degassing, which has been computed taking into account the local stratigraphy, the age of formation of the anticline hosting the reservoir (Upper Pliocene - Pleistocene) and the abundances of U and Th in the rocks. The preliminary result shows that there is at least an order of magnitude difference between the experimental evidence and the calculated data in terms of the amount of helium accumulated in the reservoir, even under the most conservative conditions, assuming that there are no losses of 4He due to advection or diffusion processes.

Our study demonstrates that the in-situ production of 4He in the crust and a long-lasting diffusion through the crust are not the main processes that rule the He degassing in the Casaglia reservoir but alternative and episodic processes controlling the transport mechanism act simultaneously.

Finally, exploiting the established association between rock deformation and helium degassing, monitoring helium flux in active tectonic settings may yield valuable insights into variations in the stress field and the occurrence of seismogenic processes. This aspect highlights the applicability of our findings in contributing to the understanding of underground phenomena, emphasizing the potential of geochemical approaches to reveal changes in the stress field and seismic activities.

How to cite: Balzan, S., Caracausi, A., Buttitta, D., and Coltorti, M.: Dissolved Helium Estimation in the Casaglia Geothermal Reservoir: a Geological Active Area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18297, https://doi.org/10.5194/egusphere-egu24-18297, 2024.

EGU24-18957 | Posters on site | GMPV8.7

Decadal monitoring of the soil CO2 outgassing activity of Vulcano Island, Aeolian Archipelago, Italy. 

Salvatore Inguaggiato, Fabio Vita, Claudio Inguaggiato, Agnes Mazot, and Marianna Cangemi

The Active cone of La Fossa caldera is a close conduit volcano affected by solphataric activity, manifested in the hot fluids released from fumaroles and the associated thermal anomalies in groundwater and exposed ground.

The evaluation of the volcanic activity changes are inferred by the near real-time monitoring of soil CO2 fluxes diffused at the La Fossa Cone and the peripheral areas of Palizzi and Levante Bay and by the discontinuous monitoring of CO2 fluxes diffused by soil in areas around the CO2 continuous monitoring stations, La Fossa Cone, Palizzi and Levante Bay. 

In particular, three main changes in degassing activity were recorded in 2009, 2021, and 2022 and allowed us to evaluate in near real-time the level and duration of the exhaling crisis affecting the Island of Vulcano, by measuring the changes in mass and energy carried by the fluid release.

The strong and deep input of volatiles released, in the last decades, from the underlying magma batch strongly modified the chemical composition of the shallow plumbing system, leading the system to an increase in the level of CO2 and energy over time.

How to cite: Inguaggiato, S., Vita, F., Inguaggiato, C., Mazot, A., and Cangemi, M.: Decadal monitoring of the soil CO2 outgassing activity of Vulcano Island, Aeolian Archipelago, Italy., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18957, https://doi.org/10.5194/egusphere-egu24-18957, 2024.

EGU24-19466 | ECS | Posters on site | GMPV8.7

Combining scanning-DOAS and SO2 camera observations leads to more robust volcanic SO2 flux records. 

Giovanni Lo Bue Trisciuzzi, Alessandro Aiuppa, Giuseppe Salerno, Dario Delle Donne, Marcello Bitetto, Luciano Curcio, Angelo Vitale, Joao Pedro Nogueira Lages, Francesco Maria Lo Forte, Filippo Murè, Roberto Maugeri, and Paolo Principato

The volcanic SO2 flux is key indicator of magma influx into the shallower portions of magmatic plumbing systems, and as such is central to volcano monitoring. However, observations are challenged by a variety of technical and methodological caveats and limitations, requiring the use of a multiple-technique approach as a key to acquiring more robust SO2 flux time-series. Here, we compare ~9 years (2014 to 2022) of SO2 flux measurements at Stromboli obtained through (i) a near-vent SO2 camera (UV1 system, managed by UNIPA) and (ii) a network of scanning-DOAS spectrometers (FLAME network, managed by INGV-OE). The UV1 system operates in close proximity to the summit craters (~500 m), while the FLAME network intercepts the volcanic plume from a greater distance (~2 km).

We find remarkable differences in the SO2 flux time-series streamed by the two observational techniques, with the FLAME daily averages fluxes being up to ~200% higher than those seen by the SO2 camera. By examining the individual components involved in the flux calculation, we find the SO2 integrated column amounts (ICAs) to match one each other within a factor 30%. Hence, the large mismatch between the two SO2 fluxes is primarily caused by large differences in the used plume speeds. By applying a simple dispersion model, we find the Stromboli’s plume to exhibit a non-Gaussian dispersion behaviour, in which in-plume SO2 concentrations are non-linearly diluted (upon atmospheric dispersion) as a function of wind intensity. In the “puffing” plume conditions our model suggests for Stromboli, use of wind speed as a proxy for real gas velocity may not be appropriate, as it can lead to a net overestimation of SO2 fluxes when observed by distally operating scanning-DOAS. In contrast, SO2 camera observations can provide more accurate plume transport results, but are challenged by radiative transfer issues in the optically opaque, proximal plume.

Ultimately, we propose a new SO2 flux record for Stromboli that combines DOAS and SO2 camera and takes advantage of the specific advantages of both techniques. Our combined SO2 fluxes is obtained by combining the SO2 camera-derived plume velocities (obtained from the optical flow algorithm applied to high-frequency UV camera images in near-vent conditions) with the FLAME-derived ICAs, recalculated at source conditions using an experimentally derived plume dilution function. The resulting SO2 flux exhibits a stronger correlation with volcanic activity than obtained using any of the two techniques alone. We emphasize that integrating near-vent measurements through UV cameras with distal scanning-DOAS measurements may significantly improve our understanding of volcano degassing dynamics and behaviour.

How to cite: Lo Bue Trisciuzzi, G., Aiuppa, A., Salerno, G., Delle Donne, D., Bitetto, M., Curcio, L., Vitale, A., Nogueira Lages, J. P., Lo Forte, F. M., Murè, F., Maugeri, R., and Principato, P.: Combining scanning-DOAS and SO2 camera observations leads to more robust volcanic SO2 flux records., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19466, https://doi.org/10.5194/egusphere-egu24-19466, 2024.

EGU24-19718 | Posters on site | GMPV8.7

Diffuse CO2 and H2S degassing monitoring at the summit crater of Teide volcano, Tenerife, Canary Islands 

María Asensio-Ramos, Natasha Keeley, Oranna Reichrath, Alexander Riddell, Alba Martín-Lorenzo, Fátima Rodríguez, Gladys V. Melián, Daniel Di Nardo, Germán D. Padilla, Eleazar Padrón, Nemesio M. Pérez, Pedro A. Hernández, and Luca D'Auria

Tenerife, the largest and highest island in the Canarian archipelago, houses the active Teide-Pico Viejo volcanic system. Its structure is shaped by a rift-system with various directions intersecting at this volcanic system. The system’s last eruption in 1798 expelled approximately 12 million m³ of lava across a three-month period, resulting in the formation of a distinct black surface that contrasts sharply with the surrounding. While Teide volcano exhibits a faint fumarolic system, the observed volcanic gas emissions mainly consist of diffuse CO2 degassing.

Spanning from 1999 to 2024, over 200 surveys meticulously assessed CO2 and H2S emissions across 38 strategic sites within the Teide Volcano's summit crater. Portable fluxmeters, equipped with CO2 and H2S sensors, estimated emission rates via the accumulation chamber method. These rates fluctuated between 2.0 and 1,257 tons per day over a 25-year span. Following a seismic swarm in October 2016, there was a general marked escalation in CO2 and H2S emissions, aligning with heightened seismic activity. This shift led to relatively high CO2 emissions, possibly attributed to fresh magma injection and convective mixing catalyzed by the seismic swarm.

It is pertinent to note a distinct event in the latter half of 2023, marked by a notable surge in CO2 and H2S emissions (ranging between 222 and up to 1,257 tons/day for CO2, and 40 to 270 tons/day for H2S), despite a relatively unchanged seismic activity compared to preceding years.

This study highlights the value of examining diffuse degassing in understanding volcanic behavior and forecasting potential volcanic activity. Monitoring these emissions has become a crucial tool in predicting seismic and volcanic unrest, contributing significantly to mitigating volcanic risks in Tenerife.

How to cite: Asensio-Ramos, M., Keeley, N., Reichrath, O., Riddell, A., Martín-Lorenzo, A., Rodríguez, F., Melián, G. V., Di Nardo, D., Padilla, G. D., Padrón, E., Pérez, N. M., Hernández, P. A., and D'Auria, L.: Diffuse CO2 and H2S degassing monitoring at the summit crater of Teide volcano, Tenerife, Canary Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19718, https://doi.org/10.5194/egusphere-egu24-19718, 2024.

EGU24-19758 | ECS | Posters on site | GMPV8.7

Preparatory experiments to investigate the vesicle formation of hydrous lower Laacher See phonolite at near liquidus conditions 

Frederic Hummel, Patricia Louisa Marks, and Marcus Nowak

The Laacher See volcano in the Eifel region of western Germany caused one of the largest eruptions in Central Europe within the last 100,000 years. The Plinian eruptions lasted days to weeks and ejected about 6.3 km³ phonolitic magma. The ascent and subsequent discharge of magma is greatly influenced by the amount of dissolved H2O. During the magma ascent the solubility of H2O in the melt decreases while simultaneously the supersaturation of the melt increases. This is the prerequisite for phase separation, which leads to the formation of volatile bubbles.

A set of high temperature decompression experiments with hydrous lower Laacher See phonolite (LLST) has recently been conducted at high temperature superliquidus conditions of 1323 K and starting pressure of 200 MPa showing spontaneous phase separation (Marks and Nowak 2024) at a final pressure of 80 MPa. In order to investigate the temperature dependence of vesicle formation, preparatory phase relation experiments were conducted in the cold seal pressure vessel at low temperature near liquidus conditions. Synthetic glass cylinders of the LLST composition were hydrated for 11 days with excess H2O at 1123 K and 200, 90, and 70 MPa to obtain H2O solubility data and pressure dependent liquidus conditions.

The hydrated and quenched sample at 200 MPa is a crystal-free homogeneous glass with residual H2O fluid. The H2O content of the glass was determined with FTIR-spectroscopy. The measured H2O content of ~5.7 wt.% at 200 MPa and 1123 K is in good agreement with previous results of Schmidt and Behrens (2008).

In contrast, the samples hydrated at P <200 MPa are partially crystallized. Needle shaped crystals grew from the capsule walls towards the sample center indicating subliquidus conditions. Based on optical microscopy and Raman spectroscopy, the crystal phases are indicative of feldspar. For a detailed phase identification, the samples will be investigated with the electron beam microprobe.

The preparatory samples provide important information on planned low temperature decompression experiments: (1) At 1123 K, 200 MPa, and H2O saturated conditions the melt is superliquidus, which is a prerequisite for homogeneous vesicle formation.  (2) Pressures conditions between 90 and 70 MPa are subliquidus, resulting in partial crystallization of the hydrous melt. This might induce crystal formation during decompression. However, (3) the planned decompression rates of 0.17 and 1.7 MPa·s-1 and experimental run times <15 min are expected to be fast enough to inhibit partial crystallization (Brugger and Hammer, 2010). Therefore, we suggest that the determination of the low temperature near liquidus H2O phase separation mechanism of the lower Laacher See phonolite will be successful.

Marks P. L. and Nowak M., 2024. Decoding the H2O phase separation mechanism as the trigger for the explosive eruption of the Lower Laacher See phonolite. EGU24-7723.

Schmidt, B.C., Behrens, H., 2008. Water solubility in phonolite melts: influence of melt composition and temperature. Chem. Geol. 256, 259–268.

Brugger, C. R. & Hammer, J. E., 2010 Crystal size distribution analysis of plagioclase in experimentally decompressed hydrous rhyodacite magma. Earth Planet. Sci. Lett. 300, 246–254.

How to cite: Hummel, F., Marks, P. L., and Nowak, M.: Preparatory experiments to investigate the vesicle formation of hydrous lower Laacher See phonolite at near liquidus conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19758, https://doi.org/10.5194/egusphere-egu24-19758, 2024.

EGU24-20368 | Posters on site | GMPV8.7

Evidence of pre-eruptive volatile-saturated magmas before the eruption of Agnano-Monte Spina (Phlegrean Fields, Southern Italy) 

Rosario Esposito, Federico Pingitore, and Maria-Luce Frezzoti

Assessing the pre-eruptive dynamic and volatile-saturation conditions of magmas of past eruptions at active volcanic systems is of paramount importance to understand the future behavior of volcanoes capable of high explosive events. Among all active volcanoes on the Earth, Campi Flegrei caldera (CFc) in southern Italy is a well monitored volcano considering the past highly explosive eruptions such as that of the Neapolitan Yellow Tuff (40 km3) occurred 15 ka ago. At the present, CFc has been undergoing through an unrest crisis consisting of a ~120 cm uplift of the central part of the caldera since 2005 (INGV, November 2023 bulletin), rising a debate relative to the origin of this crisis among scientists. The high volcanic risk is derived by the high degree of urbanization at CFc and the proximity to the city of Naples. For assessing the volcanic risk of CFc, scientists have selected the Agnano-Monte Spina (A-MS) eruption as a reference. The A-MS, in fact, represents the highest explosive event for the last 4.5 ka of CFc activity.

We studied 100 clinopyroxenes from pumices of air fall deposit associated to the A-MS, and we studied the petrography of their hosted melt and fluid inclusions (MI and FI respectively). The major and minor element compositions of the selected clinopyroxene were characterized based on electron-microprobe analysis. In addition, the volatile contents of the bubble of MI and FI were studied by using Raman microspectroscopy.

Two groups of clinopyroxene were identified based on mineral chemistry and petrography. On one hand, clinopyroxenes of one group show (1) a light green colour as hand specimen, (2) diopsidic composition (MgO=16-18 wt.%), and (3) resorbed margins. This group of clinopyroxenes was named as MgO-rich cpx. On the other hand, clinopyroxenes of the other group show (1) a showing a dark green colour as hand specimen, (2) salitic composition (MgO=12-14 wt.%), and (3) larger size grain relative to MgO-rich cpx. This group of clinopyroxenes was named as MgO-poor cpx. The most striking difference of these two groups of cpx are the types of MI and FI hosted in the crystals. Glassy MI are found exclusively hosted in the MgO-poor cpx. These glassy MI hosted in MgO-poor cpx show shrinkage bubbles (bubble-bearing MI). In contrast, MgO-rich cpx host MI and FI which were trapped heterogeneously together. Shrinkage bubbles of MI hosted in MgO-poor cpx did not show any Raman signals of volatile species, while FI and shrinkage bubbles of MI hosted in Mg-rich clinopyroxene showed CO2, carbonate, and H2S Raman signals.

Based on our results and data of MI and cpx from the literature, we suggest that a magma mush of relatively less evolved composition associated to MgO-rich cpx was present at shallow depth (~3 km). A deeper and more evolved magma ascended from deeper the plumbing system and mixed with a volatile-saturated mush triggering the A-MS eruption. We further suggested that the shallow magma mush was saturated with a CO2-H2S-rich magmatic fluids, while the deeper and more evolved magma did not present evidence of volatile saturation. 

How to cite: Esposito, R., Pingitore, F., and Frezzoti, M.-L.: Evidence of pre-eruptive volatile-saturated magmas before the eruption of Agnano-Monte Spina (Phlegrean Fields, Southern Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20368, https://doi.org/10.5194/egusphere-egu24-20368, 2024.

EGU24-20543 | Posters on site | GMPV8.7

Do gas fluxes from numerical modeling and from field data match ? 

Marielle Collombet, Alain Burgisser, Didier Bresch, and Gladys Narbona Reina

Modeling magma ascent within volcanic conduits is not an easy task since it involves complex physical interactions between melt, crystals and gas. Since the evolution of gas content mainly controls the eruptive dynamics, we have to do our best to understand and quantify how and when this gas phase exsolves from the melt, expands and finds its way toward the surface, possibly independently from the melt. In order to follow these phenomena with time, we developed a new 1.5D two-phase system which takes, among others, effects of pressure, temperature, volatile exchanges (including diffusion and viscous relaxation) between the melt and gas phases into account. First tests with this numerical model have then been conduced in order to see if we manage to reproduce gas content and gas fluxes prior to the July 2013 vulcanian eruption at Tungurahua volcano in Ecuador.

How to cite: Collombet, M., Burgisser, A., Bresch, D., and Narbona Reina, G.: Do gas fluxes from numerical modeling and from field data match ?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20543, https://doi.org/10.5194/egusphere-egu24-20543, 2024.

EGU24-2097 | Posters on site | GMPV8.8

Degassing from The Nord Stream Leaks as seen from space : an analog for submarine volcanic eruptions.  

Marcello de Michele, Guillaume Carazzo, and Daniel Raucoules

Submarine volcanic activity, constitutes a significant portion of Earth's volcanic events and presents challenges for direct observation due to its predominantly deep-sea occurrence. Despite the rarity of direct observations, insights garnered from shallow eruptions and hydrothermal vents aid in understanding these phenomena. Here, we use the Nord Stream 2 gas leaks in the Baltic Sea region as an analogue to investigate the link between gas emissions at depth and surface manifestations, akin to shallow submarine volcanic degassing. Our study focuses on the mechanical interaction between gas bubbles surfacing from the Nord Stream 2 incident and the resultant sea waves measureable with Sentinel-2 satellite data. We explore the capability of this optical sensor to measure wave celerities and directions generated by the gas plumes impacting the sea surface, inferring gas flow rates at the source. Through a combination of theoretical modeling and satellite-based observations, we measure the kinematic of concentric waves resulting from gas bubble surfacing, presenting a novel method to estimate gas flow rates. Analysis of wave celerities suggests an equilibrium regime, enabling the derivation of gas output rates at depth. Our findings indicate that Sentinel-2 satellite-based measurements can capture and characterize surface waves, offering indirect insights into the dynamics of submarine volcanic gas emissions. We determine a flow rate range of 265 to 400 m³/h, translating to methane gas emissions of 630 to 950 tons/h if considering a source at 70m depth. Furthermore, the use of high-resolution optical satellite missions extends beyond this particular study, holding promising capabilities of detection and characterization of degassing events associated with submarine volcanic eruptions, such as those observed near Mayotte island. The application of our method offers a broader spectrum of observational tools for studying submarine degassing phenomena and complements strategies recommended by the International Methane Emissions Observatory (IMEO) for methane emission characterization. Our study adds up to the methods that advances our understanding of underwater degassing processes and also holds implications for early volcanic unrest detection and risk assessment.

 

 Figure 1. Location of the study area and zooms on the gas leak. Contains modified Sentinel-2 data [2023].

 

How to cite: de Michele, M., Carazzo, G., and Raucoules, D.: Degassing from The Nord Stream Leaks as seen from space : an analog for submarine volcanic eruptions. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2097, https://doi.org/10.5194/egusphere-egu24-2097, 2024.

EGU24-4110 | ECS | Posters on site | GMPV8.8

Large igneous province degassing contributed to elevated atmospheric CO2 concentration in the Eocene 

Xiangsong Wang, Min Sun, and Guochun Zhao

Deep carbon recycling plays a critical role in regulating Earth’s atmospheric CO2 and climate changes through time. However, the fate of subducted carbonate and potential driving factor of elevated atmospheric CO2 concentration in the Eocene are not well constrained. Here, we report Mg-Ca isotope of the Cenozoic (48 Ma) large igneous province (LIP) in the western Tianshan, to trace recycled marine carbonates in the deep mantle and evaluate the amount of magmatic degassed CO2. The basalts possess remarkably lighter δ26Mg and δ44/40Ca values than those of mantle, suggesting a source contributed by isotopically light recycled surficial carbonates. The quantitative modeling of Mg-Ca-Sr-Nd-Pb isotope reveals the Tianshan LIP magmatic CO2 degassing flux (~1.4–4.1 Pg/year) is two orders of magnitude higher than that of arc magmas. We highlight the subducted Neo-Tethyan oceanic lithosphere provided abundant recycled carbonates into mantle source of Tianshan LIP and induced high CO2 degassing fluxes, which contributed to elevated atmospheric CO2 during the Eocene.

Acknowledgements: The present study was financially supported by Hong Kong Research Grant Council Joint Laboratory Funding Scheme (JLFS/P-701/18), NSFC Major Project (41890831) and Hong Kong RGC grants (17307918 and 17308023), and HKU Internal Grants for Member of Chinese Academy of Sciences (102009906) and Distinguished Research Achievement Award (102010100). This work is a contribution of the Joint Laboratory of Chemical Geodynamics between the University of Hong Kong and Guangzhou Institute of Geochemistry, Chinese Academy of Sciences.

How to cite: Wang, X., Sun, M., and Zhao, G.: Large igneous province degassing contributed to elevated atmospheric CO2 concentration in the Eocene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4110, https://doi.org/10.5194/egusphere-egu24-4110, 2024.

EGU24-5975 | ECS | Orals | GMPV8.8 | Highlight

Quantifying daily volcanic SO2 emissions on a global scale 

Ben Esse, Mike Burton, Catherine Hayer, and Manuel Queißer

The expression of volcanic activity at the Earth’s surface is accompanied by the emission of a cocktail of different gases, including water, carbon dioxide, sulphur species, halogens and metals. The composition and magnitude of these emissions reflects the state of magmatic systems, providing insights into volcanic processes and key hazard monitoring information. Many of these products also have serious health implications for local communities and are important species for the global climate. The primary target species for quantification of volcanic emissions is SO2, due to its high prevalence in volcanic emissions, its low typical atmospheric concentration and the ability to detect it remotely using UV and IR spectroscopy from both ground and space.

Satellite instruments provide a global view of volcanic activity through a combination of geostationary and polar orbiting platforms. This is particularly useful for remote or difficult to reach volcanoes, as well as for identifying eruptions from those which have not been historically active. Most previous satellite work has focused on explosive eruptions due to the decreased sensitivity of satellites to SO2 lower in the atmosphere, however recent advances in instrumentation and processing algorithms have opened the possibility of detecting and quantifying passive emissions in the troposphere.

In this work we combine daily SO2 imagery from the TROPOMI satellite instrument with the PlumeTraj back-trajectory analysis toolkit to detect and quantify daily eruptive and non-eruptive SO2 emissions as a function of time and altitude from volcanoes globally throughout the year 2020. We consistently detect more than 20 degassing volcanoes per day, dominated by non-eruptive emissions. We also investigate the emissions with respect to latitude, tectonic setting and volcano type.

These results demonstrate the ability of TROPOMI and PlumeTraj to provide daily automatic SO2 emissions for volcanoes globally. In the future, this analysis will be extended to the full TROPOMI dataset (from 2018 to present) as well as to the development of a near real-time processing workflow. This will generate an invaluable dataset of volcanic degassing for investigating volcanic processes and characterising SO2 emissions as a function of latitude and altitude, an important input for global climate modelling. Finally, the near real-time analysis will provide a key monitoring tool for volcano observatories worldwide.

How to cite: Esse, B., Burton, M., Hayer, C., and Queißer, M.: Quantifying daily volcanic SO2 emissions on a global scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5975, https://doi.org/10.5194/egusphere-egu24-5975, 2024.

EGU24-7784 | Orals | GMPV8.8

Ash dispersion modelling as a tool to constrain source parameters of past volcanic eruptions 

Gill Plunkett, Larry Mastin, and Hans Schwaiger

Understanding the relationship between volcanic eruptions and their associated climate response requires a view extending further back than historical records can provide. Polar ice cores offer one of the best continuous records of past volcanism in the form of sulphates and ash particles preserved in the ice. Because of their light scattering effect, these sulphate aerosols are the dominant volcanic product contributing to annual and muti-annual climate perturbations. The ice-core sulphate record underpins our ability to reconstruct the climate forcing potential of past eruptions but translating the sulphate concentrations within polar ice cores to atmospheric sulphate loading requires knowledge of the volcanic source’s latitude and plume height. While geochemical analysis of the ash particles can identify the source volcano, for prehistoric eruptions there is no primary record of plume height information available.

Here we assess the efficacy of ash dispersion modelling to predict minimum plume height, eruption season and meteorological conditions for events in which there is knowledge only of the source volcano, ash deposition at a given distal location, and ash grain size and shape. We use the eruption of Novarupta-Katmai 1912 as a case study, as ash from this eruption has previously been identified in the North Greenland Ice Core Project (NGRIP) ice core. Using Ash3d software, we model ash dispersion from Novarupta using historical information about the eruption and meteorology to evaluate the sensitivities of the model to parameters such as total grain size distribution, particle shape, ash cloud concentrations over the deposition site and duration of the suspended ash cloud. Using size and shape data from the NGRIP Novarupta-Katmai ash and randomly sampled values of erupted mass, column height, start dates tied to NCEP-NCAR Reanalysis meteorological data, and eruption duration, we run Ash3d simulations of a large series of eruptions from Novarupta, to compare conditions common to “successful” simulations (i.e., those that deposit ash at NGRIP coring site) with known parameters. Our results show that particle shape and size influence the longevity of the ash cloud, requiring longer simulation runs to ensure deposition is captured. We consider the value and limitations of our approach for reconstructing past volcanic plumes and the potential for further developments to aid in our knowledge of past volcanic impacts on climate.

How to cite: Plunkett, G., Mastin, L., and Schwaiger, H.: Ash dispersion modelling as a tool to constrain source parameters of past volcanic eruptions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7784, https://doi.org/10.5194/egusphere-egu24-7784, 2024.

EGU24-10163 | Orals | GMPV8.8 | Highlight

New insights into the relationship between mass eruption rate and volcanic column  

Thomas Aubry, Samantha Engwell, Costanza Bonadonna, Larry Mastin, Guillaume Carazzo, Alexa Van Eaton, David Jessop, Roy Grainger, Simona Scollo, Isabelle Taylor, Mark Jellinek, Anja Schmidt, Sebastien Biass, and Mathieu Gouhier

Understanding the relationship between the mass eruption rate (MER) and volcanic column height is essential for both real-time volcanic hazard management and reconstruction of past explosive eruptions. Using 134 eruptive events from the new Independent Volcanic Eruption Source Parameter Archive (IVESPA, v1.0), we constrain bespoke empirical MER-height relationships for four measures of column height: spreading level, sulfur dioxide height, and two measures of top height, from direct observations and as reconstructed from deposits. These relationships show significant differences, and we discuss implications for their applications in ash dispersion forecasting and modelling volcanic climate impacts. The roles of atmospheric stratification, wind, and humidity remain challenging to detect across the wide range of eruptive conditions spanned in IVESPA, ultimately resulting in empirical relationships outperforming analytical scaling relationships and the Geneva 1-dimensional (1D) volcanic plume model accounting for atmospheric conditions. However, when excluding the IVESPA events with the highest uncertainties, the 1D model progressively outperforms the empirical MER-height relationship. Our findings highlight persisting challenges in constraining the MER-height relation and reinforce the need for improved eruption source parameter databases documenting uncertainties, as well as improved physics-based models.

How to cite: Aubry, T., Engwell, S., Bonadonna, C., Mastin, L., Carazzo, G., Van Eaton, A., Jessop, D., Grainger, R., Scollo, S., Taylor, I., Jellinek, M., Schmidt, A., Biass, S., and Gouhier, M.: New insights into the relationship between mass eruption rate and volcanic column , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10163, https://doi.org/10.5194/egusphere-egu24-10163, 2024.

EGU24-12580 | ECS | Orals | GMPV8.8

A satellite study of the volcanic plumes produced during the April 2021 eruption of La Soufrière, St Vincent 

Isabelle A. Taylor, Roy G. Grainger, Andrew T. Prata, Simon R. Proud, Tamsin A. Mather, and David M. Pyle

The April 2021 explosive eruption of La Soufrière, St Vincent, produced plumes of ash and SO2 which were observed with multiple satellite instruments. In this project these were studied with the Advanced Baseline Imager (ABI) on the Geostationary Operational Environmental Satellite (GOES) and the Infrared Atmospheric Sounding Interferometer (IASI) onboard the three MetOp satellites.

The high temporal resolution of the ABI instrument (1-10 minutes) was used to identify the approximate start and end times of each eruptive event during the 14-day eruption. There were a minimum of 35 explosive events which have been divided into four phases. The first was an initial explosive event, which was followed by a sustained event lasting over nine hours. The eruption then entered a pulsatory phase which consisted of 25 explosive events in a 65.3 hour period. Finally, there was a waning sequence of events. Over the final two phases, the duration of each event and the repose time between them was shown to increase.

The IASI instrument has sensitivity to sulfur dioxide (SO2) which can be exploited to flag pixels containing SO2 and then to quantify the amount and height. Using IASI data, the SO2 plume was tracked as it was transported around the globe between –45 and 45° N. The retrievals showed a complex structure to the plume which may reflect the multiple explosive events that occurred. Most of the SO2 was shown to be in the upper troposphere and lower stratosphere. A peak SO2 mass loading of 0.31 ± 0.09 Tg occurred on 13 April a few days after the eruption began. The total mass values were converted into fluxes, with the highest fluxes occurring in the first few days of the eruption. In total it is estimated that the eruption emitted 0.63 ± 0.5 Tg of SO2.

A number of similarities between the 1979 and 2021 eruptions of La Soufrière were observed in this study. These include the sequence of events with both eruptions including a pulsatory phase and the plume heights. These similarities highlight the value of these studies for better understanding eruptive events.

How to cite: Taylor, I. A., Grainger, R. G., Prata, A. T., Proud, S. R., Mather, T. A., and Pyle, D. M.: A satellite study of the volcanic plumes produced during the April 2021 eruption of La Soufrière, St Vincent, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12580, https://doi.org/10.5194/egusphere-egu24-12580, 2024.

EGU24-13523 | Orals | GMPV8.8

Nitrates Production by Volcanic lightning during Explosive Eruptions 

Delphine Contamine, Erwan Martin, Adeline Aroskay, Slimane Bekki, Sophie Szopa, and Joël Savarino

Volcanic lightning during explosive eruptions has been suggested has a key process in the abiotic nitrogen fixation in the early Earth. Although laboratory experiences and thermodynamic models convincingly suggest that volcanic lightning can fix atmospheric nitrogen (e.g. Navarro-Gonzalez et al., 1998, Martin et al., 2007). No geological archives of N-fixed by volcanic lightning have been found yet. Recently, high nitrate concentrations in volcanic deposits from large Neogene explosive eruptions (VEI>7; Aroskay et al. 2023) have been discovered. It is tempting to infer that these nitrates correspond to the end-product of N-fixation by volcanic lightning. However long-term atmospheric deposition of nitrate is suggested to be responsible of nitrate deposits in arid environment (e.g. Atacama Desert and Mojave Desert – Michalski et al. 2004, Lybrand et al. 2013). Therefore, the long-term atmospheric deposition could contribute to nitrates preserved in volcanic deposits.

Our study aims to distinguish the origin of nitrates in volcanic deposits: end-product of volcanic lightning or long term atmospheric deposition? To answer this question, volcanic samples from super-eruptions as well as sediments have been collected in the Tecopa Basin – California, USA. The whole sedimentary column (sediments interspersed with volcanic deposits) has been preserved in the same arid conditions for the last 2Ma. The multi-isotopic composition of nitrate has been measured (δ18O, δ15N and Δ17O) and shows clear distinction between nitrate from volcanic deposits and those from sediments. It appears that while nitrate from sediments result from a mix between atmospheric nitrate and biogenic nitrate, in volcanic deposit the nitrate are most likely the end product of volcanic lightning.

As a conclusion, we demonstrate that volcanic deposits can be an archive of N-fixation by volcanic lightning. This is an open window on the direct quantification of N-fixation by large explosive volcanic eruptions and their role on the development of life on the early Earth.

How to cite: Contamine, D., Martin, E., Aroskay, A., Bekki, S., Szopa, S., and Savarino, J.: Nitrates Production by Volcanic lightning during Explosive Eruptions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13523, https://doi.org/10.5194/egusphere-egu24-13523, 2024.

EGU24-14074 | ECS | Orals | GMPV8.8

Millimeter wave radars: the way forward for remote sensing of ash plumes? 

Vishnu Nair, Anujah Mohanathan, Michael Herzog, David Macfarlane, and Duncan Ferguson

Ground-based observation of volcanic ash clouds after an eruption is currently done using weather radars which were originally designed for monitoring meteorological clouds. As ash particles and aggregates have different sizes and refractive indices compared to raindrops and ice crystals, certain parts of the volcanic ash cloud can go undetected by these low frequency weather radars. This can lead to incorrect predictions from the volcanic ash transport prediction models to the aviation industry; the field could benefit from higher frequency radars designed exclusively for ash cloud monitoring. However, the increased sensitivity to fine ash from high frequency signals comes at a cost of significant path attenuation as the wavelengths (in the order of millimeters) are comparable to the ash sizes, and any selection of frequencies should take into account the increased attenuation. In this talk we present a radar forward operator SynRad that numerically simulates the radar measurement process and generates synthetic return signals. SynRad is used to evaluate the performance of three radar frequency bands (C-,Ka- and W-bands) to detect a volcanic ash cloud. The numerically simulated volcanic ash cloud of the Redoubt 2009 eruption serves as the case study. Results suggest that a dual-frequency radar with a C- and Ka-band is the best option to detect the predominantly larger ash particles and aggregates at the early stages of the eruption and the fine ash in the distal ash cloud during the later stages of the eruption respectively. The W-band radar undergoes heavy attenuation at all locations except for downwind of the ash cloud. 

How to cite: Nair, V., Mohanathan, A., Herzog, M., Macfarlane, D., and Ferguson, D.: Millimeter wave radars: the way forward for remote sensing of ash plumes?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14074, https://doi.org/10.5194/egusphere-egu24-14074, 2024.

Explosive volcanic eruptions can damage or destroy surrounding forests, with the potential to alter their characteristics over different timescales. The damage can range from minor/temporary damage to total destruction and burial of vegetated landscapes. While eruptions resulting in vegetation damage over 100s of kilometres are rare, some volcanoes regularly impact and damage local vegetation, with frequencies of months to decades. The intensity and mechanism of the driving volcanic process influences the extent and style of the forest damage, with resulting timescales and patterns of regrowth reflecting the nature of initial impacts and local floral, climatic and environmental parameters.

As such, vegetation damage holds potential as a novel proxy for the magnitude and nature of volcanic eruptions. Particularly in the case of volcanic eruptions without recorded observations, vegetation damage could potentially constrain parameters such as tephra-fall deposit thickness, dispersal and pyroclastic density currents (PDC) distribution. Additionally, mapping the initial impact and trajectories of recovery are key to understanding the long-term environmental consequences of volcanic eruptions. Here, we aim to constrain eruption magnitudes and deposit volumes, particularly in remote environments, using optical (Landsat 8, Sentinel-2) and radar (Sentinel-1) satellite data to study forest disturbance and recovery following an explosive volcanic eruption in Southern Chile: the 2015 eruption of Calbuco volcano.

The 2015 eruption of Calbuco consisted of three explosive episodes between the 22nd-23rd of April resulting in buoyant ash plumes depositing tephra over 100s km2, pyroclastic flows reaching over 6km and lahars reaching over 15km. Thus, different intensities and spatial extents of damage were experienced by the surrounding temperate broadleaf forests. We identify areas impacted by the different eruptive deposits using the disturbance and recovery signatures from the optical and radar satellite data. We observe a decrease in vegetation coverage and health immediately following the eruption in the areas impacted by PDCs, lahars and tephra. PDC impacted regions exhibit the greatest decrease in vegetation coverage and health, and consequently a much slower vegetation recovery rate. We develop a satellite-based methodology through time series analysis and cluster analysis to understand the impact of explosive volcanic eruption on vegetation properties. This allows us to assess the extent and severity of forest disturbance caused by the eruption and to map the rates of post-eruption vegetation recovery. We hope to expand this methodology to be applied to different ecosystems and for different styles of eruption using freely available satellite data. With the eventual aim of developing a toolkit for identifying the footprint of past volcanic eruptions on forest environments.

How to cite: Udy, M., Ebmeier, S., Watt, S., and Hooper, A.: Constraining explosive volcanic eruption parameters and environmental impacts using remote sensing observations of forest disturbance and recovery., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15840, https://doi.org/10.5194/egusphere-egu24-15840, 2024.

EGU24-18896 | ECS | Orals | GMPV8.8

The 2021 paroxysmal events at Mt. Etna: Modelling of SO2 and volcanic ash dispersion by using WRF-Chem model 

Agostino Semprebello, Giuseppe Salerno, Alessandro Gattuso, Pasquale Sellitto, Maria Teresa Caccamo, Manfredi Longo, and Salvatore Magazù

From 18 January to 23 October 2021, 58 paroxysmal events occurred at Mt. Etna volcano by the South East Crater (SEC). Three events, that occurred on 4, 12 March and 24 June, were selected to be studied through a plume dispersion modelling approach. All the selected paroxysms generated ash-SO2 rich plumes ranging from 6 to 8.5 km above the main vent.
In this work, we explored the spatial dispersion of the volcanic SO2 plume in each paroxysmal event by using the Weather Research and Forecasting Chemistry (WRF-Chem) model coupled with the time-variable ground-based SO2 flux emission data recorded by FLAME (FLux Automatic MEausurement) scanning spectrometers network managed by INGV-OE (Osservatorio Etneo). In this context, WRF-Chem was specially configured to run with variable Eruption Source Parameters (ESPs), reading at each integration time-step experimentally measured SO2 flux values.
The SO2 maps resulting from the WRF-Chem simulations were compared with the dispersion pattern detected by TROPOMI sensor onboard Sentinel-5p satellite, in order to validate the capability of the model in reproducing the volcanic plume dispersion. The comparison for each simulation highlights a very good agreement between simulated data and those observed by the satellite.
The ash transport was also modelled in each simulation, considering an ash Mass Eruption Rate (MER) which was inverted from the plume height. The spatial evolution of the ash patterns was compared with data retrieved from the MGS-SEVIRI satellite. The comparison shows a good agreement between simulated and observed maps. Particularly for the 12 March event, the ash comparison clearly shows that the WRF-Chem model was able to well reproduce the eastward path of the ash cloud, even at long distances, as the simulated plume reached Greece about 10 hours after the paroxysm, in agreement with satellite observations.
In conclusion, the obtained results testify that the WRF-Chem model can efficiently reproduce the dispersion of both SO2 and ash plume emitted from Mt. Etna volcano over the Mediterranean basin, representing a powerful tool for assessing air quality, flying security and other hazard factors due to volcanic plume transport and deposition from local to Mediterranean scale. In addition, the performed simulations highlighted that the ground-based data measured by the FLAME network play a key role in improving the accuracy in simulating the SO2 dispersion pattern as it allows us to take into account the fluctuating and not stationary nature of volcanic plume emissions.

How to cite: Semprebello, A., Salerno, G., Gattuso, A., Sellitto, P., Caccamo, M. T., Longo, M., and Magazù, S.: The 2021 paroxysmal events at Mt. Etna: Modelling of SO2 and volcanic ash dispersion by using WRF-Chem model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18896, https://doi.org/10.5194/egusphere-egu24-18896, 2024.

EGU24-19256 | ECS | Orals | GMPV8.8

Detection and classification of volcanic ash based on satellite UV/VIS measurements  

Alon Azoulay, Pascal Hedlt, and Dmitry Efremenko

Volcanic eruptions impact human populations and the environment, with volcanic ash contributing to these effects through its influence on air quality, agriculture, and air transportation. Traditional satellite observation methods for monitoring volcanic ash encounter several challenges, including distinguishing ash from other aerosols, coverage area limitations, frequency of observations, and the impact of adverse weather and atmospheric conditions. These issues highlight the need for supplementary satellite-based approaches to improve volcanic ash monitoring. This project introduces a new method that utilizes machine learning techniques to analyze UV and visible satellite data for detecting and classifying volcanic ash. The research focuses on exploring how satellite UV and visible light observations can be used to identify volcanic ash in the atmosphere. A classifier was developed using simulations from a radiative transfer model, which represents various atmospheric scenarios. This classifier is then applied to analyze spectral measurements obtained by the TROPOspheric Monitoring Instrument (TROPOMI) on the ESA Sentinel-5p satellite. The complexity of detecting and classifying volcanic ash arises not only from the presence of other aerosols in the atmosphere but also from the changing characteristics of the ash, influenced by the type of magma and ongoing alterations as the ash remains airborne. This research presents progress in tackling these challenges and in developing a complex algorithm that incorporates a wide range of parameters. The application of this method to the Raikoke eruption case study enables the identification of some volcanic ash, illustrating the potential of this approach. However, this case study also reveals the presence of misclassifications, highlighting the need for continuous improvement in the classifier. This research offers valuable insights into the detection and classification of volcanic ash, contributing to the enhancement of monitoring strategies for hazard mitigation.

How to cite: Azoulay, A., Hedlt, P., and Efremenko, D.: Detection and classification of volcanic ash based on satellite UV/VIS measurements , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19256, https://doi.org/10.5194/egusphere-egu24-19256, 2024.

EGU24-20188 | Posters on site | GMPV8.8

Comparison of remote sensing ground based systems for volcanic emission monitoring 

Stefano Corradini, Lorenzo Guerrieri, Alessandro La Spina, Luca Merucci, Guseppe Salerno, Hugues Brenot, Martina Friedrich, Robin Campion, Claudia Rivera Cardenas, Dulce Maria Vargas Brancamontes, Gonzalez Gonzalez, and Lizzette Rodríguez Iglesias

Ground-based remote sensing systems provide safe, real-time, continuous and reliable measurements of parameters of volcanological interest and have become indispensable tools for monitoring volcanic activity and potentially mitigating its effects on the environment and local communities. Ground-based systems, where installed, offer continuous spatial and temporal coverage, providing data of high resolution and sensitivity, which are essential for validating satellite data The latter are characterised by much greater density and larger spatial coverage, and for this reason have now become irreplaceable for volcanic monitoring on a global scale.    

This work presents the preliminary comparison results of simultaneous measurements from ground-based systems, consisting of different types of instruments operated by several international research groups. Among these, the most relevant systems we used were (1) a new portable and low-cost TIR system consisting of three collimated cameras, one in the visible, a panchromatic TIR in the 8-14 μm window and an identical TIR camera filtered with a bandpass centred at 8.7 μm, for the detection of SO2 emission height, columnar content, and flux, (2) two high-performance SO2 dual UV imaging systems (EnviCam3) with synchronous acquisition of images (on- and off-band wavelength channels for SO2 detection), and an integrated spectrometer (co-aligned with cameras to provide calibration of SO2 retrievals), (3) a MAX-DOAS, and (4) an IR camera continuously looking at Popocatépetl thermal anomalies.  

The described ground-based systems were used for simultaneous volcanic emission monitoring measurements of Sabancaya Volcano, Perú, and Popocatépetl Volcano, Mexico, in dedicated field campaigns organized in November 2022, and February 2024 respectively, partly funded by the INGV ATTEMPT and DYNAMO projects, and the KAIROS project (SESAR 3 Joint Undertaking).The SO2 fluxes time series obtained from the different ground based systems were cross-compared with each other and with the flux retrieved by the TROPOMI instrument on board the S5p satellite.These types of comparative measurements represent a significant step forward in understanding the relationships between the various ground-based measurements carried out, their use for validating space-based measurements and, in particular, the estimation of SO2 flux using remote sensing optical methods.

How to cite: Corradini, S., Guerrieri, L., La Spina, A., Merucci, L., Salerno, G., Brenot, H., Friedrich, M., Campion, R., Rivera Cardenas, C., Vargas Brancamontes, D. M., Gonzalez, G., and Rodríguez Iglesias, L.: Comparison of remote sensing ground based systems for volcanic emission monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20188, https://doi.org/10.5194/egusphere-egu24-20188, 2024.

GMPV9 – Active volcanism: hazards, monitoring, human response, mitigation and risk

EGU24-563 | ECS | Posters on site | GMPV9.1

Generalizability of AI-based Emulators for CFD Lagrangian methods  

Eleonora Amato, Vito Zago, and Ciro Del Negro

The combination of Computational Fluid Dynamics (CFD) and Artificial Intelligence (AI) enables to expand the scope of fluid modeling and improve simulation performance. Eulerian methods have already been extensively integrated with AI, providing high-fidelity and reliable results (e.g., weather prediction); the application of AI to Lagrangian methods remains less consolidated. Smoothed Particle Hydrodynamics (SPH) is a Lagrangian mesh-less CFD numerical method with well-established advantages for the simulation of highly dynamic free-surface complex fluids. However, reliable SPH simulations require long execution times and large computational resources. This downside can be resolved using emulators, which can reproduce the dynamics of a physical system, speeding-up the simulations. In detail, an emulator is a model in which AI algorithms join or replace the equation-based mathematical representation of physics. Thus, the emulator learns from CFD simulations the behavior of the CFD reference model and reproduces it to solve fluid dynamics problems in shorter times. For the emulator to be trusted, it is important to assess the ability to generalize and correctly predict the behavior of the fluid in conditions that have not been presented during training phase. Here, we present the generalizability of an AI-based emulator for SPH, utilizing an Artificial Neural Network (ANN) to estimate the hydrodynamic forces between SPH particles. We demonstrate the capability of the emulator to reproduce particle interaction quantities, as opposed to their specific spatial configuration. Therefore, when a different problem is treated, as long as the variables values are in a range with physics meaning presented during training, the emulator will be capable to produce physically meaningful results. We discuss the salient points of designing this emulator, such as the choice of the AI model, i.e., the ANN, and the choice of the features. We show applications to different test cases, highlighting the emulator ability to generalize for problems with varying levels of complexity, and for changes in the model resolution.

How to cite: Amato, E., Zago, V., and Del Negro, C.: Generalizability of AI-based Emulators for CFD Lagrangian methods , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-563, https://doi.org/10.5194/egusphere-egu24-563, 2024.

EGU24-564 | ECS | Posters on site | GMPV9.1

How Machine Learning and Satellite Data Enhance Near-Real Time Detection of Volcanic Activity Worldwide 

Simona Cariello, Claudia Corradino, Federica Torrisi, and Ciro Del Negro

Nowadays, several satellite missions provide thermal infrared data at various spatial resolutions and revisit time, enabling nearly continuous monitoring of thermal volcanic activity worldwide. In addition, computer vision techniques, based on Machine Learning (ML) and Deep Learning (DL) models, offer unique advantages in automatically extracting valuable information from large datasets. Here, we propose a Machine Learning approach that leverages the capabilities of such models, combined with nearly continuous high spatial resolution images (20 m) acquired from the Sentinel-2 MultiSpectral Instrument (S2-MSI), to detect high-temperature volcanic features and to quantify volcanic thermal emissions. The impact of the volcanic activity is assessed based on the spatial distribution of the erupted products. Spatially characterizing the detected thermal anomalies allows us to both highlight significant pre-eruptive thermal changes and estimate the areal coverage, length of the erupted products, and the lowest altitude reached by them. We utilize the entire archive of high spatial resolution Sentinel-2 data, which comprises more than 6000 S2-MSI scenes from ten different volcanoes around the world. By employing a “top-down” cascading architecture that integrates two distinct Machine Learning models, a scene classifier (SqueezeNet) and a pixel-based segmentation model (Random Forest), we achieve very high accuracy, specifically 95%. This result comes from overcoming the limitations of the scene-level DL classification model, which compresses the entire spatial and spectral information into one unique label, by relying on the pixel-level Random Forest (RF) model. The use of multiple models allows to create more robust and powerful predictors making this tool suitable for near real time volcanic activity detection. These results demonstrate that the cascading system processes any available S2-MSI image in near-real time, providing a significant contribution to the monitoring, mapping, and characterization of volcanic thermal features worldwide.

How to cite: Cariello, S., Corradino, C., Torrisi, F., and Del Negro, C.: How Machine Learning and Satellite Data Enhance Near-Real Time Detection of Volcanic Activity Worldwide, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-564, https://doi.org/10.5194/egusphere-egu24-564, 2024.

EGU24-822 | ECS | Posters on site | GMPV9.1

Joint use of machine learning and geostationary satellite data for volcanic ash cloud detection 

Federica Torrisi, Claudia Corradino, Simona Cariello, Taryn Lopez, and Ciro Del Negro

During an explosive eruption, a major hazard to population can be represented by the ejection in the atmosphere of gases and ash, with the consequent creation of volcanic clouds, which can compromise aviation safety. The combined use of a variety of satellite data in different spectral ranges with diverse spatial and temporal resolutions allows us to continuously monitor volcanic ash clouds in an efficient and timely manner. Specifically, the latest generation of high temporal resolution satellite sensors, such as EUMETSAT MSG Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and GOES18 Advanced Baseline Imager (ABI), provide almost continuous radiometric estimates to track the entire evolution of volcanic clouds produced by worldwide volcanoes. Therefore, leveraging the strengths of these satellite sensors, which provide frequent observations at a wide variety of wavelengths, can provide critical information to help understand volcanic processes and extract eruptive products. Nevertheless, the satellite data volume is too large for ad hoc processing and analysis especially when considering daily global-scale observations. Deep learning (DL), a fastest-growing technique of artificial intelligence in remote sensing data analysis applications, has an excellent ability to learn massive, high-dimensional image features and has been widely studied and applied in classification, recognition, and detection tasks involving satellite imagery.

Here, we developed a new DL model, based on Deep Convolutional Neural Networks (CNNs), which exploits a variety of spatiotemporal information mainly coming from geostationary satellite sensors. It is trained on a combination of Thermal Infrared (TIR) bands acquired by MSG-SEVIRI and GOES18-ABI. The proposed model aims to extract complex spectral and spatial patterns autonomously to recognize a volcanic ash cloud. Preliminary capabilities and limitations of this model will be presented here. Thanks to the wide area covered by these satellite sensors, it is possible to apply this model to different volcanoes. Specifically, this model has been applied to the paroxysmal events that occurred at Mt. Etna (Italy) between 2020 and 2020 and at Shishaldin (Alaska, USA) in 2023.

How to cite: Torrisi, F., Corradino, C., Cariello, S., Lopez, T., and Del Negro, C.: Joint use of machine learning and geostationary satellite data for volcanic ash cloud detection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-822, https://doi.org/10.5194/egusphere-egu24-822, 2024.

EGU24-1030 | ECS | Posters on site | GMPV9.1

A Remote Sensing Data Fusion algorithm for Near Real time monitoring of Volcanic Radiative Power 

Giovanni Salvatore Di Bella, Claudia Corradino, Simona Cariello, Federica Torrisi, and Ciro Del Negro

Nowadays, near-real time volcano monitoring at global scale is made possible thanks to the thermal infrared sensors on board of several satellite platforms providing accurate estimates of the volcanic thermal emissions. In particular, they are able to provide reliable estimates of the Volcanic Radiative Power (VRP), i.e. the heat radiated during the volcanic activity. In addition, Remote Sensing Data Fusion (RSDF) techniques allow to combine data from multiple satellite sensors to improve the potential values of the single source and to produce a high-quality data representation. Fusion techniques are useful for a variety of applications, ranging from object detection, to object tracking, change detection. In particular, we aim to use them to integrate the different satellite data acquired with different spatial and spectral resolutions to produce fused data that contains more detailed information than each of the data sources. We introduce a novel RSDF algorithm deployed in a Cloud Computing environment to monitor VRP worldwide from multiple multispectral satellite sensors, namely the polar MODIS, SLSTR and VIIRS and the geostationary SEVIRI. The RSDF algorithm demonstrates heightened sensitivity in detecting high-temperature volcanic features and thus VRP monitoring compared to conventional already processed Level 2 products available online. Specifically, the overall accuracy has improved in terms of omitted rate and false detections, reducing from 78% to 5.3% and from 6.5% to 4.7%, respectively. The decision to combine the use of different satellite sensors stems from the need to offer complete continuous monitoring of each volcanological phenomenon, taking advantage of each sensor's own characteristics.

How to cite: Di Bella, G. S., Corradino, C., Cariello, S., Torrisi, F., and Del Negro, C.: A Remote Sensing Data Fusion algorithm for Near Real time monitoring of Volcanic Radiative Power, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1030, https://doi.org/10.5194/egusphere-egu24-1030, 2024.

EGU24-2013 | ECS | Posters on site | GMPV9.1

Assimilation of geodetic data for volcanic hazard assessment in near-real time by means of a particle filter 

Léa Zuccali, Virginie Pinel, and Yajing Yan

In a perspective of volcanic hazard assessment, it is fundamental to be able to determine as early as possible whether, where and when the magma that has started to propagate from the storage zone will reach the surface. The propagation phase is generally rapid, lasting from a few hours to a few months, but it induces seismicity and deformation signals recorded by continuous sensors and InSAR data. Furthermore, dynamic numerical models can be used to calculate the trajectory and the velocity of magma propagation as a function of the physical properties of the magma and the crust, and the initial conditions (local stress field and magma reservoir location).

Data assimilation is a method that combines a dynamic model with current and past observations based on error statistics and predicts the future state of the observed system.This method therefore appears to be an appropriate tool for addressing the need to predict the position and timing of a volcanic eruption based on available models and observations.

The particle filter is particularly noteworthy for its ability to handle nonlinear models and non-Gaussian error statistics. This method is based on a representation of the probability density of the dynamic model by a discrete set of model states (particles) and relies on Bayes' theorem.

In order to assess the potential of the particle filter for tracking magma propagation at depth, we implemented this assimilation strategy by considering, in two dimensions, the case of magma propagating beneath a caldera in an extensional stress field. The input parameters of the propagation model are the initial position of the magma at depth, its viscosity and driving pressure, the volume of magma injected, the crustal rigidity, and the local stress field characterized by the balance between tectonic extension and caldera unloading. Surface displacements induced by magma propagation are estimated using an Okada dislocation model. We first validate our assimilation strategy with synthetic data in order to take into account geodetic data recorded on volcanic systems in the future.

How to cite: Zuccali, L., Pinel, V., and Yan, Y.: Assimilation of geodetic data for volcanic hazard assessment in near-real time by means of a particle filter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2013, https://doi.org/10.5194/egusphere-egu24-2013, 2024.

EGU24-2410 | ECS | Orals | GMPV9.1

Joint analysis of seismic velocity change, deformation and meteorological data for volcano monitoring 

Quentin Dumont, Takeshi Nishimura, Takashi Hirose, and Tomoya Takano

Detection of subtle precursors to forecast the timing and location of eruptive events are one of the main issues in volcanic risk mitigation. Seismic interferometry of ambient noise allows to detect very small change in the medium, but is affected by numerous processes such as strain and meteorological variations that need to be identified and characterized in order to correctly interpret the observation for operational monitoring. To assess the monitoring potential of the seismic velocity changes, we jointly analyzed 10 year time series of velocity, strain and meteorological changes at 21 Japanese volcanoes. They span different environmental conditions and volcanic behavior, insuring a broad sample of velocity–strain–environmental interactions.

Daily seismic velocity changes were computed considering three frequency bands (0.5-1 Hz, 1-2 Hz and 2-4 Hz). Daily meteorological data were provided by the Japan Meteorological Agency (JMA). Deformation data include (1) areal strain computed from the GNSS stations of the JMA and Geonet network (from Geospatial Information Authority of Japan), and (2) numerically computed tidal strain by using GOTIC2 software (Matsumoto et al., 2001).

We assumed the velocity change to results from the linear combination of the strain and meteorological changes (including rainfall, snow load, temperature, atmospheric pressure, wind speed and sea level variations), and inverted their respective contributions to the observed velocity variation using a least-squares method.

Over the 21 volcanoes, the inversion of the parameters are able to explain 20-30% of the data in average. We determine that areal strain and temperature have, on average, a high impact on velocities (each representing ≈20% of the modeled velocities) but also shows a high variability from volcano to volcano, while pore pressure and sea level variations, which shows almost same amount of contribution to the velocities (≈20%), have a much lower variability indicating a background effect found at more or less all volcanoes. Atmospheric pressure and wind speed show similar behavior but at a lower level (≈10%). Snow have a relatively low impact over the whole year (≈5%) but it strongly increases during winter (up to 30%). Tidal strain do not demonstrate significant effect on daily velocity variations.

In the details of each volcano, results demonstrate the possibility to retrieve the different component contributing to the measured velocity change. This shows encouraging results for several subsequent application such as: (1) detection of small eruptive precursor by removing the modeled contributions, (2) use of the velocity change as a stress monitoring proxy based on the determined strain sensitivity, (3) monitoring pore pressure change especially for lava dome stability. We also highlight the need for collocated seismic and meteorological sensors to achieve higher accuracy in the environmental effect correction.

How to cite: Dumont, Q., Nishimura, T., Hirose, T., and Takano, T.: Joint analysis of seismic velocity change, deformation and meteorological data for volcano monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2410, https://doi.org/10.5194/egusphere-egu24-2410, 2024.

EGU24-5254 | ECS | Posters on site | GMPV9.1

Advancing volcano surveillance through soil gas monitoring: insights from Stromboli Island, Italy. 

Mirko Messina, Roberto Di Martino, and Antonio Paonita

Soil gas monitoring proves to be a powerful tool for studying volcanoes and their subsurface dynamics. Various gas species are examined as indicators of volcanic activity, with a focus on understanding the processes governing gas emissions. Carbon dioxide (CO2) is of particular interest due to its significant release during both active volcanic periods and periods of dormancy. Hydrogen (H2) concentration is also analysed to gain insights into the oxygen fugacity of magmatic gases, a parameter that influences the redox state and the distribution of elements among solid, fused, and gas phases.

To effectively monitor volcanic gases, automated geochemical stations are deployed to simultaneously measure multiple gas species. This study presents a comprehensive analysis of reducing capacity monitoring data collected at Stromboli during the 2021-2023 time window. This station records data on molecular hydrogen (H2) concentration, CO2 flux, CO2 concentration, soil water content, atmospheric pressure, temperature, and relative humidity.

The dataset underwent normalization of variables and filtering processes of spurious data to facilitate Principal Component Analysis (PCA), allowing for the identification of linear dependencies among the variables. The results of the PCA reveal insights into the relationships of the monitored parameters, shedding light on potential factors influencing volcanic activity.

These data reveal variations in reducing capacity and soil CO2 flux that correlate with changes in Stromboli's eruptive activity. The delay in CO2 variations following shifts in reducing capacity is attributed to the advective-diffusive transport of gases through the volcanic rock formations. This research contributes to a deeper understanding of the volcanic degassing of Stromboli and shows the efficacy of combining multiple regression analysis methods for filtering geochemical datasets. This research enhances our understanding of volcanic behaviour and aids in volcano monitoring efforts.

How to cite: Messina, M., Di Martino, R., and Paonita, A.: Advancing volcano surveillance through soil gas monitoring: insights from Stromboli Island, Italy., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5254, https://doi.org/10.5194/egusphere-egu24-5254, 2024.

EGU24-5284 | ECS | Posters on site | GMPV9.1

Thermal remote sensing of lava lakes: a comparison of approaches 

Sofie Rolain, Dries Peumans, and Benoît Smets

Satellite-based thermal remote sensing is a useful tool for monitoring volcanoes. It involves detecting thermal anomalies, called 'hotspots,' and calculating the radiative energy emitted by volcanic activity. Various volcanic hot spot detection algorithms already exist in the literature. However, every algorithm has its advantages and disadvantages, as they are limited depending on the tradeoffs made during algorithm development, the sensor used for aquisition, and  the geometry of acquisition. Depending on the algorithm used, different results are obtained from the same data and, hence, different interpretations can be made in terms of, e.g., energy emitted, effusion rates, and eruption duration. In the present work, we aim at creating a new hotspot detection algorithm using MODIS and VIIRS imagery, which allows us to efficiently look at the dynamics of thermal emissions coming from persistent lava lakes, i.e., bassins of lava maintained molten through thermal convection and outgassing. We investigate the applicability of sensor fusion ideas, using multiple bands, and incorporating cloud cover information. We expect that by combining all available data the robustness of the detection process will increase.

How to cite: Rolain, S., Peumans, D., and Smets, B.: Thermal remote sensing of lava lakes: a comparison of approaches, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5284, https://doi.org/10.5194/egusphere-egu24-5284, 2024.

EGU24-5555 | Posters on site | GMPV9.1

Application of a low-cost ultraviolet camera solution for permanent sulphur dioxide measurements at six volcanoes worldwide. 

Tom Pering, Thomas Wilkes, Patricia Nadeau, Silvana Hidalgo, Felipe Aguilera, Susana Layana, Nurnaning Aisyah, Hanik Humaida, Alfabi Sakti, and Christoph Kern

Ultraviolet (UV) cameras provide advantages in spatial and temporal resolution for the measurement of sulphur dioxide (SO2) emission rates, when compared to the more common differential optical absorption spectroscopy (DOAS) instruments. Up to this point, however, most instances of UV camera usage are restricted to discrete campaigns, rather than permanent installations. Notable exceptions include Stromboli, Etna, and Kīlauea (2013-2018). The reasons for this are largely related to cost, with commercially available UV cameras often being prohibitively expensive, and also to the challenges associated with developing robust algorithms for automated retrieval of emission rates from the collected imagery. The PiCam, developed at the University of Sheffield, is a new UV camera system designed for permanent installation in the field and provides automatic measurements of SO2 emission rates (for full details see Wilkes et al., 2023, doi: 10.3389/feart.2023.1088992). The PiCam is currently installed at six volcanoes globally: Kīlauea (USA), Cotopaxi and Reventador (Ecuador), Lascar and Lastarria (Chile), and Merapi (Indonesia). Each location has unique requirements and setup, for instance the UV cameras at Reventador and Lastarria operate autonomously but require user visits for data download. Those at Kīlauea and Merapi are integrated within existing telemetry solutions, while at Lascar and Cotopaxi we have begun to integrate Starlink satellite data telemetry alongside our cameras. We present some early results from measurements at Kīlauea where emission rates are compared to more traditional measurements using DOAS. Since the PiCam installation in 2022, the system has recorded multiple styles of activity, from low-level degassing during periods of quiescence to syn-eruptive emissions exceeding 10,000 t/d. Our work highlights continuing challenges of processing of UV camera data, where automated protocols and real-time processing for reliable emission rate retrievals are still in their infancy.

How to cite: Pering, T., Wilkes, T., Nadeau, P., Hidalgo, S., Aguilera, F., Layana, S., Aisyah, N., Humaida, H., Sakti, A., and Kern, C.: Application of a low-cost ultraviolet camera solution for permanent sulphur dioxide measurements at six volcanoes worldwide., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5555, https://doi.org/10.5194/egusphere-egu24-5555, 2024.

EGU24-5632 | ECS | Orals | GMPV9.1

The making of a Volcanic Ash DataBase (VolcAshDB) and its exploitation with machine learning 

Damià Benet, Fidel Costa, Christina Widiwijayanti, John Pallister, Gabriela Pedreros, Patrick Allard, Hanik Humaida, Yosuke Aoki, and Fukashi Maeno

The study of volcanic ash and its different components provides key information that can help understand the likely evolution of volcanic activity during early stages of a crisis and possible transitions towards different eruptive styles. However, classifying ash particles into components such as juvenile or lithic is not straightforward. Diagnostic observations may vary depending on the style of eruption, and there is no standardized methodology, which may lead to ambiguities in assigning a given particle to a given class. To address this problem, we created the web-based Volcanic Ash DataBase (VolcAshDB) which is made of > 6,300 multi-focused binocular images of particles from a range of magma compositions and types of volcanic activity (https://volcash.wovodat.org/). For each particle image, we quantitatively extracted 33 features of shape, texture, and color, and visually classified each particle into one of the four main components: free crystal, altered material, lithic, and juvenile. We used the data in VolcAshDB to setup a variety of machine learning-based models aimed at improving ash particle classification. We identified the features that are discriminant of a given particle type through explanatory AI and the Shapley values from the predictions made by an XGBoost model. We have also developed an accurate Vision Transformer model (93% accuracy) that could be potentially used by volcano observatories to obtain a relatively rapid and objective score on a particle-by-particle basis. Such models could be used for petrologic monitoring in a reproducible and systematic manner aiding in making more informed decisions for hazard mitigation.

How to cite: Benet, D., Costa, F., Widiwijayanti, C., Pallister, J., Pedreros, G., Allard, P., Humaida, H., Aoki, Y., and Maeno, F.: The making of a Volcanic Ash DataBase (VolcAshDB) and its exploitation with machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5632, https://doi.org/10.5194/egusphere-egu24-5632, 2024.

EGU24-8083 | Orals | GMPV9.1 | Highlight

Forty years of geochemical data  at Campi Flegrei hydrothermal system 

Giovanni Chiodini, Stefano Caliro, Carlo Cardellini, Rosario Avino, Giulio Bini, Antonio Carandente, Emilio Cuoco, Carmine Minopoli, Tullio Ricci, Francesco Rufino, Alessandro Santi, Alessandra Sciarra, and Giancarlo Tamburello

The systematic sampling of the main fumaroles of Solfatara (Campi Flegrei, Italy) started during the bradyseismic crisis of 1983-84. In the late 1990s, diffusive CO2 emissions measurements also became part of the monitoring activity through systematic campaigns. In these 40 years of investigations almost unique databases were created including thousands of chemical and isotopic analyses of fumaroles and hundreds estimations of the diffuse CO2 emission. These databases provided the base of numerous geochemical and interdisciplinary scientific works to understand the processes occurring in the hydrothermal-magmatic system of Campi Flegrei, a caldera in unrest since 2005. The main results obtained by this effort indicate the pivotal role of magma degassing in the current crisis of Campi Flegrei. The deep magmatic fluids are injected into the hydrothermal system during episodes of magma degassing. These injections cause pressurization and heating of the hydrothermal systems, earthquakes, ground deformations, changes in fumarole compositions and escalating CO2 emission at the surface. The expulsion of these fluids constitutes the most energetic process currently occurring at Campi Flegrei; it is, in fact, more energetic than ground deformation and seismic activity. In this work, we present a review of these different aspects.

How to cite: Chiodini, G., Caliro, S., Cardellini, C., Avino, R., Bini, G., Carandente, A., Cuoco, E., Minopoli, C., Ricci, T., Rufino, F., Santi, A., Sciarra, A., and Tamburello, G.: Forty years of geochemical data  at Campi Flegrei hydrothermal system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8083, https://doi.org/10.5194/egusphere-egu24-8083, 2024.

EGU24-9052 | ECS | Orals | GMPV9.1

A single band TIR-based algorithm to detect low-to-high thermal anomalies in volcanic regions 

Simone Aveni, Marco Laiolo, Adele Campus, Francesco Massimetti, and Diego Coppola

Volcanic eruptions pose a major threat to at least 800 million people. Studies revealed that ~50% of the ~1400 potentially active subaerial volcanoes still lack conventional ground-based monitoring networks. In this context, satellite data proves to be a cost-effective, yet reliable, information source for detecting early signs of volcanic activity and monitoring the evolution of eruptive events.
Within the past two decades, several moderate resolution (~1 km) Mid-InfraRed (MIR) satellite-based volcano monitoring systems have been developed, mostly targeting high-temperature anomalies associated with eruptive activity. Subtle thermal anomalies, however, might occur from years to days prior major volcanic unrests and/or eruptions, and persist for a long time during the cooling stage of the erupted deposits.
Studies revealed that Thermal InfraRed (TIR) bands, often characterised by higher spatial resolution (< 100 m) but lower revisit time (> 6 days), are well suited to detect subtle thermal anomalies. Yet, even in a high-temperature domain, TIR observations typically prove more effective in accurately determining the dimensions of active and cooling lava flows. Besides, high resolution TIR channels allow the retrieval of more detailed spatial information but with a temporal resolution inadequate for daily monitoring.
Forefront TIR-equipped platforms, however, like the Visible Infrared Imaging Radiometer Suite (VIIRS), offer an unprecedented trade-off between spatial (375 m) and temporal resolution (up to 4 acquisitions of the same target per day), having the potential to provide accurate heat flux measurements before, during and after an eruption. 
Here we present a single-band TIR-based algorithm capable of detecting thermal anomalies in a broad range of volcanic settings, from crater lakes and localised low-temperature hydrothermal systems to high-temperature effusive events. The algorithm – based on temporal and contextual analyses to identify thermally anomalous pixels – can detect thermal anomalies for pixel-integrated temperatures as low as 0.5 K above the surrounding hot-spot-free background and as far as 25 km from the volcano’s summit while maintaining a false positive rate of ~2%.
Results emerging from selected case studies envisage that the system will prove instrumental for detecting early signs of volcanic activity and for monitoring the evolution of thermal emissions, from unrest to eruption. Furthermore, the compilation of statistically robust multidecadal thermal datasets will provide novel insights and new perspectives into volcano monitoring, laying the ground for forthcoming higher-resolution TIR missions.

How to cite: Aveni, S., Laiolo, M., Campus, A., Massimetti, F., and Coppola, D.: A single band TIR-based algorithm to detect low-to-high thermal anomalies in volcanic regions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9052, https://doi.org/10.5194/egusphere-egu24-9052, 2024.

EGU24-9726 | ECS | Orals | GMPV9.1

Innovative approach to investigate seafloor slow vertical deformation using bottom pressure measurements in a volcanic area: Campi Flegrei caldera (Italy) case of study 

Rebecca Sveva Morelli, Rosario Riccio, Sergio Guardato, Stefano Caliro, Francesco Chierici, Giovanni Macedonio, Vincenzo Morra, and Giovanni Iannaccone

Caldera systems generally show complex ground deformation phenomena, mainly associated with variations at different timescales of the hydrothermal systems normally hosted in calderas, magma storage and migration in the volcano plumbing system. Sometimes volcanic calderas are totally or partially submerged, which makes their study challenging, in particular if we consider shallow water systems. 

Many studies demonstrate the efficiency of adopting Bottom Pressure Recorder sensors (BPRs) for monitoring the vertical displacement of volcanic areas in deep-water environments. Moreover, BPRs measure the pressure at the seafloor over time, making possible their use to measure rapid or gradual inflation and deflation events. 

Here we propose an original approach to investigate the seafloor deformation over time in shallow volcanic areas using these instruments, and we applied it at Campi Flegrei caldera (Italy), a high-risk volcano system with a significant portion submerged in the Bay of Pozzuoli, near Naples. In this study we consider the data of two BPRs installed at the seabed within the Multiparametric Elastic-Beacon Devices and Underwater Sensors Acquisition (MEDUSA) infrastructure of the INGV Osservatorio Vesuviano, and we transform pressure measurements in equivalent water level changes to obtain the vertical seafloor displacement. To do this, we need the mean density of the water column during the periods of analysis, so we indirectly calculate it through the use of two tide gauges, one placed in the Gulf of Pozzuoli, and one located outside the deformation area for reference. The final results are then compared with the data acquired by the GPSs installed on the top of MEDUSA buoys, deployed at the same sites of the BPRs. The good correlation obtained supports the reliability of these sensors in measuring the seafloor deformation in a shallow water environment with an unprecedented level of accuracy.

How to cite: Morelli, R. S., Riccio, R., Guardato, S., Caliro, S., Chierici, F., Macedonio, G., Morra, V., and Iannaccone, G.: Innovative approach to investigate seafloor slow vertical deformation using bottom pressure measurements in a volcanic area: Campi Flegrei caldera (Italy) case of study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9726, https://doi.org/10.5194/egusphere-egu24-9726, 2024.

EGU24-10724 | Orals | GMPV9.1 | Highlight

Volume, effusion rates and lava hazards of the 2021, 2022 and 2023 Reykjanes fires: Lessons learned from near real-time photogrammetric monitoring 

Gro B. M. Pedersen, Joaquin M. C. Belart, Birgir V. Óskarsson, Sydney R. Gunnarson, Magnús T. Gudmundsson, Hannah I. Reynolds, Guðmundur Valsson, Thórdís Högnadóttir, Virginie Pinel, Michelle M. Parks, Vincent Drouin, Robert A. Askew, Tobias Dürig, and Ragnar H. Þrastarson

At the time of writing (January 9, 2024) four basaltic effusive eruptions have taken place on the Reykjanes Peninsula, SW Iceland since 2021. This includes three eruptions within the Fagradalsfjall volcanic system (March 19–September 18, 2021; August 3–21, 2022 and July 10–August 5, 2023) and one eruption within the Svartsengi volcanic system (December 18–21, 2023). Near real-time photogrammetric monitoring was performed during all four eruptions and the results yielded eruption parameters such as lava volumes, thicknesses, and effusion rates, which are key for hazard assessments.

 

The 6-month long 2021 Fagradalsfjall eruption produced a bulk lava volume of 150 ± 3 × 106 m3 and the mean output rate (MOR) of 9.5 ± 0.2 m3/s with a fairly constant time-averaged discharge rate ranging between 1–8 m3/s in March–April and increasing to 9–13 m3/s in May–September. The 18 day long eruption in 2022 had a bulk volume of 11 ± 0.4 × 106 m3 with a MOR of ~7 m3/s, starting with a fairly high initial effusion (exceeding 30 m3/s a few hours from the eruption start) followed by an exponential declining phase of waning effusion. The 2023 eruption in the Fagradalsfjall volcanic system lasted 26 days and the effusion rate followed an exponential declining trend like the 2022 eruption with similar MOR of ~7 m3/s and a bulk volume of ~15 × 106 m3. The initial effusion rates observed in these three eruptions were comparable to the calculated inflow rates into the dikes prior to eruption onset, suggesting that the magnitude of effusion can be estimated prior to eruption onset. Furthermore, first order assessments of eruption durations were feasible from the exponentially declining effusion rate curves in 2022 and 2023.

The eruption in the Svartsengi volcanic system yielded a bulk volume of ~11 × 106 m3 with a MOR of ~50 m3/s. The initial effusion rate was likely to have exceeded 300 m3/s and declined rapidly ending after 2.5 days.

Here we discuss the different trends in the effusion rate curves for these four eruptions, what insight they provide regarding plumbing system dynamics, and their implications concerning associated lava hazards.

How to cite: Pedersen, G. B. M., Belart, J. M. C., Óskarsson, B. V., Gunnarson, S. R., Gudmundsson, M. T., Reynolds, H. I., Valsson, G., Högnadóttir, T., Pinel, V., Parks, M. M., Drouin, V., Askew, R. A., Dürig, T., and Þrastarson, R. H.: Volume, effusion rates and lava hazards of the 2021, 2022 and 2023 Reykjanes fires: Lessons learned from near real-time photogrammetric monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10724, https://doi.org/10.5194/egusphere-egu24-10724, 2024.

EGU24-12847 | Orals | GMPV9.1

Developing Earth Observation strategies for Global Volcano Monitoring (G-VEWERS) 

Susanna Ebmeier, Mike Poland, Matthew Pritchard, Juliet Biggs, and Marco Bagnardi

Satellite observations of displacement are critical to any efforts to monitor volcanoes globally given that less than half of world’s potentially active subaerial volcanoes are monitored continuously by ground-based systems.  Thermal, gas and displacement measurements all provide important insights for understanding volcanic processes.  Displacements measured by synthetic aperture radar in particular, are potentially informative in pre-eruptive periods, but remain especially uneven in their geographical coverage.  While this is partially due to variations in sources of uncertainty such as vegetation and atmospheric signals, it is also a consequence of unequal access to data and differences in local capacity to process and analyse it.

The Committee for Earth Observation Satellites Working Group on Disasters Volcano Pilot (2014-2017) and Volcano Demonstrator (2019-2023) projects aimed to illustrated the great potential that satellite data have for detection and forecasting of unrest and eruption.  These programs have played a particular role in connecting volcano observatory scientists to constellation SAR imagery with a diversity of wavelengths, acquisition strategies and data access policies.   This work has had an impact on monitoring decisions at volcanoes, especially in Latin America, but has also resulted in the development of new approaches for integrating and interpreting diverse EO observations and contributed to the development of a strategy for global satellite monitoring of volcanoes.

Here, we describe the aims and early progress of the successor initiative G-VEWERS (Global Volcano Early Warning and Eruption Response from Space). This aims to be a permanent partnership between space agencies, researchers at academic institutions, and volcano observatories, with the goal of coordinating the acquisition, access, and utilization of satellite data to support volcano monitoring and early warning at volcano observatories worldwide.

How to cite: Ebmeier, S., Poland, M., Pritchard, M., Biggs, J., and Bagnardi, M.: Developing Earth Observation strategies for Global Volcano Monitoring (G-VEWERS), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12847, https://doi.org/10.5194/egusphere-egu24-12847, 2024.

Thermal monitoring of volcanic activity has become common over the past 25 years and is well integrated into the set of tools at several volcano observatories. These data are acquired from a range of sensors including permanent ground-stations, less frequent campaign mode deployments from the ground and air, as well as orbital remote sensing. The fundamental ability to forecast a new eruption using orbital TIR data remains aspirational despite decades of data acquisition, modeling, and analysis. In contrast, large-scale thermal change detection is routine and used to rapidly identify a new eruption and monitor its evolution. Sensors with lower spatial (≥ 1 km) and higher temporal (≤ 24 h) resolutions are best suited for acquiring these data and provide near-real time information. Our recent work examines higher spatial, lower temporal resolution low-Earth orbit data to identify precursory thermal eruption signals. Foundational to this is the ability to retrieve accurate subtle (1-2 K) temperature changes, which are easily overlooked using current change detection approaches. Long time series orbital TIR data enable a unique opportunity to quantify these low-level anomalies and small eruption plumes over long periods. Most significant is the finding that the smaller, subtle detections served as precursory signals in ~81% of eruptions. Over the next decade, several high spatial (~ 60 m) resolution orbital sensors are planned that provide near-daily TIR data at every volcano, vastly improving thermal baselines and detection of new activity. One of these, the Surface Biology and Geology (SBG) mission, contains an infrared instrument, which also plans volcano-specific data products that are crucial for accurate daily monitoring of volcanic temperatures and degassing rates. In preparation for the SBG mission’s Volcanic Activity (VA) data product, we have developed a low-cost, ground-based, multi-wavelength TIR sensor known as the MMT-gasCam. NASA has funded a plan to use this instrument to measure small, passive plumes in emission to determine the detection threshold of sulfur dioxide in the TIR, its conversion to sulfate aerosol, and the temperature of the emitted gas/vent in volcanic plumes. Results will help to validate the future VA data product. However, despite the promise of SBG data, the fundamental step-change in orbital volcanology will not come until high-speed orbital data are possible. A proposed hypertemporal TIR mission would acquire these data at sub-minute scales to determine mass and thermal flux rates of gas emissions, eruptive ash plumes, and lava flows. With such a mission, data now acquired by current ground-based cameras will become possible from orbit for the first time.

How to cite: Ramsey, M., Thompson, J., and Smekens, J.-F.: What we need in thermal infrared (TIR) data to forecast volcanic activity: From new ground-based sensors to a rapid-revisit orbital concept, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13558, https://doi.org/10.5194/egusphere-egu24-13558, 2024.

EGU24-14151 | ECS | Orals | GMPV9.1

Forecasting future volcanic activity in long time series orbital infrared data using machine learning 

James Thompson, Michael Ramsey, and Claudia Corradino

Well established baseline data are critical for volcanic change detection and forecasting associated hazards. High resolution thermal infrared (TIR) data captured synoptically over the entire volcanic system and spanning a long time period provide this forecasting capability for many volcanoes around the world. Foundational to these patterns is the subtle (1-2 K) thermal changes, which are easily overlooked using the current lower spatial resolution (1-2 km) TIR data. Therefore, despite decades of spaceborne data acquisition, orbital volcano science still lacks the fundamental ability to forecast a new eruption. Fortunately, several high spatial resolution TIR missions are planned for the coming decade and their data will be crucial to constrain volcanic activity patterns throughout the pre- and post-eruption phases. One of these is the Surface Biology and Geology (SBG) TIR instrument being jointly developed between NASA in the US and ASI in Italy. It is planned to have high spatial (~ 60 m) and much improved temporal (1-3 days) resolutions with the regular production of volcano-specific data products. In preparation for the data from these new missions, we conducted the first study using the entire data record of higher spatial, lower temporal resolution TIR data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor. ASTER data are the most similar to SBG TIR and most critically, ASTER’s twenty-two-year archive presents a unique opportunity to quantify low-level temperature anomalies to establish baseline behavior. We developed a new statistical algorithm to automatically detect the full range of thermal activity and applied it to >5000 ASTER scenes of five volcanoes with well-documented eruptions. Unique to this algorithm is its ability to use both day and night data, account for clouds, and quantify accurate background temperatures by dynamically scaling depending on the anomaly size. Despite the less frequent temporal coverage of ASTER, the results are an improvement over prior studies that used lower spatial resolution data and show that high spatial resolution TIR data are more effective. Most significant was the finding that the smaller, subtle thermal detections served as precursory signals in ~81% of eruptions. These results also create a framework for classifying future eruptive styles and produced a labeled dataset for use with more advanced machine learning (ML) modeling. Using ML trained on the ASTER results, data from a sixth volcano that was not part of the original study were modeled and the thermally-elevated pixels accurately identified. This thermal anomaly detection approach will be incorporated into the SBG data processing stream to produce crucial daily orbital forecasting of the volcanic activity across the world.

How to cite: Thompson, J., Ramsey, M., and Corradino, C.: Forecasting future volcanic activity in long time series orbital infrared data using machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14151, https://doi.org/10.5194/egusphere-egu24-14151, 2024.

EGU24-15372 | ECS | Posters on site | GMPV9.1 | Highlight

Is ERT suited for the continuous monitoring of volcanic systems? A case study during the 2023 unrest of the Reykjanes system. 

Lore Vanhooren, Thomas Hermans, and Corentin Caudron

Geo-electric methods such as Electrical Resistivity Tomography (ERT) and Induced Polarization (IP) have become increasingly important in the characterization of volcanic and geothermal systems. The methods rely on the electrical properties of the subsurface. In volcanic settings, the main influences are temperature, gas content (i.e. saturation), mineralizations, and the presence of alteration clays.

The ERupT project aims to assess the suitability of ERT to visualize the dynamics in hydrothermal systems. With the long-term aim of improving hazard assessment associated with phreatic/hydrothermal eruptions. In that context, a semi-permanent ERT setup was installed at the Reykjanes geothermal area in Iceland. In October 2022, the monitoring system was installed on-site, automatically measuring one profile per day, with currently 15 months of uninterrupted data, except for 5 days due to technical issues. The profile is 355 meters long and has a depth of investigation of 30 to 50 meters.

The 2021 eruption at Fagradalsfjall has marked a new age of volcanism in the Reykjanes peninsula, 2023 was marked by two eruptions. The first eruption happened in the Fagradalsfjall system on July 10th. The second eruption started on 18 December, North of Grindavik, in the Svartsengi system. The eruption sites are located at respectively 30 and 10 km from the field site. Although the ERT system is located at a considerable distance from the eruption sites and the investigation depth is quite shallow, we observed signals possibly related to both eruptions and accompanying unrest, manifesting as a significant increase in resistance (figure1).

The first peak in resistance happened between 19 and 26 June with an increase of more than 100%, shortly after that, the Fagradalsfjall system erupted. A second peak is observed at the end of August, here the increase happens slowly, as opposed to the sudden peak in June, with a steady increase starting on August 8th, reaching a peak on August 30th. Contradictory to the first example, no immediate eruption occurred after this second peak.

In this context, an increase in resistance is likely caused by a drop in saturation due to high gas levels, which can be caused by magma degassing during the uprise. This raises the question of the time difference between the peaks and the subsequent eruptions, possible factors are the difference in morphological context (sill vs dyke intrusion) and preferential flowpaths relative to our monitoring site.  It should also be noted that this behavior is not observed in all data points, hence advanced processing is needed combined with interpretation using data from other methods. Tremor and soil temperature data are available along the ERT profile, together with one C02 sensor in the center of the profile.

To our knowledge, this is the first time that ERT has been used for daily monitoring of a volcanic system. With joint interpretation to deduce the signal origin, we believe that ERT can be a valuable addition to volcanic monitoring networks.

Figure 1: Resistance evolution in one measurement point, eruptions are indicated by the red lines.

How to cite: Vanhooren, L., Hermans, T., and Caudron, C.: Is ERT suited for the continuous monitoring of volcanic systems? A case study during the 2023 unrest of the Reykjanes system., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15372, https://doi.org/10.5194/egusphere-egu24-15372, 2024.

EGU24-15675 | Orals | GMPV9.1

Detection of deep volcanic tremor sources during the 2021 Tajogaite eruption (La Palma, Canary Islands) 

Luca D'Auria, José Barrancos, Alberto Falcón García, David Martínez van Dorth, Víctor Ortega Ramos, Germán D. Padilla, Javier Preciado-Garbayo, and Nemesio M. Pérez

In recent years, the use of Distributed Acoustic Sensing (DAS) in seismology has gained extensive usage in different applications. A High-Fidelity DAS system (HDAS) was deployed during the 2021 Tajogaite eruption on Cumbre Volcano (La Palma, Canary Islands), allowing the recording of most of the syn-eruptive and post-eruptive seismicity. The eruption lasted from Sep. 19th until Dec. 13th of 2021. The HDAS was installed on Oct. 19th and is still operating.

The HDAS was installed around 10 km from the eruptive vent and was connected to a submarine fibre optic cable directed toward Tenerife Island. Since then, the HDAS has been recording seismic with a temporal sampling rate of 100 Hz and a spatial sampling rate of 10m for a total length of 30 (first phase) and 50 km using Raman Amplification (last period).

The HDAS recorded thousands of local earthquakes as well as regional and teleseism events. It was revealed to be an excellent tool for volcanic monitoring, allowing a better location of deeper events, whose location was made difficult by the small aperture of the seismic network of La Palma.

The HDAS was also able to record the low-frequency (<1 Hz) component of the volcanic tremor up to a distance of tens of kilometres from the volcano. We show how using array-like techniques (MUSIC and Beamforming), it is possible to identify and separate the volcanic tremor signals from the oceanic ambient noise and characterize its source. In particular, this analysis revealed a complex wavefield consisting mostly of surface waves. The array analysis shows that, apart from the ballistic arrivals of surface waves radiated by the eruptive vents, the wavefield contains arrivals related to the scattering from topographic features of the island and its surroundings. Furthermore, it revealed that, apart from surface waves, the wavefield contains arrivals compatible with body waves radiated by deeper sources. We interpret these sources as the effect of the resonance of the volcanic tremor caused by the flow of magma within the system of feeder dikes. 

This work demonstrates the effectiveness of using DAS as a real-time volcano monitoring tool.

How to cite: D'Auria, L., Barrancos, J., Falcón García, A., Martínez van Dorth, D., Ortega Ramos, V., Padilla, G. D., Preciado-Garbayo, J., and Pérez, N. M.: Detection of deep volcanic tremor sources during the 2021 Tajogaite eruption (La Palma, Canary Islands), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15675, https://doi.org/10.5194/egusphere-egu24-15675, 2024.

EGU24-16876 | ECS | Posters on site | GMPV9.1

Tephra comminution by vehicles and resuspension of volcanic ash: impact on ambient air quality in urban areas 

Ines Tomašek, Pierre-Yves Tournigand, Daniele Andronico, Julia Eychenne, Claire Horwell, Ulrich Kueppers, Jacopo Taddeucci, Philippe Claeys, and Matthieu Kervyn

Tephra fallout is a common feature of different styles of eruptions and is the most widespread of volcanic hazards. Fallouts containing substantial amounts of fine-grained particles pose a concern for human health since exposure to respirable PM (sub-10 μm, i.e., PM10) is associated with adverse health effects. The products of effusive or poorly explosive events (e.g., lava fountains, strombolian eruptions) and their impacts are less researched as they typically generate rather coarse-grained deposits. Yet, reworking of tephra deposits by wind, traffic or other human activities can potentially alter the initial grain size distribution of a deposit and generate finer material. Remobilisation of such reworked deposits can affect ambient air quality (i.e., PM10 levels), thus leading to an increased exposure hazard.

In this study, we conducted in situ experiments on the slopes of Etna volcano, Italy, which frequently covers neighbouring urban areas with coarse-grained basaltic tephra. We aimed to understand the changes in tephra grain size distribution and airborne PM10 concentration associated with vehicular activity. For this purpose, we drove a small SUV-type car over an area of a road that we covered with tephra, and investigated the outcomes as a function of 1) the number of car passages (between 10 and 70), 2) the starting thickness of the tephra deposit (between 2 and 10 mm) and 3) vehicle speed (between 20 and 50 km/h). The results show that the grain size of the original tephra deposit decreases with the number of car passages, most notably with higher vehicle velocity (50 km/h) and increasing deposit thickness. Airborne PM10 increased with a higher number of car passages, but also with increased tephra thickness and increased vehicle speed. Our observations have important implications for the management of tephra fallouts in urban areas. We have shown that vehicles will change the grain size distribution of basaltic ash by comminution so local communities can expect that, after an eruption, concentrations of PM10 may increase with time and affect exposures close to roads.

How to cite: Tomašek, I., Tournigand, P.-Y., Andronico, D., Eychenne, J., Horwell, C., Kueppers, U., Taddeucci, J., Claeys, P., and Kervyn, M.: Tephra comminution by vehicles and resuspension of volcanic ash: impact on ambient air quality in urban areas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16876, https://doi.org/10.5194/egusphere-egu24-16876, 2024.

EGU24-18729 | ECS | Posters on site | GMPV9.1

On the occurrence of volcanic lightning during vulcanian eruptions at Sakurajima volcano, Japan 

Andre Geisler, Matthias Hort, Sonja Behnke, Harald Edens, Taishi Yamada, Masato Iguchi, and Haruhisa Nakamichi

Volcanic eruptions are enigmatic, not in the least because of volcanic lightning during eruptions, which is still not fully understood. In an effort to better constrain conditions under which electrical discharges occur, we use data from a multicomponent geophysical network installed in 2019 at Sakurajima volcano, Japan. The network includes one vertically scanning Doppler radar to resolve the internal structure of the eruption column at a low temporal resolution, and two fixed Doppler radar systems to resolve the dynamics of the eruption near the vent at high temporal resolution. Eruption onset times were determined using a total of 5 infrasound stations. Electrical discharges were detected by three electric field mills (EFM), a thunderstorm detector from Biral (BTD), a lightning mapping array sensor (LMA) as well as a fast antenna (FA). In addition, meteorological conditions are monitored by a local weather station and eruptions were recorded by two different cameras.

 

Sakurajima volcano is known to exhibit frequent complex eruptions/explosions often exhibiting a sequence of single pulses at intervals down to a few minutes. From our network, we generated an eruption catalog spanning 7 months of activity between June and Dec 2019. Out of this catalog, we select representative examples of multiple pulse events of different strength in terms of erupted mass, plume height, and eruption velocities. For each pulse within such a sequence, we analyzed the electrical activity as well as extracted eruption velocities, eruption volumes, plume heights, and eruption onsets among others. We find that the timing of the electrical discharges is correlated with the onsets of single pulses within a sequence. Furthermore, we can detect changes in the electrical activity ranging from times of CRF signals from small streamer discharges up to volcanic lightning while being able to track the erupted mass and plume extend at the same time. While electrical activity can increase together with eruptive strength, we also observe quite “strong” eruptions with little detectable discharges. On the other hand, less energetic eruptions are observed to produce electrical discharges, especially when the plume of a pulse rises through pre-existing ash clouds in the crater region.

How to cite: Geisler, A., Hort, M., Behnke, S., Edens, H., Yamada, T., Iguchi, M., and Nakamichi, H.: On the occurrence of volcanic lightning during vulcanian eruptions at Sakurajima volcano, Japan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18729, https://doi.org/10.5194/egusphere-egu24-18729, 2024.

EGU24-19253 | Posters on site | GMPV9.1

Vulcano International training Summer School of Geochemistry  

Giovannella Pecoraino, Franco Tassi, Sergio Calabrese, Jacopo Cabassi, Orlando Vaselli, Dmitri Rouwet, Giancarlo Tamburello, Francesco Capecchiacci, and Stefania Venturi

Vulcano Island, an active closed conduit volcano in south Sicily, hosts from 2018 the Vulcano International Training Summer School of Geochemistry. The basic idea is to share scientific knowledge and experiences in a multi-aspect geochemical community, using local resources with a low-cost organization in order to allow as many students as possible access to the school. The Vulcano International Training Summer School of Geochemistry is addressed to students, graduate students, senior graduate students and  fellows, coming not only from Italy but also from European and non-European countries, aiming to bring together the next generation of researchers active in studies concerning the geochemistry and the budget of volcanic gases. The main aim of the school is to bring the next generation of researchers, active in studies concerning geochemistry in volcanic environments, and to introduce them with innovative direct sampling and remote sensing techniques. Furthermore, it gives young scientists an opportunity to experiment and evaluate new protocols and techniques to be used on volcanic fluid emissions, covering a broad variety of methods. The teaching approach includes practical demonstrations and field applications, conducted by teachers of international level. Students therefore have the opportunity to learn by practicing sampling techniques. Practical exercises include: direct sampling of high-temperature fumaroles and plume measurement techniques in the fumarolic crater field; direct sampling of low-temperature gas emissions and submarine emissions; measurement of diffuse soil gas fluxes of endogenous gases at Levante Bay Beach; sampling of groundwater and dissolved gases, and measurements of physical-chemical parameters by using multiparametric probes, in thermal waters in the Vulcano village. Also this year the school will take place from 17 to 21 June 2024.

How to cite: Pecoraino, G., Tassi, F., Calabrese, S., Cabassi, J., Vaselli, O., Rouwet, D., Tamburello, G., Capecchiacci, F., and Venturi, S.: Vulcano International training Summer School of Geochemistry , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19253, https://doi.org/10.5194/egusphere-egu24-19253, 2024.

EGU24-19259 | Posters on site | GMPV9.1

Unveiling magma dynamics behind geochemical data 

Alessandro La Spina, Mike Burton, Pietro Bonfanti, and Filippo Murè

Identifying changes on volcano unrest condition and tracking the evolution of eruptive activity are fundamental for volcanic surveillance and monitoring. Under this perspective, magmatic gases play a key role; therefore, monitoring changes in volcanic plume composition is essential.

Between and during each eruption large systematic variations in the volcanic plume composition can be observed on Mt. Etna. Specifically, gas emissions implicitly contain critical information on the state of the volcano in terms of magma dynamics in the plumbing system.

New technologies have improved the ability to identify gas emissions through remote sensing. Since March 2000, the remote sensing group of INGV-OE Catania has regularly measured the volcanic gas in the plume emitted from Mt. Etna by solar occultation FTIR on average 2-3 acquisitions per week. These measurements allow to quantify the column amounts of SO2, HCl and HF in the path between the instrument and the Sun, and obtain SO2/HCl, HCl/HF and SO2/HF ratios

Extracting meaningful information and gaining new insights from 23 years data collection is a challenging task. Here, we perform a data driven investigation exploiting the relationships between volcanic activity and volcanic gas emissions from 2000 to 2023 period. A general decrease in SO2/HCl ratio, due to an increase in the halogens emission rate (HCl and HF), is observed during eruptions that results closely connected with the central conduit of Etna (e.g. 2004 and 2008).This evidence suggests that magma residence time is required to sustain an efficient halogen degassing via summit craters and the lava flow draining gradually led to a break in the magma convective overturn within a shallow reservoir. Whereas, eruptions not connected with the central conduit of Etna (e.g. 2002-03) are preceded by several weeks of elevated SO2/HCl ratio, produced by a relative reduction in HCl emission consistent with inefficient magma circulation that partially inhibits ascent of magma thought the central conduit of Etna enhances the probability of lateral eruptions.

How to cite: La Spina, A., Burton, M., Bonfanti, P., and Murè, F.: Unveiling magma dynamics behind geochemical data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19259, https://doi.org/10.5194/egusphere-egu24-19259, 2024.

EGU24-20991 | ECS | Orals | GMPV9.1

Measuring the full strain tensor using a low-cost optical borehole strainmeter 

Martin Foin, Jean Chéry, Han Cheng Seat, Michel Cattoen, Michel Peyret, and Sandrine Baudin

Monitoring volcanic deformation is crucial for understanding eruptive activities and associated hazards. While various surface deformation measurement tools like GPS, INSAR and tiltmeters are widely used on volcanoes, strainmeters offer unique means to detect volcanic transient phenomena, deformation source location and dynamics (Bagagli et al., 2017; Bonaccorso et al., 2023), including the categorization of phenomena (Carleo et al., 2023). However, their widespread use has been hindered by cost considerations and the challenges associated with on-field calibration. Additionally, strainmeters are recording deformation from shallow water levels, body tides, pressure changes and snowfall, that makes difficult the separation among the involved processes.

To address these challenges, we propose a novel, moderate-cost, high-resolution borehole strainmeter based on optical measurement. Strain is quantified by measuring the diameter change of a sphere using optical interferometry (Seat et al. 2012), providing a 10-10 strain resolution across a broadband [0; 2.5] kHz range. This innovative strainmeter (Chery 2021, patent FR2106959) features six uniaxial strain gauges anchored inside a concrete spherical shell, enabling the reconstruction of the six components of the 3D strain tensor. The full measurement of the strain tensor should enhance our understanding of deformation dynamics both at borehole vicinity and in the far-field. Indeed, the knowledge of the full straintensor should allow the differentiation between near-field and far-field perturbations due to the distinct nature of their strain perturbation in time and space.

A seventh measurement gauge, free of shell deformation, facilitates the filtering of physical variations associated to laser wavelength, temperature and air pressure. To ensure accuracy and reliability of the strainmeter, an in-situ calibration system involving sphere pressurization is integrated. This innovative feature should help to determine borehole heterogeneity and to minimize long term drift.

In November 2023, a first strainmeter prototype has been successfully installed on the Larzac Plateau (France) at the multi-instrument observatory (OSU OREME and H+/OZCAR network). We will present first results of the instrument and will discuss the future perspectives.

How to cite: Foin, M., Chéry, J., Seat, H. C., Cattoen, M., Peyret, M., and Baudin, S.: Measuring the full strain tensor using a low-cost optical borehole strainmeter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20991, https://doi.org/10.5194/egusphere-egu24-20991, 2024.

EGU24-21214 | Posters on site | GMPV9.1

Detecting volcanic lightning with different methods: a comparison 

Matthias Hort, Andre Geisler, Fransizska Heck, Sonja Behnke, Herald Edens, and Masato Iguchi

The origin of volcanic lightning is still a matter of intense research because it may complement other monitoring techniques in detecting volcanic eruptions at remote or not well monitored volcanoes. Various methods have been used to detect electrical discharges over the last decades and here we compare four different methods for the detection of electrical discharges which were operated in late 2019 at Sakurajima volcano. The electrical activity was observed by an electric field mill (EFM, which measures the static electrical field at 10 S/s (samples/second)), a thunderstorm detector from Biral (BTD, also measures the static electrical field at 100 S/s), as well as a lightning mapping array station (LMA, measuring VHF electromagnetic radiation) and a fast antenna FA (time constant τ = 10-4 s⁻¹, 180MS/s). We developed special algorithms to identify electrical discharges in the EFM and BTD data sets because those were the most continuous data sets available to us. From a period of high volcanic activity during which also data from the other instruments were available, we then picked several eruptions characterized by different types of electrical discharges. We analyzed the number of discharges detected by each instrument as well as how well the amplitudes (electrical field changes) are resolved by the different instruments. We find good correlations of detected signal strength between the FA and EFM data, the correlation between these data and the BTD is especially for larger events not as perfect. In order to analyze this problem, we use the FA measurements to downsample and synthetically reconstruct the BTD data set, showing deviations for larger amplitudes as well. Overall, the instruments show good agreement on detecting electrical discharges within volcanic eruptions with differences on the detection of „assumable weaker“ signals. We highlight the advantages and disadvantages of the different techniques in terms of detecting electrical discharges during volcanic eruptions. We finish discussing how the different instruments can be used to determine electric field changes as well as further investigate the type of electrical discharges detected.

How to cite: Hort, M., Geisler, A., Heck, F., Behnke, S., Edens, H., and Iguchi, M.: Detecting volcanic lightning with different methods: a comparison, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21214, https://doi.org/10.5194/egusphere-egu24-21214, 2024.

EGU24-1642 | ECS | Orals | GMPV9.5

Hydroacoustic monitoring of submarine lava flows: the eruption of Fani Maoré volcano offshore Mayotte, Indian Ocean 

Aude Lavayssière, Sara Bazin, Pierre-Yves Raumer, and Jean-Yves Royer

With the vast majority of our planet volcanism occurring in the Oceans, moored networks of hydrophones have become efficient tools to monitor, and therefore better understand, underwater volcanic eruptions. As these instruments can record sounds from thousands of kilometers away, they are particularly relevant to detect earthquakes and volcanic eruptions remotely, allowing better geohazards assessment. In 2018, a major seismic and volcanic crisis gave rise to the Fani Maoré underwater volcano at 3500 m below sea level, ~50 km east offshore Mayotte, in the North Mozambique channel. The MAHY hydroacoustic network has been deployed in October 2020 to monitor the eruption and investigate the oceanic soundscape in the area. It consists of four hydrophones moored in the SOFAR channel in the water column around the volcano. Since their deployment, the hydrophones have continuously recorded all low-frequency sounds (0-120 Hz), particularly hundreds of impulsive signals resulting from the interaction between hot lava and cold seawater. An automatic detection method of these specific signals on spectrograms has been developed to investigate in details the spatio-temporal evolution of the new lava flows. This technique could be used worldwide to remotely detect and monitor active submarine eruptions in the absence of local monitoring networks or regular near-bottom seafloor surveys.

How to cite: Lavayssière, A., Bazin, S., Raumer, P.-Y., and Royer, J.-Y.: Hydroacoustic monitoring of submarine lava flows: the eruption of Fani Maoré volcano offshore Mayotte, Indian Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1642, https://doi.org/10.5194/egusphere-egu24-1642, 2024.

EGU24-3639 | ECS | Posters on site | GMPV9.5

Proximal tephra characterization in Northern Victoria Land, Antarctica: Insights into eruptive history and future implications 

Giulia Fisauli, Maurizio Petrelli, Alessio Di Roberto, and Giuseppe Re

We don’t always have direct access to volcanoes especially those located in hostile and remote areas of our planet, such as Antarctica. Moreover, the knowledge of the Antarctic continent and its volcanoes is still limited by the scarce exposure of volcanic rocks due to the extensive glacial cover, since only 1% of the total area is ice-free. Pyroclastic deposits (i.e. tephra) represent a very effective and powerful tool for petrological and volcanological studies. Through the study and characterization of tephra we can get information about the evolution of magmas, including their physical, chemical and mineralogical characteristics. Additionally, we can get a new understanding of the architecture of volcanic plumbing systems, the nature and intensity of eruptions as well as the emplacement dynamics, their aerial transportation and their impacts on Earth. This work focuses on the characterization of tephra originating from three distinct volcanoes of the Northern Victoria Land, Mount Melbourne, Mount Rittmann and The Pleiades.

According to previous studies, the activity of Mount Melbourne can be dated back to approximately 1892 CE, this is also confirmed by the presence of several tephra layers in the summit and flanks of the volcano (Lyon, 1986). Evidence for explosive eruptions of Mount Melbourne volcano between 1615 cal. yrs BP and 1677 cal. yrs BP were recently acquired (Di Roberto et al. 2023). Also, Mount Rittmann erupted in historical time (696 ± 2 cal. yrs BP) and the presence of fumaroles and summit geothermal activity indicate that the volcano is still active. However, we still know very little about the volcanic history of this volcano. The Pleiades volcanoes instead show evidence of activity during the Holocene (Di Roberto et al. 2020).

Despite the abundance of rock samples collected in this area, there is still a scarcity of both geochemical and petrological data and studies.

We analysed 23 samples that have been collected over the last 30 years during Antarctic expeditions. The analyzed data will provide a more detailed understanding of past explosive volcanic activity including source, magnitude, intensity, chemical evolution and eruptive dynamics. Finally, this will also improve the correlation between proximal and distal tephra.

In addition, an extensive database containing major and trace elements is crucial for a precise geochemical characterization to provide invaluable insights to enhance our understanding of the Northern Victoria Land.

The comprehension of Antarctic volcanism is crucial not only to understand the eruptive dynamics and plumbing system but also to build new knowledge of the history of explosive volcanic activity through time and space. This understanding is critical in evaluating and defining potential impacts associated with future eruptions, which could potentially be affected by ice dynamics and ice load covering the volcanic structures, with wider implications for our planet.

 

Lyon, G.L., 1986. Doi: 10.1080/00288306.1986.10427528.

Di Roberto et al. 2020. Doi: 10.1016/j.quascirev.2020.106629

Di Roberto et l. 2023. Doi: 10.1016/j.qsa.2023.100079

 

How to cite: Fisauli, G., Petrelli, M., Di Roberto, A., and Re, G.: Proximal tephra characterization in Northern Victoria Land, Antarctica: Insights into eruptive history and future implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3639, https://doi.org/10.5194/egusphere-egu24-3639, 2024.

EGU24-3878 | ECS | Posters on site | GMPV9.5

Enhancing Geo-electric Exploration using Thermal Remote Sensing and Dual Band Processing – Case Study of the Stromboli Volcano (Aeolian Islands) 

Flavio Manara, Marceau Gresse, André Revil, Anthony Finizola, and Tullio Ricci

Geo-electric exploration surveys such as Electrical Resistivity Tomography (ERT) can provide valuable insights regarding the characterization of geological structures and hydrothermal systems in volcanic environments. However, while ERT is a powerful tool, its effectiveness can be limited by the inherent sensitivity of rock electrical conductivity to various parameters. These can include factors such as water content, salinity of pore water, rock temperature, or alteration. Each of these factors significantly impacts the results of an ERT survey and, if not precisely characterized, can lead to inaccurate data interpretation. As a result, ERT is often supplemented by additional costly and time-consuming in-situ measurements, such as soil temperature or diffuse soil CO2 degassing probing, to provide a more comprehensive analysis of subsurface conditions.

The purpose of this study is to summarize the recent geophysical findings from Revil et al. (2023), where they constructed the first 3D electrical conductivity model of the Stromboli volcano in the Aeolian Islands. To build this model, Revil et al. collected and analyzed data from various sources, including self-potential, soil temperature, soil CO2 degassing, and thermal remote sensing maps. By comparing these complementary datasets, this study aims to highlight the benefits of using Thermal Remote Sensing as a supplementary tool to analyze data from subsurface geo-electric exploration. Thermal remote sensing constitutes a practical and cost-efficient approach, allowing for systematic monitoring of Earth’s surface thermal anomalies via infrared imaging down to a spatial resolution of 30 to 15 meters.  By applying corrections and isolating surface-emitted radiance from the integrated signature received by the satellite, the average temperature of the surface is retrieved for each pixel. Thermal anomalies on the volcano are then located, and their temperatures are accurately determined through dual-band processing, which involves comparing images from Thermal Infrared and Short-Wave Infrared spectra.

The maximum remotely recorded infrared temperature is 792°C, associated with the main active volcanic vents. Considering the extreme heterogeneity in surface temperature at the scale of the pixel as well as the presence of volcanic gases, uncertainties for the remotely acquired temperature are in the range of a few degrees centigrade. The soil temperature measurements near these vents, retrieved at a depth of 30 cm, also reveal significant internal activity with temperature values reaching 100°C (the readings were taken to a tenth of a degree). This high-temperature region perfectly matches the positive anomalies of self-potential and diffuse soil CO2 degassing associated with the vertical conductive channel (1 to 10-1 S/m).

In conclusion, the ability to isolate the temperature associated with the thermally active component makes this approach highly promising for accurately constraining the spatial distribution of the shallow hydrothermal system, as it is manifested at the surface by high-temperature areas. Therefore, thermal remote sensing appears very useful in refining the interpretation of subsurface geophysical images.

How to cite: Manara, F., Gresse, M., Revil, A., Finizola, A., and Ricci, T.: Enhancing Geo-electric Exploration using Thermal Remote Sensing and Dual Band Processing – Case Study of the Stromboli Volcano (Aeolian Islands), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3878, https://doi.org/10.5194/egusphere-egu24-3878, 2024.

EGU24-4441 | Orals | GMPV9.5 | Highlight

Towards scientific forecasting of magmatic eruptions 

Valerio Acocella, Maurizio Ripepe, Eleonora Rivalta, Aline Peltier, Federico Galetto, and Erouscilla Joseph

Forecasting eruptions is a fundamental goal of volcanology. However,
difficulties in identifying eruptive precursors, fragmented approaches
and lack of resources make eruption forecasting difficult to achieve.
In this Review, we explore the first-order scientific approaches that
are essential to progress towards forecasting the time and location of
magmatic eruptions. Forecasting in time uses different monitoring
techniques, depending on the conduit-opening mode. Ascending
magma can create a new conduit (closed-conduit eruptions), use
a previously open conduit (open-conduit eruptions) or flow below a
solidified magma plug (semi-open-conduit eruptions). Closed-conduit
eruptions provide stronger monitoring signals often detected months
in advance, but they commonly occur at volcanoes with poorly
known pre-eruptive behaviour. Open-conduit eruptions, associated
with low-viscosity magmas, provide more subtle signals often
detected only minutes in advance, although their higher eruption
frequency promotes more testable approaches. Semi-open-conduit
eruptions show intermediate behaviours, potentially displaying clear
pre-eruptive signals days in advance and often recurring repeatedly.
However, any given volcano can experience multiple conduit-opening
modes, sometimes simultaneously, requiring combinations of
forecasting approaches. Forecasting the location of vent opening
relies on determining the stresses controlling magma propagation,
deformation and seismic monitoring. The use of physics-based models
to assimilate monitoring data and observations will substantially
improve forecasting, but requires a deeper understanding of
pre-eruptive processes and more extensive monitoring data.

 

How to cite: Acocella, V., Ripepe, M., Rivalta, E., Peltier, A., Galetto, F., and Joseph, E.: Towards scientific forecasting of magmatic eruptions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4441, https://doi.org/10.5194/egusphere-egu24-4441, 2024.

EGU24-4989 | Posters on site | GMPV9.5

THERESA project: a study to enhance algorithms for processing data from the SBG-TIR mission in volcanological field 

Malvina Silvestri, Maria Fabrizia Buongiorno, and Vito Romaniello

The THERESA project, which stands for THErmal infRarEd SBG Algorithms, seeks to improve algorithms for processing data obtained from the SBG-TIR (Surface Biology and Geology – Thermal InfraRed) mission. By leveraging the mission's technical features, THERESA aims to improve and adapt specific algorithms to study geological processes and develop new ones that could get advantages by using SBG-TIR spectral channels in the VIS and MIR-TIR range. Over the two-year duration of the project, THERESA will play a vital role in advancing the study of terrestrial phenomena also considering the high revisit time of SBG, which will be of 3 days worldwide over land.

SBG-TIR data will benefit diverse thematic areas, ranging from vegetation analysis to monitoring volcanic eruptions and fires. The project aims to derive several key parameters, including the estimation of ash and SO2 emissions from volcanoes, surface temperature, detection of hotspots, and the calculation of FRP (Fire Radiative Power) during High Temperature Events (HTEs). THERESA distinguishes itself through its innovative algorithmic advancements, providing comprehensive support to the SBG-TIR mission. Finally, suitable sites for CAL/VAL activities will be identified, and measurement campaigns will be conducted coinciding with the passages of currently operational TIR satellites for the validation of the algorithms under study.

How to cite: Silvestri, M., Buongiorno, M. F., and Romaniello, V.: THERESA project: a study to enhance algorithms for processing data from the SBG-TIR mission in volcanological field, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4989, https://doi.org/10.5194/egusphere-egu24-4989, 2024.

Volcanic risks cannot be stopped or eliminated, but their effects can be minimized by applying new methods and providing data to support decision-making processes. Etna is one of the most active volcanoes in the world, producing both effusive and explosive eruptions, together with very intense seismic activity, which significantly influence the territory and society. The PANACEA project intends to address some issues that are still open in the modeling and integration of risks deriving from seismic and volcanic hazards, in order not to be caught unprepared and implement proactive risk reduction policies. In particular, the project has focused on the: (i) classification and statistical analysis of the historical eruptions of Etna; (ii) revision of the historical earthquake catalogue and the related database of macroseismic intensities; (iii) assessment of the long-term probability of vent opening based on historical eruptions and seismicity; (iv) extraction of the input parameters to run numerical simulations; (v) physics-based modeling of complex geophysical flows; (vi) probabilistic hazard mapping for single eruptive products, i.e. lava, tephra fallout and PDCs; (vii) probabilistic seismic hazard assessment; (viii) harmonization of the different hazards in a single long-term hazard map; (ix) analysis of the possible interactions at the hazard and the vulnerability levels, in order to quantitatively update hazard and risk estimations; (x) exposure and vulnerability assessment of elements at risk; (xi) multi-risk analysis by combining multi-hazards, exposure and vulnerability assessment. The results of PANACEA demonstrate that a better understanding of geophysical flow mechanisms, as well as improvements in knowledge in volcanic and seismic multi-hazard and multi-risk assessment, both in conceptual and technological terms, provide a powerful tool to develop effective and operational strategies, improving safety and reducing the impact of Etna's eruptive events.

How to cite: Cappello, A. and the PANACEA team: The PANACEA project: Probabilistic AssessmeNt of volCano-related multi-hazard and multi-risk at Mount EtnA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5354, https://doi.org/10.5194/egusphere-egu24-5354, 2024.

EGU24-5710 | ECS | Orals | GMPV9.5

Electromagnetic monitoring of active volcanic zones: Monitoring of Phase Tensor parameters from Mount St Helens and Stromboli volcanoes 

Gokhan Karcioglu, Graham Hill, Max Moorkamp, Yann Avram, Colin Hogg, Sophia Gahr, Katharina Maetschke, Adam Schultz, Esteban Bowles-Martinez, Jared Peacock, Chaojian Chen, Corrado Cimarelli, Luca Caricchi, Yasuo Ogawa, and Duygu Kiyan

The main goal of volcano monitoring is to understand processes occurring within the magmatic system from there geophysical response signatures that informs on the eruptive behavior of the system. Traditional volcano monitoring approaches have relied primarily on changes in seismicity, and geodetic response which depend on active changes such as magma migration.

The magnetotelluric method, informs the physical property electrical conductivity, which within a magmatic context is sensitive to the presence of fluids, temperature, and melt fraction. High quality magnetotelluric measurements allow identification of conductivity variations related to the physical changes in magmatic systems, making it possible to determine temporal changes in magma content and temperature. Thus, magnetotellurics may be a valuable additional monitoring tool able to detect static phase changes of the magmatic fluids within the system, contributing to our understanding of the dynamics occurring within magmatic systems absent of and/or preceding magma movement within the system.

Mount St Helens as perhaps the most studied volcanic system including a dense 3D MT data set collected during the 2004-2008 dome building eruption provides the opportunity to investigate the difference within the magmatic system in different eruptive states (i.e. eruptive 2004-2008 and current quiescence). This is been achieved by a complete repeat of the initial survey (67 sounding locations) collected in 2005-06 and establishment of 4 ‘continuous’ telemetered systems. Given the current non-eruptive state of Mount St Helens a second system has been selected, Stromboli, currently in an eruptive cycle for installation of 4 continuous telemetered MT systems. Stromboli volcano, maintains a persistent eruptive activity, with near daily minor explosions typically punctuated by 1-2 larger events a year.

Initial evaluation of the streamed measurements has been completed using Phase Tensor parameters, which are immune to galvanic distortions, which can occur from seasonal near-surface conductivity changes (e.g. variations in soil moisture content). The Phase Tensor represents conductivity gradients in the subsurface, and Phase Tensor differences between two measurement times hence reflects the changes in conductivity structure in time. The temporal application of magnetotellurics provides a mechanism to determine short-term and long-term conductivity changes within the magmatic system representative of physical changes within the system, correlatable to active eruptive behavior, properties of the system during periods of quiescence and eruptive phases.

How to cite: Karcioglu, G., Hill, G., Moorkamp, M., Avram, Y., Hogg, C., Gahr, S., Maetschke, K., Schultz, A., Bowles-Martinez, E., Peacock, J., Chen, C., Cimarelli, C., Caricchi, L., Ogawa, Y., and Kiyan, D.: Electromagnetic monitoring of active volcanic zones: Monitoring of Phase Tensor parameters from Mount St Helens and Stromboli volcanoes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5710, https://doi.org/10.5194/egusphere-egu24-5710, 2024.

Short and long-term probabilistic volcano hazard assessments entail the fusion of data from multiple sources with the realisation and subsequent combination of hundreds/thousands of scenarios spanning the range of system uncertainties (model inputs and parameterisations, boundary conditions, etc). Computational workflows are middleware software layers that manage and orchestrate in an automated way the multiple steps and tasks involved in this process, from data acquisition and preparation, to model executions and post-process in centralised (HPC) and/or cloud computing infrastructures. This contribution presents some examples from on-going European projects tackling computational geohazards on HPC/cloud infrastructures. For the short-term hazard assessment, the DT-GEO project (2022-2025, Grant Agreement No 101058129) is implementing a number of workflows conducting precise data-informed early warning systems and hazard assessments by harnessing world-class computational (FENIX, EuroHPC) and data (EPOS) research infrastructures. The volcano-related workflows in DT-GEO include: (i) merging of multi-parametric data from ground-based and remote observation systems (on-site monitoring networks and satellites) with global modelling of magma and rock dynamics and with AI approach; (ii) merging of real-time geostationary satellite observations with the FALL3D model to generate deterministic and ensemble-based probabilistic forecast products; (iii) merging of real-time multi-parametric data from ground-based and remote observation systems with deterministic modelling of lava flow propagation and inundation areas and; (iv) air-quality data and AI in a volcanic gas dispersal forecast context to improve operational Early Warning Systems. On the other hand, the EuroHPC ChEESE Center of Excellence (CoE) is conducting an ensemble-based volcanic dispersal across multiple scales that will lead to the first European tephra hazard map at scale covering, simultaneously, long-range dispersal and short-range fallout telescopically. This will be integrated in the EPOS Volcanic Observations TCS (VO-TCS). All these initiatives liaise, align, and synergise with EPOS and longer-term mission-like initiatives like Destination Earth.

How to cite: Folch, A.: Workflows for volcano hazard assessment in cloud and HPC research infrastructures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6365, https://doi.org/10.5194/egusphere-egu24-6365, 2024.

EGU24-6412 | ECS | Orals | GMPV9.5 | Highlight

Volcanic fire hazard modeling 

Roberto Guardo, Giuseppe Bilotta, Gaetana Ganci, Francesco Zuccarello, Daniele Andronico, and Annalisa Cappello

Numerical models have been extensively explored for simulating forest fire propagation, employing a spectrum of approaches ranging from intricate physical models to simpler graph or cellular automata-based models. These models rely on various input parameters such as humidity, radiant capacity, vegetation flammability, tree types, wind and topography to accurately replicate fire spread. When integrated with Geographic Information Systems (GIS), these models facilitate classifying soil and mapping burnt areas. Despite the progress in forest fire models, a dedicated model for volcanic-induced fires is notably absent. Leveraging our expertise in lava flow hazard modeling, we have introduced a novel numerical model to address the current lack of a specific model for volcanic-induced fires. This model is based on cellular automata to tackle issues related to accessibility, usability, and computational costs inherent in existing applications. Indeed, the increased availability of low-cost, high-performance computing hardware has enhanced the accessibility and cost-effectiveness of cellular automata-based simulations, enabling the simulation of fire propagation under multiple environmental conditions. Our new model is able to generate fire hazard scenarios, providing insights into the likelihood of combustion. We present test cases using Stromboli Island as a case study, as it is an area where volcanic eruptions already caused fires that also contributed to human loss. Our results exhibit good spatial accuracy, with a Brier score of 0.188±0.002 and 0.073±0.001 for the fire spread on July 3, 2019, and May 25, 2022, respectively.

How to cite: Guardo, R., Bilotta, G., Ganci, G., Zuccarello, F., Andronico, D., and Cappello, A.: Volcanic fire hazard modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6412, https://doi.org/10.5194/egusphere-egu24-6412, 2024.

Sheet-like sequences may form in relation to subglacial volcanism. Such sequences are thought to be of two types: Mount Pinafore and Dalsheiði-type. The Mount Pinafore-type presumably forms under thin ice cover or some 150-200 m, whereas the Dalsheiði-type is thought to form under much thicker ice cover or probably ˃ 1000 m. Dalsheiði-type sequences are well known in Iceland and were first described by Walker and Blake for Dalsheiði in SE-Iceland. They assumed the pillows and breccia developed through escape upwards and sideways from the basalt into the overlying glacier or its meltwater. A considerably more widespread Dalsheiði sequence was later mapped by Bergh in the Síða-Fljótshverfi of S-Iceland.

Walker and Blake (1966) mapped the Dalsheiði sequence near the assumed eruptive source by Lambatungnajökull (at 628 m a.s.l.) over a 20 km distance down to heath Dalsheiði (at 200 m a.s.l.). New work by Dalsheiði area has revealed that the sequence is more widespread than previously mapped, extending 5 km further down slope to Þórisdalur, or to 20 m a.s.l. I, the sequence differs drastically from the upper segment in that pillows and breccia are rare but extensive sheet-like units dominate. Here, the sills and pillows are typically nonvesicular and dense. Near the edge of the sequence one sheet is seen to intrude into underlying sedimentary rock as evidenced by “fingered” units where the sill intrudes a hydrothermally altered sediment, a host that presumably had brittle to ductile properties. Most Dalsheiði sequences have a thick hyaloclastite body above a sheet of basalt that presumably intruded the ice/bedrock boundary. The lack of a hyaloclastite body by Þórisdalur and the abundant sill-like intrusive sheets there strongly suggests that the first phase in sheet-like sequence formation are intrusions into the ice sheet/bedrock boundary.

By Þórisdalur the sheets have 1-2 m thick colonade at the base, grade into some 6 m thick entablature fracture part, and at the top a 4-5 m segment with still finer fractures and white secondary minerals. Total absence of vesiculation in the lowest sequence of the Dalsheiði formation by Þórisdalur supports that the intruding magma was confined below thick ice that suppressed magma-water explosivity. The interface sills by Þórisdalur may the best such examples discovered to date and in excellent agreement with the theoretical model proposed by Wilson and Head (2002) for injection of such magma sills at the ice sheet lower base. Furthermore, the dominating sill-like character of the Dalsheiði formation by Þórisdalur and intrusion into underlying sedimentary rock, is in contrast with the Sída formation of S-Iceland where a sill-like unit typically interacts with a thick overlying hyaloclastite unit. At Þórisdalur the hylaoclastite phase is missing suggesting that that pillows, breccias and hyaloclastite form at a later stage on top of the sill, perhaps when a meltwater lense has accumulated there, and that this later stage may not have taken place in Þórisdalur.

How to cite: Helgason, J.: New additions to the Dalsheiði sheet-like formation in Þórisdalur, SE-Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6723, https://doi.org/10.5194/egusphere-egu24-6723, 2024.

EGU24-6999 | Orals | GMPV9.5

Modelling the conditions that may lead to phreatic eruptions, with comparison to Whakaari volcano, New Zealand 

Sophie Pearson-Grant, Jonas Köpping, James Patterson, and Thomas Driesner

Phreatic or steam-driven eruptions are the most common type of volcanic eruption in New Zealand. They are notoriously difficult to forecast and have caused fatalities globally. There are two main conceptual models that have been proposed to lead to phreatic eruptions: a) cracking of a hydrothermal seal that is trapping pressurised fluid, and/or b) an injection of hot magmatic gas interacting with cold groundwater that then flashes to steam resulting in rapid fluid overpressure and overburden failure. Testing these hypotheses can help to determine the subsurface processes and timescales leading to an eruption, a possible key to unlocking phreatic eruption forecasting.

We have created generalised 2D numerical models of heat and fluid flow based on conceptual models of Whakaari/White Island volcano in New Zealand. Using CSMP++, we have explored the conditions that allow a build-up of fluids with sufficient overpressure to cause rock failure and potentially initiate an eruption. Our models simulate a sealed hydrothermal system above a magma reservoir. In some models, there is a high permeability zone linking the two which represents a highly fractured zone inferred from fumarole and degassing locations at Whakaari. A subset of these models also includes low permeability zones on either side of the highly fractured zone, which correspond to inferred regions of hydrothermal alteration.

Model results suggest that the permeability of the rock affects how quickly fluids move, but not the long-term pressure distribution. Our models show pressure increases of more than 5 MPa beneath the hydrothermal seal purely due to magmatic heating of groundwater. However, the timescales are on the order of decades. If low-permeability alteration zones are included which limit lateral flow of fluids, pressure increases by 5 MPa from hydrostatic in less than two years. We are now exploring the effects of adding magmatic fluids as well as heat, and will compare results of these models with field and experimental observations from Whakaari volcano.

How to cite: Pearson-Grant, S., Köpping, J., Patterson, J., and Driesner, T.: Modelling the conditions that may lead to phreatic eruptions, with comparison to Whakaari volcano, New Zealand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6999, https://doi.org/10.5194/egusphere-egu24-6999, 2024.

EGU24-7370 | Posters on site | GMPV9.5

25 years recording of the long-base fluid tiltmeter installed at 2.850 m a.s.l. observatory on Etna volcano 

Salvatore Gambino, Laura Privitera, Alessandro Bonaccorso, Giuseppe Falzone, Giuseppe Laudani, and Angelo Ferro

Etna is a very active volcano with frequent eruptions and it is well controlled through different monitoring techniques. Continuous control of ground deformation is also provided by tilt measurements especially through a network of short-base borehole sensors. Since 1996 this network has been integrated with a long-base fluid tiltmeter installed in two 80 m long tunnels present at the high altitude (2,850 m a.s.l.) volcanological observatory of Pizzi Deneri (PDN) located on the summit area of the volcano. The instrumentation was created with an innovative configuration composed of mercury, free to move along the entire length of 80 m in response to the ground tilt, and laser sensors to measure the changes of the mercury level at the ends of the length where this fluid is positioned. In this study for the first time we present the entire set of 25 years of data (1997-2022) recorded by this instrumentation. During this long time interval, the Etna volcano was characterized by numerous main eruptions due to dyke intrusions. The tilt variations recorded in the short term during the rapid intrusive phases are presented and discussed. These signals contributed to the modeling of eruptive processes, and in particular in the case of the 2002-2003 eruption they contributed to the real-time understanding of the ongoing eruptive phenomenon, supporting the correct hazard assessment. In the medium-long term (years to decades) the signal maintained a trend that cumulated approximately 200 microrads on both components during the entire observation. PDN long term is primarily affected by the dynamics of the marked sliding of the entire eastern sector of the volcano.

How to cite: Gambino, S., Privitera, L., Bonaccorso, A., Falzone, G., Laudani, G., and Ferro, A.: 25 years recording of the long-base fluid tiltmeter installed at 2.850 m a.s.l. observatory on Etna volcano, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7370, https://doi.org/10.5194/egusphere-egu24-7370, 2024.

EGU24-7541 | ECS | Posters on site | GMPV9.5

Matlab Interface for Seismo‐Acoustic aRray Analysis (MISARA) 

Vittorio Minio, Luciano Zuccarello, Silvio De Angelis, Giuseppe Di Grazia, and Gilberto Saccorotti

Volcanic activity generates diverse seismic and acoustic signals that offer valuable insights into the underlying magmatic processes. Contemporary volcano monitoring relies on networks and arrays of seismic and acoustic sensors. The analysis of signals acquired by these instruments necessitates streamlined workflows and specialized software. The high sampling rates, typically exceeding 50 Hz, employed in recording seismic and acoustic waveforms by multi-station networks and dense arrays result in the swift accumulation of substantial data volumes, posing a formidable challenge in establishing efficient data analysis workflows for volcano surveillance.
In this context, we introduce MISARA (Matlab Interface for Seismo-Acoustic aRray Analysis), an open-source MATLAB graphical user interface. MISARA is meticulously crafted to furnish a user-friendly workflow for analyzing seismo-acoustic data in volcanic settings. It incorporates efficient algorithmic implementations of established techniques for seismic and acoustic data analysis, with a focus on supporting the visualization, characterization, detection, and location of volcano seismo-acoustic signals. The intuitive and modular structure of MISARA facilitates swift, semi-automated data inspection and result interpretation, thereby minimizing user effort.
Validation of MISARA involved testing it with seismo-acoustic data recorded at Etna Volcano (Italy) during 2010, 2011, and 2019. The tool is intended for educational and research purposes and is well-suited to aid routine data analysis at volcano observatories. Its open-source nature encourages collaborative development and adaptation, fostering advancements in volcano monitoring and contributing to the broader scientific community.

How to cite: Minio, V., Zuccarello, L., De Angelis, S., Di Grazia, G., and Saccorotti, G.: Matlab Interface for Seismo‐Acoustic aRray Analysis (MISARA), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7541, https://doi.org/10.5194/egusphere-egu24-7541, 2024.

EGU24-7815 | ECS | Orals | GMPV9.5

Exploiting satellite techniques for volcanic deposits mapping: the case of 2021 Mt. Etna eruptions 

Maddalena Dozzo, Federico Lucchi, and Simona Scollo

During explosive eruptions tephra fallout represents one of the main volcanic hazards and can be extremely dangerous for air traffic, infrastructures, agriculture, and human health.

The technological advancements and increasing availability of high-resolution satellite imagery have offered new possibilities for mapping volcanic deposits related to an individual eruptive event. Spatial resolution is one of the main limitations in deposit mapping, together with the revisit time of satellites, particularly in rapidly evolving situations.

Here we present a new technique aimed at identifying the urban areas covered by tephra after an explosive event based on the processing of PlanetScope satellite imagery. These recent multispectral data are acquired from a constellation of over 180 microsatellites and exhibits a relatively high spatial resolution (~ 3 m pixel size) covering once a day each point in the Earth surface.

Our technique is based on the introduction of a new index that we call ‘Tephra Fallout Index (TFI)’ computed from the mean reflectance values of the near infrared (NIR) band analyzing pre- and post-eruptive data in paved areas adjacent to the summit craters of Etna and more distal paved areas, to have an overall view of the distribution of the tephra deposit.

The objective of the proposed method is to find any variations between the pre- and post-eruptive reflectance values in the selected areas, exploiting the different ways that different materials exhibit (in this case tephra and cement) to reflect light.

We use the cloud-based geospatial analytic Google Earth Engine (GEE) computing platform and define a dynamic threshold for the TFI of different eruptive events to distinguish the areas affected by the tephra fallout. 

We demonstrate our technique by applying it to the eruptive events that occurred in 2021 at Mt. Etna (Italy), which mainly involved the eastern and south-eastern flanks of the volcano, sometimes two or three times within a day, making field surveys difficult. Whenever possible, we compare our results with field data and find an optimal match. 

The use of satellite imagery acquired from microsatellite constellations, such as PlanetScope, providing an optimal compromise between spatial and temporal resolution, may prove fundamental for identifying tephra deposits during eruptive episodes, such as those occurred in 2021 at Mount Etna volcano. Our method provides a near real time result, making it ideal also for the mapping of other hazardous events worldwide.

How to cite: Dozzo, M., Lucchi, F., and Scollo, S.: Exploiting satellite techniques for volcanic deposits mapping: the case of 2021 Mt. Etna eruptions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7815, https://doi.org/10.5194/egusphere-egu24-7815, 2024.

EGU24-8046 | Posters on site | GMPV9.5

Volcanic activity classification trough Self-Supervised Learning applied to satellite radiance time series 

Marco Spina, Giuseppe Bilotta, Annalisa Cappello, Maddalena Dozzo, Roberto Guardo, Francesco Spina, Francesco Zuccarello, and Gaetana Ganci

Automated early warning systems for volcanoes, capable of early recognition of any signs of impending eruption, as well as to track the evolution of different kinds of eruptive activity in near real time, are essential to assess the volcanic hazards and mitigate the associated risk. Satellite imagery offers a systematic, synoptic framework for monitoring active volcanoes in even the most isolated corners of the Earth. 

Here we have applied a machine learning technique to automatically classify a pixel in SEVIRI imagery over an active volcano, in order to detect and characterize its eruptive activity. In particular, we have discriminated against five main classes of pixels: clear sky, cloud-contaminated, ash-contaminated, SO2-contaminated and thermal anomalies.

Due to the enormous amount of data and the difficulty in labeling it, we have used self-supervised learning to study data acquired since 2004. We have selected an area of 5x5 pixels around the active volcano under study and followed the spectral radiance variation of each pixel in the twelve bands availables. 

Our technique has been applied to several active volcanoes within the SEVIRI disk, including Etna, Nyiragongo, Stromboli, Nabro, La Palma and Fogo.

How to cite: Spina, M., Bilotta, G., Cappello, A., Dozzo, M., Guardo, R., Spina, F., Zuccarello, F., and Ganci, G.: Volcanic activity classification trough Self-Supervised Learning applied to satellite radiance time series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8046, https://doi.org/10.5194/egusphere-egu24-8046, 2024.

EGU24-8200 | Posters on site | GMPV9.5

The SAFARI project: An Artificial Intelligence-based strategy for volcano hazard monItoring from space 

Gaetana Ganci, Giuseppe Bilotta, Alessandro Pignatelli, Simona Scollo, and Elisa Trasatti and the SAFARI team

Identifying the observable signals that warn against volcanic unrest and impending eruptions is one of the greatest challenges in the management of natural disasters. In this regard, satellite data has become a strong focus of global interest, offering abundant datasets from multi-missions and valuable tools to study Earth and improve physical models.

The SAFARI project aims at developing a comprehensive space-based strategy for next-generation quantitative volcano hazard monitoring integrating the most recent satellite imagery capabilities and the relative products with the newest technologies mainly in the field of Machine Learning (ML) and Soft Computing. The main objectives of SAFARI include: (i) following the manifestations of unrests and impending eruptions, as well as (ii) forecasting the areas potentially threatened by volcanic products through eruptive scenarios. For this purpose, SAFARI intends to characterize the state of volcanic activity (quiet, unrest and eruptive phases) by taking advantage of a variety of satellite data, including active and passive sensors ranging from optical to microwave frequencies, and to extract quantitative satellite-derived input parameters to physical models for rapid and accurate scenario forecasting during eruptions. 

Well-established products from space-based volcano monitoring such as: (i) volcanic radiative power, (ii) surface displacement and (iii) volcanic gas emission (e.g., SO2, BrO) time series are processed jointly and supported by less frequently used but still informative time series such as (iv) ground skin temperature of the volcanic edifices, (v) change detection time series, (vi) time-varying volcanic ash indices, (vii) ash top height time series, (viii) gravity field variation and also (ix) time varying indices giving information about deformation phases of the volcanic edifice (i.e., inflation/deflation) as well as (x) crucial parameters related to the volcanic source (e.g., depth, volume variation) by using data assimilation to deformation models. SAFARI merges and assembles the latest developments from different INGV teams, in a way to analyze Earth observation (EO) data with a retrospective and multi-disciplinary approach, employing traditional statistical or numerical analysis, latest generation Graphic Processing Units (GPUs) architectures and newer and more sophisticated ML algorithms to classify time series, detect anomalies, and predict or estimate significant parameter values. 

The methodologies in SAFARI are developed and verified at four active volcanoes worldwide: Etna and Vulcano (Italy), continuously monitored by dense ground based networks managed by INGV, which will provide a first controlled experiment, and Nyiragongo (D.R. Congo) and Sangay (Ecuador), characterized by high volcanic hazard but with modest permanent monitoring networks, where satellite remote sensing is a key monitoring tool.

The results of the SAFARI project and its underlying data source and methodologies, as well as the potential of the whole integrated processing chain, aim at becoming an effective tool for volcanic hazard analysis and impact quantification never used to date in volcanology, improving safety and reducing risk associated to eruptive events worldwide.

How to cite: Ganci, G., Bilotta, G., Pignatelli, A., Scollo, S., and Trasatti, E. and the SAFARI team: The SAFARI project: An Artificial Intelligence-based strategy for volcano hazard monItoring from space, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8200, https://doi.org/10.5194/egusphere-egu24-8200, 2024.

In recent decades, Etna's main eruptive activity  was characterized by prolonged sequences of lava fountain episodes. In particular, the sequence from December 2020 to February 2022 was characterized by 65 lava fountains. After the conclusion of the last sequence in February 2022, preceded a few days earlier by a shallow seismic swarm, a powerful fountain occurred on May 21, 2023. This lava fountain was unexpected since it was far from the previous sequence and did not even  belong to a new sequence. The greatest criticality was the difficulty in monitoring this eruptive event using conventional remote sensing devices due to the bad weather conditions characterized by thick cloud cover.

In this study we present the strain data recorded by the borehole dilatometers network on Etna. The high precision strain changes make it possible to follow all the recent lava fountains providing a valuable interpretative contribution. Through new approaches recently implemented, the analysis of the strain data allowed us to identify the correct timing of the events, evaluate the ‘size’ of the fountain (i.e. its eruptive power) and estimate the erupted volumes in near real-time. In particular, during the 21 May 2023 event, the quantification of these features provided a useful support during the Civil Protection meeting convened in emergency at the Prefecture of Catania, where the evolution of these features was presented and updated in near real-time. The experience gained on the 21 May 2023 lava fountain demonstrates the contribution that the real-time high precision strain may provide to define and evaluate the hazard associated with a lava fountain even in unfavorable weather conditions, when the remote sensing systems may not be able to provide helpful information on the ongoing phenomenon.

How to cite: Bonaccorso, A., Carleo, L., Currenti, G., and Sicali, A.: Lava fountains at Etna volcano deciphered in real-time by high precisions borehole strainmeters data and implications on hazard mitigation: the 21 May 2023 case, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8437, https://doi.org/10.5194/egusphere-egu24-8437, 2024.

EGU24-8471 | Orals | GMPV9.5

A new algorithm for complex lava flow modeling driven by satellite-derived data 

Francesco Zuccarello, Giuseppe Bilotta, Flavio Cannavò, Annalisa Cappello, Roberto Guardo, and Gaetana Ganci

Lava flows represent the main hazardous phenomena that may threaten human buildings in basaltic volcanoes. Physical and chemical characteristics of lava, as well as the rate at which lava is emitted at the vents, strongly control the motion and the extensions of lava flows. Estimation of the likely paths that lava flows may follow during an ongoing eruption can be evaluated through numerical modeling driven by satellite-derived time averaged discharge rate (TADR). However, complex eruptive dynamics, such as the sequential opening of new vents, formation of lava tubes and fluctuations in effusion rates, may lead to the development of composite lava fields, which are challenging to reproduce with a simple 2D modeling. In this study, we present a new optimization algorithm based on the Metropolis-Hastings approach to model complex emplacements of lava flow fields using satellite imagery. In particular, the algorithm performs sequential time-step refinements by assimilating TADR estimations, derived from low spatial resolution satellite imagery (e.g. MODIS, SLSTR, SEVIRI), and the locations of both main and ephemeral vents, obtained from higher spatial resolution imagery (e.g. MSI Sentinel 2, OLI & TIRS Landsat 8/9 or Planetscope). The algorithm automatically chooses the optimal input parameters and the associated uncertainty, minimizing the mismatch between the simulated and the observed lava flow features extracted from multi-source satellite imagery. The testing and validation have been performed using two recent effusive events that occurred at Mt. Etna (Italy): the 27 February - 1 March 2017 and the 27 November 2022 - 6 February 2023 eruptions.

How to cite: Zuccarello, F., Bilotta, G., Cannavò, F., Cappello, A., Guardo, R., and Ganci, G.: A new algorithm for complex lava flow modeling driven by satellite-derived data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8471, https://doi.org/10.5194/egusphere-egu24-8471, 2024.

EGU24-8653 | ECS | Posters on site | GMPV9.5

Advancing Volcano Monitoring Capabilities: Deployment of Cost-Efficient GNSS Units in the Lesser Antilles on Mt. Scenery, Saba 

Andreas Krietemeyer and Elske de Zeeuw-van Dalfsen

The evolution of cost-efficient Global Navigation Satellite System (GNSS) equipment sparked increasing scientific interest to use this technology for precise geophysical measurements. In this research, we investigate the use of cost-effective GNSS units for deformation monitoring on the island of Saba in the Caribbean Netherlands. Saba hosts Mt. Scenery, an active but quiescent stratovolcano in the Lesser Antilles Volcanic Arc. The most recent eruption of the 887 metres high volcano occurred around 1640.

In February 2022, four cost-effective GNSS units were installed on the island to densify the existing Royal Netherlands Meteorological Institute (KNMI) GNSS network of four permanent GNSS stations. While the equipment costs of a permanent GNSS station quickly exceeds 10.000 Euro, the cost-efficient units come at a price of about 1000 Euro. The cost-effective unit’s design includes all necessities for independent operation: Solar charger, microcontroller, cellular data transmission, as well as remote connection via the cellular 4G connection. Compared to permanent GNSS stations, the cost-effective unit’s installation time in the field is significantly reduced.

We present the GNSS unit’s design and first deformation monitoring results of the deployed stations. The data is validated by comparing data of a cost-effective unit with those from a permanent GNSS station next to it. The GNSS units are well suited to monitor ground deformation on Saba as their daily positioning precision is similar to those of permanent GNSS stations. The cost-efficient GNSS units can therefore be used i) to expand existing deformation monitoring networks, ii) in stand-alone areas where the installation of conventional GNSS is deemed too costly, or iii) in risk-prone areas where rapid installation of expendable equipment is necessary.

How to cite: Krietemeyer, A. and de Zeeuw-van Dalfsen, E.: Advancing Volcano Monitoring Capabilities: Deployment of Cost-Efficient GNSS Units in the Lesser Antilles on Mt. Scenery, Saba, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8653, https://doi.org/10.5194/egusphere-egu24-8653, 2024.

EGU24-8686 | ECS | Posters on site | GMPV9.5

Multiscale Entropy (MSE) and Self Organizing Map (SOM): two useful tools for the interpretation of seismic signals in the Campi Flegrei Caldera 

Alberico Grimaldi, Silvia Scarpetta, Ortensia Amoroso, Vincenzo Convertito, Danilo Galluzzo, Giovanni Messuti, Ferdinando Napolitano, Guido Gaudiosi, Lucia Nardone, and Paolo Capuano

The Campi Flegrei caldera, located in Southern Italy, is one of the most hazardous volcanoes in the world. Seismic activity in the caldera has increased in the last year due to a new unrest phase of the volcano. This has driven the attention of the scientific community and both local and national media. The Campi Flegrei area is densely populated, with a very low signal-to-noise ratio, making the detection of small earthquakes or the recognition of non-seismic events more challenging.

This study introduces a novel approach to the detecting and clustering of seismic signals. Unlike conventional methods that primarily focus on the regularity of seismic patterns, our research pivots towards a complexity-centric perspective using the Multiscale Entropy (MSE) algorithm, in conjunction with the Self-Organized Map (SOM) algorithm for effective data clustering. This methodological shift allows for a more nuanced exploration of the intricate dynamics inherent in seismic activities.

Seismic signals are not random or chaotic but rather complex structures that vary across different scales. By employing the MSE algorithm, we unravel these complex patterns, offering insights into the seismic behaviours that traditional methods may overlook. Our findings indicate a significant correlation between the complexity of seismic signals and key geophysical events related to the dynamic of the volcano, suggesting that complexity analysis could be a significant tool in seismic monitoring and prediction.

The analysed dataset is a six-month long continuous signals recorded in period at the V0102 temporary seismic station installed by the INGV-Osservatorio Vesuviano close to the Pisciarelli area, located in the Campi Flegrei caldera. MSE has been applied to one-minute-long traces of signal and clusterized through the application of the SOM analysis, revealing hidden layers of complexity across multiple scales.

Moreover, the study explores the potential of integrating MSE analysis with other seismic analysis techniques to enhance the accuracy of seismic interpretations. By combining complexity analysis with traditional approaches, we aim to develop a more deep and comprehensive understanding of seismic signals, potentially leading to an improvement of the seismic risk assessment.

How to cite: Grimaldi, A., Scarpetta, S., Amoroso, O., Convertito, V., Galluzzo, D., Messuti, G., Napolitano, F., Gaudiosi, G., Nardone, L., and Capuano, P.: Multiscale Entropy (MSE) and Self Organizing Map (SOM): two useful tools for the interpretation of seismic signals in the Campi Flegrei Caldera, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8686, https://doi.org/10.5194/egusphere-egu24-8686, 2024.

EGU24-9467 | ECS | Orals | GMPV9.5

Illuminating eruptions, fluid pathways and melt storage with seismo-(acoustic) tremor at Oldoinyo Lengai volcano, Tanzania 

Miriam Christina Reiss, Francesco Massimetti, Adele Campus, Georg Rümpker, Amani Laizer, and Emmanuel Kazimoto

Oldoinyo Lengai volcano is a strato-volcano in the eastern part of the East African Rift system and as such, a curious end member of a young magmatic segment: it is the only volcano worldwide that currently erupts carbonatitic lava. Known to alternate between large explosive (ash) and smaller effusive eruptions, we analyze volcanic tremor from Oldoinyo Lengai during a renewed phase of eruptive but non-explosive activity beginning in late 2018,  which we recorded with a seismo-acoustic network between March 2019 - June 2020 with the SEISVOL (Seismic and Infrasound Networks to Study the Volcano Oldoinyo Lengai) project. We focus on two different aspects of our data set, which are the very first observations of seismo-(acoustic) tremor at this peculiar volcano.

First, we analyze one year of data at a co-located seismic and infrasound station about 200 m below the summit together with satellite InfraRed thermal data and reconstruct different phases of volcanic activity (varying styles of extrusive activity, in particular spattering, degassing, activity from a lava pond, intrusive activity, and the construction of hornitos) and the evolution of crater morphology. We characterize the near-constant but highly variable tremor by analyzing its seismic amplitude, duration, recurrence, dominant seismic frequency and harmonics. Frequency gliding occurs frequently and over short (minutes to hours) to long time scales (hours to days). Seismic and acoustic wavefields correlate well for stronger eruptive sequences but are only partially coherent which suggests that high-frequency seismic tremor (up to 25 Hz) may be caused by the low viscosity of the carbonatitic melt.

Second, we focus on a selected number of seismic network stations to locate stronger tremors using the network-covariance matrix and a raytracing approach. While many tremors locate in the shallowest part of the edifice of Oldoinyo Lengai, supporting our previous analysis that much of the tremor is caused by eruptions, tremors are also located in the crust to depths of ~15 km. Most importantly, strong (gliding/harmonic) tremor seems to be connected to a migration of tremor depths which mostly locate in rock volumes not associated with seismicity. This suggests we may be able to use tremor to study melt and fluid pathways in the mushy part of a volcanic plumbing system. Overall, our study provides important insights into the eruption dynamics, as well as melt transport and storage of this peculiar volcano.

How to cite: Reiss, M. C., Massimetti, F., Campus, A., Rümpker, G., Laizer, A., and Kazimoto, E.: Illuminating eruptions, fluid pathways and melt storage with seismo-(acoustic) tremor at Oldoinyo Lengai volcano, Tanzania, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9467, https://doi.org/10.5194/egusphere-egu24-9467, 2024.

EGU24-9964 | Orals | GMPV9.5

The characteristic of January-February 2023 Eruption of Marapi Volcano 

Dannie Hidayat, Hetty Triastuty, Dini Nurfiani, Widiwijayanti Christina, Yizhou Lou, Ahmad Basuki, Benoit Taisne, and Hendra Gunawan

After a long paused of eruption, Marapi Volcano in West Sumatra, Indonesia, started to erupt on 7 January 2023.  The eruption lasted for a couple of months.  It is followed by several months of quite period, the new, more violent eruption episodes occurred starting Dec 3, 2023 which are ongoing.  The study focus on episodes of January-February 2023 eruption to understand the volcano process, eruption behaviour compared to the past eruption and whether, in the hindsight there are precursors to the eruption that followed.  Compared to last recent episodes of eruptions, The January-February 2023 Marapi eruption consist of many explosions and degassing events. The time interval between explosions of Marapi in the beginning of eruptions, almost every hour there was an explosion, after a week time, the time interval became longer until no explosion occurred a month the first explosion.  We will also explore the mechanism of explosions from the infrasound data because the infrasound waveforms are simpler than those of the seismic waveforms. We observed the waveforms and the amplitude of infrasound in the beginning of eruption was simpler and very large at the station 300m from the active vent (> 50 Pa peak-to-peak) then the later explosions the amplitudes became smaller, and the waveforms became more oscillating coda.  This suggest the source, in the beginning it is filled with gas and fragmented magma and later the source is partially filled.  The explosions were also recorded by 4 other infrasound stations installed around the volcano up to the distance of 10 km from the vent.  Based on the observation seismicity several months prior to the first explosion of January-February 2023 Marapi eruption, there were distal volcano tectonic earthquakes clustered 4-5km the NW of the active crater.  The seismicity migrates to shallower depth below the active crater. This is supported by the observation of the tilt data from summit station and flank station, the tilt showed migration of pressure source for several months before the eruptions and that the magma pathway may probably located near the active fault zone.

How to cite: Hidayat, D., Triastuty, H., Nurfiani, D., Christina, W., Lou, Y., Basuki, A., Taisne, B., and Gunawan, H.: The characteristic of January-February 2023 Eruption of Marapi Volcano, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9964, https://doi.org/10.5194/egusphere-egu24-9964, 2024.

EGU24-10127 | Orals | GMPV9.5

Enhancing Confidence in Volcanic Ash Forecasts: Approaches for Quantifying and Reducing Uncertainties 

Helen Dacre, Natalie Harvey, and Lauren James

Generating accurate quantitative volcanic ash forecasts poses a considerable challenge, especially in remote volcanic locations where there are large uncertainties regarding the timing, quantity, and vertical distribution of ash released. Quantifying this uncertainty is crucial for providing timely and reliable volcanic hazard warnings. Our research presents methodologies aimed at quantifying the uncertainty associated with volcanic ash dispersion forecasts.  Ensemble forecasting techniques that account for input, parametric, and structural uncertainties result in volcanic ash forecasts with low confidence, making them challenging for decision-making. To enhance the utility of these forecasts, we introduce data assimilation methods that combine ensemble volcanic ash predictions with satellite retrievals, considering uncertainties from both data sources. This approach enables us to constrain emission estimates, subsequently increasing confidence in the forecasts. By applying a risk-based methodology to these refined dispersion simulations, we significantly reduce the high-risk areas, minimizing disruptions to flight operations. These findings offer insights for the design of ensemble methodologies, facilitating the transition from deterministic to probabilistic volcanic ash forecasting. 

How to cite: Dacre, H., Harvey, N., and James, L.: Enhancing Confidence in Volcanic Ash Forecasts: Approaches for Quantifying and Reducing Uncertainties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10127, https://doi.org/10.5194/egusphere-egu24-10127, 2024.

EGU24-10514 | Posters on site | GMPV9.5

FEEDS: Validation of the Framework for Evaluation of Early Detection Systems 

Flavio Cannavo, Vittorio Minio, Eugenio Privitera, Bellina Di Lieto, Pierdomenico Romano, Lorenzo Innocenti, Giorgio Lacanna, and Maurizio Ripepe

Monitoring volcanic activity is a complex task, given the intricate nature of volcanic processes and the diverse eruptive styles exhibited by different volcanoes. Early Detection (ED) systems have emerged as indispensable tools for mitigating potential risks associated with volcanic eruptions. The effectiveness of these systems is contingent upon their ability to provide timely and accurate alerts, as false alarms or missed warnings can lead to economic repercussions and pose risks to infrastructure and human safety. Evaluating the reliability of the ED systems may be paramount not only for effective hazard mitigation but also for facilitating the implementation and optimization of an ED model. However, developing an ED model is a challenging and labor-intensive endeavor, also requiring a deep understanding of advanced techniques and a meticulous calibration of various parameters. 

In response to these challenges, we present the Framework for Evaluation of Early Detection Systems (FEEDS). FEEDS is a comprehensive Python-based package designed to automatically assess the generalization capability of generic ED systems through cross-validation. The framework introduces a generic class representing the ED model identified solely through data, enabling a systematic assessment based on essential predictive parameters, including True Positive Rate, False Discovery Rate, prediction time, and Fraction of Time in Alarm, by performing a simulation. 

To validate the effectiveness of FEEDS, we utilized tiltmeter and strainmeter data recorded at Stromboli volcano between 2007 and 2019. These datasets, managed by Istituto Nazionale di Geofisica e Vulcanologia and Università di Firenze, were employed to implement FEEDS with a customized model for the early detection of the paroxysmal activity affecting the volcano during the period of the study, demonstrating the practical applicability and reliability of this framework in real-world volcanic monitoring scenarios.

FEEDS may represent a valuable contribution to the ongoing efforts to enhance ED systems and their application in mitigating volcanic hazards. The development of a robust framework that automates the standard evaluation process not only streamlines system implementation but also reduces user efforts and establishes a common ground for assessing the reliability and performance of different ED models, contributing significantly to the advancement of volcanic monitoring capabilities.

How to cite: Cannavo, F., Minio, V., Privitera, E., Di Lieto, B., Romano, P., Innocenti, L., Lacanna, G., and Ripepe, M.: FEEDS: Validation of the Framework for Evaluation of Early Detection Systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10514, https://doi.org/10.5194/egusphere-egu24-10514, 2024.

EGU24-11019 | ECS | Orals | GMPV9.5

Overview of the shallow magma reservoir, conduit properties and effusion style throughout the 2021 eruption near Fagradalsfjall, Iceland 

Eva P. S. Eibl, William M. Moreland, Thorvaldur Thordarson, Ármann Höskuldsson, Egill Árni Gudnason, Gylfi Páll Hersir, and Thorbjörg Ágústsdóttir

The 2021 Geldingadalir eruption is the first of four eruption events that have taken place since volcanic activity resumed on the Reykjanes Peninsula, SW Iceland, after an 871-year repose. It lasted from 19 March to 18 September 2021 and featured (i) continuous effusion, (ii) episodic effusion on a minute scale, and (iii) episodic effusion on an hour to day scale. The eruption transitioned between these states several times, making it the most diverse eruption on record. We provide an overview of the eruptive processes during the entire eruption using video camera footage and seismic tremor data.

Our aim is to image the changes in the subsurface structure, to identify the driving processes, and to interpret the dynamics of the volcano. We will present our view on the most striking questions: What triggered the transition between these different states? What do these different effusion states mean in the context of the conduit and the shallow magma reservoir? What can we learn from the tremor amplitude, tremor duration and repose time of such episodic events?

How to cite: Eibl, E. P. S., Moreland, W. M., Thordarson, T., Höskuldsson, Á., Gudnason, E. Á., Hersir, G. P., and Ágústsdóttir, T.: Overview of the shallow magma reservoir, conduit properties and effusion style throughout the 2021 eruption near Fagradalsfjall, Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11019, https://doi.org/10.5194/egusphere-egu24-11019, 2024.

EGU24-11452 | ECS | Posters on site | GMPV9.5 | Highlight

Volcanic eruption styles in changing environments at Katla and Eyjafjallajökull volcanoes, south Iceland 

Rosie Cole, Magnús Tumi Gudmundsson, Elisa Piispa, Birgir Óskarsson, Catherine Gallagher, Brian Jicha, and Wesley Farnsworth

It has been established through geochemical and geophysical models that, in Iceland, unloading of the Pleistocene ice sheet at the end of the last glacial period resulted in a peak in magma production and volcanic activity. Environmental differences are recorded in volcanic products, but mostly between discrete monogenetic glaciovolcanoes and postglacial lava flows. In areas of frequent and persistent activity, the way in which physical eruption styles evolved with changing ice thickness and glacial hydrology has received less attention. We examine a sequence of volcanic products exposed in the dissected flanks of Katla and Eyjafjallajökull, two ice-capped volcanoes that have been active beneath fluctuating glacial cover from the Pleistocene to present day. We use traditional geological mapping combined with photogrammetry surveys, major element geochemistry, paleomagnetic techniques and radiometric dating to determine how volcanic eruption processes have evolved with the eruptive environment throughout this period.

 

A wide diversity in the physical volcanology of deposits and major element geochemistry indicates a rich eruptive history alongside changes in glacial configuration and meltwater availability in this area. Volcanic products include pillow lavas, pillow breccias, tuff sheets 50-100 m thick, tuff mountains containing crystal-rich intrusions, lobate lava, entablature lava and compound pahoehoe lava. Evidence for glaciofluvial processes, including debris flow deposits, diamictite, and possible flood-formed canyons demonstrate additional processes that have shaped this landscape. Recognition of volcanic, constructive processes vs remobilisation and erosive processes is vital for accurately determining the distribution and source of products, particularly since edifice morphology is commonly used to characterise glaciovolcanoes.

 

Reliable dating from independent sources is necessary to determine the chronology of events and the timescale of volcano evolution. Identification of the Þórsmörk ignimbrite within the stratigraphy indicates a timescale spanning > 55 ka as well as a period of ice-free conditions. Additional age constraints from deposits in the area include a 40Ar/39Ar date from basaltic lava of < 20 ka and the identification of reworked Vedde-like pumice (< 12 ka). The sequence is capped by the 2010 Fimmvörðuháls lava. We are testing the use of paleomagnetic dating to refine the dates that have higher uncertainty and to provide additional ages for intercalated lavas that cannot be dated by radiometric isotope systems.

 

Given the ongoing changes in global glacier extent, it is critical to understand how glaciated volcanoes will behave physically. We are building an age-constrained eruptive history and record of eruptive environment from one of the most volcanically productive areas of Iceland to inform our understanding of the influence a changing environment has on volcanism.

How to cite: Cole, R., Gudmundsson, M. T., Piispa, E., Óskarsson, B., Gallagher, C., Jicha, B., and Farnsworth, W.: Volcanic eruption styles in changing environments at Katla and Eyjafjallajökull volcanoes, south Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11452, https://doi.org/10.5194/egusphere-egu24-11452, 2024.

EGU24-12280 | ECS | Posters on site | GMPV9.5

Summit and rift vent progression captured by infrasound during the 2022 Mauna Loa eruption 

Arthur Jolly, Alex Iezzi, Matt Patrick, Aaron Wech, Weston Thelen, John Lyons, and Jefferson Chang

The 2022 Mauna Loa eruption began on November 27 23:21 HST (November 28 9:21 UTC) at the summit, based on the onset of seismic tremor and visual observations of nighttime incandescence from lava viewed by webcameras.  Continued visual observations noted early southwestward migration of the summit flows followed by dike propagation and new fissures on the northeast rift zone in the early hours of November 28th HST.   Northeast rift zone activity subsequently settled into persistent activity primarily from Fissure 3 (located about 7 km from the Summit) until the eruption stagnated by December 9th HST.

This contribution provides a detailed retrospective assessment of the performance of four Hawaiian Volcano Observatory (HVO) infrasound arrays (AIND, AHUD, MENE, SHEEP) and an International Monitoring System array operated by the University of Hawaii Infrasound (I59US) data during the onset and progression of the eruption.  We use results from a standard least-squares beamforming algorithm which is widely used for infrasound processing across the USGS Volcano Science Center and compare other multidisciplinary observations such as visual and seismic amplitude.

We find that that the standard array processing approach performed adequately as a real-time assessment tool with high correlation back-azimuth computations in reasonable agreement with visual observations.  High winds associated with storms impacted the quality of our results, particularly toward the end of the eruption when infrasound signals were comparably small.  It was possible to distinguish between summit and rift fissure activity using the three long-term arrays operated by HVO, despite the large source to receiver distance.  The SHEEP array (on the south flank of Mauna Kea) was established in response to the Mauna Loa eruption and only recorded the waning phase of the eruption.  Regardless, the new array should further improve azimuthal coverage for future Mauna Loa eruptive activity.

How to cite: Jolly, A., Iezzi, A., Patrick, M., Wech, A., Thelen, W., Lyons, J., and Chang, J.: Summit and rift vent progression captured by infrasound during the 2022 Mauna Loa eruption, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12280, https://doi.org/10.5194/egusphere-egu24-12280, 2024.

EGU24-13612 | ECS | Orals | GMPV9.5

Ice-marginal lava delta in Iceland found on a nondescript shallow slope: An unexpected record of ice thickness late in deglaciation 

Audrey Putnam, Kirsten Siebach, Candice Bedford, Sarah Simpson, Elizabeth Rampe, Joseph Tamborski, and Michael Thorpe

Volcanism increases when glaciers melt because isostatic rebound during deglaciation decreases the pressure on the mantle, which enhances decompression melting. Anthropogenic climate change is now causing ice sheets and valley glaciers to melt around the world and this deglaciation could stimulate volcanic activity and associated hazards in Iceland, Antarctica, Alaska, and Patagonia. However, current model predictions for volcanic activity associated with anthropogenic deglaciation in Iceland are poorly constrained, in part due to uncertainties in past volcanic output over time compared to ice sheet arrangements. Further work specifically characterizing glaciovolcanic and ice-marginal volcanoes in Iceland is needed to reconstruct volcanic output during time periods with changing ice cover. Here, we describe a previously unrecognized ice-marginal volcanic lava delta on a broad, shallow slope southeast of Langjökull and the Jarlhettur volcanic chain in Iceland’s Western Volcanic Zone.

 

Although previously mapped as interglacial lavas and sediments, canyons in this area revealed two ~20-30 meter-thick southwest-dipping sequences of pillow-bearing tuff-breccias between pāhoehoe lava flows above modern lake Sandvatn. Clasts within the tuff-breccias include a mixture of pillow lavas and pāhoehoe fragments, requiring that the subaqueous tuff-breccia facies were derived from subaerial flows. The upper subaqueous to subaerial transition in this sequence occurs around 400 m above sea level, much higher than any local topography that could dam water or the highest Icelandic marine transgression, necessitating ice damming. Quenched meter-scale cavities in coherent lava and cube-jointed facies show lava-ice contact, supporting evidence for an ice dam. We propose that an eruption melted through thin ice near Skálpanes during a deglacial period and lavas flowed downslope to the south, melting ice and forming an englacial lake. We constrain that the local ice thickness was tens of meters to a few hundred meters thick. This would represent a similar ice configuration as some interpretations of the ice extent at the time of formation of the Buði moraines around 11.2 ka, with higher ice flow down the valley of the Hvita river than off Langjökull, although it occurred during an earlier deglaciation. Importantly, this finding demonstrates that ice-marginal deposits that can provide paleo-environmental constraints may be hidden in terrains that do not conform to existing classifications of glaciovolcanic edifices.

How to cite: Putnam, A., Siebach, K., Bedford, C., Simpson, S., Rampe, E., Tamborski, J., and Thorpe, M.: Ice-marginal lava delta in Iceland found on a nondescript shallow slope: An unexpected record of ice thickness late in deglaciation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13612, https://doi.org/10.5194/egusphere-egu24-13612, 2024.

EGU24-15102 | Posters on site | GMPV9.5

Hydrogeochemical and soil CO2 efflux weekly monitoring network for the surveillance of Cumbre Vieja volcano, La Palma, Canary Islands 

Mónica Arencibia Hernández, Rosella Feraco, Siobhan O'Shea, Sttefany Cartaya, Fátima Rodríguez, Gladys V. Melián, María Asensio-Ramos, Eleazar Padrón, Nemesio M. Pérez, Pedro A. Hernández, and Germán D. Padilla

La Palma Island, spanning 708.32 km2, resides at the north-western edge of the Canary Archipelago and is among the youngest within this group. In the last 123,000 years, volcanic activity has been exclusive to Cumbre Vieja in the island's southern region. The last volcanic activity (Tajogaite eruption) took place at the west flank of Cumbre Vieja from 19 September to 13 December 2021. It was a fissure and powerful strombolian eruption with a magnitude VEI = 3 (Bonadonna et al., 2022). Due to the absence of visible geothermal manifestations, recent decades have witnessed a burgeoning interest in studying diffuse degassing as a vital tool for volcano monitoring. With the aim of strengthening the geochemical monitoring of Cumbre Vieja volcanic activity, we have conducted on a weekly basis from October 2017 to the present, two distinct studies for volcano monitoring. Firstly, we monitored physical-chemical parameters and the chemical/isotopic composition and dissolved gases in the groundwater of two galleries (Peña Horeb and Trasvase Oeste) and three water wells (Las Salinas, Charco Verde, and San Isidro) before, during, and after the Tajogaite Volcano eruption at Cumbre Vieja from September 19 to December 13, 2021. We observed significant temporal variations in pH, EC, ion content, pCO2, and δ13C-CO2, correlating with interactions between deep volcanic fluids and groundwater. These changes showed good temporal agreement with the eruption and seismic swarms leading up to it. Simultaneously, we established a network of 21 closed static chambers to measure soil CO2 effluxes. Before the eruption (October 2017 to December 2020), the recorded soil CO2 efflux averaged 7.30 g·m-2·d-1 across Cumbre Vieja (7.48, 7.35, and 7.11 g·m-2·d-1 in the north, east, and west, respectively). Post-eruption (March 2022 to present), it averaged 7.51 g·m-2·d-1 (8.09, 7.58, and 6.99 g·m-2·d-1). The absence of data during this crucial period impedes direct comparisons and assessment of volcanic activity using this specific monitoring tool.

These methods underscore an approach to bolster volcanic surveillance on La Palma Island. Our study emphasizes the importance of monitoring the chemical and isotopic composition of groundwaters linked to active volcanic systems. Such evaluations offer critical insights into magmatic gas input within aquifers, despite limitations encountered during eruptive phases, as witnessed in the case of Cumbre Vieja in 2021.

Bonadonna et al. (2022). J.  Geophys. Res: Solid Earth, 127, e2022JB025302.

How to cite: Arencibia Hernández, M., Feraco, R., O'Shea, S., Cartaya, S., Rodríguez, F., Melián, G. V., Asensio-Ramos, M., Padrón, E., Pérez, N. M., Hernández, P. A., and Padilla, G. D.: Hydrogeochemical and soil CO2 efflux weekly monitoring network for the surveillance of Cumbre Vieja volcano, La Palma, Canary Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15102, https://doi.org/10.5194/egusphere-egu24-15102, 2024.

EGU24-16106 | ECS | Posters on site | GMPV9.5

Relationships between geodynamics of Northern Sicily (Italy) and volcanic activity at Vulcano Island (Aeolian Islands, Sicily, Italy) from GNSS and seismic data 

Danilo Messina, Graziella Barberi, Valentina Bruno, Mario Mattia, Domenico Patanè, Fabrizio Pepe, Massimo Rossi, and Luciano Scarfì

We present an analysis of Global Navigation Satellite System (GNSS) and seismic data collected in the last decade in northeastern Sicily and the Aeolian Islands (Italy). During this period, La Fossa Caldera at Vulcano showed a significant phase of unrest since September 2021. Based on the analysis of GNSS time series and velocity fields, we found evidence of changes in the deformation pattern of the Peloritani area, which is located about 40 km south of Vulcano Island in northeastern Sicily. These changes occurred about seven months before the Vulcano unrest and were accompanied by an increase in seismic strain, which was released at increasingly shallower depths. This suggests a temporal correlation between the deformations detected in the Peloritani area and the volcanic activity of Vulcano Island, which was further investigated by analyzing another phase characterized by an increase in the areal variation measured at La Fossa Caldera in 2018.   This study presents a new perspective for understanding the geodynamic, volcanic, and seismic phenomena in the investigated area, with particular attention to the Vulcan unrest between September and November 2021.

How to cite: Messina, D., Barberi, G., Bruno, V., Mattia, M., Patanè, D., Pepe, F., Rossi, M., and Scarfì, L.: Relationships between geodynamics of Northern Sicily (Italy) and volcanic activity at Vulcano Island (Aeolian Islands, Sicily, Italy) from GNSS and seismic data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16106, https://doi.org/10.5194/egusphere-egu24-16106, 2024.

EGU24-16118 | Orals | GMPV9.5

Near real-time dike tracking using GNSS networks 

Vincent Drouin, Benedikt Gunnar Ófeigsson, Halldór Geirsson, and Sigrún Hreinsdóttir

Volcanic activity can take several forms ; one of them is magma moving horizontally along the crust and forming a dike, i.e. subvertical magma-filled structures. Dikes pose substantial risk to population and infrastructure at the surface. They can transport the magma far away from the main volcanic edifice and result in eruptions in unexpected locations. The larger dikes will also induce surface faulting and even the formation of grabens. However, this means that we can measure this deformation at the surface to infer characteristics of the dike. This is traditionally done after the dike as finished propagating by using a combination of GNSS and InSAR measurements.

In Iceland, there have been 6 dikes intrusion on the Reykjanes Peninsula since 2021. The first four dikes occurred in uninhabited areas, originating from the Fagradalsfjall volcanic system. The last two dikes, in November and December 2023, originated from the Svartsengi volcano and are along an axis that goes partly under the town of Grindavik. All these dike intrusions have been recorded by the local continuous GNSS network. We tested the applicability of near real-time tracking of the dike propagation for all of these events. This is done by searching for the best-fitting Okada dislocation that explains the GNSS displacements, with some assumption about the origin and direction of the magma. The earlier events cannot be easily tracked because the GNSS network was too sparse. However, the network has been densified with time and the later events are easier to track. For the largest one, in Nov. 2023, we are able to observe the initial vertical propagation of the magma, its horizontal propagation to the SW and the NE, and its focus to SW at the end. We can measure the magma inflow rate within the dike hour by hour through the event. It peaks at over 9000 m3/s two hours after the beginning of the event. These results show that, given a network of a few continuous GNSS stations, it is possible to have a near real-time monitoring of a dike. Having this information would be extremely valuable to the decision takers and the civil protection. Therefore, it is planned to have this tool implemented at the Icelandic Met Office in the coming weeks to be able track future events. It will be set up for specific volcanoes and run automatically based on real-time GNSS solutions.

How to cite: Drouin, V., Ófeigsson, B. G., Geirsson, H., and Hreinsdóttir, S.: Near real-time dike tracking using GNSS networks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16118, https://doi.org/10.5194/egusphere-egu24-16118, 2024.

EGU24-16290 | Posters on site | GMPV9.5

Groundwater and soil CO2 efflux weekly monitoring network for the volcanic surveillance of Tenerife, Canary Islands 

Sttefany Cartaya Arteaga, Christian Isfort, Louis-Alexandre Lobanov, Ciara Mcknight, Mónica Arencibia, María Asensio-Ramos, Fátima Rodríguez, José González-Cantero, Gladys V. Melián, Eleazar Padrón, Germán D. Padilla, Nemesio M. Pérez, and Pedro A. Hernández

Tenerife, with 2034 km2, isthe largest active volcanic island of the Canarian archipelago and boasts over 1,000 galleries used for groundwater explotation, enabling access to the aquifer at varying depths and elevations. From mid-2016 to present, we've diligently sampled two important galleries - Fuente del Valle and San Fernando - on a weekly basis for volcanic monitoring. On-site measurements of water's physicochemical parameters such as temperature (ºC), pH, and electrical conductivity (E.C., µS·cm-1) were conducted at each sampling point. Subsequently, the water's chemical/isotopic composition and dissolved gases were analyzed in the laboratory. Noteworthy trends in certain parameters, including increased conductivity, sulfate (SO42-) concentration, chloride, bicarbonate, and the SO42-/Cl- molar ratio, suggest an infiltration of deep-seated gases into the groundwater. Isotopic data further revealed a robust interaction with endogenous gases like CO2, H2S, H2, etc. Additionally, correlations were discerned between specific hydrogeochemical parameters in the gallery groundwaters, correlating with observed seismic activity changes. This study underscores the sensitivity of monitoring the chemical and isotopic composition of groundwater in Fuente del Valle and San Fernando galleries to fluctuations in volcanic activity on Tenerife. Exploring groundwater associated with a volcanic system offers insights into magmatic gas input into the aquifer, models groundwater flow within the edifice, and provides vital geochemical information potentially indicating an imminent eruption.

Concurrently, a cost-effective method to gauge CO2 fluxes using alkaline traps has significantly contributed to Tenerife's volcanic surveillance. In the summer of 2016, a network of 31 closed alkaline traps was strategically placed across Tenerife's three volcanic rifts (NE, NW, and NS) and at Cañadas Caldera, persisting until the present. The weekly replacement of alkaline solutions facilitated subsequent laboratory titration analysis of the trapped CO2, expressed as weekly integrated CO2 efflux. Across the study period, the average CO2 efflux stood at 6.41 g·m-2·d-1, with variations across regions: 8.41 g·m-2·d-1 for the NE rift-zone, 5.11 g·m-2·d-1 for Cañadas Caldera, 6.36 g·m-2·d-1 for NW rift-zone, and 6.35 g·m-2·d-1 for NS rift-zone. Notably elevated CO2 effluxes were observed in the NE rift-zone, exhibiting maximum values. While the temporal evolution of CO2 efflux estimated by closed alkaline traps exhibited minimal variation during the study, seasonal fluctuations were noted. The systematic use of closed static chamber alkaline traps proves to be a straightforward and economical method aiding volcanic surveillance, especially in areas lacking visible volcanic gas manifestations.

This comprehensive approach using chemical analysis of groundwater and CO2 flux monitoring through alkaline traps showcases their combined efficacy in advancing Tenerife's volcanic surveillance, potentially serving as a crucial precursor to future volcanic activity.

How to cite: Cartaya Arteaga, S., Isfort, C., Lobanov, L.-A., Mcknight, C., Arencibia, M., Asensio-Ramos, M., Rodríguez, F., González-Cantero, J., Melián, G. V., Padrón, E., Padilla, G. D., Pérez, N. M., and Hernández, P. A.: Groundwater and soil CO2 efflux weekly monitoring network for the volcanic surveillance of Tenerife, Canary Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16290, https://doi.org/10.5194/egusphere-egu24-16290, 2024.

EGU24-16954 | Orals | GMPV9.5

Real-time monitoring the hydrothermal outgassing of the active Campi Flegrei caldera through seismo-acoustic observations 

Dario Delle Donne, Rebecca Sveva Morelli, Stefano Caliro, Maria Grazia Soldovieri, Aldo Benincasa, Ciro Buonocunto, Antonella Bobbio, Antonio Caputo, Sergio Gammaldi, Lucia Nardone, Francesco Rufino, and Massimo Orazi

Fumarolic and hydrothermal activities represent the shallow evidence of volcanic degassing within calderas, offering valuable insights for volcano monitoring. This phenomenon is particularly significant at the Pisciarelli fumarolic field in the Campi Flegrei caldera, Italy, where a continuous and vigorous release of hydrothermal and magmatic fluids occurs. This fumarolic outgassing is also associated with a persistent harmonic tremor and a persistent subtle infrasonic wavefield. Following the recent bradyseismic crisis at Campi Flegrei caldera, we established a permanent seismo-acoustic array to enhance real-time monitoring of temporal changes in fumarolic outgassing in Pisciarelli area. In particular, we exploited the seismo-acoustic wavefield produced by outgassing to assess its intensity and dynamics. Notably, we identified two distinct infrasonic sources, concurrently active and linked to 1) intense boiling in a water pool and 2) overpressurized steam release from fumarolic vents. The well-correlated temporal variations in infrasonic and seismic amplitudes offer insights into the hydrothermal system's outgassing mechanism. Specifically, they shed light on changes in the shallow hydrothermal reservoir pressure changes driving the outflow of hydrothermal gas. The integration of acoustic and seismic observations enhances our understanding of the dynamic nature of fumarolic outgassing at Campi Flegrei caldera. This improved understanding contributes to assessing volcanic risk for the caldera, as any modifications in fumarolic outgassing may indicate pressure changes in the hydrothermal reservoir.

 

How to cite: Delle Donne, D., Morelli, R. S., Caliro, S., Soldovieri, M. G., Benincasa, A., Buonocunto, C., Bobbio, A., Caputo, A., Gammaldi, S., Nardone, L., Rufino, F., and Orazi, M.: Real-time monitoring the hydrothermal outgassing of the active Campi Flegrei caldera through seismo-acoustic observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16954, https://doi.org/10.5194/egusphere-egu24-16954, 2024.

EGU24-17223 | Posters on site | GMPV9.5 | Highlight

Modelling the effusive phase of the 1944’s Vesuvio eruption using VLAVA 

Giovanni Macedonio, Louise Cordrie, Antonio Costa, Flora Giudicepietro, Francesco Obrizzo, Elena Cubellis, and Eliana Bellucci Sessa

The eruption of Vesuvio in 1944 commenced on the 18th of March and concluded on the 29th, encompassing both eruptive and seismic activities. After that date the activity decreased and has continued with low intensity until April 7, when the eruption was declared over, the crater was completely obstructed and the closed conduit period of the volcano began, which has lasted until now. During the paroxysm, the volcano underwent four distinct phases: effusive, lava fountaining, mixed explosions, and explosive events. In the initial phase (from the 18th to the 21st), the resulting lava field attained a total volume of 10^6 m^3 and a length of 5.6 km, distributed across various flows. The recent acquisition of a digitized pre-eruption Digital Elevation Model (DEM) for the region facilitates a more accurate estimation of the thickness of the final lava field by comparing it to post-eruptive LIDAR DEM data. Utilizing VLAVA, a simulation code designed for modeling lava flow propagation over complex topography with temperature-dependent viscosity, accurate modeling of the effusive phase has been achieved. These simulations contribute to a better characterization of the 1944 Vesuvius lava flow emplacement and a deeper understanding of lava flow rates from multiple vents and the subsequent lava propagation dynamics.

How to cite: Macedonio, G., Cordrie, L., Costa, A., Giudicepietro, F., Obrizzo, F., Cubellis, E., and Bellucci Sessa, E.: Modelling the effusive phase of the 1944’s Vesuvio eruption using VLAVA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17223, https://doi.org/10.5194/egusphere-egu24-17223, 2024.

EGU24-17498 | ECS | Orals | GMPV9.5

An overview of tremor and icequake types during the 2015 Eastern Skaftá jökulhlaup, Iceland 

Thoralf Dietrich, Eva P.S. Eibl, Kristin S. Vogfjörd, Sebastian Heimann, Morgan T. Jones, Benedikt G. Ófeigsson, Matthew J. Roberts, and Christopher J. Bean

Ice-covered volcanoes regularly cause subglacial floods called jökulhlaups. These may be caused by volcanic eruptions but more often they are associated with geothermal activity beneath the ice. Within this presentation we will study the largest jökulhlaup on record in Iceland using GPS sensors above the flood path, hydrological sensors and geochemical measurements in the affected river and a seismic array in combination with the local seismic network.

We detected four different tremor types: (1) Migrating tremor and high-frequency transient events follow the propagation of the flood front. (2) Minute-long tremor bursts occur in the cauldron area once the water has drained from the subglacial lake and (3) each one is followed by hour-long harmonic tremor. (4) Tremor due to more energetic flow in the rapids near Sveinstindur in the Skaftá river.

Interestingly, families of icequakes were generated in the area around the cauldron, during the onset of the flood. This grouping into families - and their consecutive activation with time - suggests that we see the gradual collapse of the ice shelf above the subglacial lake seismically.

The flood generated five different seismic signal types that can be associated with five different geophysical processes, including the wide spectrum from brittle failure and explosions to boiling and turbulent flow. We will discuss these sources in detail in the presentation.

How to cite: Dietrich, T., Eibl, E. P. S., Vogfjörd, K. S., Heimann, S., Jones, M. T., Ófeigsson, B. G., Roberts, M. J., and Bean, C. J.: An overview of tremor and icequake types during the 2015 Eastern Skaftá jökulhlaup, Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17498, https://doi.org/10.5194/egusphere-egu24-17498, 2024.

EGU24-17989 | ECS | Posters on site | GMPV9.5 | Highlight

Near real-time retrieval of weak plume source parameters: Insights from physical modeling and Meteosat data 

Audrey Michaud-Dubuy, Mathieu Gouhier, and Yannick Guéhenneux

The prediction of the spatial and temporal evolution of ash dispersal and concentrations during an explosive volcanic eruption is crucial for crisis management. Satellite observations of volcanic ash clouds have enabled an important advance in the near-real-time quantification of the dynamic parameters of the volcanic umbrella propagating in the atmosphere. However, the link between these observations and the estimation of the eruptive source parameters (ESPs), such as the mass eruption rate (MER), remains a scientific obstacle to be overcome.

Previous studies developed methods to estimate the MER based on the temporal evolution of the volcanic umbrella obtained by visible images. The accuracy of the predictions however strongly depends on the physical model used to link the measurements made on the umbrella to the source conditions. These methods are reliable for eruptions where the impact of wind is low on the vertical plume (i.e., producing “strong plumes”), but are less suitable for weaker eruptions and/or occurring under strong wind conditions (thus producing “weak plumes”), which are much more frequent. In this study, we use the 1-D volcanic column model PPM for the estimation of ESPs based on umbrella measurements from strong to weak plumes. PPM takes into account the precise effects of wind and particle sedimentation on the plume dynamics, and has already been validated with natural data on Plinian eruptions.

The model allows predicting the plume geometry as seen from space, but close to the eruptive vent. These predictions are then used to link the MER to the umbrella geometry far from the source via an empirical factor  that connects the conditions at the neutral buoyancy height to those at the source of the umbrella cloud. The model is calibrated and tested using Meteosat-SEVIRI (MSG) images via the HOTVOLC system of paroxysms from Mt Etna (2015-2022) and from the Soufriere Saint Vincent (2021). The model allows estimating the temporal evolution of the MER during the Soufriere Saint Vincent eruption, with values consistent with those estimated in the field. The model also provides a theoretical framework to explain the geometry of weak plumes from Mt Etna. Ultimately, this study will provide a robust tool for a rapid interpretation of satellite data in terms of source conditions, which are necessary inputs for volcanic ash transport and dispersion models, such as those used by the Volcanic Ash Advisory Centers.

How to cite: Michaud-Dubuy, A., Gouhier, M., and Guéhenneux, Y.: Near real-time retrieval of weak plume source parameters: Insights from physical modeling and Meteosat data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17989, https://doi.org/10.5194/egusphere-egu24-17989, 2024.

EGU24-18052 | ECS | Posters on site | GMPV9.5

Estimating Pleistocene ice thickness from pillow lava melt inclusions in the south-central highland of Iceland 

Harrison Collins, Eniko Bali, and Magnus T. Gudmundsson

Paleoclimate records show that Iceland was at times fully covered during Pleistocene glaciations. Models and data for the last glacial maximum indicate that the ice sheet at this time extended several tens of kilometers beyond the present coast. In contrast, much is known about the extent of the ice sheet during other times of the Weichselian glaciation, and very little information exists on possible variations of earlier glaciations. The regions near Þórisvatn, Jökulheimar, and Bláfjöll in the south-central highland of Iceland contain many outcrops of Pleistocene pillow lavas. The volatile contents in the glassy rims of pillow lavas may record the ambient pressure during eruption. This could offer insight into syn-eruptive glacier thickness. 15 samples were collected from three sample locations near Þórisvatn, one near Jökulheimar, and four near Bláfjöll from August 14 to August 15, 2023. Samples were crushed and sieved into 0.5-2.0 mm grains, and the glassiest grains were double polished with thicknesses between 88–219 µm for FTIR analysis. The spectra showed strong similarity to FTIR spectra of Holuhraun samples of similar thickness. H2O contents of the samples varied between 0.22–0.32 wt%, with a median of 0.30 wt%. CO2 was under the detection limit of the FTIR analyses. This may be an artifact of polishing grains too thin, and thus separate analyses with thicker grains will be carried out to accurately assess ambient pressure due to pressure model sensitivity to CO2. Further analysis will include S concentrations, which will be used alongside H2O and CO2 to calculate a precise ambient pressure with the Sulfur_X model (Ding et al., 2023). The derived parameters will be used to estimate glacier thickness.

How to cite: Collins, H., Bali, E., and Gudmundsson, M. T.: Estimating Pleistocene ice thickness from pillow lava melt inclusions in the south-central highland of Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18052, https://doi.org/10.5194/egusphere-egu24-18052, 2024.

EGU24-18088 | Posters on site | GMPV9.5

FEM model of surface deformation pattern and a first application on real data at Campi Flegrei caldera 

Pierdomenico Romano, Prospero De Martino, Bellina Di Lieto, Annarita Mangiacapra, Zaccaria Petrillo, and Agata Sangianantoni

Campi Flegrei Caldera is an active volcano located westward of Naples, Italy. Despite its volcanic activity spanning over 39,000 years, the area is densely populated and poses a significant threat to the inhabitants due to ongoing seismicity, ground uplift, and hydrothermal activity resulting from increased pressure due to fluid injections and thermal variations at depth. These factors highlight the potential for a major volcanic eruption. Being able to model the processes that lead to ground deformation could be of vital importance in predicting an imminent eruption and enabling the evacuation of the resident population in the area.

Such models are being schematized and analyzed using specific Finite Element Method (FEM) software capable of solving complex mathematical problems involving partial differential equations. In this manuscript, we utilized COMSOL Multiphysics, configured with the structural mechanics module, to examine how deep changes in pressure and temperature influence the observed surface deformation field within the Campi Flegrei caldera. To simulate these deep changes, we employed the Tough software, an open-source numerical simulation program designed for multi-dimensional fluid and heat flows of multiphase and multicomponent fluid mixtures in porous and fractured media. The output of Tough served as an input for the COMSOL model, representing the source at depth. By using the structural mechanics module, we were able to assess the accuracy of the proposed model in comparison to analytical solutions. Furthermore, we were able to model the geometry of the deep source in more detail and verify that the surface deformation pattern aligned with the measurements obtained from sensors. By leveraging COMSOL Multiphysics, therefore, we have constructed a mathematical model that accurately captures the intricate interplay of fluid injections, thermal variations, and rock mechanics, enabling us to simulate volcanic crustal deformations with remarkable fidelity: the surface deformations obtained through simulation aligns with those observed through GPS/GNSS, strain and tilt time series recorded by the Osservatorio Vesuviano monitoring networks.

Valuable information are embedded in the data used in the current work, which could be used not only for scientific purposes but also from civil protection for monitoring reasons. Such a variety of possible usage needs the setting of principles and legal arrangements to be implemented in order to ensure that data will be properly and ethically managed and in turn can be used and accessed from the scientific community.

How to cite: Romano, P., De Martino, P., Di Lieto, B., Mangiacapra, A., Petrillo, Z., and Sangianantoni, A.: FEM model of surface deformation pattern and a first application on real data at Campi Flegrei caldera, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18088, https://doi.org/10.5194/egusphere-egu24-18088, 2024.

EGU24-18410 | ECS | Posters on site | GMPV9.5

Spatial probability of vent opening at the active central volcanoes of São Miguel (Azores) 

Simone Aguiar, Laura Sandri, Adriano Pimentel, Sérgio Oliveira, and José Pacheco

Forecasting the location of future volcanic eruptions is one of the most critical and challenging issues when assessing volcanic hazard. A long-term hazard assessment approach based on past eruptive behaviour is of utmost importance for dormant or low-activity volcanoes, on which sound land-use policies and risk mitigation plans should be based.
São Miguel Island in the Azores Archipelago hosts three active central volcanoes (Sete Cidades, Fogo, and Furnas) that produced a large variety of eruptions in the last millennia and even in historical times, including trachytic explosive and effusive events and basaltic flank eruptions. 
Although these volcanoes are currently in a repose period, the likelihood of future eruptions should not be neglected.  
This study focuses on the estimation of the spatial probability of vent opening at the Sete Cidades, Fogo, and Furnas volcanoes separately, using the kernel method. Here, we used the location of past basaltic and trachytic emission centres, in the form of vents or fissures, of each volcano, to explore different kernel functions (Gaussian, Cauchy, Exponential, and Uniform) and calculate the best degree of clustering of vents given by a smoothing parameter (h). This approach was applied to each volcano by considering (1) basaltic and trachytic emission centres (fissures and/or vents) and (2) only trachytic emission centres (vents). This allowed us to estimate the pair (kernel function and h-value) that best fits the empirical cumulative distribution function of the minimum distance between emission centres and compute the final vent opening probability maps conditional to an eruption (or susceptibility maps).
For Sete Cidades, the results show that when considering basaltic and trachytic emission centres together, the southeast and west flanks of the volcano have a higher likelihood of hosting a new vent; however, when considering trachytic vents alone, the higher probability is at the west flank and southern sector of the caldera. The susceptibility map generated using Fogo’s basaltic and trachytic emission centres indicates a higher likelihood of hosting a new vent at the northwest flank of the volcano and southeast sector of the caldera. When only trachytic vents are considered, the southeastern sector of the caldera is more likely to host a new vent. For Furnas volcano, the results show that the northwestern part of the caldera has a higher likelihood of hosting a future basaltic or trachytic vent.

How to cite: Aguiar, S., Sandri, L., Pimentel, A., Oliveira, S., and Pacheco, J.: Spatial probability of vent opening at the active central volcanoes of São Miguel (Azores), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18410, https://doi.org/10.5194/egusphere-egu24-18410, 2024.

EGU24-18805 | Orals | GMPV9.5 | Highlight

Ice cauldrons and their relationship with volcanic and geothermal activity in ice-covered volcanoes in Iceland 

Magnus Tumi Gudmundsson, Thordis Hognadottir, Hannah I. Reynolds, Eyjolfur Magnusson, and Finnur Palsson

About 10% of Iceland is covered by glaciers, including three of the four most active central volcanoes, Grímsvötn, Katla and Bárðarbunga, where the ice-filled calderas have glacier thickness of several hundred meters.  Ice cauldrons, defined as circular or elongated depressions in the surface of glaciers which form due to enhanced basal melting, are very common in the ice-covered volcanic areas in Iceland.  Many have concentric crevasses.  Over 100 cauldrons have been identified in the glaciers of Iceland, with over half being located within or adjacent to the calderas of Grímsvötn, Katla and Bárðarbunga.  Ice cauldrons are usually a sign of subglacial geothermal activity, while occasionally cauldrons are formed during subglacial volcanic eruptions.  Some cauldrons are short term features, existing for some years, indicating transient geothermal activity or recent occurrence of a volcanic eruption.  Others are semi-stable features that have existed for several decades, possibly centuries.  Stable cauldrons are always associated with geothermal activity and the same applies to many of the intermittently active ones as well.  Cauldrons formed in volcanic eruptions tend to be deep and with larger depth/width ratios than geothermal cauldrons.  The widest cauldrons observed in Iceland reach 4-5 km in diameter while diameters of 0.5-1.0 km are the most common.   The size and form of geothermal ice cauldrons depends to a considerable degree on the ice thickness.  Where thickness is small (<100 m), cauldrons can be holes with steep slopes or vertical ice walls and may in some cases reach the base of the glacier.  Where ice thickness exceeds 200-300 m, geothermal cauldrons rarely form vertical ice walls.  In most cases, it is clear which cauldrons are formed by sustained geothermal activity. Volcanic cauldrons tend to reach their maximum size rapidly, followed by gradual decline as the erupted volcanic material loses its heat quickly and ice flow gradually fills the depression.  However, despite gradual infill by ice flow and reduction in cauldron depth, volcanically formed depressions may persist for decades.  An example of this is the tens-of-meters deep and 2-3 km wide depression at the site of the 1996 Gjálp eruption, which is still visible.  Ice thickness at this site was ~600 m prior the eruption. Beneath some ice cauldrons meltwater accumulates at the base of the glacier.  This may result in semi-periodic release of meltwater in jökulhlaups.  Other cauldrons may drain more or less continuously. 

How to cite: Gudmundsson, M. T., Hognadottir, T., Reynolds, H. I., Magnusson, E., and Palsson, F.: Ice cauldrons and their relationship with volcanic and geothermal activity in ice-covered volcanoes in Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18805, https://doi.org/10.5194/egusphere-egu24-18805, 2024.

EGU24-19010 | Posters on site | GMPV9.5

150 years of Etna Summit Craters through a photogrammetry-based time machine 

Cantarero Massimo, De Beni Emanuela, Proietti Cristina, Bonali Fabio Luca, Palano Domenico, Civico Riccardo, and Paratore Mario

Etna is one of the most active volcanoes in the world, with almost continuous eruptive activity from its four summit craters resulting in frequent morphological variation of its upper area. The summit area is frequently site of effusive and explosive activity, but also of local flank collapses of the summit cones and pyroclastic flows with different triggering mechanisms. Such a dynamic environment requires a thorough understanding of its temporal evolution in order to properly assess the state of the volcano over time, and infer further insight into its potential hazard. Voragine (VOR), formerly called the Central Crater, is the oldest and has been depicted on topographic maps since at least 1865; the NE-Crater (NEC) cone was born in 1911; the Bocca Nuova started as a pit crater next to Voragine in 1968, and the SE-Crater (SEC) cone started in 1971. Since 2011, a new cone grew on the SEC eastern lower flank during a series of paroxysmal episodes and it progressive coalesced with the SEC cone. To properly model the temporal changes of the summit area, we exploited archival topographic maps and aerial photogrammetric stereo-pairs. This reconstruction started from the digitising and processing of topographic maps that were produced on 1897, 1932, and 1985. We also processed aerial stereo-images acquired since 1954. From these datasets we extracted Digital Elevation Models (DEMs) with 5-10 m pixel size. We integrated historical data with already available DEMs: the 1998 and 2001, interpolated from vector maps; the 2005, obtained from aerial photogrammetry; and the 2012, 2014 and 2015 derived from helicopter-acquired data. Finally, between 2017 and 2023 we performed UAS (unoccupied aerial systems) surveys to derive high-resolution DEMs and orthomosaics with sub-meter pixel size. This new multi-temporal Digital Elevation Models (DEMs), from ancient topographic maps and aerial photo as well as from recent and current UAS data, have been analysed through the ESRI ArcGIS software to reconstruct the topography and quantify the main morphological changes of Etna summit area. Our modelling increases the knowledge about the evolution and the behaviour of a frequently active volcano, thus enabling to mitigate the associated risks.

 

How to cite: Massimo, C., Emanuela, D. B., Cristina, P., Fabio Luca, B., Domenico, P., Riccardo, C., and Mario, P.: 150 years of Etna Summit Craters through a photogrammetry-based time machine, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19010, https://doi.org/10.5194/egusphere-egu24-19010, 2024.

EGU24-19414 | ECS | Posters on site | GMPV9.5

Earthquake focal mechanisms before and after the onset of re-inflation at Askja caldera, Iceland 

Isabel Siggers, Tom Winder, Nicholas Rawlinson, Robert S. White, and Bryndís Brandsdóttir

Askja, an active volcano in Iceland’s Northern Volcanic Zone, has experienced over 70 centimetres of uplift since August 2021, following several decades of ground surface deflation. In the same month that surface uplift began, there was also an overall increase in shallow microseismicity. This overlap suggests that there is a link between the shallow seismicity and re-inflation, but much more information is needed to constrain an exact mechanism.

 

To gain more insight into the stresses driving seismicity beneath Askja, and how they may have changed with the onset of uplift, moment tensor solutions were constructed from a subset of events within the Askja caldera, both before and after the start of re-inflation. The goal is to uncover any dominant earthquake slip orientation patterns, and how they have changed post August 2021. Cambridge’s Volcano Seismology Group has maintained a dense seismic network surrounding and within Askja from July 2007 to the present day, which provides sufficient data to produce well constrained moment tensor solutions, even for events as small as magnitude 0.5.

 

Moment tensor solutions constructed from the first year of inflation suggest that the direction of slip along faults encircling the crater lake Öskjuvatn did not change when Askja switched from deflation to re-inflation; however, data from a longer recording period is needed to provide a definitive conclusion. With another 12 months of data from the main network now downloaded, as well as additional data from a supplementary dense network of seismic nodes within the Askja caldera from July 2023 to September 2023, a more in-depth analysis of the moment tensor solutions for shallow microearthquakes underneath the region of uplift through time is now possible. The preliminary results of this analysis will be presented, along with plans for future interrogation of this enhanced dataset.

How to cite: Siggers, I., Winder, T., Rawlinson, N., White, R. S., and Brandsdóttir, B.: Earthquake focal mechanisms before and after the onset of re-inflation at Askja caldera, Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19414, https://doi.org/10.5194/egusphere-egu24-19414, 2024.

EGU24-19747 | Orals | GMPV9.5 | Highlight

Lava flow monitoring from EO microwave imageries 

Christian Bignami, Emanuele Ferrentino, Lisa Beccaro, and Marco Polcari

In this study, microwave satellite images, and in particular Synthetic Aperture Radar (SAR), are used to detect volcanic lava flow. We propose methods that exploit both single and dual polarization channels to map the deposits that occurred in three case studies: the Etna Volcano (Italy) 2007-2008 eruption and the Sangay Volcano (Ecuador) eruption that took place in December 2021.

The objective of the work is to analyse the different information carried out by single and dual polarization data, in different volcanic environments, aiming to identify the most suitable solution for each setting.

For the Etna case study, we applied two change detection methods. The first one exploits the normalised difference and is used on a pair single polarization (SP) image captured by ENVISAT mission. The second method relies on the dual polarization (DP) data acquired by ALOS-PALSAR satellite. The latter is based on the covariance matrix derived from DP images, and the normalized difference of pre and post-event matrices.

As far as the Sangay case study, the results are undertaken over a pair of images collected by the C-band Sentinel-1 DP SAR sensor. The outputs are then analyzed to detect the different phenomena (i.e., lava flow, pyroclastic currents, landslides), that occurred over the scene.

The work demonstrates the complementary evidence provided by the co- and cross-polarized channels, suggesting the combination of them to obtain additional and more accurate information.

This activity is part of a INGV funded project, SAFARI - an AI-based StrAtegy For volcano hAzaRd monItoring from space, a research project that aims at developing a comprehensive space-based strategy for the near-real-time characterization of volcanic state of activity, based on the extraction of satellite-derived input parameters to physical models for rapid scenario forecasting during the eruptive phases.

How to cite: Bignami, C., Ferrentino, E., Beccaro, L., and Polcari, M.: Lava flow monitoring from EO microwave imageries, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19747, https://doi.org/10.5194/egusphere-egu24-19747, 2024.

GMPV10 – Mantle-core fingerprints at Earth's surface - the connections

EGU24-124 | ECS | Posters on site | GMPV10.1

Multiple melt extraction in Neo-Tethyan mantle and the Supercontinent heritage: insights from geochemical signatures of mantle peridotites from Naga Hills ophiolite, Indo-Myanmar ranges 

Anisha Verencar, Abhishek Saha, Sohini Ganguly, Manavalan Satyanarayanan, and Mekala Ram Mohan

The Naga Hills Ophiolite (NHO) exposed on the northeastern margin of India, represents a thrusted section of Neo-Tethyan oceanic lithosphere comprising distinct crustal and upper mantle lithologies accreted onto continental margins at Indo-Myanmar ranges during late Cretaceous-Eocene collision between Indian and Eurasian Plates. This study focuses on the whole-rock geochemistry and Re-Os isotopic compositions of the mantle peridotites from NHO to address the implications on the upper mantle heterogeneity and thermo-tectonic evolution of Neo-Tethyan oceanic lithosphere through time. The chondrite normalized REE patterns, and low Re/Os, suggests that, these are mantle residues resulting from ~5–20% of melt extraction from a spinel peridotite source. The refractory characters of the studied mantle peridotites from NHO are further complemented by relatively enriched concentrations of transition elements like Cr, Ni and Co with respect to primitive mantle composition. PGE modeling from melt fractionation indices [(Pt/Ir)N and (Pd/Ir)N] and depletion index (Al2O3) corroborates discernible melt depletion trends. Isotopically, these mantle peridotites are subchondritic with 187Os/188Os (0.1218-0.1266) and γOs (gamma osmium) values of -3.73 to -0.09 comparable with depleted MORB mantle source.  LILE-LREE enrichment, HFSE depletion, and U-shaped chondrite-normalized REE patterns, distinct S-undersaturated trend and Re addition suggest multistage petrogenetic processes including refertilization of pre-existing depleted, refractory mantle wedge by subduction-derived fluids and instantaneous fractional melts operative in an intraoceanic fore-arc environment. Re-Os isotopic plots reflect the role of ancient depleted Subcontinental lithospheric mantle (SCLM) and the large variations in ɣOs values attest to involvement of both SCLM and depleted MORB component thereby contributing to pronounced Os isotopic heterogeneities in the upper mantle that in turn manifest inputs of discrete depleted and enriched mantle components during opening and closure of ocean basins synchronized with assembly and dispersal of continental blocks. The model ages (TMA) for the mantle peridotites reveals a wide spectrum of ages  ranging from 1142 Ma – 145 Ma suggesting multiple episodes of melt extraction events prior to the opening of Neo-Tethys (~250Ma) and encapsulation of ancient SCLM fragments correlatable with Gondwana Supercontinent amalgamation and disintegration coupled with closure and opening of the Tethyan ocean basins.

How to cite: Verencar, A., Saha, A., Ganguly, S., Satyanarayanan, M., and Ram Mohan, M.: Multiple melt extraction in Neo-Tethyan mantle and the Supercontinent heritage: insights from geochemical signatures of mantle peridotites from Naga Hills ophiolite, Indo-Myanmar ranges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-124, https://doi.org/10.5194/egusphere-egu24-124, 2024.

In this study, we present a new analysis of 12,515 pre-analysed garnet xenocrysts recovered from kimberlites from the Barkly West kimberlite cluster. These kimberlites were emplaced in the western Kaapvaal Craton, South Africa in two pulses. These analyses are used to constrain the chemical and thermal structure of the subcontinental lithospheric mantle (SCLM) beneath the Kaapvaal Craton. In South Africa, kimberlites are distinguished based on geochemistry and petrology: (1) the hydrous, K-rich, and generally older Group II (age: ~200-114Ma; aka Kaapvaal lamproites) and (2) the younger, carbonate-rich and magnesian Group I kimberlites (age: ~112-86Ma). Upon ascent, kimberlites entrain mantle xenoliths, xenocrysts (e.g., garnet) and sometimes diamonds. Historically, mantle xenoliths have been employed to investigate the SCLM, but the large abundance of xenocrysts, available from a larger array of kimberlites, allows a more spatially robust characterisation of the SCLM. We investigate peridotitic garnets, i.e., G10 (CaO-poor) and G9 (CaO-rich) garnets, to allow single-mineral thermobarometry. Generally, G10 garnets have low CaO and high Cr2O3 contents and high Mg-numbers relative to G9 garnets. G9 garnets are typically more enriched in incompatible elements (i.e., Zr, Y, Ti) and heavy REE. Profiles of mantle composition obtained from garnets exhumed by both Group I and Group II kimberlites provide evidence for (likely metasomatic) enrichment of the SCLM at depths greater than 90-150 km, with the enrichment revealed by garnets from group I kimberlites being generally greater in magnitude and extending to shallower depths. Distinctions between Group II and Group I derived garnets suggest modification of the SCLM by two distinct metasomatic agents, and that Group I-related metasomatism was much more pervasive. For each kimberlite group, two paleogeotherms were calculated (one each for G10 and G9 garnets) using garnet thermobarometry. For Group II kimberlites, the G10- and G9-based paleogeotherms are very distinct from each other, cooler and warmer paleogeotherms, respectively. However, for Group I kimberlites, the paleogeotherms obtained from G10 & G9 are consistent with each other and are similar to the G9-based paleogeotherm obtained from Group II kimberlite xenocrysts. We infer that the Group II G10-based paleogeotherm, which has the lowest thermal gradient, is consistent with a steady state cratonic geotherm, devoid of transient thermal perturbations. However, geotherms with higher gradients obtained from Group II G9 and all Group I peridotitic garnet xenocrysts are the products of transient thermal disturbances, likely related to the effect of hot infiltrating melts. Recent seismological studies have discovered sharp velocity changes within the SCLM known as mid-lithospheric discontinuities (MLDs). Globally, negative MLDs observed in cratonic areas have been associated with metasomatism. However, beneath the Kaapvaal Craton we note positive MLDs, which coincide with the observed layer of metasomatism which has resulted in increased clinopyroxene and garnet modal abundance. Is clinopyroxene and garnet generation responsible for positive MLDs beneath the Kaapvaal Craton?

How to cite: Hashibi, S., Janney, P., Sloan, A., and Quiros, D.: Using kimberlite indicator mineral geochemistry to better constrain the thermal and chemical structure of the lithospheric mantle beneath the Kaapvaal craton: correlations with S-to-P receiver functions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1107, https://doi.org/10.5194/egusphere-egu24-1107, 2024.

EGU24-3978 | Posters on site | GMPV10.1

Amphibole origin in the mantle lithosphere peridotites beneath continents: An example from Marais de Limagne (Massif Central, France) xenoliths 

Jacek Puziewicz, Sonja Aulbach, Theodoros Ntaflos, and Magdalena Matusiak-Małek

The Marais de Limagne (MdL) site is located at the Devès volcanic field in the French Massif Central. MdL is known for abundant peridotite xenoliths, which come from the “southern domain” of lithospheric mantle underlying Variscan crust of the Massif Central. The MdL xenolith suite consists of spinel lherzolites and harzburgites which contain from 0 to 21 vol. % of amphibole (Touron et al. 2008). We studied in detail 13 xenoliths in order to understand better the mechanisms of amphibole formation by modal metasomatism.

The suite studied by us contains from 0 to ca. 20 vol. % of amphibole, the textural context and volume of which varies from thin rims of the mineral on spinel to rocks containing thick mantles of amphibole on subordinate or relict spinel. Exceptionally (one xenolith), amphibole occurs as interstitial grains independent of spinel. Amphibole is pargasite sensu IMA 2012 classification. Peridotites consist of olivine Fo 89.4-90.5, orthopyroxene Al 0.11-0.19 atoms per formula unit (apfu), clinopyroxene Al 0.13-0.28 apfu and spinel Cr# 0.09-0.39. The exception is harzburgite with olivine Fo 87.0 (orthopyroxene Al 0.11, clinopyroxene Al 0.15 apfu, spinel Cr# 0.15). Clinopyroxene REE patterns vary from LREE-depleted to LREE-enriched. The abundance of amphibole in many xenoliths and equal participation of peridotites with LREE-depleted and LREE-enriched clinopyroxene distinguishes the MdL suite from other xenolith suites from the Devès volcanic field, dominated by lherzolites which contain no or only traces of amphibole and mostly contain aluminous clinopyroxene with LREE-depleted REE patterns.

Clinopyroxene occurring in rocks containing no or little amphibole has < 100 ppm of Sr, whereas that coexisting with abundant amphibole has 230-370 ppm of Sr. The content of Ba in amphibole varies from 2.6 ppm in rocks with only thin rims of mineral on spinel to 467.0 ppm in those which contain high volumes of amphibole. The REE patterns of amphibole are similar to those of coexisting clinopyroxene. Because both Sr and Ba are fluid-mobile elements, we assume that amphibole has originated by reaction of hydrous fluid with spinel, in which clinopyroxene has also participated as a source of elements not present in a fluid or spinel. By analogy with a similar mechanism described by Puziewicz et al. (2023), we speculate that hydrous fluid migration through the peridotite host might have induced its recrystallization.

Puziewicz et al. 2023, Journal of Petrology 64: https://doi.org./10.1093/petrology/egad049

Touron et al. (2008), In: Metasomatism in Oceanic and Continental Lithospheric Mantle, Geological Society Special Publ. 293, 177-196.

How to cite: Puziewicz, J., Aulbach, S., Ntaflos, T., and Matusiak-Małek, M.: Amphibole origin in the mantle lithosphere peridotites beneath continents: An example from Marais de Limagne (Massif Central, France) xenoliths, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3978, https://doi.org/10.5194/egusphere-egu24-3978, 2024.

EGU24-4509 | ECS | Posters on site | GMPV10.1

Petrogenesis of mantle peridotite of the Jabal Ess ophiolite, NW Saudi Arabia 

Sabyasachi Chattopadhyay, Faris Sulistyohariyanto, Scott Whattam, Mutasim Osman, and Oktarian Iskandar

Neoproterozoic ophiolites are widespread in the Arabian-Nubian Shield (ANS) and mostly occur along or within suture zones that extend roughly from north to south. These ANS ophiolites represent fragments of forearc-derived oceanic lithosphere generated during a stage of subduction initiation in the Mozambique Ocean. One of these ophiolites is the Jabal Ess ophiolite (JEO) which is the most complete of the Arabian ophiolites. The ~780 Ma JEO is situated in the far north of Saudi Arabia, where it crops out in an area more than 30 km east-west by 5 km north-south and comprises a segment of the Yanbu suture zone separating the Hijaz terrane from the Midyan terrane. The JEO comprises an assemblage of mantle peridotite, isotropic and layered gabbro, a dike complex, pillow basalt, boninite and pelagic sediments and the focus of this study is the mineralogy and geochemistry of the peridotite. Our study identifies predominantly serpentinized harzburgite in the NE and lesser serpentinite to the SW. Whole rock Al2O3/SiO2 of 0.01–0.02 confirm a high degree of melt extraction for the serpentinized harzburgite; the two serpentinites yield Al2O3/SiO2 of 0.04 and 0.08 with the higher value possibly due to silica-melt addition. Harzburgites exhibit U-shaped chondrite-normalized REE patterns with low concentration (∑REE 7.46–10.79 µg/g), typical of melts derived from a depleted mantle. These signatures probably represent residual mantle after boninite extraction. Alternatively, the two serpentinites have wider ranges of ∑REE=4.35–7.10 µg/g with one showing a U-shaped pattern akin to the harzburgite and one showing a LREE depletion (La/YbCN = 0.51) relative to the MREE and HREE. Mineral assemblages from the serpentinized harzburgite and serpentinite record greenschist facies metamorphism. The serpentinized harzburgite unit comprises Mg-rich olivine (Fo92-90), bastite after orthopyroxene (En90-86), minor clinopyroxene (Wo52-50, En47-46, Fs4-1), and euhedral to anhedral spinel. Some enstatite shows crystallographic banding, indication of high temperature sub-solidus deformation within the plastic mantle. Serpentinites are characterized by abundant high-pressure antigorite and altered anhedral spinel, e.g., spinels which exhibit noticeable chemical zonation of cores rich in Al (a.p.f.u=0.47–0.49) and Cr (a.p.f.u=0.50–0.99) with Fe-enrichment (a.p.f.u=0.72–0.98) towards the rim. Based on spinel Cr# (0.56–0.72) the serpentinized harzburgites and serpentinites have undergone high degrees of partial melting of ~18–20% consistent with the low whole rock Al2O3/SiO2.  Moreover, based on Cr# vs Mg# (0.48-0.61) the serpentinized harzburgite and serpentinite plot within the field of forearc peridotite. Results of oxygen fugacity and thermobarometry calculations will be discussed in the context of the compositional evolution of Jabal Ess harzburgite and serpentinite in the framework of formation during subduction initiation.

How to cite: Chattopadhyay, S., Sulistyohariyanto, F., Whattam, S., Osman, M., and Iskandar, O.: Petrogenesis of mantle peridotite of the Jabal Ess ophiolite, NW Saudi Arabia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4509, https://doi.org/10.5194/egusphere-egu24-4509, 2024.

EGU24-6225 | ECS | Posters on site | GMPV10.1

Following the tracers of magma mixing; mafic enclaves within volcanic rocks at the Methana peninsula 

Vasileios Giamas, Lemonia Kalantzi, Petros Koutsovitis, Petros Petrounias, and Theodoros Ntaflos

The presence of mafic enclaves within volcanic rocks, which present an evolved geochemical character, tends to be related to magma mixing. In the Hellenic Volcanic Arc, mafic enclaves are regularly encountered within the volcanics. There are a few reports regarding the islands of Santorini and Nisyros as well as in the peninsula of Methana. The petrographic and mineral chemistry data we present here concern enclaves only from the Methana peninsula. Enclaves in Methana vary in size (from a few cm up to hand-sized samples) and color (reddish to black) depending on their host lava. The typical mineral assemblage is amphibole + clinopyroxene + olivine + plagioclase ± spinel ± mica. Mineral phases of amphibole, olivine, and clinopyroxene form the major phenocrysts that are embedded within a matrix mostly of fine-grained plagioclase laths and fine-grained needle-shaped amphibole. Textural features of plagioclase reveal the predominance of wet conditions during their crystallization since their cores and/or intermediate growth zones are usually dissolved suggesting a hydrous and volatile enriched magma related to the mafic enclaves. The aforementioned mineral assemblage along with the latter petrographic features match with lamprophyric rocks and their typical porphyritic and panidiomorphic textures. This counterpart is further ascertained by the mineral chemistry of Mg-rich amphibole varieties, and primary forsterite-rich olivine as well as by the lamprophyre-related trends of clinopyroxene and mica. These preliminary results provide new insights regarding magma mixing processes that occurred at the western margin of the Hellenic Subduction Zone.

Acknowledgments

This work is part of the first author's Ph.D. research, which is financially supported by the «Andreas Mentzelopoulos Foundation».

How to cite: Giamas, V., Kalantzi, L., Koutsovitis, P., Petrounias, P., and Ntaflos, T.: Following the tracers of magma mixing; mafic enclaves within volcanic rocks at the Methana peninsula, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6225, https://doi.org/10.5194/egusphere-egu24-6225, 2024.

EGU24-6324 | ECS | Posters on site | GMPV10.1

Miocene basaltic lavas from Chios Island: Petrogenetic implications 

Lemonia Kalantzi, Vasileios Giamas, Petros Koutsovitis, Petros Petrounias, Christoph Hauzenberger, and Theodoros Ntaflos

Extensional processes related to subduction initiation stages often result in the formation of back-arc basins. In central Anatolia and the northern-central Aegean, the main lithotypes geochemically correspond to high-K calk-alkaline rocks that formed during the Early Miocene, while volcanism in the Middle Miocene was predominantly Na-rich. The latter lithotypes were in most cases significantly affected by differentiation processes. On the island of Chios, volcanism is comprised of lithotypes that vary significantly from alkali basalts to rhyolites. In particular, the Pyrgi lavas are fine-grained with typical porphyritic and seriate textures, which are classified as alkali basalts according to the AFM ternary plot. These lavas also exhibit positive anomalies in PM-normalized P, Sr, and Pb elements and significant enrichments in LILE (i.e., Cs, Rb, Ba), presenting a probable interaction with subduction melts. The negative correlation between SiO2 contents and the Nb/Yb ratio indicates that crustal contamination did not play a significant role during differentiation. Crystallization appears to be under extremely dry conditions due to the absence of hydrous phases (e.g., amphibole). The presence of MORB signature spinel crystals suggests the implication of a MORB-type source. In the case of Chios, the high Nb tholeiites can be associated with petrogenetic processes in which OIB-related melts interacted with the previously metasomatized mantle wedge, confirming the back-arc extension of the Northern Aegean during the Miocene and possibly to mantle delamination in the western Anatolia region.

Acknowledgments

This work is part of the first author's MSc. research, which is financially supported by the «Andreas Mentzelopoulos Foundation».

How to cite: Kalantzi, L., Giamas, V., Koutsovitis, P., Petrounias, P., Hauzenberger, C., and Ntaflos, T.: Miocene basaltic lavas from Chios Island: Petrogenetic implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6324, https://doi.org/10.5194/egusphere-egu24-6324, 2024.

EGU24-7019 | ECS | Posters on site | GMPV10.1

Mapping Global Lithospheric Mantle Pressure-Temperature Conditions by Machine Learning-Based Thermobarometry 

Chenyang Ye, Ben Qin, Jingao Liu, Shichun Huang, Shunguo Wang, and Johnny Zhangzhou

Understanding the temperature and pressure within Earth's lithospheric mantle is crucial for comprehending the dynamics of Earth's interior, its geochemical and geophysical properties, as well as their influence on magma formation and the stability of cratons. While traditional mineral-based thermobarometers have provided valuable insights in estimating temperature and pressure, their reliance on specific mineral pairs and reactions limits their global applicability. Furthermore, as a type of high-dimensional data, mineral compositions have complex relationships that are difficult to capture by conventional methods, and these conventional methods are prone to overfitting, which can produce inaccurate results in certain cases. Our work introduces a new method using XGBoost to develop machine learning-based thermometers and barometers. These models are trained on a comprehensive dataset from 985 high-temperature and high-pressure experiments. This approach is designed to fully leverage the potential of high-dimensional data, offering more precise and widely applicable estimations while also preventing overfitting inherent in traditional methods. Comparison between machine learning models and classic thermobarometer reveals that the machine learning models significantly improve the accuracy in predicting temperature and pressure. This improvement can be attributed to the capability of machine learning models in processing the high-dimensional data of mineral pairs. The global application of these machine learning models has enabled a re-evaluation of the mantle's thermal conditions across diverse cratons. Most notably, the depth estimations to the lithosphere-asthenosphere boundary using machine learning thermobarometry typically exceed seismic measurements by approximately 40 km. This discrepancy suggests the presence of melt-bearing zones at the lithosphere-asthenosphere boundary.

How to cite: Ye, C., Qin, B., Liu, J., Huang, S., Wang, S., and Zhangzhou, J.: Mapping Global Lithospheric Mantle Pressure-Temperature Conditions by Machine Learning-Based Thermobarometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7019, https://doi.org/10.5194/egusphere-egu24-7019, 2024.

The Spongtang Ophiolite positioned along the Indus Suture Zone (ISZ) in Ladakh, NW Himalaya, stands as a key geological site for unraveling the origin and tectonic evolution of serpentinized ultramafic rocks. The petrographic study of highly serpentinized ultramafic rocks is characterized by presence of relict olivines and orthopyroxenes exhibiting porphyroclastic texture. Orthopyroxene grains exhibit bastite texture pseudomorphing the primary relict grains and are altered along their rims to form lizardite. Olivine grains have been mostly altered to lizardite having mesh and hourglass texture and show characteristic peaks at 230 cm-1, 383 cm-1 and 692 cm-1 under Raman spectroscopy. Chrysotiles are observed to have fibrous vein cross-cutting relict orthopyroxene and olivine grains and show peaks at around 135 cm-1, 232 cm-1, 385 cm-1 and 694 cm-1. Antigorites show interlocking to interpenetrating planar texture peaking at 229 cm-1, 377 cm-1 and 687 cm-1. All these major phases are associated with minor brucite, indicating initial stage of serpentinization, and showing characteristic peak at 276 cm-1 and 442 cm-1, 721 cm-1 and 1086 cm-1. Magnetites are formed as alteration products along the rims of chromites and within the serpentine veins indicating mature stage of serpentinization. Lizardite and chrysotile commonly occur during sea floor serpentinization at temperature condition ranging between 50-400˚C. Antigorite mostly occurs in a subduction setting and formed at temperature between 300-600˚C. Mineral chemistry data of serpentines exhibit wide variation in MgO (8.66 wt. % to 27.20 wt. %) and FeO (4.10 wt. % to 12.26 wt. %). However, SiO2 (43 wt. % to 40.82 wt. %) and Al2O3 (0.16 wt. % to 1.07 wt. %) content in serpentines varies within a small range indicating that Si and Al are relatively immobile compared to Mg and Fe during serpentinization. The crosscutting brucite veins have high MgO and FeO composition of 50.53 wt. % and 16.56 wt. % respectively. Mg# of serpentines vary between 0.80 to 0.85, which is much lower than olivines (Mg# = 0.91-0.92) and pyroxenes (Mg# = 0.91-0.97) indicates that magnesium loss has been taken place during serpentinization from the primary minerals. High CaO (22.84 wt. % to 24.73 wt. %) content in diopside grains than the surrounding serpentine grains (0.19 wt. % to 0.55 wt. %) implies that Ca has been removed from the serpentines during serpentinization. The base metal sulfide (BMS) mineral assemblages in serpentinized Spongtang ultramafics are dominated by presence of pyrrhotite, pentlandite, awaruite, magnetite and a few Cu-Fe-Ni alloys. Pyrrhotite, pentlandite and awaruite occur together in serpentine mesh centers and indicate presence of reducing condition at low water-rock ratio during their mineralization. Magnetites formed within serpentinized veins suggest a high water-rock condition leading to a more oxidizing environment.

How to cite: Nayak, B. R. and Ovung, T. N.: Geochemical effects of hydrothermal alteration in the Neotethyan oceanic lithosphere: inferences from the serpentinized mantle rocks of the Spongtang ophiolite, Ladakh, NW Himalaya, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7131, https://doi.org/10.5194/egusphere-egu24-7131, 2024.

EGU24-8393 | Posters virtual | GMPV10.1

High-Cr and High Al chromite from the Nidar Ophiolite Suite, Ladakh, India: implications for its petrogenesis and tectonic evolution 

Alok Kumar, Kalpajyoti Barman, Annapurna Verma, Prasenjit Barman, Vivek Prakash Malviya, and Petros Koutsovitis

The Nidar Ophiolite Suite (NOS) is well exposed in the Indus Suture Zone that separates the Indian plate in the south from Asia to the north, where the ophiolite sequence is best exposed in the Nidar Valley and the outcrop is elongated NW-SE along the regional tectonic trend. The Nidar ophiolite contains both mantle and crustal sections. The mantle section includes ultramafic rocks, namely lherzolite, harzburgite, dunite and serpentinized peridotite with chromite. In the present study, our focus is on chromium-spinel (chromite), which is a common mineral in ophiolitic rocks, and the study of this mineral from the mantle sections of NOS ophiolites can shed light on their petrogenetic origin and tectonic setting.
NOS contains disseminated chromite grains in mantle harzburgites and podiform chromitites associated with dunites and serpentinized peridotites. Due to alteration, most chromite grains display compositional zoning, but the fresh cores preserve primary igneous compositions. Podiform chromitites in the NOS dunites and serpentinized peridotites are compositionally similar to typical ophiolitic chromitites elsewhere. NOS chromite samples exhibit two clusters based on Mg and Cr numbers, indicating two different chromite formation stages.
They are in the initial chromite precipitating stage and later form chromite pods due to the accumulation of chromite crystal precipitation. Chromite from can be texturally and chemically classified into two main types: primary high-Al (spinel Cr# < 0.67) and high-Cr (spinel Cr# > 0.75) chromite. High Cr/Al ratios of the investigated spinel cores (Cr# 0.7– 0.81) point to a higher degree of partial melting of the depleted mantle source. Low (Cr# 0.27-0.4) indicates a lower degree of partial melting. MORB-like tholeiitic melt generated during proto-forearc spreading at the onset of subduction leads to the generation of high-Al chromite. In contrast, the latter was formed from boninitic melts resulting from the high degree melting of the sub-arc depleted mantle in slab-derived fluids at a mature-arc stage.
However, chromite grains in the peridotites show mixed MORB and arc signatures. Thus, the mineralogy and geochemistry of the NOS peridotites suggest that the chromite in the NOS formed in a forearc tectonic setting during a reaction between boninitic melts and MORB-type harzburgite in a supra-subduction zone (SSZ) mantle wedge.

How to cite: Kumar, A., Barman, K., Verma, A., Barman, P., Malviya, V. P., and Koutsovitis, P.: High-Cr and High Al chromite from the Nidar Ophiolite Suite, Ladakh, India: implications for its petrogenesis and tectonic evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8393, https://doi.org/10.5194/egusphere-egu24-8393, 2024.

EGU24-8658 | Posters on site | GMPV10.1

Insight into lithospheric mantle beneath Devès volcanic field recorded by xenoliths from Mt. Coupet (Massif Central, France): preliminary data 

Hubert Mazurek, Magdalena Matusiak-Małek, Jacek Puziewicz, Sonja Aulbach, and Theodoros Ntaflos

Mafic volcanic rocks occurring in Devès volcanic field (3.5 – 0.5 Ma) are rich in peridotitic xenoliths sampling the southern domain of the French Massif Central (FMC). The origin of the relative fertile composition of the continental lithospheric mantle (CLM) beneath FMC is widely discussed in literature and two competing major mechanisms are proposed: 1) extraction of small amounts of partial melt(s), 2) refertilization by upwelling asthenospheric melts [1, 2]. Data from xenoliths at individual localities contribute to this discussion, providing insight into the local conditions of CLM and documenting its regional variability. In this study, we present major and trace elements chemistry of peridotites from Mt. Coupet xenolith suite.

Mt. Coupet peridotites (n = 24) are represented by porphyroclastic to fine–granular lherzolites, which are characterized by within-sample chemical homogeneity. Between samples, olivine Fo varies from 88.63 to 90.85. The Mg# and Al content in orthopyroxene (Opx) are: 0.90 – 0.92 and 0.12 – 0.20 a pfu, respectively. In clinopyroxene (Cpx), Mg# is 0.89 – 0.94 and Al content is 0.11 – 0.32 a pfu. In spinel, Cr# and Mg# are: 0.04 – 0.39 and 0.62 – 0.80, respectively. The REE patterns in Cpx vary, but are always above PM values (in 10 samples analyzed). Based on these patterns, three groups are recognized: (1) LREE–depleted, (2) LREE–enriched, and (3) spoon–shaped (i.e. LREE-enriched with inflection from La to Sm). Other trace elements contents, e.g. U, Th, Nb, Ta, Ti and Sr also differ between samples. Only 10 of the 24 samples are in major-element chemical equilibrium based on Opx–Cpx thermometry [3]. Thus, calculated temperatures are: 900 – 1070 ℃, suggesting sampling of a considerable depth interval if equilibrated to a conductive geotherm. No relationship between textures, geochemistry and thermometry were observed. By analogy to literature data [2, 4] we assume that the Mt. Coupet xenolith suite represents lithospheric mantle typical for the southern domain in FMC. Studies of REE and trace elements on greater number of samples from Mt. Coupet are, however, required to provide more profound interpretation which could contribute to the discussion on the structure and thermochemical evolution of CLM beneath FMC.

Funding. We gratefully acknowledge funding by the project of Polish National Centre of Research 2021/41/B/ST10/00900 to JP.

 

[1] Lenoir et al. (2000). EPSL 181, 359-375.

[2] Puziewicz et al. (2020). Lithos 362–363, 105467.

[3] Brey and Köhler (1990). JoP 31, 1353-1378.

[4] Uenver-Thiele et al. JoP 58, No. 3, 395–422.

How to cite: Mazurek, H., Matusiak-Małek, M., Puziewicz, J., Aulbach, S., and Ntaflos, T.: Insight into lithospheric mantle beneath Devès volcanic field recorded by xenoliths from Mt. Coupet (Massif Central, France): preliminary data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8658, https://doi.org/10.5194/egusphere-egu24-8658, 2024.

EGU24-8867 | ECS | Posters virtual | GMPV10.1

Nature and evolution of the Tethyan Mantle evidenced by the Dras peridotites, Ladakh Himalayas, India. 

Shivani Harshe, Mallika Jonnalagadda, Mathieu Benoit, Raymond Duraiswami, Michel Grégoire, and Nitin Karmalkar

Prominent exposures of mantle rocks in the form of peridotites are observed extending in the E-W direction having a maximum width of 1.5km at the Dras village, Ladakh, India. The Dras peridotites are mainly dunites bearing chromite mineralization with minor harzburgites and wehrlites. The peridotites are emplaced within the Dras volcanics along with gabbros and radiolarian cherts. They display protogranular textures grading into equigranular mosaic textures typical of mantle peridotites. In dunites, olivines exhibit straight boundaries meeting at 120⁰ indicating recrystallization. Spinels associated with dunites are disseminated as tiny inclusions and at places they are lodged on olivine triple junctions. Porphyroclastic olivine in the harzburgites display kink bands whereas orthopyroxenes (enstatite) in harzburgites are subhedral with exsolution lamellae of clinopyroxene (dioside). Overall textures suggest that the peridotites have undergone progressive deep-seated deformation and solid-state recrystallization. The chromite mineralization associated with dunites displays a variety of structures viz. banded, lenticular, pull-apart, schlieren, massive, disseminated etc. Magnesite veins forming an intricate network in dunites are observed.  

Geochemically, the peridotites are relatively fresh (LOI - 0.1 wt % to 5 wt %) with Mg# between 89 and 91, comparable with residual oceanic peridotites. Major element chemistry of the peridotites indicates they are abyssal peridotites, however, depleted REEs, trace elemental concentrations along with enriched LILEs, especially Cs and Nb-Ta and Zr-Hf anomalies indicate formation in a subduction setting. Olivines contain Mg-Cr-rich and Fe-poor rims compared to the cores. Spinels in dunites are chromites with Cr# 68-82 and Mg# 34-48 whereas, in harzburgites, spinels are magnesio-chromites with Cr# 44-55 and Mg# 56-62. Spinel and olivine data suggest that dunites have undergone very high degrees of partial melting about 35% possibly in the supra-subduction zone (SSZ) setting and may have interacted with boninite-like melts.  Harzburgites, on the contrary, are formed by lower degrees of partial melting ranging from 20-25%. However, when remodelled using the clinopyroxene trace element concentrations, the clinopyroxenes from harzburgites suggest 15% to 23% degrees of partial melting. Temperature estimates calculated on select mineral pairs yield temperatures of 816⁰C to 1046⁰C for the peridotites. Distinct petrological and geochemical signatures displayed by the rocks in the present study indicate that the Dras samples show mixed affinities with harzburgites formed at MOR setting whereas dunites being ultra-depleted and refractory owing to higher degrees of partial melting were modified in an SSZ environment.

Keywords: Dras, peridotites, mantle, dunite, chromite mineralization, Ladakh.

How to cite: Harshe, S., Jonnalagadda, M., Benoit, M., Duraiswami, R., Grégoire, M., and Karmalkar, N.: Nature and evolution of the Tethyan Mantle evidenced by the Dras peridotites, Ladakh Himalayas, India., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8867, https://doi.org/10.5194/egusphere-egu24-8867, 2024.

EGU24-11601 | Posters on site | GMPV10.1

A petrogenetic approach on the St. Martin/Maarten granitoids (Lesser Antilles Arc) and associated mantle processes   

Petros Koutsovitis, Michiel J. van der Meulen, Tirza van Daalen, Pavlos Tyrologou, Nikolaos Koukouzas, Alkiviadis Sideridis, Christos Karkalis, Michel Grégoire, Petros Petrounias, Theodoros Ntaflos, and Konstantinos Lentas

In St. Martin, the Oligocene granitoids comprise granodiorites, leucotonalites, melatonalites and Qz-monzodiorites. Tonalites are low-K, whereas granodiorites and Qz-monzodiorites are related with calc-alkaline suites. Mineralogical, geochemical and Sr-Nd isotopic data denote that most rocks are I-type calc-alkaline, except for the melatonalites that seemingly resemble peraluminous S-type granitoids. The melatonalites display the lowest Al2O3/TiO2 and highest CaO/Na2O ratios, pointing to high temperature conditions. Various geothermometry applications, which include Ti-in-zircon thermometry reveal high generated temperatures for the melatonalites, exceeding by ~100 °C those calculated for the other granitoids. Regarding the granodiorites (Type-I low REE; Type-II high REE), Type-II are associated with higher temperature conditions by ~70 °C. Zircon saturation thermometry also show higher crystallization temperatures for the melatonalites and Type-II granodiorites. Thermobarometric results elucidated from mineral chemistry and bulk-rock geochemical point to  higher temperature and pressure crystallization conditions for the melatonalites compared to the leucotonalites and granodiorites. The granitoids were affected by extensive differentiation processes; plagioclase preferably fractionated in the Type-I granodiorites; Type-II mainly involved K-feldspar removal. Fluctuation of hydrous and slab-derived fluid fluxes  contributed to magma differentiation as inferred by the Th/Nb and Ba/La ratios, with hydrous-saturated conditions favouring formation of granodiorites rather than leucotonalites.

Melatonalites and Type-II granodiorites likely formed at proto-arc settings, with melting of a fertile mantle during subduction initiation. Melatonalites may have involved magma mixing via interaction of a hotspot plume within the forearc mantle, as denoted by geochemical and geothermometry results. The geochemical features of the Type-II granodiorites likely reflect formation at the early subduction stages, associated with a fertile source.

Reference: Koutsovitis et al. 2024. Granitoids from St. Martin/Maarten Island, Caribbean: Insights on the role of Mantle processes in the Lesser Antilles Arc. Lithos (Under Review).

How to cite: Koutsovitis, P., van der Meulen, M. J., van Daalen, T., Tyrologou, P., Koukouzas, N., Sideridis, A., Karkalis, C., Grégoire, M., Petrounias, P., Ntaflos, T., and Lentas, K.: A petrogenetic approach on the St. Martin/Maarten granitoids (Lesser Antilles Arc) and associated mantle processes  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11601, https://doi.org/10.5194/egusphere-egu24-11601, 2024.

EGU24-13712 | ECS | Posters on site | GMPV10.1

Geochemistry and Melt Inclusion study of Peridotite Xenoliths from Sinsanri, Jeju, South Korea 

Naing Aung Khant, Han-Sun Ryu, Jinah Moon, and Heejung Kim*

The Sinsanri region of Jeju Island, South Korea, is renowned for its abundant xenoliths, making it one of the prime locations for their occurrence. Jeju Island itself is a Cenozoic intraplate volcano situated in East Asia. A variety of xenolith types such as Spinel Lherzolite, Spinel Harzburgite to Wehrlite are entrapped in Quaternary intraplate alkali basalts on Sinsanri, Jeju Island, South Korea, during the first and second eruption episodes of the Quaternary Volcanic Activity.  Here we report the major element composition of the xenoliths, including the first Raman spectroscopy analysis of the melt inclusion inside olivine to constrain the post-entrapment depth and the latest recrystallizing depth of the melt inclusion itself.  The prominent xenoliths are spinel lherzolite, showing transitions between proto-granular textures and porphyroclastic textures. Mg# ranges from 73.4 to 93.8 in the Sinsanri xenolith’s samples. The spinel lherzolite xenoliths originated at pressure of 15kb with an equilibrium temperature ranging from 922°C.  The size of the CO2 rich melt inclusion entrapped inside the mantle peridotite xenoliths ranges from 20 to 40 µm.  The densities of CO2 melt inclusion were measured to be between 302.8516 kg/m³ and 972.4025 kg/m³.  Most of the melt inclusions inside the xenoliths may have formed while they are ascending to the surface together with the host basalt.  The post-entrapment depth is calculated using the equilibrium temperature of the olivine mineral, which caused the most melt inclusion.  It can be estimated that the post-entrapment depth of the CO2 melt inclusion of the Sinsanri is 86 MPa. The Sinsanri xenoliths are predominantly formed at relatively lower temperatures and pressures.

Acknowledgement 
This research was funded by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (grant numbers 2019R1I1A2A01057002 and 2019R1A6A1A03033167); and Korea Ministry of Environment as “The SS (Surface Soil conservation and management) projects; 2019002820004”.

How to cite: Khant, N. A., Ryu, H.-S., Moon, J., and Kim*, H.: Geochemistry and Melt Inclusion study of Peridotite Xenoliths from Sinsanri, Jeju, South Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13712, https://doi.org/10.5194/egusphere-egu24-13712, 2024.

Upper mantle rocks from tectonically emplaced fragments of the oceanic lithosphere are generally considered to represent variably depleted residues of the oceanic upper mantle remaining after mantle melting and crust-mantle segregation. Geochemical data of these mantle rocks and their compositions of mineral phases are pondered as a powerful petrogenetic indicator and their chemical compositions are dependent on the conditions and degree of partial melting and melt-rock interactions and also contribute to our understanding of the original tectonic setting of lithosphere generation. The Neo-Tethyan ophiolites of the Indo-Myanmar Orogenic Belt (IMOB), northeast India which lie along the southern extension of the Indus-Tsangpo Suture Zone (ITSZ) are investigated through the mantle-derived peridotite sequence. The lithology of the IMOB comprises ultramafic tectonic (dunite–harzburgite–lherzolite), ultramafic–mafic cumulates (pyroxenite–gabbro), mafic intrusives, volcanic, and volcano-clastics dominated by basalt, spilite, and marine sediments. A wide range of chemical compositions is observed in the mantle sequence of the IMOB ophiolites. Lherzolites display low Cr# (0.12-0.26) and TiO2 (<0.11) associated with high Mg# [Mg/(Mg+Fet] (0.69-0.76) in the Cr-spinels present in them. They represent the residual product of a fertile mantle that underwent low-degree partial melting (2-10%) in a divergent mid-ocean ridge (MOR) tectonic setting. Conversely, the harzburgites and dunites have high Cr# (0.84–0.90) and low TiO2 (< 0.06 wt%) Cr-spinels and exhibit slightly U-shaped REE distributions indicating their derivation from a highly depleted mantle source. The dunite is composed of a very refractory olivine-spinel assemblage (Fo: 92.1-93.6; Cr#: 71-83), corroborating a boninitic parentage, with influence from melt-rock interactions. The NMO also hosts both refractory grade high-Al chromitites (0.46 < Cr# < 0.53) and metallurgical grade high-Cr chromitites (0.71 < Cr# < 0.79). The high-Al chromitites originated from MORB-like melts whereas high-Cr chromitites were crystallized from a boninitic melt. The available isotopic ages reveal two episodes of the IMOB ophiolites formation at 148 Ma (K–Ar ages) and 118-117 Ma (U–Pb age). Upper mantle rocks show lower concentration of PGE (Rh < 2 ppb; Pd < 25 ppb; Re < 16 ppb; Pt = < 10 ppb; Au < 28 ppb; Os < 9 ppb; Ir < 3 ppb; Ru = 5-11 ppb). And the total PGE content (60-190 ppb) of the high-Al chromitites is less as compared with the total PGE content (118-2341 ppb) in high-Cr chromitites. The occurrence of both MOR and SSZ types of melting regimes indicates that the peridotites along with chromitites in the IMOB ophiolites formed at different stages of the pre-subduction period and subduction, respectively. Thus, we argue that the upper mantle of the NMO of the IMOB has been modified by a substantial amount of supra-subduction zone components after initially being formed in a mid-ocean ridge tectonic environment supporting multistage melting and melt-rock reaction processes.

How to cite: Chaubey, M. and Singh, A. K.: Geochemical Insights into Neo-Tethyan Ophiolites of Indo-Myanmar Orogenic Belt, Northeast India: Multistage Melting and Supra-Subduction Zone Modification of Upper Mantle Rocks., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15695, https://doi.org/10.5194/egusphere-egu24-15695, 2024.

EGU24-17699 | Posters on site | GMPV10.1

Micro-heterogeneities in lithospheric mantle evidenced by clinopyroxene forming peridotitic xenoliths from S Sweden and French Massif Central 

Magdalena Matusiak-Małek, Małgorzata Ziobro-Mikrut, Jakub Mikrut, Daniel Buczko, Jacek Puziewicz, Theodoros Ntaflos, Sonja Aulbach, Michel Grégoire, and Leif Johansson

Studies on mantle xenoliths evidence heterogeneities occurring in scale from single localities to large geological units. Variations of chemical composition (exceeding analytical uncertainty) occur also within single crystals, as well-defined zoning or as patchy zones. Whereas mantle-derived melts average out such micro-heterogeneities, in-situ study of mantle xenoliths allows to probe their extent and thereby unveil processes affecting the mineralogical and compositional evolution of the mantle lithosphere. Here, we present different types of micro-heterogeneities recorded by clinopyroxene and associated phases from xenolithic mantle peridotites from Sweden (Scania) and the French Massif Central (Mt. Briançon).

Micro-heterogeneities in clinopyroxene occur in only one out of five types of peridotites from Scania and are mirrored by contents of major and trace elements which in general vary between cores and rims of grains, however the composition of cores may also be not homogenous. Cores of clinopyroxene crystals containing oriented lamellae of spinel are enriched in Cr (0.033-0.035 vs. 0.028-0.02 afpu in Cr-poor parts of cores) in 10-100 µm thick layers parallel to the elongation of the spinel crystals. Variations in Cr content are not reflected in trace element compositions. Furthermore, margins and areas along cracks in some clinopyroxene grains (both, lamellae-bearing and lamellae-free), are enriched in Al (0.195-0.206 vs. 0.159-0.196 afpu in unaffected rims), Cr (0.026-0.032 vs. 0.018-0.031 afpu in unaffected rims) as well as in LREE, Zr, Hf, and Ti, the latter recorded also in orthopyroxene.

In Mt. Briançon mantle lherzolites, chemically heterogeneous clinopyroxene occurs in ~14% of the studied xenoliths. In some samples, the Mg# of pyroxenes and olivine Fo change gradually across a petrographic section from 0.87 to 0.89 and from 86.5 to 89.0%, respectively. The REE patterns of clinopyroxene are homogeneous at the grain scale and vary among the grains from spoon-shaped to LREE-enriched, but with no correlation to Mg# values. Another type of heterogeneity is evidenced by higher (by 0.01-0.03) values of Mg# (0.89-0.91) and contents of Al (0.245-0.252 vs 0.226-0.232 apfu in rims) and Cr (0.037-0.038 vs 0.028-0.033 apfu in rims) in cores than in rims of the same clinopyroxene grain. In those samples, clinopyroxene rims are LREE-enriched, whereas REE patterns in cores vary from spoon-shaped to LREE-enriched.

 

The heterogeneities in cores of lamellae-bearing crystals of clinopyroxene from Sweden result from incomplete exsolution of Cr-rich spinel from the structure of clinopyroxene, while the enrichment in Al, Cr and trace elements evidences infiltration of silicate melts along margins and cracks in grains. The section-scale heterogeneities in xenoliths from Mt. Briançon document chromatographic effects of alkaline silicate metasomatism that modifies spoon-shaped REE clinopyroxene patterns to LREE-enriched ones. The LREE-enrichment of clinopyroxene rims is a record of the early stage of this process. The data unveil the dynamic nature of lithospheric mantle in terms of chemical composition and texture (e.g., exsolution) due to varying degrees of metasomatism and emphasize that detailed in-situ studies of mantle phases are necessary to fully understand Earth’s evolution.  

Funded by Polish National Science Centre grants no. UMO-2016/23/B/ST10/01905, UMO-2018/29/N/ST10/00259 and 2021/41/B/ST10/00900.

How to cite: Matusiak-Małek, M., Ziobro-Mikrut, M., Mikrut, J., Buczko, D., Puziewicz, J., Ntaflos, T., Aulbach, S., Grégoire, M., and Johansson, L.: Micro-heterogeneities in lithospheric mantle evidenced by clinopyroxene forming peridotitic xenoliths from S Sweden and French Massif Central, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17699, https://doi.org/10.5194/egusphere-egu24-17699, 2024.

EGU24-20036 | Posters on site | GMPV10.1

Petrology and fluid inclusions geochemistry of ultramafic xenoliths from Mayotte and the origin of the Comoros Archipelago 

Barbara Faccini, Luca Faccincani, Andrea Luca Rizzo, Federico Casetta, Nicolò Nardini, Marco Liuzzo, Andrea Di Muro, and Massimo Coltorti

Ultramafic xenoliths provide valuable insights into the physico-chemical, compositional and thermal characteristics of Earth’s mantle along with its heterogeneities. Integrating petrography and mineral chemistry data with the determination of volatile concentrations and isotopic fingerprints in fluid inclusions (FI) in these xenoliths has become the state-of-the-art approach, as it provides not only important information on the nature and evolution of the lithospheric mantle, in terms of melting and metasomatic processes, but also illustrates the storage and migration pathways of volatiles throughout the lithosphere. This tandem approach makes the Comoros Archipelago (Mozambique Channel, Western Indian Ocean) ideal candidates to explore, because the characteristics of the local lithosphere are intimately tied to the complex regional geodynamic setting. Indeed, the origin of the Comoros magmatism remains enigmatic and controversial despite extensive documentation in the literature, as it has been attributed to either a plume-related hot spot or to a passive response to lithospheric break-up.

In this study, we investigate a unique suite of ultramafic xenoliths from Mayotte island by combining petrographic observation, mineral phase major and trace element analysis with the geochemistry of noble gases (He, Ar, Ne) and CO2 hosted in olivine (ol), orthopyroxene (opx) and clinopyroxene (cpx) FI. Mineral major elements results show refractory compositions in terms of MgO (Mg#Ol > 90.5, Mg#Opx > 91 and Mg#Cpx > 91.5) and Al2O3 contents (ranging from about 1.60 to 3.00 wt.% for opx and from 2.50 to 3.60 wt.% for cpx, respectively), with Cr# of spinel falling between about 0.4 and 0.55. Overall, these features indicate that the local lithosphere experienced relatively high degrees of melting, from ~20% to 25%. This is also supported by highly depleted chondrite-normalized rare earth element (REE) patterns for cpx, where HREE are roughly (1.5)N.

Volatile concentrations and isotopic fingerprints in FI hosted in Mayotte xenoliths are variable, with CO2 standing out as the most abundant gas species. The air-corrected 3He/4He isotopic ratios (5.6 to 6.8 Ra) are intermediate between the typical signatures of MORB (8±1 Ra) and the SCLM (6.1±2.1 Ra) mantle, as measured in local subaerial (Liuzzo et al., 2021) and submarine (Fani Maoré Seamount, Mastin et al., 2023) gas emissions. The relationships between 3He/4He and the extrapolated air-free mantle 21Ne/22Ne ratios, together with 40Ar/36Ar versus 3He/36Ar systematics, suggest a dominating MORB-like component in the upper mantle below the Comoros archipelago, mixed with recycled crustal and atmospheric components, in agreement with recent data of ultramafic xenoliths from Grande Comore island (Ventura Bordenca et al., 2023).

 

References

Bordenca, C.V., Faccini, B., Caracausi, A., et al., 2023. Geochemical evidence for a lithospheric origin of the Comoros Archipelago (Indian Ocean) as revealed by ultramafic mantle xenoliths from La Grille volcano. Lithos, 462, 107406.

Liuzzo, M., Di Muro, A., Rizzo, A.L., et al., 2021. Gas geochemistry at Grande Comore and Mayotte volcanic islands (Comoros archipelago), Indian Ocean. Geochemistry, Geophysics, Geosystems, 22, e2021GC009870.

Mastin, M., Cathalot, C., Fandino, et al., 2023. Strong geochemical anomalies following active submarine eruption offshore Mayotte. Chemical Geology, 640, 121739.

How to cite: Faccini, B., Faccincani, L., Rizzo, A. L., Casetta, F., Nardini, N., Liuzzo, M., Di Muro, A., and Coltorti, M.: Petrology and fluid inclusions geochemistry of ultramafic xenoliths from Mayotte and the origin of the Comoros Archipelago, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20036, https://doi.org/10.5194/egusphere-egu24-20036, 2024.

EGU24-21219 | Posters on site | GMPV10.1

The origin and tectonic evolution of Hongguleleng ophiolite, Western Junggar, southwestern Central Asian Orogenic Belt 

Zhengyu Yang, Riccardo Tribuzio, Xiaohan Gong, Qisong Luo, and Jifeng Xu

We present a petrological and geochemical study of the Hongguleleng ophiolite in Western Junggar of Xinjiang (Southwestern Central Asian Orogenic Belt), which contains the classic Penrose-type ophiolite stratigraphic units. The ophiolite actually includes mantle spinel harzburgites, olivine-rich troctolites within the harzburgites, layered troctolites, plagioclase-bearing wehrlites, olivine gabbros, gabbros and a minor basalt proportion. Compared to other ophiolites from the accretionary orogenic belt, such as those from Tianshan and Inner Mongolia, the lower crust sequence of the Hongguleleng ophiolite is well preserved. The Hongguleleng spinel harzburgite is highly depleted, for instance as documented by the low whole-rock Al2O3 and CaO contents, the low REE concentrations of clinopyroxene, and the high Cr# [molar Cr/(Cr+Al)] of spinel. Overall, the harzburgite chemical compositions document that these mantle peridotites underwent a high degree of partial melting, similar to mantle peridotites from supra-subduction zones. Remarkably, the trace element signature of clinopyroxene is similar in harzburgites and included olivine-rich troctolites, thereby providing evidence for formation of the olivine-rich troctolites by melt-peridotite reaction. On the other hand, the trace element compositions of clinopyroxene from other lower crustal rocks, including the plagioclase-bearing wehrlites, may be reconciled with crystallization from MORB-type melts. However, these clinopyroxenes locally display a significant enrichment in La, Ce and Pb, which could reflect either contamination of the MORB-type melts by continental crust material, or late infiltration of a melt enriched in La-Ce-Pb through the lower ophiolitic crust. To conclude, the Hongguleleng ophiolite shares close similarities to oceanic lithospheres formed at supra-subduction zones. Along with the coeval ophiolites from the Junggar and Tianshan area, the Hongguleleng ophiolites might represent the remnants of the Junggar Ocean during the initiation of subduction.

How to cite: Yang, Z., Tribuzio, R., Gong, X., Luo, Q., and Xu, J.: The origin and tectonic evolution of Hongguleleng ophiolite, Western Junggar, southwestern Central Asian Orogenic Belt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21219, https://doi.org/10.5194/egusphere-egu24-21219, 2024.

EGU24-418 | ECS | PICO | GMPV10.2

Revealing Redox Variability in the lithospheric mantle: Insights from Mg-chromite inclusions in diamonds from the Udachnaya kimberlite pipes 

antonio angellotti, Giulia Marras, Alla Logvinova, Denis Mikhailenko, and Vincenzo Stagno

The study of mineral inclusions trapped within lithospheric diamonds stands as one of the fundamental approaches to directly study the Earth’s interior, enhancing our comprehension of its chemistry and deep geological processes. The inclusions provide crucial insights into the pressure (P), temperature (T), and redox conditions (fO2) occurring during the diamond nucleation and growth. Among the various mineral inclusions observed in lithospheric diamonds, those characterized by a peridotitic mineral assemblage (P-type), frequently exhibit the presence of Mg-chromite (Stachel et al., 2022) that suggests their involvement in redox-driven diamond formation from CO2-bearing melts. Since the current understanding of the Earth’s interior redox state primarily relies on peridotite samples from the shallow upper mantle based on the Fe3+ content of spinels (Ballhaus et al., 1991), investigating the chemistry of spinel mineral inclusions in diamonds would extend the knowledge of the mantle redox state to greater depths.

 

In this study, we focused on a suite of nine diamonds extracted from the Udachnaya kimberlite pipes, located within the Siberian craton. These diamonds show multiple dark and transparent inclusions with sizes between 30 and 200 µm in diameter. The selected diamonds are polished to expose some of the inclusions. The chemical composition was determined by electron microprobe while textural features were observed by scanning electron microscopy. The Fe3+/ΣFe ratios of both encapsulated and polished inclusions were measured by in situ synchrotron Mössbauer spectroscopy at the ID18 beamline of the ESRF synchrotron (Grenoble, France), employing a 6 x 15 µm2 focused beam.

 

The analyzed Mg-chromites exhibit FeO contents of 15-17 wt% and Cr# and Mg# of 0.85-0.92 and 0.54-0.61, respectively. The Mössbauer data collected on the Mg-chromites show a large variability with Fe3+/ΣFe ratios ranging from 0.07 to 0.28. Interestingly, variable chemical composition for the Mg-chromites among inclusions trapped in the same diamond along with fO2 ranging within 2 log units below the fayalite-magnetite-quartz buffer suggest possible changes in the chemistry of the diamond growth medium providing, therefore, evidence of redox heterogeneities in the lithospheric mantle underneath the Siberian platform.

How to cite: angellotti, A., Marras, G., Logvinova, A., Mikhailenko, D., and Stagno, V.: Revealing Redox Variability in the lithospheric mantle: Insights from Mg-chromite inclusions in diamonds from the Udachnaya kimberlite pipes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-418, https://doi.org/10.5194/egusphere-egu24-418, 2024.

EGU24-2592 | ECS | PICO | GMPV10.2

The redox state of asthenospheric mantle and the onset of melting beneath mid-ocean ridges 

Fangyi zhang, Shaocong Lai, and Vincenzo Stagno

The redox state of the convective asthenospheric mantle governs the speciation of volatile elements, such as carbon, therefore influences the depth at which (redox) melting can occur with implications for seismic signals. Geophysical observations suggest the presence of carbonatite melts at depth of 200–250 km, however, thermodynamic models indicate that the onset of (redox) melting would occur at 100–150 km for a mantle with 3–4 % of Fe3+/∑Fe. Here we present a new oxybarometer based on the V/Sc exchange coefficient between olivine and melt, which is insensitive to surficial alteration, volatile degassing, electron exchange reactions and fractional crystallization. By applying this method to primary mid-ocean ridge basalts (MORBs) from the Southwest Indian Ridge and East Pacific Rise, we demonstrate that the average oxygen fugacity (fo2) of MORBs, corrected for the depth of formation, is 0.88±0.24 log units above the fayalite-magnetite-quartz (FMQ) buffer, which is slightly more oxidized than previously estimated (near FMQ buffer). Our findings indicate that the convective asthenospheric mantle exhibits a higher oxygen fugacity than continental lithospheric mantle. Along an adiabat, carbonatitic melts can form from a CO2-bearing source at depth of 200–250 km explaining, therefore, the electrical conductivity and seismic velocity anomaly of the asthenospheric mantle.

How to cite: zhang, F., Lai, S., and Stagno, V.: The redox state of asthenospheric mantle and the onset of melting beneath mid-ocean ridges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2592, https://doi.org/10.5194/egusphere-egu24-2592, 2024.

EGU24-2982 | PICO | GMPV10.2

Predicting Sulfide Precipitation in Magma Oceans on Earth, Mars, and the Moon Using Machine Learning 

Johnny ZhangZhou, Yuan Li, Proteek Chowdhury, Sayan Sen, Urmi Ghosh, Zheng Xu, Jingao Liu, Zaicong Wang, and James Day

The sulfur content at sulfide saturation (SCSS) in silicate melts plays a pivotal role in governing the behavior of chalcophile elements in planetary magma oceans. Numerous high-pressure experiments have been conducted to determine SCSS, employing various regression methods to capture the thermodynamic characteristics of the system. However, existing empirical equations have shown limited predictive accuracy when applied to laboratory measurements. In this study, we have compiled and analyzed 542 experimental datasets encompassing diverse sulfide and silicate compositions under varying pressure-temperature (P-T) conditions (up to 24 GPa and 2673 K). Employing empirical equations, linear regression, Random Forest algorithms, and a novel hybrid approach combining empirical fits for P-T conditions with Random Forest modeling for compositions, we have developed multiple SCSS models. These models have been rigorously compared with laboratory measurements. Our findings reveal that the Random Forest and hybrid models exhibit exceptional predictive performance (R2 = 0.82–0.91, mean average error [MAE] < 746 ppmw S, residual mean standard error [RMSE] < 972 ppmw S) in comparison to previous empirical models (R2 = 0.28–0.69, MAE = 622–1,170 ppmw S, RMSE = 1,070–1,744 ppmw S). Linear regression falls in between the performance of classical and machine learning models. Furthermore, we have applied our hybrid model to predict SCSS during the solidification of magma oceans on Earth, Mars, and the Moon. A comparison of our model results with expected sulfur contents in residual magma oceans, calculated through mass balance, offers valuable insights. Our analysis confirms that sulfides precipitated during the early accretion phases of Earth and Mars, but not on the Moon. Subsequently, evolving compositions of magma oceans offset increasing sulfur concentrations, preventing sulfide precipitation during intermediate stages of crystallization. Late-stage sulfide precipitation, contributing significantly to the bulk-silicate sulfur abundances of Earth, Mars, and the Moon, occurred at shallow depths (120–220 km, 40–320 km, and <10 km, respectively) within their respective magma oceans. This study sheds light on predicting SCSS under a range of conditions, advancing our understanding of chalcophile element behavior in planetary magma oceans.

How to cite: ZhangZhou, J., Li, Y., Chowdhury, P., Sen, S., Ghosh, U., Xu, Z., Liu, J., Wang, Z., and Day, J.: Predicting Sulfide Precipitation in Magma Oceans on Earth, Mars, and the Moon Using Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2982, https://doi.org/10.5194/egusphere-egu24-2982, 2024.

EGU24-3301 | ECS | PICO | GMPV10.2

Sub-Arc Mantle Redox Evolution since the Archean 

Chun-Tao Liu, Chen-Yang Ye, and Zhou Zhang

The redox state of the sub-arc mantle is critical in contraining the behavior of redox-sensitive elements, particularly volatile species, within the magmatic system. However, the long-term evolution of redox conditions in the sub-arc mantle and its impact on atmospheric oxygen levels remain unclear. In this study, we address two key challenges in understanding the sub-arc mantle redox throughout geological history: 1) the need for more effective methods to identify arc samples in different tectonic settings, and 2) the lack of constraints on the evolution of redox-sensitive trace elements from the mantle source. To overcome these challenges, we used an XGBoost machine learning model trained on multiple elements and elemental ratios (e.g., Nb, Ta, Ti, Pb, Th/Nb, Nb/La, and U/Nb) to accurately classify arc basalts and basalts (N ≈ 14,000) derived from other tectonic settings. Subsequently, we modeled the evolution of trace elements (V, Ti, and Sc) partitioning in the hydrous and dry depleted mantle beneath the arc using non-modal near-fractional melting. Finally, we applied the trained machine learning model and redox-sensitive elemental ratios to a refined global dataset of basalts (N ≈ 19,000) to calculate the redox evolution since 3.4 Ga. Our findings reveal that there have been minimal fluctuations in the melting T-P conditions since 3.4 Ga, indicating a consistent oxidized state in the sub-arc mantle. The average ΔFMQ of 0.96 ± 0.52 (1 SD) observed in our study is similar to that of the modern arc mantle since the early Archean. Interestingly, it is unlikely that the long-term oxidation of the sub-arc mantle has significantly impacted the progressive increase in atmospheric oxygen levels over time.

How to cite: Liu, C.-T., Ye, C.-Y., and Zhang, Z.: Sub-Arc Mantle Redox Evolution since the Archean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3301, https://doi.org/10.5194/egusphere-egu24-3301, 2024.

The aluminum (Al), lithium (Li) and phosphorus (P) in zircon, combining their partitioning coefficients between zircon and silicate melt, may show important insights into the evolution of Earth’s crust and habitability over geological timescales, but their partitioning coefficients have not been experimentally studied in detail. In this study, we conducted high-temperature experiments to constrain the partition coefficients of Al (DAl), Li (DLi) and P (DP) between zircon and silicate melt. Our experiments firstly show the amounts of P has the identifiable effects on DAl and DLi, but not on itself. The positive and negative correlations of DAl and DLi as P content in zircon increasing enables us to constrain the aluminum saturation index (ASI) and Li content of the parental melt of zircon, respectively, by comparing their contents in zircon. The re-evaluated ASI values over time yields two significant increases at 3.6 Ga and 1.0 Ga, whereas, the calculated Li content of Earth’s crust non-linearly decrease with time. Meanwhile, the P content of early Earth’s crust is constrained to 1779 ppm before 3.0 Ga, similar to the present-day crust level of 2052 ppm. These indicate that the global scale tectonic events occurred on the Earth around 3.6 Ga and 1.0 Ga, and that the early Earth could have had a life habitability, and it did not get receded during the terrestrial crust evolution.

How to cite: Shang, S. and Lin, Y.: Re-experimentally constrained aluminum, lithium and phosphorus partitioning between zircon and melt: implication for early Earth’s crust evolution and possible habitability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7525, https://doi.org/10.5194/egusphere-egu24-7525, 2024.

EGU24-7879 | ECS | PICO | GMPV10.2

Quantification of uncertainty related to methane production associated with geogenic hydrogen and carbon dioxide 

Ehsan Ranaee, Fabio Inzoli, Monica Riva, and Alberto Guadagnini

We provide a numerical analysis aimed at quantifying uncertainty associated with methane (CH4) production following geogenic hydrogen (H2) and carbon dioxide (CO2) generation. Our study stems from the observation that naturally generated H2 can potentially be (i) reduced through, e.g., mineral-based (abiotic) geochemical processes and/or (ii) consumed through (biotic) methanogens. Both scenarios yield methane (CH4) as a product. Some studies suggest relying on the H2/CH4 ratio as a straightforward indicator to assess the origin of methane in the subsurface. For example, Oze et al. (2012) rely on laboratory experiments of serpentinization associated with a given temperature/pressure condition and rock/fluid compositions and suggest that values of H2/CH4 larger than 40 are likely to indicate abiotic origin of CH4. Otherwise, values H2/CH4 less than 40 suggest contribution of biotic activity to methane generation. Here, we consider the same types of (abiotic) geochemical reactions analyzed by Oze et al. (2012) and conceptualize the subsurface system as a natural chemical reactor within which a mixture of H2 (generated from serpentinization) and CO2 (generated from carbon-clay-reactions) yields a mixture of H2, CO2, and CH4. Our analysis considers that complete mixing of the various chemical species is attained and that geochemical reactions can be evaluated under thermodynamic equilibrium conditions. We then perform a modeling study framed in a stochastic context and relying on a numerical Monte Carlo framework. We aim at quantifying the way uncertainties associated with hydrogen loss (as reflected through the H2/CH4 ratio) due to geochemical reactions at reservoir equilibrium condition can depend on corresponding uncertainties related to (i) composition of the fluids residing in the system, (ii) depth of a reservoir (i.e., as reflected through temperature/pressure conditions), and (iii) characterization of the thermodynamic equilibrium model. With reference to the latter point, uncertainties in terms of values of reaction equilibrium constants stem from the observation that temperature and pressure values associated with significant burial depths may fall outside ranges of validity of commonly employed thermodynamic databases and typically used geochemical software. Our stochastic simulation results suggest that (on average) almost 43% of native H2 is consumed due to the geochemical reactions analyzed. This would correspond to an average value of H2/CH4 of about 13 (with first and third quantiles corresponding to 7 and 20, respectively). The ensuing sample probability density function of the H2/CH4 ratio displays a clear positive skewness. Our results may practically be used as a simple criterion to identify the probability associated with CH4 production from geochemical processes involving natural H2 under reservoir thermodynamic equilibrium conditions.

Keywords: serpentinization, methane, geochemical reactions, uncertainty quantification, H2/CH4 ratio.

References

Oze, C., Jones, L. C., Goldsmith, J. I., and Rosenbauer, R. J. (2012). Differentiating biotic from abiotic methane genesis in hydrothermally active planetary surfaces. Proceedings of the National Academy of Sciences, 109(25), 9750-9754. https://doi.org/10.1073/pnas.1205223109.

How to cite: Ranaee, E., Inzoli, F., Riva, M., and Guadagnini, A.: Quantification of uncertainty related to methane production associated with geogenic hydrogen and carbon dioxide, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7879, https://doi.org/10.5194/egusphere-egu24-7879, 2024.

EGU24-8063 | ECS | PICO | GMPV10.2

A novel rapid cooling assembly design in a high-pressure Cubic Press apparatus 

Yongjiang Xu, Peiyan Wu, and Yanhao Lin

In traditional high pressure-temperature assembly design, priority has been given to temperature insulation and retention at high pressures. This limits the efficiency of cooling samples at the end of experiments, negatively impacting many studies in the field of high-pressure earth and planetary science. Inefficient cooling of experiments containing molten phases at high temperature leads to the formation of quench textures, which makes it impossible to quantify key compositional parameters of the original molten phase, such as their volatile contents.

Here, we designed a novel, low-cost experimental assembly for rapid cooling in a six-anvil cubic press. This assembly not only retains high heating efficiency and thermal insulation, but also enables a very high cooling rate (~600 °C/s from 1900 °C to the glass transition temperature). Without using expensive materials or external modification of the press, the cooling rate in an assembly (~600 °C/s) with cube lengths of 38.5 mm is about ten times faster than the traditional assembly (~60 °C/s). Experiments have shown that the heterogeneous quenched textures produced with the traditional assembly, does not shown with the novel rapid cooling assembly design.

How to cite: Xu, Y., Wu, P., and Lin, Y.: A novel rapid cooling assembly design in a high-pressure Cubic Press apparatus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8063, https://doi.org/10.5194/egusphere-egu24-8063, 2024.

EGU24-8112 | ECS | PICO | GMPV10.2

Melting the mantle of Mercury and the compositional diversity of the crust 

Peiyan Wu, Yongjiang Xu, Yanhao Lin, Fabrizio Saracino, Olivier Namur, Camille Cartier, and Bernard Charlier

The compositional diversity of the crust of Mercury revealed by NASA’s MESSENGER spacecraft is interpreted to result from partial melting of a heterogeneous sulfur-rich Mercurian mantle. Major magmatic activity and the building of its secondary volcanic crust are restricted to the first billion year of the planet evolution. In order to understand the causes for the production of diverse lavas and the early death of major volcanism, we have performed a suite of high-pressure and high-temperature partial melting experiments under reduced conditions at temperature and pressure conditions relevant the mantle (1450-1750°C; 5, 3.5, and 1.5 GPa) of potential primordial S-free and S-saturated mantles and obtained crystallization sequences, solidus and liquidus of the residual mantle of Mercury with the Mg/Si ratio of 1.02 (Mer8) and 1.35 (Mer15) contains under above conditions. Our experimental data reveal that the majority of chemical composition of the highest Mg/Si region (HMR) on the Mercury’s surface can result from ~25±15 wt.% melting of a deep primitive mantle. Additionally, the possibility that garnet was abundant in the deep mantle could explain that Mercury rocks but the High-Mg province overlap the terrestrial “Al-undepleted” array, consistent with low-pressure melting of a garnet-free mantle.

How to cite: Wu, P., Xu, Y., Lin, Y., Saracino, F., Namur, O., Cartier, C., and Charlier, B.: Melting the mantle of Mercury and the compositional diversity of the crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8112, https://doi.org/10.5194/egusphere-egu24-8112, 2024.

The Mars is thought to have been covered by a deep magma ocean after its formation. In the past, the solidification of this ocean was modeled by one-step experimental1 and numerical models2 assuming a Fe-rich (~18.7 wt% FeO) mantle composition3. Estimates of the mantle composition and depth of the Martian magma ocean were recently updated by using the latest cosmochemical model (~13.7 wt% FeO)4 and the newest seismic observations from the InSight mission (the depth of the mantle, ~1560 km)5. Here, we present an experimental crystallization study of a nominally dry experimental Martian magma ocean (MMO), simulating up to ~50 percent fractional crystallization of the updated MMO composition and refined core-mantle boundary condition. A ‘two-stage’ model of magma ocean solidification is assumed, which features early efficient crystal suspension up to 50% solidification in magma and corresponding equilibrium crystallization, followed by fractional crystallization of the later residual magma ocean. For the first stage experiments at pressures of 1.5, 5, 10, 13 and 16 GPa and a constant temperature were designed to represent MMO equilibrium crystallization. Results indicate formation of a cumulate pile of olivine, orthopyroxene, clinopyroxene, garnet, spinel, periclase and quartz. Our preliminary result significantly differ from the previous experimental and numerical studies1,2, likely due to the updated mantle composition and interior structure of Mars. Further second-stage experiments will start at the averaged residual magma composition resulting from the first stage, and we will provide more detailed results at the conference.

References and Notes

1. Bertka, C. M. & Fei, Y. Mineralogy of the Martian interior up to core-mantle boundary pressures. J. Geophys. Res. Solid Earth 102, 5251–5264 (1997).

2. Elkins-Tanton, L. T., Zaranek, S. E., Parmentier, E. M. & Hess, P. C. Early magnetic field and magmatic activity on Mars from magma ocean cumulate overturn. Earth Planet. Sci. Lett. 236, 1–12 (2005).

3. Dreibus, G. & Wänke, H. Mars, a volatile-rich planet. Meteoritics 20, 367–381(1985).

4. Khan, A., Sossi, P. A., Liebske, C., Rivoldini, A. & Giardini, D. Geophysical and cosmochemical evidence for a volatile-rich Mars. Earth Planet. Sci. Lett. 578, 117330 (2022).

5.  Stähler, S. C. et al. Seismic detection of the martian core. Science 373, 443–448 (2021).

 

How to cite: Wang, X., Lin, Y., and van Westrenen, W.: Solidification evolution of a dry Martian magma ocean: Constraints from high pressure-temperature experimental petrology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8318, https://doi.org/10.5194/egusphere-egu24-8318, 2024.

EGU24-8480 | ECS | PICO | GMPV10.2

Redox heterogeneity in lithospheric mantle evidenced by C-O-H-S fluid inclusions entrapped in Kerguelen mantle-plume associated pyroxenites 

Shubham Choudhary, Renbiao Tao, Souvik Das, Koushik Sen, Jiten Pattnaik, Yuhang Lu, Santosh Kumar, and Fanus Viljoen

The C-O-H-S fluids play a significant role in various geological processes. The participation of these fluids in redox reactions remarkably influences carbonation process, melting behaviour, and physicochemical properties of the mantle rocks. In this study, we report rare, reduced fluid inclusions in shallow upper mantle-derived pyroxenites associated with the Kerguelen mantle plume from Northeast India. Raman spectroscopy reveals primary inclusions of hydrocarbon (CH) fluid and calcite along with the nearly perpendicular exsolution lamellae of magnetite in clinopyroxene (referred to herein as Cpx 1) of these pyroxenites. A rare occurrence of pseudo-secondary polyphase fluid inclusions of hydrogen sulfide (H2S), carbon monoxide (CO), rutile, and calcite was also recorded in other clinopyroxenes (referred to herein as Cpx 2) of these pyroxenites. Mineral chemical data suggests that the studied Cpx are purely diopside and Cpx 1 hosted magnetite exsolutions are coeval with these clinopyroxenes. This is evident from the notable enrichment in MgO in these magnetite exsolutions relative to accessory magnetite, showing that they certainly do not represent a sub-solidus phase. Single Cpx geothermobarometric calculations suggest that these pyroxenites were formed at 1.2- 1.8 GPa pressure and 752- 941 °C temperature. We use a theoretical thermodynamic model to validate our natural observations of fluid inclusions. Overall, our results show that mantle plume-derived oxidized C-O-H-S fluids interacted with crystallizing diopside from pyroxenites in the shallow mantle. During this interaction, these fluids participated in redox reactions leaving the reduced fluid products such as CH, CO and H2S and minerals such as calcite and rutile trapped as co-genetic inclusions along with magnetite exsolutions in host diopsides at oxygen fugacity conditions equivalent to FMQ-2. Therefore, considering the widely accepted fact that the shallow lithospheric mantle is predominantly oxidized, these natural observations of fluid inclusions, for the first time provide direct evidence of redox heterogeneity of the shallow mantle.

 

How to cite: Choudhary, S., Tao, R., Das, S., Sen, K., Pattnaik, J., Lu, Y., Kumar, S., and Viljoen, F.: Redox heterogeneity in lithospheric mantle evidenced by C-O-H-S fluid inclusions entrapped in Kerguelen mantle-plume associated pyroxenites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8480, https://doi.org/10.5194/egusphere-egu24-8480, 2024.

EGU24-18384 | PICO | GMPV10.2

Redox-induced isotope anomalies in the deep Earth 

Mao Tang and Yun Liu

A weakly temperature dependent isotope effect, i.e., the nuclear field shift, can produce isotope anomalies in the deep mantle due to redox condition changes. This effect can produce several to tens of ppm isotope anomalies or mass-independent fractionations at 2000 or even higher temperatures for many heavy metal isotope systems. This effect can be confirmed easily by comparing several isotope anomaly results of the same isotope system. For example, for W isotope anomalies, e.g., 180W and 183W, there are unique relationships between tthem if they are caused by the nuclear field shift effects. This work suggests a method to use heavy metal isotope systems as the tracers to detect the redox changes in the deep mantle. 

How to cite: Tang, M. and Liu, Y.: Redox-induced isotope anomalies in the deep Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18384, https://doi.org/10.5194/egusphere-egu24-18384, 2024.

The redox state of the Earth’s interior (i.e., the oxygen fugacity, fo2) is related to the Fe speciation (Fe2+, Fe3+) in mantle rock-forming minerals and controls the speciation of volatiles like carbon at depth. To date, the fo2 of the lower mantle has been mostly constrained by HP-T experiments, due to the extreme rarity of natural samples represented by mineral inclusions in sub-lithospheric diamonds. Experimental evidence suggests that the lower mantle is reduced and saturated in Fe(-Ni) metal (about 1 wt%). However, coexisting minerals like ferropericlase and bridgmanite are predicted to contain 0.02 and 0.6 of Fe3+ /∑Fe, respectively. A slight increase of Fe3+ /∑Fe (less than 1 wt%) is expected in the case of fo2 > iron-wüstite buffer. This would imply the complete oxidation of Fe(Ni) alloys promoted by reduction of carbonates (either fluids or melts). The finding of carbonates trapped in sub-lithospheric diamonds is natural evidence of the (local) oxidative redox state of the deep and inaccessible lower mantle and this is enhanced by the lack of metallic inclusions coexisting with Fe3+-poor ferropericlase in sublithospheric diamonds. Moreover, the variation of Fe3+ in bridgmanite appears, at least currently, to be better explained by its crystal chemistry while the effect of pressure and fo2 remains unclear, mainly due to the lack of oxybarometers applicable to lower mantle assemblages.

In this study, we combined an experimental investigation of the Fe3+/∑Fe in ferropericlase and bridgmanite equilibrated at known high pressure, temperature and oxygen fugacity conditions with Fe3+ /∑Fe measurements conducted on bridgmanite(-like) and ferropericlase inclusions in sublithospheric diamonds from Rio Sorriso and São Luís (Brazil) and Kankan (Guinea). Some inclusions are composite for which the Fe3+/∑Fe was determined by in situ synchrotron Mössbauer source spectroscopy and the bulk Fe3+ /∑Fe determined.

Our preliminary results show a discrepancy between natural inclusions and experimental products in terms of i) modal abundance of ferropericlase and bridgmanite, likely related to their diverse role in diamond formation (redox) processes; ii) chemical compositions expected for both peridotitic and metabasaltic parageneses; and iii) Fe3+ /∑Fe content.

How to cite: Stagno, V., McCammon, C., Kaminsky, F., and Marras, G.: The redox state of the Earth’s lower mantle: combined evidence from natural mineral inclusions in superdeep diamonds and experimental predictions , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19097, https://doi.org/10.5194/egusphere-egu24-19097, 2024.

EGU24-19755 | PICO | GMPV10.2

Pseudobrookite-based ceramics with low thermal conductivity prepared from Fe-Ti-rich heavy mineral sand concentrate 

Darko Hanžel, Nina Daneu, Tina Radoševič, Slavko Bernik, Matjaž Mazaj, Marjeta Maček Kržmanc, Dejan Verhovšek, Andraž Kocjan, Mirijam Vrabec, Matjaž Spreitzer, and Emmanuel Guilmeau

The potential of using natural Fe-Ti-rich heavy mineral sand, as an abundant, inexpensive, and ecologically acceptable raw material for the processing of pseudobrookite-based ceramics for thermoelectric applications is presented. The as-received raw powder was used in untreated form or after pre-oxidation at 600°C, 700°C, and 800°C for 1h in an air. The starting powders were consolidated into dense compacts via conventional solid-state sintering or spark plasma sintering. The phase composition, ferrous:ferric ratio and microstructural characteristics of the powders and sintered compacts were investigated by XRD, Mössbauer spectroscopy and SEM. The samples with a higher fraction of pseudobrookite exhibit relatively low thermal conductivity ranging between 2 and 3 W m-1 K-1, which is promising for practical thermoelectric applications. The Seebeck coefficient depends on the ferrous:ferric ratio and is rather low, leading to low power factor values for all the samples which will have to be improved for practical applications.

How to cite: Hanžel, D., Daneu, N., Radoševič, T., Bernik, S., Mazaj, M., Maček Kržmanc, M., Verhovšek, D., Kocjan, A., Vrabec, M., Spreitzer, M., and Guilmeau, E.: Pseudobrookite-based ceramics with low thermal conductivity prepared from Fe-Ti-rich heavy mineral sand concentrate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19755, https://doi.org/10.5194/egusphere-egu24-19755, 2024.

EGU24-415 | ECS | Orals | TS8.1

The South Atlantic Magmatic Province: An Integration of Early Cretaceous LIPs in the West Gondwana 

Antomat Avelino de Macedo Filho, Alisson Oliveira, Valdecir Janasi, and Maria Helena Hollanda

Extensive igneous activity, currently identified from NE Brazil and western Africa to the Falkland Islands and South Africa, preceded the fragmentation of the Western Gondwana supercontinent in the Early Cretaceous. The Paraná-Etendeka Magmatic Province (PEMP) is characterized by continental basaltic flows and igneous plumbing systems in SE South America and its African counterpart. In NE Brazil, dyke swarms and sill complexes compose the Equatorial Atlantic Magmatic Province (EQUAMP). A prominent feature of EQUAMP is the Rio Ceará-Mirim dyke swarm, an arcuate igneous plumbing system approximately 1,100 km in length. Aeromagnetic data suggests that the Rio Ceará-Mirim dykes stretch from the corner of South America to the northwest border of the São Francisco Craton. At this point, the dykes shift orientation to the NNW, extending towards the south, where they appear to connect with the Transminas dyke swarm (northern PEMP). The apparent continuity of dykes as a single entity would constitute a massive transcontinental swarm of about 2,300 km. A similar relationship is observed for the Riacho do Cordeiro (southern EQUAMP) and Vitória-Colatina (northern PEMP) dykes, indicating continuity across the São Francisco Craton of about 1,600 km. This study, supported by new petrological, geochemical, isotopic, and geochronological data, combined with geophysical and geodynamical analyses, demonstrates that the Transminas and Vitória-Colatina dyke swarms share the same composition and age as the Rio Ceará-Mirim and Riacho do Cordeiro dyke swarms, respectively. The set of new evidence supports a genetic connection between the PEMP and EQUAMP. Therefore, they can be collectively referred to as a single large igneous province related to the early stage of the South Atlantic rifting process in the West Gondwana realm: The South Atlantic Magmatic Province.

How to cite: Avelino de Macedo Filho, A., Oliveira, A., Janasi, V., and Hollanda, M. H.: The South Atlantic Magmatic Province: An Integration of Early Cretaceous LIPs in the West Gondwana, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-415, https://doi.org/10.5194/egusphere-egu24-415, 2024.

EGU24-1934 | ECS | Posters on site | TS8.1

The hypothesis of a lost Cenozoic “Himalandia” between India and Asia 

Liang Liu, Lijun Liu, Jason Morgan, Yi-Gang Xu, and Ling Chen

            The type of lithosphere subducted between India and Tibet since the Paleocene remains controversial; it has been suggested to be either entirely continental, oceanic, or a mixture of the two. As the subduction history of this lost lithosphere strongly shaped Tibetan intraplate tectonism, we attempt to further constrain its nature and density structure with numerical models that aim to reproduce the observed history of magmatism and crustal thickening in addition to present-day plateau properties between 83˚E and 88˚E. By matching time-evolving geological patterns, here we show that Tibetan tectonism away from the Himalayan syntaxis is consistent with the initial indentation of a craton-like terrane at 55±5 Ma, followed by a buoyant tectonic plate with a thin crust, e.g., a broad continental margin (Himalandia). This new geodynamic scenario can explain the seemingly contradictory observations that had led to competing hypotheses like the subduction of Greater India versus largely oceanic subduction prior to Indian indentation.

How to cite: Liu, L., Liu, L., Morgan, J., Xu, Y.-G., and Chen, L.: The hypothesis of a lost Cenozoic “Himalandia” between India and Asia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1934, https://doi.org/10.5194/egusphere-egu24-1934, 2024.

EGU24-2317 | Posters on site | TS8.1

Rayleigh-wave Ambient Noise Investigation for the OHANA Experiment in the NE Pacific 

Gabi Laske, Grace Atkisson, Sujania Talavera Soza, John Collins, and Donna Blackman

The OHANA experiment comprises a 15-month deployment of 25 broadband ocean bottom seismometers (OBSs) in the northeast Pacific Ocean, about halfway between Hawaii and the North American west coast. The primary objective of this project is to explore the crust, lithosphere and asthenosphere in a 600~km wide region west of the Moonless Mountains, covering mainly 40-to-50 Myr old Pacific lithosphere. A fundamental question to be addressed is whether this particular area has the signature of a typical oceanic lithosphere that has a normal plate cooling history. Alternatively, we seek evidence for a previously proposed reheating process, e.g. resulting from small-scale shallow-mantle convection. 

The new data enhance seismic imaging in a regional as well as in a global context. Regionally, short-period ambient noise and long-period earthquake-derived Rayleigh wave dispersion provide the centerpiece for imaging the crust and upper mantle. In  a top-down approach,
we start with the assembly and analysis of ambient-noise cross-correlation functions between 5 and 25 s. We present an initial assessment of high signal-to-noise quality cross-correlation functions. We derive path-averaged dispersion curves for the fundamental mode and present tomographic images from initial inversions. 

Furthermore, our cross-correlation functions contain prominent waveforms from overtones that can help improve resolution as a function of depth.

How to cite: Laske, G., Atkisson, G., Talavera Soza, S., Collins, J., and Blackman, D.: Rayleigh-wave Ambient Noise Investigation for the OHANA Experiment in the NE Pacific, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2317, https://doi.org/10.5194/egusphere-egu24-2317, 2024.

EGU24-2624 | ECS | Posters on site | TS8.1

Ridge-dual hotspots interaction and potential hotspot-hotspot interaction in the Southeastern Indian Ocean  

Yiming Luo, Jian Lin, Zhiyuan Zhou, Fan Zhang, Xubo Zhang, and Jinchang Zhang

We investigated the impacts of the Kerguelen and Amsterdam-St. Paul (ASP) hotspots on mantle evolution and crustal accretion of nearby spreading ridges in the Southeastern Indian Ocean. Gravity analysis revealed enhanced magmatism and thickened crust along the ridge caused by the Kerguelen and ASP hotspots. By employing plate motions derived from the GPlates global plate reconstruction model, along with the ASPECT 3-D mantle convection code, we presented a comprehensive depiction of the ridge-dual hotspot system, which has been relatively underexplored in previous research. Model results indicated that the Kerguelen hotspot had a significantly greater influence on mantle temperature and ridge crustal thickness compared to the ASP hotspot. Furthermore, there is evidence suggesting a potential interaction between the dual hotspots, leading to the migration of ASP plume materials towards the Kerguelen plume.

How to cite: Luo, Y., Lin, J., Zhou, Z., Zhang, F., Zhang, X., and Zhang, J.: Ridge-dual hotspots interaction and potential hotspot-hotspot interaction in the Southeastern Indian Ocean , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2624, https://doi.org/10.5194/egusphere-egu24-2624, 2024.

EGU24-2711 | ECS | Orals | TS8.1

Links between large volcanic eruptions, basal mantle structures and mantle plumes 

Annalise Cucchiaro, Nicolas Flament, Maëlis Arnould, and Noel Cressie

As part of mantle convection, mantle plumes rise from the deep Earth, leading to volcanic eruptions during which large volumes of mafic magma are emplaced at Earth’s surface over a few million years. In 1971, Jason Morgan showed that seamount chains could be used to calculate the absolute motion of tectonic plates above fixed mantle plumes. This ground-breaking work notably led to the study of the relationship between Earth’s deep interior and its surface. Mantle plumes have been critical to constrain absolute plate motions in Earth’s recent geological past, with the development of both fixed-hotspot and moving-hotspot plate-motion models. Recent studies also revealed a statistical link between large volcanic eruptions and basal mantle structures in space and time, suggesting that large volcanic eruptions, mantle plumes, and hot basal structures are intrinsically connected. In these studies, mantle plumes were considered as the implicit process connecting volcanic eruptions at the surface to hot basal mantle structures. Geodynamic models suggest that mantle plumes are generated by two large antipodal hot basal mantle structures, up to ~1,200 km thick, and shaped by subducted oceanic crust through time. Here, we systematically compare three volcanic-eruption databases, four global tomographic models, and six reconstructions of past global mantle flow, to investigate the spatio-temporal links between volcanic eruptions, hot basal mantle structures, and modelled mantle plumes from 300 million years ago to the present day. We find that large volcanic eruptions are spatially closer to fixed and moving hot basal mantle structures than to modelled mantle plumes, because mantle plumes cover an area that is five orders of magnitude smaller than the area covered by hot basal mantle structures. The strength of the spatial-statistical relationships is largest between volcanic eruptions and modelled mantle plumes and, overall, it is larger between volcanic eruptions and moving basal mantle structures than between volcanic eruptions and fixed basal mantle structures.  This suggests that large volcanic eruptions are preferentially associated with mantle plumes generated from the interior of mobile basal mantle structures, which is in sharp contrast to previous studies that suggested mantle plumes are generated from the edges of fixed basal mantle structures.

How to cite: Cucchiaro, A., Flament, N., Arnould, M., and Cressie, N.: Links between large volcanic eruptions, basal mantle structures and mantle plumes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2711, https://doi.org/10.5194/egusphere-egu24-2711, 2024.

EGU24-4020 | ECS | Orals | TS8.1

Prolonged multi-phase volcanism in the Arctic induced by plume-lithosphere interaction 

Björn Heyn, Grace Shephard, and Clint Conrad

Between about 130 and 75 Ma, the Arctic was impacted by widespread and long-lived volcanism known as the High Arctic Large Igneous Province (HALIP). HALIP is a very unusual large igneous province because it exhibits prolonged melting over more than 50 Myr with pulses of activity, an observation that is difficult to reconcile with the classic view of large igneous provinces and associated melting in plume heads. Hence, the suggested plume-related origin and classification of HALIP as a large igneous province has been questioned, and alternative mechanisms have been invoked to explain at least part of the volcanism. However, the Arctic also exhibits a very complex and time-dependent tectonic history that includes cratons, continental margins and rifting, all of which are expected to interact with the rising plume and affect its melting behaviour.

 

Here, we use 2-D numerical models that include melting and melt migration to investigate a rising plume interacting with a lithosphere of variable thickness, i.e. an extended-basin-to-craton setting. Models reveal significant spatial and temporal variations in melt volumes and pulses of melt production, including protracted melting for at least about 30-40 Myr, but only if feedback between melt and mantle convection is accounted for. In particular, we find that melt migration transports heat upwards and enhances local lithospheric thinning, resulting in a more heterogeneous distribution of melting zones within the plume head underneath the Sverdrup Basin. Once the thicker continental and cratonic lithosphere move over the plume, plume material is deflected from underneath the Greenland craton and can then re-activate melting zones below the previously plume-influenced Sverdrup Basin, even though the plume is already ∼500 km away. Hence, melting zones may not represent the location of the deeper plume stem at a given time. Plume flux pulses associated with mantle processes, rifting of tectonic plates or magmatic processes within the crust may alter the timing and volume of secondary pulses and their surface expression, but are not required to generate pulses in magmatic activity. Hence, we propose that the prolonged period of rejuvenated magmatism of HALIP is consistent with plume impingement on a cratonic edge and subsequent plume-lithosphere interaction. Based on melt fractions, our models suggest that HALIP magmatism should exhibit plume-related trace element signatures through time, but potentially shifting from mostly tholeiitic magmas in the first pulse towards more alkalic compositions for secondary pulses, with regional variations in timing of magma types.

How to cite: Heyn, B., Shephard, G., and Conrad, C.: Prolonged multi-phase volcanism in the Arctic induced by plume-lithosphere interaction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4020, https://doi.org/10.5194/egusphere-egu24-4020, 2024.

The India-Asia convergence has persisted since the onset of collision at ~55 Ma, indicating the driving forces of Indian indentation do not disappear on continental collision in the convergence process. What drives ongoing India-Asia convergence? This puzzle cannot be well resolved by the traditional theory of plate tectonics and the concept of Wilson Cycle. Consequently, questions concerning the primary driving force of the ongoing India-Asia convergence and the magnitude of this force still await an answer. Previous works have proposed multiple candidates for the primary driver of India-Asia convergence, including the continental subduction of the Indian lithosphere under Tibet, oceanic subduction at the Sumatra-Java trench, as well as the basal drag exerted by the mantle flow on the base of Indo-Australia plate. Here we present global geodynamic models to investigate the driving forces behind the India-Asia convergence, which produce good fits to the observed motions, stresses and strains within the Indo-Australia plate. On this basis, we quantitatively calculate the magnitude of effective forces of boundary forces (slab pull and ridge push) and basal drag. We conclude that the Sumatra-Java subduction is the primary driver of the ongoing India-Asia convergence. Indo-Australia plate motion is driven at the Sumatra-Java trench, impeded along the Himalaya, which could increase the shear stress within the plate. Different from the recent emphasis on the basal drag as a dominant driving force for the India-Asia convergence, this study shows that basal drag acts as the resisting force for the northeastward motion of the giant Indo-Australia plate, though it serves as a driver in some local regions.

 

How to cite: Zheng, Q. and Hu, J.: Driving forces for the ongoing India-Asia convergence: insight from global high-resolution numerical modeling of mantle convection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4314, https://doi.org/10.5194/egusphere-egu24-4314, 2024.

EGU24-4754 | Orals | TS8.1

Mantle plumes imaged by seismic full waveform inversion: from the core-mantle-boundary to surface hotspots 

Barbara Romanowicz, Federico Munch, and Utpal Kumar

With recent progress in resolution in global seismic mantle imaging provided by numerical wavefield computations using the Spectral Element Method and full waveform inversion, Jason Morgan’s suggestion from over 50 years ago that mantle plumes may be rooted at the core-mantle boundary (CMB) has been confirmed. Yet the imaged plumes present intriguing features that contrast with the classical thermal plume model and should inform our understanding of mantle dynamics. Among other features, they are broader than purely thermal plumes, and do not extend straight from the CMB to the corresponding hotspot volcanoes, but they are frequently deflected horizontally in the extended transition zone (400-1000 km depth), so that their lower mantle location can be significantly offset (as much as a 1000 km) from their surface expression. They appear to be thinner in the upper mantle. This, together with similar horizontal flattening observed in subduction zones suggests a change in the radial viscosity structure of the mantle that may occur deeper than usually assumed to be related to the 660 km phase change. The fattest plumes have been shown to be anchored within the perimeter of the large low shear velocity provinces (LLSVPs) and an increasing number of them appear to house mega-ultra low velocity zones within their roots.  Moreover, in the upper mantle, they appear to be associated with regularly spaced low velocity channels aligned with absolute plate motion.

We discuss these features in the light of recent regional imaging updates in the south Atlantic and beneath Yellowstone, contrasting the corresponding mantle plumes, and in particular showing mounting evidence that the LLSVPs are not compact “piles” extending high above the CMB, but rather a bundle of thermo-chemical plumes feeding secondary scale convection in the top 1000 km of the mantle.

How to cite: Romanowicz, B., Munch, F., and Kumar, U.: Mantle plumes imaged by seismic full waveform inversion: from the core-mantle-boundary to surface hotspots, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4754, https://doi.org/10.5194/egusphere-egu24-4754, 2024.

EGU24-6247 | ECS | Posters on site | TS8.1

Slab dynamics in the mantle: a back-to-basics approach 

Abigail Plimmer, Huw Davies, and James Panton

Subduction is one of the most fundamental processes on Earth, linking the lithosphere and mantle and is a key driving force in mantle circulation. Despite this, and the advancement of geophysical methods which allow us to better understand mantle dynamics, our understanding of slab behaviour is still limited. The Earth is a very complex system, and so conclusions regarding slab dynamics are also sensitive to the interplay between countless processes acting within the mantle. 

There is much to learn about slab sinking in the mantle from considering a single 'perfect' plate, such that the dynamics can be isolated from any pre-established or distal processes. We present a range of 3D spherical mantle circulation models which evolve from the initial condition, driven by a 'perfect' plate at the surface. Each of these plates comprises a rectangular geometry, bound by a subduction zone on one side, a spreading ridge on the opposite side, and two tranform faults on the adjacent edges. We vary the geometry of the plate, both in terms of the length of the subducting trench, and the distance from the trench to the ridge, and vary the plate velocity.

We will report the slab behaviour in terms of plate geometry, mantle properties, and plate velocity, focussing on the evolution of downwellings, upwellings and other mantle structures in response to mantle circulation models driven solely by a single plate at the surface.

How to cite: Plimmer, A., Davies, H., and Panton, J.: Slab dynamics in the mantle: a back-to-basics approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6247, https://doi.org/10.5194/egusphere-egu24-6247, 2024.

EGU24-6549 | ECS | Posters on site | TS8.1

Utilizing Euler poles for the evaluation of plate rigidity in numerical mantle convection models 

Taiwo Ojo, Joshua Guerrero, Chad Fairservice, Pejvak Javaheri, and Julian Lowman

We implement an innovative method of plate identification for the purpose of evaluating plate motion in numerical mantle convection models. Our method utilizes an existing tool,  Automatic Detection Of Plate Tectonics (ADOPT), which applies a tolerance (threshold) algorithm to elevation maps, to detect candidate plate boundaries at the surface of 3-D spherical mantle convection models. The logarithm of the strain-rate field yields a well-defined elevation map where local maxima lineations indicate spreading centres, zones of convergence, transform faults or diffuse deformation zones. For the plates found by ADOPT’s analysis, we determined rotation (Euler) poles implied by the velocities  within  the plate interiors. Subsequently, we examined the velocity field of each model plate for its agreement with rigid motion about the Euler poles.  We apply our method to snapshots taken from three previously published mantle convection calculations that appear to generate plate-like surface behaviour. Self-consistently generated model plates were obtained by combining a highly temperature-dependent viscosity with a yield stress that adds a strain-rate dependence to the viscosity, thus allowing for both intra-plate low strain-rate and weakening along tightly focussed plate boundaries. We generally identify more (and smaller) rigid plates for low yield stress or low threshold. Strong agreement of the surface velocities with rigid-body rotation around Euler poles is found for many of the plates identified; however, some plates also exhibit internal deformation. Regions that show a departure from rigidity can be decomposed into subsets of rigidly moving plates. Thus, the identification of a mantle convection model's maximally rigid plate surface may require plate boundary detection at both low and high thresholds. We suggest that as global mantle convection models superficially converge on the generation of plate boundary network similar to those observed with plate tectonics (including transform fault generation), testing for plate rigidity through the determination of Euler poles can serve as a quantitative measure of plate-like surface motion.

How to cite: Ojo, T., Guerrero, J., Fairservice, C., Javaheri, P., and Lowman, J.: Utilizing Euler poles for the evaluation of plate rigidity in numerical mantle convection models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6549, https://doi.org/10.5194/egusphere-egu24-6549, 2024.

EGU24-6630 | Posters on site | TS8.1

Gondwanan Flood Basalts Linked Seismically to Plume-Induced Lithosphere Instability 

Ya-Nan Shi and Jason Morgan

Delamination of continental lithospheric mantle is now well-recorded beneath several continents. However, the fate of delaminated continental lithosphere has been rarely noted, unlike subducted slabs that are reasonably well imaged in the upper and mid mantle. Beneath former Gondwana, recent seismic tomographic models indicate the presence of at least 5  horizontal fast-wavespeed anomalies at ~600 km depths that do not appear to be related to slab subduction, including fast structures in locations consistent with delamination associated with the Paraná Flood Basalt event at ~134 Ma and the Deccan Traps event at ~66 Ma. These fast-wavespeed anomalies often lie above broad slow seismic wavespeed trunks at 500-700 km depths beneath former Gondwana, with the slow wavespeed anomalies branching around them. Numerical experiments indicate that delaminated lithosphere tends to stagnate in the transition zone above a mantle plume where it shapes subsequent plume upwelling. For hot plumes, the melt volume generated during plume-influenced delamination can easily reach ~2-4×106 km3, consistent with the basalt eruption volume at the Deccan Traps. This seismic and numerical evidence suggests that observed high wavespeed mid-mantle anomalies beneath the locations of former flood basalts are delaminated fragments of former continental lithosphere, and that lithospheric delamination events in the presence of subcontinental plumes induced several of the continental flood basalts associated with the multiple breakup stages of Gondwanaland. Continued upwelling in these plumes can also have entrained subcontinental lithosphere in the mid-mantle to bring its distinctive geochemical signal to the modern mid-ocean spreading centers that surround southern and western Africa.

How to cite: Shi, Y.-N. and Morgan, J.: Gondwanan Flood Basalts Linked Seismically to Plume-Induced Lithosphere Instability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6630, https://doi.org/10.5194/egusphere-egu24-6630, 2024.

EGU24-7075 | Orals | TS8.1

Absence of surface volcanism and the indeterminate evidence for continental mantle plumes 

Simone Pilia, Giampiero Iaffaldano, Rhodri Davies, Paolo Sossi, Scott Whattam, and Hao Hu

There are rare occurrences on Earth where mantle plumes intersect with continents, resulting in surface volcanism.Unlike their more common counterparts in oceanic lithosphere, where the ascent of melts is facilitated by a thinner lithosphere, identifying continental plumes is challenging. Surface volcanism, traditionally a key indicator of mantle plumes, may play a diminished role in regions characterized by complex tectonics and variations in lithospheric thickness.

Eastern Oman provides an excellent example where a continental mantle plume has remained undetected due to the absence of current surface volcanism. The region exhibits evidence of intraplate basanites, although with an age of ~35-40 Ma. Given their geochemical signature, these alkaline rocks likely originated from a mixture of melts from a plume-derived source and those from a lithosphere-derived component. Using P- and S-wave arrival-time residuals from distant earthquakes, we image a new mantle plume in eastern Oman, which we name the Salma plume. This continental plume is revealed in our 3-D P- and S-wave tomographic models as a 200 km low-velocity conduit extending to at least the base of the upper mantle, and located below the area of Tertiary intraplate volcanism. Despite experiencing minimal shortening since the Paleogene, the shallow-marine sediments of the Salma Plateau in eastern Oman reach elevations exceeding 2000 meters. Ongoing uplift, indicated by elevated Quaternary marine terraces, suggests that the plateau is still rising. The present uplift rate is modest but maps of residual topography show a positive trend in eastern Oman that can be associated to the presence of a plume.

Incorporating a geodynamic perspective, our analysis of noise-mitigated Indian plate motion relative to Somalia reveals that India underwent a constant-velocity reorientation of approximately 15˚  from 48 to 30 Ma, concurrent with the arrival of the plume head beneath eastern Oman. We quantitatively demonstrate that increased asthenospheric flow induced by the plume flux in eastern Oman, adjacent to the Indian plate in the Eocene, may be responsible for deflecting the Indian plate path, as indicated in kinematic reconstructions.

The consequence of ignoring a plume in Oman is that we were unable to understand many of the enigmatic observations from plume impingement at ~40 Ma. Our study underscores the potential of combining seismology, geology, geochemistry, and geodynamics to be a more effective approach for detecting continental plumes than relying solely on surface volcanism, and has transformed our understanding of the tectonic evolution of the area and beyond.

How to cite: Pilia, S., Iaffaldano, G., Davies, R., Sossi, P., Whattam, S., and Hu, H.: Absence of surface volcanism and the indeterminate evidence for continental mantle plumes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7075, https://doi.org/10.5194/egusphere-egu24-7075, 2024.

EGU24-7255 | Orals | TS8.1

Short-period (400 kyr) pulsation of the Réunion plume 

Vincent Famin, Xavier Quidelleur, and Laurent Michon

Many hotspots worldwide display evidence of fluctuating magmatic emplacement rates in their history, at periods of 1-20 Myr, indicative of changing melt production within underlying mantle plumes. Here we report unprecedentedly short fluctuations of magmatic activity in the Réunion hotspot, emblematic because it started with the Deccan traps suspected to have caused the Cretaceous-Paleogene mass extinction. Using K-Ar geochronology, field observations, and geomorphology, we reconstructed the volcanic history of La Réunion and Mauritius islands, the two latest manifestations of the Réunion hotspot. Our reconstruction reveals coeval magmatic activity pulses and rest intervals for the two islands over the past 4 Ma. The period of these pulses, of ~400 kyr, is an order of magnitude shorter than any fluctuation found on other hotspots. Given the distance between La Réunion and Mauritius (~230 km), this synchronous short-period pulsation of the Réunion hotspot cannot stem from the lithosphere (≤70 km thick), and must be attributed to deeper plume processes. Moreover, this ~400 kyr periodicity coincides with the recurrence time of magmatic phases in the Deccan traps, suggesting that the pulsation began with the initiation of the hotspot. We propose that the Réunion plume is regularly pulsing with a periodicity of ~400 kyr, possibly since the Cretaceous-Paleogene transition, thus delivering extremely short-period waves of magma to the surface, synchronous over hundreds of kilometers. Understanding the geodynamic causes of this superfast beat of the Réunion plume is the objective of the four-year project “Plum-BeatR”, funded by the Agence Nationale de la Recherche (ANR- 23-CE49-0009), starting in 2024.

How to cite: Famin, V., Quidelleur, X., and Michon, L.: Short-period (400 kyr) pulsation of the Réunion plume, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7255, https://doi.org/10.5194/egusphere-egu24-7255, 2024.

Plate tectonics plays a pivotal role in shaping the Earth's surface and is intricately linked to internal processes, including the subduction of cold slabs and the ascent of hot mantle plumes. Statistical analyses have unveiled a strong correlation between the distribution of large igneous provinces (LIPs) over the past 320 Ma and two large low-velocity provinces (LLVPs) beneath Africa and the Pacific Ocean. Consequently, hypotheses have emerged suggesting the long-term stability of these LLVPs. However, numerical modeling challenges this notion, suggesting that these basal mantle structures are mobile. To resolve these debates, we attempt to study these basal mantle structures from the evolution of intermediate-scale thermochemical anomalies. We report such an intermediate-scale thermochemical anomaly beneath the NW Pacific Ocean based on existing tomographic models and use paleogeographically constrained numerical models to study its evolution. Considering different plate configurations in North Pacific, our models consistently show that this anomaly was separated from the Perm anomaly by the subduction of the Izanagi slab in the Cretaceous. After the separation, it generated a mantle plume, inducing an oceanic plateau that got subducted beneath Kamchatka in Eocene. This scenario is consistent with multiple lines of evidence, including the seismic anomaly in the lower mantle, a seismically detected megameter-scale reflector that coincides with the subducted oceanic plateau and changes in Pacific Plate motion that correlated with the Eocene trench-plateau collision. We propose that intermediate-scale low velocity structures constantly undergo segregation and coalescing, and are sources of plumes that lie outside the two major LLVPs. Merging of the reported anomaly with the Pacific LLVP suggests the latter is still under assembly.

How to cite: Zhang, J. and Hu, J.: Segregation of thermochemical anomaly and associated deep mantle plume outside the large low-velocity provinces, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8432, https://doi.org/10.5194/egusphere-egu24-8432, 2024.

EGU24-8563 | ECS | Orals | TS8.1

UPFLOW body wave tomography of the whole mantle column beneath the Azores-Madeira-Canaries region 

Maria Tsekhmistrenko, Ana Ferreira, and Miguel Miranda

We present initial tomographic findings from the ERC-funded UPFLOW (Upward mantle flow from novel seismic observations) project, showcasing results from a large-scale passive seismology experiment conducted in the Azores-Madeira-Canaries region between July 2021 and September 2022. Recovering 49 out of 50 ocean bottom seismometers (OBSs) in a ~1,000×2,000 km2 area with an average station spacing of ~150-200 km, we analyze approximately ~8000 multi-frequency (T ~2.7-30 s) body-wave travel time cross-correlation measurements derived from UPFLOW OBS data and over 120 teleseismic events. A preliminary P-wave tomographic model is presented, offering insight into the region's mantle dynamics.

Furthermore, by integrating UPFLOW's OBS data with global seismic data from both temporary and permanent stations, we expand the dataset to around 600,000 multifrequency measurements. This comprehensive dataset is employed to construct a global P-wave model, providing enhanced resolution throughout the entire mantle column beneath the Azores-Madeira-Canaries region. A comparative analysis with existing global tomography models is performed, and we discuss the geodynamical implications of our new, high-resolution model.

How to cite: Tsekhmistrenko, M., Ferreira, A., and Miranda, M.: UPFLOW body wave tomography of the whole mantle column beneath the Azores-Madeira-Canaries region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8563, https://doi.org/10.5194/egusphere-egu24-8563, 2024.

EGU24-8567 | Orals | TS8.1

Iceland plume and its magmatic manifestations: LIP-Dornröschen in the North Atlantic 

Alexander Koptev and Sierd Cloetingh

The North Atlantic region is a prime example of the interaction between plate tectonic movements and thermal instabilities in the Earth’s mantle. The opening of the Labrador Sea/Baffin Bay and the North Atlantic, the widespread volcanism and the localized uplift of the topography in Greenland and the North Atlantic are traditionally attributed to the thermal effect of the Iceland mantle plume. However, several prominent features of the region – the temporal synchrony of magmatism and break-up events, the symmetrical configuration of the Greenland-Iceland-Faroe Ridge, and the diachronous domal uplift of the North Atlantic rifted margins – have inspired alternative, “non-plume” views. According to these, the North Atlantic Igneous Province (NAIP) and Iceland magmatism originate from plate tectonic processes sourced in the shallow upper mantle, at odds with the unequivocal presence of deep-seated low-velocity seismic anomalies beneath Iceland and the isotopic signatures of plume-derived melts in Cenozoic magmatic units.

We resolve apparent contradictions in the observations and reconstructions and reconcile end-member concepts of the Late Mesozoic-Cenozoic evolution of the North Atlantic realm. We show that simultaneous Paleocene (~62-58 Ma) magmatism in Western Greenland/Baffin Island and the British Isles, which together form the NAIP, is driven by two processes accidently coinciding in time: 1) the propagation of the Labrador Sea/Baffin Bay spreading axis has overlapped with the ~100-80 Ma dated segment of the Iceland hotspot track near the West Greenland margin, while 2) the actual tail of the Iceland plume has reached the eastern continental margin of Greenland, allowing a horizontal flow of hot plume material along corridors of relatively thinned lithosphere towards Southern Scandinavia and Scotland/Ireland. In this framework, the subsequent formation of the symmetrical Greenland-Iceland-Faroe Ridge can be coherently explained by the continuous supply of hot plume material through an established channel between Eastern Greenland and the British Isles. In contrast to the Scotland/Ireland region, the South Norway continental lithosphere remains too thick to enable localized uplift of the topography and melting immediately after plume lobe emplacement at ~60 Ma. Therefore, the development of topographic domes in Southern Scandinavia only started ~30 Myr later in the Oligocene as a consequence of increasing ridge-push compression that built up during the opening of the Norwegian-Greenland Sea.

The evolution of the North Atlantic region shows that a thermal anomaly that has been hidden below a thick lithosphere for tens of Myr without signs of excessive magmatism can be re-initialized (or “re-awakened”) by the lateral propagation of spreading ridges or by the tapping of its source beneath thinner segments of the overlying lithosphere due to horizontal plate movements. We dub this type of Large Igneous Province (LIP) as LIP-Dornröschen (LIP-Sleeping Beauty). We hypothesise that the term LIP-Dornröschen may be applicable to a broad family of LIPs, including Precambrian and oceanic LIPs. This means that the interpretation of the timing of LIP formation from the perspective of mantle dynamics should be treated with caution, as there may be delays between the timing of upwelling in the mantle and detectable magmatic manifestations at or near the Earth’s surface.

How to cite: Koptev, A. and Cloetingh, S.: Iceland plume and its magmatic manifestations: LIP-Dornröschen in the North Atlantic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8567, https://doi.org/10.5194/egusphere-egu24-8567, 2024.

EGU24-9504 | ECS | Orals | TS8.1

Depth dependence of mantle plume flow beneath mid-ocean ridges 

Sibiao Liu, Fan Zhang, Lei Zhao, Xubo Zhang, and Jian Lin

Hotspot-related anomalies observed in mid-ocean ridge systems are widely interpreted as the result of upwelling mantle plumes interacting with spreading ridges. A key indicator of this interaction is 'waist width', which measures the distance of plume flow along the ridge. Current scaling laws for waist width, premised on a gradual decrease in plume temperature along the ridge, often overlook sub-ridge longitudinal thermal variations, potentially biasing width measurements at various depths. In this study, we refined waist width measurements by tracking the material flow and its thermal diffusion from the plume source in plume-ridge interaction models. These non-Newtonian viscoplastic models integrate ridge spreading, lithospheric cooling with hydrothermal circulation, and mantle dehydration. Model results show that the hot plume initially boosts upwelling from the deep mantle to near the dehydration zone, followed by a slowdown and lateral spread across and along the ridge. In addition to strongly correlating with plume flux and spreading rate, the pattern and distance of plume flow vary with depth. At deeper depths, the plume expands radially in a pancake-like thermal pattern with shorter along-ridge distances, while shallower, it shows an axial pipe-like dispersion over longer distances, forming a concave structure. This is shaped by the cooling of the plume material during the phase of decelerated upwelling and along-ridge dispersion within the dehydration zone and cooling of the oceanic lithosphere associated with plate spreading. Estimates of plume buoyancy flux, derived from both material- and isotherm-tracking waist widths, show significant variations at different depths, suggesting that understanding depth-dependent plume dynamics beneath mid-ocean ridges is crucial for reconciling the observed discrepancies in buoyancy flux estimates.

How to cite: Liu, S., Zhang, F., Zhao, L., Zhang, X., and Lin, J.: Depth dependence of mantle plume flow beneath mid-ocean ridges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9504, https://doi.org/10.5194/egusphere-egu24-9504, 2024.

EGU24-9647 | Posters virtual | TS8.1

Influence of the Kerguelen hotspot on eastern Indian lithosphere by trans-dimensional Bayesian inversion of Rayleigh wave dispersion data 

Nirjhar Mullick, Vivek Kumar, Gokul Saha, Shyam S. Rai, and Thomas Bodin

Mantle plumes play major role in modifying the continental lithosphere producing rifts and massive amounts of basaltic volcanism as the anomalously hot mantle undergoes decompressive melting. If conditions are favourable the rift may widen and a new ocean is formed. During the break up of Eastern Gondwana at ~ 130 Ma, the Kerguelen mantle plume influenced the separation of India from Antarctic and Australian plates and generation of the Eastern Indian Ocean. Eastern India-Bangladesh region (83-94ºE, 21-26ºN) carries imprints of the plume activity in the form of the Rajmahal and Sylhet traps and their subsurface expression in Bengal basin and extensive lamproytes. Existing geophysical studies of the region are mainly crustal scale and do not explicitly refer to the Kerguelen plume activity providing geophysical evidence for the same. We present here lithospheric shear velocity structure of the region up to a depth of ~ 175 km by trans-dimensional Baysian inversion of Rayleigh group velocity dispersion data (7-100s at 1º X 1º resolution). Using the same, we investigate the influence of the Kerguelen plume on the lithosphere of the Eastern India-Bangladesh region that comprises the Eastern India craton, the Bengal basin, the Bhrahmaputra basin, Bangladesh and the Shillong- Mikir plateau.

How to cite: Mullick, N., Kumar, V., Saha, G., Rai, S. S., and Bodin, T.: Influence of the Kerguelen hotspot on eastern Indian lithosphere by trans-dimensional Bayesian inversion of Rayleigh wave dispersion data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9647, https://doi.org/10.5194/egusphere-egu24-9647, 2024.

EGU24-10288 | Posters on site | TS8.1

Heterogeneous mantle source of Mauna Loa volcano (Hawai’ian plume) revealed by Sr-isotope and trace elements signatures of olivine-hosted melt inclusions 

Adrien Vezinet, Blas Barbera, Alexander V. Sobolev, Valentina G. Batanova, Charbel Kazzy, and Aleksandr V. Chugunov

Melt inclusions hosted in highly magnesian olivine crystals have proven invaluable for probing the composition of the mantle through time since their geochemical signature is reflecting that of parental melt. Additionally, the geochemical study of melt inclusions has shown to be more suited to identify the heterogeneity in the magma from which they crystallized, particularly the chemically depleted domains [1, 2]. Here, we will present new major, minor & trace elements, H2O contents and Sr-isotope signature of more than 300 olivine-hosted naturally quenched melt inclusions from Pu’u Wahi (910 yr-old) and Puʻu Mahana (ca. 50 kyr-old), two ash cones associated with Mauna Loa, the largest shield volcano of the Hawai’ian seamount chain. In order to have a high degree of confidence in the geochemical proxies, Sr-isotope and trace elements analyses were conducted through laser ablation split stream (LASS) protocol on top of EPMA and Raman (for H2O contents) analytical spots. Preliminary results in our new set of inclusions show the presence of high (Sr/Ce)N inclusions, previously interpreted as indicating either gabbro influence in the source of the plume [3] or interactions between plagioclase-rich cumulates and percolating mantle-derived melts [4]. Further, “ultra-depleted melts”, UDM, indicated by K2O contents < 0.1 wt.% identified in [1], have also been re-identified in this new set of inclusions (not analyzed for Sr-isotope yet). 87Sr/86Sr of non-UDM inclusions ranges from 0.70361±0.00025 to 0.70427±0.00025, i.e. analogous to the most recent TIMS values [4, 5]. Additional LASS analyses will be conducted before the meeting. The full set of analyses will be confronted to published results on the same volcano [1, 3-6] and integrated in a larger framework of interactions between mantle plume and consequences for plate tectonic.

References:

  • Sobolev, A.V., et al., Nature, 2011. 476(7361).
  • Stracke, A., et al., Nature Geoscience, 2019. 12(10).
  • Sobolev, A.V., et al., Nature, 2000. 404(6781).
  • Anderson, O.E., et al., Geochemistry, Geophysics, Geosystems, 2021. 22(4).
  • Reinhard, A., et al., Chemical Geology, 2018. 495.
  • Sobolev, A.V., et al., Nature, 2005. 434(7033).

How to cite: Vezinet, A., Barbera, B., Sobolev, A. V., Batanova, V. G., Kazzy, C., and Chugunov, A. V.: Heterogeneous mantle source of Mauna Loa volcano (Hawai’ian plume) revealed by Sr-isotope and trace elements signatures of olivine-hosted melt inclusions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10288, https://doi.org/10.5194/egusphere-egu24-10288, 2024.

EGU24-10507 | ECS | Posters on site | TS8.1

The density and viscosity of a bilithologic plume-fed asthenosphere 

Jia Shao and Jason Morgan

Pyroxenites are generated by the subduction of sediments and oceanic basalts into the deep mantle. These rocks, together with the larger volume fraction of their surrounding mantle peridotites make up a lithologically heterogeneous two-component mantle, sometimes called a ‘marble-cake’ or ‘plum-pudding’ mantle. Geochemical and petrological observations have shown that pyroxenites play a significant role in the genesis of oceanic island basalts (OIB). However, the consequences of preferential pyroxenite melting on bulk mantle properties have yet to be systematically explored. For example, how does the plume melting process modify a plum-pudding mantle’s bulk density and viscosity? This question could be very important, in particular if the asthenosphere is formed by material from upwelling, melting plumes.

To explore the above questions, we use the thermodynamic software Perple_X to determine densities for different degrees of depleted (i.e. partially melted) peridotites and pyroxenites. We then include these relations into a one-dimensional numerical simulation code for the upwelling and pressure-release melting of a potentially wet multi-component mantle. We investigate the density changes associated with the melting of this idealized mantle’s pyroxenites and peridodites, and also the viscosity change by assuming that the reference viscosity of pyroxenite is 10-100 times that of dry peridotite at similar P-T conditions, since the peridotite’s olivines are the weakest large volume-fraction minerals in the upper mantle. We have explored the effects of mantle temperature, initial water contents, initial fractions of pyroxenites and peridotite, peridotite solidi, and the thickness of the overlying lithosphere which will affect the depth-interval of upwelling and melting. Preliminary results show that significant density and viscosity changes should take place during plume upwelling and melting. ~30% partial melting of pyroxenite would lead to a net bulk density reduction of 0.3%, comparable to the thermal buoyancy associated with a ~100° temperature increase. As long as the surrounding peridotites do not melt, the mixture’s aggregate viscosity will remain that of wet peridotitic mantle; after the peridotites have melted a percent or so, the aggregate viscosity will increase 10-100-fold to that of dry peridotite. This could lead to the formation of a 10-100x asthenospheric viscosity restitic hotspot swell root. Eventual peridotitic melting will reduce the density of the more depleted peridotites relative to fertile peridotite as originally noted by Oxburgh and Parmentier (1977), but to a lesser degree than the density reduction associated with the preferential removal of pyroxenites by their partial melting. A dynamical consequence is that the asthenosphere is likely to be strongly stratified by density, with its most pyroxenite-depleted materials likely to rise to form a layer along the base of the overlying oceanic lithosphere. 

How to cite: Shao, J. and Morgan, J.: The density and viscosity of a bilithologic plume-fed asthenosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10507, https://doi.org/10.5194/egusphere-egu24-10507, 2024.

EGU24-10967 | ECS | Posters on site | TS8.1

From plumes to subduction network formation and supercontinent break-up 

Michaël Pons, Stephan V. Sobolev, Charitra Jain, and Elodie Kendall

The evolution of modern plate tectonics is described by the Wilson cycle, which portrays the dynamics of the supercontinental cycle through the interaction of the oceanic plate with the continental plate over periods of hundreds of millions of years. This cycle is characterized by a phase of supercontinent assembly and enhanced orogenic collision, followed by a phase of supercontinent fragmentation and dispersal, as shown by the geological record. The dynamics of the Wilson cycle is intrinsically linked to mantle convection and subduction dynamics. While the assembly phase appears to follow a degree-2 mantle convection style, the mechanism responsible for supercontinent fragmentation is still debated. We hypothesize that the dispersal phase is mostly governed by trench roll-back from subductions and mantle plumes. To test this hypothesis, we have built a series of 2D and 3D geodynamic models of the Earth on a global scale using the ASPECT code. We have tested different scenarios in which we prescribe the distribution of the supercontinent Rodinia at 1Ga or Pangea at 250 Ma and let the models evolve self-consistently.  In some model variants, the strength of the supercontinent and that of the surrounding oceanic area is changed. We will present our preliminary results and discuss the dynamics of continental dispersal and its link to subduction and mantle dynamics. In particular, 3D models will demonstrate how regional plume-induced retreating subduction zones evolve into a global network of subduction zones and tectonics plate boundaries which ultimately leads to the break-up of the supercontinent.

How to cite: Pons, M., V. Sobolev, S., Jain, C., and Kendall, E.: From plumes to subduction network formation and supercontinent break-up, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10967, https://doi.org/10.5194/egusphere-egu24-10967, 2024.

While the temperature drop across the thermal boundary layer (TBL) at the base of the mantle is likely > 1000 K, the temperature anomaly of plumes, which are believed to rise from that TBL is only up to a few hundred K. Reasons for that discrepancy are still poorly understood. It could be due to a combination of (1) the adiabat inside the plume being steeper than in the ambient mantle, (2) the plume cooling due to heat diffusing into the surrounding mantle as it rises, (3) the hottest plume temperature representing a mix of temperatures in the TBL, and not the temperature at the core-mantle boundary (CMB), (4) plumes not directly rising from the CMB due to chemically distinct material at the base of the mantle, (5) a plume-fed asthenosphere which is on average warmer than the mantle adiabat, reducing the temperature difference between plumes and asthenospheric average. Here we use the ASPECT software to model plumes from the lowermost mantle and study their excess temperatures. We use a mantle viscosity that depends on temperature and depth with a strong viscosity increase from below the lithosphere towards the lower mantle, reaching about 1023 Pas above the basal TBL, consistent with geoid modelling and slow motion of mantle plumes. With a mineral physics-derived pyrolite material model, the difference between a plume adiabat and an ambient mantle adiabat just below the lithosphere is about two thirds of that at the base of the mantle, e.g. 1280 K temperature difference at the CMB reduces to about 835 K at 200 km depth. In 2-D cartesian models, plume temperature drops more strongly and is rather time variable due to pulses rising along plume conduits. In contrast, 3-D models of isolated plumes are more steady and, after about 10-20 Myr after the plume head has reached the surface, their temperatures remain rather constant, with excess temperature drop compared to an adiabat for material directly from the CMB usually less than 100 K. This extra temperature drop is small because plume buoyancy flux is high. Hence the above points (2) and (3) do not contribute much to reduce temperature of isolated 3-D plumes. In our models, the asthenosphere is on average about 200-400 K hotter than the mantle beneath, due to plume material feeding into it. While this appears to reduce the plume temperature anomaly, a resulting cooler mantle adiabat also corresponds to an even stronger temperature drop in the basal TBL, offsetting that effect. In the Earth, plumes are likely triggered by slabs and probably rise preferrably above the margins of chemically distinct piles. This could lead to reduced excess temperatures, if plumes are more sheet-like, as the 2-D models, or temperature at their source depth is less than at the CMB.

How to cite: Steinberger, B. and Roy, P.: Why are plume excess temperatures much less than the temperature drop across the core-mantle boundary?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11566, https://doi.org/10.5194/egusphere-egu24-11566, 2024.

EGU24-11719 | Orals | TS8.1

Prospects of Neutrino Oscillation Tomography of the Earth  

Veronique Van Elewyck, Joao Coelho, Yael Armando Deniz Hernandez, Stephanie Durand, Nobuaki Fuji, Edouard Kaminski, Lukas Maderer, Eric Mittelstaedt, and Rebekah Pestes

Much has been learned about the deep Earth through a combination of geophysical constraints, theories of Earth’s formation, and seismic measurements. However, such methods alone cannot directly resolve the full structure of the inner Earth, e.g. in terms of matter density, composition and temperature distributions.

Complementary information about Earth’s interior can be provided by small, nearly massless elementary particles called neutrinos that propagate through the Earth. Neutrinos exist in different flavours and are known to experience a quantum phenomenon of flavour oscillation as they propagate. With an extremely small chance of interacting with matter, neutrinos can travel long distances through very dense materials (e.g., the Earth’s core). For atmospheric neutrinos of energy ~GeV crossing the Earth, the flavour oscillation patterns are distorted due to coherent forward scattering on electrons along their path. Measuring the flavour, energy and angular distributions of such neutrinos therefore provides sensitivity to a new observable of geophysical interest: the electron number density in the layers of matter traversed.

After a short introduction to the concepts of neutrino oscillation tomography, we will discuss the potential of this method to address open questions concerning inner Earth's structure and composition (such as the amount of light elements in the core and the nature of LLSVPs), the status of sensitivity studies, and the perspectives opened by the next generation of atmospheric neutrino detectors.

How to cite: Van Elewyck, V., Coelho, J., Deniz Hernandez, Y. A., Durand, S., Fuji, N., Kaminski, E., Maderer, L., Mittelstaedt, E., and Pestes, R.: Prospects of Neutrino Oscillation Tomography of the Earth , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11719, https://doi.org/10.5194/egusphere-egu24-11719, 2024.

The Rajmahal Traps is one of the two major Large Igneous Provinces (LIPs) that erupted in the Indian subcontinent in the Mesozoic. The trap was the product of activity at the Kerguelen hotspot, located in the Indian Ocean, that initiated around 117 Ma. Earlier studies on the eruption location of the Rajmahal trap show that its location does not coincide with the present-day location of the Kerguelen Hotspot. This difference in the paleo-locations could be the result of mantle dynamics beneath the Indian Ocean during the Cretaceous and has been explained with concepts such as the multiple diapir-single plume model, the migration pathway of the hotspot beneath the mantle, and the complex plume-ridge interaction.

In this study, we use paleogeographic reconstruction software GPlates to reconstruct the paleogeography of the Rajmahal Traps on the Indian subcontinent plate in an Antarctica fixed reference frame since 117 Ma to pin-point the paleo-location of the Kerguelen hotspot and eruption location of the Rajmahal trap along with the tectonic changes that the Indian Ocean was encountering. The mantle structure below the Indian Ocean was further studied using publicly available P-wave tomography data. The paleogeographic reconstruction linked to the mantle structure hints towards the presence of a tree-like hotspot-plume structure beneath the Kerguelen hotspot where a deep-seated single plume feeds into various fissures at the surface which are active at different points in time.

Our kinematic analysis for the Indian Plate reveals significant changes in the velocity of the plate since the Cretaceous at specific points in time in response to tectonic activities initiated by the plumes present in the Indian Ocean. These activities that link to changes in the velocity include interactions with the Morondova plume (velocity increase at 90 Ma) and Reunion hotspot (velocity increase between 78 – 62 Ma), and other processes like continental collision (velocity decrease at 56 Ma and between 50-43 Ma) and slab pull (velocity increase at 56 Ma). Using this new velocity profile, we have developed a revised velocity model for the drift of the Indian subcontinent since the Cretaceous.

How to cite: Guleriya, S., Beniest, A., and Tiwari, S. K.: Change in eruption location in Kerguelen hotspot and Kinematic Reconstruction of Rajmahal Trap:  Implications for Cretaceous to present day Geodynamics of Indian plate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11883, https://doi.org/10.5194/egusphere-egu24-11883, 2024.

EGU24-12584 | Orals | TS8.1

Robust hotspot origin far from LLSVP margins 

John Tarduno

W. Jason Morgan’s seminal development of plate tectonic theory set the foundation for current investigations of mantle convection and the nature of deep mantle plumes. More recently, hotspots have been proposed to occur at the edges of stationary African and Pacific large low shear velocity provinces (LLSVPs) and that this has a special significance in terms of plume/hotspot generation. The basis for this proposed global correlation has in turn been challenged, and whether LLSVPs edges are the sites of initial mantle plume formation debated. A different approach is to consider hotspots with the greatest buoyancy flux because to be successful, any global model should be able to explain their origin. In all analyses of buoyancy flux, the Pacific’s Hawaiian hotspot, which figured prominently in Jason’s early papers, stands out above all others. However, paleomagnetic and age-distance relationships indicate that the Hawaiian hotspot originated >1500 km N of the Pacific LLSVP and subsequently drifted to its edge where it may have become anchored. The hotspot with the highest buoyancy flux in the Atlantic is Iceland, which is far from the African LLSVP. Iceland represents the youngest of three past episodes of extraordinary volcanism affecting the North Atlantic-Arctic region, namely the North Atlantic Tertiary Volcanic Province, the High Arctic Large Igneous Province, and the Siberian Traps. This recurrent volcanism spanning more than 250 million years requires either drift of a single pulsing plume, or separate plumes, generated far from the edge of the proposed stationary African LLSVP. Thus, the nature and histories of these robust hotspots in the Pacific and Atlantic imply an origin distinct from stationary LLSVPs.  

How to cite: Tarduno, J.: Robust hotspot origin far from LLSVP margins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12584, https://doi.org/10.5194/egusphere-egu24-12584, 2024.

EGU24-13570 | Orals | TS8.1

Changes in the Rate of Ocean Crust Production Over the Past 19 Myr: Implications for Sea Level, Mantle Heat Loss, and Climate 

Colleen Dalton, Timothy Herbert, Douglas Wilson, and Weimin Si

The rate of ocean-crust production exerts control over mantle heat loss, sea level, seawater chemistry, and climate. Reconstructing ocean-crust production rates back in time relies heavily on the distribution of present-day seafloor age. Different strategies to account for the incomplete preservation of older seafloor have led to differing conclusions about how much production rates have changed since the Cretaceous, if at all. We have constructed a new global synthesis of ocean-crust production rates along 18 mid-ocean ridges for the past 19 Myr at high temporal resolution.  We find that the global ocean-crust production rate decreased by ~37% from its maximum during 19-15 Ma to its minimum during 6-4 Ma. Our ability to resolve these changes at a statistically significant level is due to the availability of many new plate reconstructions at high temporal resolution and our use of an astronomically calibrated magnetic time scale with small uncertainties in reversal ages. We show that the reduction in crust production occurred because spreading rates slowed down along almost all ridge systems. While the total ridge length has varied little since 19 Ma, some fast-spreading ridges have grown shorter and slow-spreading ridges grown longer, amplifying the spreading-rate changes. The change in crust production rate skews the seafloor area-age distribution toward older crust, and we estimate that sea level may have fallen by as much as 32-37 m and oceanic heat flow may have been reduced by 6%. We also show, using a simple model of the carbon cycle, that the inferred changes in tectonic degassing resulting from the crust-production changes can account for the majority of long-term surface-temperature evolution since 19 Ma.

How to cite: Dalton, C., Herbert, T., Wilson, D., and Si, W.: Changes in the Rate of Ocean Crust Production Over the Past 19 Myr: Implications for Sea Level, Mantle Heat Loss, and Climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13570, https://doi.org/10.5194/egusphere-egu24-13570, 2024.

EGU24-13786 | ECS | Posters on site | TS8.1

Counterflow and entrainment within a buoyant plume-fed asthenosphere 

Xianyu Li, Jia Shao, Guanzhi Wang, Yanan Shi, and Jason Morgan

Laboratory and numerical experiments and boundary layer analysis of the entrainment of buoyant asthenosphere by subducting oceanic lithosphere (cf. Morgan et al., Terra Nova, 2007) implies that slab entrainment is likely to be relatively inefficient at removing a buoyant and lower viscosity asthenosphere layer. Such asthenosphere would instead be mostly removed by accretion into overlying oceanic lithosphere, both at mid-ocean ridges where a ~60-km compositional lithosphere forms due to the melt-induced dehydration of upwelling peridotitic mantle, and later with the thermal growth of  overlying oceanic lithosphere. When an oceanic plate subducts, the lower (hot) side of a subducting slab entrains a 10– 30 km-thick downdragged layer, whose thickness depends upon the subduction rate and the density contrast and viscosity of the asthenosphere, while the upper (cold) side of the slab may entrain as much by thermal ‘freezing’ onto the slab as by mechanical downdragging.  

Here we use 2-D numerical experiments to investigate the dynamics of entrainment and counterflow at subduction zones. We explore situations with both stable subduction geometries and slab rollback. Due to its low viscosity, a plume-fed asthenosphere is particularly likely to be stratified in its internal density, with variable amounts of plume melt-extraction leading to variable pyroxenite fractions and associated vertical density stratification within a bilithologic ~80-90% peridotite, ~10-20% pyroxenite asthenosphere. While this type of vertical density stratification appears to lead to similar predicted entrainment by subducting slabs, it will generate more complex patterns of asthenospheric counterflow that involve shallower and time-dependent counterflow behind the subducting slab.

How to cite: Li, X., Shao, J., Wang, G., Shi, Y., and Morgan, J.: Counterflow and entrainment within a buoyant plume-fed asthenosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13786, https://doi.org/10.5194/egusphere-egu24-13786, 2024.

EGU24-13826 | ECS | Posters on site | TS8.1

Understanding Ni-Cu Sulphide Deposits in a Plate Tectonic and Mantle Convection Context 

Isadora Page, Ben R. Mather, Nicole Januszczak, Michele Anthony, and R. Dietmar Muller

Nickel-Copper (Ni-Cu) sulphide deposits are a diverse class of deposits, formed during the cooling and crystallisation of metal-rich mafic to ultramafic magmas. Despite sharing several key ore-forming processes, many of these deposits form in contrasting geologic environments and periods. The objective of this research project is to investigate the spatial and temporal distribution of Ni-Cu sulphide deposits in a mantle convection and plate tectonic context, and to explore the influence of different mantle and tectonic parameters on their origins and occurrence. We first determine the location of these deposits in relation to relevant geologic and tectonic features through time, including subduction zones, large igneous provinces (LIPs), and mantle plumes. Using a 1 billion year plate model we extract key parameters relating to subduction, as well as the spatio-temporal distribution of LIPs through time. Employing an associated geodynamic model, we identify model mantle plumes and quantify their key properties. Preliminary findings indicate that certain mantle plumes associated with deposits exhibit increased plume flux in the upper mantle preceding deposit formation, and that many deposits are spatially associated with LIPs throughout their formation history. For several deposits located in convergent margin settings, we have identified a notable spike in subduction volume and convergence rate during a 50-100 million year period prior to the onset of mineralisation. While the angle of the subducting slab is highly variable throughout the evolution of these deposits, several deposits are associated with a distinct steepening of the subducting plate in the lead-up to deposit formation. The findings of this study aim to contribute new insights into the dynamic processes governing the genesis of magmatic Ni-Cu sulphide deposits. These insights aid in our understanding of the interplay between mantle dynamics, plate tectonics, and deposit formation, and hold implications for future critical mineral exploration.

How to cite: Page, I., Mather, B. R., Januszczak, N., Anthony, M., and Muller, R. D.: Understanding Ni-Cu Sulphide Deposits in a Plate Tectonic and Mantle Convection Context, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13826, https://doi.org/10.5194/egusphere-egu24-13826, 2024.

EGU24-13939 | ECS | Posters on site | TS8.1

Numerical exploration of the dynamics of the subduction plate boundary channel  

Guanzhi Wang, Jason P. Morgan, and Paola Vannucchi

The plate ‘interface’ at subduction zones has often been idealized as a single fault with ‘asperities’, however there is increasing evidence that plate boundary motions typically occur across a ~100-1000m channel or shear zone. Here we investigate the dynamics of slip in a mechanically heterogeneous plate boundary shear zone, and will typically use periodic boundary conditions to model the channel at a ~m-scale.  In contrast to most previous numerical studies, we imagine that this shear zone is embedded within finite strength wall-rock associated with the downgoing and overriding plates that themselves are capable of subduction-related deformation, for example during bend-faulting of the lower-plate or a forearc deformation event. We first look at how stress-concentrations can form by the clogging of strong blocks in a channel with a weaker matrix. We find that the strength of the surrounding wall-rock will play a key role in the channel’s response to a clogging event. In general, a clogging event can be mitigated by failure of surrounding relatively weak wallrock along the edges of a subduction channel in the conceptual process put forward by von Huene et al. (2004) to drive basal erosion of the forearc. We also consider cases where metamorphic transitions have led to the existence of weaker blocks within a stronger matrix. In this case, frequent tremor-like failure of the weak blocks can coexist with rarer earthquake failure of the stronger surrounding matrix.  Finally we explore the mechanical effects of channel widening and narrowing events that will invariably lead to a component of local pressure-driven flow within a subduction shear channel. Numerical snapshots and videos are used to visualize these potential modes of subduction shear zone deformation.

How to cite: Wang, G., P. Morgan, J., and Vannucchi, P.: Numerical exploration of the dynamics of the subduction plate boundary channel , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13939, https://doi.org/10.5194/egusphere-egu24-13939, 2024.

EGU24-14528 | Posters on site | TS8.1

Using Dynamic Topography and Seismic Tomography to explore the compensation of seafloor in oceanic and back-arc basins 

Jialei Qiu, Nadia Padavini, Paola Vannucchi, and Jason Morgan

Both dynamic topography and seismic tomography have played crucial roles in providing invaluable insights into the Earth's interior structure and geological processes. Here we explore to what degree dynamic topography within ocean and back-arc basins can be correlated with the upper mantle seismic structure that has been imaged in recent high-resolution global models.

To explore the global ocean dynamic topography associated with subsurface mantle convection, we need to remove the influences of known contributing factors to seafloor relief such as the cooling of the ocean floor and the thickness of the ocean crust and sediments. We developed a series of scripts in PyGMT and MATLAB to do this, based on seafloor ages in GPLATES and sediment/crust information in CRUST1.0. With these corrections for near-surface structure, we obtained global average residual-depth values that serve as a basis for analyzing global subsurface structures linked to the asthenosphere and upper mantle, which we then compare to the vertically averaged shear-wave seismic structure above the transition zone. Our preliminary study highlights that the significant ~km-difference in dynamic topography between the Philippine back-arc basin and the Lau-Tonga backarc appear to be linked to a major difference in asthenosphere thickness and density beneath these two regions.

How to cite: Qiu, J., Padavini, N., Vannucchi, P., and Morgan, J.: Using Dynamic Topography and Seismic Tomography to explore the compensation of seafloor in oceanic and back-arc basins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14528, https://doi.org/10.5194/egusphere-egu24-14528, 2024.

EGU24-16479 | Posters on site | TS8.1

H, He, and seismic evidence for a bilithologic plume-fed asthenosphere  

Jason P. Morgan and W. Jason Morgan

Chemical diffusion in the mantle has typically been viewed to play a negligible role in geodynamic processes.  However, diffusion rates for water (H) and helium (He) are large enough that they lead to observable differences between pyroxenite-rich melting associated with ocean island volcanism (OIB) and more peridotite-rich melting associated with mid-ocean ridge basalts (MORB). Laboratory measurements of diffusion rates of H and He at ambient mantle temperatures in olivine are of order ~10 km/1.7Gyr for He and ~250 km/1.7 Gyr for H. If the mantle is an interlayered mixture of recycled oceanic basalts and sediments surrounded by a much larger volume of residual peridotites, then chemical diffusion can shape the mantle in two important ways.  Hydrogen will tend to migrate from peridotites into adjacent pyroxenites, because clinopyroxene has a much stronger affinity for water than the olivine and orthopyroxene that form the bulk of mantle peridotites. Therefore pyroxenite lithologies will typically have twice or more the water content of their surrounding damp peridotites. This will strongly favor the enhanced melting of pyroxenites that is now mostly agreed to be a common feature of the OIB source. Radiogenic 4He will have the opposite behaviour — it will tend to migrate from where it is produced in recycled incompatible-element-rich (e.g. U and Th-rich) pyroxenites into nearby, larger volume fraction, but U+Th-poorer peridotites, while the radioisotopes of Ar and Ne that are also produced by the decay of the incompatible elements K, U, and Th will diffuse much less, and thus remain within their original pyroxenite source.  This effect leads to lower 4He/21Ne and 4He/40Ar ratios in OIB in comparison to the predicted values based on the mantle’s bulk geochemistry, and complementary higher 4He/21Ne and 4He/40Ar ratios in the MORB source that is formed by the plume-fed asthenospheric residues to OIB melt extraction at plumes.

 The recent observation of a 150-km-deep positive shear velocity gradient (PVG) beneath non-cratonic lithosphere (Hua et al., 2023) is further evidence for the initiation of pyroxenitic melting at this depth within the asthenosphere. It also implies that lateral temperature variations at this depth are quite small, of order +/- 75°C. This near uniformity of temperatures near both mantle plumes and mid-ocean ridges is, in turn, strong evidence in favor of the hypothesis that the asthenosphere is fed by mantle plumes. We propose that two filtering effects occur as plumes feed the asthenosphere, removing both the hottest and coldest parts of upwelling plume material. First, the peridotite fraction in the hottest part of upwelling plume material melts enough for it to dehydrate, thereby transforming this fraction into a more viscous and buoyant hotspot swell root that moves with the overlying plate, not as asthenosphere. Second, since plume material is warmer than average mantle, it is more buoyant, creating a natural density filter that prevents any cooler underlying mantle from upwelling through it. These rheological and density filters make the asthenosphere sampled by melting at mid-ocean ridges have a more uniform temperature than its typical underlying mantle.

How to cite: Morgan, J. P. and Morgan, W. J.: H, He, and seismic evidence for a bilithologic plume-fed asthenosphere , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16479, https://doi.org/10.5194/egusphere-egu24-16479, 2024.

EGU24-17078 | ECS | Orals | TS8.1

Insight into the formation of the Siberian Large Igneous Province: A study of olivine-hosted melt inclusion in meimechite 

Mateo Esteban, Alexander Sobolev, Valentina Batanova, Adrien Vezinet, Evgeny Asafov, and Stepan Krasheninnikov

Meimechite (i.e., rare high MgO and TiO2 ultramafic rocks) concluded the Permo-Triassic Trap magmatism ca. 250 Ma-ago, known as a Siberian Large Igneous Province (SLIP) in the Meimecha-Kotui region, northern Siberia (e.g. [1]). In addition to their elevated MgO contents, meimechite’s melts display almost no crustal contamination, making them ideally suited to investigate the mantle source of the SLIP. Formerly, two opposing models were evoked for the origination of the meimechite: i) the hottest phanerozoic mantle plume [1] or ii) water fluxing of the asthenospheric mantle in a long-lived subduction zone [2]. Based on an extended analytical workflow we will shed new light on the source of these unusual rocks.

Here we present new results for more than 300 olivine-hosted homogenized melt inclusions from Siberian meimechite including major, minor and trace elements, water and Sr-isotopes contents (EPMA, LA-ICP-MS and Raman spectrometry) along with the chemical composition of their host olivine (EPMA, LA-ICP-MS). When encountered, spinel inclusions were analysed by EPMA for major element abundances.

We show that the Siberian meimechite crystallised from a highly magnesian (MgO > 22 wt%) parental melt deficient in H2O compared to Ce and K concentrations, which was degassed of most of its CO2 and likely part of its H2O while rising to shallower depths. Three independent geothermometers (Mg-Fe and Sc-Y olivine melt and Al olivine-spinel) confirm the high crystallisation temperature of the Siberian meimechite, ca. 1400oC. Furthermore, the calculated potential temperatures (over 1500oC) imply a mantle plume origin of the Siberian meimechite and, consequently, of the SLIP.

Initial 87Sr/86Sr values of melt inclusions reveal heterogeneous populations ranging from 0.7022±0.0002 to 0.7039±0.0004 suggesting mixing between at least two depleted mantle components. The less depleted group has an average Bulk Silicate Earth (BSE) model age of 876±88 Ma, whereas the more depleted group is significantly older with an average model age of 1716±76 Ma. All source components display significantly fractionated proxies of continental crust extraction (Nb/U, Th/U and Ce/Pb [3]), indicating major events of continental crustal formation and deep recycling of residual lithosphere before the Proterozoic Eon.

References:

[1] – Sobolev, A.V., et al., Russ. Geol. Geophys., 2009 and references therein. [2] – Ivanov, A.V., et al., Chem. Geol., 2018. [3]- Hofmann, A.W. et al. EPSL, 1986.

How to cite: Esteban, M., Sobolev, A., Batanova, V., Vezinet, A., Asafov, E., and Krasheninnikov, S.: Insight into the formation of the Siberian Large Igneous Province: A study of olivine-hosted melt inclusion in meimechite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17078, https://doi.org/10.5194/egusphere-egu24-17078, 2024.

EGU24-17341 | ECS | Orals | TS8.1

The Influence of Mantle Plumes on Plate Tectonics 

Ingo L. Stotz, Berta Vilacís, Jorge N. Hayek, Sara Carena, Anke Friedrich, and Hans-Peter Bunge

Our understanding of plate tectonics and mantle convection has made significant progress in recent decades, yet the specific impact of mantle plumes on plate tectonics remains a topic of controversy. The motions of the Earth’s lithosphere serves as a powerful lens into the dynamic behavior of the asthenosphere and deeper mantle, helping to untangle such controversies. Surface observations, therefore, provide important constraints on mantle convection patterns through space/time. Among these observations, the record of plate motion changes stands out, as it enables the geographical identification of torque sources. Consequently, surface observations provide essential constraints for theoretical models and numerical simulations.

The analytical Poiseuille flow model applied to upper mantle flux in the asthenosphere offers a robust and testable prediction: Poiseuille flow induced plate motion changes should coincide with regional scale mantle convection induced elevation changes. Mantle plumes can generate such pressure driven flows, along with intraplate magmatism and induce buoyancy-driven uplift that leaves an imprint in the sedimentary record.

Here, I will present a synthesis of geological and geophysical observations, supported by analytical calculations, to illustrate that a significant number of plate motion changes can be attributed primarily to torques originating from mantle plumes.

How to cite: Stotz, I. L., Vilacís, B., Hayek, J. N., Carena, S., Friedrich, A., and Bunge, H.-P.: The Influence of Mantle Plumes on Plate Tectonics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17341, https://doi.org/10.5194/egusphere-egu24-17341, 2024.

Models depicting the plate kinematic development of the Indian Ocean have a range of applications including in paleogeographic studies and in formulating and testing ideas about plume/plate interactions. Until now, these applications have been forced to tolerate egregious model/observation inconsistencies concerning the relative motion history of India and Madagascar. Whilst the Phanerozoic record of these motions begins with ∼90 Ma basalts that erupted along a narrow rift basin, all modern plate kinematic models for the Indian Ocean predict hundreds of kilometres of relative motions, in diverse and conflicting senses, over several tens of millions of years prior to the eruptions. The diversity of these predicted motions suggests they are artefacts that arise from differing approaches taken to modelling the development of the eastern and western parts of the ocean, rather than a reflection of insufficient or absent geological observations. In this contribution, I present a new model for the early plate kinematic development of the Indian Ocean that is constrained by observational evidence for relative plate motion azimuths in the Enderby and western Bay of Bengal basins and by explicitly maintaining a rigid mid- and early Cretaceous Indo-Malagasy body. This approach requires the model to feature two small tectonic plates between the continental margins of eastern India and East Antarctica. The older of the two, Mandara, is an intraoceanic plate in the Enderby Basin that may have formed in relation to delivery of excess melt from the Kerguelen plume to the basin's mid-ocean ridge. The younger plate, Vasuki, in the western Bay of Bengal Basin, also accommodated plume-related melt at its boundaries, in its case from the Marion and possibly also the Crozet plume. The model shows this plate transporting Sri Lanka ∼800 km southwards along the eastern Indian continental margin to its present location. The model also requires the presence of around half a million square kilometres of continental crust beneath the Kerguelen Plateau, which lies within the range of published observation-led estimates of its extent. Neither the absence of evidence for relative motions between India and Madagascar prior to ∼90 Ma, nor the modelled Euler rotation pole's location afterwards, are consistent with suggestions that traction forces related to the ascent of the Marion plume drove the mid-Cretaceous onset of subduction in the western Neotethys.

How to cite: Eagles, G.: A new model of plate kinematics describing the early development of the Indian Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17862, https://doi.org/10.5194/egusphere-egu24-17862, 2024.

EGU24-18017 | Orals | TS8.1

Flexural Pumping and the Origins of Petit-Spot Volcanism 

Paola Vannucchi, Yanan Shi, Ting Yang, Gou Fujie, and Jason P. Morgan

Most volcanic activity on Earth is linked to well-known processes like plate tectonics and mantle plumes, typically through mechanisms such as flux-melting in subduction zones and decompression-melting at ridges and mantle plumes. However, recent discoveries point to a different origin for some intraplate volcanism, a key example being 'Petit-Spots'—small volcanic mounds that erupt on incoming plates near subduction zones. Here we propose that flexural pumping, occurring as the subducting slab unbends, transports fluids released by intra-slab dehydration to the slab's base where these fluids induce flux-melting in the warm slab base and asthenosphere beneath the slab. Counterflow in the buoyant asthenosphere beneath the subducting plate further expands the region of petit-spot volcanism. This mechanism not only explains the origin of petit-spot volcanism but also suggests a broader conceptual model for generating low-degree melts in the oceanic asthenosphere.

How to cite: Vannucchi, P., Shi, Y., Yang, T., Fujie, G., and Morgan, J. P.: Flexural Pumping and the Origins of Petit-Spot Volcanism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18017, https://doi.org/10.5194/egusphere-egu24-18017, 2024.

EGU24-18296 | ECS | Posters on site | TS8.1

How could a single Iceland Plume produce the widely scattered North Atlantic Igneous Province volcanism? New clues from Britain and Ireland. 

Raffaele Bonadio, Sergei Lebedev, David Chew, Yihe Xu, and Javier Fullea

The extensive Paleocene magmatism of the British and Irish Tertiary Igneous Province (BITIP)—a part of the North Atlantic Igneous Province (NAIP)—was accompanied by significant uplift and exhumation, as evidenced by geothermochronological and other data. The enigmatic origins of the volcanism and uplift are debated. The Iceland Hotspot reached the North Atlantic at that time and could probably supply anomalously hot asthenospheric material to the volcanic areas of NAIP, but they were scattered over a broad area thousands of kilometres across. This motivates alternative, non-plume explanations.

Here, we obtain a map of the lithosphere-asthenosphere boundary (LAB) depth in the region using thermodynamic inversion of seismic surface-wave data. Love and Rayleigh phase velocity maps in broad period ranges were computed using optimal resolution tomography with direct model error estimation and supplied the data for the inversion.

Our results reveal a consistently thinner-than-average lithosphere beneath the Irish Sea and surroundings, encompassing northern Ireland and western Scotland and Wales. The Paleocene uplift, BITIP volcanism and crustal underplating are all located in the same regions, which are underlain, consistently, by anomalously thin lithosphere.

The previously unknown lithospheric anomalies we discover yield a new insight into how the Iceland Plume could cause volcanism scattered over the vast NAIP. Plume material is likely to have flowed into pre-existing areas of thin continental lithosphere, whose thickness was then reduced further by the erosion by the hot asthenosphere. The thinning of the lithosphere and the presence of hot asthenosphere beneath it can account for the uplift, volcanism and crustal underplating. The localisation of the plume material in scattered thin-lithosphere areas, such as the circum-Irish-Sea region, can explain the wide scatter of the volcanic fields of NAIP.

How to cite: Bonadio, R., Lebedev, S., Chew, D., Xu, Y., and Fullea, J.: How could a single Iceland Plume produce the widely scattered North Atlantic Igneous Province volcanism? New clues from Britain and Ireland., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18296, https://doi.org/10.5194/egusphere-egu24-18296, 2024.

The X-discontinuity at 300 km beneath the Hawaiian hotspot has been hypothesized to require at least 40% basalt, a figure that would far exceed the plume's buoyancy and thus be irreconcilable with initial entrainments.
We had previously explored the potential for large basalt accumulations to form over time by simulating a section of the plume conduit, with known quantities of basaltic material flowing in as discrete heterogeneities. For entrainments of 10-20%, we had estimated average accumulations of 20-25% at ~300 km depth.
While this simplified setting recreated segregation of the denser material, it did not feature a realistic plume. On the other hand, employing mechanical mixture compositions hamper quantitative analyses of the recycled basalt.

I have overcome this issue by developing a novel implementation to the ASPECT code.
My advancement features a mechanical mixture composition (82% harzburgite — 18% basalt) for both the background mantle and the plume. The recycled material is then added to the self-consistent rising plume in the form of compositionally distinct basaltic heterogeneities. By combining these two approaches, I was able to successfully reproduce and quantify material segregation while keeping an accurate plume composition.

Preliminary results, conducted in a 2000 km * 1000 km 2D domain, with entrainments of 10-20%, and a maximum resolution of 0.98 km in the heterogeneities, show average basalt accumulations of 20-22% around 300 km depth. Occasional, transient peaks at 31% and 35% can be observed for plumes incorporating 15% basalt. Over the model time (20 Ma), the denser material tends to sink between 360-660 km depth, generating large average accumulations of 35-40%. 

This new strategy not only opens promising scenarios by overcoming long-standing model limitations, but also reinforces the potential for mantle plumes to accumulate more denser material than classically thought, shedding further light on the controversial link between the X-discontinuity and the Hawaiian plume activity.

How to cite: Monaco, M.: A Novel Implementation to Simulate Basalt Segregation in the Hawaiian Mantle Plume Overcomes Model Limitations and Elucidates the Origin of the X-discontinuity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18845, https://doi.org/10.5194/egusphere-egu24-18845, 2024.

EGU24-19459 | ECS | Posters on site | TS8.1

Influence of small-scale convection on the cooling of oceanic lithosphere at slow and fast spreading ridges 

Raghu Ram Gudipati, Marta Pérez-Gussinyé, and Javier García-Pintado

Classic models of continental rifting predict that after continental break-up, the extended lithosphere returns to its original thermal state (McKenzie, 1978). At this time, the heat-flow should decrease from the proximal margin sectors, where the radiogenic crust is still relatively thick, towards its distal sectors, where the crust has extensively thin and the thermal lithosphere thickness approximates that of the adjacent untinned continental lithosphere. This should occur after approximately ~50 Myr for 120 km thick continental lithosphere (McKenzie, 1978). Although, good quality heat flow data is very scarce along margins, some of them, such as the Voring basin, show instead increasing heat flow towards the distal margin sectors ~60 Myr after break-up (Cunha et al., 2021). Recent numerical models have suggested, instead, that the lithosphere under the hyper-extended continental margins, does actually not return towards its original thermal thickness, instead it acquires a thickness which is similar to that of the adjacent plate, resulting in higher heat-flow towards the distal margins at ~80-100 Myr after break-up (Perez-Gussinye et al., 2023). In those models, the delay in thermal relaxation under the hyper-extended margins is caused by small-scale convections cells, a process which also prevents the oceanic lithosphere to infinitely cool and is responsible for the flattening of the oceanic bathymetry at old ages. Interestingly, the models show that the delay in thermal relaxation under both the hyper-extended rifted margins and the old oceanic crust increases with decreasing rifting and spreading velocity, such that is most obvious in ultra-slow margins and adjacent oceanic basins (Perez-Gussinye et al., 2023). Here we use updated 2D numerical models which include the thermal consequences of serpentinisation, melting and melt emplacement to understand the thermal evolution of oceanic plates and compare the resulting plate structure, heat-flow and bathymetry with the observations from seismic LAB structure, and global heat-flow and bathymetry databases.

 

References

Cunha, T.A., Rasmussen, H., Villinger, H. and Akinwumiju, A.A., 2021. Burial and Heat Flux Modelling along a Southern Vøring Basin Transect: Implications for the Petroleum Systems and Thermal Regimes in the Deep Mid-Norwegian Sea. Geosciences, 11(5), p.190.

McKenzie, D., 1978. Some remarks on the development of sedimentary basins. Earth and Planetary science letters, 40(1), pp.25-32.

Pérez-Gussinyé, M., Xin, Y., Cunha, T., Ram, R., Andrés-Martínez, M., Dong, D. and García-Pintado, J., 2024. Synrift and postrift thermal evolution of rifted margins: a re-evaluation of classic models of extension. Geological Society, London, Special Publications, 547(1), pp.SP547-2023.

How to cite: Gudipati, R. R., Pérez-Gussinyé, M., and García-Pintado, J.: Influence of small-scale convection on the cooling of oceanic lithosphere at slow and fast spreading ridges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19459, https://doi.org/10.5194/egusphere-egu24-19459, 2024.

EGU24-19570 | ECS | Orals | TS8.1

The tectonic evolution of the western North American margin since the Devonian 

Andres Felipe Rodriguez Corcho, Sabin Zahirovic, Michele Anthony, Dene Tarkyth, Christopher Alfonso, Maria Seton, Dietmar Muller, Bruce Eglington, and Basil Tikoff

The western North American margin records multiple phases of rifting and convergence, resulting from the interaction between western Laurentia, rifted continental fragments, and intra-oceanic terranes originating in the Panthalassa and Pacific oceanic plates. Quantitative plate reconstructions of this margin have prioritised diverging interpretations regarding the subduction polarities of eastern Panthalassa terranes during Jurassic to Cretaceous times. These discrepancies arise from the reliance on either seismic tomography or surface geology as the first-order constraint for determining subduction polarity. We present an updated tectonic reconstruction for western North America from the Devonian to present day. In this new model, we reconcile geological histories based on surface geology, geochronology, paleomagnetism and isotopic data, with interpretations of seismic tomography. The new reconstructions account for the tectonic evolution of the Alaska orocline, western Canada and western United States (US) and south-western (SW) North America, which have not been implemented in detail in previous tectonic models. Our model suggests that most of the terranes of western North America were rifted off Laurentia and Baltica during Devonian to Triassic extension and trench-retreat. Following back-arc rifting and opening, many of the terranes (e.g. Insular, Intermontane, Angayucham) experienced an intra-oceanic phase before accreting to the continental margin of North America at different times, between Early Triassic to Late Cretaceous times. The model illustrates the collision of the Angayucham Terrane, counterclockwise rotation and orocline formation in Alaska during the middle Jurassic. In western US and SW North America, the model showcases Jurassic to Cretaceous extension and rifting. Extension starts first in western US (170-145 Ma) and is then propagated south, causing the opening of the Bisbee Basin (161-105 Ma). The model also captures the Late Cretaceous collision of the Insular Terrane, which triggered transpression, terrane translation for thousands of kilometers and clockwise rotation in western US during Late Cretaceous to Paleogene times. Our updated model highlights the importance of surface geology in constraining the polarity of ancient subduction zones interpreted from seismic tomography.

How to cite: Rodriguez Corcho, A. F., Zahirovic, S., Anthony, M., Tarkyth, D., Alfonso, C., Seton, M., Muller, D., Eglington, B., and Tikoff, B.: The tectonic evolution of the western North American margin since the Devonian, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19570, https://doi.org/10.5194/egusphere-egu24-19570, 2024.

Geodynamicists have long proposed that mantle convection creates dynamic topography — a long-wavelength, low-amplitude signal extending beyond plate tectonics. This predicts transient vertical Earth surface movement of 1–2 km across thousands of horizontal kilometers at any location, including continental interiors. Despite these claims, experts working on local observations, using the multitude of high-resolution geological, sedimentological, and geomorphological data, face challenges in finding clear evidence to unequivocally support dynamic models of whole mantle convection, including the plume mode. Moreover, regional-scale stratigraphic techniques, such as sequence stratigraphy, which enabled hydrocarbon exploration, invoke unconformities on multiple scales but, from their far-field perspective, render correlation to distinct geodynamic events difficult.

To circumvent this scaling and correlation problem, I propose to reverse the stratigraphic perspective to an outwards-directed view. This approach requires a theoretical geodynamic framework and the identification of tectonic events (center, near field), such as magmatic arcs, flood basalts, or uplifted domes, followed by outward-directed geological mapping of regional-scale stratigraphic unconformities —predicted by theory— to distal regions. This approach is analogous to the way in which paleoseismologists examine so-called event horizons, i.e., unconformities in the stratigraphic record adjacent to fault scarps that preserve a record of the Earth's surface at the time of earthquake rupture.

This event-based stratigraphic mapping method (EVENT-STRAT) enables analysis of geological events on geological maps compiled at regional to continental scales. The technique connects local work into a continent-scale framework, allowing identification of transient patterns related to dynamic mantle-derived events. The EVENT-STRAT mapping method is designed to visualize geological effects resulting from both the plate and the plume mode of mantle convection. The toolbox consists of the hiatus mapping method (Friedrich 2019, Geological Magazine) and the event-based stratigraphic framework mapping (e.g., Friedrich et al. 2018, Gondwana Research). The upcoming EVENT-STRAT mapping method involves multiple polygonal stacking to analyze various stratigraphic event horizons, such as hiatus surfaces and unconformities. The most significant current challenge is to add the high-precision stratigraphic data compiled on local chronostratigraphic charts to continent-scale geological maps. This effort requires the attention of geological surveys on international scales seeking to compile theory-based geodynamic-stratigraphic parameters on the next generation of global and continent-scale geological maps.

How to cite: Friedrich, A. M.: Geodynamic Stratigraphy — Defining the Need for Mapping Strategies to link Models of Mantle Dynamics to Surface Processes on Geological Scales, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19837, https://doi.org/10.5194/egusphere-egu24-19837, 2024.

EGU24-440 | ECS | Posters on site | GD1.1

Spatial and temporal variation in dynamic mantle support of the Antarctic plate: Implications for ice sheet evolution 

Aisling Dunn, Nicky White, Robert Larter, Megan Holdt, Simon Stephenson, and Chia-Yu Tien

Accurately constraining past and future ice sheet evolution requires a quantitative understanding of key boundary conditions in ice sheet models, including topography and heat flux. Both of these conditions are in part moderated by spatially and temporally variable mantle dynamics. This study exploits an interdisciplinary approach to probe the mantle beneath Antarctica to better understand sub-crustal processes. First, observed bathymetry and topography are corrected for isostatic effects to isolate the residual topographic signal, a proxy for dynamic mantle support. In this way, a comprehensive suite of oceanic residual depth (n = 1120) and continental residual elevation (n = 237) spot measurements are calculated. Secondly, basaltic rare earth element concentrations acquired from an augmented database of Neogene volcanic samples (n = 264) are inversely modelled to determine melt fraction as a function of depth. Thus, we constrain mantle potential temperature and depth to the top of the melting column (i.e. lithospheric thickness). Finally, results from these approaches are interpreted alongside other geological and geophysical data, including free air gravity anomalies and mantle tomographic models to understand present day mantle-lithosphere interactions. Sequence stratigraphic analysis along continental margins (e.g. offshore from Dronning Maud Land and the Wilkes and Aurora Subglacial Basins) is also used to constrain temporal changes in mantle-induced vertical plate motion. Robust observations in the oceanic realm evidence dynamic support beneath the central Scotia Sea, the Marie Byrd Seamounts, in the vicinity of the Astrid Ridge, and beneath the Emerald Fracture Zone. Residual topography measurements define the extent to which these dynamic swells continue onto the continent, with 1-2 km of mantle support throughout West Antarctica, the Transantarctic Mountains, and the Gamburtsev Subglacial Mountains. Collectively, these results highlight considerable spatial and temporal variation in dynamic mantle support throughout Antarctica, making it imperative to account for such mantle-lithosphere interactions when modelling the onset and evolution of glaciation.

How to cite: Dunn, A., White, N., Larter, R., Holdt, M., Stephenson, S., and Tien, C.-Y.: Spatial and temporal variation in dynamic mantle support of the Antarctic plate: Implications for ice sheet evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-440, https://doi.org/10.5194/egusphere-egu24-440, 2024.

EGU24-1686 | ECS | Posters on site | GD1.1

Detecting subduction-related metamorphic events during the early Brasiliano Orogeny in southern Borborema Province using detrital rutile  

Rodrigo I. Cerri, Fabricio A. Caxito, Christopher Spencer, George L. Luvizotto, George W.C. Junior, Nayara M. Santos, and Lucas V. Warren

The ubiquity of detrital zircon in clastic sediments and their typical high U and low common Pb contents, resulting in relatively high precision U-Pb age determination, made zircon one of the primary minerals for provenance studies. Yet, its high closure temperature (>900oC), limited growth of new zircon under upper amphibolite-eclogite facies, inherited bias towards zircon-rich sources (e.g., felsic plutonic rocks), and the refractory behavior in sedimentary deposits rarely representing first-cycle sedimentation, can hamper the ability to detect some key tectonomagmatic events. In this sense, other mineral assemblages, like detrital rutile, that is formed in medium- to high-grade metapelite and metabasite mainly during high-pressure and low-temperature subduction metamorphism, can be used to provide a more complete record of orogenesis with polyphase evolution. Herein, we present U-Pb detrital rutile ages from the Cambrian-Ordovician Tacaratu Formation (lowermost unit of the late Jurassic to Cretaceous Tucano-Jatobá Basin, that directly overlies the Borborema Province in its southern region) to track the complete polyphase evolution of southern Borborema Province in the northeastern Brazil. The geodynamic evolution of this structural province is still a matter of debate, with interpretations varying from reworking of Paleoproterozoic continental crust with sedimentation and metamorphism in intracontinental setting, to oceanic closure during a complete Wilson Cycle with or without terrane accretion. Considering the southern Borborema Province Sergipano Belt, subduction started ca. 740 Ma ending with collisional processes (ca. 590-570 Ma) associated with the closure of the Sergipano-Oubanguides oceanic basin. The Neoproterozoic Pernambuco-Alagoas Domain and Sergipano Belt, both formed due to the collision between São Francisco-Congo Craton and the Pernambuco-Alagoas superterrane, are the main source of detritus of the Tacaratu Formation. Coupled U-Pb detrital zircon and rutile analysis revealed that detrital zircon ages lags (i.e., are younger) detrital rutile ages by around 100 Ma. Detrital rutile and zircon present main young peaks at ca. 650 Ma and 545 Ma, respectively. Recently, Neoproterozoic arc-back-arc amphibolite (ca. 743 ± 3 Ma), a rare setting for the early phases of Brasiliano Orogeny, and Cordilleran-type medium- to high-K granites (ca. 645-610 Ma), were recognized in southern Borborema Province, in agreement with our detrital rutile U-Pb ages. Thus, our detrital rutile ages record earlier phases of Brasiliano Orogeny in the southern Borborema Province (subduction-related metamorphism; closure of Sergipano-Oubanguides ocean), since the Brasiliano Orogeny culminated in the collision of blocks that were followed by high-temperature metamorphism (hampering the formation of younger rutile?). Notwithstanding, detrital rutile ages interesting marks around late Tonian to Cryogenian subduction-related metamorphism, perhaps in a magma-poor orogenic phase.

How to cite: Cerri, R. I., Caxito, F. A., Spencer, C., Luvizotto, G. L., Junior, G. W. C., Santos, N. M., and Warren, L. V.: Detecting subduction-related metamorphic events during the early Brasiliano Orogeny in southern Borborema Province using detrital rutile , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1686, https://doi.org/10.5194/egusphere-egu24-1686, 2024.

EGU24-2023 | Orals | GD1.1 | Highlight

Morphology, structure and gravitational instability of the steep caldera walls of Tambora (Indonesia) influenced by hydrothermal alteration. 

Thomas R. Walter, Claire E. Harnett, Valentin R. Troll, and Michael J. Heap

Calderas are steep morphological and collapse basins that continue to reshape long after initial structural collapse. While large landslides are associated with caldera collapse and widen the basin, little is known about the morphological and structural changes that occur long after caldera formation. Here, we investigate the shape and slope of the Tambora caldera in Indonesia, which formed in 1815 during one of the most devastating eruptions of the past  centuries. The release of over 150 cubic kilometers of volcanic ash created a caldera 6 kilometers wide and 1250 meters deep, causing climatic effects worldwide. Here we explore an ultra-high-resolution dataset we generated from Pleiades, a tri-stereo satellite, that now allows us to apply computer vision approaches to study the morphology and geometry of the Tambora caldera. We generated a 12 million pixel point cloud resampled to a 1 m resolution Digital Elevation Model and a 0.5 m orthomosaic. We explore the dimension, slope, and outline of the caldera and find localized open fissures, tension cracks, and morphological scars. We also apply an unsupervised image classification approach to the stereo multispectral data and find locations of fumarole activity and hydrothermal alteration in close proximity to these structural features. Hydrothermal alteration sites are commonly located in the caldera wall below the scars and open fissures. We explore this proximity of alteration, scarring, and faulting using newDistinct Element Method models, emphasizing that caldera morphology and structure is strongly influenced by hydrothermal weakening that causes flank instability, localized shedding of material, and large-scale morphological changes.

How to cite: Walter, T. R., Harnett, C. E., Troll, V. R., and Heap, M. J.: Morphology, structure and gravitational instability of the steep caldera walls of Tambora (Indonesia) influenced by hydrothermal alteration., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2023, https://doi.org/10.5194/egusphere-egu24-2023, 2024.

EGU24-2321 | ECS | Orals | GD1.1

Cenozoic asthenospheric flow history in the Atlantic realm: Insights from Couette/Poiseuille flow models 

Zhirui Ray Wang, Ingo L. Stotz, Hans-Peter Bunge, Berta Vilacís, Jorge N. Hayek, Sia Ghelichkhan, and Sergei Lebedev

Mantle convection is an essential component of the Earth system. Yet its history is not well known , in part, as the strength of tectonic plates conceals the underlying flow. To date, global mantle convection models have reached an impressive level of sophistication due to significant advancement of computational infrastructures and numerical techniques. This ultimately allows geodynamicists to reconstruct past mantle states through using, for instance, inverse geodynamic models based on adjoint equations. However, key input parameters of these models --- such as thermo-chemical flow properties and rheology --- are complex and poorly known. This in turn limits their ability to effectively interpret the reconstructed mantle flow, thus motivating one to pursue an approach that aims to conceptualize paleo-mantle-flow at a simple analytical level.

To this end, the existence of thin, mechanically weak asthenosphere permits one to develop an analytical Couette/Poiseuille model of asthenospheric flow, where flow is associated with moving tectonic plates, and with lateral pressure gradients due to rising plumes and sinking slabs. Here we present estimates of the Cenozoic asthenospheric flow history from such models in the Atlantic realm. We, moreover, link them to azimuthal seismic anisotropy as well as mantle flow retrodiction simulated by inverse geodynamic models. Our analytically derived asthenospheric flow indicates that it is in broad agreement with the orientation of seismic azimuthal anisotropy, and with the large-scale flow patterns from mantle flow retrodictions. In light of these results, our study suggests exploiting a hierarchy of geodynamic models together with growing observational constraints on mantle flow induced surface expressions to gain a better understanding of paleo-mantle-flow.

How to cite: Wang, Z. R., Stotz, I. L., Bunge, H.-P., Vilacís, B., Hayek, J. N., Ghelichkhan, S., and Lebedev, S.: Cenozoic asthenospheric flow history in the Atlantic realm: Insights from Couette/Poiseuille flow models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2321, https://doi.org/10.5194/egusphere-egu24-2321, 2024.

EGU24-2631 | Orals | GD1.1 | Highlight

River incision on hotspot volcanoes: insights from paleotopographic reconstructions and numerical modelling 

Loraine Gourbet, Sean F. Gallen, Vincent Famin, Laurent Michon, Miangaly Olivia Ramanitra, and Eric Gayer

The influence of climate on landscape evolution in natural settings remains debated. Here, we focus on tropical hotspot volcanic islands because they exhibit relatively uniform lithology and experience significant precipitation and climate gradients. Furthermore, intermittent volcanic flows effectively “reset” the landscape that begins to evolve post-eruption. Thus, we can constrain initial conditions by reconstructing the initial geometry of radiometrically dated volcanic flows. We constrain landscape evolution through time in several volcanic islands with strong climate gradients to assess the role of climate on incision. We perform topographic reconstructions to calculate long-term basin-averaged erosion rates in two islands of the Réunion hotspot (Réunion, Mauritius) and compile published erosion rates on Réunion and Kaua’i (Hawaii hotspot). We define the time since incision started as the age of the surface incised lava flow. To calibrate incision parameters on all three islands, we use the stream power model and apply a data-driven Bayesian approach to obtain the erodibility, K, the drainage area exponent, m, and the slope exponent, n. We also calculate a normalized erodibility index, Kn, using n = 1 to directly compare results among the different study sites. Erosion rates of Réunion Island range from 9.9 ± 0.5 mm/yr to 5.2 x 10-3 ± 2 x 10-4 mm/yr and erosion rates in Mauritius Island range from 6.5 x 10-2 ± 8 x 10-3 mm/yr to 5.1 x 10-3 ± 4 x 10-4 mm/yr. Incision efficiency seems to decrease with time since incision started from 63 ka to ~300 ka and then does not vary significantly with time since incision started from ~300 ka to 4300 ka. This is likely due to the covariation between the age of volcanism repaving and precipitation rates on Réunion, which is related to the configuration of the island’s two volcanoes – the active Piton de la Fournaise located on the windward side and the dormant Piton des Neiges on the center and leeward side. Our empirical calibration of the stream power law shows high dispersion in n and Kn on each individual island. m ranges from 0.2 to 2.9, and Kn ranges from 2.3 x 10-7 to 9.8 x 10-4 m1-2m/yr. For Réunion, we identify a positive trend between mean annual precipitation and erosion rates, and between mean annual precipitation and Kn, for low to moderate erosion rates (<1 mm/yr). For all basins of Réunion, there is also a positive trend between mean annual cyclonic precipitation rates and erosion rates, and between mean annual cyclonic precipitation rates and n. In Kaua’i, there is a positive trend between erosion rates and mean annual precipitation, consistent with previous studies. In Réunion, the proportionality coefficient between erosion and mean annual precipitation is three times greater than in Kaua’i. In addition, considering all three islands, a nonlinear relationship exists between channel slope and incision rate: best-fit n values range from 0.5 to 6, with n generally lower than one on Kaua’i. Our results highlight different sensitivities of fluvial relief to incision, and of incision to climate, between Kaua’i and Réunion islands.

 

How to cite: Gourbet, L., Gallen, S. F., Famin, V., Michon, L., Ramanitra, M. O., and Gayer, E.: River incision on hotspot volcanoes: insights from paleotopographic reconstructions and numerical modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2631, https://doi.org/10.5194/egusphere-egu24-2631, 2024.

The basal Cambrian sandstone unit in the North China craton (NCC) is an example of globally widespread siliciclastic succession that resides on the Great Unconformity and deposited on a hypothesized low-lying peneplain during the Cambrian global eustatic sea-level rise. Detrital zircon age signatures from this distinct sequence enable recognition of the ancient drainage system of the NCC in deep time and track its potential linkage with the Gondwana landmass. LA-ICP-MS U–Pb dating of the fossil-calibrated basal Cambrian (Series 2) detrital zircon samples from seven measured sections reveal marked spatial changes in their age signatures that can be divided into three distinct types. The first is generally characterized by the bimodal age populations with broad peaks at ~1.85 Ga and ~2.5 Ga that correlate with the Archean to Paleoproterozoic basement inboard of the NCC. The second is featured by multi-modal distribution with diagnostic Neoproterozoic peaks that correspond to subregional magmatic record. The third also shows multiple-zircon age populations, but yields significant crystallization ages close to the early Cambrian age. Comparing our new data with existing age spectra for the Cambrian strata across the NCC and the northern Gondwana demonstrates that separate drainage systems did exist in the peneplained basement during global Cambrian transgression and the basal Cambrian unit in the NCC was not a part of the far-travelled sand sheet across the northern margin of Gondwana. The most suitable source for Cambrian-aged grains constrained by paleogeographic restoration is the arc terrane developed along the northern margin of the NCC as a result of subduction of the Paleo-Asian oceanic plate. Our new continental-scale detrital zircon provenance signatures in the basal Cambrian unit suggest that the NCC should be considered a discrete continental block separated by the Proto-Tethys Ocean in the Cambrian, rather than an integral part of the northern Gondwana.

How to cite: Wei, R. and Duan, L.: Detrital zircon age signatures of the basal Cambrian sandstone unit in North China: implications for drainage divides during global Sauk transgression and separation from Gondwanaland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2721, https://doi.org/10.5194/egusphere-egu24-2721, 2024.

EGU24-2858 | ECS | Orals | GD1.1

Deriving mantle temperatures from global seismic models: A quantitative analysis in the light of uncertain mineralogy and limited tomographic resolution 

Gabriel Robl, Bernhard Schuberth, Isabel Papanagnou, and Christine Thomas

Mantle convection is driven by buoyancy forces in Earth’s interior. The resulting radial stresses generate vertical deflections of the surface, leaving traces in the geological record. Utilizing new data assimilation techniques, geodynamic inverse models of mantle flow can provide theoretical estimates of these surface processes, which can be tested against geological observations. These inverse models are emerging as powerful tools, providing the potential for tighter constraints on the relevant physical parameters governing mantle flow.

The geodynamic inversions mentioned above require an estimate of the present-day thermal state of the mantle, which can be derived from seismic observations. Using thermodynamically self-consistent models of mantle mineralogy, it is possible to convert the seismic structure imaged by global tomographic models to temperature. However, both seismic and mineralogical models are significantly affected by inherent limitations and different sources of uncertainty. In addition, owing to the complexity of the mineralogical models, the relation between temperature and seismic velocities is highly non-linear and not strictly bijective: In the presence of phase transitions, different temperatures can result in the same seismic velocity, making the conversion from seismic heterogeneity to thermal structure non-unique.

We investigate the theoretical ability to estimate the present-day thermal state of the mantle based on tomographic models in the case of isochemical convection. The temperature distribution from a 3-D mantle circulation model with earth-like convective vigour serves as the “true” temperature field. Using a closed-loop experiment, we aim to recover this initial model after: 1) mineralogical mapping from the “true” temperatures to seismic velocities, 2) application of a tomographic filter to mimic the effect of limited tomographic resolution, and 3) mapping of the “imaged” seismic velocities back to temperatures. We test and quantify the interplay of smoothed seismic structure due to tomographic filtering with different approximations for the conversion from seismic to thermal structure. Additionally, owing to imperfect knowledge of the parameters governing mineral anelasticity, we test the effects of changes to the anelastic correction applied in the mineralogical mapping. The observed mismatch between the recovered and initial temperature field is dominated by the effect of tomographic filtering, with a depth-dependent average error of up to 200 K. Additionally, we observe systematic large errors in the vicinity of phase transitions. Our results highlight that, given the current limitations of tomographic models and the incomplete knowledge of mantle mineralogy, magnitudes and spatial scales of a temperature field obtained from global seismic models will deviate significantly from the true state, even under the assumption of purely thermally driven mantle flow. Strategies to estimate the present-day thermodynamic state of the mantle must be carefully selected to minimize additional uncertainties.

How to cite: Robl, G., Schuberth, B., Papanagnou, I., and Thomas, C.: Deriving mantle temperatures from global seismic models: A quantitative analysis in the light of uncertain mineralogy and limited tomographic resolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2858, https://doi.org/10.5194/egusphere-egu24-2858, 2024.

Global plate reconstructions that constrain the surface plate motions provide crucial boundary conditions for mantle circulation models. Earth-like plate kinematics could reduce the impact of the uncertain mantle initial conditions and generate slab structures in the mantle that are comparable with seismic tomographies. However, due to the subduction of the oceanic plates, uncertainty increases in global plate reconstruction over time. Here, we utilize a novel slab unfolding technique to retrodeform mantle slabs imaged in the MITP08 seismic topography back to the pre-subduction states at Earth’s surface. Such a technique provides additional constraints on plate reconstructions, especially in regions dominated by intra-oceanic subductions, such as Southeast Asia.

Our reconstruction shows a significant trench retreat along Southeast Asia and Northern Australia between 90 and 65 Ma that opened a gigantic, >3,000 km wide backarc basin. This basin, named the East Asian Sea plate, was later consumed by the west-moving Philippine Sea plate and North-moving Australian plate in the Cenozoic. We then embed our reconstruction in a mantle circulation model, TERRA, testing the fidelity of the reconstruction in a closed-loop experiment.

We found that fragmented, sub-horizontal East Asian Sea slabs can be reproduced in the mantle circulation model. These slabs lying underneath the current Philippine Sea plate and northern Australia are similar to the MITP08 tomography on which the reconstruction is built. Moreover, these slabs at 800-1000 km depths result in a more negative dynamic topography on the present Philippine Sea plates comparable with the observed residual topography. On the contrary, the traditional, Andean-style reconstruction can only produce positive dynamic topography. Other Mesozoic, intra-oceanic subductions in NE Asia and western North America embedded in our reconstruction also produce negative, yet smaller magnitude, dynamic topography, possibly due to the older subduction history and deeper slabs. We conclude the negative dynamic topography within the present Pacific plate is the result of ancient intra-oceanic subductions. 

How to cite: Chen, Y.-W., Bunge, H.-P., Stotz, I., and Wu, J.: Testing tomography-based plate reconstructions from a paired, inverse-forward closed-loop experiment in a mantle circulation model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3083, https://doi.org/10.5194/egusphere-egu24-3083, 2024.

EGU24-3473 | Posters on site | GD1.1

The gully system on the NW sector of La Fossa cone (Vulcano Island): 2D evolution and hazard implication 

Alessandro Fornaciai, Massimiliano Favalli, Luca Nannipieri, Agnese Turchi, Rosanna Bonasia, and Federico Di Traglia

The Island of Vulcano is the emerged portion of a composite volcanic edifice within the Aeolian volcanic archipelago, situated in the southern Tyrrhenian Sea. The remobilization, triggered by heavy rainfall, of loose volcaniclastic material from La Fossa cone and the generation of small debris flows are recurrent hazards on Vulcano. Although these debris flows generally transport small volumes of material, in the case of severe events, they can  be channeled along the roads, flood several buildings, inundate the main harbor, and eventually be discharged into the sea. Gravitational and erosive processes, mainly due to rainfall, have formed several gully systems around the La Fossa cone. The presence of gully systems along slopes enhances both runoff and downslope mass wasting, and, above all, the gullies themselves act as a source of mass wasting due to the collapse of their walls and the processes of aggradation and degradation of their beds. Therefore, understanding the behaviour of gullies and their response to rainfall is crucial for predicting the effects of environmental changes, whether climatic or volcanic, on gully dynamics. 

In the frame of "VOlcaniclastic debris flows at La Fossa cone (Volcano  Island): evolution and hazard implication (VOLF)" project funded by the Istituto Nazionale di Geofisica e Vulcanologia, we here analyze aerial photos of the NW sector of La Fossa cone to describe the evolution of its gully system from the 1954 to 2022. First, we create a georeferenced dataset of photos by orthorectifying existing photos and generating new ones through the Structure from Motion (SfM) method applied to Unmanned Aerial System (UAS) photos. Second, we describe the geomorphological features of the gullies in the NW sector of La Fossa cone, identifying features to be parameterized. Finally, we qualitatively and quantitatively describe their evolution over almost 70 years.  

This work aims to investigate the morphological evolution of the NW flanks of La Fossa cone, a crucial aspect for assessing hazards associated with volcaniclastic sediment-charged flows and floods on Vulcano Island. This is especially relevant in a scenario where ongoing climate changes may potentially disturb the current equilibrium, heightening the likelihood of short-term extreme rainfall events.

How to cite: Fornaciai, A., Favalli, M., Nannipieri, L., Turchi, A., Bonasia, R., and Di Traglia, F.: The gully system on the NW sector of La Fossa cone (Vulcano Island): 2D evolution and hazard implication, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3473, https://doi.org/10.5194/egusphere-egu24-3473, 2024.

The Cheakamus basalts are a set of ~31 km long, 1.65 km3 valley-filling olivine basalts which erupted into the glaciated Callaghan-Cheakamus Valley system of the Garibaldi Volcanic Belt (GVB), British Columbia. Combined paleomagnetic and radiometric (40Ar/39Ar) analysis dates the lavas as a short-lived (< 2 ka duration) eruption at 15.95 ± 7.9 ka (2σ); additional field evidence, including well-glaciated lava flow surfaces overlain by till, indicate the eruption coincided with the early stages of the Fraser Glaciation (LGM) at ~20-18 ka. The lavas preserve features indicative of a landscape hosting diverse and dynamic paleoenvironments. Subaerial eruption of basalt lava filled an ice-free Callaghan Creek drainage system before inundating and damming of the paleo-Cheakamus River, creating an upstream rising body of water. Periodic overtopping of the lava dam resulted in syn-eruptive intermittent flooding and overtopping of lavas expressed by discontinuous lenses of interflow sediment and well-developed entablatures in the upper portions of lava flows. Rare instances of enigmatic cooling columns indicate localized ice contact with glaciers that partially filled the Cheakamus Valley. Emplacement features and morphologies in the Cheakamus Valley have been heavily altered by the erosional overprinting of a glacial lake outburst flood (GLOF) that preliminary 10Be analysis dates at the close of the LGM (11-10 ka). Lavas in the Callaghan valley remain untouched by the GLOF. Their aerial extent and distribution, especially at high elevations in tributary valley mouths suggest bottlenecking and backing-up of lavas due to narrowing in valley topography. Current work combines field mapping and analogue modelling and aims to provide insight into the emplacement dynamics of effusive lavas in the steep, confined terrain of the BC Coast Mountains. Despite, and in part because of, their heavily modified morphology, the Cheakamus basalts act as an excellent recorder of both effusive volcanic processes and the paleoenvironments into which they erupted. Their thorough and accurate analysis is especially pertinent temporally, as they erupted during a time of glacial flux and can provide additional evidence for the timing and location of the advancing Cordilleran ice sheet. Spatially, the Cheakamus basalts are proximal to population centers and transport infrastructure and thus have implications for potential volcanic hazards and attendant risks, as any future effusive, valley-filling basaltic eruption from the GVB will likely share similar emplacement characteristics and processes.

How to cite: Borch, A., Russell, J. K., Barendregt, R., and Friele, P.: Emplacement and erosion of valley-filling basalt lavas in shifting Quaternary environments of the Garibaldi Volcanic Belt, British Columbia, Canada, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4176, https://doi.org/10.5194/egusphere-egu24-4176, 2024.

EGU24-4552 | ECS | Orals | GD1.1 | Highlight

Synthetic Hiatus Maps as a Tool for Constraining Global Mantle Circulation Models 

Hamish Brown, Berta Vilacís, Ingo Stotz, Yi-Wei Chen, and Hans-Peter Bunge
The transient uplift and subsidence of the Earth’s surface induced by mantle convection (dynamic topography) leaves an imprint on the stratigraphic record at inter-regional scales. Dynamically uplifted continental regions result in widespread erosional/non-depositional environments (sedimentary hiatus), while subsided regions result in continuous sedimentation. Thus, by mapping hiatus and no-hiatus signals on inter-continental scales, one gains a proxy for the long-wavelength uplift and subsidence associated with dynamic topography. In this contribution, we report on the use of hiatus maps as a constraint on mantle circulation models (MCMs), which make predictions of the history of dynamic topography. In order to make such a comparison, we filter the modelled dynamic topography through the available data points from the real maps to form hiatus/no hiatus signals. The resulting synthetic hiatus maps are then directly comparable to the true maps. By generating synthetic hiatus maps for a variety of high-resolution TERRA MCMs, we show that such maps allow for the falsification or verification of MCMs based on their prediction of dynamic uplift/subsidence events. We additionally find that eustatic sea-level variations are clearly highlighted by geological series in which the global ratio of hiatus/no-hiatus surfaces is significantly over-/under-predicted by the synthetic maps. We stress that, while plume histories in MCMs are constrained only by the surface tectonic history, this form of comparison paves the way for the validation of adjoint geodynamic models in which plume histories are constrained by seismic tomography.

How to cite: Brown, H., Vilacís, B., Stotz, I., Chen, Y.-W., and Bunge, H.-P.: Synthetic Hiatus Maps as a Tool for Constraining Global Mantle Circulation Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4552, https://doi.org/10.5194/egusphere-egu24-4552, 2024.

EGU24-6544 | Orals | GD1.1

The large-scale landscapes in SW Scandinavia and in SW India are the result of two episodes of Neogene uplift 

Peter Japsen, Paul F. Green, Johan M. Bonow, and James A. Chalmers

Peninsula India and Scandinavia are elevated passive continental margins (EPCMs) characterized by asymmetric relief with high mountains in the west and a gentle slope towards lowlands in the east.

New AFTA data from southern India reveal major Phanerozoic episodes of cooling, reflecting exhumation. Here we focus on the early Miocene episode possibly related to the hard India-Asia collision (van Hinsbergen et al. 2012). The Miocene exhumation resulted in a low-relief landscape; e.g. the Karnataka and Mysore plateaus (Gunnel and Fleitout, 1998) with residual regions of higher ground (e.g. Palani Hills). Today, these plateaus reach an elevation of 1 km along the coast of SW India, sloping towards the east. The Miocene peneplains were graded towards the base level of the adjacent ocean (Green et al. 2013), and therefore reached their present elevation after their formation. Thick piles of Pliocene sediments off SW India (Campanile et al. 2008) suggests that this happened during the Pliocene.

Richards et al. (2016) studied river profiles in Peninsula India and concluded that the regional tilt grew since 25 Ma, maintained by sub-lithospheric processes. However, we find that the relief is the result of two episodes: 1) Miocene peneplanation related to far-field stress. 2) Late Neogene, asymmetric uplift driven by sub-lithospheric processes.

We identified a similar development in SW Scandinavia, where two Neogene episodes of uplift and erosion define main features of the relief (Japsen et al. 2018): 1) Early Miocene uplift leading to formation of the Hardangervidda peneplain (possibly related to the hard India-Asia collision). 2) Uplift beginning in the Pliocene, raising Hardangervidda to its present elevation at 1.2 km. Pliocene uplift raised margins around the NE Atlantic with maximum elevations reached close to Iceland. This suggests support from the Iceland Plume due to outward-flowing asthenosphere extending beneath the conjugate margins (Rickers et al. 2013; Japsen et al. 2024). 
Lithospheric as well as sub-lithospheric processes appear to shape main features of EPCMs.

Campanile et al. 2008. Basin Research. Green et al. 2013. GEUS Bull. Gunnell, Fleitout 1998. ESPL. Japsen et al. 2018. JGSL. Japsen et al. 2024. ESR. Richards et al. 2016. G cubed. Rickers et al. 2013. EPSL.

How to cite: Japsen, P., Green, P. F., Bonow, J. M., and Chalmers, J. A.: The large-scale landscapes in SW Scandinavia and in SW India are the result of two episodes of Neogene uplift, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6544, https://doi.org/10.5194/egusphere-egu24-6544, 2024.

Deflection of the Earth’s surface supported by mantle flow, known as dynamic topography, is associated with a free-air gravity anomaly because such topography is not isostatically compensated. Consequently, the ratio of the gravity anomaly to the dynamic topography, known as the admittance, has been used to estimate the amplitude of dynamic topography, which can be difficult to measure directly. However, at long wavelengths (e.g., spherical harmonic degrees 2 to 6) both dynamic topography and gravity anomalies, and thus the admittance, are sensitive to the mantle’s viscosity structure. Previous studies [e.g., Colli et al., 2016] demonstrate a reversal in sign of the free-air gravity anomaly resulting from lower mantle structures as the viscosity of the lower mantle is increased. This indicates potential complexity for inferring long-wavelength dynamic topography from observations of gravity anomalies, because the upper-lower mantle viscosity contrast is poorly constrained. We further investigated the relationship between dynamic topography and gravity anomalies by introducing lateral viscosity variations into a finite element model of global mantle flow. We find that the gravity anomaly above lower mantle density heterogeneity can change dramatically as we begin to introduce different models for lateral viscosity variations into the upper and lower mantle viscosity fields. In such models we find that the sign of the admittance varies laterally, with the horizontal gradients in mantle viscosity perturbing mantle flow patterns in ways that produce large changes gravity anomalies and smaller changes in dynamic topography. A spatially-varying admittance will greatly complicate estimation of dynamic topography from observed gravity, and may help to explain mismatches between observations of dynamic topography and predictions made using global mantle flow models. On the other hand, the reconciliation of such mismatches may help to constrain viscosity heterogeneity in the lower mantle.

Colli, L., S. Ghelichkhan, and H. P. Bunge (2016), On the ratio of dynamic topography and gravity anomalies in a dynamic Earth, Geophysical Research Letters, 43(6), 2510-2516, doi:10.1002/2016GL067929.

How to cite: Conrad, C. P. and Ramirez, F.: Sensitivity of Long-Wavelength Dynamic Topography and Free-Air Gravity to Lateral Variations in Lower Mantle Viscosity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6721, https://doi.org/10.5194/egusphere-egu24-6721, 2024.

EGU24-6783 | Orals | GD1.1

Gully incision development on scoria cones: different behaviors in three volcanic fields reflect environmental conditions. 

Maria Cristina Zarazúa-Carbajal, Greg A. Valentine, and Servando De la Cruz-Reyna

A consequence of alluvial processes acting on scoria cones is the development of a drainage network composed of radially distributed rills and gullies parallel to the volcanic edifice's downslope direction. This work focuses on the quantification of the degree of development of the drainage network by applying the Average Erosion Index method to scoria cones from the arid to semi-arid Lunar Crater volcanic field and comparing with previously obtained results from two tropical volcanic fields (Sierra Chichinautzin volcanic field and Paricutin-Tancitaro region, both in central Mexico). The results show that the method helps to determine geomorphic age relations when calibrated separately for each field. Furthermore, the differences in the resultant rates at which AEI varies as a function of time obtained for the three studied fields indicate that the method provides a tool to quantify the effects of different alluvial rates at volcanic fields across various environments.

How to cite: Zarazúa-Carbajal, M. C., Valentine, G. A., and De la Cruz-Reyna, S.: Gully incision development on scoria cones: different behaviors in three volcanic fields reflect environmental conditions., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6783, https://doi.org/10.5194/egusphere-egu24-6783, 2024.

EGU24-6885 | Orals | GD1.1

Cumulative storage of magma in the Paricutin-Tancítaro region, Mexico, revealed by recurrent swarm seismicity and a high spatial density of morpho-chronometrically dated Holocene monogenetic cones. 

Servando De la Cruz-Reyna, María Cristina Zarazúa-Carbajal, Gema Victoria Caballero-Jiménez, and Ana Teresa Mendoza-Rosas

A region located in the SW sector of the Michoacán-Guanajuato monogenetic field, in central Mexico displays a high spatial density of scoria cones, mostly around Tancítaro, a large central volcano active in the middle Pleistocene. This region became well known when in 1943 a new volcano, Paricutin, was formed in a cornfield at 11 km to the NW of the extinct stratovolcano. The birth of Paricutin was preceded by significant swarm-type seismicity. Afterward, new seismic swarms were reported in the area in 1997, 1999, 2000, 2006, 2020, 2021, 2022, and 2023, with a mean recurrence interval of only 4 yr, most of them (not all) showing the characteristics of a magmatic origin.  Aiming to shed some light on the relation between the high density of monogenetic cones and the recurrent seismicity, we have made a morpho-chronometric estimate of the relative ages of 170 scoria cones located in the Paricutin-Tancítaro region (PTR) within latitudes 19°N and 20°N and longitudes -102.0° E and -102.7° using the Average Erosion Index (AEI) which quantifies the degree of alluvial erosion of scoria cones from a Fourier analysis of their level contours. Monogenetic activity began in the PTR at about 1 Ma, and the AEI analysis shows that such activity increased after the end of the Tancítaro activity, around 232 ka, and further increased in the Holocene when about one-third of the scoria cones in the region were formed, with a mean interval between eruptions between 120 and 240 yr. On the other hand, a detailed study of two of the most energetic seismic swarms, recorded in 2020 and 2021 shows that the magma intrusion volume required to produce the measured cumulative seismic moment of both swarms amounts to about 140 million cubic meters, which is seemingly insufficient to produce a Paricutin-size eruption, which ejected about 1.3 cubic km of magma. We thus propose a possible conceptual explanation of the recurrent emplacement of monogenetic volcanoes and the frequent seismic swarm activity in terms of a persistent magma source under the crustal extension of the PTR producing numerous dike and sill forming intrusions. In some cases, such intrusions may have a cumulative effect forming temporary magma reservoirs capable of producing new monogenetic eruptions. Assuming that about 0.5 to 1 cubic kilometer of magma needs to accumulate to begin an eruption, about 7 to 14 sizable (similar to the 2020-2021) swarms may then represent a significant precursor.    

How to cite: De la Cruz-Reyna, S., Zarazúa-Carbajal, M. C., Caballero-Jiménez, G. V., and Mendoza-Rosas, A. T.: Cumulative storage of magma in the Paricutin-Tancítaro region, Mexico, revealed by recurrent swarm seismicity and a high spatial density of morpho-chronometrically dated Holocene monogenetic cones., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6885, https://doi.org/10.5194/egusphere-egu24-6885, 2024.

EGU24-7187 | ECS | Posters on site | GD1.1

Spontaneous Formation of Mantle Wind by Subduction and Its Impacts on Global Subduction Asymmetry 

Youngjun Lee and Changyeol Lee

Various subduction zone characteristics, including the slab dip, plate velocity, seismicity, and back-arc stress regime, show the global asymmetry with respect to the subduction direction. In particular, the east-directed subducting slabs show shallow dips and slow convergences, contrast to the steep dips and fast convergences of the west-directed subducting slabs. To explain the global asymmetry, the westward lithospheric motion or the eastward mantle wind with respect to the underlying mantle and the overlying plate, respectively, have been proposed. However, the causative force for the lithospheric motion, the tidal force between the Earth and Moon, is only acceptable when the asthenospheric viscosity is dramatically low such as 1015 ~ 1016 Pa·s, which could not globally exist in the mantle. The causative force for the mantle wind has left unknown even though the impact of the mantle wind has been verified. Past studies have shown that slabs sinking into the lower mantle can cause global mantle flow. That is, the slabs sinking at the eastern and western trenches around the Pacific ocean can cause the global mantle flow above the low-viscosity liquid outer core, expressed as the mantle wind. Therefore, to verify whether the subducting slabs around the Pacific ocean cause the mantle wind, we conducted a series of 2-D numerical models using an annulus-shape model domain, which simplifies the subduction history in the paleo- and present-Pacific ocean. Along with an allowance of dynamic subduction, both the realistic mantle viscosity and the major phase transition in the mantle were considered. Results show that the global-scale mantle wind is spontaneously formed by the imbalance in lateral mantle stresses owing to the subducting slabs around the Pacific ocean when the slippery core-mantle boundary operates as a lubricant layer, and the direction and magnitude of the mantle wind are periodically changed every tens of million years. When he eastward mantle wind occurs, it induces the relative westward drift of the plate, and as a result, the westward plate velocity becomes greater than the eastward plate velocity with respect to the hotspot reference frame. Simultaneously, the mantle wind pushes the west-directed subducting slab toward the ocean, forming steep slab dips but does the east-directed subducting slab toward the arc, forming shallow slab dips, consistent with the present subduction asymmetry in the Pacific ocean. After that, the negative buoyancy of the shallow slab steepens the slab itself, changing the direction of mantle wind westward; the opponent slab dips and plate velocities occur in the subduction zones. This study reveals that the present subducting asymmetry is a snapshot expression of the evolving global mantle flow, formed by the subducting slabs.

How to cite: Lee, Y. and Lee, C.: Spontaneous Formation of Mantle Wind by Subduction and Its Impacts on Global Subduction Asymmetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7187, https://doi.org/10.5194/egusphere-egu24-7187, 2024.

EGU24-8475 | ECS | Posters virtual | GD1.1

Patterns of volcanic eruptions in connection to sea-level change 

Margherita Scala, Maria C Neves, and Stéphanie Dumont

Understanding the relationships between the onset of volcanic eruptions and external forcings, such as solid Earth and ocean tides, can help us to understand the underlying dynamics of volcanic processes and have implications for volcanic monitoring and prediction efforts.

Many studies that explored the relationship between tidal forces and volcanic activity have shown that certain phases of tidal cycles are associated with an increased likelihood of eruptions. At longer-time scales of hundreds of thousands of years, pronounced sea level variations related to ice melting or climatic and astronomical periodic variations have also been associated with pulses of volcanic activity.

Oceans participate in significant redistributions of mass that can affect the stress field within the Earth’s crust over different time scales. Considering that most volcanoes lie near, within or beneath the oceans we hypothesize that stresses induced by ocean loading participate in destabilizing volcanic dynamical systems and ultimately contribute to eruption triggering.

In a previous study we analyzed the worldwide number of monthly volcanic eruptions from the Global Volcanism Program and the global mean sea level between 1880 and 2009 using the Singular Spectrum Analysis time-series analysis technique. We found common periodicities and particularly multi-decadal components of similar periodicities of 20, 30 and 50 years present in both time-series.

In this work we further explore the connection between volcanic activity and sea level by mapping the spatial patterns of volcanic eruptions at the previously identified temporal scales of correlation, ranging from the fortnightly tide to cycles of approximately 100 years. Geographical Information System tools are used to create spatial data layers, perform spatial analysis, and provide geographical visualization. The analysis might reveal global conditions and space-time patterns favorable to eruption triggering.

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) –

UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020),

UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and

LA/P/0068/2020(https://doi.org/10.54499/LA/P/0068/2020).

How to cite: Scala, M., Neves, M. C., and Dumont, S.: Patterns of volcanic eruptions in connection to sea-level change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8475, https://doi.org/10.5194/egusphere-egu24-8475, 2024.

EGU24-8609 | ECS | Posters on site | GD1.1

Implications of dynamic topographic measurements along Africa’s passive margins 

Philippa Slay, Megan Holdt, and Nicky White

Earth’s topography is both isostatically and dynamically supported. Sub-crustal density anomalies, caused by convective mantle processes, generate transient vertical motion at Earth's surface, producing the dynamic component of topographic support. Residual depth measurements are a well-established proxy for quantifying dynamic topography on oceanic crust and provide an observation-led approach to probing mantle dynamics. A global database of residual depth anomalies compiled from seismic reflection profiles and wide-angle seismic experiments is augmented with results obtained from interpreting further seismic experiments in the oceans surrounding the African continent. Residual depth anomalies are calculated by isolating and removing isostatic signals arising from sediment loading and crustal heterogeneity. Following these corrections, observed water-loaded depth-to-basement is compared to that predicted by the plate cooling model, with deviation equal to the residual depth anomaly. Coverage surrounding the African continent is improved, particularly in the Gulf of Guinea and Mozambique Channel. Results are consistent with previous observations, showing dynamic support of ± 1 km out to and including spherical harmonic degree l = 40 (i.e. ~ 1000 km). Results are corroborated by independent geologic and geophysical markers of subsidence and uplift. For example, volcanism and slow shear-wave upper mantle velocity anomalies associated with the Cameroon Volcanic Line indicate dynamic support. Improving the spatial sampling of residual depth anomalies provides insight into the influence of convective circulation on Earth’s surface, culminating in a more robust database against which geodynamic models of mantle convection can be benchmarked.

How to cite: Slay, P., Holdt, M., and White, N.: Implications of dynamic topographic measurements along Africa’s passive margins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8609, https://doi.org/10.5194/egusphere-egu24-8609, 2024.

It is widely recognized that mantle dynamics and plate flexure both contribute to Earth’s topography and gravity fields at different wavelengths, yet the actual transition wavelength between them is not well quantified, ranging from ~100 km to ~1000 km. Here we use the observed relationship between topography and the free-air gravity anomaly fields (admittance) to infer the relative contribution of plate flexure and mantle dynamics based on mantle flow models which incorporate an essentially elastic plate. Global and regional Pacific Ocean data studies show that plate flexure and mantle convection potentially contribute to the topography and gravity for wavelengths larger than ~600 km. Plate flexure mainly contributes at wavelengths shorter than ~600 km and is consistent with the support of uncompensated topography for wavelengths shorter than ~200 km. To investigate the admittance associated with mantle dynamics at long wavelengths we have constructed mantle flow models based on a number of different seismic tomography models. The finite element software CitcomS was used to calculate mantle flow and related surface dynamic topography and associated free-air gravity anomaly. Admittance analysis in the Pacific Ocean from different mantle flow models show that the dynamic admittance is generally larger than the observed admittance, while the admittance from plate flexure is smaller than the observed admittance, suggesting that both mantle dynamics and plate flexure contribute to Earth’s topography and gravity at long-wavelengths. The difference between the dynamic admittance and the observed admittance is smallest for cases with temperature-dependent viscosity and weak asthenosphere, and the combined admittance in the presence of both flexure and mantle convection for these cases is generally consistent with the observed admittance. We use a new method to separate the effects of plate flexure and mantle convection to the topography and gravity fields at long wavelengths which has been developed from the plate flexure and dynamic admittances. We assume that the topography and gravity at long wavelength are the combination of plate flexure and mantle dynamics and further assume that the topography and gravity are linearly related through the admittance. The final separated dynamic topography in the Pacific Ocean is generally consistent with previously published residual topography studies at long-wavelengths.

How to cite: Yang, A., Watts, A., and Zhong, S.: Long-wavelength gravity and topography of the Pacific Ocean: Relative contribution of mantle dynamics and plate flexure , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9346, https://doi.org/10.5194/egusphere-egu24-9346, 2024.

EGU24-10128 | ECS | Orals | GD1.1

Exploring the potential of normal mode seismology for the assessment of geodynamic hypotheses 

Anna Schneider, Bernhard Schuberth, Paula Koelemeijer, Grace Shephard, and David Al-Attar

Fluid dynamics simulations are a powerful tool for understanding processes in the Earth's deep interior. Mantle circulation models (MCMs), for example, provide important insight into the present-day structure of the mantle and its thermodynamic state when coupled with mineralogical models, which is essential information for other fields in the geosciences. The evolution of the heat flux through the core-mantle boundary, for instance, is a prerequisite for geodynamo simulations that aim to model the reversal frequency pattern of the Earth's magnetic field on geologic time scales. However, geodynamical modelling requires extensive knowledge of deep Earth properties and plate motions over time. Uncertainties in these model inputs propagate into the MCMs, which subsequently have to be evaluated with independent data, such as the seismological or geological record. Although state-of-the-art MCMs typically explain statistical properties of seismological data, they do not consistently reproduce the location of features in the mantle.

In this contribution, we explore the effect of varying the absolute position of mantle structure on seismic data by applying first-order modifications to an initial MCM. Normal mode data are particularly well suited for assessing the resulting changes in the location of mantle structure, as they capture its long-wavelength component throughout the entire mantle. In addition, the global sensitivity of normal modes reduces the drawbacks of uneven data coverage. Specifically, we use two different seismic forward modelling approaches, an iterative direct solution method for computing full-coupling spectra and a splitting function calculation that is based on the self-coupling approximation. Our goal is to quantify the effects of a limited number of large-magnitude earthquakes, the adequacy of the self-coupling approximation, and the resolvability of relevant model differences through a comprehensive data analysis. Our synthetic forward modelling framework is moreover well suited for testing the depth sensitivity associated with specific frequency intervals in the spectrum that generally is inferred from seismic 1-D profiles within the splitting function approximation.

How to cite: Schneider, A., Schuberth, B., Koelemeijer, P., Shephard, G., and Al-Attar, D.: Exploring the potential of normal mode seismology for the assessment of geodynamic hypotheses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10128, https://doi.org/10.5194/egusphere-egu24-10128, 2024.

EGU24-10566 | ECS | Orals | GD1.1

Global assessment of tomographic resolution and uncertainty with the SOLA method 

Roman Freissler, Bernhard S.A. Schuberth, and Christophe Zaroli

Interpretations of seismic tomography and applications of the resulting tomographic images, e.g. for estimating present-day mantle temperatures, require information on their resolution and uncertainty. Assessing these model properties is often difficult due to the large size of tomographic systems on global scales. In consequence, there have been only few attempts to consistently analyse the spatially variable quality of tomographic images of deep mantle structure. For linear problems, both resolution and uncertainty can be quantified with the tools provided by classic Backus–Gilbert (B–G) inversion. In this theory, averaging kernels define the local resolving power at each model parameter, while uncertainties represent the propagation of data errors into the model values. By using a more efficient variant of B–G inversion, the method of 'Subtractive Optimally Localized Averages' (SOLA), global tomography can be performed with complete information for model appraisal.

Based on the SOLA framework, we present a concept for the assessment of the 3-D resolution information contained in a global set of averaging kernels. It is based on the rigorous estimation of resolution lengths from a 3-D Gaussian parametrization of the averaging kernels, together with a test for the robustness of this approximation. This is a necessary step because a perfectly bell-shaped or delta-like behaviour of resolution can not always be guaranteed in global tomography due to the inhomogeneous data coverage. Therefore, we also develop a classification scheme, which enables a basic identification of those averaging kernels that are too complex to be sufficiently described by the chosen definition of resolution length. We note that this approach is more generally applicable, i.e. it can be used with any explicitly available set of averaging kernels or point-spread functions, but also with alternative parametrizations.

In the context of the SOLA method, our resolution analysis can be further used to locally calibrate the inversion parameters. This involves on the one hand the specification of a target (resolution) kernel. On the other hand, a trade-off parameter needs to be selected that regulates the fit of the averaging to the target kernel, and the conversely affected propagation of data errors.

To this end, we apply our concept for robust resolution estimation to different sets of averaging kernels from SOLA inversions with varying parameter combinations. Most notably, we systematically increase the spatial extent of the target kernels (taken as 3-D Gaussian functions here as well). The final maps of global (and classified) resolution and uncertainty can be viewed together for a complete picture of the model quality. They reveal where, and for which target size and amount of error propagation, resolution lengths are meaningful and model values can be interpreted appropriately.

How to cite: Freissler, R., Schuberth, B. S. A., and Zaroli, C.: Global assessment of tomographic resolution and uncertainty with the SOLA method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10566, https://doi.org/10.5194/egusphere-egu24-10566, 2024.

We present a new book aimed at graduate students, and academics, as well as all volcano enthusiasts. We chose to publish on the topic of volcano geomorphology for two main reasons. Firstly, although several geomorphology textbooks have been published, ones focussed on volcano geomorphology are scarce or outdated and out of print (Cotton, 1944, McDonald, 1972; Ollier, 1969 and 1988). Secondly, many volcanology books have been published over the past few decades, but they do not describe landforms and geomorphic processes in sufficient detail (as stated by the late P. Francis in 1993). To our knowledge, only five modern books on volcanology include a chapter on volcanoes as landforms and landscapes (Francis, 1993 and Francis & Oppenheimer, 2004; Chester, 1993; Scarth, 1993; Lockwood and Hazlett, 2010). They are less process-oriented than modern books on geomorphology.

Our book on Volcano Geomorphology is organised into five main themes, and contains 10 chapters. The first theme is an overview of the geodynamic environments in which the Earth's volcanoes are createdThe second is a detailed account of elementary “constructional” landforms, from lava forms to monogenetic volcanoes, both terrestrial and subaqueous, reflecting a variable degree of magma-water interaction. The third deals with polygenetic volcanic edifices including shield volcanoes, composite cones and volcanic clusters. This is followed by landforms and processes that form calderas, caldera complexes, and volcano-tectonic depressions. The fourth is oriented towards the degradation of volcanoes by short- and long-term erosion processes. The fifth and final theme is twofold: first, we deal with geomorphic hazards on active and dormant volcanoes, along with five specific case studies of recent events; and lastly, we conclude with a chapter presenting a wide array of methods (morphometry, simulations of processes, structural geology, age determination, etc.) that are used to unravel processes on active and dormant volcanoes.
            In summary, our textbook aims to: (1) review the most recent research in geomorphology and physical volcanology, e.g. an improved classification and understanding of volcanic landforms, with respect to geodynamic settings, lithology, and climate; (2) update our knowledge of processes and rates of growth and destruction of volcanic landforms and landscapes by integrating recent results from the expanding sector of volcanology both in the field and in the laboratory; (3) consider how volcanic landforms, landscapes, and processes can be studied by reviewing classical and modern methods.  

In this way, we hope that our compilation, which provides a richly referenced and illustrated piece of work on volcano geomorphology, will be of interest to a broad audience. It is expected to be published later this year (2024).  

How to cite: Karátson, D. and Thouret, J.-C.: ‘Volcano Geomorphology: landforms, processes and hazards’  ̶̶ A new book in ‘Advances in Volcanology’ Collection, Springer Verlag , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11744, https://doi.org/10.5194/egusphere-egu24-11744, 2024.

EGU24-11817 | ECS | Orals | GD1.1

River dynamics in an active volcano with tropical humid conditions 

Sebastián Granados, Nicola Surian, and Guillermo E. Alvarado

 Active volcanic catchments within low-latitude tropical humid climates constitute some of the most dynamic and sediment-rich fluvial systems globally. The combination of factors such as active explosive vulcanism, frequent high-magnitude earthquakes, dense biodiverse vegetation, and intense rainfall leads to very high sediment supply and very active channel morphodynamics within such fluvial systems.

Our research focused on channel dynamics in three remote and challenging-to-access reaches of the Sucio River, situated within the Irazú stratovolcanic structure in Costa Rica's central volcanic chain. This unique setting experiences extreme conditions, including rainfall exceeding 8000 mm annually, infrequent but significant volcanic eruptions (occurring over three times per century), high-magnitude earthquakes (>Mw5), and dense pristine vegetation. The mapped river reaches within this active volcano exhibit a distinctive confined multi-thread channel morphology predominantly comprised of coarse sediments, notably boulders, displaying exceptional dynamism. These reaches showcase rapid shifts between braided, island-braided, and anabranching morphologies in relatively short periods (<20 yrs.). Additionally, the primary sediment sources located in crateric areas have undergone rapid and substantial changes, resulting in the emergence of large landslides and drastic alterations in vegetation.

Employing remote sensing techniques, geostatistical analysis, and fieldwork, we investigated the impacts of eruptions, earthquakes, and rainfall on the Sucio River's channel morphology and its primary sediment sources (craters) from 1961 to 2023. Over 65 images were processed to generate various derived raster products, including supervised classification datasets, change detection outputs, and morphometric parameters (such as channel width, braided index, anabranching index, and area of bars and islands). Moreover, we constructed a precipitation database spanning the study period to assess the frequency, magnitude, and duration of extreme rainfall events. Historical seismic data was utilized to compile a database of relevant earthquakes that might have affected the catchment, given the river's proximity to several active faults. Subsequently, exploratory statistical analysis employing linear regression models helped discern the influential factors behind channel dynamics and changes.

Our findings provide a novel understanding of how this specific fluvial volcanic environment responds to external perturbations and adapts its channel morphology over time. Key outcomes include the rarity of the multithread boulder morphologies observed in these reaches, rapid morphological transformations occurring within this multithread system in short intervals, the significant role of dense pristine vegetation in stabilizing banks and islands, and the cyclic stability-instability phases (erosion-deposition) triggered by pivotal events like eruptions, hurricanes, and high-magnitude earthquakes.

 

This study presents novel insights into channel morphology dynamics in one of Central America's most extensively studied active volcanoes, likely having the river transporting the most sediments in Costa Rica's volcanic regions.

How to cite: Granados, S., Surian, N., and Alvarado, G. E.: River dynamics in an active volcano with tropical humid conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11817, https://doi.org/10.5194/egusphere-egu24-11817, 2024.

EGU24-12015 | ECS | Orals | GD1.1

Unraveling Tasmania's Late Paleozoic Ice Age: Carbon Isotopic and Stratigraphic Signatures in Response to Glacial-Deglacial Cycles and Large Igneous Province (LIP) Events 

Wahyuningrum Lestari, Aisha Al Suwaidi, Calum Fox, Vivi Vajda, Andrea Ceriani, Yadong Sun, Joost Frieling, and Tamsin Mather

Late Paleozoic Ice Age (LPIA), which peaked during the mid Permian, resulting in widespread ice centers across Gondwana during its coldest periods. Assessing the climate change across this glaciation and the following deglaciation interval contribute important data not only in terms of understanding the end-Permian extinction event but also present-day global change. Tasmania, located in a high-latitude setting, forming a bridge between the continents Antarctica and Australia provides a valuable record of the environmental and climatic shifts that occurred in areas proximal to glaciation during the acme and waning stages of the LPIA.

At the time of glaciation, Tasmania was a distinct landmass located within the Paleo-Antarctic Circle at a paleo-latitude of ~78°S. Here we present new high-resolution bulk organic carbon isotope analyses (δ13CTOC), mercury, bulk and trace elemental and sedimentological data combined with palynology and conodont biostratigraphy from the late stage (P3 and P4) of the LPIA Glacial-Deglacial Episode III. We base the data on samples from the Bicheno-5 core, from Eastern Tasmania, which contains approximately 83 meters of middle Permian glaciomarine sediments.

Three negative carbon isotope excursions (CIEs) have been identified in the middle Permian (mPN1, mPN2, and mPN3). The latter two are correlated with the deglaciation episodes in Eastern Australia's glacial intervals P3 and P4 phases. Diamictites and dropstones are typically present in the sediments that record the most positive carbon isotope values, which likely correspond to the peak of the glaciation period. Elemental proxies indicate two cycles of increased weathering and terrestrial sediment influx to the marine system. These cycles coincide with the most negative carbon isotope values and are associated with deglacial cycles in Tasmania and within the paleo-Antarctic circle. The first deglacial cycle (mPN1) coincides with elevated mercury (Hg/TOC) which may hint at a link between deglaciation and volcanism, possibly from the Tarim III LIP.

Comparisons with similar records from the marine Pingdingshan (PDS) section in South China confirms that our data from Tasmania reflect global carbon cycle perturbations providing new insights into the significant global climatic shifts that occurred during the middle Permian. The end stage of the LPIA offers a unique comparison to modern environmental and climatic change in Antarctica associated with anthropogenic global warming.

How to cite: Lestari, W., Al Suwaidi, A., Fox, C., Vajda, V., Ceriani, A., Sun, Y., Frieling, J., and Mather, T.: Unraveling Tasmania's Late Paleozoic Ice Age: Carbon Isotopic and Stratigraphic Signatures in Response to Glacial-Deglacial Cycles and Large Igneous Province (LIP) Events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12015, https://doi.org/10.5194/egusphere-egu24-12015, 2024.

EGU24-12118 | ECS | Orals | GD1.1

Global continental hiatus surfaces as a proxy for tracking dynamic topography since the Upper Jurassic 

Berta Vilacís, Hamish Brown, Sara Carena, Hans-Peter Bunge, Jorge N. Hayek, Ingo L. Stotz, and Anke M. Friedrich

Mantle convection is a fundamental process governing the evolution of our planet. Buoyancies in the mantle induce horizontal and vertical motion of the Earth’s lithosphere, which can be mapped using independent geological datasets. Positive surface deflections induced by mantle convection create erosional/non-depositional environments which lead to gaps (hiatuses) in the stratigraphic record, while negative deflections provide accommodation space for sedimentation to occur. We use continental- and country-scale digital geological maps and regional and local stratigraphic studies at the temporal resolution of geological series (ten to tens of millions of years) to map the distribution of hiatus through geological time.

Here we present global continental hiatus surfaces since the Upper Jurassic. We find that they vary inter-regionally at timescales of geological series and that they correlate with known mantle dynamic events. For example, we tend to observe the appearance of a hiatus surface before the arrival of a mantle plume. In Europe, we mapped a large-scale sedimentary hiatus during the Paleocene, prior to the arrival of the Iceland plume. In Africa and South America, we found a widespread absence of the Upper Jurassic prior to the arrival of the Tristan plume. This pattern can be seen as characteristic of plume-induced dynamic uplift. We observe a sea level signal during some geological series, such as in the Oligocene, when there is a global increase of hiatus areas, coinciding with the onset of Antarctic glaciation and associated sea level drop. At other times, we find that the hiatus areas evolve differently for different continents, precluding their interpretation as an eustatic signal. Spectral analysis shows that hiatus surfaces have shorter wavelengths than no hiatus surfaces, requiring higher spherical harmonic degrees to describe the geological series with larger amounts of hiatus. These include the Upper Jurassic, the Paleocene, the Oligocene and the Pleistocene.

Our results imply that a key property of time-dependent geodynamic Earth models must be a difference in timescale between mantle convection itself and resulting dynamic topography. Moreover, they highlight the importance of continental-scale compilations of geological data to map the temporal evolution of mantle flow beneath the lithosphere, which can provide powerful constraints for global geodynamic models.

How to cite: Vilacís, B., Brown, H., Carena, S., Bunge, H.-P., Hayek, J. N., Stotz, I. L., and Friedrich, A. M.: Global continental hiatus surfaces as a proxy for tracking dynamic topography since the Upper Jurassic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12118, https://doi.org/10.5194/egusphere-egu24-12118, 2024.

While the isostatic compensation of crustal thickness and density heterogeneity provides the dominant contribution to Earth’s observed topography, there nonetheless remains a substantial difference (the ‘residual topography’) between these two fields. This difference is a consequence of dynamic processes occurring within the mantle, most notably due to time-dependent vertical surface stresses driven by mantle convection. Mantle convection dynamics also produce differences between the observed geoid and the isostatic geoid generated by crustal heterogeneity: the ‘residual geoid’. The joint consideration of both residual geoid and topography anomalies provides unique and fundamental global constraints on the amplitude and spatial distribution of density anomalies in the convecting mantle.
Despite the crucial role of isostasy in determining residual geoid and residual topography, accurate constraints depend heavily on the quality of the isostasy calculations. The classical theory of isostasy relies on a 1st-order treatment of hydrostatic equilibrium, which is not sufficiently accurate for the calculation of isostatic geoid anomalies on a compressible, self-gravitating mantle. Consequently, we present a geodynamically consistent approach that is based on the surface loading response (via dynamic kernels) calculated with a viscous flow model that incorporates a fully compressible mantle and core (given by the PREM reference model) with self-gravitation.
Another critical issue that remains outstanding is the accuracy inherent in global crustal heterogeneity models. Here we show that the differences between the residual geoid and topography fields predicted using CRUST1.0 (Laske et al. 2012) and the most recent ECM1 (Mooney et al. 2023) crustal heterogeneity models are substantial. We discuss the importance and implications of these differences in the context of determining the most accurate constraints on density anomalies in the convecting mantle.

How to cite: Kamali Lima, S., Forte, A. M., and Greff, M.: A Geodynamically Consistent Approach to Residual Topography and Geoid Anomalies on the Convecting Mantle: Importance of Global Crustal Models , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12457, https://doi.org/10.5194/egusphere-egu24-12457, 2024.

EGU24-13012 | ECS | Orals | GD1.1

Modelling volcano degradation through analogue experiments: the impact of volcano slopes and summit craters on erosion patterns 

Roos M. J. van Wees, Engielle Paguican, Daniel O'Hara, Gabor Kereszturi, Pablo Grosse, Pierre Lahitte, and Matthieu Kervyn

Analogue experiments can enhance our understanding of complex natural volcanic landscapes formed by eruptions, intrusions, remobilisation of volcanic material and erosional processes. Experimental setup in a laboratory offers a controlled setting to investigate the development of rainfall-induced radial drainage basins on scaled volcano cones. It allows to simulate surface runoff, a prominent sediment transport process in volcanic landscapes, primarily influenced by climate, lithology, and topography. By controlling the flowrate within the setup, maintaining a uniform lithology, and using initial axisymmetric cones with the same size, this study aims to record the variations in erosion patterns caused by systematic cone slope and shape changes.

Analogue volcanic cones made up of water-saturated 70 μm silica powder were built upon a drainage layer of coarse sand at the VUB volcanology analogue laboratory. The cones were scaled based on the height/basal width ratios of natural pristine composite volcanoes with a scaling factor of 4.5*10-6 for the basal width. Initial cones had basal widths of 33 cm with two sets of cones with heights ranging from 4.2 to 6.9 cm. For the highest cones, the lower flank was 21 degrees and the upper slope 30 degrees, with a break-in-slope at 45% of the cone height. Experiments included cones with and without summit craters, the craters were 5 cm wide and 0.5 cm deep. Rainfall-induced erosion was simulated with two atomizer sprinklers, creating a mist of droplets of circa 30 μm. Experiments were run for 3 to 5 hours, simulating erosion taking place over several millions of years at natural volcanoes. We generated a minimum of ten Digital Elevation Models (DEMs) by photogrammetry with sub-millimetre spatial resolution, enabling the estimation of volume loss and erosion rates. The automated algorithms MorVolc and DrainageVolc were used to extract morphometric and drainage parameters (e.g., height/basal width ratio, drainage density, irregularity index) from the DEM of each timestep.

The analogue models' drainage networks and morphological characteristics replicate those found on natural volcanoes. Having a steeper slope for the upper flank of the cone delayed the forming of erosional features on the lower flank, while the top part of the volcano incised deeper than the cones with one slope gradient. The cones without a summit crater develop a radial drainage network from an initial set of narrow gullies to a more stable pattern with fewer valleys that gradually widen. The introduction of a summit crater substantially modifies the resulting erosional patterns: the incision of the crater rim forms two to four dominant watersheds that widen faster than the basins of cones lacking a crater. Migration of drainage divides ceases when equilibrium in the landscape is attained, with cones featuring a summit crater reaching this equilibrium later than those without. Analogue experiments are a valuable tool for studying erosional processes in a controlled manner and give insight into complex volcanic landscapes, thereby improving our understanding of long-term volcanic landscape evolution.

How to cite: van Wees, R. M. J., Paguican, E., O'Hara, D., Kereszturi, G., Grosse, P., Lahitte, P., and Kervyn, M.: Modelling volcano degradation through analogue experiments: the impact of volcano slopes and summit craters on erosion patterns, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13012, https://doi.org/10.5194/egusphere-egu24-13012, 2024.

Understanding the interaction between oceanic plates and the underlying asthenosphere and its impact on plate thickness is essential for explaining plate motions and mantle convection patterns. While sub-lithospheric small-scale convection provides an explanation for why oceanic plates do not continue to thicken after a certain age, many open questions still surround this process. Here, we link dynamic models of mantle flow, grain-scale processes, seismic imaging, and surface observations to gain new insights into the mechanisms of asthenospheric small-scale convection and its surface expressions.

We have performed a series of high-resolution 3D numerical models of the evolution of oceanic plates and the development of thermal instabilities at their base using the open-source geomodeling software ASPECT. These simulations use an Earth-like rheology that includes coupled diffusion and dislocation creep as well as their interplay with an evolving olivine grain size. Our models quantify how the effective asthenospheric viscosity and the balance between diffusion and dislocation creep affect the morphology and temporal stability of small-scale sub-lithospheric convection, including the age of its onset, the average depth and wavelength of the small-scale convection rolls, and the amplitude of the temperature and grain size anomalies within the rolls.

All of these quantities predicted by the dynamic models can be directly related to both geophysical observables and to surface manifestations such as dynamic topography and heat flux. To accurately compare our model outputs to geophysical data, we convert them to seismic velocity and attenuation using laboratory-derived constitutive relations and taking into account variations in temperature, pressure, grain size, water content and calculated stable melt fraction. We then create synthetic seismic tomography models of different dynamic scenarios and analyze their fit to observations from the Pacific OBS Research into Convecting Asthenosphere (ORCA) experiment. Comparison with both seismic imaging and surface expressions allows us to determine the parameter range in which geodynamic models fit these observations, providing new constraints on the convection patterns and the rheology of the oceanic asthenosphere beneath the Pacific Plate.

How to cite: Dannberg, J., Eilon, Z., Russell, J. B., and Gassmoeller, R.: Sub-Lithospheric Small-Scale Convection as a Window into the Asthenosphere: Insights from Integrating Models Of Mantle Convection, Grain Size Evolution and Seismic Tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13895, https://doi.org/10.5194/egusphere-egu24-13895, 2024.

EGU24-15103 | Posters on site | GD1.1

Understanding volcanic edifice erosion and morphologic evolution using numerical models 

Daniel O'Hara, Liran Goren, Benjamin Campforts, Roos van Wees, María Cristina Zarazúa-Carbajal, and Matthieu Kervyn

Volcanic edifices are dynamic landforms whose morphology encodes the long-term (thousands to millions of years) interplay between construction and erosion. Short-term, stochastic episodes of volcanic activity cumulatively build topography, competing with stochastic erosive processes associated with climate and mass wasting to degrade edifices over longer timescales, thus generating a variety of morphologies from simple, cone-like edifices to complex, non-axisymmetric volcanoes. Understanding how these processes interact to shape volcano morphologies over the landform’s lifespan is still in its infancy, especially as construction and erosion are often spatially-heterogeneous and temporally-varying. Despite this, disentangling edifice morphologic histories provide new avenues to better discern an edifice’s volcanic record, assess potential hazards, and quantify the role of climate in landscape evolution.

Numerical modeling has been shown to be a useful approach to exploring long-term landscape evolution. Although the majority of studies have applied landscape evolution models to tectonic settings, modeling has also been applied to simulate erosion and drainage development for specific volcanic features (e.g., channel incision on shield volcanoes, soil diffusion on cinder cones). However, thus far no modeling frameworks have been developed to explore evolution over the full spectrum of edifice types

Here, we investigate volcanic edifice erosion and drainage basin formation using a simplified landscape evolution model. Assuming that the various erosive processes that shape a volcano can be simplified to the competition between advection and diffusion, we use common transport laws (stream power law and linear soil diffusion) to conduct a nondimensional parameter analysis. We then test various parameter combinations to demonstrate the range of morphologic evolutions that can occur over different edifice classifications and environments. Afterwards, we compare our results to previously-derived relationships of natural volcano evolutions to test the ability for simplified models to recreate nature. Finally, we explore the effects of edifice size on the competition between incision- and diffusion-based erosion within the framework of our nondimensional parameters by quantifying drainage development of 156 cinder cones from the Springerville Volcanic Field (AZ, U.S.) and comparing these to both edifice age and planform area.

Our results demonstrate that simplified numerical models are able to recreate the trends observed in nature. Furthermore, we show that the combination of model parameters predicts threshold sizes that volcanic edifices must overcome to begin generating fluvial drainage networks and becoming incised by gullies, broadly inferring parametric thresholds that describe the ratios of erosion processes on these landforms. Our results thus establish a new foundation to study edifice morphologies over several volcano types (cinder cones, shield volcanoes, composite volcanoes) and construction styles (intrusion-driven surface uplift, mantling by lava flows and ash deposits), and provides a basis to test how volcanic environments respond to past and future changes in climate and tectonics.

How to cite: O'Hara, D., Goren, L., Campforts, B., van Wees, R., Zarazúa-Carbajal, M. C., and Kervyn, M.: Understanding volcanic edifice erosion and morphologic evolution using numerical models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15103, https://doi.org/10.5194/egusphere-egu24-15103, 2024.

EGU24-15374 | Orals | GD1.1

A Southern Hemisphere Chronostratigraphic Framework for the Pliensbachian–Toarcian Carbon Cycle Perturbations 

Aisha Al-Suwaidi, Micha Ruhl, David Kemp, Marisa Storm, Stephen Hesselbo, Hugh Jenkyns, Tamsin Mather, Lawrence Percival, and Daniel Condon

Lower Jurassic sedimentary successions from the Neuquén Basin, Argentina are unique in the abundance of radiometrically datable material (ash-beds) present, which can be tied to bio- and chemostratigraphic (carbon-isotope) zonations. Here, we present new U-Pb radio isotopic dates, integrated with carbon-isotope and Hg/TOC data, from three localities in Argentina (Arroyo Lapa, Arroyo Serrucho/Las Overas and Chacay Melehue) to generate a biostratigraphically calibrated composite carbon-isotope curve and geochronological framework for the Pliensbachian–Toarcian transition in South America. Using a Bayesian framework we present an age-depth model for this composite record and estimate the age and duration of key intervals extending from the Latest Pliensbachian carbon isotope excursion (CIE) through the Early Toarcian negative CIE. Using a  statistical analysis of all available Karoo and Ferrar Large Igneous Province (LIP ) U-Pb and Ar-Ar radioisotopic ages we create a timeline of the key events and examine the timing of the carbon cycle perturbations specifically looking at potential links to peaks of extrusive emplacement of the Karoo and Ferrar LIP. The geochronological framework is further compared with other available radioisotopic dates from correlative sections, allowing for a more precise constraint and validation of the timing and duration of these Early Jurassic events.

 

How to cite: Al-Suwaidi, A., Ruhl, M., Kemp, D., Storm, M., Hesselbo, S., Jenkyns, H., Mather, T., Percival, L., and Condon, D.: A Southern Hemisphere Chronostratigraphic Framework for the Pliensbachian–Toarcian Carbon Cycle Perturbations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15374, https://doi.org/10.5194/egusphere-egu24-15374, 2024.

EGU24-15516 | Orals | GD1.1

Uplift and erosion of an intraforeland topographic high: implication for the evolution of the Gondwanian Transantarctic foreland 

Valerio Olivetti, Silvia Cattò, Fabrizio Balsamo, Luca Zurli, Matteo Perotti, Gianluca Cornamusini, Marco Fioraso, Federico Rossetti, and Massimiliano Zattin

The Transantarctic Basin is a continental basin system developed for ca 200 Myr, from the Devonian to the Early Jurassic, along the Panthalassa margin of Gondwana and above the peneplained Ross Orogeny rocks. The Beacon Supergroup strata form the clastic sedimentary infill of the Transantarctic Basin.

Geodynamic interpretation of the Transantarctic Basin is not univocal and likely geodynamic conditions accounting for basin subsidence have been changed in space and time. Involvement of the basin into the Gondwanian orogenic deformation is a key question for defining the geodynamic setting and the tectonic environment during the Beacon Supergroup deposition. Nonetheless, involvement of  Beacon Supergroup  in orogenic shortening is  poorly assessed for the limited exposed rocks and because formation of the Cenozoic  Transantarctic rift shoulder modified the Paleozoic geometry of the Beacon strata.

Here we explored the exhumation pattern and thermal evolution of the basement rocks and the immediately overlain Beacon sandstones through low-temperature apatite fission track and (U-Th)/He zircon thermochronology along the Prince Albert Mts, where Beacon deposits are particularly thin to suppose a relevant erosional event during the Paleozoic. Thermochronological data and thermal modelling pointed out that basement rocks and Beacon sandstones of the Prince Albert Mts have preserved evidence of a Late Paleozoic erosional event that allows to infer an actively eroding topographic high that lasted from Early to Late Paleozoic times, as a consequence of the far-field stress transmitted from the active Gondwanian convergent margin.

How to cite: Olivetti, V., Cattò, S., Balsamo, F., Zurli, L., Perotti, M., Cornamusini, G., Fioraso, M., Rossetti, F., and Zattin, M.: Uplift and erosion of an intraforeland topographic high: implication for the evolution of the Gondwanian Transantarctic foreland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15516, https://doi.org/10.5194/egusphere-egu24-15516, 2024.

EGU24-15687 | Posters on site | GD1.1

The EVoLvE toolkit: a set of methods for systematic quantification of volcano morphometry and their temporal evolution 

Matthieu Kervyn, Roos M.J. van Wees, Pablo Grosse, Pierre Lahitte, and Daniel O'hara

Volcanoes display a wide range of morphologies, resulting from the cumulative imprints of deposition from multiple eruptive events and processes, deformation by intrusive and gravitational processes, as well as erosion throughout the active volcanic phase and beyond. Quantitative documentation of the morphometry of volcanoes offers opportunities to compare volcanic edifices across tectonic regions, define evolutionary trends for volcanoes of different ages and/or stage, or compare natural volcanoes with results from analogue or numerical modelling. Although such morphometric studies exist, the comparability of their results faces challenges related to the contrasted approaches used for delineating volcanic edifices, defining morphometric metrics to characterize volcano sizes, shapes, and erosion patterns, and deriving the pre-erosional volcano volume.

Building upon the MORVOLC (Grosse et al. 2012) and ShapeVolc (Lahitte et al. 2012) algorithms, the EVoLvE project has produced a suite of scripts in MatLab to semi-automatically document the morphometry of stratovolcanoes systematically. First, the manual delineation of a volcano’s base is aided by implementing a slope threshold (suggested to be at 3°) after applying a 300m low-pass filter on the volcano’s topography to identify the prominent volcano landform. Morphometric parameters documenting volcano-scale size, plan-shape, profile shape and slope, as well as metrics derived at regular elevation intervals, following the MORVOLC approach of Grosse et al. (2012), are complemented with a new set of parameters (DrainageVolc) that document the erosion pattern of volcanoes, specifically the drainage density and the geometry of drainage basins. Finally, assuming basins’ divides or local quasi planar surfaces represent the least eroded sections of an edifice, a surface fitting algorithm (ShapeVolc, Lahitte et al. 2012) is used to find the best approximate pre-erosional shape of the volcano,  making it possible to compute its erupted and eroded volumes, and dismantling and degradation rates.

In this contribution, we illustrate how the EVoLvE toolkit can be used to systematically document the morphometry of stratovolcanoes across volcanic arcs, and with contrasted ages to highlight morphological evolution through time. The toolkit can as well be used to compare the morphometry of natural volcanoes with those of synthetic volcanic cones whose erosion is simulated through analogue experiments and numerical landscape evolution models. The Matlab codes of the EVoLvE toolkit are open-source: they aim to contribute to homogenizing the morphometric datasets for volcanoes around the world as a first step towards a more comprehensive understanding of the morphological evolution of volcanoes.

 

References:

Grosse, P., van Wyk de Vries, B., Euillades, P. A., Kervyn, M. & Petrinovic, I. A. 2012: Systematic morphometric characterization of volcanic edifices using digital elevation models. Geomorphology 136, 114-131.

Lahitte, P., Samper, A. & Quidelleur, X. 2012: DEM-based reconstruction of southern Basse-Terre volcanoes (Guadeloupe archipelago, FWI): Contribution to the Lesser Antilles Arc construction rates and magma production. Geomorphology, 136, 148-164.

How to cite: Kervyn, M., van Wees, R. M. J., Grosse, P., Lahitte, P., and O'hara, D.: The EVoLvE toolkit: a set of methods for systematic quantification of volcano morphometry and their temporal evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15687, https://doi.org/10.5194/egusphere-egu24-15687, 2024.

EGU24-15825 | Posters on site | GD1.1

Dynamism of the Neogene and Quaternary erosional processes in the Lesser Antilles volcanoes, constrained by morphometric approaches 

Pierre Lahitte, Louise Bergerot, Pablo Grosse, Roos M. J. van Wees, Daniel O’Hara, and Matthieu Kervyn

Understanding the temporal variations in erosion dynamics is crucial when exploring the intricate relationship between climates and the evolution of landforms. Volcanic surfaces constitute an undeniable asset for documenting temporal variations in erosion dynamics, as they readily reveal the onset of erosion. Indeed, the dating of volcanic materials constrains the age of eruptive activity, volcanic surface formation, and the time since erosion occurred. This study quantifies the Neogene and Quaternary erosional processes that shaped the current Lesser Antilles's volcanic reliefs. We apply morphometric approaches on high-resolution digital topographies of very densely dated volcanoes to discern the influence of factors driving erosion, focusing on climatic context and erosion duration.

The detailed analysis of the erosion signature's evolution was carried out on the French volcanic oceanic arc islands of Basse-Terre (Guadeloupe) and Martinique, thanks to the large number of geochronological constraints (around 100 K-Ar datings on each of them) and the high-resolution topography (LIDAR DEM at horizontal 1m resolution). The meticulous examination of erosion signatures is facilitated because magmatic activity, which produced the same kind of volcanic edifices in both islands, has undergone a spatial migration (westward in Martinique, southward in Basse-Terre). It results in outcrops of terrains spanning vastly different ages (0-3 and 0-25 Ma, respectively), providing a unique opportunity to investigate the distinct influences of geological processes on erosion signature. The study focuses on quantitative analysis of river-long profiles by scaling river profile concavity, hypsometric indexes and knickpoints, which are noticeable slope breaks or abrupt changes in the gradient of the river channel. Thanks to the dense geochronological database, metrics computed for each geomorphological feature can be associated with the age of formation of the local volcanic surface. Then, as these ages are relevant to the cumulated erosion process occurring since the end of the volcanic activity, such metrics can be correlated to the time and evolution trends in morphometric parameters can be investigated.

The 25 Ma-long erosion history of Martinique Island reveals two distinct patterns. During the initial 5 million years of erosion, there is a rapid increase in river concavities and a decrease in the intensity and number of heterogeneities along river profiles, resulting in smoother stream patterns. In contrast, over the 5-25 Ma erosion period, every river's morphometric parameters evolve slowly, suggesting a preservation of river concavity. This transition phase in concavity evolution could mark the moment when the rivers’ incision, driven by regressive erosion and carving into the volcano from every side, having finally affected the summit area, also reached a maximum concavity. Erosive processes then reduced the volcano's elevation but maintained a relatively uniform profile shape and, consequently, concavity over time. Despite Basse-Terre Island's shorter erosion history of 3 million years, morphometric parameters testify that this island experienced strictly similar evolution as Martinique Island during the same erosion lifespan, suggesting a comparable evolution of the Basse-Terre reliefs in the future.

How to cite: Lahitte, P., Bergerot, L., Grosse, P., van Wees, R. M. J., O’Hara, D., and Kervyn, M.: Dynamism of the Neogene and Quaternary erosional processes in the Lesser Antilles volcanoes, constrained by morphometric approaches, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15825, https://doi.org/10.5194/egusphere-egu24-15825, 2024.

EGU24-16531 | ECS | Orals | GD1.1

Exploring the structure of the Cascadia Subduction Zone by coupling 3D thermomechanical modeling and CPO evolution with observations. 

Menno Fraters, Magali Billen, John Naliboff, Lydia Staisch, and Janet Watt

The Cascadia Subduction Zone is characterized by young subducting lithosphere, its isolation from other subducting systems, and its ability to produce megathrust earthquakes (M>9.0) and devastating tsunamis. Due to its high potential hazard and risk, it is also a well-studied subduction zone where modern, diverse and detailed observational datasets are available through the USGS and initiatives like GeoPrisms and EarthScope. These datasets include high quality GPS, onshore and offshore geophysical imaging, geochemical and seismic anisotropy data. Integrating these data sets with geodynamic modeling presents an opportunity to gain insight into outstanding questions regarding slab structure, tectonic evolution, seismic hazards, and the physical processes that can self-consistently explain all these observations. For example, geologic and geophysical data suggest that there may be one or two prominent slab gaps or tears, while tomographic data does not fully constrain the depth extent of the slab. Furthermore, the overriding plate is composed of different terranes and contains numerous active and slowly moving faults, complicating efforts to accurately constrain variations in present-day stress and deformation rates.

In this study we test whether comparison of observations to geodynamic model predictions can distinguish between different slab geometries for the Cascadia Subduction Zone. To this end, we have created regional 3D geodynamic models of Cascadia including the slab based on the Slab 2.0 dataset. The model setup is built with the Geodynamic World Builder, and the models are run with the geodynamics code ASPECT. We present results which compare the Juan de Fuca plate velocities against the present day Euler poles. We have found that matching the plate velocity magnitude and direction is sensitive to the rheological model overall, while at the same time being insensitive to certain aspects of the plate boundary rheologies. During the evolution of these models we track the development of the CPO (Crystal Preferred Orientation) with an implementation of the DREX algorithm, so we can compare it against observations of seismic anisotropy in the region. Our presentation will focus on the importance of the geometry of the slab and the strength of different sections of the interface. Furthermore, these models and demonstrate workflows for linking the model results to surface tectonics.

How to cite: Fraters, M., Billen, M., Naliboff, J., Staisch, L., and Watt, J.: Exploring the structure of the Cascadia Subduction Zone by coupling 3D thermomechanical modeling and CPO evolution with observations., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16531, https://doi.org/10.5194/egusphere-egu24-16531, 2024.

EGU24-17475 | ECS | Posters on site | GD1.1

Surface regimes can provide an inherent perspective into interior dynamics 

Oliver Henke-Seemann and Lena Noack

Tectonic processes shape the Earth's lithosphere and surface. Deformation, as a result of tectonic forcings, arises mainly in the regions of plate boundaries. A recurring process is the subduction of oceanic lithosphere, which is widely regarded as the main driver of plate tectonics and the recycling of surface material into the mantle. In geodynamic models, the breaking of the strong crust is facilitated by processes that mimic plastic deformation. Most efforts to include plate tectonics self-consistently into mantle convection models, combine Newtonian diffusion creep with a stress-dependent pseudo-plastic rheology, given in the form of a yield criterion. Studies from seismology and geodynamic modelling indicate that cold lithospheric crust can reach the lowermost mantle regions, even the core-mantle-boundary. Additionally, the agglomeration of continental lithosphere (the most extreme variants of which are called supercontinents) inhibits the escape of heat over large surface areas, resulting in an abnormally heated mantle beneath. Therefore, it can be argued, that surface processes exert control on mantle dynamics as a whole, by introducing thermal and compositional heterogeneities.

An example of the influence of surface tectonics on the interior can be found in the study of the Earth's geodynamo. Theoretical considerations and numerical models indicate, that the heat flux at the core-mantle boundary partly governs the variability of the geodynamo, and therefore the frequency of geomagnetic reversals and excursions. 

We run several numerical mantle convection simulations in a 2D-spherical annulus geometry, with a visco-plastic rheology to facilitate surface mobilisation. The models are evaluated with respect to well-known diagnostic values, used to recognise plate-like surface deformation, as well as the thermal structure of the lower mantle. In this, we aim to connect tectonic regimes or continental configurations that arise dynamically at the surface, to evolutionary trends in the mantles thermal structure.

How to cite: Henke-Seemann, O. and Noack, L.: Surface regimes can provide an inherent perspective into interior dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17475, https://doi.org/10.5194/egusphere-egu24-17475, 2024.

EGU24-18172 | Orals | GD1.1

On the different contributions to the peculiar topography of the Iberian Peninsula 

Ana M. Negredo, Javier Fullea, Olga Ortega-Gelabert, Carlos Clemente, and Julien Babault

The topography of the Iberian Meseta located between the Pyrenees-Cantabrian Mountains and the Betics Chain is moderately high (660 m on average) compared to the high plateaus on Earth (> 1 km) albeit higher than the topography of the surrounding western European plate. The Iberian Meseta encompasses Cenozoic sedimentary basins, active or inactive Alpine mountain ranges, and low-relief erosional surfaces represented by plateaus with elevations between 600 and 1400 m asl. It is commonly accepted that ~600-700 m surface uplift occurred during the Cenozoic, but the underlaying processes and the precise timing of the onset of the plateau growth are strongly debated. The main objective of the present study is to find out to what extent the topography of the Iberian Meseta has a crustal, lithospheric or a sublithospheric origin. We used the results of a recent modelling based on the joint inversion of both the crustal and lithospheric mantle structure. It encompasses an integrated geophysical-lithological multi-data modelling. The inversion is framed within an integrated geophysical-petrological setting where mantle seismic velocities and densities are computed as a function of temperature and composition whereas crustal density, shear and compressional wave velocities are lithologically linked based on empirical relationships from global petrophysical databases.

We computed the relative contribution to topography of crustal and lithospheric mantle thickness variations and density structure. The topography of the Alpine mountain belts in Iberia is largely associated with thickened crust. We find that the elevated topography in the NW Iberian Meseta (elevation > 700 m) is mostly related to the lithospheric mantle thinning. This is in agreement with Inversion of topographic data, landform dates, and erosion rates suggesting a late Cenozoic mantle-related surface uplift of several hundreds of meters in NW Iberia (EGU24-11613) and in the central Iberia (EGU24-16382). Similarly, a thin and warm lithospheric mantle is responsible for the positive elevation of the onshore Mediterranean margins. A negatively buoyant lithospheric mantle causes >1 km subsidence in the Gibraltar Arc and western Pyrenees.  We solved the Stokes flow to evaluate the contribution of temperature-related buoyancy forces at asthenospheric depths. These forces cause a long wavelength topographic response located in the centre of the Iberian Peninsula reaching a maximum value of only 100-150 m, which is much lower than the values reported in previous works assuming an isostatic balance.

How to cite: Negredo, A. M., Fullea, J., Ortega-Gelabert, O., Clemente, C., and Babault, J.: On the different contributions to the peculiar topography of the Iberian Peninsula, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18172, https://doi.org/10.5194/egusphere-egu24-18172, 2024.

EGU24-18291 | ECS | Posters on site | GD1.1

Lava tubes formation and extensive flow field development during the 1858 eruption of Mount Vesuvius.  

Thomas Lemaire, Daniele Morgavi, Paola Petrosino, Sonia Calvari, Leopoldo Repola, Lorenzo Esposito, Diego Di Martire, and Vincenzo Morra

Lava tubes are an important transport mechanism in active lava flows. Their presence in a lava flow can influence its distance of emplacement due to the insulation of the hot molten lava by a cooled overlying crust. Understanding mechanisms of formation and development of lava tubes is fundamental to comprehend lava flow propagation and improve knowledge to better manage the hazard during a volcanic crisis. Vesuvius is known for its major explosive eruptions; however, in its history it underwent extensive periods of open conduit, with prolonged explosive activity and lava flows. After the 1631 eruption, Vesuvius entered an effusive period that ended with the 1944 eruption. During these 313 years, over one hundred lava flows emplaced on Vesuvius flanks, particularly the 1858 eruption which produced a compound pahoehoe lava flow that emplaced on the western flank of Vesuvius. 

In this study, we conducted: (1) a temporal and spatial reconstruction of the 1858 lava flow using historical documents (geological maps, paintings, descriptions of eruptions), (2) a morphological and surficial analysis of the 1858 lava flow as well as the definition of new contours based on geological maps and digital elevation models and (3) a complete morphological analysis of the lava tube using high-end technologies (time-of-flight terrestrial laser scanner, Lidar equipped drone and optical cameras).  

On the 1858 lava flow field surface we found numerous tumuli and ephemeral vents. We discovered a small lava tube present in a flat area of the lava flow field (<3°) with ropy to slabby pahoehoe surface lavas. The lava tube is oriented north-south, perpendicular to the main flow direction. It is triangularly shaped with a length of 30.05 meters and a width that varies from 1.20 to 17.61 meters from the northern to the southern part. The average height is around 2 meters. The slope along the flow direction is on average 4.48°. We measured a mean roof thickness of 2.4 meters. The roof is fractured and has collapsed in different areas of the lava tube. Inside, we observed features that relate to the temporal evolution of the lava tube. Stalactites are present on the ceiling of the tube suggesting a prolonged flow of lava within the tube. Multiple layers of lava are covering the wall of the lava tube, the last wall lining is five to seven centimeters thick and, in some areas of the lava tube, has detached from the wall and rolled down on itself, testifying to a sudden drainage of the lava tube when the lining was still plastic.  

The results of the study of the 1858 lava flow field and of its lava tube are essential for expanding our knowledge about the processes at the basis of lava flow field emplacement and development on Vesuvius and the first attempt focused on understanding effusive dynamics governed by lava tube formation (i.e., lava emplacement) at Vesuvius.

How to cite: Lemaire, T., Morgavi, D., Petrosino, P., Calvari, S., Repola, L., Esposito, L., Di Martire, D., and Morra, V.: Lava tubes formation and extensive flow field development during the 1858 eruption of Mount Vesuvius. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18291, https://doi.org/10.5194/egusphere-egu24-18291, 2024.

Gondwana Basins of eastern India preserves sediment record from Carboniferous to Triassic, which were possibly sourced partially from Antarctica through a radial drainage system. This study attempts to test the hypothesis regarding source of sediments based on petrographical and mineral chemical analysis of siliciclastic Paleo-Mesozoic sediments of eastern India. We present an integrated provenance and paleodrainage analysis on the sediments of Bokaro and Raniganj basins, outcrops of which occur along E-W trend along eastern part of India. The sedimentation in these Gondwana basins initiates with basal Talchir Formation, consisting of alternation between conglomerate and fine- to medium-grained sandstones, and is succeeded by Barakar-Barren Measures-Raniganj and Panchet Formation with sandstone-mudstone alternation, with or without coal.  Petrographic study of sandstones reveals moderate sorting, with angular to sub-rounded quartz and feldspar and rounded to well-rounded lithic fragments; however, the abundance of lithic fragments drastically reduces from Talchir to Panchet formation. Feldspar grains shows the dominance of K-feldspar over plagioclase.  Most of the sandstones are classified as feldspatho-quartzose arenite. The Qm-F-Lt plot indicates that these sandstones were derived primarily from transitional continental sources. Heavy minerals in sandstones include garnets, tourmaline, epidote, rutile, zircon, monazite in order of decreasing abundance. Mineral chemistry of garnet in sandstones points their source to metasedimentary amphibolite facies rocks and granitoid. The tourmaline mineral chemistry suggests the derivation of sediments from various sources, including Li-poor granitoids associated with pegmatites, aplites and Ca-poor metapelites. Rutile chemistry in sandstones indicates the predominance of metapelitic source over metamafic source. Insights from heavy mineral analysis indicates that the Gondwana sediments were derived from multiple sources, and such variation in sources bears information about paleogeographic and paleotectonic evolution of the depositional basin.  The mineral composition of source rocks and paleocurrent data tracks the source of sediments to Eastern Granulite-Schist belt and the Eastern Ghat mobile belt, situated to the east and southwest parts of the Gondwana succession.  This study when integrated with geochronological data would reveal the extent to which a particular source provided sediments to these basins, evolution of sediment sources from bottom to top and ultimately will lead to a refined understanding of timing and evolution of East Gondwana assembly.

How to cite: Dutta, A. and Banerjee, S.: Facies Analysis, Petrography, heavy mineral analysis of paleo-Mesozoic sediments of Eastern India: Implications on provenance and basin evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18433, https://doi.org/10.5194/egusphere-egu24-18433, 2024.

EGU24-18733 | Orals | GD1.1

The uplift of East Africa-Arabia swell: the signature of the mantle upwelling and spreading 

Andrea Sembroni, Claudio Faccenna, Thorsten W. Becker, and Paola Molin

The East Africa - Arabia topographic swell is an anomalously high-elevation region of ~4000 km long (from southern Ethiopia to Jordan) and ~1500 km wide (from Egypt to Saudi Arabia) extent. The swell is dissected by the Main Ethiopian, Red Sea, and Gulf of Aden rifts, and characterized by widespread basaltic volcanic deposits emplaced from the Eocene to the present. Although most agree that mantle plumes play a role in generating the swell, several issues including the number and locations of plumes and the uplift signatures remain debated. We seek to address these questions and provide a general evolutionary model of the region. To this end, we conduct a quantitative analysis of topography to infer isostatic and dynamic contributions. When interpreted jointly with geological data including volcanic deposits, the constraints imply causation by a single process which shaped the past and present topography of the study area: the upwelling of the Afar superplume. Once hot mantle material reached the base of the lithosphere below the Horn of Africa during the Late Eocene, the plume flowed laterally toward the Levant area guided by pre-existing discontinuities in the Early Miocene. Plume material reached the Anatolian Plateau in the Late Miocene after slab break-off and the consequent formation of a slab window. During plume material advance, buoyancy forces led to the formation of the topographic swell and tilting of the Arabia Peninsula. The persistence of mantle support beneath the study area for tens of million years also affected the formation and evolution of the Nile and Euphrates-Tigris fluvial networks. Subsequently, surface processes, tectonics, and volcanism partly modified the initial topography and shaped the present-day landscape.

How to cite: Sembroni, A., Faccenna, C., Becker, T. W., and Molin, P.: The uplift of East Africa-Arabia swell: the signature of the mantle upwelling and spreading, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18733, https://doi.org/10.5194/egusphere-egu24-18733, 2024.

EGU24-20357 | ECS | Posters on site | GD1.1

A newly discovered youngermost (13.07 Ma) “Upper Tuff”, a large-volume phreatomagmatic ignimbrite in the Pannonian Basin, drapes the present, faulted/dissected topography  

Tamás Biró, Pierre Lahitte, Maxim Portnyagin, Emő Márton, Emőke Mohr, Márton Palotai, Sándor Józsa, Levente Iván, Márton Krasznai, Mátyás Hencz, Jean-Louis Paquette, János Hír, Fanni Vörös, and Dávid Karátson

Silicic ignimbrite volcanism played a major role in the Miocene evolution of the Central Paratethys. The most voluminuous ignimbrites identified to date (18.1–14.4 Ma) were emplaced in various paleoenvironments in the North Pannonian Basin, thus they are extremely helpful in regional stratigraphy. Here, we present the discovery of a previously unknown but widespread, youngest member of the “Upper Rhyolite Tuff“, referred to as Dobi Ignimbrite, which shows a distinctive glass geochemistry. High-precision sanidine and plagioclase Ar-Ar dating yielded 13.066±0.019 Ma (earliest Sarmatian stage in Paratethys chronology), significantly shifting the previously claimed termination (i.e. Badenian) of the North Pannonian ignimbrite flare-up. In addition, we demonstrate that, although the Dobi Ignimbrite is underlain by a marine sedimentary succession, it was emplaced on land, as it bears leaves and tree trunk fragments and is rich in charcoal. Despite the highly faulted terrain as well as intense dissection and erosion controlled by the neotectonic evolution of the Pannonian Basin, the observed areal extent (c. 1000 km2) and calculated minimum volume (c. 50 km3) of the ignimbrite may represent a VEI= 6 or 7 eruption, which needs to be further delineated. At the same time, the ignimbrite has a strongly phreatomagmatic character, suggesting an abundant, possibly shallow sea- or residual lake water source that was likely limited to the vent area (e.g. caldera graben). The detected sharp environmental change from submarine to terrestrial, as defined by the timing of ignimbrite emplacement at c. 13 Ma, marks the latest Badenian regressive period, followed by a Sarmatian erosion during the Central Paratethethys evolution.

 

How to cite: Biró, T., Lahitte, P., Portnyagin, M., Márton, E., Mohr, E., Palotai, M., Józsa, S., Iván, L., Krasznai, M., Hencz, M., Paquette, J.-L., Hír, J., Vörös, F., and Karátson, D.: A newly discovered youngermost (13.07 Ma) “Upper Tuff”, a large-volume phreatomagmatic ignimbrite in the Pannonian Basin, drapes the present, faulted/dissected topography , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20357, https://doi.org/10.5194/egusphere-egu24-20357, 2024.

Four monogenetic volcanoes were formed during the last 100 ka (Late Pleistocene), west of the city of Morelia (Mexico), in the central-eastern part of the Michoacán-Guanajuato Volcanic Field, located in the central region of the Trans-Mexican Volcanic Belt. These include four scoria cones (Melón, Mina, Tzinzimacato Grande, and Tzinzimacato Chico) and some lava flow deposits associated with the material emitted during the effusive phase of the volcanoes. From the study of stratigraphic relationships in the field and geological mapping, the eruptive chronology of the monogenetic volcanoes was determined. Subsequently, based on the analysis of the morphological (flow dimensions) and petrographic characteristics, the eruptive parameters (effusion rate and emplacement time) and the rheology of the lavas were estimated. The flow units of the effusive phase of the volcanoes present different morphological and mineralogical characteristics. The flows with greater slopes have average viscosities of 2.7x108 P and a higher volume content of phenocrysts; the value of this property decreases in the flows with lower slopes, 1.7x108 P as respectively. The results indicate that the most voluminous eruption corresponds to that emitted by the Mina volcano, with an effusion rate of 2.3 m3/s and a total duration of 239 days. The Tzinzimacato Chico volcano emitted a smaller volume of lava during its eruption, with an effusion rate of 0.9 m3/s and a total duration of 117 days, which is considered the most recent.

How to cite: Delgado Granados, H. and Hernández Villamizar, D.: Eruptive parameters of volcanoes Melón, Mina, Tzinzimacato Grande, Tzinzimacato Chico (Mexico) from morphology and petrographic studies , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20487, https://doi.org/10.5194/egusphere-egu24-20487, 2024.

EGU24-21095 | Posters on site | GD1.1

Evolution and Growth of Lava Deltas: Insights from the 2021 La Palma Eruption (Canary Islands) 

Lucía Sáez-Gabarrón, David Sanz-Mangas, Inés Galindo-Jiménez, Juana Vegas, Juan Carlos García-Davalillo, Mario Hernández, Raúl Pérez-López, Carlos Camuñas, Gonzalo Lozano, Carlos Lorenzo Carnicero, Miguel Ángel Rodríguez-Pascua, Maria Ángeles Perucha, Julio López Gutiérrez, and Nieves Sánchez

During the 2021 eruption on La Palma Island, the predominant volcanic hazard was lava flows, while tephra fall and gas emission were significant concerns. Consequently, monitoring the expansion of the lava flow perimeter considering the variations in volcanic activity became fundamental. The interaction of lava with the sea water was also a major concern for emergency managers due to its associated hazards like gas emission and explosive activity due to interaction lava-water, leading to a specific focus on the formation and development of lava deltas.

Almost 10 days after the beginning of the eruption, the lava reached the sea, forming a main structure (south delta) that grew in different phases until nearly the end of the eruption, covering an area of approximately 83 ha. The south delta encroached upon the sea and additionally buried the northern part of a pre-existing lava delta from the 1949 San Juan eruption. About 1300 m from the northernmost tip of the south delta, a new lava flow entry to the sea occurred 64 days into the eruption, feeding a second lava delta (north delta) of about 5 ha over a 4-day period.

This study has made significant technical and scientific contributions, not only during the emergency but also in preparation for future recovery efforts on La Palma. Remotely Pilot Aircrafts (RPAs) provided valuable information about the lava-flow development and enhanced a deeper understanding of the formation and evolution of lava deltas and their potential hazards. Moreover, the study highlights the potential impact on new inhabited or economically exploited areas and is imperative its preservation for the geological heritage, including marine zones. Furthermore, it will play a crucial role in forecasting the behaviour of lava deltas and in the development of mitigation measures for potential future eruptions.

How to cite: Sáez-Gabarrón, L., Sanz-Mangas, D., Galindo-Jiménez, I., Vegas, J., García-Davalillo, J. C., Hernández, M., Pérez-López, R., Camuñas, C., Lozano, G., Lorenzo Carnicero, C., Rodríguez-Pascua, M. Á., Perucha, M. Á., López Gutiérrez, J., and Sánchez, N.: Evolution and Growth of Lava Deltas: Insights from the 2021 La Palma Eruption (Canary Islands), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21095, https://doi.org/10.5194/egusphere-egu24-21095, 2024.

EGU24-21597 | ECS | Orals | GD1.1 | Highlight

The Chon Aike magmatic province: an active margin origin?

Joaquin Bastias-Silva, Richard Spikings, Teal Riley, and Jorge Sanhueza

EGU24-21895 | Orals | GD1.1 | Highlight

Closed loop experiments in global geodynamic earth models 

Hans-Peter Bunge, Ingo L. Stotz, Nicolas Hayek, berta vilacis, hamish brown, roman freissler, bernhard schuberth, sara carena, and anke friedrich

Recent advances in computational capabilities make it possible to compute global geodynamic earth models at near earthlike convective vigor. This paves the way to systematically obtain a range of synthetic data from such models in an approach that is known as closed loop experiments. Here we present results from closed loop experiments in geodynamic earth models targeted at three classes of data that are sensitive to the mantle convection process, namely seismic data, global stress patterns as reflected by the world stress map, and continent scale stratigraphy processed for the distribution of conformable and unconformable successions in recently developed so called hiatus maps. Our results reveal effects from spatially variable data collection and quality (as expected), mantle flow geometries (less expected) and (still poorly known) histories of paleo mantle flow. We conclude that the derivation of process based synthetic data from geodynamic earth models provides crucial information for data interpretion, that closed loop experiments are
a powerful tool to link geodynamic earth models to data, and that closed loop experiments could be helpful to guide future data collection efforts.

How to cite: Bunge, H.-P., Stotz, I. L., Hayek, N., vilacis, B., brown, H., freissler, R., schuberth, B., carena, S., and friedrich, A.: Closed loop experiments in global geodynamic earth models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21895, https://doi.org/10.5194/egusphere-egu24-21895, 2024.

EGU24-22053 | ECS | Posters on site | GD1.1

Revisiting tectonic models for the evolution of the Ellsworth Mountains in Antarctica: A key component for understanding the African-Antarctic section of the paleo-Pacific margin

Paula Castillo, Fernando Poblete, Rodrigo Fernández, Joaquín Bastias-Silva, C. Mark Fanning, Teal Riley, Jaime Cataldo Bacho, Ellen Rosemann, Cristóbal Ramírez de Arellano, and Katja Deckart

EGU24-103 | ECS | PICO | GD2.1

 Oxygen-fugacity evolution of magmatic Ni-Cu sulfide deposits in East Kunlun: Insights from Cr-spinel composition  

Lihui Jia, Yi Chen, Bin Su, Qian Mao, and Di Zhang

Redox state of parental magma would have undergone significant changes from partial melting in the mantle to emplacement in the shallow crust, which might play a critical role in the genesis of magmatic Ni-Cu sulfide deposits in convergent tectonic settings. In this study, we present mineralogy, petrology, and fO2 calculations of the Xiarihamu Ni-Cu deposit and the Shitoukengde non-mineralized intrusion in the East Kunlun orogenic belt. Olivine-spinel pairs in different magmatic stages were chosen to estimate the magma fO2 (olivine-spinel oxybarometer), track the changes in oxygen fugacity during magmatic evolution, and reveal its influence on the metallogenic mechanism of the Ni-Cu sulfide deposit. Spinel Fe3+/ΣFe ratios determined by a secondary standard calibration method using electron microprobe. Those ratios of the Xiarihamu Ni-Cu deposit vary from 0.32±0.09 to 0.12±0.01, corresponding to magma fO2 values ranging from ΔQFM+2.2±1.0 to ΔQFM-0.6±0.2. By contrast, those of the Shitoukengde mafic-ultramafic intrusion increase from 0.07±0.02 to 0.23±0.04, corresponding to magma fO2 varying from ΔQFM-1.3±0.3 to ΔQFM+1.0±0.5. A positive correlation between fO2 and Cr-spinel Fe3+/ΣFe ratios suggests that the Cr-spinel Fe3+/ΣFe ratios can be used as an indicator for magma fO2. The high fO2 (QFM+2.2) of the harzburgite in the Xiarihamu Ni-Cu deposit suggests that the most primitive magma was characterized by relatively oxidized conditions, and then became reduced during magmatic evolution, causing S saturation and sulfide segregation to form the Xiarihamu Ni-Cu deposit. The evolution trend of the magma fO2 can be reasonably explained by metasomatism in mantle source by subduction-related fluid and addition of external reduced sulfur from country gneisses (1.08–1.14 wt.% S) during crustal processes. Conversely, the primitive magma of the Shitoukengde intrusion was reduced and gradually became oxidized (from QFM-1.3 to QFM+1.0) during crystallization. Fractional crystallization of large amounts of Cr-spinel can reasonably explain the increasing magma fO2 during magmatic evolution, which would hamper sulfide precipitation in the Shitoukengde intrusion. We propose that the temporal evolution of oxygen fugacity of the mantle-derived magma can be used as one of the indicators for evaluating metallogenic potential of Ni-Cu sulfide deposits, and reduction processes from mantle source to shallow crust play an important role in the genesis of magmatic Ni-Cu sulfide deposits.

How to cite: Jia, L., Chen, Y., Su, B., Mao, Q., and Zhang, D.:  Oxygen-fugacity evolution of magmatic Ni-Cu sulfide deposits in East Kunlun: Insights from Cr-spinel composition , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-103, https://doi.org/10.5194/egusphere-egu24-103, 2024.

EGU24-616 | ECS | PICO | GD2.1 | Highlight

The Namuaiv picrite-melanephelinite pipe, Kola alkaline province, Russia: petrography and evolution of late alkaline melts during forming large alkaline province with carbonatites. 

Darina Shaikhutdinova, Alexey Kargin, Liudmilla Sazonova, Natalia Lebedeva, Anna Nosova, and Yapaskurt Vasiliy

Petrological investigations of large alkaline provinces with carbonatites are very important to understanding the generation and evolution of alkaline melts, as well as processes provided generation of related ore deposits. Most often, generation of large alkaline massifs with carbonatites accompanied by intrusion of related ultramafic alkaline and related alkaline-ultramafic melts as dykes swarms and explosive pipes. These melts could be generated on the initial stages of magmatic activities of alkaline province magmatism, or fix the final stages of alkaline magmatism, after the formation of large alkaline massifs with carbonatites. Studying of these melts could provide insights into the composition of primary melts for large alkaline province, as well as understanding their evolution during magmatic activities. Moreover, the latest melts forming dykes and explosive pipes could provide information about the evolution of the mantle source of these rocks including of processes of lithospheric mantle transformations (enrichment, depleting, mantle metasomatism etc.).

The Kola alkaline province (KAP) with carbonatites is a good natural laboratory for investigation petrology of alkaline melts and their evolutions. KAP includes large alkaline massifs with carbonatites, the early dyke swarms of ultramafic and alkaline lamprophyres and late explosive pipes of the alkaline rocks (Arzamastsev et al., 2005). To investigate the composition of alkaline melts at the late stages of the province's magmatic activity, we have studied the petrography and mineralogy (olivine composition) of the Namuaiv pipe rocks.

The Namuaiv pipe (363 ± 3 Ma; Arzamastsev et al., 2005) erupted the alkaline rocks of the north part Khibiny massif (377± 3 Ma). The detailed petrographical studied suggested, that the pipe breccia was formed during mixing of two portions of alkaline melts close in composition to alkaline picrite and melanephelinite.

The Namuaiv rocks contain several types of olivine grains: (1) picritic melt phenocrysts; (2) antecrysts of ultramafic lamprophyres of the Kandalaksha Bay (Vozniak et al., 2023) that traced the first stages of the province magmatism; and (3) disintegrated fragments of the lithospheric mantle peridotites (mantle xenocrysts). The composition of olivine phenocrysts suggests that in the final stage of KAP activity, the alkaline melts have not fractionated in deep magmatic chambers and their composition is close to primary melts. That is in contrast to the first stages of KAP magmatism, where lamprophyre dikes were formed as fractionated melts (Vozniak et al., 2023). The present of the olivine antecrysts assumes that the Namuaiv melts ascent trough magmatic channels modified by previous portions of alkaline melts, that consistent with the presence metasomatic clinopyroxene-phlogopite xenoliths within the pipe.

The study was supported by the Russian Science Foundation under Grant No 23-77-01052.

Arzamastsev A.A., Belyatsky B.V., Travin A.V. et al. 2005. Dyke rocks in the Khibiny massif: relation to plutonic series, age, and characterization of mantle sources // Petrology. V.42. N3. P.1-23.

Vozniak A.A., Kopylova M.G., Peresetskaya E.V. et al. 2023. Olivine in lamprophyres of the Kola Alkaline Province and the magmatic evolution of olivine in carbonate melts // Lithos 448–449, 107149. doi:10.1016/j.lithos.2023.107149

How to cite: Shaikhutdinova, D., Kargin, A., Sazonova, L., Lebedeva, N., Nosova, A., and Vasiliy, Y.: The Namuaiv picrite-melanephelinite pipe, Kola alkaline province, Russia: petrography and evolution of late alkaline melts during forming large alkaline province with carbonatites., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-616, https://doi.org/10.5194/egusphere-egu24-616, 2024.

EGU24-1231 | PICO | GD2.1

Thermal state and nature of the low crust in the Baikal Rift zone according to the lower crust xenoliths of Cenozoic volcanics and Paleozoic magmas.  

Igor Ashchepkov, Andrey Tsygankov, Galina Burmakina, Sergei Rasskazov, Yusef Ailow, and Nikolai Karmanov

The lower crust and Moho pyroxenites and xenocrysts from Cenozoic volcanoes studied with the EPMA, SEM and LA ICP MS for trace elements evidence about the structure and composition of the transitional zone from the crust to mantle in Cenozoic volcanic regions In Vitim (picrite basalts), Dzhida, (Bartoy volcanoes) and Tunka valley (Karierny volcano). For the comparisons the lower crust xenocrysts from the Angara Vitim batholite were studied. The calculated PT conditions show the PT estimates are localizing within the Moho –and just beneath giving the vast range of temperatures. Lower they trace 90 mw/m2 geotherm. Within the crust the variation of temperature regime are varying from the conductive to advective. Xenocrysts and pyroxenite xenoliths mainly trace 90 mw/m2  SEA plume geotherm the area of the intrusions is over heated to 1350oC.

Fig.1 PT diagram for the xenoliths from Vitim Miocene  Picrite basalts

Fig.2 PT diagram for the xenoliths from Bartoy Pleistocene basalts

Fig.3 PT diagram for the xenoliths from Tunka Pliocene basalts

Fig.4 PT diagram for the xenocrysts from  Magmas of Angara-Vitim batholite

The granulites are typically represent the more colder conditions than SEA geotherm.  Xenocrysts from Angara Vitim batholith magmas reveal more depleted material of lower crust than those found in Cenozoic lavas and possibly are skialites. The xenocrysts and granulate xenoliths in Cenozoic lavas are mainly basic cumulates. The lower crust became more acid to the upper part. The lateral variations in the lower crust sampled material show enrichment in K2O at the boundary with the Siberian craton in Tunka, more metasomatic and hydrous nature in Dzhida zone and more basic and CaO rich characteristic in Vitim area.  These data give the evidence for the conditions of the creation of magmas of Angara-Vitim Batholiths.  It was created by the hot spot created kimberlites and basalts in north and Center of Yakutia in Silurian- Devonian time and Ingashi lamproites,  than it turned in Transbaikalia and after returned to central and Northern Siberia.   

 Supported by Ministry of Science and Higher Education of the Russian Federation. Supported by Russian Science Foundation (23-17-00030). Work is done on state assignment of IGM SB RAS, Geological institute SB RAS Ulan Ude and Institute of Earth crust SB RAS, Irkutsk

How to cite: Ashchepkov, I., Tsygankov, A., Burmakina, G., Rasskazov, S., Ailow, Y., and Karmanov, N.: Thermal state and nature of the low crust in the Baikal Rift zone according to the lower crust xenoliths of Cenozoic volcanics and Paleozoic magmas. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1231, https://doi.org/10.5194/egusphere-egu24-1231, 2024.

Finding of the giant diamond in Ebelyakh of CLIPPIR type of IIa type (Moor, 2014) suggest that similar diamonds should be found in the source kimberlites in Anabar basing and nearest Northern fields located within collision Khapchan terrain. To predict the finding authors are using the method of 5E diagrams based on the principle of analogy of the compositions Fe/(Fe+Mg) – Cr/(Cr+Al) – (Mn,Na) (Mitchell, 1986) for satellite minerals (Gar, Cpx, Chr and Ilmenites) of diamond (DSM) comparing with the etalon diagram for Karowe pipe (reference) and any other pipe. The forecast is quantified by the probability of convergence of these compositions using the division to the cluster groups. It was shown that the convergence of the DSM compositions of the Karowe and Grib pipes is 74%, which can be regarded as an indicator of the possible presence of diamonds in the predicted CLIPPIR pipe (Zinchenko et al., 2021).

 The application of this technique to two weakly diamondiferous kimberlite pipes of the Anabar region is demonstrated that the Leningrad pipe (Lower Devonian) have probability (75%) and Malokuonamskaya (Lower Triassic) (20%). Methods of constructing 5E diagrams and complementary PTXfO2 diagrams by I.V. Ashchepkov (2010-2023) of reconstructed lithospheric mantle sections (SCLM) to predict the crystallization of CLIPPIR diamonds. The petrological meaning of such characteristic suggest diamond formation in pipe in permeable mantle within protokimberlite magmatic chamber located near the lithosphere boundary and  connected with the asthenospheric source supplying by low oxidized magma, sulfides and extra pressure. The pipe should be surrounded by the low oxidized mantle eclogites rich C and dunites with the high pressure-temperature and Mg-rich ilmenite-chromite metasomatites.

 

A.

 

B.

Fig.1.  Mitchels’s diagram for minerals from Leningrad  and Malokuhamskay (B) pipes in comporisond with the Karowe pipe (contur lines) Cr- pyropes, Cr-diopsides, Ilmenites, Cr -spinels together. B. Triangle Na-Mn-Ti and C. Triangle Na-Al-Cr for Cr-diopsides and pyropes. D. distributions of the cluster groups for different minerals. E. Correltions of diamond grade with TiO2 in garnest, Cr-diopsides and Cr-spinels and Fe2O3 in ilmenites

The application of this technique to two weakly diamondiferous kimberlite pipes of the Anabar region is demonstrated that the Leningrad pipe (Lower Devonian) have probability (75%) and Malokuonamskaya (Lower Triassic) (20%). Methods of constructing 5E diagrams and complementary PTXfO2 diagrams by I.V. Ashchepkov (2010-2023) of reconstructed lithospheric mantle sections (SCLM) to predict the crystallization of CLIPPIR diamonds. The petrological meaning of such characteristic suggest diamond formation in pipe in permeable mantle within protokimberlite magmatic chamber located near the lithosphere boundary and  connected with the asthenospheric source supplying by low oxidized magma, sulfides and extra pressure. The pipe should be surrounded by the low oxidized mantle eclogites rich C and dunites with the high pressure-temperature and Mg-rich ilmenite-chromite metasomatites.

A.

B.

 

C.

Fig.2. PTXFO2 diagram for all xenocrysts from Leningrad (A), Malokuonamskaya (B) and Karowe AK-6 pipes. Symboles see legend

Russian Science Foundation grant 23-17-00030

How to cite: Ivanov, A., Zinchenko, V., Ashchepkov, I., Babushkina, S., Oleinikov, O., and Shelkov, P.: The perspectives of finding of giant CLIPPIR-type diamonds in weakly diamondiferous kimberlites of the north of Yakutia (Western Anabar region) using method of 5E Mitchells’s diagrams and cluster analyses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3574, https://doi.org/10.5194/egusphere-egu24-3574, 2024.

EGU24-3630 | PICO | GD2.1

The influence of the Siberian plume to the formation of Angaro-Vitim batholiths 

Andrey Tsygankov, Igor Ashchepkov, and Burmakina Galina

The influence of the hot spot for the AVB was assumed by (Kuzmin and Yarmolyuk, 2011). It may be the same hot spot that cause the creation of the kimberlites at 420 Ma at the north of Siberian craton (Sun et al,, 2014; 2018) than in the central part of Yakutian kimberlite province 350- 370 Ma. and transferred to the Prisayanie forming kimberlite fields covered by Carboni ferrous Permian sedimentary sequences in the basins of Tumanshet, Biryusa and Chuna rivers. Than it produced the Ingashi kimberlites - lamproites 310 -300 Ma (Kostrovitsly et al., 2022).

Granites of Angara-Vitim batholith were caused and influenced by this huge thermal event. The A-type granitoid magmatism and acid and mafic magmatism accompanied by mingling between these magmas suggest influence of the mantle plume (Litvinovsky et al., 2002; Tsygankov et al., 2019). This explains the K-nature of the granitoid magmatism, corresponding to the selective melting of the K-feldspars (Litvinovsky et al., 2000). This is the reason of the alkaline magmatism widely distributed among the  AVB magmas (Tsygankov et al., 2010-2021).

The huge amount of the volatiles that accompany plumes are responsible for melting in the mantle and crust (White and McKenzie, 1995). But essential parts of plume volatiles are CO2 and CH gases (Marty and Tolstikhin, 1998).. The H2O fluxes correspond to the starting and final stages of plume impulses (Ivanov et al., 2013). The periods of such pulses are nearly close to 30- Ma what is regulated by the Cosmic forces (Abbott, and Isley, 2002). Boundaries of the geological periods correspond to plume events In Transbaikalia, the H2O-rich flux was designated by transition to more acid magmas at 270 Ma. The CO2-rich flux at the maximum was manifested by the generation of the Burpala alkali-carbonatite massif (Vladykin et al., 2017).

Further, numerous already granitic and associated magmas and massifs were found in Eastern Sayan and Southern Pribaikalie. In Svyatoi Nos in Baikal 310 Ma (Kruk et al., 2023). 

The simultaneously and later the hot spot  created the main massifs of the AVB at the time span 275 -320 Ma (Khubanov et al., 2016; 2021).  The further continuation could be found in Khangai  batholith (270-240 Ma) (Yarmolyuk et al., 2013).

Than at the eastern margin, the plume turned to the NNW again and created the Siberian large igneous province- Permo-Triassic traps (Kuzmin and Yarmolyuk, 2011) 260-240 Ma.  the development of the plume magmatism in Early Triassic and later  in Jurassic time probably was transformed to the Island hot spot (Kuzmin and Yarmolyuk, 2010).

RNF grant 23-17-00030

Kostrovitsky  S.I. ea  2021.  Special Publications 513, 45 - 70.

Khubanov V.B ea 2021.   Russian Geology  Geophysics. 62, 1331-1349.

Kuzmin, M.I. , Yarmolyuk,   2014.   Russian Geology and Geophysics, 55, 120-143.

Kuzmin M.I. ea 2010.   Earth-Science Reviews, 102, 29-59.

Yarmolyuk V.V ea 2013,   Petrologiya , 21/2, 115–142.

How to cite: Tsygankov, A., Ashchepkov, I., and Galina, B.: The influence of the Siberian plume to the formation of Angaro-Vitim batholiths, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3630, https://doi.org/10.5194/egusphere-egu24-3630, 2024.

EGU24-4048 | PICO | GD2.1

Analyze of the structural conditions of heat and mass transfer under volcanoes of the northwestern sector of the Pacific ocean- Eurasian continent transition 

Viktor Sharapov, Yury Perepechko, Anna Mikheeva, Alexander Vasilevsky, Konstantin Sorokin, Igor Ashchepkov, and Grigory Kuznetsov

Based on the analysis of the tectonophysical characteristics of the actual seismofocal zone (SFZ) in the lithosphere of the Kuril-Kamchatka region and adjacent Oceanic areas,  we estimated the boundary conditions necessary for constructing the quantitative models of heat and mass transfer dynamics in compacted heterophase media under active volcanoes located over the mantle and crustal magmatic   sources of the ocean–continent transition regions of the northwestern sector of the Pacific Ocean.

The methodology of obtaining the information  used for developing of the mathematical models of magmatogenic processes includes: 1) the study of individual porphyry deposits associated with active fluid volcanogenic systems; 2) the study of morphological structures using cosmic satellite images (Sharapov et al., 1980); 3) the study of mantle and crust xenoliths of volcanics (Kutyev, Sharapov, 1979; Sharapov et al., 2009, 2017, 2020); 4) parametric tectono-physical analysis of the modern SFZ of the studied region (Sharapov et al., 1984, 1992); 5) experimental modeling of the  processes of deformation   Earth's crust and lithospheric mantle rocks of modern SFZ (Sharapov et al., 1984, 1992); 6) construction of mathematical models of the petrogenesis under volcanoes (Sharapov et al., 2007, 2020)

According to data on the structure of the Earth's crust under the Avacha volcano; (Koulakov et al., 2014), permeable zones are linear fractures 2-4 km wide, which are conductors of melts and magmatogenic fluids coming from magmatic systems (Koloskov et al., 2014).

An analysis of the time characteristics of formation porphyric deposits in the active margins of the Pacific Ocean (Sharapov et al., 2013) showed that more than 70% of the described deposits are formed during the evolution of fluid mantle-crustal ore-magmatic systems. This study analyzes the data on the structure of the modern SFZ of Kamchatka and the Kuril Island arc, used in constructing a model of heat and mass transfer under volcanoes.

Based on the analysis of the tectonophysical characteristics of the actual seismofocal zone (SFZ) in the lithosphere of the Kuril-Kamchatka region and adjacent Oceanic areas,  we estimated the boundary conditions necessary for constructing the quantitative models of heat and mass transfer dynamics in compacted heterophase media under active volcanoes located over the mantle and crustal magmatic   sources of the ocean–continent transition regions of the northwestern sector of the Pacific Ocean.

T

An analysis of the time characteristics of formation porphyric deposits in the active margins of the Pacific Ocean (Sharapov et al., 2013) showed that more than 70% of the described deposits are formed during the evolution of fluid mantle-crustal ore-magmatic systems. This study analyzes the data on the structure of the modern SFZ of Kamchatka and the Kuril Island arc, used in constructing a model of heat and mass transfer under volcanoes.

RNF grant  24-27-00411

How to cite: Sharapov, V., Perepechko, Y., Mikheeva, A., Vasilevsky, A., Sorokin, K., Ashchepkov, I., and Kuznetsov, G.: Analyze of the structural conditions of heat and mass transfer under volcanoes of the northwestern sector of the Pacific ocean- Eurasian continent transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4048, https://doi.org/10.5194/egusphere-egu24-4048, 2024.

Small-volume alkaline magmatism has now garnered due attention in geosciences, wherein these rocks provide essential information about deep mantle processes, geochemical composition, and the prevailing geodynamics. The continental alkaline magmatism of deep-seated ultramafic lamprophyres (UML) is spatially and temporally linked with continental breakup and rifting. Additionally, they have gained significant attention in terms of mineralization.

Deccan hosts one of the most extensive and peculiar suites of lamprophyre complexes in India, and this magmatism holds valuable geological information to unveil the geodynamic processes and provide significant implications on the enrichment/depletion processes of SCLM during Deccan times. The present research delves into the mineral and whole-rock geochemical compositions and paleomag dating of lamprophyres from the West Coast Alkaline Complex (WCAC) of the Deccan Large Igneous Province. The study has implications for the relation of lamprophyre magmatism with the Réunion mantle plume, the associated main phase of Deccan tholeiite magmatism, the initiation of rifting in the western Indian subcontinental margin, the separation of Seychelles from the Indian subcontinent, as well as the role of lithosphere thinning in triggering lamprophyre magmatism. WCAC lamprophyres are principally composed of olivine and phlogopite phenocrysts/ macrocryst embedded in a mesostasis of carbonate, clinopyroxene, olivine, nepheline, spinel, and melilite groundmass. The presence of titanian aluminous phlogopite, clinopyroxene, and Al-enriched spinels with high Fe2+/(Fe+Mg) ratios are the characteristic features of WCAC lamprophyres. They are primitive, undersaturated in silica (SiO2: 38.43 – 38.99), and rich in MgO (up to 10 wt. %), TiO2 (up to 4.2 wt. %), and light rare earth elements. Mineral genetic classification schemes and geochemical compositions demonstrate a resemblance with ultramafic lamprophyres. 

High LREE/HREE (La/Yb= 75-82) ratios, similar to UMLs reported globally, and low Ba/Rb and Rb/Sr ratios exhibit the predominance of phlogopite and amphibole in the mantle source. Geochemical investigations inarguably trace their genesis back to the enriched garnet lherzolite mantle, metasomatised by silicate and carbonate veins. They show compositional similarity with global damtjernites and derivation from moderate pressure depth (3-4 GPa) corresponding to 90-100 km thick lithospheric mantle. Paleomagnetic studies support the intrusion of lamprophyres, predominantly during the chron C29n, thereby substantiating their radiometric eruption age at ~65 Ma. Seismic tomography models reveal a current lithospheric thickness of approximately 50 km beneath the WCAC, suggesting delamination of the lithosphere after the intrusion of lamprophyres at 65 Ma. UML magmatism in WCAC resulted from the initiation of a rift, which ultimately led to the separation of the Indian subcontinent and the Seychelles. The impetus behind the emplacement of UML dykes is intricately tied to passive rifting and external plate boundary forces, surpassing the influence of the Reunion mantle plume. The lithospheric thinning presumably occurred after the emplacement of lamprophyres and other alkaline rocks and continued with continental rifting in response to greater plate-tectonic stresses in the region of persistent lithospheric weakness.

How to cite: Singh, A. and Dongre, A.: Post-tholeiite rifting and genesis of ultramafic lamprophyres at ~65 Ma in the Deccan Large Igneous Province, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4288, https://doi.org/10.5194/egusphere-egu24-4288, 2024.

EGU24-4498 | PICO | GD2.1

Role of sediment-derived melts in Mo cycling of subduction zone 

Feng Huang, Jie Li, Jifeng Xu, and Yunchuan Zeng

While heavy molybdenum (Mo) isotope compositions in arc-related rocks have been linked to slab-derived fluids, the origins of arc lavas with light isotopic Mo compositions remain enigmatic. The two potential sources for the origin of light Mo isotopes in arc rocks are (1) dehydrated oceanic crust 1, 2 and (2) subducting sediments 3, 4. Although the former has been extensively recognized, the latter still poses an enigma. We present the Mo-Sr-Nd-Hf isotope compositions and elemental data of a suite of Jiang Tso andesites to elucidate the chemical compositions of sediment-derived melts in the central Tibetan Plateau. The andesites from the Jiang Tso area show elevated Mg# values, along with trace element characteristics reminiscent of melts derived from sediments. Their Sr-Nd-Hf isotope compositions (87Sr/86Sri = 0.710260–0.710671, εNd(t) = –10.63 to –8.97, and εHf(t) = –9.38 to –8.02) closely resemble those of contemporaneous sediments in the central Tibetan Plateau. In addition, these andesites exhibit higher Ce/Mo ratios (396–587) and extremely lighter δ98/95Mo values (−1.62‰ to −0.69‰) compared to the depleted mantle (δ98/95Mo = –0.21‰ ± 0.02‰) 5, 6 and the majority of arc lavas (δ98/95Mo = –0.07‰ ± 0.04‰) 3, suggesting a more plausible explanation lies in the involvement of subducting sediments rather than dehydrated oceanic crust in the source. Our latest findings, integrated with previous studies, indicate that the arc-related rocks exhibiting light Mo isotopes may not solely originate from the rutile-breakdown oceanic crust source but could also result from sediment melting at various sub-arc depths. Consequently, sediment-derived melts play a crucial role in Mo isotope cycling and the formation of arc magmas in subduction zones.

 

1 Chen, S., et al., Nat. Comm. 10, 4773 (2019). 2 Freymuth, H., et al., EPSL 432, 176-186 (2015). 3 Huang, F., et al., GCA 341, 75-89 (2023). 4 König, S., et al., EPSL 447, 95-102 (2016). 5 McCoy-West, A.J., et al., Nat. Geos.12, 946-951 (2019). 6 Willbold, M. & Elliott T., CG 449, 253-268 (2017).

How to cite: Huang, F., Li, J., Xu, J., and Zeng, Y.: Role of sediment-derived melts in Mo cycling of subduction zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4498, https://doi.org/10.5194/egusphere-egu24-4498, 2024.

EGU24-4770 | ECS | PICO | GD2.1

Geochronological, petrological and tectonic implications of the Proterozoic massif-type anorthosite intrusions and related rocks from the northern Oaxacan Complex, southern Mexico 

Luis Alejandro Elizondo Pacheco, Luigi Solari, Hailong He, Juan Alonso Ramírez Fernández, and Roberto Maldonado

Massif-type anorthosite intrusions are enigmatic and significant crustal components widespread worldwide. They occur either as individual massifs or accompanied by mangerite, charnockite, and granite (AMCG suite). This Proterozoic phenomenon has been studied in numerous complexes, generating long-lasting discussions regarding the magmatic source and the tectonic setting where these rocks form. This controversy is still a matter of debate after decades of scientific research. In this sense, Mexico represents a unique and new opportunity to explore such petrological issues because its exposures of massive anorthosite and associated lithologies are mainly unstudied. These rocks are better exposed in the Oaxacan Complex, the most extensive Mexican inlier of Grenvillian rocks. This work is focused on its northern portion. This area is characterized by 1.4-1.1 Ga metamorphic rocks from the El Catrín and El Marquez units that were later intruded by anorthosite, gabbro, leucogabbro, oxide-apatite gabbronorites (OAGN), and granite bodies from the Huitzo suite. New LA-ICP-MS U-Pb zircon data revealed similar crystallization age ranges in the gabbro-anorthositic (1013-960 Ma) and granitic (1012-964 Ma) rocks. Their zircon Hf-O isotopic composition was compared with previous and new data from the older units of the area to assess the possible interaction between mantle- and crustal-derived melts during their generation. The intrusions of massive anorthosite and gabbro exhibit εHf(t) values of -2.54-4.79 and δ18O = 6.84-8.03‰. The granitic rocks have εHf(t) values of -0.79-2.87 and δ18O = 7.80-8.42‰. The lack of mantle-like εHf(t) and δ18O values suggests the participation of high-δ18O supracrustal material with more radiogenic Hf signatures during their generation. Simple binary mixing modeling indicates that the gabbro-anorthositic intrusions incorporated ~20-30% of metasedimentary country rocks, supporting a mantle-dominated origin. A slightly higher crustal component is recognized in the studied granitic intrusion. We also propose that these rocks permit an alternative model where Oaxaquia is paleogeographical relocated close to the eastern margin of Laurentia during the final stages of Rodinia amalgamation due to the resemblance in age to the late- to post-Grenvillian AMCG rocks (1016-956 Ma) outcropping there (e.g., Roseland, Mattawa, Labrieville, and Vieux Fort). This new tectonic view challenges the classical Amazonia-Oaxaquia-Baltica connection.

How to cite: Elizondo Pacheco, L. A., Solari, L., He, H., Ramírez Fernández, J. A., and Maldonado, R.: Geochronological, petrological and tectonic implications of the Proterozoic massif-type anorthosite intrusions and related rocks from the northern Oaxacan Complex, southern Mexico, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4770, https://doi.org/10.5194/egusphere-egu24-4770, 2024.

The geodynamic regime driving formation of Archean felsic continent crust is still an ongoing debated and unsolved fundamental issue. The episodic Archean TTGs and associated granitoids, with emplacement ages of ca. 2.9, 2.7 and 2.5 Ga, occurred in the Jiaobei Terrane, North China Craton (NCC), provide prolonged continuous records of formation processes of Meso-Neoarchean felsic continental crust. To track patterns of crust-mantle differentiation, crustal reworking and recycling, and accordingly, constrain underlying geodynamic regimes associated with formation of the Meso-Neoarchean felsic continental crust, we present comprehensive zircon U-Pb dating, Hf-O isotopes and whole-rock major- and trace-element geochemical data for the episodic Archean TTGs and associated granitoids. The comprehensive dataset decodes the generation of the episodic Archean TTGs over wide-range pressure conditions from amphibolite to eclogite facies and Meso-Neoarchean coupled crust-mantle differentiation, which was likely driven by episodic hot mantle (plume) upwelling. In addition, the ca. 2.9 and 2.7 Ga TTGs shared identical Mesoarchean juvenile crust source and exhibit consistent mantle-like zircon δ18O values, whereas the ca. 2.5 Ga TTGs mainly derived from distinctly younger Neoarchean juvenile crust, implying removal and replacement of the Mesoarchean juvenile lower crust. Importantly, some ca. 2.5 Ga TTGs, granitic gneisses and sanukitoids exhibit significantly higher zircon δ18O values than mantle δ18O values, demonstrating occurrence of Neoarchean supracrustal recycling. Consequently, the combined geochemical dataset with geological evidence allow us to track the geodynamic processes for the formation of the Meso-Neoarchean felsic continent crust in the Jiaobei Terrane, NCC: Episodic hot upwelling mantle (plume)-lithosphere interactions at ca. 2.9, 2.7 and 2.5 Ga resulted in the coupled crust-mantle differentiation over different depths to produce the spatial-temporally coexisted various-pressure-type TTGs, juvenile crust and voluminous dense lower crustal restite, respectively. Subsequently, dense lithospheric delamination triggered by gravitational instability occurred, followed by continental uplifting, subduction of altered oceanic crust, and asthenosphere and mantle-derived mafic melts upwelling, resulting in extensive occurrences of anatexis and metamorphism with anticlockwise P-T paths in the medium-lower crust at ca. 2.5 Ga. Along with large-scale melting and cooling of mantle, thick stable craton lithosphere with strong rigidity and viscosity had likely developed by the end of Neoarchean. The geodynamic processes in Meso-Neoarchean were likely diverse, especially episodic hot upwelling mantle (plume) -lithosphere interaction could be a favored geodynamic regime responsible for formation of Archean felsic continental crust in the Jiaobei Terrane, NCC.

How to cite: Liu, J.: Meso-Neoarchean coupled crust-mantle differentiation followed by gravity-driven lithospheric delamination and subduction initiation in the North China Craton, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4864, https://doi.org/10.5194/egusphere-egu24-4864, 2024.

EGU24-5761 | PICO | GD2.1

Can Venus and Mars Inform Us About Intraplate Magmatism on Earth? 

Scott King, Megan Duncan, Grant Euen, Joshua Murphy, Savaria Parrish, and Matt Weller

Venus and Mars have operated as one-plate planets for some or all of their history and intraplate magmatic activity on Earth has been suggested as an analogue for the observed volcanic activity on these bodies. Flipping the question around, what can we learn about intraplate magmatism on Earth from other planets?

Volcanic features, including extensive lava flows and vast lava plains, cover large portions of the Martian surface. Mars has two large volcanic provinces: Tharsis and Elysium. While the continent-sized region of elevated terrain called the Tharsis rise receives most of the attention, Elysium—the second largest volcanic province on Mars—is larger than the Ontong-Java plateau—the largest LIP on Earth. Activity detected by the InSight seismometer near Cerberus Fossae (located in Elysium Planitia, southeast of the Elysium volcanic province) is consistent with fluid flow at depth. Cerberus Fossae is among the youngest tectonic structures on Mars and large discharges of water and lava have been proposed to explain the geomorphic structures observed at Cerberus Fossae. The regional gravity and topography, volcanic history, and seismic activity at Cerberus Fossae are consistent with a present-day 2,000-km-radius plume head beneath Elysium Planitia. The characteristics of the Elysium Planitia plume are comparable to terrestrial plumes proposed to explain the formation of terrestrial LIPs. Plumes on Mars appear to be spatially stable for long periods of time, reflecting the stabilizing influence of a thick stagnant lid and sluggish mantle convection.

While Venus is nearly the same size as Earth, there is no evidence supporting Earth-like plate tectonics for the past 250-750 Myrs. The similarity in size invites comparison of present-day volcanic activity between the two planets. This is complicated by the presence of plate tectonics where volcanic activity at ridges and subduction zones has no clear analogue on Venus. Expanding intraplate volcanism on Earth suggests as many as 100 active volcanic events per year on Venus. While detecting surface changes is one goal of the upcoming NASA and ESA Venus missions, surface change associated with volcanic activity has already been found in the Magellan image archive. Herrick and Hemsley identified a 2 km2 volcanic vent that changed shape in the eight months between two Magellan radar images. While sulfuric acid clouds obscure our view of the surface, those same clouds provide the best evidence for ongoing volcanic activity. Assuming the primary mechanism removing atmospheric SO2 is a reaction between calcium minerals on the surface and SO2, an SO2 residence time of ~2 Myrs is required. This requires an outgassing rate of ~6x1010 kg SO2/year—about the same yearly SO2 outgassing rate measured on Earth over the past decade. Converting this outgassing rate to erupted lava, an eruption rate on Venus of ~1 km3/yr is obtained.

How to cite: King, S., Duncan, M., Euen, G., Murphy, J., Parrish, S., and Weller, M.: Can Venus and Mars Inform Us About Intraplate Magmatism on Earth?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5761, https://doi.org/10.5194/egusphere-egu24-5761, 2024.

This study presents the first comprehensive investigation into the petrography, major and trace element mineral chemistry of a mantle-derived eclogite xenolith suite from the Balmoral kimberlite. Most of the eclogite xenoliths from the Balmoral kimberlite pipe are bimineralic (garnet and clinopyroxene) rocks with a substantial number of corundum-bearing xenoliths also recognised. The bimineralic eclogites are classified into low MgO (<15 wt% MgO) and high MgO (<15 wt% MgO) varieties. Mica with average modal abundances ≤10 vol% is observed as an accessory phase in bimineralic xenoliths. Modal abundances of corundum in corundum-bearing samples range between 1 and 6 vol%. Textures are ambiguous in Balmoral eclogites, while the chemical criteria of McCandless and Gurney (1989) place all of them into Group II. The temperature range of Balmoral eclogites (at an assumed pressure of 50 kbar; Ellis and Green, 1979) is between 1046 and 1311 °C. The low-MgO bimineralic eclogites are characterised by relatively higher temperatures than the high-MgO variety. Corundum-bearing eclogites have the highest equilibration temperatures. Based on calculated temperatures, corundum-bearing eclogites have the highest inferred pressures of equilibration with the high-MgO eclogite variety having the lowest. The reconstructed Balmoral major element bulk compositions are characterised by variations in MgO, CaO and Al2O3 contents, with less variation in FeO contents. Reconstructed major element bulk compositions from bimineralic eclogites coincide with those of tholeiitic basalts, and to a lesser extent, basalts from mid-ocean ridges and oceanic gabbros. Corundum-bearing eclogites are similar to oceanic gabbros in general. The REE pattern of bulk eclogite commonly show humped-shaped REEN patterns. High MgO eclogites have a slight enrichment in the LREEN pattern while low MgO eclogites have enrichment in HREEN patterns. These REEN patterns are broadly comparable to those of oceanic gabbro and MORB. The protolith for these Balmoral eclogite xenoliths is thought to be a once composite oceanic crustal section which underwent partial melting during subduction and/or dehydration and, subsequent metasomatic re-enrichment in incompatible trace elements.

How to cite: Pattnaik, J. and Viljoen, F.: Petrology and geochemistry of a Cratonic mantle-derived Eclogite Xenolith Suite from the Balmoral Kimberlite, Kimberley Region, South Africa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6583, https://doi.org/10.5194/egusphere-egu24-6583, 2024.

EGU24-7403 | ECS | PICO | GD2.1 | Highlight

Quaternary volcanism in southeastern Tibetan Plateau: A record of stagnant oceanic slab in the mantle transitional zone 

Huan Kang, Yongwei Zhao, Xiaoran Zhang, Liyun Zhang, Huiping Zhang, and Haibo Zou

The Tibetan lateral mantle flow bears considerable significance in deciphering the material movement mechanisms within global plate convergence zones. However, the front edge of this mantle flow is unclear. Here we conduct petrological, geochronological, mineralogical, geochemical and Sr-Nd-Pb isotopic investigations on Quaternary intracontinental alkali basalts from the southwestern Yunnan (the south of 27°N), to determine the source characteristics and geodynamic mechanisms of the Quaternary alkali basalts in southeastern Tibetan Plateau and to trace the recent Tibetan mantle flow. Alkali basalts in the region are mainly basanite and trachybasalt with eruptions during the Pleistocene epoch. They possess a highly incompatible elemental and radiogenic Sr-Nd-Pb isotopic composition similar to those of the Ocean Island Basalts, consistent with melts derived from asthenospheric mantle with low-degree partial melting. Calculated magma-water contents of regional alkali basalts range from 1.32 ± 0.48 wt.% to 2.23 ± 0.18 wt.%, corresponding to 269 ppm to 3591 ppm water contents of their mantle source, which are significantly higher than that of the normal upper mantle (i.e., 50–250 ppm). Quantitative trace-element modelling and dramatic variations in oceanic crust-sensitive indicators such as Eu/Eu*, Sr/Sr*, Ce/Pb, (Nb/Th)N-PM and (Ta/U)N-PM indicate variable contributions of upper and lower oceanic crust to magma sources. Systematic examinations of petrological, geochemical, and geophysical evidence reveal that the temporary small-volume Quaternary volcanism in southeastern Tibetan Plateau is not related to Tibetan southeastward mantle flow but is primarily attributed to stagnant Neo-Tethyan slab in the mantle transition zone.

How to cite: Kang, H., Zhao, Y., Zhang, X., Zhang, L., Zhang, H., and Zou, H.: Quaternary volcanism in southeastern Tibetan Plateau: A record of stagnant oceanic slab in the mantle transitional zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7403, https://doi.org/10.5194/egusphere-egu24-7403, 2024.

A low-velocity layer atop the mantle transition zone has been extensively observed worldwide, which may play an important role in mantle dynamics and Earth habitability. In subduction zones, this layer is widely explained as partial melting triggered by slab subduction on a regional or global scale. However, direct observational evidence is still absent, and the response of the layer to slab subduction is not well known. Here, we image the seismic velocity around the mantle transition zone by matching synthetic and observed triplicated seismic P and sP waveforms in the Indian–Eurasian continental subduction zone. Our observations reveal a laterally varied low-velocity layer atop the mantle transition zone beneath the Hindu Kush, where a subducted slab extends to the mantle transition zone. It is characterized by thickness of 56-94 km and P-wave velocity drop of -2.8~-4.7%. The geometric morphology of the low-velocity layer indicates that it is a partially molten layer induced by the subducted slab on a regional scale. Interestingly, our observations also support that the layer has a low viscosity. The decreased viscosity possibly facilitates slab motion in the deep domain; however, the buoyant continental crust in the shallow domain likely resists downwards movement of the slab. This differential movement is more likely to cause slab stretching, tearing and break-off in the middle region, which may contribute to explaining rare recurring large intermediate-depth earthquakes in an intracontinental setting.

How to cite: Li, G.: Seismic evidence of upper mantle melt caused by a subducted slab in the Indian-Eurasian continental subduction zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7577, https://doi.org/10.5194/egusphere-egu24-7577, 2024.

EGU24-8338 | ECS | PICO | GD2.1

The alkaline rocks olivine variety: a case study of Namuaive Pipe, Kola alkaline province, Russia 

Natalia Lebedeva, Anna Nosova, Lyudmila Sazonova, Alexey Kargin, Darina Shaikhutdinova, Vasiliy Yapaskurt, and Vasily Shcherbakov

An alkaline magma undergoes significant modification during its ascent to the surface due to assimilation of mantle and crustal material, exsolution of volatiles, trapping of crystals from earlier crystallized melt batches, fractional differentiation and explosive processes, making a thorough understanding of the petrogenesis of the magma and the nature of its mantle source in large igneous provinces difficult. The dikes and pipes of ultramafic lamprophyres, picrites and nephelinites are characterised by rapid rise of melt batches that could provide a high chance of preserving unworked mantle and crustal material. A study of olivine from these rocks may help to resolve some issues of their mantle sources and melt evolution.

The Namuaive pipe located in the northern part of the nepheline syenite Khibina Massif, Kola alkaline province. The pipe is filled by pyroclastic alkaline picrite (melanephelenite). The rock is texturally heterogeneous, consisting of 30-40 vol % magmaclasts and lapilli, phenocrysts and macrocrysts (up to 40 vol %) of phlogopite, olivine and clinopyroxene, xenoliths of Khibina Massif rocks, and fine grained matrix composed of phlogopite, apatite, perovskite, spinel, Ti-magnetite, nepheline, sodalite, high-Ti garnet.

Olivine is one of the most abundant macrocrysts in alkaline picrite, ranging up to 30 vol %; it is fresh or slightly replaced by serpentine or clinopyroxene-phlogopite intergrowth. Three groups of olivine based on core-to-rim zonation were observed:

  • Euhedral-to-subhedral olivine grains up to 5 mm are phenocrysts. Some grains have spinel inclusions. Phenocrysts show normal Mg#-zonation. They consist of a more magnesian core (Mg# = 0.90-0.89) with Ni content from 1595 to 3058 ppm and a thin marginal ferruginous zone (Mg# = 0.89-0.83) with Ni content from 363 to 2663 ppm.
  • Antecrysts have rounded and often corroded edges. Their size ranges from the first few hundred µm to 1 mm. They are characterised by Fe-rich cores (Mg# = 0.84-0.87) with a wide range of Ni contents from 1200 to 3200 ppm, surrounded by a transitional zone with a gradual increase in magnesium (Mg# = 0.86-0.89) and Fe-rich rind (Mg# = 0.89-0.86) with Ni contents from 1500 to 605 ppm. They have a small clinopyroxene-phlogopite rim and spinel along cracks.
  • The xenocrysts have been divided into two subgroups according to their Mg# and Ni contents. The cores of the first subgroup have Mg# 0.90-0.91 and Ni contents from 2800 to 3200 ppm, the cores of the second subgroup have Mg# 0.91-0.93 and Ni content about 2000 ppm. The rims of both subgroups have Mg# 0.83-0.85 and Ni contents from 1236 to 433 ppm. Some olivine grains are intergrown with high-Cr clinopyroxene and high Mg phlogopite.

The antecrysts reflect mixing of the evolved lamprophyric melts during previous pulses with the partial melt batch that formed the Namuaive pipe. Phenocrysts and other olivine rims formed during fractional crystallization. Antecrysts and phenocrysts equilibrated to melts from wehrlite sources.

The study was supported by the Russian Science Foundation under Grant No 23-77-01052

How to cite: Lebedeva, N., Nosova, A., Sazonova, L., Kargin, A., Shaikhutdinova, D., Yapaskurt, V., and Shcherbakov, V.: The alkaline rocks olivine variety: a case study of Namuaive Pipe, Kola alkaline province, Russia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8338, https://doi.org/10.5194/egusphere-egu24-8338, 2024.

The modal metasomatic alteration for lithosphere mantle may be investigated using mantle xenoliths from kimberlite pipes. The pyroxenite xenoliths from diamondiferous upper-Devonian Udachnaya kimberlite pipe (Daldyn field, Yakutia) were studied, mineral chemical composition was researched. The several stages of metasomatic processes were observed in the lithospheric mantle under the Udachnaya kimberlite pipe.

The most garnets from studied xenoliths demonstrated so-called “normal” trace element distribution that closed to the element coefficients the basalt - silicate melt. All garnets are characterized by a maximum in Ta, a minimum in La-Ce, and a minimum in Ti. Eclogites (especially with a mosaic texture) are characterized by a small minimum in Eu, which may indicate the presence of Pl in the initial rock. The presence of eclogitic xenoliths (with Eu-minimum in garnet) indicates the influence of the subduction component. The pyroxenite xenoliths with narrow variations in the composition of minerals indicates their crystallization from melts, accompanied later by metamorphic recrystallization. The 10% studied xenoliths are observed the secondary metasomatic amphibole (pargasite - taramite) - the evidence of modal Amph metasomatism. The Ti/Eu – La/Yb distribution for clinopyroxene and amphibole demonstrate the influence of silicate (not carbonatite) melts.The increasing concentrations of HFSE and REE group elements can also be traced by the Cpx and Grt chemical composition, it may be indicating the asthenospheric melts. Several garnet samples from high-Zr (80–100 ppm) eclogites demonstrated the features of fluid metasomatism (fluid-produced, accompanied by phlogopite crystallization). Another sign of the alkaline melts influence is secondary Na silicates crystallization (according reaction Grt + Omphacite + K - Fluid = Amph + Сpx2 ± Cal ± Sodalite).

Thus, several stages of metasomatic processes were observed in the lithospheric mantle under the Udachnaya kimberlite pipe. The presence of eclogite xenoliths (with a Eu minimum) indicates the influence of a subduction component. The presence of pyroxenite xenoliths with narrow variations in mineral composition indicates their crystallization from melts - the second stage of metasomatic processes, subsequently be accompanied by metamorphic recrystallization. The content of trace elements in garnets indicates the asthenospheric nature of the melts. Such melts brought elements of the HFSE and REE groups, as well as Pt, Pd and Re. The last stage is most clearly traced using modal Amph metasomatism. The presence of secondary amphibole indicates widespread occurrence of silicate pre-kimberlite metasomatism in the lithospheric mantle beneath the center of the Siberian craton.

The research was supported by Russian Science Foundation grant № 22-77-10073.

How to cite: Kalashnikova, T. and Kostrovitsky, S.: The silicate and carbonatite metasomatic alterations in lithospheric mantle under Siberian craton (the evidence of mantle xenoliths from Udachnaya pipe), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11448, https://doi.org/10.5194/egusphere-egu24-11448, 2024.

EGU24-14538 | PICO | GD2.1

Features of the introduction of magmatic melts in permeable zones of the platform cover 

Yury Perepechko, Konstantin Sorokin, and Sherzad Imomnazarov

The problem of the introduction of heterophase magmatic melts into the conducting channels of the lithospheric mantle under the cratons of the Siberian platform has been studied numerically. The analysis of the features of the introduction of melts was carried out on the basis of a hydrodynamic model of the evolution of magmatic and fluid-magmatic systems. The mathematical model describes the two-speed dynamics of the redistribution of hot heterophase melts and magmatogenic fluids in the flow during their movement from the generation zones to the platform cover, as well as the processes of heat and mass transfer between melts and rocks in permeable zones of the lithosphere. The nature of the flow of mixtures of liquid fractions of aluminosilicate, sulfide, native and oxide liquids, in which a sub-liquid solid phase appears during movement and decompression boiling occurs, the features of heat and mass transfer processes determine the type of magmatic and magmatogenic deposits of the trap formation of the Siberian platform. The flow of magmatic melts in a wide temperature range of 300-1200 °C, the viscosity of the melt phases of 101-106 N, as well as the rate of penetration and the degree of stratification of the heterophase magmatic flow were studied.

The figure shows an example of the randomization of an intrusive flow. (a) (b) An example of the development of heterogeneity in the distribution of the concentration of particles of the dispersed phase (a, m-3) and temperature (b, °C) in an initially stratified magmatic flow embedded in the host rocks. The temperature of the introduced flow is 500 °C, in the channel at the initial moment standard thermodynamic conditions; the dynamic viscosity of the melt is 102 P. The work was carried out with the financial support of the Russian Science Foundation, grant No. 24-27-00411.

How to cite: Perepechko, Y., Sorokin, K., and Imomnazarov, S.: Features of the introduction of magmatic melts in permeable zones of the platform cover, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14538, https://doi.org/10.5194/egusphere-egu24-14538, 2024.

EGU24-14806 | PICO | GD2.1

Reconstructions of mantle structure beneath kimberlites of Anabar shield and surroundings – similarities and differences. 

Sergey Kostrovitsky, Igor Ashchepkov, Svetlana Babushkina, and Nikolai Mdevedev

Comparative study of the mantle xenocrysts from Anabar region (Ary-Mastakh, Dyuken, Orto-Yargyn fields) and Boomerang kimberlites and pipe show essential differences with the mantle in surrounding area from Olenek (Chomurdakh field)

The PTX diagram show presence of the rare lherzolitic pyrope and abundant eclogitic almandines to 6 GPa. In suture zone of Daldyn and Magan terranes (Boomerang pipe) eclogitic omphacites and Cr less pyroxenites and Cr diopsides occurs mainly in the middle mantle part the pyroxenite layer possibly formed after eclogites due to plume melt interaction. Long ilmenite fractionation trend extends from the lithosphere base to the GPa 2.5, which is typical. Geochemistry of minerals vary from most depleted pyropes with V-U shaped REE patterns typical of arc mantle and Ba, U peaks and HFSE minima of subduction type. The fertilization produced the increase of the incompatible elements and sometimes LILE and The marginal parts of the SCLM of Anabar shield are extremely enriched in eclogitic deep-seated material located in lower SCLM part and demonstrating similar thermobarometric trends and features to the diamond inclusions from the Ebelyakh (Mayat) placers. Mantle column beneath several pipes (Losi, Universitetskaya, Kuranakh) contain Cr amphiboles distributes from lithosphere base to Moho. Comparison of reconstructed SCLM beneath Anabar and Chomurdakh field reveal more fertile compositions of the mantle rocks and simpler structure for later field. Abundance of eclogites in Kuranakh and Orto-Yargyn kimberlite in the lower mantle lithosphere part and their PTX trends are similar to the eclogitic diamond inclusions from the Ebelyakh placers. This increase the possibility of finding of diamonds deposits in Anabar shield kimberlites.

RNF grant No. 24-27-00411

How to cite: Kostrovitsky, S., Ashchepkov, I., Babushkina, S., and Mdevedev, N.: Reconstructions of mantle structure beneath kimberlites of Anabar shield and surroundings – similarities and differences., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14806, https://doi.org/10.5194/egusphere-egu24-14806, 2024.

EGU24-16571 | PICO | GD2.1 | Highlight

The origin of melilitites: preliminary results on melting of a carbonated wehrlite 

Stefano Poli and Leone Melluso

Melilitites are ultramafic magmas characterized by normative Ca2SiO4, larnite, high FeO* and TiO2. Liquids compositionally close to melilitites were experimentally reproduced from carbonated lherzolites in alkali, Fe and Ti-free model systems at 3.2-3.3 GPa, approx.  1500 °C (Gudfinnsson & Presnall, 2005), at relatively high melt proportions. In complex compositions, MORB-eclogite derived, carbonated, partial melts reacted with a fertile peridotite were proposed at the origin of melilitites (Mallik & Dasgupta, 2013, 2014). The experimental reconstruction of phase relationships along a join olivine melilitite - carbonate revealed that at 3 GPa, clinopyroxene and olivine or garnet are stable on the liquidus (Brey & Ryabchikov, 1994), suggesting that carbonated wehrlites are potential sources for the genesis of melilitites.

Here, we explore phase relationships on the high pressure melting of a model wehrlite, initially composed of a mechanical mixture of San Carlos olivine, diopside, aegirine, dolomite, rutile and kyanite. Starting materials were loaded in graphite capsules, inserted in sealed platinum capsules. Vitreous carbon spheres and synthetic diamond grains were adopted for liquid traps. 

Preliminary experimental results show that at 3 GPa the solidus is located at temperatures lower than 1200 °C. A thick, orthopyroxene-rich layer, with polygonal microstructure, forms at contact with aggregates resulting from quenched liquids, both at 1200 °C and 1400 °C. Estimates of liquid composition are melilititic, with TiO2 approx. 2.5 wt.% on a volatile free basis.

Currently available experiments suggest that the solidus is controlled by the reaction dolomite + olivine + clinopyroxene = orthopyroxene + liquid, as suggested in Eggler (1976). This is feasible only if the liquid composition is located on the CaO-rich side of the plane diopside-forsterite-dolomite in the model system CaO-MgO-SiO2-CO2, i.e. on the normative larnite (akermanite) portion of the tetrahedron.

 

Brey G.P. & Ryabchikov I.D. (1994). Carbon-dioxide in strongly silica undersaturated melts and origin of kimberlite magmas. Neues Jahrbuch Fur Mineralogie-Monatshefte, (10), 449-463.

Eggler D.H. (1976). Does CO2 cause partial melting in the low-velocity layer of the mantle?. Geology4(2), 69-72

Gudfinnsson G.H. & Presnall D.C. (2005). Continuous gradations among primary carbonatitic, kimberlitic, melilititic, basaltic, picritic, and komatiitic melts in equilibrium with garnet lherzolite at 3–8 GPa. Journal of Petrology46(8), 1645-1659.

Mallik A. & Dasgupta R. (2013). Reactive infiltration of MORB-eclogite-derived carbonated silicate melt into fertile peridotite at 3 GPa and genesis of alkalic magmas. Journal of Petrology54(11), 2267-2300

How to cite: Poli, S. and Melluso, L.: The origin of melilitites: preliminary results on melting of a carbonated wehrlite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16571, https://doi.org/10.5194/egusphere-egu24-16571, 2024.

EGU24-20570 | PICO | GD2.1

On a tectonics, magmatism and hydrocarbons (HC, oil-gas) of the South Caspian - West Baluchestan, Middle East: some problems and constraints 

Alexander Romanko, Nazim Imamvderdiyev, Ilya Vikentiev, Bahman Rashidi, Mehrdad Heidari, and Anton Poleshchuk

Joint analysis of tectonics, magmatism, metallogeny, and hydrocarbons (HC – oil-gas) for the South Caspian - west Baluchestan, Middle East (Alpine time mainly) was made. Different anomalies and degassing here are of interest too.  Specific anomalous deep regime and degassing of CH4, H2 etc. due to a giant African superPlume activity are noted too. Such points discussed as follows:

1.      Alpine North-Eastern (NE) tectonic zoning exists in this region up to Present (Q4). Anomalous long-lived African superPlume activity influences on regional tectonics, related magmatism and fluid regime (Fig.). There are different anomalies in this region on gravity, hydrocarbons (HC), degassing etc.

2. Miocene – Recent (N1-Q) intraplate magmatism with: different subalkaline- alkaline rocks directly relates to superPlume mentioned. There are data about Sr, Ca etc. input in upper younger Caspian Sea sediments from the lower older magmatites. Such magmatic trend exists as: Quaternary carbonatites, Hanneshin, Helmand block (Afghanistan) - Ca-rich volcanites with CaO up to 34.8% -  trachyandesites with CaO = 7.2%.  

  • Oligocene-Recent (Pg3-Q) calk-alkaline subduction-related rocks are as antipodes to mentioned intraplate rocks (intrusive, extrusive and volcaniclastic ones). Relation with African superplume is not formally necessary, but there are our data about warmer calk-alkaline rocks here, ex., warm melt inclusions in them with T crystallization as 1180oC.
  • Decreasing of earthquakes activity from South to the Middle Caspian Sea, at

least (Khain, Bogdanov, 2003 etc.). HC resources decreasing from Persian Gulf to North Caspian Sea

  • Lesser order HC zoning (west to east: oil - gas) in the S-M Caspian Sea exists. Is Great Caucasus a barrier for HC in lesser order?
  • A regional tectonic - HC correlation in Iraq - South Caspian- Turkmenistan exists: more compression and oil in west of region versus less compression and gas in the east of region up to the east Turkmenistan with, however, non-deep sea conditions (transitional facies) in the latter. Moreover, unusual several times repeating of oil - gas - gas-condensate in a stratigraphic section is revealed in west Turkmenistan. Is it a result of deep fluids input too? HC behavior and zoning is not quite clear in this unique economic and geological region.
  • Other HC north-south (N-S) zoning is as follows: HC in the old rocks - since Devonian up to Paleogene (D-Pg) – North Caspian Sea vs. HC in Triassic-Jurassic, Paleogene rocks in the Middle Caspian Sea, and in Low Pliocene (N2) rocks - South Caspian Sea. It could be in agreement with northeastern (NE) superplume activity decreasing. Giant HC resources in Saudi Arabia – Caspian region could be related with this hot regime. HC localizations are in agreement with a regional general geology. Surely, the oil genesis is traditional – organic one.

There is a good correlation as detailed HC structural map - HC maximum. It is in agreement with a young concrete HC localization despite the different age of host rocks.  Mud volcanoes (Kholodov, 2012 etc.) – HC – Salt – magmatism - tectonics in this region studied is the one system.    

This work was made due to the State program of the Geological Institute RAS.

How to cite: Romanko, A., Imamvderdiyev, N., Vikentiev, I., Rashidi, B., Heidari, M., and Poleshchuk, A.: On a tectonics, magmatism and hydrocarbons (HC, oil-gas) of the South Caspian - West Baluchestan, Middle East: some problems and constraints, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20570, https://doi.org/10.5194/egusphere-egu24-20570, 2024.

EGU24-473 | ECS | Orals | GD1.2

Deep plumbing model of the Cenozoic Manzaz / Atakor intraplate volcanic system, Central Hoggar, Northwest Africa, based on electrical resistivity models 

Zakaria Boukhalfa, Matthew J. Comeau, Amel Benhallou, Abderrezak Bouzid, and Abderrahmane Bendaoud

Continental intraplate volcanic systems, with their location far from plate tectonic boundaries, are not well understood: the crustal and lithospheric mantle structure of these systems remain enigmatic and there is no consensus on the mechanisms that cause melt generation and ascent. The Cenozoic saw the development of numerous volcanic provinces on the African plate. This includes the Hoggar volcanic province, located in Northwest Africa, part of the Tuareg shield. It is composed of several massifs with contrasting ages and eruptive styles. The magmatic activity began at around 34 Ma and continued throughout the Neogene-Quaternary. Phonolite and trachyte domes as well as scoria cones and necks are found in the Manzaz and Atakor volcanic districts. In order to image the crustal and lithospheric mantle structure of this region, and to understand the origins and potential mechanisms of the continental intraplate volcanic activity in the Central Hoggar and specifically the Atakor/Manzaz area, we acquired magnetotelluric (MT) measurements from 40 locations and generated a 3-D electrical resistivity model. The model covers an area of about 100 km by 200 km. Images of the subsurface architecture, in terms of electrical resistivity, from the near-surface to the lithospheric mantle, allow us image the deep plumbing system of the volcanic system. Low resistivity features (i.e., conductors) in the crust that are narrow, linear structures trending approximately north-south, are revealed along the two boundaries of the Azrou N’Fad terrane, in the Manzaz area. They likely reflect the Pan-African mega-shear zones, which were reactivated throughout the tectonic evolution of the region. The model reveals that these faults are lithospheric-scale. In addition, the low-resistivity features likely represent the signatures of past fluid flow. The location of the recent Cenozoic volcanic activity was likely influenced by the pre-existing structure. A deep feature of moderate conductivity is located in the upper lithospheric mantle directly beneath the Manzaz and Atakor Volcanic Districts. It may represent the origin of the overlying anomalies and may suggest metasomatism of the sub-continental lithospheric mantle.

Keywords:  intraplate, Hoggar, alkaline volcanism, magnetotelluric, electrical resistivity.

How to cite: Boukhalfa, Z., J. Comeau, M., Benhallou, A., Bouzid, A., and Bendaoud, A.: Deep plumbing model of the Cenozoic Manzaz / Atakor intraplate volcanic system, Central Hoggar, Northwest Africa, based on electrical resistivity models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-473, https://doi.org/10.5194/egusphere-egu24-473, 2024.

EGU24-1021 | ECS | Posters on site | GD1.2

Geochemistry and geochronology of the High Arctic Large Igneous Province on Svalbard 

Anna Marie Rose Sartell, Christoph Beier, Ulf Söderlund, Kim Senger, Grace E. Shephard, Hans Jørgen-Kjøll, and Olivier Galland

Large Igneous Provinces are defined as magmatic provinces with large magma volumes (> 100,000 km3) emplaced and/or erupted in an intraplate tectonic setting over a vast area within a few Myr, thus having the potential for significant impact on the global climate. The High Arctic Large Igneous Province (HALIP) was emplaced during the Cretaceous. The available ages, ranging between ~140 and 80 Ma, suggests that the magmatism was apparently long-lived and multi-phase. Extrusive and intrusive remnants of the HALIP can be found across the circum-Arctic, specifically in Arctic Canada, Russia, Svalbard, Northern Greenland, and the Arctic Ocean. On Svalbard, the HALIP magmatism is regionally called the Diabasodden Suite. Here, the dolerites have mainly been emplaced as sills at shallow depths and occur all over the archipelago. Despite the relative accessibility of outcrops, the HALIP on Svalbard has been mostly unexplored. As such, available U-Pb geochronology of the Diabasodden Suite is limited, but indicates a shorter time span of 125 – 122 Ma.

Yearly field campaigns since 2020 have resulted in over 150 collected samples from Spitsbergen and Nordaustlandet. This has been accomplished through a collaborative effort, and by strategically targeting outcrops to build a good representative dataset of the Diabasodden Suite. Additionally, a large number of samples have also been taken for a detailed case-study in central Spitsbergen. The dolerite samples are used for whole-rock major and trace element geochemical analysis, U-Pb baddeleyite geochronology and petrological studies. Furthermore, during all field campaigns, high-resolution drone images have also been acquired. These data form the basis for digital outcrop models (DOMs), which are used for thickness measurements of the sills and to put the geochemical data into a 3D perspective. The resulting DOMs are made openly available through the geoscientific database of Svalbard, SvalBox.

Here we present a review of the available geochronology of the HALIP in the circum-Arctic, as well as new data from Svalbard. Specifically, new U-Pb baddeleyite ages of one mafic sill in northern Isfjorden, and an extensive dataset of whole-rock geochemical data from the HALIP on Svalbard to better understand the magmatic history of the HALIP as a whole.

How to cite: Sartell, A. M. R., Beier, C., Söderlund, U., Senger, K., Shephard, G. E., Jørgen-Kjøll, H., and Galland, O.: Geochemistry and geochronology of the High Arctic Large Igneous Province on Svalbard, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1021, https://doi.org/10.5194/egusphere-egu24-1021, 2024.

The origin of intraplate magmatism is debated, with two main hypotheses having been proposed. These are deep-seated high-temperature sources (plumes), and  intraplate extension driven ultimately by plate tectonics. A test region in this debate is the 'Jurassic Corridor,' a geological feature proposed to span North America, which contains igneous rocks including kimberlites that are attributed to the Great Meteor Hotspot (GMH). Despite longstanding assumption of this model, close inspection using modern, much-expanded geological information sets shows that the existence of a Jurassic Corridor and GMH lacks support. In this paper we reassess the distribution of kimberlites in North America and on neighboring landmasses. We demonstrate the lack of a clear Jurassic Corridor and show instead that the kimberlites and related rocks are more likely linked to the breakup of the Pangaean Supercontinent and controlled by lithospheric structures. Furthermore, by comparing these findings with global plate models for the last 300 Myr we identify three prominent age peaks in North American kimberlite occurrence that broadly align with periods of heightened plate velocity with respect to Africa. Additionally, the analysis reveals in Africa two peaks in kimberlite abundance and two velocity peaks with respect to North America. Here, however, the velocity peaks occurred approximately 20-30 Myr before the kimberlite abundance peaks. These observations underscore the significance of plate kinematics in controlling kimberlite magmatism and add to a growing body of work linking periods of tectonic upheaval to kimberlite production. The implications of this extend to our broader understanding of intraplate magmatism and warrant a global revaluation of similar phenomena.

How to cite: Peace, A. and Foulger, G.: Beyond the Jurassic Corridor: Exploring North American Kimberlites and their relationship to plate tectonics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1799, https://doi.org/10.5194/egusphere-egu24-1799, 2024.

EGU24-3168 | ECS | Orals | GD1.2

Oceanic remnants in the mantle of the Parana Basin, Central South Atlantic: supporting the large-scale geochemical anomaly in the Northern Parana-Etendeka LIP 

Luizemara Szameitat, Monica Heilbron, Alessandra Bongiolo, Otavio Licht, Maria Alice Aragão, and Francisco Ferreira

The Parana Basin is one of the larger continental Paleozoic basin in Central South America. Although several studies investigated the flooring mantle of the Parana Basin, mantle-scale oceanic relicts have not been interpreted by previous regional geophysical studies. For this work, we used the global-scale tomographic model of P-wave velocity perturbation UU-P07 for mapping slab-like anomalies, and qualitative gravity and magnetic anomalies for indicating orogenic trends. Positive P-wave anomalies were mapped along fifty-two profiles, and revealed slab-like anomalies (long and segmented tabular mantle bodies), and four top slab surfaces (S1, S2, S3 and S4). The biggest anomalous mantle body (top surface S1) is transversal to the central-southern Brasilia Belt trending, and therefore it can be directly linked to the Southern São Francisco craton. However, the other three slab-like tabular bodies cannot be linked to outcropping orogenic trends, due to the extensive and thick sedimentary cover of the Parana Basin. Southwestern São Francisco Craton, elongated bodies coincide with Brazilian/Pan-African island arc collisions (top surface S2), but other possible slabs (top surfaces S3 and S4) are underneath Paraná Basin. Positive anomalies in the residual geoid anomalies (XGM2019e_2159 model) and transformed total magnetic field (vertical integration) follow the possible accretionary trend formed by S2, S3 and S4. Although the assumptions about the origin of these slab-like anomalies need to be investigated further, all these observations have shown the high complexity of the upper mantle beneath Parana floods. Facing the geophysical anomalies, we realize that the mapped slab-like bodies are mostly located under the Central-Northern Parana Basin, where several studies interpreted the existence of remnants of Proterozoic subductions in the mantle. Previous geochemical analysis had linked the high-Ti domain in the Central-Northern Parana floods with the partial melting of oceanic subduction relics. Nonetheless, the abundance of other incompatible elements (e.g., P, F and B) in the early phase of Central-Northern basaltic floods can be inherited from subduction remnants in the mantle. The remarkable early enrichment contrasts with the primitive mantle affinity in tholeiitic magmas of the relative late northern floods of the Parana Basin, the southern floods of the Parana Basin, the Etendeka counterpart, and the continental margins. In agreement with the previous understanding of the chemical evolution, we consider that the early magmatic phase was highly influenced by subcontinental subduction relicts. On the other hand, the advancing lithospheric embrittlement, due to the Atlantic opening process, intensified the rise of primitive fluids. Therefore, geophysical observations support the hypothesis of the existence of oceanic remnants from oceanic closure southern São Francisco Craton, due to the Western Gondwana’s assembly. The location of highly preserved oceanic-like mantle bodies supports the occurrence of enriched magmas in the early magmatic phase of the Northern Parana-Etendeka LIP.

How to cite: Szameitat, L., Heilbron, M., Bongiolo, A., Licht, O., Aragão, M. A., and Ferreira, F.: Oceanic remnants in the mantle of the Parana Basin, Central South Atlantic: supporting the large-scale geochemical anomaly in the Northern Parana-Etendeka LIP, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3168, https://doi.org/10.5194/egusphere-egu24-3168, 2024.

EGU24-4616 | Orals | GD1.2

Understanding Seamount Genesis: Utilizing Gaussian Process Regression and Clustering for Morphological Analysis 

Yanghui Zhao, Bryan Riel, Hanghang Ding, and Dazhen Deng

Seamounts are theorized to originate from deep mantle plumes or shallow, plate-related activities. The mantle plume hypothesis suggests that abnormally hot materials rise from the lowermost mantle and produce large volumes of volcanism on the surface. However, the accuracy of morphological analysis and volume estimation is highly influenced by the representation accuracy of irregularly shaped seamounts and the extent to which thick sediment coverage obscures their bases. As a result, the precise contribution of magma from mantle plumes to surface volcanism remains unclear.

Our study introduces a novel approach using Gaussian Process Regression to reconstruct the complex topography of seamounts, both above and beneath sedimentary covers. This approach advances previous analyses by (1) taking account of irregular seamount topography and (2) correcting for the varying sediment thicknesses that obscure seamount bases. Our investigation yields two principal findings.

1. Refined Volcanism Distribution Mapping

Analysis in the Pacific Ocean indicates that only 18% of total intraplate volcanic activity is attributable to plume-related volcanism. In addition, the volume statistics of plume-related seamounts and those along the Large Low-Shear-Velocity Province margins show no significant distinction from those of other intraplate seamounts. These results suggest that proposed plumes account for only a minority of the volume of intraplate volcanism in the Pacific plate, and that shallow rather than deep processes are dominant.

Along the volcanic Kyushu-Palau Ridge, high seamount volumes are observed near lithospheric weak zones, implying that tectonic inheritance significantly influences magma distribution during volcanic arc formation.

2. Comprehensive Morphological Analysis

Employing machine learning clustering analysis on high-resolution multibeam bathymetry data, we categorize seamounts in the South China Sea basin into three distinct morphological types: Type I, large seamounts with steep slopes and rounded bases, predominantly located along extinct ridges; Type II, linear seamounts characterized by gentler slopes, situated along ridges; and Type III, smaller, elliptically-based seamounts found along transform faults or off-ridge areas. This morphological classification provides a novel quantitative framework correlating seamount shapes with their tectonic environments during volcanic activity.

Overall, this research advances our understanding of seamount genesis, highlighting the importance of shallow tectonic processes in shaping submarine volcanic landscapes.

How to cite: Zhao, Y., Riel, B., Ding, H., and Deng, D.: Understanding Seamount Genesis: Utilizing Gaussian Process Regression and Clustering for Morphological Analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4616, https://doi.org/10.5194/egusphere-egu24-4616, 2024.

EGU24-6451 | ECS | Posters on site | GD1.2

Modeling seismic wave propagation across complex volcanic structures of the Hawaii-Emperor Ridge 

Megumi Fujimoto, Robert Dunn, and Chong Xu

Volcanic seamount chains are widespread throughout ocean basins, but their formation and structure are not well understood. Active-source refraction seismology can provide images of the interiors of these volcanoes via P wave travel time tomography, but that requires proper identification of seismic phases that are generated by and propagate across complex volcanic structures. Unfortunately, the current limitation on the number of seismic phases that can be included in tomographic analyses leads to less detailed images and a limited geological understanding of the structures being imaged. The primary objective of this study is to compare recorded seismic wavefields from recent surveys across the Hawaiian-Emperor Seamount Chain with synthetic wavefields generated through waveform modeling. We use simplified yet realistic models of volcanic edifices, the underlying oceanic crust, and the mantle to better understand observed seismic phases and their origins. In previous studies (Dunn et al., 2019; Watts et al., 2021; Xu et al., 2022; MacGregor et al., 2023), several seismic phases were identified in recorded sections along the Hawaiian-Emperor Chain. However, interpreting the origins of some of these phases remains challenging. In this study, we developed an idealized seamount model based on the seismic structure of Jimmu Guyot in the Emperor Ridge (Xu et al., 2022). We calculated the seismic P-SV wavefield for various source and receiver positions using a finite difference wavefield modeling code (Levander, 1988; Lata and Dunn, 2020). Our goal is to model the observed seismograms and identify additional phases, including P-to-S converted waves. Additionally, we aim to verify recent tomographic images of the Hawaiian-Emperor Seamount Chain created by P wave travel time inversion via wavefield comparison. By resolving ambiguities and pinpointing new seismic phases, our aim is to improve seismic images of the Hawaiian-Emperor Chain. This contribution will enhance our understanding of specific structures, such as volcanic cores (a high-density and high-wave-speed interior core of the seamount), the hypothesized magmatic underplating of the oceanic crust by mantle melts rising beneath the volcanic chain, and the nature of the Moho and upper oceanic crust beneath these volcanic edifices.

How to cite: Fujimoto, M., Dunn, R., and Xu, C.: Modeling seismic wave propagation across complex volcanic structures of the Hawaii-Emperor Ridge, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6451, https://doi.org/10.5194/egusphere-egu24-6451, 2024.

EGU24-7314 | Posters on site | GD1.2

An ongoing lithospheric dripping process beneath Northeast China and its impact on intraplate volcanism 

Feiyu Lin, Liang Qi, Nan Zhang, and Zhen Guo

Unique intraplate volcano eruptions and westward volcano migration since the Oligocene are observed in NE China, an overriding continental zone tectonically controlled by the subduction of the northwestern Pacific plate and the opening of Japan Sea. Interestingly, these intraplate magmatic events occur around a subsiding basin (the Songliao Basin), but no volcanic activities have been observed within the Songliao Basin. The geodynamic mechanism responsible for these volcanoes remains unclear. To address the geodynamic process beneath NE China, numerical experiments are conducted constrained by datasets from regional reconstruction, seismic and volcanic studies. Vertical velocity field of mantle convection and lithospheric partial melting structures yielded from our numerical model show mantle upwelling and melting center migrates from the east to the west of NE China with the westward propagation of the stagnant slab, leading to the volcano migration. Also, with the subduction retreat of NW Pacific plate and the opening of the Japan Sea, significant lithospheric thickness differences between Changbaishan-Mudanjiang Region and the Songliao Basin develop, leading to lithospheric unstable dripping. This dripping structure prevents the partial melting of the lithosphere but facilitates the subsidence of the Songliao Basin in central NE China. Moreover,  the lithospheric dripping model successfully predicts upper mantle structures consistent with the proposed tomography model, the observed Moho depth, and surface topography variations. Thus, the lithospheric dripping induced by lithospheric thickness difference and the subduction of the Pacific slab provides a robust mechanism for the unique geodynamic process in NE China.

How to cite: Lin, F., Qi, L., Zhang, N., and Guo, Z.: An ongoing lithospheric dripping process beneath Northeast China and its impact on intraplate volcanism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7314, https://doi.org/10.5194/egusphere-egu24-7314, 2024.

The Great Meteor Seamount is a guyot and the largest seamount in the North Atlantic Ocean with an estimated volume of some 24,000 km3. Located ~1280 km west of Africa and ~720 km south of the Azores, the seamount forms part of a group of seamounts which include Hyeres, Irving, Cruiser, Plato, Atlantis, and Tyro. Previous dredged rock, magnetic anomaly lineation, and predicted hotspot track studies suggest the seamount is ~17 Myr in age, was emplaced on oceanic crust and lithosphere with a thermal age of ~68 Ma and is linked to the New England Seamount Chain. However, bathymetric, free-air gravity anomaly and geochemical data are inconsistent with these ages and such a tectonic setting: bathymetric data suggest a guyot depth of ~400 m which is deeper than expected (~187 m), gravity data suggest an effective elastic thickness, Te, of ~20 km which is lower than expected (~26 km) and geochemical data suggest a link, not to the New England Seamount Chain, but to the Azores Islands instead. To address these inconsistencies, we used legacy Ocean Bottom Hydrophone, free-air gravity anomaly and bathymetry data to reassess the seismic structure, Te, and tectonic evolution of Great Meteor Seamount and its neighbouring seamounts. We show the uppermost crustal structure of Great Meteor Seamount is characterised by a relatively low velocity volcano-clastic sediments (2.0-4.5 km/s) and extrusive lava (5.0-6.0 km/s) drape which overlies a relatively high P-wave velocity intrusive ‘core’ of 6.0-6.5 km/s. The lowermost crust, in contrast, is characterized by a 4-km-thick body of P-wave velocity 7.00-7.75 km/s intermediate in velocity between the crust and mantle, the base of which is at depths at ~16 km. This seismic structure has been verified by gravity modelling assuming a Gardner and Nafe-Drake relationship between P-wave velocity and density, but 3-D flexure modelling reveals that a Moho depth at ~16 km requires a low elastic thickness (Te ~10 km) which is inconsistent with the amplitude and wavelength of the free-air gravity anomaly and the relatively flat depth to the top of the oceanic crust beneath the flexural moats flanking the guyot ‘core’. We found that gravity and seismic data are consistent if the Te of flexed oceanic crust at Great Meteor Seamount is ~20 km and is underlain by a ~4-km-thick magmatic underplated body. In contrast, we found that the Irving, Cruiser, Plato, Atlantis, and Tyro seamounts are characterised by a best fit Te of ~10 km and no evidence of underplating. We discuss these findings here with respect to the guyot depth at Great Meteor, terrace depths at Plato, and the tectonic setting of Great Meteor and its neighbouring seamounts.

How to cite: Watts, A. and Grevemeyer, I.: Legacy seismic refraction and gravity anomaly data in the vicinity of Great Meteor Seamount and its implications for plate flexure , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11610, https://doi.org/10.5194/egusphere-egu24-11610, 2024.

EGU24-11775 | Posters on site | GD1.2

TRANSCAUCASUS: Record of 200 My plume activity 

Nino Sadradze, Shota Adamia, Sierd Cloetingh, Alexander Koptev, and Guga Sadradze

Transcaucasus - the westernmost part of the southern Caucasus, represents an area where the Tethys Ocean was closed in the Late Cenozoic because of Eurasian and Africa-Arabian plate convergence. The lithosphere of the region represents a collage of Tethyan, Eurasian, and Gondwanan terranes. During the Late Proterozoic–Early Cenozoic a system of island arc and back-arc basins existed within the convergence zone. Geological and palaeogeographical data supported by paleomagnetic studies indicate the presence of several tectonic units in the regions that have distinctive geological histories.

The region comprises a 30-55 km thick continental crust with significant lateral variations in thickness of the overlying sediments (0-25 km). The travel times velocity anomalies of the P- and S-waves are interpreted as high-velocity bodies down to about 100 km depth, where the mantle lithosphere is thin or even missing.

The Mesozoic-Cenozoic magmatic assemblages reflect a diversity of paleogeographic -paleotectonic environments. They are indicative of a west Pacific-type oceanic basin setting under which the mature continental North Transcaucasian arc developed with zones of rifting and alkaline basaltic volcanism on the active margins of the oceanic domain.

Within-plate magmatic activity in the North Transcaucasus is represented by volcanic and plutonic complexes, including Late Triassic to Early Jurassic subaerial alkali basalts and alkali gabbro; the Late Bathonian-Late Jurassic high titanium alkali basalts and minor trachytes with coal-bearing shales and evaporites intercalations; Albian alkali basalts alternating with redeposited volcaniclastics and shallow marine carbonates.

The Late Cretaceous volcanics are associated with intraplate-type titanium rich alkali basalts and basanites with minor trachytes and phonolites, while the Eocene volcanics are associated with highly potassic to ultrapotassic basalts and basanites. The Late Miocene-Pleistocene volcanism is represented by alkaline basalt-trachytes as well.

The Great Caucasus, a NW–SE-directed mountain range, extends westwards along the pre-Caucasian strip of the Eastern Black Sea and is bounded to the south by the Transcaucasian Massif. The shoreline of the Eastern Black Sea Basin cuts off the Colchis intermontane trough formed over the rigid Georgian Block, the Achara–Trialeti trough and the Artvin–Bolnisi rigid block.

Onshore and offshore data confirm that the subaerial structures have immediate submarine prolongations. Deep drilling conducted within the onshore zone of the Transcaucasus, in the immediate vicinity of the shoreline, revealed that the volcanic formations below the modern sea level extend further into the Eastern Black Sea basin.

Recent data on structure and evolution of the Transcaucasus and adjacent area provide new constraints on the geological history of the lithosphere of the region, particularly on the Eastern Black Sea basin located in the collision zone between Eurasian and Africa-Arabian lithosphere plates, proximal to ancient sutures.

How to cite: Sadradze, N., Adamia, S., Cloetingh, S., Koptev, A., and Sadradze, G.: TRANSCAUCASUS: Record of 200 My plume activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11775, https://doi.org/10.5194/egusphere-egu24-11775, 2024.

EGU24-12578 | Posters on site | GD1.2

The influence of the lithosphere on deep-origin volcanism 

Lara M Kalnins, Amelia K Douglas, Benjamin E Cohen, J Godfrey Fitton, and Darren F Mark

Eastern Australia and the neighbouring Tasman and Coral Seas are home to extensive age-progressive volcanism spanning from ~55 Ma in the north to ~6 Ma in the south. This volcanism forms two offshore seamount trails, the Lord Howe and the Tasmantid Chains, as well as the onshore central volcanoes and leucitites of the East Australian Chain. The three volcanic chains are an average of just 500 km apart, erupted contemporaneously from 35-6 Ma, and share a common age-distance relationship, strongly suggesting a common source, most likely a deep-origin plume. However, they have erupted through lithosphere ranging from oceanic with well-developed seafloor spreading to drowned continental fragments to mainland Australia. How do these diverse settings influence the chemical and physical properties of the resulting mafic volcanism? The East Australian Chain has more fractionated mafic samples, reflecting more complex magmatic plumbing and longer magma residence times in the thick continental lithosphere. However, the most striking result is that the trace element and isotopic ratios remain remarkably similar across the three suites, showing little evidence of crustal or lithospheric assimilation affecting the mafic magmas. 

How to cite: Kalnins, L. M., Douglas, A. K., Cohen, B. E., Fitton, J. G., and Mark, D. F.: The influence of the lithosphere on deep-origin volcanism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12578, https://doi.org/10.5194/egusphere-egu24-12578, 2024.

EGU24-12916 | ECS | Posters on site | GD1.2

First insights into the geochemical and petrological features of the Eger Rift’s plumbing system (Czech Republic) 

Kyriaki Daskalopoulou, Samuel Niedermann, Franziska D.H. Wilke, Martin Martin, and Heiko Woith

The western Eger Rift (Czech Republic) is a non-volcanic rift setting of intraplate seismicity that is characterized by abundant degassing of mantle-derived fluids. Since 2019, gases obtained from the free gas phase and volcanic rock samples of Quaternary age have been collected in order to determine the origin and evolution of volatiles in the system and define the magma chamber p-T conditions. Results of the CO2-dominated gas discharges of the Bublák and Hartoušov mofette fields yield an ~93 % mantle input (considering a subcontinental lithospheric mantle) for He. Ne isotopic ratios range from 9.8 to 11.0 for 20Ne/22Ne and from 0.0282 to 0.0480 for 21Ne/22Ne. Notwithstanding the samples enriched in 20Ne likely due to mass fractionation, many samples show a mixed atmospheric-mantle type source for Ne. However, an additional crustal input cannot be excluded. 40Ar/36Ar ratios also cover a wide spectrum of values (between 300 and 4680). Overall, gas samples typically present a higher-than-atmospheric value with 40Ar likely deriving from the mixing of an atmospheric and deep source. The 4He/40Ar* ratio is moderately constant and falls within the MORB range, suggesting an unfractionated magma that originates from mantle sources.. Results obtained from mineral quantitative analyses and by using thermobarometry of orthopyroxene and clinopyroxene rim pairs of matrix grains yield predominantly temperature and pressure conditions of 700 ±100 °C and 1.1 ±0.5 GPa, respectively, indicating a lithospheric depth that ranges between 40 - 45 km for 1.5 GPa and 20-25km for 0.5 GPa. In addition, pairing cores of mm-sized pyroxenes point to a temperature of 1100 ±100 °C and a pressure of 2.5 ±0.5 GPa that correspond to a lithospheric depth of ~75 km. Those minerals that indicate greater depths are likely the oldest ones as they were able to grow for longer times during their ascent. On the other hand, secondary overgrowths or smaller matrix grains represent younger grains that have grown during magma evolution. Therefore, their diverse chemistry and the wide range of p-T conditions reveal rising (and cooling) of magma.

This research is a part of the “MoRe-Mofette Research” and MoCa - “Monitoring Carbon” projects, which were funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 419880416, 461419881.

How to cite: Daskalopoulou, K., Niedermann, S., Wilke, F. D. H., Martin, M., and Woith, H.: First insights into the geochemical and petrological features of the Eger Rift’s plumbing system (Czech Republic), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12916, https://doi.org/10.5194/egusphere-egu24-12916, 2024.

EGU24-13068 | ECS | Orals | GD1.2

Intraplate magmatism, serpentinization and hydrothermal venting in the ultra-slow spreading setting of the Eurasia Basin, Arctic Ocean 

Juan Camilo Meza, Jan Inge Faleide, Alexander Minakov, and Carmen Gaina

The Eurasia Basin, one of two major oceanic basins of the Arctic Ocean, is composed of the Amundsen and Nansen basins, which were created due to the slow and ultra-slow seafloor spreading at the mid-oceanic Gakkel Ridge initiated during the Paleocene-Eocene transition (53-56 Ma). Since the beginning of the current millennia the Gakkel Ridge and the Eurasia Basin have been subject of marine geological and geophysical studies leading to the collection of diverse datasets including rock samples, seismic, and potential-field datasets. New marine seismic data has become available in the western Eurasia Basin in the very last years, including data acquired by the Norwegian Petroleum Directorate in the context of the UN Law of the Sea, together with seismic lines gathered by Norwegian research institutions and partners. During October-November 2022 the first High Arctic GoNorth marine expedition collected new seismic reflection and refraction, as well as gravity and magnetic datasets. It is considered that this polar region may hold important clues for the understanding of global processes such as passive margin formation, and the complex links between plate tectonics and climate. Volcanic additions have been suggested within the flanks of the Eurasia Basin during different stages in the Cenozoic. Existing hypotheses further postulate corridors of exhumed mantle formed across the western Eurasia Basin because of the magmatic segmentation imposed by the Gakkel Ridge. Consequently, the oceanic basement of this area should be prone to deformation, hydrothermal alteration and serpentinization. However, little is known about the relationships between such processes with the sedimentary units above, or whether such processes occur away from the ridge and to what extent.

The new compilation of multi-channel seismic reflection profiles provides an image of the sedimentary structure and the upper crust, within the oceanic crust and the continent-ocean transition (COT) between northern Svalbard margin and Eurasia Basin. The preliminary analysis of these datasets indicates that the sediments and basement structures within the southwestern corner of the Eurasia Basin have been modified in a unique manner due to an underlying geothermal anomaly beneath the lithosphere. This is expressed as focused late Miocene (< 20 Ma) to recent sill intrusion events resulting in basement and sediment deformation, and intense hydrothermal and sediment evacuation features. We present unique examples of hydrothermal venting on seismic reflection data and discuss implications of the post-rift NE Atlantic and Arctic setting, including the role of breakup magmatism, post-breakup intraplate volcanism, and sheared/passive margin development during the Cenozoic.

How to cite: Meza, J. C., Faleide, J. I., Minakov, A., and Gaina, C.: Intraplate magmatism, serpentinization and hydrothermal venting in the ultra-slow spreading setting of the Eurasia Basin, Arctic Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13068, https://doi.org/10.5194/egusphere-egu24-13068, 2024.

EGU24-13901 | Posters on site | GD1.2

Seismic Silence Speaks Loud: No extensive magmatic underplating found in recent seismic studies of the Hawaiian Ridge 

Robert Dunn, Megumi Fujimoto, Chong Xu, Anthony Watts, Brian Boston, and Donna Shillington

Some prior active-source seismic studies beneath oceanic seamount chains indicate a sub-crustal layer of what is considered to be underplated magmatic material. The classic example is the Hawaiian Ridge, where a seismic study in the early 1980s first proposed the existence of such a layer. Since then, Hawaii has been considered one end-member in a range of possible scenarios, extending from underplating to no underplating, but with possible magmatic intrusion into the lower oceanic crust. Magmatic underplating affects mass flux and lithospheric loading calculations. All else being equal, underplating would be expected to lower the amplitude of the gravity anomaly over the crest of the edifice and provide a positive buoyancy force that makes the plate appear more rigid than it actually is. One hypothesis put forward to explain variations in the style of magmatic emplacement at intraplate volcanoes hinges on the age of the lithosphere at the time of volcano formation. In this model, shallow intrusion into the oceanic crust and overlying edifice is favored for seamounts growing on younger lithosphere, while magmatic underplating is favored for seamounts growing on older lithosphere such as Hawaii. However, recent seismic, gravity, and plate flexure studies conducted along the Hawaiian-Emperor Seamount Chain collectively provide clear evidence for shallow magmatic emplacement and contradict the notion of significant magmatic underplating for ages at the time of loading of ~57 Ma (Emperor Seamounts) and ~90 Ma (Hawaiian Ridge). Additionally, reprocessed legacy seismic data has not revealed evidence for underplating beneath the Hawaiian Ridge. In this presentation, results from these recent studies will be shown, compared, and the evidence for a simple mantle structure without underplating will be presented along with seismic synthetic tests that explore the degree of underplating that may be 'hidden' in the data.

How to cite: Dunn, R., Fujimoto, M., Xu, C., Watts, A., Boston, B., and Shillington, D.: Seismic Silence Speaks Loud: No extensive magmatic underplating found in recent seismic studies of the Hawaiian Ridge, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13901, https://doi.org/10.5194/egusphere-egu24-13901, 2024.

EGU24-13934 | ECS | Orals | GD1.2

Bulldoze and rebuild: Modifying cratonic lithosphere via removal and replacement induced by continental subduction 

Lingtong Meng, Chu Yang, Wei Lin, Ross N. Mitchell, and Liang Zhao

Establishing the mechanisms for craton modification is critical for understanding cratonic stability and architecture. Cratons are intrinsically strong with long-term stability, but plate tectonics or mantle plumes cause craton weakening, mechanical decoupling, and lithospheric removal. By comparison, craton modification—craton destruction accompanied or followed by rejuvenation—has received less attention. Oceanic plate subduction dominantly destroys the craton, with a lesser degree of rebuilding. Mantle plumes can facilitate decratonization, by weakening and peeling off the lithospheric mantle, or recratonization, by healing the craton with refractory mantle residues. Compared with the effects of oceanic plate subduction and mantle plumes, the role of continental subduction in craton modification remains an open question. The North China Craton (NCC), a previously stable continent with a lithospheric thickness of >200 km since the Paleoproterozoic, was reworked and partially destroyed due to lithospheric delamination triggered by Early Cretaceous Paleo-Pacific oceanic subduction. In eastern NCC, lithospheric thickness decreased from 200 km to 35 km in the Early Cretaceous in only 10 m.y. The NCC experienced an early Mesozoic continent–continent collision (as the overriding plate) with the South China Block (SCB). The collision provides an opportunity to understand the potential for craton modification due to deep continental subduction induced by continental collision.

In the NCC, combined structural geology, magnetic fabrics, zircon U-Pb dating, and Hf-O isotopes, we report the presence of martial derived from a partially melted SCB’s crust. We proposed a three-stage model to interpret the material sourced from the subducted plate into the overriding carton: (1) SCB bulldozed and rebuilt NCC during 250–220 Ma; (2) during 220-200 Ma, the subducted SCB exhumed along the exhumation channel to underplate beneath the NCC, associated with partial melting; (3) finally, Late Jurassic granite derived partial melting of the SCB entrained Latest Triassic reworked SCB’s crust to emplace.

Combining our new results with previous geophysical observations, we estimate the extent of the bulldozing and rebuilding. We argue that a 200-km-long tract of the NCC lithosphere was bulldozed and rebuilt by the subducted SCB, resulting in a lithospheric suture far from the suture zone at the surface. This lithospheric removal occurred at middle-lower crustal levels (16–20 km depth)—much shallower than previously thought possible. The bulldozed NCC lithosphere was replenished by the subducted SCB continental lithosphere rather than the asthenosphere, thus terminating the lithosphere modification. With essentially no net loss of lithosphere during deep continental subduction, the NCC maintained its stability until Early Cretaceous paleo-Pacific oceanic subduction. This “bulldoze and rebuild” model can thus account for how a craton maintains its stability during a collision with another continental plate.

How to cite: Meng, L., Yang, C., Lin, W., Mitchell, R. N., and Zhao, L.: Bulldoze and rebuild: Modifying cratonic lithosphere via removal and replacement induced by continental subduction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13934, https://doi.org/10.5194/egusphere-egu24-13934, 2024.

Mesozoic intraplate igneous activity is abundant on the Canadian shield and includes multiple kimberlite fields, a province of alkaline magmatism, and individual bodies of kimberlites and ultramafic lamprophyres. Models have variously attributed the emplacement of these intrusions to the influence of Farallon plate subduction, opening of the Atlantic Ocean, or one or several Atlantic hotspots which North American plate is postulated to have drifted over during the Mesozoic. The latter hypothesis relies of the attribution of spatially, temporally and compositionally distributed and diverse magmatic rocks into a poorly defined, age-progressive, ‘corridor’ which may be derived from a common geochemical reservoir. In this study, we aim to test the spatiotemporal association between intraplate igneous activity along this postulated Triassic-Jurassic corridor and several elements of fixed mantle reference frame, such as the Atlantic hotspots and the hypothesised plume-generating zone (PGZ) of the African Large Low Shear Velocity province (LLSVP).

We use published geochronological databases containing locations and isotopic ages of the Mesozoic intrusions of North America and published global plate reconstructions to dynamically calculate distances between the loci of intraplate magmatism and features of the upper and lower mantle assuming the latter remained fixed in the mantle reference frame throughout their history. We use GPlates 2.3.0 software package and pygplates 0.36.0 Python library to build the reconstructions and implement our calculations.

Results demonstrate that none of the examined mantle features show a consistent association with all instances of intraplate magmatism across the Canadian shield during the Triassic-Jurassic. The coeval kimberlitic magmatism in the western Slave province (Jericho kimberlite field) and Baffin Island (Chidliak kimberlite field) appears to be completely spatially unrelated to any of the examined mantle features. The kimberlite fields of the Superior province (Attawapiskat, Kirkland Lake, Timiskaming) experience emplacements long before and after their passage over the PGZ, but their frequency increases in the PGZ’s vicinity, i.e. 76% of emplacement events in these provinces occur within 200 km of the PGZ’s surface projection.

Our results show that intraplate magmatism across many Triassic-Jurassic fields of North America could be initiated independently of the influence of deep mantle structures. Thereby, a geodynamic mechanism nested in the asthenosphere or lithospheric mantle suffices for melt generation in an intraplate setting. However, it cannot be ruled out whether proximity to deep mantle structures is capable of facilitating “shallow” melt generation and emplacement and that deep-seated mantle structures could provide an influx of fluids or thermal energy, increasing melting intensity and volume.

How to cite: Koptev, E. and Peace, A.: The Triassic-Jurassic corridor of North America: are deep mantle structures a sufficient explanation for intracontinental magmatism?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14228, https://doi.org/10.5194/egusphere-egu24-14228, 2024.

EGU24-14365 | ECS | Orals | GD1.2

Intraplate Volcanism by Spontaneous Shallow Upper Mantle Melt Focusing 

Jung-Hun Song, Seongryong Kim, Junkee Rhie, and Tae-Seob Kang

Intraplate volcanism signifies persistent magmatic activity within plate interiors far from active plate boundaries. However, due to limited assessment of the detailed physical conditions of the intraplate upper mantle, the fundamental mechanism behind the genesis of mantle magma remains poorly understood. We analyzed the temperature conditions of the upper mantle beneath global intraplate volcanic regions estimated from seismic velocity and geochemical data. We revealed that excluding volcanoes near major plumes, large proportions (> 70%) of the volcanoes are situated above the upper mantle with moderate temperatures comparable to or colder than those found at mid-oceanic ridges (potential temperature (Tp) ~1250–1350°C). These volcanoes also overlie regions of low vertical and horizontal asthenospheric shear estimated by global mantle convection simulations. Without peculiarities in thermal and large-scale mantle dynamics, we inferred that these volcanic activities are likely driven by a small-scale local convective process confined to the shallow upper mantle. To constrain a more detailed process of intraplate volcanism, we focus on analyzing the upper mantle rheology and melt distribution beneath intraplate volcanoes in NE Asia. Thermodynamic properties, conservatively constrained by high-frequency seismic attenuation and velocities, revealed the common presence of low-viscosity zones concentrated beneath the volcanoes at shallow asthenospheric depths (< 200 km). These regions contain a small fraction of melt (~0.05–0.8%) at cold-to-moderate temperatures (Tp ~1300–1350°C) compared to the average mantle aligning with global analyses. A series of evidence potentially suggests the existence of localized mantle upflux focused beneath intraplate volcanoes. Considering the amount and extent of the estimated mantle melts and numerical mantle convection simulations with lithospheric structures, we propose that undulations in the lithosphere and asthenosphere boundary could play a primary role in controlling the small-scale mantle convection and the location of intraplate mantle melting. Our estimation supports the possibility of the ubiquitous occurrence of intraplate volcanoes independent of dynamic forces for deriving active mantle upwellings (e.g., thermal or chemical buoyancy).

How to cite: Song, J.-H., Kim, S., Rhie, J., and Kang, T.-S.: Intraplate Volcanism by Spontaneous Shallow Upper Mantle Melt Focusing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14365, https://doi.org/10.5194/egusphere-egu24-14365, 2024.

EGU24-14871 | Orals | GD1.2

Santiago Island, Cape Verde: Evidence for island-scale collapse from paleotopography onshore and bathymetry offshore 

Fernando Ornelas Marques, Cristina Catita, Anthony Watts, Anthony Hildenbrand, and Sónia Victória

A volcanic edifice much larger than the current one must have existed in Santiago Island, Cape Verde, because the granular rocks and dyke-in-dyke complex representing magma chambers and deep feeders currently outcrop up to 700 m altitude. Therefore, we must find an explanation for the massive destruction of the original edifice. We developed a new tool for the quantitative reconstruction of ancient topographies in a volcanic ocean island to address this problem, because it allows us to estimate the shape and volume of volcanic rock removed at a certain time. The reconstruction of the topography of the basement complex at ca. 6 Ma ago, before the unconformable deposition of the submarine complex, shows a concave depression coincident with the asymmetric distribution of volcanic complexes east and west of the main divide of the island. This concave depression is here interpreted as the remnant of an island-scale, summit collapse. Instituto do Mar de Cabo Verde bathymetry and RRS Charles Darwin (8/85) seismic reflection profile data suggest that the west side of Santiago is characterised by a narrow insular shelf, a major debris avalanche deposit with scattered blocks and at least one lateral sector collapse structure. Data, however, east of Santiago are limited and so the full extent of mass wasting on the east side of the island is not known. Maio Island, which is similar in age to Santiago, would have acted as a buttress in the east, and it is possible that any eastward collapse might have rotated and travelled to the northeast. Irrespective, one or more mass wasting events west or east of Santiago are consistent with a major destruction of the original volcano edifice which removed the summit, exposed the basement complex of the island, and redistributed volcano-clastic material over a large area of the adjacent seafloor. 

How to cite: Ornelas Marques, F., Catita, C., Watts, A., Hildenbrand, A., and Victória, S.: Santiago Island, Cape Verde: Evidence for island-scale collapse from paleotopography onshore and bathymetry offshore, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14871, https://doi.org/10.5194/egusphere-egu24-14871, 2024.

The Eifel volcanic area in western Germany has been active for tens of million years. Geodetic observations, geochemical analysis and seismological studies all indicate that the source of these long-term volcanic activities is a mantle plume. However, it still remains controversial whether the Eifel plume has a deep origin. This is because the tomography images do not consistently show a continuous plume conduit between the surface and the core-mantle boundary. The Eifel plume is also not associated with any flood basalt province or a clearly age-progressive hotspot track, which is regarded as a key surface feature indicating a deep plume origin. In addition, it has been proposed that the Alpine subduction zone, south-east of the volcanic area, has created a stagnant slab in the mantle transition zone, which might be interacting with the Eifel plume.

Based on the previous studies and observations, our two contrasting hypotheses are as follows: (1) The Eifel plume is not rooted in the lower mantle. In this case, subduction beneath the Alps might trigger a return asthenospheric flow and the ascent of an upper-mantle plume, leading to the formation of intraplate volcanism beneath the European plate. (2) The Eifel plume is assisted from an upwelling in the lower mantle. In this case, the subducting plate might tilt the plume conduit and influence the position where volcanism takes place.

In this study, we apply the Finite-Element-Method geodynamic modeling code ASPECT to model the ascent of the Eifel plume and its interaction with the subducting slab. We design both slab advancing and slab retreating model set-ups, with and without a plume from the lower mantle beneath the subducting plate. We check whether and under what conditions the Eifel plume will be triggered behind the slab due to slab overturn. Preliminary results show that the return flow induced by subduction can help generate an upper-mantle plume and lead to the formation of volcanism. A series of models are also performed to investigate the effects of mantle viscosity and plume temperature on the plume-slab interaction.

How to cite: Li, Y., Steinberger, B., Brune, S., and Le Breton, E.: Intra-plate volcanism generated by slab-plume interaction: Insights from geodynamic modeling of the Eifel plume and its interaction with the European subducting lithosphere beneath the Alpine subduction zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15020, https://doi.org/10.5194/egusphere-egu24-15020, 2024.

EGU24-15229 | ECS | Posters on site | GD1.2

3-D Modelling of Plume-Lithosphere Interaction: The Cosgrove Track, Eastern Australia 

Thomas Duvernay and D. Rhodri Davies

Compared to oceanic hotspot tracks, volcanic provinces within Earth's continents generally exhibit more intricate surface characteristics, such as spatio-temporal distribution and geochemical signatures of erupted lavas. These complex surface patterns relate to dynamic interactions in the uppermost convective layer of the mantle, where decompression melting occurs. The Cosgrove Track of Eastern Australia constitutes a compelling example of such continental volcanic activity. Recent studies support a mantle plume having sustained the volcanism and discuss several notable features, such as lithosphere-modulated volcanic activity, plume waning, separate volcanic tracks, and plate-motion change.

Here, we simulate the proposed interaction between the Cosgrove plume and eastern Australia during the past 35 Myr. We design a 3-D analogue of the Australian continent using available lithospheric architecture determined through seismic tomography and impose the inferred plate motion associated with this region. Our models incorporate updated peridotite melting and melt chemistry parameterisations that provide quantitative estimates of generated melt volume and composition. We find that plume-driven and shallow edge-driven melting processes, modulated by the lithospheric thickness of the Australian continent, combine to explain the observed volcanic record. Our preliminary results agree well with surface observations and provide further insight into the geodynamics of eastern Australia.

How to cite: Duvernay, T. and Davies, D. R.: 3-D Modelling of Plume-Lithosphere Interaction: The Cosgrove Track, Eastern Australia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15229, https://doi.org/10.5194/egusphere-egu24-15229, 2024.

EGU24-17719 | ECS | Posters on site | GD1.2

Petrology and geochemistry of alkaline Circular Complexes from Sal Island, Cape Verde archipelago. 

María García-Rodríguez, Cristina de Ignacio, David Orejana, Carlos Villaseca, João Mata, and Rita Caldeira

Sal is the oldest island of the Cape Verde archipelago, with magmatic activity starting around 25 Ma (Torres et al., 2010). Located to the northeast of the archipelago, it forms part of a north-south islands alignment and features intrusive bodies potentially representing the subvolcanic roots of exposed volcanic rocks. These intrusions, dated from ≈ 14 to 17 Ma (Torres et al., 2010) are intrusive into the Old Eruptive Complex, located in the central-western part of the island and mostly comprised by gabbro bodies, dyke swarms and several circular gabbro to monzonite complexes.

There are no previous detailed studies concerning mineral chemistry and crystallization conditions of these intrusions, which are a first step, together with precise geochronology, to correlate them with any of the different volcanic series occurring in Sal. In this work we present preliminary mineral chemistry, whole-rock geochemistry and radiogenic (Sr, Nd, Pb) isotope data of the circular complexes aiming to characterize their main features, magmatic evolution and mantle source composition.

The studied rocks range from gabbros to monzonites, sometimes displaying cumulate textures. The main mafic minerals present variable compositions: olivine chemistry ranges from Fo61-81 in gabbros to Fo39-49 in monzogabbros; clinopyroxene is classified as augite-diopside in all samples; amphibole is mainly kaersutite-pargasite-Mg-hastingsite and biotite-phlogopite Mg# is in the range 0.4-0.7. Plagioclase is bytownite-andesine (An30-86) in gabbros, whereas it is more sodic in monzogabbros and monzonites (An16-66), while nepheline (Ne70-86) turns more potassic from gabbros to monzonites. Alkali feldspar (Or20-98) only appears in monzogabros and monzonites. The main accessory phases are ilmenite/Ti-magnetite, chromite, ulvospinel, titanite and apatite.

Major and trace element chemistry points to a progressive evolution from mafic to intermediate types characterized by a linear decrease of MgO, TiO2, FeOT, CaO, Ni and Cr, and a gradual increase of SiO2, Al2O3, K2O, Na2O, Rb, Ba, Zr and Nb. These patterns suggest initial crystallization of mafic phases (olivine, clinopyroxene, ilmenite-magnetite) and calcic plagioclase. The intra-complexes positive correlation between strongly incompatible element pairs: U-Th, La-Ce and Nb-Ta, suggests the predominance of fractional crystallization within each circular complex.

The studied rocks display 87Sr/86Sr and 143Nd/144Nd initial ratios typical of some OIB having more Sr-radiogenic and Nd-unradiogenic compositions than the N-MORB. These signatures and the Pb isotope ratios are close to the FOZO composition, in an intermediate position between the HIMU and N-MORB mantle components. Small εNd and 206Pb/204Pb differences between the several circular complexes define two compositional groups, which implies slight heterogeneities in the mantle sources. These isotopic results support the association of Sal intrusive with the Cape Verde northern islands as no low Nd isotopic ratios have been found that could imply EM-1 enriched components, as those described by Torres et al. (2010) for some lavas.

Torres, P., Silva, L.C., Munhá, J., Caldeira, R., Mata, J., Tassinari, C. (2010): Petrology and geochemistry of lavas from Sal Island: Implications for the variability of the Cape Verde magmatism. Comunicaçoes Geológicas, 97: 35-62.

How to cite: García-Rodríguez, M., de Ignacio, C., Orejana, D., Villaseca, C., Mata, J., and Caldeira, R.: Petrology and geochemistry of alkaline Circular Complexes from Sal Island, Cape Verde archipelago., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17719, https://doi.org/10.5194/egusphere-egu24-17719, 2024.

EGU24-18227 | ECS | Posters on site | GD1.2

A geodynamic perspective on the formation of intraplate volcanism in Central East Asia 

Alexander Rutson, Tiffany Barry, Stewart Fishwick, and Victoria Lane

Central East Asia has experienced intraplate volcanism over the past ~110 Myrs. The mechanism for this volcanism is enigmatic, with several potential causes put forward for the origin, including a mantle plume, edge convection, and lithospheric delamination. One of the big questions for the region is the role played by the long-term subducting systems of the Pacific/Izanagi and the Tethys Ocean(s). And secondarily, how much the volcanism is influenced by the lithospheric conditions and its changing thicknesses across the region.  

To recreate the conditions of mantle circulation and flow beneath Central East Asia, a mantle circulation model has been created using the fluid dynamics code ASPECT; the mantle circulation model is coupled with the plate reconstruction of Muller et al. (2019) for the surface conditions of the past 200 Myrs. To better understand the patterns of mantle flow, particles are emplaced into the model to track flow beneath the region, particularly around the subducted slabs. The mantle flow is compared to localities of intraplate volcanism across Central East Asia to assess whether any upwelling regions correlate with the spatial and temporal origins of the volcanism. Initial results show colder downwelling mantle from the surface boundary beneath Central East Asia at ~120-110 Ma, with warmer mantle upwelling into the region to replace it. The timing of this upwelling mantle coincides with the initiation of intraplate volcanism in the region; however, whether this results in the onset of intraplate volcanism in the region and the following 110 Myrs of intraplate volcanism is still being investigated. The mantle flow from the global models will then be used to inform the boundary conditions of a localised box model for Central East Asia. This model will be used to examine any potential effect of delamination beneath Central East Asia, and whether this model can explain any of the timings of intraplate volcanism formation. 

How to cite: Rutson, A., Barry, T., Fishwick, S., and Lane, V.: A geodynamic perspective on the formation of intraplate volcanism in Central East Asia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18227, https://doi.org/10.5194/egusphere-egu24-18227, 2024.

EGU24-18822 | ECS | Orals | GD1.2

Plate flexure and tectonic tilt along the Emperor Seamount Chain  

Chong Xu, Paul Wessel, Anthony Watts, Brian Boston, Robert Dunn, and Donna Shillington

The Hawaii-Emperor seamount chain stretches westward from the “Big Island” of Hawaii for over 6000 km until the oldest part of the chain are subducted at the Kuril and Aleutian trenches. Still regarded as the iconic hotspot-generated seamount chain it has been sampled, mapped, and studied to give insights into numerous oceanic phenomena, including seamount and volcano formation and associated intraplate magma budgets, the past absolute motions of the Pacific plate, the drift of the Hawaiian plume, and the thermal and mechanical properties of oceanic lithosphere. Previous work (Wessel et al., EGU 2023 abstract) used a high-resolution free-air gravity anomaly and high-resolution bathymetry data set, together with fully 3-dimensional flexural models with variable volcano load and infill densities, to estimate the optimal effective elastic thickness, Te, and load and infill densities along the Emperor Seamount chain. Here, we use these parameters to calculate the tectonic tilt of a pre-existing volcano that occurs as each new volcano in a seamount chain is progressively added by flexure to the Pacific oceanic plate. We found tilts in the range 0.1-2.1 degrees which are modest compared to other cases of progressive flexure, for example, at seaward dipping reflector sequences in volcanic rifted margins (~5-15 degrees) but may be significant enough to modify the morphology of volcano summits and the stratigraphy of the sequences that accumulate in their flanking moats. They may also modify the physical properties of the edifice such as their magnetisation vectors.

Wessel, P., A. B. Watts, B. Boston, C. Xu, R. Dunn, and D. J. Shillington “Variation in Elastic Thickness along the Emperor Seamount Chain”, EGU 2023 Abstract

How to cite: Xu, C., Wessel, P., Watts, A., Boston, B., Dunn, R., and Shillington, D.: Plate flexure and tectonic tilt along the Emperor Seamount Chain , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18822, https://doi.org/10.5194/egusphere-egu24-18822, 2024.

EGU24-19827 | Posters on site | GD1.2

Seamounts and giant carbonate mounds drive bio-physical connections in the deep-sea: Two case studies from the North Atlantic. 

Christian Mohn, Vibe Schourup-Kristensen, Janus Larsen, Franziska Schwarzkopf, Arne Biastoch, Inês Tojera, Miguel Souto, Manfred Kaufmann, Anna-Selma van der Kaaden, Karline Soetaert, and Dick van Oevelen

Seamounts and carbonate mounds are ubiquitous features of the global deep seascape. They often provide habitat for unique benthic species communities and support increased production and aggregation of phytoplankton, zooplankton, micronekton, and fish. Seamounts and carbonate mounds interact with the surrounding currents generating flow phenomena over a wide range of spatial and temporal scales including stable Taylor caps, energetic internal waves and turbulent mixing, all with the potential to enhance productivity, biomass, and biodiversity in an often food-limited deep-sea environment. We present hydrodynamic and ecological framework conditions at two contrasting topographic features in the North Atlantic, Great Meteor Seamount and Haas Mound. Great Meteor Seamount is of volcanic origin and one of the largest seamounts in the subtropical North Atlantic rising from 4200 m depth at the seafloor to a summit depth of 270 m. Great Meteor Seamount shows remarkable endemism in meiofaunal groups of copepods and nematodes. Haas Mound is one of the largest biogenic carbonate mounds of the Logachev mound province along the Southeast Rockall Bank in the Northeast Atlantic with a species rich benthic fauna dominated by the cold-water coral Desmophyllum pertusum (Lophelia pertusa). We used results from hydrodynamic models to identify the physical processes, which potentially support seamount and carbonate mound biodiversity. The models employ high-resolution local bathymetry, basin-scale lateral forcing and tidal forcing. Our model simulations provide a detailed three-dimensional picture of the fine-scale motions and physical processes, which potentially drive bio-physical connections such as particle retention and continuous or episodic food supply to benthic communities. 

How to cite: Mohn, C., Schourup-Kristensen, V., Larsen, J., Schwarzkopf, F., Biastoch, A., Tojera, I., Souto, M., Kaufmann, M., van der Kaaden, A.-S., Soetaert, K., and van Oevelen, D.: Seamounts and giant carbonate mounds drive bio-physical connections in the deep-sea: Two case studies from the North Atlantic., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19827, https://doi.org/10.5194/egusphere-egu24-19827, 2024.

The depleted mantle and the continental crust are largely geochemically and isotopically complementary. However, the question of when the depleted mantle reservoirs developed on Earth remains a topic of considerable debate. In this study, we report the existence of a ca. 3.8 Ga detrital zircon from the quartzite of the Paleoproterozoic Songshan Group in the southern North China Craton. In situ zircon hafnium isotopic characteristics of the 3.8–3.2 Ga detrital zircons indicate the presence of source rocks as old as ca. 4.5 Ga in the southern North China Craton. Together with the global zircon U-Pb-Hf isotope dataset from the North China Craton, Jack Hills, Acasta as well as available μ142Nd values of ancient rocks from Archean craton worldwide, the new results indicate that the silicate Earth has differentiated at 4.5–4.4 Ga almost immediately after accretion, developing continental crust and a complementary depleted mantle reservoir at that same time.

How to cite: Si, B., Diwu, C., and Si, R.: Eoarchean-Paleoarchean crustal material in the southern North China Craton and possible mantle reservoir of early Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-406, https://doi.org/10.5194/egusphere-egu24-406, 2024.

EGU24-1479 | Orals | GD3.1 | Highlight

Recipes for a Hadean Earth 

Stephen J. Mojzsis and Anna Medvegy

Silicate+metal worlds like Earth form hot owing to gravitational heating from accretion and differentiation, and intrinsic radioactive decay. Concurrent cooling sets off a chemical and mechanical cascade wherein siderophile elements (Fe+Ni) form a metallic core, and lithophile elements (Mg, Si, Al, Ca, Na, etc.) partition into mantle and siliceous crust. The outcome is a rocky surface beneath an outgassed fluid envelope composed of atmophile elements and compounds (CO2, H2O, H2, etc.). In its first 500 Myr (q.v. Hadean eon), Earth’s crust co-existed with liquid water; it was molded by volcanism, affected by late accretion bombardments and harbored diverse hydrothermal systems. Volcanism and differential buoyancy of the crust mandates the presence of scattered emergent landmasses. Such Hadean surfaces could host diverse (sub-)aqueous where organic chemical ingredients became concentrated to reactivity beneath a dense atmosphere bathed by the active young Sun. Soon after planet formation, it seems proto-biochemical reactions led to full-fledged living biochemistry. We do not know whether the earliest environments for life were ideally suited for its origin, or merely just good enough to accomplish the task. The inferred complexity for even the minimum biological entity means that operative and persistent biochemistry are the most difficult developmental stages to reach.

How to cite: Mojzsis, S. J. and Medvegy, A.: Recipes for a Hadean Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1479, https://doi.org/10.5194/egusphere-egu24-1479, 2024.

EGU24-1792 | ECS | Orals | GD3.1

Litho-structural framework of the Eoarchean Tussaap supracrustal belt, Itsaq gneiss complex, southwestern Greenland 

Peter Haproff, Alexander Webb, Chit Yan Eunice Leung, Christoph Hauzenberger, Jiawei Zuo, and Anthony Ramírez-Salazar

The Isua and Tussaap supracrustal belts of the Itsaq gneiss complex, southwestern Greenland, form the largest and best-preserved exposure of Eoarchean supracrustal materials on Earth. Previous studies have almost exclusively focused on the ∼35-km-long, arc-shaped Isua supracrustal belt and adjacent ca. 3.8–3.7 Ga meta-tonalite bodies, which are the basis for competing Archean tectonic regime interpretations (i.e., plate versus heat-pipe tectonics). In this study, we performed geologic field mapping of the seldom-explored Tussaap supracrustal belt, located ~11 km south of the Isua supracrustal belt, to better constrain its litho-structural framework and test the predictions of existing Eoarchean tectonic models. Observations from this study and previous works show that the Tussaap supracrustal belt consists of a east-northeast-striking, ~12-km-long and <1-km-wide, mostly continuous belt of greenstone rocks flanked to the north and south by ca. 3.8 Ga meta-tonalite. Lithologies of the Tussaap supracrustal belt consist of interlayered garnet ± staurolite ± sillimanite paragneiss, felsic schist, garnet mafic schist, amphibole-rich garbenschiefer, and minor pegmatite bodies and meta-ultramafic rocks. The northern and southern contacts between the Tussaap supracrustal belt and meta-tonalite are ~100-m-wide transitional zones featuring interlayered and folded meta-tonalite and greenstone rocks that increase in abundance towards each lithologic unit. Both the Tussaap supracrustal belt and adjacent meta-tonalite feature well-developed, southeast-dipping foliation and southeast-plunging stretching lineation (average 162° trend, 40° plunge). Macroscopic sheath and often rootless, disharmonic folds with hinges parallel to stretching lineation occur throughout the study area. In contrast with previous interpretations, no discrete tectonic discontinuities (i.e., brittle faults and ductile shear zones) were observed within the Tussaap supracrustal belt and meta-tonalite. Similarly, no apparent metamorphic field gradient was observed in the study area. This litho-structural framework is consistent with that of the Isua supracrustal belt and meta-tonalite bodies to the north, indicative of spatially-uniform strain and metamorphism. Based on our preliminary observations, the Archean development of the region can be explained by uniform subvertical shearing and folding of an interlayered volcanic-intrusive sequence (i.e., heat-pipe tectonics). Additional structural, geochronologic, and geochemical analyses of the Tussaap supracrustal belt and meta-tonalite are required to further elucidate their emplacement and metamorphic histories and differentiate end-member models of Archean tectonics.

How to cite: Haproff, P., Webb, A., Leung, C. Y. E., Hauzenberger, C., Zuo, J., and Ramírez-Salazar, A.: Litho-structural framework of the Eoarchean Tussaap supracrustal belt, Itsaq gneiss complex, southwestern Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1792, https://doi.org/10.5194/egusphere-egu24-1792, 2024.

An Archean ancestral landmass of Columbia supercontinent is a matter of concern to geologists. A single supercontinent called “Kenorland” or several supercratons have been mainly proposed, but more evidence from geological records and palaeomagnetism argue for the latter supercraton solution, in which two long-lived supercratons Sclavia and Superior were recently reconstructed. Studies has shown that the Northern China blocks, including the North China and Tarim cratons, the Alxa, Quanji blocks, were involved in the reconstruction of Columbia. However, their affinity in Archean supercratons remained little constrained. Owe to the lack of reliable palaeomagnetic data old than 1.8 Ga, the geological piercing points in these blocks could allow us to figure out the question. Then, compilation and comparison of Neoarchean–early Paleoproterozoic magmatism, metamorphism, and sedimentary records, have been conducted among these blocks. As a result, 2.4-2.2 Ga magmatism and khondalite-like sedimentary sequence may be used as indicators of the affinity of these blocks in northern China. Consequently, the Kuruktag Block, Quanji Block, Alxa Block, TNCO, Khondalite Belt have similar evolutionary history during the Neoarchean-Paleoproterozoic, suggesting their close affinity at that period. Besides, the North China craton and Dharwar craton of India shield were proved to be connected during the Archean-Proterozoic. And latest study indicate the Dharwar craton was one of the Sclavia supercraton. Therefore, we speculate that during the Neoarchean–early Paleoproterozoic, the Kuruktag-Quanji-Alxa-TNCO-Khondalite Belt link was close to the Dharwar craton in Sclavia supercraton. The absence of Siderian glacial event (ca. 2.4 Ga) in the Alxa, Quanji, Kuruktag blocks and TNCO, Khondalite Belt of the North China craton rule out the link with Superia, which is common in Superia supercraton. Further geological and paleomagnetic studies are required to constrain the above hypothesis, the relation between these blocks clusters and other cratons, which is crucial to understand the origins of blocks in northern China.

How to cite: Zhang, Q. and Yao, J.: Paleogeographic affinity of Northern China block clusters in Archean-Paleoproterozoic supercraton solution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2507, https://doi.org/10.5194/egusphere-egu24-2507, 2024.

1 Deep Space Exploration Laboratory / School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui, China.

2Department of Earth Sciences, The University of Hong Kong, Hong Kong, Hong Kong.

3Department of Geology, State Key Laboratory of Continental Dynamics, Northwest University, Xi'an, China.

* Corresponding author: wuzq10@ustc.edu.cn.

The origins of the Archean cratons were most important events in the early Earth and crucial for understanding how the early Earth worked. The mechanisms for the origins of the Archean cratons remain unclear. It is widely accepted that Archean tonalite-trondhjemite-granodiorite (TTG) plutons were derived from hydrous mafic magmas in the garnet/ amphibole stability field. Although the subduction can bring water to the mantle to produce granitic magma, the island Arc Model for the origin of continents meets fundamental challenges. The growing evidences support the plume-driven oceanic plateau models for the origin of continents. However, the lower parts of the oceanic plateau have been thought to be dry. How to generate the hydrous meta-basalt at the base of the oceanic plateau remain an open question.

Here we show that the Archean cratons resulted from the evolution of the hydrous magma ocean (Wu et al., 2023). The whole-mantle magma ocean created by the moon-forming giant impact likely evolved into an outer magma ocean and a basal magma ocean because the magma ocean would initially crystallize in the mid mantle and the basal magma ocean is denser than the overlying solid mantle. The basal MO at the beginning should contain a certain amount of water since extensive studies suggest substantial accretion of water-rich bodies during core formation. The major lower-mantle minerals have limited water storage capacity. Therefore, with progressive crystallization, the basal magma ocean becomes increasingly enriched in water. The basal magma ocean eventually becomes gravitationally unstable because of the enrichment of water. The triggered massive mantle overturns transported a large amount of water upward to the shallow part of the Earth and resulted in the major pulses of the crust and thick SCLM generations. The model can account for many observations including the source of water needed for generation of the continental crust, the major pulse of crustal growth around the end of the Archean, why the TTG and thick SCLM basically occurred in the Archean, and why only the Earth among inner planets was covered with the continental crust.

 

Wu, Z., Song, J., Zhao, G., & Pan, Z. (2023). Water-induced mantle overturns leading to the origins of Archean continents and subcontinental lithospheric mantle. Geophysical Research Letters, 50, e2023GL105178. https://doi.org/10.1029/2023GL105178

How to cite: Wu1, Z.: Water-induced mantle overturns and the origins of Archean cratons, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2870, https://doi.org/10.5194/egusphere-egu24-2870, 2024.

The BIFs in Bundelkhand Craton occurred as a discontinuous unit within the east-west trending Bundelkhand Tectonic Zone (BTZ). The BIFs were associated with amphibolite, calcsilicate rocks, and quartzite. The BIFs were massif in appearance in the Mauranipur (east of Bundelkhand Tectonic Zone, BTZ) that graded to layered variety in the Babina area (west of the BTZ).

The Bundelkhand BIFs were characterized by 45 to 55 wt.% SiO2 and 44 to 55 wt.% Fe2O3 content. The Al2O3 content was usually low and varied between > 1 to 3 wt%. Barring a few samples, the MnO and CaO contents are < 1 wt.%. The higher MnO (~ 3.70 wt.%) and CaO (~ 1 wt.%) implied a different redox condition and involvement of CaCO3 in the early stages of BIF formations. The ΣREE content of Bundelkhand BIFs varied between 10 – 38 ppm, with Eu/Eu*SN values between 1.1 to 1.5. Geochemically, the BIFs were classified as Algoma-type BIFs deposited by low-temperature hydrothermal fluids. Monoclinic amphiboles, quartz and garnet were the dominant silicate phase for Mauranipur BIFs. Hornblende was present with monoclinic amphibole in the garnet-absent BIFs. Isolated grains of magnetite were dispersed throughout the Mauranipur BIFs. In contrast, alternate hematite and SiO2-rich layers with locally developed low-T amphiboles characterized Babina BIFs. The Fe-rich oxides were mostly hematite. Mineral microstructure and P-T pseudo-section modeling implied Minnesotaite and Fe-Ca carbonate phases were the primary minerals in BIFs, deposited at temperature ~ 200°C at 0.05 to 0.1 GPa. The primary minerals experienced dehydration and decarbonization reactions, leading to the stabilization of amphibole and garnet at a temperature of ~450°C and pressure of 0.1—0.2 GPa. When plotted in a P-T diagram, the increase in temperature corresponds to tectonic activity and plutonism, leading to micro-bock accretion and growth of Bundelkhand Craton.

How to cite: Raza, M. B. and Nasipuri, P.: Mineralogy and P-T condition of Algoma type Banded Iron Formation from Bundelkhand Craton, North-Central India and their implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2992, https://doi.org/10.5194/egusphere-egu24-2992, 2024.

Iron Formations (IF) are economically significant sedimentary rocks primarily formed in the Precambrian evolutionary history of the Earth. In the Precambrian period, Iron Formations were deposited within marine sediments on stable continental margins (superior-type) and in association with volcanic rocks and many volcanic Massive Sulphide (VMS) deposits (Algoma-type). Most scientists agree that for BIF to form, photosynthesis and changing ferrous iron from seawater into mixed-valence iron (oxy-hydroxide) oxides and carbonate phases during oxidation are needed.
The present study is based on the Superior-type BIFs from the Girar Supracrustal Belt of Southern Bundelkhand terrane, which mainly consists of Neoarchean K-rich granitoids with a minor volume of a schist complex, TTG, sanukitoids, and mafic-ultramafic layered intrusion. The Girar schist (metasedimentary) belt is mostly made up of two types of rocks: (i) quartzite and (ii) BIFs. There are also some dolomitic marble and chlorite schist lenses close to the quartzite/BIF boundary. The BIFs consist of thick-bedded quartz and hematite with magnetite. The quartzites display low-grade metamorphism of fuchsite- and hematite-bearing quartz arenite with thick meta-argillite (schist) laminae and lesser quartz pebble conglomerates.
P-T pseudosection modelling indicates that Fe-carbonates and iron-oxyhydroxides (minnesotaite) are the primary phases that stabilize at 200 – 250 O C, 0.1–0.15 GPa. Subsequently, the low-temperature phases experienced dehydration and decarbonisation reactions with an increase in temperature, leading to the stabilisation of hematite and magnetite. The absence of orthopyroxene in the BIFs suggests these rocks suffer amphibolite facies
metamorphism, which is uncommon in generally undeformed superior-type BIFs.

How to cite: Bisht, B. P. S.: Mineralogy and P-T conditions of Superior- type Iron Formation fromBundelkhand Craton, North Central India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3109, https://doi.org/10.5194/egusphere-egu24-3109, 2024.

EGU24-3114 | ECS | Orals | GD3.1

Reconstruction of the Tarim craton within Rodinia: constraints from magmatic- orogenic records in the Altyn belt 

Wei Li, Jinlong Yao, Guochun Zhao, and Yigui Han

The position of the Tarim craton within the Rodinia supercontinent has long been the focus of scientific debate, with competing models varying from internal to external positions. The Altyn belt in the southeast Tarim margin records an extensive Neoproterozoic magmatic-sedimentary successions which likely recorded the convergence of Tarim to Rodinia. Thus, we here investigated the granitoids exposed in the Kuoshi-Kalaqiaoka and Tula areas in the eastern and western segment of the South Altyn belt. We present new field geology, zircon U–Pb–Hf–O isotopes and H2O, and whole rock geochemistry data from these granitoids. Zircon U–Pb data yielded ages of 914 ± 3.9 Ma for the Tula granite, 919 ± 5.2 Ma and 932 ± 6.5 Ma for the Kuoshi granite. The Tula and Kalaqiaoka granite samples mostly display high ACNK values that are typical of S-type granitoids, consistent with the presence of Al-rich minerals, such as garnet and muscovite. In addition, the Tula granite have higher zircon δ18O (7.62 to 10.85‰, peaked at 8.9‰) and lower εHf(t) (-4.0 to +0.3) values, along with lower H2O content (medium values at 102 and 251 ppmw), indicating that the primary magmas were generated from recycled ancient crust in a water-deficient syn-collisional setting, with minor juvenile contribution. On the other hand, the Kuoshi granite have high Sr (169–259 ppm), Sr/Y (17.85–19.33) and (La/Yb)N (30–49) ratios that are indicating of adakitic affinity. The Kuoshi granite are also characterized by lower δ18O (4.15 to 9.81‰, peaked at 8.2‰) and εHf(t) values(−2.4 to 0.6), along with higher H2O content (medium values at 255 and 795 ppmw) and MgO. These signatures suggest that the Kuoshi pluton was formed by recycling ancient crust and subducted continental crust. Overall, the granitoids across the South Altyn belt reflect a transformation of tectonic regime from water-enriched subduction setting to water-deficient syn-collisional setting. Moreover, the Hf isotopes evolution tend of the early Neoproterozoic granitoids and Suoerkuli Group across the South Altyn belt also suggest a transformation from slab retreat to syn-collision in the early Neoproterozoic. Therefore, overall data and field relations across the Altyn belt indicate an early Neoproterozoic magmatic-sedimentary successions that are similar to that of the Eastern Ghats Belt in India. Given the available paleomagnetic data and detrital zircon age patterns, we conclude a position of the Tarim craton between Australian and North India block in the periphery of Rodinia, close to East Antarctica as well. This research was supported by NSFC Projects (42322208 and 41972238), National Key Research and Development Programs of China (2022YFF0802700 and 2023YFF0803604) and Hong Kong RGC GRF (17308023).

How to cite: Li, W., Yao, J., Zhao, G., and Han, Y.: Reconstruction of the Tarim craton within Rodinia: constraints from magmatic- orogenic records in the Altyn belt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3114, https://doi.org/10.5194/egusphere-egu24-3114, 2024.

EGU24-3303 | ECS | Orals | GD3.1

Redox state of Archean surface environments: Insights from the Banded Iron Formations (BIFs) of the Western Dharwar Craton, Southern India  

Aindrila Mukherjee, Jayananda Mudlappa, Pritam Nasipuri, and Aadhiseshan Krishnasamy Raveendran

The interplay of geological, chemical and biological processes that drive the oxygenation of the oceans-atmosphere of the early earth are spatially linked to the emergence of biosphere. Banded Iron Formations (BIFs) from the Archean greenstone belts form important archives for understanding the redox conditions of Archean surface environments. The Archean Dharwar craton preserves BIFs in the volcano-sedimentary greenstone belts of two distinct stratigraphic units (older Sargur Group and younger Dharwar Supergroup) corresponding to a time span of 3300-2600 Ma.  These BIFs are confined to the highest stratigraphic levels forming summits of greenstone belts.  They show alternate layers of chert and iron oxides, and petrographic data reveal diverse mineralogy including oxides, carbonate, sulphide and silicate facies. The occurrence of riebeckite and stilpnomelane in BIFs of younger Dharwar Supergroup indicates recrystallization under low-grade metamorphism. Slightly higher abundances of CaO and Al2O3 reveal significant influence of crustal source and precipitation of CaCO3 during BIFs formation. Mesoscopic layers of chert and iron oxide with variable thickness suggest fluctuating redox state of surface environments. The higher enrichment of Ni (6-26 ppm) than the Cr content (3-19 ppm) with variable Sr concentrations may be attributed to feldspar breakdown during hydrothermal fluid acceleration. Trace element ratios (Y/Ho, Sm/Yb, Eu/Sm) coupled with positive Eu anomalies of the BIFs from both older Sargur Group and younger Dharwar Supergroup BIFs reveal dominant hydrothermal input in BIFs origin. The PAAS normalized REE data preclude major continental input in the origin of BIFs. The variable negative Ce anomalies imply periodic fluctuating surface environments (oxic to anoxic) at the dawn of the Great Oxidation Event close to 2340 Ma. This is consistent with the published Fe, N, and S isotope data on the BIFs of the Western Dharwar craton.

 

How to cite: Mukherjee, A., Mudlappa, J., Nasipuri, P., and Krishnasamy Raveendran, A.: Redox state of Archean surface environments: Insights from the Banded Iron Formations (BIFs) of the Western Dharwar Craton, Southern India , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3303, https://doi.org/10.5194/egusphere-egu24-3303, 2024.

EGU24-3394 | Orals | GD3.1

Paleoarchean volcanic stratigraphy and geochemistry of the mafic-ultramafic Kromberg Formation type-section, Barberton greenstone belt, South Africa. 

Eugene Grosch, Sibu Ndlela, David Murphy, Nicola McLoughlin, Jakub Trubac, and Jiri Slama

In this study, the c. 3.334 Ga Kromberg Formation of the Onverwacht Group, in the south-eastern limb of the Onverwacht Anticline in the Barberton greenstone belt (South Africa) is investigated. Various geodynamic models have been proposed for the evolution of the Kromberg Formation, but detailed geochemical constraints on the mafic-ultramafic sequence are sparse. The objectives are to constrain the Paleoarchean mantle source characteristics and geodynamic setting for the Kromberg mafic-ultramafic rocks, placed in the context of recent high-resolution field mapping data. To study the protolith volcanic rocks, sampling has been conducted to avoid areas affected by deformation-related alteration. In addition, screening for alteration due to Archean seawater silicification has also been conducted. In conjunction with major, trace and rare earth element data, this study presents the first whole-rock Lu-Hf isotope analyses of mafic-ultramafic rocks of the Paleoarchean Kromberg Formation type-section in the Barberton greenstone belt (Grosch et al., 2022). Three compositionally distinct volcanic rock types are identified namely Group 1 metabasalts, Group 2 metabasalts and komatiitic metabasalts. The geochemistry of these rock types will be presented, and a possible geodynamic setting on the early Earth will be explored.  

Grosch, E.G., Ndlela S., Murphy D., McLoughlin N., Trubac J., Slama J., (2022) Geochemistry of mafic-ultramafic rocks of the 3.33 Ga Kromberg type-section, Barberton greenstone belt, South Africa: Implications for early Earth geodynamic processes. Chemical Geology 605, 120947

How to cite: Grosch, E., Ndlela, S., Murphy, D., McLoughlin, N., Trubac, J., and Slama, J.: Paleoarchean volcanic stratigraphy and geochemistry of the mafic-ultramafic Kromberg Formation type-section, Barberton greenstone belt, South Africa., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3394, https://doi.org/10.5194/egusphere-egu24-3394, 2024.

EGU24-3563 | ECS | Orals | GD3.1

The geological record of H2 production in the Archean 

Renée Tamblyn and Jörg Hermann

The oxidation of iron from rocks during subaqueous alteration is a key source of the molecular hydrogen (H2) used as an energy source by chemosynthetic organisms, which may represent some of the earliest forms of life on Earth. In the Archean, a potential source of ultramafic material available for serpentinisation reactions that release H2 are komatiites. Komatiites are highly magnesian lavas, which contain evidence of extensive serpentinisation and magnetite (Fe2+Fe3+2O4) production close to the Archean seafloor. H2 production in komatiitic compositions has been modelled and experimentally investigated; however, the natural rock record has remained unexplored. Here, we examine the geological evidence of H2 production from the basaltic to komatiitic rock record held in Archean cratons. From the petrological investigation of thirty-eight samples of komatiitic basalt to komatiite, we identify the unique serpentinisation reaction responsible for H2 production from these lithologies. With support from over 1100 bulk rock geochemical analyses, we directly quantify Fe3+ and therefore H2 production of komatiites in the Archean. The chemical (high Mg) and physical (low viscosity flow) characteristics of komatiite flows allowed for extensive hydration and serpentinisation in oceanic plateaus, and therefore high H2 production available to chemosynthetic early life.

How to cite: Tamblyn, R. and Hermann, J.: The geological record of H2 production in the Archean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3563, https://doi.org/10.5194/egusphere-egu24-3563, 2024.

EGU24-4334 | Orals | GD3.1

Earth's evolution over time revealed by the Nb/U, Ce/Pb and Nb/Th ratios in the sources of mantle plumes. 

Alexander Sobolev, Adrien Vezinet, Aleksandr Chugunov, Mateo Esteban, Valentina Batanova, Nicholas Arndt, Charitra Jain, Stephan Sobolev, Evgeny Asafov, and John Valley

Magmas from mantle plumes are potentially the best monitors of Earth's compositional and thermal evolution over time. However, their erupted products are commonly modified by syn- and post-magmatic processes and thus do not fully retain original information about their mantle sources. Such data can be recovered from melt inclusions in olivine phenocrysts in the most primitive magmas from mantle plumes. Such inclusions, shielded by host olivine, retain original isotopic and critical trace element signatures of deep mantle sources even for Archean and Hadean Eons.

We will present the results of a study of chemical and Rb-Sr isotope composition (EPMA, LA-ICP-MS and RAMAN) of melt inclusions and chemical (EPMA, LA-ICP-MS) compositions of host olivines for komatiites and plume-related picrites with eruption age from 3.3 Ga to 1 Ka.

Recent advances in in-situ split stream LA-ICP-MS measurements of 87Sr/86Sr ratios and trace element contents of olivine-hosted melt inclusions revealed significant mantle source heterogeneities of magmas from individual plumes. The results are confirmed by geodynamic modelling (Jain et al., this meeting).

We show that the melt inclusions of most studied mantle plumes display heterogeneous populations in age-corrected 87Sr/86Sr ratios and include groups with model ages more than 1 Ga older than the emplacement age. The oldest inclusion groups found in Archean komatiites correspond to Hadean (4.3±0.2Ga, Vezinet et al., in review) and Eo-Paleoarchean (3.6±0.2 Ga) model ages. These and most inclusions from studied komatiites and picrites display Nb/U, Nb/Th and Ce/Pb significantly higher than in BSE.

Evolution over time of canonical proxies of continental crust generation (Nb/U, Th/U and Ce/Pb, Hofmann et al., 1986) in mantle plumes, combined with geodynamic modelling, suggests:

  • Most of the continental crust was generated in several Hadean and Archean pulses by plume-induced subduction and melting of the hydrated mafic/ultramafic crust or mantle. Hadean continental crust was subducted or/and reworked.
  • Restites left after extraction of continental crust were continuously subducted to the core-mantle boundary from the mid-Hadean and later recycled in Archean mantle plumes.
  • Active formation of both continental and oceanic crust in Hadean was governed by plume-induced subduction, which ceased after cold subducted material hindered the propagation of large plumes at the core-mantle boundary. After heating the recycled lithosphere at the core-mantle boundary, the process repeats, producing oscillating subduction and crustal formation in Hadean-Archean.

How to cite: Sobolev, A., Vezinet, A., Chugunov, A., Esteban, M., Batanova, V., Arndt, N., Jain, C., Sobolev, S., Asafov, E., and Valley, J.: Earth's evolution over time revealed by the Nb/U, Ce/Pb and Nb/Th ratios in the sources of mantle plumes., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4334, https://doi.org/10.5194/egusphere-egu24-4334, 2024.

The results of the U-Pb-Hf-O isotope study of zircon from (meta)igneous rocks sampled in all domains of the Ukrainian Shield allow recognition of the four main stages of continental crust formation:

1. The Eoarchean stage (ca. 4000-3600 Ma). Rocks of this stage occur in the Dniester-Bouh and Azov domains. In the former, they are represented by heavily metamorphosed enderbites and mafic schists reaching an age of 3.8 Ga. In contrast, tonalites with an age of 3.67 Ga were identified in the Azov Domain. The oldest zircon reaching an age of 3970 Ma was found in the Mesoarchean metadacite in the Azov Domain. The Eoarchean rocks are rare, but their presence indicates that crust-forming processes have started already in the Eoarchean, or even in Hadean, time.

2. The second major event took place between c. 3.2 and 2.7 Ma. Rocks, formed during this age interval, compose around half of the Ukrainian Shield. Considering the long duration of this event, it may have consisted of several separate episodes. The whole set of rock associations typical for the Archean continental crust, including TTG series, greenstone belts and sedimentary basins, has been formed. Hafnium isotope composition in zircon reveals the juvenile nature of this event. Some remobilization of the older crust is also recorded from several samples.

3. Nearly half of the rock assemblages were dated at ca. 2.15-1.90 Ga. In contrast to the Archean events that resulted in the formation of apparently more or less equant terranes, the Paleoproterozoic events led to the formation of orogenic belts. These belts comprise metamorphosed in amphibolite or epidote-amphibolite facies supercrustal sequences, and abundant granitic intrusions. According to the existing models, the formation of the orogenic belts was related to the assembly of Baltica as a part of the Columbia/Nuna supercontinent. Hafnium-in-zircon and whole-rock Nd isotopes indicate the predominantly juvenile nature of these rocks, with some contamination by the Archean crust.

4. The last major stage of the Ukrainian Shield evolution was linked to the formation of the Prutivka-Novohol large igneous province, which between 1.8 and 1.72 Ga affected the whole Shield. It resulted in the emplacement of numerous mafic dykes and layered massifs, alkaline intrusions, and huge anorthosite-mangerite-charnockite-granite complexes. All igneous rocks formed during this stage reveal signs of crustal contamination, although input of moderately depleted mantle material is also evident.

Obtained isotope and geochronological data demonstrate that the growth of the continental crust in the Ukrainian Shield was episodic. The mechanisms of the crustal growth were different at different times. During both Archean events, the main mechanism was mafic underplating with further remelting and generation of TTG series, whereas greenstone belts represent the results of mantle plume activity. In the Paleoproterozoic, the main mechanism of crustal growth was the subduction of the oceanic lithosphere that led to the formation of volcanic arcs. Mantle plumes remained an important mechanism of the input of mantle-derived material into the continental crust.

How to cite: Shumlyanskyy, L.: The main stages of the Ukrainian Shield evolution and plate tectonics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4724, https://doi.org/10.5194/egusphere-egu24-4724, 2024.

EGU24-4875 | ECS | Posters on site | GD3.1

Plume-induced continental crust growth rate in Early Earth:Insight from numerical modeling 

Xinyi Zhong, Zhong-Hai Li, and Yang Wang

The origin of Earth’s felsic continental crust is still a mystery. The continental crust requires two-steps partial melting of mantle rocks. There are two proposed hypotheses for the continental crust growth in the Early Earth. One is the subduction-related magmatism, e.g. island arc, that produces intermediate to felsic magma which constitutes the early buoyant continental crust. The other is that the magmatism induced by mantle plume creates the thick basaltic crust, and which partially melts into continental crust. However, both two models have their deficiencies. It is still a controversial topic that when plate tectonics begins, which is an obstacle for applying the subduction-induced model in the Early Earth. On the other hand, the plume-induced model seems to be inefficient to support the continental crust growth. The previous numerical studies haves generally focused on the mechanisms of the continental crust formation, while efficiency of the model remains unknown. Thus, we simulated the melt transport process and integrated petrological model in our numerical model to evaluate the efficiency and the plausibility of continental crust production by mantle plume in the Earth’s history. The comparison between our model results and the reconstruction model of continental crust growth provides a new insight for the problem. The results indicates that the mantle plume is an efficient and possible way to support rapid continental crust growth in the Archean. Other mechanisms, e.g. subduction, may take dominant role since the Proterozoic because of low efficiency of plume-induced continental crust production.

How to cite: Zhong, X., Li, Z.-H., and Wang, Y.: Plume-induced continental crust growth rate in Early Earth:Insight from numerical modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4875, https://doi.org/10.5194/egusphere-egu24-4875, 2024.

EGU24-5245 | Orals | GD3.1

Elemental fluxes into 3.0-billion-year-old marine environments: evidence from trace elements and Nd isotopes in banded iron formations from the Murchison Greenstone Belt, South Africa 

Johanna Krayer, Sebastian Viehmann, Alina Mayer, Toni Schulz, Christian Koeberl, Axel Hofmann, Jaganmoy Jodder, Matthias Willbold, and Stefan Weyer

Banded Iron Formations (BIFs) are authigenic, marine sediments directly reflecting the chemical composition of ancient seawater. BIFs serve as prime geochemical archives for the reconstruction of Precambrian marine environments. However, due to the scarcity of well preserved Archean rocks, atmospheric and hydrospheric environmental conditions within this time frame are still incompletely understood. In particular, elemental fluxes derived from continental weathering and submarine hydrothermal fluxes that affected ancient seawater chemistry are cornerstones for our understanding of the evolution of marine habitats through time. Here we present major- and trace element concentrations in combination with Nd isotopic compositions of 13 samples of Mesoarchean Algoma-type greenschist-facies BIFs from the ca 3.0 Ga old Murchison Greenstone Belt, South Africa. Individual Fe- and Si-rich layers are monitored for sample purity based on their chemical composition. Neodymium isotope compositions, in combination with trace element contents of BIF samples with varying amounts of clastic detritus, are further used to reconstruct the Murchison depositional environment and identify the origin of dissolved and detrital components entering the ancient ocean around 3.0 Ga ago.

Eight samples with low immobile element concentrations display typical shale-normalized Archean seawater-like rare earth and yttrium (REYSN) patterns with positive LaSN, EuCN, and GdSN anomalies, super-chondritic Y/Ho ratios, and an enrichment of heavy REYSN over light REYSN, implying an open marine-dominated depositional setting with contributions from submarine high-temperature, hydrothermal systems. A Sm-Nd regression line yields an age of 2.98 ± 0.19 Ga that overlaps with the proposed depositional age, suggesting negligible post-depositional alteration on the REY composition of the pure BIF layers. In contrast, higher concentrations of immobile elements (e.g., Zr) and/or non-seawater-like REYSN patterns are characteristic for the remaining five BIF samples, indicating elevated detrital input or post-depositional alteration. A regression line of the impure BIF layers yields an age of 2.49 ± 0.15 Ga, reflecting a potential post-depositional overprinting event such as the 2.6 Ga old Limpopo orogeny. The Nd isotopic compositions of pure and impure BIF samples cover a wide range of ca. two epsilon units suggesting a mixture of weathered mafic and felsic sources for the dissolved and suspended fluxes into the Murchison ocean.

How to cite: Krayer, J., Viehmann, S., Mayer, A., Schulz, T., Koeberl, C., Hofmann, A., Jodder, J., Willbold, M., and Weyer, S.: Elemental fluxes into 3.0-billion-year-old marine environments: evidence from trace elements and Nd isotopes in banded iron formations from the Murchison Greenstone Belt, South Africa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5245, https://doi.org/10.5194/egusphere-egu24-5245, 2024.

EGU24-5391 | ECS | Posters on site | GD3.1

Diverse P-T-t paths within the Neoarchean sagduction regime of North China Craton: insights from field data and numerical modeling 

Chenying Yu, Ting Yang, Jian Zhang*, Guochun Zhao, Peter A. Cawood, Changqing Yin, Jiahui Qian, Peng Gao, and Chen Zhao

The Neoarchean greenstone-granite rock association preserved in the Eastern Block of the North China Craton exhibits distinctive dome-and-keel structures. Although the metamorphic data from these rock assemblages provide valuable insights into the tectonic evolution of this region, the interpretation of the clockwise paths with nearly isothermal decompression (ITD) and the anticlockwise P–T paths involving near-isobaric cooling (IBC) remain inconsistent and controversial. By conducting 2D numerical models with the initial and boundary conditions similar to those of the Neoarchean Eastern Block, we investigated the coexistence of diverse P-T paths and determined their possible geodynamic regime. The model results demonstrate that the combination of crustal density inversion and heat from the high-temperature lower boundary initiates a crustal-scale sagduction process, leading to the formation of dome-and-keel structures. Additionally, we identified four primary types of P-T-t paths. Firstly, an anticlockwise IBC-type P-T-t path reveals the supracrustal rocks gradually subside to a deep crustal level, where they experience a prolonged residence period characterized by ambient mantle cooling without significant exhumation. Secondly, a clockwise ITD-type P-T-t path suggests the supracrustal rocks descend to the deep crust and are partly entrained by upwelling TTG magmas, leading to their rapid ascent to a middle crustal level. Thirdly, a newly identified crescent-type P-T-t path indicates an integrated burial-exhumation cycle, consisting of an initial burial stage with high dT/dP, followed by a rapid exhumation stage and a subsequent cooling stage exhibiting low dT/dP. Lastly, a hairpin-type P-T-t path highlights the slow exhumation rate experienced by deeply buried supracrustal rocks. The dome-and-keel structure and P-T-t paths observed in the numerical model are consistent with the geochronological, metamorphic and structural data of the Eastern Block. Based on these observations, we propose that the crustal-scale sagduction involving a mantle plume could responsible for the geological complexity of eastern China.

This work was financially supported by the National Natural Science Foundation of China (42025204) and National Key Research and Development Program of China (No. 2023YFF0803804).

How to cite: Yu, C., Yang, T., Zhang*, J., Zhao, G., Cawood, P. A., Yin, C., Qian, J., Gao, P., and Zhao, C.: Diverse P-T-t paths within the Neoarchean sagduction regime of North China Craton: insights from field data and numerical modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5391, https://doi.org/10.5194/egusphere-egu24-5391, 2024.

EGU24-6614 | Orals | GD3.1

Evolving Chemistry of Lithospheric Mantle Based on Oxygen Isotope and Trace Element Analyses of Olivines from Mantle Xenoliths across Earth’s History 

Ilya Bindeman, Valentina Batanova, Alexander Sobolev, Dmitri Ionov, and Leonid Danyushevsky

Oxygen is the most abundant element in the terrestrial mantle and crust. We have recently reported on a 0.2‰ δ18O decrease of continental mantle peridotites from the original primary Bulk Silicate Earth-Moon value of 5.57‰ [1] in the mid-Archean to the Phanerozoic explained by the initiation of surface recycling (linked to intensity and style of plate tectonics) sometime in the Archean. Even small variations in the volatile mass balance are critical in explaining phenomena such as the Great Oxidation Event at ~2.4 Ga that may have mantle origin. As low-δ18O subduction fluids are derived by the dehydration (and potentially oxidation) of low-δ18O interiors of subducted slabs, this work further explores this process to observe temporal changes related to the progressive input of volatile elements and potential lithospheric mantle oxidation. This study presents a record of trace elements measured in same olivines (Li, Na, Al, P, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Ga, Y, Zr) including oxidation-sensitive elemental ratios V/Sc and Zn/Fe for this collection. Prior melt-depletion of mantle peridotites, estimated using bulk Al2O3 content of the xenoliths, increases with age from ~25 to 35%, leading to depletion of Yb, Y, Co, Mn, Ca, P, with smaller effects on the elemental ratios.  We observe significant ranges of V/Sc (0.2-14), Li/Y and other ratios, not related to prior melt depletion that may be linked to subduction-related re-distribution of incompatible elements by subduction [2], and scattered correlation with age and δ18O values. Further trends will be analyzed during the talk after considering craton-specific domains and global trends. This work can potentially contribute to constraining a global mass balance of crustal growth and recycling based on co-variations of isotopes of a major element oxygen and trace elements in the predominant lithospheric reservoir of subcontinental mantle.

[1]Bindeman ea, (2022) Nat Comm 13, 3779; [2] Doucet ea, (2020) NatGeosci 13, 511.

How to cite: Bindeman, I., Batanova, V., Sobolev, A., Ionov, D., and Danyushevsky, L.: Evolving Chemistry of Lithospheric Mantle Based on Oxygen Isotope and Trace Element Analyses of Olivines from Mantle Xenoliths across Earth’s History, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6614, https://doi.org/10.5194/egusphere-egu24-6614, 2024.

EGU24-7106 | ECS | Orals | GD3.1 | Highlight

Fresh water on Earth four billion years ago 

Hamed Gamaleldien, Li-Guang Wu, Hugo K.H. Olierook, Christopher L. Kirkland, Uwe Kirsche, Zheng-Xiang Li, Tim Johnson, Sean Makin, Qiu-Li Li, Qiang Jiang, Simon A. Wilde, and Xian-Hua Li

The operation of a hydrological cycle (i.e., exchange of water between the land, oceans, and atmosphere) has significant implications for the emergence of life. The oldest confirmed single-celled organisms at ~3.48 billion years ago (Ga) (Pilbara Craton, Western Australia) are thought to have formed in the presence of meteoric (fresh) water on emerged (subaerial) land in a hot spring environment. However, when widespread interaction between fresh water and emerged continental crust first began is poorly constrained. In this study, we use >1000 oxygen isotope analyses of Jack Hills detrital zircon to track fluid-rock interactions from the Hadean to the Paleoarchean (~4.4–3.1 Ga). We identify extreme isotopically light O (i.e., δ18O < 4.0 ‰) values older than 3.5 Ga. The data define two periods of magmatism with extreme isotopically-light O as low as 2.0 ‰ and –0.1 ‰ at around 4.0 and 3.4 Ga, respectively. Using Monte Carlo simulations, we demonstrate that such values can only be generated by the interaction of crustal magmatic systems with meteoric water. Our data constrains the earliest emergence of continental crust on Earth, the presence of fresh water, and the start of the hydrological cycle that likely provided the environmental niches required for a life less than 600 million years after Earth’s accretion.

How to cite: Gamaleldien, H., Wu, L.-G., Olierook, H. K. H., Kirkland, C. L., Kirsche, U., Li, Z.-X., Johnson, T., Makin, S., Li, Q.-L., Jiang, Q., Wilde, S. A., and Li, X.-H.: Fresh water on Earth four billion years ago, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7106, https://doi.org/10.5194/egusphere-egu24-7106, 2024.

Several studies have already concluded the presence of 7-8 ocean equivalent water (OCE) in the mantle of earth, structurally occurring as H+/OH. This can affect the seismic anomaly, mechanical strength, ionic diffusion, etc. of the mantle. The upper mantle is primarily composed of olivine, which first transforms to wadsleyite and then to ringwoodite at ~13 and ~18 GPa, respectively. Petrological and mineralogical experiments have demonstrated that H, occurring as point defects can act as a source of water in the upper mantle. Being the abundant mineral in upper mantle, it is very important to investigate the ability of olivine to act as a potential mineral phase to house water. Incorporation of water in mantle minerals has been a burning topic for many theoretical and experimental works. Even a trace amount of water in mineral structure can significantly alter their physical (e.g., elastic behaviour, seismic velocities, etc.) and chemical properties (e.g., ionic diffusion, electrical conductivity, etc.). FT-IR studies suggested that a rapid diffusion of H+ in olivine makes it a better candidate for point defects compared to larger and heavier OH ions. Karato & Jung (2003)  showed that increment of H concentration in olivine decreases its strength. Later, Mao et al. (2008) and Panero et al. (2010) observed qualitatively similar trend in high pressure olivine polymorphs. They observed drastic reduction in selective elastic constants of C11compared to C12 and C44 as H content increases in ringwoodite. Huang et al. (2005) found that temperature and water increases electrical conductivity in both the polymorphs. Yoshino et al. (2009) reported that a hike in temperature switches H-diffusion mechanism in olivine from proton conduction to small polaron conduction. The H diffusion in Fe-bearing olivine is experimentally shown to be dictated by (i) Proton-polaron (PP) mechanism and (ii) Proton-vacancy (PV) mechanism in <1 GPa. The PV is found to be valid for incorporating more water in olivine compared to PP. However, the second method, despite being strongly anisotropic, allows a faster diffusion. Much of the existing studies deals with temperature and water content as the key physical factors in controlling proton diffusivity. The fact that most of these studies have not carried out in the exact pressure (p) and temperature (T) conditions of mantle of Earth demand further studies on the same. Present study involves the study of H diffusion in lattice structure of olivine and wadsleyite; their mechanical stability, physical and chemical properties under mantle p–T conditions. Our results suggest a drop in seismic velocities in both olivine and wadsleyite phases. This can explain few outstanding geological events such as, weakening of upper mantle etc. This study will also provide a water budget in these mantle minerals. Therefore, the proposed research embarks on advancing theoretical understanding of hydrous mineral phases, which have a stability under extreme thermo-mechanical conditions.

How to cite: Das, P. K. and Karangara, A.: First principle investigations on the water budget in olivine phases: Implications towards the behavior of hydrous mantle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7388, https://doi.org/10.5194/egusphere-egu24-7388, 2024.

EGU24-9476 | Orals | GD3.1

Spatially explicit simulations of the effect of tidal energy dissipation on the climate on early Earth 

Georg Feulner, Benjamin Biewald, J. A. Mattias Green, Matthias Hofmann, and Stefan Petri

The potential impact of the increased rates of tidal energy dissipation on the climate on early Earth is usually assessed in terms of the global contribution to the energy balance which is small compared to the incoming solar radiation. However, tidal energy dissipation depends strongly on the distribution of landmasses, and regional energy input could, in principle, impact the local and global climate state via changes in circulation patterns and feedbacks in the Earth system. Here we investigate these effects by calculating tidal energy dissipation for a randomly generated continental distribution representative of early Earth, and three different rotation rates, and feeding it into a coupled climate model. Despite marginal global impacts, tidal energy dissipation can have significant regional effects caused by changes in ocean circulation and amplified by the ice-albedo feedback. These effects are strongest in climate states and regions where meridional heat transport close to the sea-ice margin is altered. This suggests that tidal heating could have contributed to sustaining regions with no significant ice cover.

How to cite: Feulner, G., Biewald, B., Green, J. A. M., Hofmann, M., and Petri, S.: Spatially explicit simulations of the effect of tidal energy dissipation on the climate on early Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9476, https://doi.org/10.5194/egusphere-egu24-9476, 2024.

EGU24-10677 | Posters on site | GD3.1

Geochemical and Nd isotopic constraints on the evolution of Neoarchean continental crust underlying the central Deccan Traps 

Marc C. Halfar, Bradley J. Peters, James M.D. Day, and Maria Schönbächler

Ancient rocks documenting early silicate Earth processes are only sparsely preserved on its modern surface. Some of the oldest known crustal lithologies (≤3.7 Ga) can be found within the Indian Shield. However, a substantial area of the western and central Indian basement has been covered by the ~66 Ma old Deccan flood basalts. Some Deccan-related mafic dykes in the Nandurbar-Dhule region of the Narmada-Tapi rift zone host xenolithic crustal material, which can be used to study the otherwise inaccessible basement. Textural and mineralogical heterogeneity amongst these xenoliths implies that they derive from different depths of a single column of crust and represent randomly sampled crustal rock types with possibly distinct heritages. Well studied examples of these dykes are the adjacent Rajmane and Talwade dykes south of Duhle, which host Neoarchean-aged [1] crustal xenoliths with highly variable 87Sr/86Sr ratios between 0.70935 and 0.78479 [2]. This led previous researchers to infer a genetic relationship of these xenoliths with rocks from the Dharwar Craton [1, 2].

In this study, xenolith samples are used to investigate the evolution of sub-Deccan continental crust and evaluate whether randomly sampled crustal lithologies share a common Hadean heritage that is similar to published data for Dharwar granitic rocks. Our samples (n = 17) originate from two mafic dykes near Talwade and Ranala in the Nandurbar-Dhule region. We report major and trace element abundances and 142Nd isotopic compositions. The CIPW norms of xenoliths define a nearly continuous petrological evolution trend from tonalites to reworked, orthoclase-rich granites, with subordinate trondhjemitic compositions. The vertical cross-section of crust underlying the dykes therefore provides an opportunity to study the geochemistry of evolving primitive continental crust. Trace element abundance data also conform to a tonalite-trondhjemite-granodiorite-like (TTG) composition for a subset of the xenoliths, whereas others resemble younger granitoids, which might represent reworked TTG equivalents, or younger intrusions.

The short-lived (t1/2 = 103 Ma) 146Sm-142Nd decay system is particularly sensitive to magmatic fractionation processes that occurred within the first ca. 500 Ma of Earth’s history. Heterogeneous 142Nd/144Nd compositions (expressed as μ142Nd = [(142Nd/144Nd)sample/(142Nd/144Nd)JNdi – 1] * 106) are typically restricted to Archean-aged rocks and reveal information about the preservation of mantle heterogeneity over geological timescales. The μ142Nd of dyke host lavas (n = 3) are heterogeneous (μ142Nd = -2.0 ±5.1 to +6.1 ±5.1) but unresolved from the terrestrial standard. Such heterogeneity suggests that the parental magmas to the dykes experienced complex lithospheric and crustal assimilation during their ascent. Felsic xenoliths have homogeneous μ142Nd compositions (μ142Nd = -0.9 ±2.3, 95% c.i., n = 7). Combined with the major and trace element data, this implies an extensively reworked crust underneath the Deccan Traps. The lack of recognizable μ142Nd anomalies is consistent with data of younger Dharwar granitoids [3] and may reflect regional overprinting of mantle μ142Nd heterogeneity at or before the Neoarchean emplacement age of the xenoliths.

 

[1] Upadhyay et al. (2015) J. Geol. 123(3), 295–307.

[2] Ray et al. (2008) Gondwana Res. 13, 375–385.

[3] Ravindran et al. (2022) Goldschmidt Abst. 10986.

How to cite: Halfar, M. C., Peters, B. J., Day, J. M. D., and Schönbächler, M.: Geochemical and Nd isotopic constraints on the evolution of Neoarchean continental crust underlying the central Deccan Traps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10677, https://doi.org/10.5194/egusphere-egu24-10677, 2024.

EGU24-10889 | Orals | GD3.1

Archaean record of the Singhbhum Craton, India: new insights from greenstone belts and cratonic cover sequences.  

Jaganmoy Jodder, Axel Hofmann, Marlina Elburg, and Rebeun Ngobeli

In recent times, the Archaean geological record of the Singhbhum Craton has been scrutinized regarding early Earth crustal processes, tectonics, magmatic-detrital zircon geochronology, early life research, and Fe-Mn mineralization associated with volcano-sedimentary successions. However, many of these studies are hampered by a lack of a basic stratigraphic framework of the various litho-stratigraphic units, complicating our understanding of the overall Archaean geology of the Singhbhum Craton. Here, we share first-hand information on the Palaeoarchaean greenstone belts and Meso-Neoarchaean intracontinental volcano-sedimentary sequence of the Singhbhum Craton.

New magmatic zircon U-Pb ages determined from felsic volcanic rocks of the Badampahar Group are represented by their crystallization age at c. 3.51 Ga. Intrusive granitoids exposed in the Daitari and Gorumahisani greenstone belts yield crystallization ages ranging from 3.38 to 3.29 Ga and having inherited zircons being 3.58, 3.55, and 3.51 Ga old. A granitoid intrusive into iron formation of the Gorumahisani greenstone belt has an age of c. 3.29 Ga.  Detrital zircons recovered from Koira Group sandstone intercalated with iron formation yield a maximum depositional age of 2.63 Ga. 

We demonstrate that Palaeoarchaean greenstones exposed in the northern and southern parts of the Singhbhum Craton consists largely of sub-marine mafic-ultramafic volcanic rocks interlayered with minor felsic volcanic and chemical sedimentary rocks. Importantly, the ca. 3.51 Ga felsic volcanic rocks from the Badampahar Group permit comparison with co-eval felsic volcanic units reported from the lower part of the Onverwacht, Nondweni, Warrawoona groups of the Kaapvaal and Pilbara cratons. Otherwise, new age constraints of the Koira Group allow for better correlations with Meso-Neoarchaean cratonic cover successions elsewhere. 

How to cite: Jodder, J., Hofmann, A., Elburg, M., and Ngobeli, R.: Archaean record of the Singhbhum Craton, India: new insights from greenstone belts and cratonic cover sequences. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10889, https://doi.org/10.5194/egusphere-egu24-10889, 2024.

EGU24-12762 | ECS | Orals | GD3.1

Boron isotopes in global TTGs trace the increase in deep crustal recycling in the Mesoarchean   

Jeroen Goumans, Matthijs Smit, and Kira Musiyachenko

Granitoids of the Tonalite-Trondhjemite-Granodiorite (TTG) group are a prime constituent of Archean cratons. Differences in the composition of these rocks relative to modern-day, more potassic granitoids have been proposed to reflect changes in the conditions and mechanisms of crust generation. By extension, these differences may indicate changes in the tectonic regime through geological time. Despite a continuously growing body of TTG research, consensus on TTG generation and Archean tectonic settings has not yet been reached. A remaining open question regarding TTGs is whether a reworked crustal component is present. Silicon and O isotopes have been previously employed to address this question and both isotope systems suggest that at least some TTGs indeed contain reworked material. Boron provides an alternative isotope system that can trace surface-altered material in magmatic rocks because B isotopes fractionate significantly at Earth’s surface but remain relatively unaltered at high temperatures. On modern-day Earth, the deep recycling of isotopically heavy seawater-derived B through subduction results in a diverse, but on average heavy, B isotope composition in arc granitoids. Conversely, juvenile granitoids formed in settings unrelated to subduction typically have mantle B-isotope values. These systematics are likely uniform and would apply to the Archean as well, given that Archean seawater also appears to exhibit isotopically heavy B. The B isotope system may thus be used to investigate the presence of subducted or otherwise surface-derived material in Archean granitoids. To this end, B isotopes were analyzed for a geographically and temporally spread sample set of pristine TTGs and related granitoids (n=45, from 9 different Archean terranes covering an age range of 3.78 to 2.68 Ga). This is a considerably larger and more geographically spread sample set than a B-isotope pilot study on TTGs (Smit et al., 2019), and may as such provide more globally representative results. The B isotope signature of TTGs seem to diversify over time, diverging more from mantle-derived values starting between 3.3 and 2.9 Ga. TTGs younger than 2.9 Ga exhibit up to δ11B = +10.5 ± 0.2‰, and 48% of the samples have δ11B values heavier than depleted mantle, whereas this is 18% for TTGs older than 3.3 Ga. The B isotope signature additionally diversifies with decreasing K2O/Na2O and La/Sm. Boron isotope compositions do not correlate with geochemical or petrological proxies for (post-)magmatic processes, such as weathering, metamorphism, hydrothermal alteration, or the loss of magmatic fluids, and therefore seem to be at least not significantly altered by these processes. Instead, isotopically heavy B in TTGs may be explained by the addition of a sodic and 11B-rich contaminant into the TTG source. These contaminant characteristics point to seawater-altered oceanic crust, possibly introduced to the TTG source through subduction. If this is correct, the temporal trend observed in the δ11B values in TTGs may reflect a shift from local and episodic to global and systematic subduction of oceanic crust in the Mesoarchean.

Smit, M.A. et al., 2019, Formation of Archean continental crust constrained by boron isotopes: Geochemical Perspectives Letters, doi:10.7185/geochemlet.1930.

How to cite: Goumans, J., Smit, M., and Musiyachenko, K.: Boron isotopes in global TTGs trace the increase in deep crustal recycling in the Mesoarchean  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12762, https://doi.org/10.5194/egusphere-egu24-12762, 2024.

EGU24-12921 | Posters on site | GD3.1 | Highlight

Earth’s early tectonic modes and implications for habitability 

Peter Cawood and Priyadarshi Chowdhury

Tectonic mode manifests how a planet’s interior is cooling, and it encompasses all the geological activities (e.g., magmatism, deformation, metamorphism, sedimentation) that characterize the planetary body. Tectonic processes exert first-order control on factors key to planetary habitability (e.g., Southam et al., 2015). For example, tectonic mode controls the long-term prevalence of surface oceans, the sustenance of physicochemical conditions (e.g., temperature) favourable for metabolic activity, fluxing of elements in and out of the planet’s interior and thereby, the availability of bio-essential nutrients (e.g., C, O, H, N, P, S) (Cockell et al., 2016). However, all tectonic modes do not regulate these processes efficiently. For example, stagnant-lid mode restricts heat and material exchange between a planet’s interior and surficial reservoirs compared to plate tectonics. Further, certain factors determining a planet’s tectonic mode – like internal heat budget, mechanical behaviour of rocks, and volatile content – can vary with time, leading to the prevalence of different tectonic modes during planetary evolution. Thus, a planet’s habitability is critically intertwined with its tectonic evolution.

Modern Earth is the only known planet with plate tectonics, felsic crust, and life. Plate tectonics has resulted in a Goldilocks environment for long-term habitability via chemical cycling across the Earth system, regulating temperature through the carbonate-silicate cycle, sustaining oceans at the surface, and developing bimodal hypsometry with emergent felsic crust releasing bio-essential minerals through weathering and erosion. This has resulted in diverse habitats facilitating life’s complex phylogenetic tree. However, life initiated on Earth in the Hadean or early Archean when non-plate-tectonic modes like the stagnant- or squishy-lid modes are inferred to be prevalent (e.g., Cawood et al., 2022). Their potential to promote habitability is unknown, with few studies suggesting that they may lead to habitable conditions (e.g., Tosi et al., 2017). Nevertheless, our terrestrial planetary neighbours’ records suggest that such modes are unlikely to provide the environmental stability necessary to develop a long-term phylogenetic landscape. The geochemical cycling of elements through these modes may occur (e.g., via magmatism and episodic recycling of lithosphere) but is likely to be spatially and temporally discontinuous and limited, thereby limiting the supply of bio-essential nutrients and longevity of oceans on a planetary surface. As such, these modes inhibit a surficial environment in long-term dynamic equilibrium, leading to inhospitable habitats either through the development of a run-away greenhouse (e.g., Venus) or the loss of early atmosphere and oceans to space (e.g., Mars).

Thus, the tectonic evolution of Earth and its resultant habitability are a predictable consequence of its position, composition, size, and heat energy within the solar system. These conditions may serve as a template to search for exoplanet habitability; however, a degree of unpredictability will remain in knowing whether a similar set of planetary criteria would produce the same outcome.

References:

Cawood et al., 2022. Reviews of Geophysics, 60, e2022RG000789

Cockell et al., 2016. Astrobiology, 16(1), pp.89-117.

Southam et al., 2015. Planets and Moons, 10, pp.473-486.

Tosi et al., 2017. Astronomy & Astrophysics, 605, p.A71.

How to cite: Cawood, P. and Chowdhury, P.: Earth’s early tectonic modes and implications for habitability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12921, https://doi.org/10.5194/egusphere-egu24-12921, 2024.

The Limpopo Belt of southern Africa is a classical Paleoproterozoic orogenic belt that is believed to have resulted from the collision between the Kaapvaal and Zimbabwe Cratons. Previous studies have primarily focused on geochronology, petrology, and geochemistry of different rock assemblages, resulting in a general tectonic framework indicating at least two significant tectonothermal events from Mesoarchean to Paleoproterozoic. However, the spatial and temporal relationships between these events, as well as their overall structural patterns in the field, are poorly understood. The Central Limpopo Belt contains the best lithological exposures of different ages, making it the most promising area for detailed structural mapping and analysis, and for gaining a better understanding of these issues.
Based on the detailed field-based structural analyses, four generations of deformation were identified. The earliest D1 deformation is characterized by the penetrative S1 foliations only preserved within the 3.6-3.4 Ga anorthosites that now occur sporadically as xenoliths or boudins in the highly deformed 2.9-3.3 Ga Sand River gneiss. S2 are penetrative gneissic foliations that were extensively developed in the Sand River gneiss and were intensively superimposed by subsequent deformations into tight to isoclinal folds. After restoration of their attitude, S2 foliations strike NW-SE and dip steeply to SW at high angles, indicating that the D2 deformation experienced a roughly NE-SW-oriented compression between 2.9-2.6 Ga. D3 deformation resulted from significant NW-SE-oriented compression that intensively superimposed the earlier S2 fabrics into vertically inclined isoclinal folds and tectonites S3-L3. Strain measurements on these tectonites indicate that all pre-existing rock assemblages were stretched or sheared along the vertical orientation, resulting in the development of numerous sheath folds in the Sand River gneiss and 2.6-2.7 Grey gneiss. Associated with the zircon ages from anatexis melts, the D3 deformation most likely occurred at 2.1-2.0 Ga. SHRIMP U-Pb zircon age dating recorded these two metamorphic ages of ~2.6 Ga and 2.0 Ga on a single zircon of the foliated Sand River gneiss. A regional large scale inclined open fold F4 gently refolded the D1-D3 fabrics and marked the final deformation of the Central Limpopo Belt, occurring sometime after ~2.0 Ga. 
Detailed structural data of this study, in combination of available geochronological and metamorphic data lead us to propose that the ~2.65 Ga and ~2.0 Ga tectonothermal events occurred under different tectonic environments. The ~2.65 Ga tectonothermal event developed coevally with D2 deformation and high-grade metamorphism during the NE-SW collisional event. In contrast, the ~2.0 Ga tectonothermal event occurred during a NW-SE-oriented collisional event between the Kaapvaal and Zimbabwe Cratons, resulting in the formation of the major Limpopo tectonic linear belt seen today.

Acknowledgement
This work was financially supported by the National Natural Science Foundation of China (42025204) and National Key Research and Development Program of China (No. 2023YFF0803804).

 

How to cite: Zhang, J., Brandl, G., Zhao, G., Liu, J., and Zhao, C.: Deciphering a complex Neoarchean-Paleoproterozoic collisional history between the Kaapvaal and Zimbabwe Cratons: new constraints from polyphase deformation of the Central Limpopo Belt, southern Africa , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14565, https://doi.org/10.5194/egusphere-egu24-14565, 2024.

EGU24-16380 | ECS | Orals | GD3.1

Linking early Earth’s internal and external reservoirs: a change in oxygen fugacity of sub-arc magmas across the Great Oxidation Event 

Hugo Moreira, Craig Storey, Emilie Bruand, James Darling, Mike Fowler, Marine Cotte, Edgar E. Villalobos-Portillo, Fleurice Parat, Luís Seixas, Pascal Philippot, and Bruno Dhuime

Plate tectonics exerts a first-order control on the interaction between Earth’s reservoirs. Atmospherically-altered surface materials are recycled to the mantle via subduction, while volatiles from the mantle are liberated to the atmosphere via volcanism. This cycle regulates much of Earth’s climate, ocean levels and metallogenetic processes within the continental crust. However, the interplay between Earth’s atmospheric changes and the geochemical evolution of mantle-derived magmas has remained obscure for the ancient geological history. This has led to multiple conflicting models for the crustal evolution in the early Earth.

A time-integrated evolution of the mantle-crust-atmosphere-hydrosphere interaction is yet to be fully established. For instance, secular change of the ocean and atmosphere system is evident from several proxies but the feedback of these changes to magmatic and geochemical processes in the lithosphere remain unclear. Moreover, no clear consensus has been reached on the timing of modern-style plate tectonic initiation and the evolution of net growth of the continental crust.

To explain overt and cryptic global trends in the geochemistry of magmatic rocks, a better understanding of mineral reactions and how these control trace element evolution in magmas at the lithosphere-scale is paramount. For example, the elemental and isotopic composition of apatite inclusions hosted by zircon offers a way to better understand the evolution of magmas and, to some extent, the nature of magma sources. These proxies rely on the robust data acquisition of other isotope systems with different geochemical behaviour, such as U-Pb and Lu-Hf analyses in the host zircon crystal.

A combination of methods and proxies including the elemental composition of apatite via EPMA and the oxygen fugacity based on sulphur speciation via μ-XANES of apatite inclusions was applied to ancient sub-arc magmas formed in regions akin to modern subduction zones. These magmas share a common mantle source but crystallised more than 200 million years apart (at 2.35 and 2.13 billion years ago). Importantly, they bracket the Great Oxidation Event, when atmospheric oxygen levels increased by five orders of magnitude, causing a permanent and dramatic change in Earth’s surface chemistry. As such, these sub-arc magmas were investigated as potential tracers of the interaction between Earth’s atmosphere and the mantle.

The information from several inclusions from co-magmatic rocks can then be interpreted in the light of U-Pb, Lu-Hf, trace elements and oxygen isotope analyses of the host zircon grains. Altogether, the results show a shift in oxygen fugacity of sub-arc magmas across the Great Oxidation Event. The change in oxygen fugacity is thought to be caused by recycling into the mantle of sediments that had been geochemically altered at the surface by the increase in atmospheric oxygen levels. This study opens a wide window of opportunities for the time-integrated investigation of the interaction between atmosphere and oceans with the evolving terrestrial mantle.

How to cite: Moreira, H., Storey, C., Bruand, E., Darling, J., Fowler, M., Cotte, M., Villalobos-Portillo, E. E., Parat, F., Seixas, L., Philippot, P., and Dhuime, B.: Linking early Earth’s internal and external reservoirs: a change in oxygen fugacity of sub-arc magmas across the Great Oxidation Event, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16380, https://doi.org/10.5194/egusphere-egu24-16380, 2024.

EGU24-18408 | Orals | GD3.1

Archean continental crust formed by melting mafic cumulates 

Matthijs Smit, Kira Musiyachenko, and Jeroen Goumans

Large swaths of juvenile crust with tonalite-trondhjemite-granodiorite (TTG) composition were added to the continental crust from about 3.5 billion years ago. Although TTG magmatism marked a pivotal step in early crustal growth and cratonisation, the petrogenetic processes, tectonic setting and sources of TTGs are not well known. Part of this issue is the general difficulty in disentangling the chemical effects of fractional crystallization and partial melting, which impedes constraining primitive melt compositions and, by extension, investigating source-rock lithology and composition. To investigate these aspects, we assessed the composition and petrogenesis of Archaean TTGs using high field-strength elements that are fluid immobile, uniformly incompatible, but differently compatible between various residual minerals. The Nb concentrations and Ti anomalies of TTGs show the overwhelming effects of amphibole and plagioclase fractionation and permit constraints on the composition of primary TTGs. The latter are relatively incompatible element-poor and characterised by variably high La/Sm, Sm/Yb and Sr/Y, and positive Eu anomalies. Differences in these parameters do not represent differences in melting depth, but instead indicate differences in the degree of melting and fractional crystallisation. Primary TTGs formed by the melting of rutile- and garnet-bearing plagioclase-cumulate rocks that resided in the roots of mafic proto-continents. The partial melting of these rocks likely was part of a causal chain that linked TTG magmatism to the formation of sanukitoids and K-rich granites. These processes explain the growth and differentiation of the Archean continental crust, without requiring external forcing such as meteorite impact or the start of global plate tectonics.

How to cite: Smit, M., Musiyachenko, K., and Goumans, J.: Archean continental crust formed by melting mafic cumulates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18408, https://doi.org/10.5194/egusphere-egu24-18408, 2024.

EGU24-19222 | ECS | Posters on site | GD3.1

Petrogenetic and Geochemical studies of Sittampundi Anorthosite Complex, Southern Granulite Terrain, India. 

Amandeep Kaur, Rajagopal Krishnamurthi, and Nachiketa Rai

The Sittampundi Anorthosite complex (SAC), in the Southern Granulite terrain of Peninsular India, is a layered Archean anorthosite comprising gabbroic rocks at the base overlain by leucogabbros and anorthosites interlayered with well-developed massive chromitites. The complex has been subjected to high-pressure granulite facies (800-900°C and 11-14 Kbar) metamorphism and later retrogressed to amphibolite-facies metamorphism (550-480°C and 5.5-4.5Kbar) during exhumation (Chatterjee et al., 2022). Detailed petrography, mineral chemistry as well as major and trace element geochemistry have been used to constrain its petrogenesis and geodynamic setting.

The presence of highly calcic plagioclase and igneous amphibole indicates that magma was quite hydrous in nature. Chromites are Fe-Al rich in nature, and on the differentiation diagram, they plot near to podiform chromites and supra-subduction zone setting. Geochemical trends in major and trace elements indicate that the gabbro, leucogabbro and anorthosites were derived from the fractionated magma. However, the mineral assemblage and chromite chemistry in chromitite indicate they formed due to magma mixing.  Based on experimental studies, the composition of plagioclase limits the pressure to 2-3kb and depth of crystallization to approximately 7-11 kilometres. The findings of this study indicate the hydrous magma parental to SAC originated in a subduction zone setting in the Neoarchean.

How to cite: Kaur, A., Krishnamurthi, R., and Rai, N.: Petrogenetic and Geochemical studies of Sittampundi Anorthosite Complex, Southern Granulite Terrain, India., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19222, https://doi.org/10.5194/egusphere-egu24-19222, 2024.

EGU24-19385 | Orals | GD3.1 | Highlight

The conceptual model of the formation of Earth’s habitability 

Yun Liu

The difficulty in direct differentiation of the felsic crustal components from Earth’s mantle peridotite leads to a requirement for the presence of a large amount of hydrated mafic precursor of TTG in Earth’s proto-crust, the origin of which, however, remains elusive. The mafic proto-crust may have formed as early as  4.4 Ga ago as reflected by the Hf and Nd isotopic signals from Earth’s oldest geological records, i.e., zircons. The Archean continents, primarily composed of the felsic tonalite–trondhjemite–granodiorite (TTG) suite, were formed or conserved since  3.8 Ga, with significant growth of the continental crust since  2.7 Ga. Such a significant time lag between the formation of the mafic proto-crust and the occurrence of felsic continental crust is not easily reconciled with a single-stage scenario of Earth’s early differentiation. 
Here, inspired by the volcanism-dominated heat-pipe tectonics witnessed on Jupiter’s moon Io and the resemblances of the intensive internal heating and active magmatism between the early Earth and the present-day Io, we present a conceptual model of Earth’s early crust-mantle differentiation and the formation of habitability, which involves the tremendous heat obtained by the Moon-forming giant impact. It  forces Earth to choose an Io-like tectonics, which can efficiently dissipate heat and extract a mafic proto-crust from the early mantle, then followed by an intrusion-dominating regime that could account for the subsequent formation of the felsic continents as Earth cools. The episodic heat-pipe tectonics destroy most of rocks formed during Hadean era. The cool and hard rock layer formed due to the heat-pipe tectonics is essential for the formation of habitability of the earth. By this way, the required conditions by a habitable Earth, e.g., adequate surface temperature, aqueous sphere, and towering mountains, etc., would be appeared within a surprisingly short time. Therefore, the Moon-forming giant impact is the most important reason to make a habitable Earth. It not only brought tremendous heat into Earth and forced Earth to choose the volcanism-dominated heat-pipe tectonics but also completely destroyed the proto-atmosphere to avoid over-heated situations occurred like that of Venus at present. 

How to cite: Liu, Y.: The conceptual model of the formation of Earth’s habitability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19385, https://doi.org/10.5194/egusphere-egu24-19385, 2024.

EGU24-21184 | Orals | GD3.1

A widespread, short-lived, off-craton subduction source for hidden crustal growth in Earth’s infancy 

Eric Vandenburg, Oliver Nebel, Peter Cawood, Fabio Capitanio, Laura Miller, Marc-Alban Millet, and Hugh Smithies

The scarce geological record of Earth’s infancy, particularly before 3 billion years ago (Ga), is restricted to cratons, many of which likely originated as volcano-plutonic plateaus in a non-mobile lid geodynamic regime. However, this scarcity is at odds with the significant volumes of continental crust at 3 Ga that multi-proxy models of mantle depletion and crustal growth predict. This challenges the notion that plateau-type cratonic nuclei represent the predominant tectonomagmatic settings operating on the early Earth. Reconciling this paradox necessitates a “silent majority” of missing off-craton Archean crust of an uncharacterized affinity.

To investigate a potential rare remnant example of an Archean crust constructed away from cratonic nuclei, we report major and trace-element chemostratigraphic data from the 3.1 Ga Whundo Group of the Pilbara Craton, investigating the petrogenetic processes related to its formation. These data reveal three magmatic cycles of intercalated supracrustal successions comprising six groups: tholeiites, boninites, calc-alkaline BADR (basalt-andesite-dacite-rhyolite), high-magnesium ADR (including a subset of transitionally adakitic affinity), Nb-enriched basalts (NEB), and boninite-calc-alkaline hybrids. Th/Yb-Nb/Yb, Gd/YbN-Al/TiN, and Nd isotope systematics are inconsistent with contamination by felsic basement characteristic of cratonic cores, suggesting eruption onto thin, juvenile lithosphere that was only later incorporated into the Pilbara Craton.

How to cite: Vandenburg, E., Nebel, O., Cawood, P., Capitanio, F., Miller, L., Millet, M.-A., and Smithies, H.: A widespread, short-lived, off-craton subduction source for hidden crustal growth in Earth’s infancy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21184, https://doi.org/10.5194/egusphere-egu24-21184, 2024.

Measuring the topographic relief evolution over hundreds of thousands to million-year timescales remains challenging. Current approaches use a mix of basin stratigraphy, numerical modelling of terrestrial cosmogenic nuclide (TCN) exposure ages on strath terraces, and exhumation histories based on thermochronology or drainage basin evolution. Yet, even a combined mix of these methods is incapable of quantifying the rate changes with precisions needed to differentiate climate from tectonic drivers over multiple glacial cycles and longer timescales.

The recently conceived muon-paleotopometry (MPT) approach is tailored to close the methodological gap of determining relief generation. MPT exploits the dependence of cosmic ray muon flux on crustal shielding depth. The spatial concentration pattern of multiple muon-induced TCN measured along a near-horizontal transect under valleys and peaks relates directly to the history of changes (positive or negative) in crustal thickness. MPT allows paleotopometry measurements above the sample datum over an isotope-specific monitoring duration. By sampling at depths of hectametres, long-lived TCN (e.g., 10Be, 26Al) are not sensitive to minor short-term (<105-yr) changes owing to cut and fill terraces or transgressions. For instance, the horizontal samples will have similar muon production histories. At this depth, only fast muon interactions and radiogenic or nucleogenic pathways are likely, and only high-energy cosmic ray particles can penetrate, dodging variations in geomagnetic and solar effects and simplifying the interpretation of concentrations along the transect.

We provide an overview of this new method, starting with the theoretical concept, the encouraging proof-of-concept results by Dalhousie (M. Soukup, Hon. Thesis, 2017), the laboratory needs for measuring low TCN concentrations at great depths (>150 m) and update on the progress for the current large-scale relief investigation of the European Alps.

How to cite: Raab, G., Gosse, J., and Hidy, A.: Conceptual proof, current application, and lab procedures to quantify crustal thickness variations with muon paleotopometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1067, https://doi.org/10.5194/egusphere-egu24-1067, 2024.

In contrast to the mountainous topography and high relief of the eastern Tauern window, the adjacent Nock Mountains (Gurktal Alps, Austria) are characterized by hilly topography, lower relief and rounded summits with elevations of ca. 2000 m. Although the unusual landforms in the Nock Mountains have long been recognized (Hejl, 1997; Frisch et al., 2000, and references therein), little is known about rates of landscape evolution in this area, which was deglaciated ~15 ka ago (Wölfler et al., 2022). Here we present a new set of 16 catchment-wide erosion rates from the Nock Mountains derived from cosmogenic 10Be concentrations in stream-sediment samples. Samples from 10 major streams that drain the Nock Mountains toward the Mur-Mürz valley, the Katschberg-Lieser valley and the Drau valley range between ~130 and ~300 mm/ka. Smaller subcatchments with low relief located in the upper part of the larger catchments erode at lower rates between ~80 and ~160 mm/ka. A comparison between 10Be-derived erosion rates and exhumation rates obtained from low-temperature thermochronology and thermokinematic modelling reveals that short-term and long-term erosion rates are remarkably similar. In the central Nock Mountains, 10Be-derived erosion rates of 110-160 mm/ka are similar to the long-term exhumation rate of ~160 m/Ma since ~34 Ma (Wölfler et al., 2023). The southern Nock Mountains (Millstatt Complex) show higher short-term erosion rates of 170-300 mm/ka and also a higher long-term exhumation rate of ~270 m/Ma since 18 Ma (Wölfler et al., 2023). The similarity between short-term and long-term erosion rates suggests that the pace of erosion in the Nock Mountains did not change significantly during the late Cenozoic. A comparison of our data with 10Be erosion rates from the eastern Tauern Window (>500 m/Ma) and the Lavanttal Alps (<125 m/Ma) (Dixon et al., 2016; Delunel et al., 2021), which are located west and east of the Nock Mountains, respectively, reveals that erosion rates in the Eastern Alps decrease from west to east.

  • References
  • Delunel R, Schlunegger F, Valla PG, Dixon J, Glotzbach C et al. (2020) Earth-Sci. Rev. 211:103407.
  • Dixon JL, von Blanckenburg F, Stüwe K, Christl M (2016) Earth Surf. Dyn. 4:895909.
  • Frisch W, Székely B, Kuhlemann J, Dunkl I (2000) Zeitschr. f. Geomorph. 44:103–138.
  • Hejl E (1997) Tectonophysics 272:159–173.
  • Wölfler A, Hampel A, Dielforder A, Hetzel R, Glotzbach C (2022) J. Quat. Sci. 37:677-687.
  • Wölfler A, Wolff R, Hampel A, Hetzel R, Dunkl I (2023) Tectonics 42:e2022TC007698.

How to cite: Hampel, A., Wölfler, A., Wolff, R., and Hetzel, R.: 10Be-derived catchment-wide erosion rates from the Nock Mountains (Gurktal Alps, Austria): comparison with thermochronological data and implications for landscape evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1362, https://doi.org/10.5194/egusphere-egu24-1362, 2024.

EGU24-4640 | Orals | TS4.3 | Highlight

New constraints on the Neo-Tethyan carbon cycling and its forcing of early Cenozoic climate 

Pietro Sternai, Sébastien Castelltort, Pierre Bouilhol, Lucas Vimpere, Léa Ostorero, Mubashir Ali, Luca Castrogiovanni, Bram Vaes, and Eduardo Garzanti

Cenozoic climate trends are classically ascribed to variations of the geological carbon cycle related to Neo-Tethyan geodynamics. It is widely agreed that the collision of India and Arabia with Asia and associated mountain uplift enhanced erosion and global silicate weathering rates, ultimately driving post-50 Ma climate cooling. Cenozoic climate trends, however, involve major events of global warming in the early Paleogene (~60-50 Ma), a period that preceded rapid mountain uplift by about 30 Ma and that was characterized by a climax of arc magmatism profoundly affecting the surface CO2 budget and consequently climate. We present new measurements of mercury and carbon-isotope anomalies documented in the sedimentary archive, together with pre-eruptive CO2 budgets of Neo-Tethyan magmas encompassing the India-Asia and Arabia-Asia collision. We also show new forward modeling of the Neo-Tethyan geodynamics and inverse modeling of the Cenozoic surface CO2 budget which, tied to these new observational constraints, allow us to quantify magmatic CO2 emissions associated with the collision of India and Arabia with Eurasia. We demonstrate through such comprehensive and interdisciplinary approach that CO2 emissions associated with magmatic pulses induced by subduction of Neo-Tethyan lithosphere as well as of Indian and Arabian passive-continental-margin successions exerted a primary control on early Cenozoic climate changes.

How to cite: Sternai, P., Castelltort, S., Bouilhol, P., Vimpere, L., Ostorero, L., Ali, M., Castrogiovanni, L., Vaes, B., and Garzanti, E.: New constraints on the Neo-Tethyan carbon cycling and its forcing of early Cenozoic climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4640, https://doi.org/10.5194/egusphere-egu24-4640, 2024.

EGU24-5514 | ECS | Orals | TS4.3

Dynamic Evolution of the Northern Carnarvon Basin: An Integrated Kinematic Approach 

Patrick Makuluni, Juerg Hauser, and Stuart Clark

The geological histories of passive margin basins are dominated by tectonically induced vertical and lateral motions that control sediment transport and the development and distribution of resource systems within the basins. However, the upward (uplift and exhumation), downward (burial and subsidence) and lateral (extension, rifting and potential inversion) motions are rarely analysed together. Exploration models built from basin evolution models that include only the vertical dimension may contain larger uncertainties than those that combine lateral and vertical motions. Based on a case study, our research suggests that the combination of analyses can improve the accuracy of basin evolution models and help optimise exploration models. 

Here, we present a case study for the basin evolution model for the Northern Carnarvon Basin that incorporates data from such a combined vertical and lateral motion analysis. Backstripping and decompaction techniques were used to analyse subsidence in more than 200 wells to build the basin’s subsidence and sediment evolution maps. These maps were then used to analyse lateral motions associated with the intraplate rift development in the region. In parallel, we analysed exhumation using compaction and vitrinite reflectance analysis techniques on porosity, sonic logs and paleotemperature data from 210 wells. Our combined analyses revealed seven critical periods of basin development from the Triassic to the present. The Triassic Period was dominated by thermal subsidence and sedimentation within the south-western parts. High subsidence (~ 90 m/Ma) and sedimentation were dominant in the Early and Mid-Jurassic, coinciding with the intraplate rifting of up to ~8 mm/yr, which produced the major sub-basins in the southern and southeastern parts of the basin. This was followed by Callovian exhumation that removed up to 1500 m of sediments from the western part of the basin. The Cretaceous was dominated by rifting and breakup-related subsidence, truncated by exhumation episodes that removed up to 1000 m of sediment thickness in the southeastern parts of the basin. In the Cenozoic, the basin experienced subduction-related tilting that exhumed the southern part while the northeastern parts subsided. Our study has shown that integrating the vertical and lateral motions presents a more accurate and complete basin evolution model with the potential for improving the optimisation of basin exploration.

How to cite: Makuluni, P., Hauser, J., and Clark, S.: Dynamic Evolution of the Northern Carnarvon Basin: An Integrated Kinematic Approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5514, https://doi.org/10.5194/egusphere-egu24-5514, 2024.

EGU24-8880 | ECS | Posters on site | TS4.3

Tectonic driving mechanism of Quaternary rock-uplift and topographic evolution in the northern-central Apennines from linear inversion of the drainage system 

Simone Racano, Peter van der Beek, Claudio Faccenna, Victor Buleo Tebar, Domenico Cosentino, and Taylor Schildgen

The study of rock-uplift variations in time and space can provide insights into the processes driving the topographic evolution of mountain belts. The Apennine mountain chain of Italy, one of the more recently developed mountain belts in the Mediterranean region, has undergone a strong Quaternary rock-uplift phase, particularly in the north-central sector, which has shaped the present-day topography. It has long been recognized that drainage systems can record temporal and spatial variations in rock-uplift rates. Specifically, in detachment-limited systems with simple settings (e.g., no significant variations in drainage area over time, and catchments mostly draining perpendicular to regional structures), river profiles can be inverted to reconstruct their history of rock uplift. In this study, we present linear inversions of river profiles from 28 catchments along the eastern flank of the northern-central Apennines. These results are calibrated to infer rock-uplift rates by estimating the value of an erodibility parameter (K) from short-term incision rates and catchment-averaged erosion rates obtained from cosmogenic-nuclide data. Different approaches with constant and variable K have been applied to produce the rock-uplift model that best fits independent geochronological constraints about the uplift of the Apennine belt. Our findings suggest a spatially and temporally variable rock-uplift event that started around 2.5 to 3 Ma, following the last compressional orogenic phase and coinciding with the onset of extension. Furthermore, this rock-uplift pulse migrated southward at a rate of approximately 115 km/Myr. The highest rock-uplift rates (higher than 1.2 km/Myr) are observed in the region encompassing the highest Apennine massifs, such as the Laga Massif and the Gran Sasso Range. These results align with previous studies on Apennine paleoelevations, and they are consistent with numerical models and field evidence from other regions exhibiting rapid rock-uplift pulses and the migration of uplift related to slab break-off. Our results support the hypothesis of a break-off of the Adria slab under the central Apennines and its southward propagation over the last few million years.

How to cite: Racano, S., van der Beek, P., Faccenna, C., Buleo Tebar, V., Cosentino, D., and Schildgen, T.: Tectonic driving mechanism of Quaternary rock-uplift and topographic evolution in the northern-central Apennines from linear inversion of the drainage system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8880, https://doi.org/10.5194/egusphere-egu24-8880, 2024.

EGU24-8980 | Orals | TS4.3

Mechanisms and effects of Tarim rotation: 3-D thermo-mechanical modeling 

Qihua Cui, Pengpeng Huangfu, and Zhong-Hai Li

The rotational of rigid blocks within continental interiors, distant from plate convergence boundaries, represents a peculiar phenomenon with unclear dynamics. The Tarim block, characterized as a rigid Precambrian entity in Central Asia, is surrounded by the Tibetan–Pamir plateau to the south and the Tian Shan mountains to the north. Geophysical data strongly indicate a significant clockwise rotation of the Tarim block during the Cenozoic era. Simultaneously, distinctive deformation patterns and associated topographic responses are observed between the western–central and eastern Tian Shan regions. The intricate relationship among the India-Asia collision, Tarim's rotation, and Tian Shan's responses remains insufficiently constrained. In this study, we constructed a series of large-scale, high-resolution 3-D numerical models to study the mechanisms and effects of Tarim rotation. Our model results reveal that the collision between the advancing Indian lithosphere and the southwestern rim of the Tarim block triggers a clockwise rotation of the Tarim block. Subsequently, this rotation induces varied deformation responses along the strike of Tian Shan—resulting in heightened compression and significant uplift in central Tian Shan due to convergence, while eastern Tian Shan experiences less compression and moderate uplift attributed to divergence. Thus, the Tarim rotation emerges as an essential linkage, connecting the evolutionary dynamics of the Tibetan plateau with the far-reaching activation of Tian Shan. This research provides valuable insights into the geodynamic processes shaping continental interiors, with implications for broader tectonic frameworks and technological applications.

How to cite: Cui, Q., Huangfu, P., and Li, Z.-H.: Mechanisms and effects of Tarim rotation: 3-D thermo-mechanical modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8980, https://doi.org/10.5194/egusphere-egu24-8980, 2024.

EGU24-9089 | Posters on site | TS4.3

Variscan olistostromes and the geological history they tell… unraveling the tectonic evolution of the Pangea supercontinent  

Ícaro Dias da Silva, Manuel Francisco Pereira, Emílio González-Clavijo, José Brandão Silva, and Lourenço Steel Hart

Mass transport deposits or olistostromes, carrying large-sized blocks or olistoliths, are related to active and passive margin tectonics. Information on how they are produced is critical to understanding the tectonically driven topographic dynamics in the source areas, and the tectonic evolution of sedimentary basins and their shoulders. The geological record of these mass transport deposits is commonly well preserved onshore, in orogenic regions where continental margins uplift was influenced by the gradual movement of continents.

The Iberian Massif is one of the World’s key areas for studying ancient orogenies, like the Late Paleozoic Variscan belt, to understanding the formation of olistostromes, and developing provenance studies on such complex tectonic fold and thrust belts. Structural relations between the basement and overlying Mississippian synorogenic marine basins were recently examined in the lower plate (Gondwana side) of the Variscan collisional orogeny in Iberia. The stratigraphy of these Variscan synorogenic basins is quite complex and includes: a) sedimentary melánges (e.g., related to submarine mudflows and turbidites) that carried or were formed by different-sized blocks of different age metamorphic, volcanic, siliciclastic and carbonated rocks derived from the nearby pre-Mississippian basement; b) partially or completely dismantled Devonian and/or Mississippian carbonate platforms; and c) syn-sedimentary bimodal calc-alkaline volcanism. Geochronology data show that Mississippian sedimentation and volcanism occurred simultaneously with regional high temperature-low pressure metamorphism, associated with the formation of gneiss domes, bounded by extensional shear zones and faults, during crustal thinning and plutons emplacement. Mapping of shear zones and faults on the Iberian Variscan basement provided crucial information for better comprehending Mississippian synorogenic basin architecture. Our study demonstrates that there is a spatial and temporal relationship between the generation of olistostromes (including large olistoliths) and the development of first-order extensional structures in the pre-Mississippian basement.

Given that the collision between Laurussia and Gondwana had already occurred, it seems that these Mississippian synorogenic basins were not formed in a foreland, backarc, or forearc setting related to the subduction of the Rheic oceanic lithosphere, and thus, other geodynamic hypotheses need to be set. Two tectonic models have been discussed to explain the occurrence of a significant thermal anomaly beneath the lower plate (Gondwana side) and the formation of the Mississippian synorogenic basins in Iberia: Model A) considers that the roll-back of the lower plate was responsible for the formation of an orogenic plateau, the lateral flow of partially molten orogenic roots, and peel-back tectonics, after the subduction of the Rheic Oceanic lithosphere under the upper plate (Laurussia side) and the subsequent continental collision. In this case, the Mississippian synorogenic basins would be of peel-back type; Model B) invokes the subduction of the Paleotethys oceanic lithosphere beneath the Variscan collisional orogen, and the Mississippian synorogenic basins would be of backarc type but developed later than the Rheic Ocean closure.

This work was supported by FCT I.P./MCTES (Portugal) through national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020), LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020), DL57/2016/CP1479/CT0030 (https://doi.org/10.54499/DL57/2016/CP1479/CT0030), FCT/UIDB/ 04683/2020-ICT and by the Spanish Agency of Science and Technology MCIN/AEI/10.13039/501100011033 and TED2021- 130440B-I00

How to cite: Dias da Silva, Í., Pereira, M. F., González-Clavijo, E., Silva, J. B., and Steel Hart, L.: Variscan olistostromes and the geological history they tell… unraveling the tectonic evolution of the Pangea supercontinent , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9089, https://doi.org/10.5194/egusphere-egu24-9089, 2024.

EGU24-10486 | Posters on site | TS4.3

Central Anatolian (Turkey) and Aegean (Greece) soil carbonate δ18O values reveal Late Miocene surface uplift of the southern plateau margin and post−Miocene aridification of the northeastern Mediterranean region 

Maud J.M. Meijers, Tamás Mikes, Bora Rojay, Erkan Aydar, H. Evren Çubukçu, Thomas Wagner, and Andreas Mulch

In recent years, numerous studies focused on reconstructing the surface uplift history of the Central Anatolian Plateau (CAP) and the associated driving mechanisms such as slab breakoff, removal of lithospheric mantle, or crustal thickening (e.g. McPhee et al., 2021). The CAP forms the westward portion of the Turkish−Iranian plateau and has mostly been above sea level since ca. 41 Ma (Okay et al., 2020). Most of its present-day topography, featuring mean elevations of ca. 1.0-1.5 km, however, has been shaped since the Late Miocene (e.g. Meijers et al., 2018; Schildgen et al., 2012a,b). Perhaps the most spectacular discovery is the recognition of 2 km of surface uplift of a portion of the southern plateau margin, the Tauride Mountains, since ca. 0.5 Ma (Öğretmen et al., 2018).

Here, we provide stable isotope paleoaltimetry estimates for the Late Miocene for the southern CAP margin. The method is based on the inverse relationship between the oxygen isotopic composition (δ18O) of meteoric waters and elevation. We therefore contrast the δ18O values of age−equivalent low and (potential) high elevation soil carbonates (the δ−δ method; Mulch, 2016) from central Anatolia with published Anatolian and Aegean soil carbonate δ18O values (Böhme et al., 2017; Meijers et al., 2018; Quade et al., 1994). Our results reveal a low (ca. 0.5 km) orographic barrier between the Aegean and Mediterranean coastlines and central Anatolia at ca. 10 Ma, which increased to an elevation of ca. 1 km by ca. 8−6 Ma. This trend in increasing surface elevations during the Late Miocene is in agreement with stable isotope−derived paleoelevation estimates from Anatolian lacustrine carbonate records (Meijers et al., 2018). Given proposed post−0.5 Ma surface uplift of the southernmost plateau margin (Öğretmen et al., 2018), our results imply a phase of significant local subsidence bracketed between the latest Miocene and ca. 0.5 Ma. From the Pliocene onward, we also observe long-term trends toward higher δ18O values in soil carbonate data sets from the Aegean Sea and CAP region, which indicate increased aridification and possibly seasonality of rainfall in the region since the Pliocene. Additionally, our ‘modern’ soil carbonate records from central Anatolia underestimate the elevation of the modern Tauride orographic barrier (ca. 2.2 ± 0.5 km) at the southern plateau margin by ca. 0.5 to 1.0 km (non−linear vs. linear lapse rate, respectively). We attribute this underestimation to the mixing in of higher δ18O atmospheric moisture derived from the Black Sea compared to atmospheric moisture derived from the Mediterranean Sea during spring and early summer, a signal that is likely incorporated into soil carbonates that form at the onset of the dry summer season. Although atmospheric moisture derived from the Black Sea yields lower δ18O values than Mediterranean atmospheric moisture at sea level (Schemmel et al., 2013), the former undergoes less distillation across the significantly lower northern plateau margin (the Pontide Mountains). The presently observed mixing of Black Sea and Mediterranean Sea moisture sources might have also led to an underestimation of southern orographic barrier elevations in the geologic past.

How to cite: Meijers, M. J. M., Mikes, T., Rojay, B., Aydar, E., Çubukçu, H. E., Wagner, T., and Mulch, A.: Central Anatolian (Turkey) and Aegean (Greece) soil carbonate δ18O values reveal Late Miocene surface uplift of the southern plateau margin and post−Miocene aridification of the northeastern Mediterranean region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10486, https://doi.org/10.5194/egusphere-egu24-10486, 2024.

EGU24-11203 | ECS | Posters on site | TS4.3

What controls the migration rate of divides? Insights from morphometry and 10Be and 26Al cosmogenic nuclides analysis applied to the Vosges massif 

Bastien Mathieux, Jérôme van der Woerd, François Chabaux, Philippe Steer, Julien Carcaillet, and Thierry Perrone

The Vosges massif is a mid-altitude mountain range located northeast of France. It extends latitudinally for 250 km north of the Alps and is characterized by topographic, geological and geomorphological north-south and east-west gradients. In the south, the exhumed Paleozoic basement culminates at about 1400 m asl while in the north, river valleys incise Mesozoic sandstones with summits ranging between 400 and 700 m asl. The relief is intricately linked to the Eocene-Oligocene formation of the Rhine graben and the Mio-Pliocene deformation of the Alpine foreland. The present-day slow deformation rates in the Rhine graben, coupled with the region’s moderate seismicity characterized predominantly by strike-slip mechanisms, raise questions about the current driving forces behind the Vosges’ topographic evolution.

The evolution of drainage divides provides a window into the complex interrelations among tectonic forces, surface erosion processes and climatic influences that contribute to shaping a mountain range. In this study, we combine morphometric and cosmogenic nuclides (10Be and 26Al) analyses to assess the migration of the Vosges’ main drainage divide. Gilbert’s metrics (elevation, relief and gradient) alongside χ-index reveal a strong eastward gradient across the divide suggesting a migration away from the Rhine graben margin. To provide a quantification of this migration, a dataset of in-situ cosmogenic nuclides whose concentrations are erosion-dependent has been measured in samples collected across various segments of the divide. Cosmogenic nuclide analysis reveals a robust set of 10Be/26Al ratios falling within the steady-state denudation curve and denudation rates, ranging from 30 to 90 mm/kyr in the south and 40 to 70 mm/kyr in the north. Notably, both regions display an eastward trend in denudation, corroborating the gradient observed in the morphometric analysis.  A geometric approach was used to translate cross-differences in denudation rates and topographic gradients into migration rates of the main drainage divide, showing a westward shift of 20-70 mm/kyr in the south and 3-30 mm/kyr in the north.

Expanding our analysis, we examined the correlation between the calculated denudation rates and the hilltop curvatures derived from high-resolution DEMs (1m). A relation appears in the south, whereas no relationship has been found in the north, suggesting additional complexities in controlling morphogenetic processes. This finding allows us to use hilltop curvature as a proxy for denudation rates, particularly within mono-lithologic soil-mantled basins along the southern Vosges drainage divide. These insights offer a valuable conceptual framework for constraining numerical simulations at the mountain range scale aimed at unravelling the external forces that shape the highest Vosges relief.

How to cite: Mathieux, B., van der Woerd, J., Chabaux, F., Steer, P., Carcaillet, J., and Perrone, T.: What controls the migration rate of divides? Insights from morphometry and 10Be and 26Al cosmogenic nuclides analysis applied to the Vosges massif, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11203, https://doi.org/10.5194/egusphere-egu24-11203, 2024.

EGU24-12254 | Posters on site | TS4.3

Relief stability of western Europe middle mountains from morphometry and 10Be denudation rates: the Strengbach catchment case in the central Vosges massif 

Jérôme van der Woerd, Daniel S. Moreno Martin, Raphaël di Chiara Roupert, Bastien Mathieux, Thierry Perrone, Gilles Rixhon, Silke Merchel, Anne-Sophie Mériaux, and François Chabaux

Assessing the Quaternary topographic stability of western Europe middle mountains characterized by low tectonic activity remains challenging. We suggest to tackle this question in the Vosges – Upper Rhine Graben system where elevation reach up to 1400 m asl. This study is focused on the Strengbach catchment, that flows from the Vosges massif towards the Rhine graben, upstream of Ribeauvillé in the central Vosges. The catchment reaches 29 sq.km between 500 to 1200 m elevation. Morphometric analysis of the main trunk and tributaries is performed to constrain the areas of topographic disequilibrium along the valleys (knickpoints). 10Be cosmogenic isotope analysis in river sediments from various sites in the catchment is used to constrain the migration rates of these topographic instabilities at the millennial scale.

The morphometric analysis performed in the Strengbach catchment (catchment topography - χ-elevation profiles) provide evidence of relic topographic surfaces upstream of a 2 km-long convex knick-zone located at about 700 m. Below this zone, the catchment is deeply incised and ramified with knick-points in the tributaries at about 500 m. Above the knick-zone, fluvial incision is reduced with a high-standing knickpoint at about 950 m marking the upper section of the Strengbach stream. 10Be denudation rates points to relatively small variations along the main trunk upstream (36 ± 2 - 44 ± 3 mm/ka), while denudation rates derived from the tributaries range from 38 ± 2 mm/ka to 75 ± 5 mm/ka. We show that these variations are primarily controlled by topographic and lithologic factors, namely the presence of sandstones in the sub-catchments, characterized by higher erodibility than crystalline rocks. The 10Be cosmogenic isotope concentrations in sediments from both upstream and downstream of the knickpoints, and in the tributaries, constrain at first order the migration rate of the knickpoints along the river profile and the retreat rate of sandstone cliffs upstream some tributaries. Migration rates on the order of 100-200 m/Ma suggest that at the millennial scale, the topography is relatively stable. These data will be used to discuss the source of topographic disequilibrium present in the catchments.

How to cite: van der Woerd, J., Moreno Martin, D. S., di Chiara Roupert, R., Mathieux, B., Perrone, T., Rixhon, G., Merchel, S., Mériaux, A.-S., and Chabaux, F.: Relief stability of western Europe middle mountains from morphometry and 10Be denudation rates: the Strengbach catchment case in the central Vosges massif, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12254, https://doi.org/10.5194/egusphere-egu24-12254, 2024.

EGU24-13770 | ECS | Posters on site | TS4.3

The Northward Expansion of the Tibetan Plateau: Topographic Evidence from the Bogda Mountains—Junggar Basin Coupling system, Northwest China 

Mengyue Duan, Franz Neubauer, Jörg Robl, Xiaohu Zhou, and Moritz Liebl

Distinct Mountain–Basin coupling systems were formed during the expansion of the Tibetan Plateau into the surrounding low elevation regions in the north, northeast and east. In this study, we focus on the topographic features of the Bogda Mountains–Southern Junggar Basin coupling system on the north of the Tibeau Plateau, which influenced by the N-S orthogonal shortening caused by the uplift of the Tibetan Plateau and northward propagation of deformation away from the India-Asia collision zone. We mainly quantify the influence of uplift of the Tibetan Plateau on the formation of the Bogda Mountains–Junggar Basin coupling system by fluvial geomorphologic analysis based on the digital elevation model analysis and the optically stimulated luminescence (OSL) dating on the Dalongkou river terraces on the northern slope of Bogda Mountains. Together, these morphological analyses show that the high normalized steepness index (ksn) and knickpoints mainly distributed in the western Bogda Mountains. The normalized steepness index (ksn) gradually decreased from west to east, which indicated that the tectonic activity of the western Bogda Mountains is higher. The compiled low-temperature thermochronology data of the Bogda Mountains show a younging trend from west to east, which indicates that the western Bogda uplift started earlier than in eastern Bogda. The difference of the χ values on both sides of the Bogda Mountains is similar, which means the drainage divide of the Bogda Mountains is stable. There are five river terraces distributed on both side of the Dalongkou River. The optically stimulated luminescence (OSL) dating results show that the ages of the T2 river terrace, T3 river terrace, T4 river terrace of the Dalongkou river are 6.2±1.3 ka, 13.1±1.7 ka, and 14.2±2.5 ka, respectively. The incision rate of the Dalongkou river increases upstream from ~1.22 mm/yr close to the southern Junggar Basin, to ~2.1 mm/yr, and to ~6.33 mm/yr in front of the higher Bogda Mountains, which means that the uplift rate of the Dalongkou river increases upstream. We propose a model of upbending of central Bogda Mts. by ongoing Holocene folding, with an inflection point close to the southern boundary to the Junggar Basin. By comparing the geomorphological features of the Bogda Mountains with the North Tianshan Mountains, we conclude that the tectonic uplift intensity gradually decreased from the North Tianshan Mountains to the Bogda Mountain, as well as the gradual accelerated uplift rate of the Bogda Mountains, are influenced by the N-S orthogonal shortening caused by the uplift of the Tibetan Plateau, which is gradually decreasing from west to east.

How to cite: Duan, M., Neubauer, F., Robl, J., Zhou, X., and Liebl, M.: The Northward Expansion of the Tibetan Plateau: Topographic Evidence from the Bogda Mountains—Junggar Basin Coupling system, Northwest China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13770, https://doi.org/10.5194/egusphere-egu24-13770, 2024.

Quantifying rates and magnitudes of topographic change across timescales requires diverse observational and modeling techniques.  Low-temperature thermochronometer methods are a powerful tool for quantifying denudation rates, paleotopography, and/or the kinematic history of orogens over geologic timescales.  Parallel to thermochronometer technique development, a range of thermal, kinematic, and erosion modeling approaches are available to interpret tectonic and surface processes from thermochronometer data. However, differing thermal modelling approaches exist in the literature and often lead to the question of which approach is most appropriate, and when?

This presentation addresses the diversity of thermo-kinematic and erosion modelling approaches available to quantitatively interpret topographic change or tectonic processes from thermochronometer data. Emphasis is placed on deciphering the different approaches available and which approach is suitable for the scientific questions asked (e.g., topographic change, tectonic/faulting history, etc.) in diverse geologic settings.  Thermo-physical factors explored include the appropriate model spatial dimension (e.g., 1D, 2D, vs. 3D); the influence of model geometry on geotherms; the importance of constant basal temperature vs. flux basal boundary conditions; transient vs. steady-state geotherms, and how tradeoffs in different parameters (exhumation rate, material properties, boundary conditions) can produce similar thermochronometer ages. The presentation focuses on examples from the literature, ranging from William Thompson’s (Lord Kelvin) founding work on continental geotherms to contemporary numerical modeling approaches.

How to cite: Ehlers, T. A. and Willett, S. D.: Appropriate Thermal Modelling Approaches for Interpreting Topographic and Tectonic Change from Thermochronometer Data (Remembering the Geotherm and 200 years of Lord Kelvin’s legacy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13841, https://doi.org/10.5194/egusphere-egu24-13841, 2024.

EGU24-15024 | Orals | TS4.3

Direct evidence of drainage divide migration reveals intermittent dynamics linked to 100 kyr climate oscillations 

Liran Goren, Elhanan Harel, Tianyue Qu, Onn Crouvi, Naomi Porat, Hanan Ginat, and Eitan Shelef

It is common to assume that when there are erosion rates and slope gradients across a drainage divide, the divide is prone to migrate and change the drainage area distribution of its bounding catchments. However, direct records of divide migration are exceptionally rare. This raises the following questions: Could the assumption be wrong, and can divides sustain topographic and erosion rate asymmetry over geomorphic and geologic (104– 106 yrs) timescales? And when divides eventually migrate, is the migration driven by endogenic feedback within the basin, or by exogenic forcing, such as climate change?

To address these issues, we study a field area along the escarpments of the Dead Sea plate boundary, Israel, where direct records for divide migration are present in the form of terraces that grade opposite to the channel flow direction. These terraces are interpreted as a record of the divide’s paleo-locations, such that terraces are formed when the divide migrates inland from the edge of an escarpment, inducing drainage reversal and gradually extending the reversed channel that drains toward the escarpment.

Absolute dating of these terraces using luminesces techniques and relative dating using soil chronosequence markers reveal that the terraces become older from the present locations of the divide toward the escarpment, consistent with the interpreted process of their formation. Terrace ages show an average divide migration rate of ~1100 m myr-1 over the past ~230 kyr, supporting active divide migration over timescales of 105 yrs or shorter.

Terrace groups with similar ages indicate ~100 kyr cycles of periods of divide stalling and episodes of rapid divide migration with rates up to fourfold relative to the average rate. We use numerical simulations to explore possible drivers for the inferred divide intermittent dynamics. Simulations show that the dynamics are inconsistent with landscape evolution under uniform environmental conditions due only to internal basin dynamics. Instead, the inferred intermittency is best explained with time-dependent erosional efficiency that is sensitive to global climate change and correlates with regional paleoclimate proxies.

This study provides the first detection of divide migration rate intermittencies at timescales of 104-105 yrs, and the association between divide dynamics and changing climatic conditions. This highlights the potentially significant impact of climate changes on the plan-form evolution of drainage basins.

How to cite: Goren, L., Harel, E., Qu, T., Crouvi, O., Porat, N., Ginat, H., and Shelef, E.: Direct evidence of drainage divide migration reveals intermittent dynamics linked to 100 kyr climate oscillations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15024, https://doi.org/10.5194/egusphere-egu24-15024, 2024.

EGU24-15751 | Posters on site | TS4.3

3D interaction of tectonics with surface processes explains fault network evolution of the Dead Sea Fault 

Sascha Brune, Esther L. Heckenbach, Anne C. Glerum, Roi Granot, Yariv Hamiel, Stephan V. Sobolev, and Derek Neuharth

Releasing and restraining bends are complementary features of continental strike-slip faults. The Dead Sea Basin of the strike-slip Dead Sea Fault is a classical example of a releasing bend with an asymmetric, deep basin structure. However, the intrinsic relationship to its northern counterpart, the restraining bend that created the Lebanese mountains, remains unclear.

Here, we present 3D coupled geodynamic and landscape evolution models that include both the releasing and the restraining bend in a single framework. These simulations demonstrate that the structural basin asymmetry is a consequence of strain localization processes, while sediments control the basin depth. Local extension emerges due to strength heterogeneities and a misalignment of faults and the overall stress field in an area where regional tectonics are dominated by strike-slip motion. Furthermore, we reveal a crustal thinning and thickening pattern that intensifies with surface process efficiency. Along-strike deformation is linked through coupled crustal flow driven by gravitational potential energy which is opposed by deposition at the releasing bend and enhanced by erosion around the restraining bend. Due to the generic nature of our models, our results provide templates for the evolution of fault bends worldwide.

How to cite: Brune, S., Heckenbach, E. L., Glerum, A. C., Granot, R., Hamiel, Y., Sobolev, S. V., and Neuharth, D.: 3D interaction of tectonics with surface processes explains fault network evolution of the Dead Sea Fault, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15751, https://doi.org/10.5194/egusphere-egu24-15751, 2024.

EGU24-17337 | Orals | TS4.3

Landscape response at the edge of a tearing slab 

Jose Miguel Azañon, Jorge Pedro Galve, Daniel Ballesteros, Jose Vicente Perez-Peña, Patricia Ruano, Fernando Garcia-Garcia, and Guillermo Booth-Rea

Tearing at the edges of subducted slabs permits the migration of narrow orogenic arcs. Dynamic models predict that the active segment of subvertical tears migrates in the sense opposite subduction modifying the topography and tectonic regime along its path. However, the effects of slab tearing on surface deformation and landscape evolution, remains virtually unexplored. Here we show the landscape response to slab tearing, including drainage development and reorganization in the Betics, with analogies to the southern Caribbean arc. After approximately 400 km of slab tearing since 10 Ma the Betics show a transient topography with positive residual values over regions stripped from their subcontinental lithospheric mantle and negative anomalies outboard of the tear. The landscape evolves through crustal shortening and flexural uplift in the foreland of the active tearing segment producing land emergence and drainage development, with fluvial diversion around uplifting structures. Slab pull and orogen transverse extension inboard the active-tearing segment foster basin development followed by emergence and drainage reorganization by fluvial incision and capture. Mantle upwelling, flexural rebound and further extension affects teared regions, driving positive residual topography amplified in the footwall of extensional domes. Mantle flow around the slab drives uplift hundreds of km away from the slab edges.

How to cite: Azañon, J. M., Galve, J. P., Ballesteros, D., Perez-Peña, J. V., Ruano, P., Garcia-Garcia, F., and Booth-Rea, G.: Landscape response at the edge of a tearing slab, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17337, https://doi.org/10.5194/egusphere-egu24-17337, 2024.

EGU24-17907 | Orals | TS4.3

3D Velocity field of Romania derived from more than 20 years of continuous GPS observations 

Alexandra Muntean, Boudewijn Ambrosius, Eduard Ilie Nastase, and Ioan Munteanu

Abstract

      The Earth's surface is continuously transformed, with deep and superficial processes contributing to the present-day morphology. Evaluating the contribution of each process and interaction between tectonics, climate, and human activities is difficult, especially in areas with relatively low crustal deformation.

      With this study, we aim to better understand the tectonic and sub-surface geodynamic processes that result in (small) surface motions in Romania. We are particularly interested in the Eastern Carpathians Bending Zone (Vrancea region), where strong deep earthquakes occur. Furthermore, we are focused on the interaction between the Eurasian, and Aegean tectonic plates. For this purpose, we processed more than 20 years of cGPS data from various networks in Romania (more than 100 stations), using the GipsyX software. To put our results in a broader perspective, we also included similar results published in open-source online literature including countries around Romania. Combining all these solutions we generated a velocitiy horizontal and vertical velocity fields for this extended region. All solutions were converted to the Eurasian tectonic reference plate in the ITRF14 plate rotation model.

      We find that in general, the horizontal velocity vectors in Romania have small values, ranging from 0.0 mm/yr in the north to 1.5 mm/yr in the south, and notably, the majority of stations indicate a subtle yet significant downward motion of 1.0 -2.0 mm/yr. In contrast, to our expectations, we did not find any significant horizontal and vertical motions in the Vrancea region. The horizontal motions exhibit a strong, generally southward, and gradually increasing trend, starting south of the South Carpathians. The trend is in the direction of the tectonic plates in southeast Europe. It means that the intraplate deformation zone extends to south Romania. The observed patterns contribute to our understanding of intraplate deformation and emphasize the need for continued regional research.

Keywords: crustal deformations, GPS, geophysics, tectonics 

 

Acknowledgments

This paper was carried out within Nucleu Program SOL4RISC, supported by MCI, project no PN23360101, and PNRR- DTEClimate Project nr. 760008/31.12.2023, Component Project Reactive, supported by Romania - National Recovery and Resilience Plan

How to cite: Muntean, A., Ambrosius, B., Nastase, E. I., and Munteanu, I.: 3D Velocity field of Romania derived from more than 20 years of continuous GPS observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17907, https://doi.org/10.5194/egusphere-egu24-17907, 2024.

EGU24-18362 | ECS | Posters on site | TS4.3

The role of tectonic, volcanic, and fluvial processes as controls of Neogene intermontane basin evolution in the western Colombian Andes 

Santiago León, Claudio Faccenna, Ethan Conrad, and Víctor A. Valencia

The sediment dispersal patterns at active orogens are highly sensitive to changes in the landscape configuration triggered by the combined effects of deformation, volcanism, and geomorphological processes. Hence, reconstructing source-to-sink systems provides valuable insights into the interplay between deep-seated and surface processes as controls of the coupled development of mountain ranges and intermontane sedimentary basins.

The Oligocene-Miocene evolution of the Colombian Andes has been shaped by subduction tectonics and the collision of an oceanic terrane, which are linked to changes in the kinematics of crustal deformation and the tectono-magmatic history of continental arcs. Nevertheless, the combined effect of such processes on the growth of the Western and Central Cordilleras and the associated intermontane basins remains elusive.

Here, we use a large dataset of detrital zircon U-Pb ages from Oligocene-Pliocene strata of intermontane basins of western Colombia, and available (bio)stratigraphic and structural constraints to reconstruct: i) the regional-scale configuration of source areas and accumulation settings, ii) the sediment routing systems, and iii) the history of basin connectivity. We interpret the sediment dispersal patterns as controlled by the pulsed uplift of the Central and Western Cordilleras linked to a syn- to post-collisional transpressional tectonic regime, and to changes in the drainage network driven by intra-basinal arc-related magmatic activity

How to cite: León, S., Faccenna, C., Conrad, E., and Valencia, V. A.: The role of tectonic, volcanic, and fluvial processes as controls of Neogene intermontane basin evolution in the western Colombian Andes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18362, https://doi.org/10.5194/egusphere-egu24-18362, 2024.

EGU24-20268 | Orals | TS4.3

Discovery of lithospheric drip explains topographic rejuvenation of the Uinta Mountains, USA 

Adam Smith, Matthew Fox, Scott Miller, and Leif Anderson

Densification at the base of thickened crust drives lithospheric dripping or delamination. Mountain ranges form due to crustal thickening, and so represent locations where dripping and delamination are likely to occur. Recent studies have implicated dripping continental crust with a variety of different surface expressions, from driving surface uplift to initiating rifting, highlighting the uncertainty associated with our ability to predict the surface consequences of dripping continental crust. The Uinta Mountains in Utah formed during the Laramide orogeny, and despite this period of crustal shortening ending ~50 mya, the elevation of the range, and the form of the river networks draining the range suggest the range has undergone topographic rejuvenation. To investigate the cause of this rejuvenation, we extract map of recent surface uplift from the river networks of the Uintas, and use previously published seismic tomography to investigate the structure of the mantle beneath the range. We identify dripping lithospheric crust beneath the Uintas, and, using a simple isostatic model, are able to reconcile the observed surface uplift with a prediction of surface uplift based on isostatic compensation. The agreement between our observations and our predictions allow us to present a compelling case for delamination driven surface uplift of the Uintas, and show that simple isostatic compensation can explain the surface expressions of delaminated crust. Our observations therefore have important implications for the history of the Uinta Mountains and more generally for our understanding of the long-term evolution of the continents.

 

How to cite: Smith, A., Fox, M., Miller, S., and Anderson, L.: Discovery of lithospheric drip explains topographic rejuvenation of the Uinta Mountains, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20268, https://doi.org/10.5194/egusphere-egu24-20268, 2024.

GMPV11 – Interdisciplinary studies with a regional focus

EGU24-550 | ECS | PICO | GMPV11.1

Assessing the potential of a new widespread ignimbrite-forming eruption in Cappadocia, Central Anatolia 

Ivan Sunye Puchol, Xavier Bolos, Rengin Ozsoy, Efe Akkas, Erkan Aydar, Lorenzo Tavazzani, Manuela Nazarri, and Silvio Mollo

The Cappadocian plateau is a tectonic horst within the Central Anatolian Volcanic Province (CAVP), characterised by multiple thick and widespread ignimbrites accumulated since the late Miocene (e.g. Aydar et al., 2012). These Cappadocian ignimbrites blanketed an extensive area of at least 40,000 kmwith an estimate volume of pyroclastic material exceeding 1000 km3 (Temel et al., 1998). The source of the oldest Neogene ignimbrites still remains a subject of intense debate, as the area is primarily covered by younger volcanic products. However, it is well-known that the two youngest ignimbrites were produced by the Acigöl caldera (Druitt et al., 1995). These are the Lower Acigöl Tuff  (LAT) and the Upper Acigöl Tuff (UAT), erupted at 190 ± 11 ka and 164 ± 4 ka respectively (Schmitt et al., 2011). Post-caldera explosive volcanism continued in Acigöl until more recent times, especially in the last 25ka with the eruption of several rhyolitic tephra cones, maars and related tephra rings (Uslular et al., 2022).

Here, we propose that these monogenetic eruptions within the caldera basin may serve as precursory signals for larger caldera-forming events. Findings from a recent tephrostratigraphic investigation suggest that this series of volcanic eruptions has already occurred in Acigöl caldera as cascading events. This series includes the simultaneous emplacement of the Taskesik tephra ring and the UAT caldera-forming ignimbrite. Therefore, considering: 1) the high monogenetic volcanic activity in the last thousands of years within and outside the caldera, 2) the potential presence of eruptible magma beneath the caldera (Abgarmi et al., 2017), and 3) the increase in seismicity within the Central Anatolian Volcanic Province, the hypothetical scenario of a future caldera collapse eruption in Acigöl should not be dismissed.

This study was founded by the PÜSKÜRÜM project, a Marie Curie Action (Grant No. 101024337) funded by the European Union’s Horizon 2020.

 

Reference list:

Abgarmi, B., et al. (2017). Structure of the crust and African slab beneath the central Anatolian plateau from receiver functions: New insights on isostatic compensation and slab dynamics: Geosphere, v. 13, no. 6, p. 1774–1787, doi:10.1130/GES01509.1.

Aydar, E., et al (2012). Correlation of ignimbrites in the central Anatolian volcanic province using zircon and plagioclase ages and zircon compositions. J. Volcanol. Geoth. Res. 213, 83–97. doi:10.1016/j.jvolgeores.2011.11.005

Druitt, T.H., et al. (1995). Late-Quaternary rhyolitic eruptions from the Acıgöl Complex, central Turkey. Journal of the Geological Society (London, United Kingdom) 152, 655–667. DOI: 10.1144/gsjgs.152.4.0655

Schmitt, A. K., et al. (2011). Acigöl rhyolite field, Central Anatolia (part 1): High-resolution dating of eruption episodes and zircon growth rates. Contrib. Mineral. Pet. 162 (6), 1215–1231. doi:10.1007/s00410-011-0648-x

Uslular, G., et al. (2022). New findings on compositionally distinct maar volcanoes: A case study from Acıgöl (Nevşehir) caldera (Central Anatolia, Turkey)   . Front. Earth Sci.  DOI 10.3389/feart.2022.909951

Temel, A., et al (1998). Ignimbrites of Cappadocia (Central Anatolia, Turkey): petrology and geochemistry. J. Volcanol. Geotherm. Res. 85, 447–471. doi:https://doi.org/10.1016/S0377-0273(98)00066-3

How to cite: Sunye Puchol, I., Bolos, X., Ozsoy, R., Akkas, E., Aydar, E., Tavazzani, L., Nazarri, M., and Mollo, S.: Assessing the potential of a new widespread ignimbrite-forming eruption in Cappadocia, Central Anatolia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-550, https://doi.org/10.5194/egusphere-egu24-550, 2024.

EGU24-632 | ECS | PICO | GMPV11.1

Güzelyurt Resurgent Caldera - Cappadocia, Türkiye: The Origin of Gördeles Ignimbrite and Its Geothermal Potential  

Gökhan Atici, Erkan Aydar, İnan Ulusoy, and Orkun Ersoy

Turkey hosts various types of volcanic rocks in different areas due to evolving volcanic activity from the Miocene to the present. The Cappadocia region is one of the most prominent areas in these regions. In this study, geological and volcanological data, along with samples obtained through the anisotropy of magnetic susceptibility method (AMS), were used to determine the potential source area of Gördeles ignimbrite (ca. 6.3 My), a Miocene-aged ignimbrite found in the Cappadocia region of Central Anatolia. As a result of field observations, the Gördeles ignimbrite was divided into Lower and Upper Gördeles separated by a paleosoil layer. To the west of Güzelyurt, the largest pumice diameter was found to be 72 cm, while the lithic diameter was 33 cm in the ignimbrite. Near the village of Kayırlı, a lag breccia measuring 30 m in thickness was identified just below an 8m pyroclastic flow unit. The lag breccia contains pumices and andesites with a diameter of 70 cm. To determine paleoflow directions, 130 core samples were taken from 25 locations of the ignimbrite, and 2448 magnetic measurements were conducted using the anisotropy of magnetic susceptibility method. According to our AMS analyses, the paleoflow directions around the Güzelyurt area are distributed radially. Our magnetic fabric data, combined with field and stratigraphic information, suggests that the source area is located near Güzelyurt. The source area (the Güzelyurt resurgent caldera) spans roughly 9x9 km, and its highest point is about 2000 m. The pre-caldera lavas, situated on the eastern side of the caldera, have an elevation of about 1800 m. The caldera's lowest point is at an elevation of 1330 meters. Based on these measurements, the total subsidence amount is estimated to be 500 meters, which indicates the discharge of around 31 km3 of magma. The eruptions occurred in multiple stages and were explosive in nature. After the caldera collapse, the caldera floor rose up, forming a resurgent dome. A graben system was formed on this structural dome consist of marble and granite, reaching a height of 1900 m. Different types of alterations occurred on the edges of grabens and where the dome resurges. Intensive alteration zones have been identified within the ignimbrites in the caldera, particularly around the resurgent dome. The Güzelyurt resurgent caldera in Central Anatolia has significant geothermal potential due to geological events. The Narlıgöl maar, located just north of the resurgent dome towards the caldera boundary is a source of known geothermal potential. There are hot water and gas outlets in the maar, and geothermal facilities are operated on the northern flank of the maar. . Multiple gas emissions have been identified both inside and outside the Güzelyurt caldera, and an important geothermal field is also located just outside of the southern caldera wall (Bozköy Village). Detailed research about volcanism, especially in different regions of Anatolia, particularly in Central and Eastern Anatolia, is of great importance for increasing and revealing Turkey's geothermal energy potential.

How to cite: Atici, G., Aydar, E., Ulusoy, İ., and Ersoy, O.: Güzelyurt Resurgent Caldera - Cappadocia, Türkiye: The Origin of Gördeles Ignimbrite and Its Geothermal Potential , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-632, https://doi.org/10.5194/egusphere-egu24-632, 2024.

EGU24-659 | ECS | PICO | GMPV11.1

New insights into the Belbaşhanı Pumice Plinian eruption: tephrostratigraphy, eruptive history and implications for volcanic hazards posed by Hasandağ (Central Anatolia) 

Rengin Özsoy, Ivan Sunye-Puchol, Dario Pedrazzi, Efe Akkas, Antonio Costa, Erkan Aydar, Lorenzo Tavazzani, Silvia Massaro, Manuela Nazzari, Daniel P. Miggins, Simge Kaya, and Silvio Mollo

Hasandağ has been one of the most active volcanoes in the Central Anatolian Volcanic Province (CAVP) during the late Pleistocene and Holocene. The past volcanic activity of Hasandağ is characterised by the eruption of multiple lavas, domes, block-and-ash flows (e.g., Aydar and Gourgaud, 1998; Kuzucuoğlu et al., 2020; Friedrichs et al., 2020). Additionally, this volcano has also experienced significant Plinian eruptions such as the Belbaşhanı Pumice, which is the focus of this work. Here, we present a complete volcanological investigation to better characterise this pumice fallout deposit and reconstruct the large explosive eruption that formed the Belbaşhanı Pumice approximately 400 ka ago.

By combining different methodological approaches (i.e., tephrostratigraphy, geological mapping, granulometric distribution, glass chemistry, geochronology, and shard morphology), we have derived isopach and isopleth maps, volume estimation, column height, and location of the eruption vent. The Belbaşhanı Pumice was formed by a Plinian column of about 23 km in height, which erupted ~2 km³ of bulk pyroclastic material. This column was erupted from a Hasandağ vent located at the intersection of the Tuz Gölü fault and a circular shape depression resembling a volcanic caldera. Major and trace element abundances show that the rhyolitic Belbaşhanı Pumice follows a compositional trend similar to those of documented for other Hasandağ pyroclastic deposits. The dispersal axis of the Belbaşhanı Pumice plume extended towards the NNE, leading to the accumulation of a pumice layer of at least 17-m-thick in proximal deposits and up to 2-m-thick in medial-distal areas (20 km from the vent). The highly vesiculated nature of the pumices and glass morphology indicate that Belbaşhanı Pumice was purely a magmatic eruption without any wet phases. Based on the abovementioned observations, we infer that the eruptive history of Hasandağ was related to VEI > 5 Plinian eruptions.

This contribution is relevant for a better understanding of hazard assessment within the CAVP, especially considering the current increase in fumarolic vents around the summit area, and in the seismic events  below and near the Hasandağ. In addition, the geochemical and geochronological data set is an important step to 1) foster future tephrochronological correlations, 2) constrain the distribution of the Belbaşhanı Pumices distal ashes and its eruptive magnitude, and 3) synchronize paleoenvironmental, paleoclimatic and archaeological records.

This research is part of Rengin Özsoy's Ph.D. thesis, funded through a PhD scholarship from La Sapienza – University of Rome and by the PÜSKÜRÜM project, a Marie Curie Action (Grant No. 101024337) funded by the European Union’s Horizon 2020.

 

References:

  • Aydar, E. and Gourgaud, A. (1998). The geology of Mount Hasan stratovolcano, central Anatolia, Turkey. J Volcanol Geotherm Res 85:129–152. https://doi.org/10.1016/S0377-0273(98)00053-5
  • Friedrichs, B., et al. (2020). Late Pleistocene eruptive recurrence in the post-collisional Mt. Hasan stratovolcanic complex (Central Anatolia) revealed by zircon double-dating. J Volcanol Geotherm Res 404:107007. https://doi.org/10.1016/j.jvolgeores.2020.107007
  • Kuzucuoğlu, C., et al. (2020). Geomorphology and tephrochronology review of the Hasandağ volcano (southern Cappadocia, Turkey). Mediterranean Geosciences Reviews, https://doi.org/10.1007/s42990-019-00017-1

 

How to cite: Özsoy, R., Sunye-Puchol, I., Pedrazzi, D., Akkas, E., Costa, A., Aydar, E., Tavazzani, L., Massaro, S., Nazzari, M., Miggins, D. P., Kaya, S., and Mollo, S.: New insights into the Belbaşhanı Pumice Plinian eruption: tephrostratigraphy, eruptive history and implications for volcanic hazards posed by Hasandağ (Central Anatolia), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-659, https://doi.org/10.5194/egusphere-egu24-659, 2024.

EGU24-718 | ECS | PICO | GMPV11.1

Geochemical characterization of Anatolian tephras from Late Middle and Early Upper Palaeolithic sites in the Jebel Qalkha area, southern Jordan 

Shuang Zhang, Simon Blockley, Naima Harman, Christina Manning, Dustin White, Rhys Timms, and Seiji Kadowaki

The Middle to Upper Palaeolithic transition in the Levant is characterized by key archaeological shifts, including the interaction between Neanderthals and AMH and the appearance and dispersal of the Upper Palaeolithic. During this period there is also potential for abrupt climatic transitions to influence the distribution of humans across the region. One issue is the precision and resolution to which we can date Levantine archaeological sites and the wider environmental record. Ongoing studies have demonstrated that archaeological sites in this region receive volcanic ash horizons (tephra), which can be utilised as a tool to provide chronological markers to date archaeological sites and to link them to important palaeoclimate records (Barzilai et al., 2022).

Here we present the detailed cryptotephra stratigraphic profiles from two Jordanian archaeological sites in the Jebel Qalkha area, one Early Upper Palaeolithic (EUP) to Epipalaeolithic site – Tor Hamar, and another Late Middle Palaeolithic (LMP) site – Tor Faraj. The data include tephra shard concentrations in different cultural layers. We also present new major and trace element geochemical data that trace the majority of these tephra layers to Anatolian volcanic centres. This allows existing radiometric ages for some of these tephra to provide additional age constraints in these archaeological sites. Our data show the potential for sites in this region to be correlated into Anatolian and Aegean volcanic records and distal environmental records from marine cores and the Dead Sea sequence (Kearney et al., 2022). This would allow further underpinning of studies that link environmental change with early human adaptations in the region.

 

Barzilai, O., Oron, M., Porat, N., White, D., Timms, R., Blockley, S., Zular, A., Avni, Y., Faershtein, G., Weiner, S. and Boaretto, E., 2022. Expansion of eastern Mediterranean Middle Paleolithic into the desert region in early marine isotopic stage 5. Scientific reports, 12(1), p.4466.

Kearney, R., Schwab, M. J., Neugebauer, I., Pickarski, N., and Brauer, A.: The TephroMed project: Precise synchronising of two key palaeoclimatic ICDP records of the eastern Mediterranean using tephra, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-468, https://doi.org/10.5194/egusphere-egu22-468, 2022.

How to cite: Zhang, S., Blockley, S., Harman, N., Manning, C., White, D., Timms, R., and Kadowaki, S.: Geochemical characterization of Anatolian tephras from Late Middle and Early Upper Palaeolithic sites in the Jebel Qalkha area, southern Jordan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-718, https://doi.org/10.5194/egusphere-egu24-718, 2024.

Preliminary Investigation of Volcanic Succession and Mineralogy of the Southern part of Mount Ağrı, Eastern Anatolia, Turkey

 

Zeynep Madak1*, Elif Varol1, G. Deniz Doğan-Külahcı1

 

1  Hacettepe University, Department of Geological Engineering, 06800, Ankara, Türkiye

 

 

Mount Ağrı is a significant stratovolcano located in Eastern Anatolia, Turkey, characterized by its steep conical shape and unique ice-capped structure. It is generally considered part of the Alpine-Himalayan orogenic belt and developed in the Quaternary, with its last known eruption occurring in 1840.

 

The volcanic succession in the southern part of Mount Ağrı begins with basaltic volcanic lava flows. These lower lava flow units exhibit a hypocrystalline porphyritic texture and contain a mineral assemblage of plagioclase + pyroxene ± olivine + oxide. These lava flows are overlain by a series of Plinian pumice-fall deposits of varying thicknesses of layers, which include ash-size volcanic material, different sizes of normally graded pumices, and inversely graded lithic clasts. Predominantly slaty fabric is observed in the pumices, with the thickness of pyroclastic fall deposits ranging up to 20 m and the color of the sequences varying between beige and white.

 

Finally, younger lava flows overlie these pyroclastic sequences. These younger lavas generally exhibit a hypocrystalline porphyritic texture, although an aphanitic texture has also been observed. The upper lava flow units display a mineral assemblage of pyroxene + plagioclase + oxide. The ongoing geochemical analyses will unveil the processes influencing the formation of these volcanic rocks and help determine the origin of the magma.

 

 

Key words: Mount Ağrı, Eastern Anatolia,  plinian fall deposits, lava flow, mineralogy

How to cite: Madak, Z., Varol, E., and Dogan Kulahci, G. D.: Preliminary Investigation of Volcanic Succession and Mineralogy of the Southern part of Mount Ağrı, Eastern Anatolia, Turkey , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-746, https://doi.org/10.5194/egusphere-egu24-746, 2024.

The Greater and Lesser Hasandağ summits have both active and extinct fumarole vents, with evident hydrothermal alteration in their vicinity. Active fumaroles were documented on the western summit flanks of the Greater Hasandağ crater, at altitudes between 3000 and 3150 meters. Several hydrothermally altered zones are located inside the double craters of Greater Hasandağ and on the Lesser Hasandağ summit. In order to characterize the both completed and ongoing hydrothermal alteration process, a total of 27 rock samples were gathered from the hydrothermally altered rocks. The mineralogical compositions were examined by X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FT-IR) from the selected parts of altered rocks. Presence of common low–grade temperature (0 – 100 °C) secondary mineralization such as alunite, natro-alunite, halloysite, and opal-AN with scarce jarosite indicate existence of a continuous alteration process in a systematic order of crystallization. Recurrent temperature measurements from the fumarole vents also confirm the mineralogical findings. FT-IR analysis is also used synchronously to identify the spectral characteristics of hydrothermally altered rocks together with other analytical methods. Spatial distributions of the alteration minerals of Hasandağ were monitored comprehensively by using ASTER and Sentinel-2 imagery, relying on the reflectance and absorbance characteristics observed in the FT-IR data obtained from the altered samples. The combined results allowed us to produce precise hydrothermal alteration maps. Significantly, the zones where the alteration is prevalent are located along the Karacaören and Hasandağ Faults, which extend in the northeast-southwest and northwest-southeast directions, respectively.

How to cite: Diker, C., Akkaş, E., Ulusoy, İ., and Şen, E.: Pairing mineralogical and multispectral satellite imagery analysis to map the hydrothermal alteration on Hasandağ Volcano (Aksaray, Türkiye), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-748, https://doi.org/10.5194/egusphere-egu24-748, 2024.

EGU24-1078 | ECS | PICO | GMPV11.1

Eruptive recurrence and magma accumulation for Quaternary stratovolcanoes in Central Anatolia 

Bjarne Friedrichs, Axel K. Schmitt, Martin Danišík, Oscar M. Lovera, and Gokhan Atıcı

Mt. Erciyes and Mt. Hasan are the two largest stratovolcanic complexes of the Central Anatolian Volcanic Province (Turkey). Despite geochronological evidence for early Holocene eruptions classifying both volcanic systems as active (Sarıkaya et al., 2019; Schmitt et al., 2014), their Late Pleistocene–Holocene chronostratigraphies remained poorly constrained. Combining zircon U–Th–Pb crystallization ages with trace element concentrations (zircon petrochronology) and (U–Th)/He cooling ages (zircon double-dating; ZDD), we identified contrasting magma recharge and eruptive recurrence patterns.

Mt. Hasan, magmatically and volcanically active since ca. 550 ka, predominantly erupted andesitic lava domes and flows as well as block-and-ash-flows. Zircon double-dating indicates a Late Pleistocene recurrence of at least one eruptive episode every ca. 5–15 ka. Combined with volume estimates, zircon geochronology suggests Middle–Late Pleistocene eruptive magma fluxes of ~0.3–0.1 km3/ka, similar to continental arc volcanoes (Friedrichs et al., 2020a).

Mt. Erciyes formed after the deposition of the Valibaba Tepe Ignimbrite with a U–Pb zircon age of 2.73 ± 0.02 Ma (all uncertainties 1σ). Its magmatic system is characterized by protracted zircon crystallization since at least ca. 800 ka. Episodes of scoria cone and lava dome as well as pyroclastic fall-out emplacement at ca. 105 and ca. 88–85 ka were followed by an extended eruptive lull. In an early Holocene resurgence, four peripheral rhyolitic–dacitic lava domes erupted, three of them with significant initial explosive phases. Yılanlı Dağ was emplaced at 9.4 ± 1.3 ka, Dikkartın at 8.9 ± 0.5 ka, and Karagüllü as well as Perikartın with their stratigraphically directly overlying pyroclastic deposits at 8.8 ± 0.8 ka (Friedrichs et al., 2021a).

Tephra glass major and trace element geochemistry identifies Karagüllü as the source of a cryptotephra found in a Black Sea gravity core, calling for a re-evaluation of its age model. The chemically indistinguishable Dikkartın and/or Perikartın eruptions are potential sources of the Eastern Mediterranean S1 tephra, an important marker horizon for archaeological and paleoclimatological research. Proximal fall-out from the Dikkartın eruption indicates eastward dispersal from a 20 ± 5 km high eruption plume, in agreement with probabilistic tephra dispersal modeling results. Distal S1 tephra, however, is distributed up to ~1300 km south of Mt. Erciyes, suggesting tephra transport by low altitude rather than stratospheric winds. This may either be due to eolian reworking of proximal deposits or due to co-ignimbrite ash cloud dispersal (Friedrichs et al., 2020b).

Contrasting thermochemical evolutions of the magma plumbing systems control the distinct eruptive styles and recurrence patterns. For Mt. Hasan, zircon crystallization temperatures and melt differentiation indices span comparably narrow, time-invariant ranges, whereas for Mt. Erciyes, these parameters fluctuate over broader ranges. Thermochemical modeling indicates moderate near-steady recharge into an upper crustal magma chamber beneath Mt. Hasan (“warm” storage, eruptible), but low and modulated magma recharge for Mt. Erciyes (“cold” storage, rheologically locked). Nonetheless, both systems may be reactivated by magmatic rejuvenation. Violent explosive eruptions would pose major threats for the local population, particularly for Kayseri metropolis at the base of Mt. Erciyes (Friedrichs et al., 2021b).

How to cite: Friedrichs, B., Schmitt, A. K., Danišík, M., Lovera, O. M., and Atıcı, G.: Eruptive recurrence and magma accumulation for Quaternary stratovolcanoes in Central Anatolia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1078, https://doi.org/10.5194/egusphere-egu24-1078, 2024.

EGU24-1114 | ECS | PICO | GMPV11.1

Spatial and Temporal Variability of Slip Rates on the Tuz Gölü Fault Zone: Insights from Zircon Double Dating of Offset Lavas of Mount Hasan, Central Anatolia  

Gülin Gencoglu Korkmaz, Axel K. Schmitt, Janet C. Harvey, Martin Danišík, and Lindsay M. Schoenbohm

Accurate knowledge of fault displacement rates is essential for seismic hazard assessments, with long-term slip rates being critical as constraints for the tectonic drivers of seismicity. The Tuz Gölü Fault Zone (TGFZ) is a NW-SE trending ~200 km long structure within the central Anatolian continental plateau. It consists of eleven parallel or sub-parallel fault segments, each ranging in length from 9 to 30 km, but seismic activity is scarce, making it difficult to pinpoint deformation mechanisms and magnitudes. Previous studies suggested that the TGFZ can produce earthquakes between M = 6.1 and 6.8, with generally higher displacement rates in the southern part of the TGFZ compared to the northern segments. Here, we studied the Akhisar-Kilic segment, which is located in the southern part of TGFZ. It dissects the southeastern flank of Mount Hasan, a prominent active stratovolcano, where several upper Pleistocene lava flows exhibit morphological evidence for faulting and hydrothermal activity. We conducted zircon double-dating, which merges U-Th and U-Pb geochronology and (U-Th)/He thermochronology, to date these variably offset lavas in order to establish fault geometries and offset rates.
Zircon crystallization ages of four lava flows, sampled in duplicate or triplicate on both sides of the TGFZ, permit correlation between proximal parts of the flows, and the more distal lobes across the TGFZ. The youngest zircon crystallization age population in each of the two northernmost flows overlaps within error, and they are closer to equilibrium than for the middle and southern flows. (U-Th)/He dates record eruptive cooling and indicate a systematic increase from north to south, with eruption ages between 39.0 ± 1.0 and 151 ± 3 ka.
Detailed morphological study of faulted lava flows utilizing a 5-meter digital elevation model (DEM) demonstrates that reasonable lava flow geometry can be restored within a range of oblique slip scenarios, ranging from primarily dip slip offset, to moderate right lateral oblique offsets. Combining the age dating and the geomorphic analysis yields vertical slip rates that can range up to between 0.5 and 0.6 mm/yr over the duration of lava emplacement in the southeastern sector of Mount Hasan. Because these rates are faster than previous estimates, we also expect that some TGFZ segments have the potential to produce earthquakes with considerably higher magnitudes than previously claimed. New slip rates covering a significant portion of the Late Pleistocene extend the fault history beyond the timescales of geodetic monitoring and historical records, thereby offering a significant vantage point for the derivation of seismic hazard estimates based on fault analysis. This is crucial to advance assessment of the multiple volcano-tectonic hazards that result from the coexistence of an active volcano and an active fault zone.
Keywords: multiple volcano-tectonic hazards, offset lavas, slip rates, zircon double dating

How to cite: Gencoglu Korkmaz, G., Schmitt, A. K., Harvey, J. C., Danišík, M., and Schoenbohm, L. M.: Spatial and Temporal Variability of Slip Rates on the Tuz Gölü Fault Zone: Insights from Zircon Double Dating of Offset Lavas of Mount Hasan, Central Anatolia , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1114, https://doi.org/10.5194/egusphere-egu24-1114, 2024.

EGU24-1687 | PICO | GMPV11.1 | Highlight

Hazards and risk assessment for Volcanoes of Turkey  

Stephen Sparks, Gokhan Atici, Sarah Brown, Bilge Karaman-Little, and Mark Woodhouse

Turkey has 14 active volcanoes known to have had eruptions of Holocene age and four historic eruptions have been recorded. The last eruption was at Ağri (Ararat) in 1840, when an estimated 1900 people died. The low rate of eruptions in Turkey might be construed as indicating low risk, but this is misleading for two reasons. Firstly, the Holocene record indicates that many of the volcanoes have had significant explosive eruptions, some including long run-outs of pyroclastic flows and blasts. Secondly, there has been huge population growth in cities on the flanks of active volcanoes, which greatly increases exposure. More than 3.1 million people live within 30 km of active volcanoes in Turkey.  Urban development on the surface of Holocene pyroclastic flows and blast deposits lead to high risk should volcanic activity resume. The vulnerability is further exacerbated through current populations having no experience of past eruptions. In the TurcVolc project, profiles of all Turkey’s active volcanoes were developed with an emphasis on hazards and risk assessment. Modelling of these hazards provides a baseline for identifying potential hazard zones for future eruptions. The above points are illustrated by presenting volcanic hazard and risk profiles for Erciyes Daği and Hasan Daği volcanoes. The Volcanic Hazard and Population Exposure Indices for each volcano were used to develop a risk matrix for Turkish volcanoes. Four volcanoes were identified at risk level III (high risk). These were Erciyes Dağı, Gölcük, Hasandağ and Nemrut. Three volcanoes exhibited dominantly effusive behaviour and small-scale explosive activity at risk level I (low risk). These were Karapınar Volcanic Field, Karacadağ and Kars Plateau. The remaining volcanoes (Ağri, Tendurek, Acıgol, Kula, Golludag, Süphan, Girekol) were classified at risk level II (intermediate risk).

How to cite: Sparks, S., Atici, G., Brown, S., Karaman-Little, B., and Woodhouse, M.: Hazards and risk assessment for Volcanoes of Turkey , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1687, https://doi.org/10.5194/egusphere-egu24-1687, 2024.

EGU24-12038 | ECS | PICO | GMPV11.1

Providing a detailed glass geochemistry for key tephra layers of Lake Van, Eastern Anatolian Volcanic Province 

Rebecca Kearney, Jeremy Goff, Markus J. Schwab, Ina Neugebauer, Victoria Smith, Oona Appelt, Christina Günter, Yavuz Özdemir, Özgür Karaoǧlu, Matthew Thirwall, Dan Burfod, Nadine Pickarski, Rik Tjallingii, and Achim Brauer

The volcanoes of Nemrut and Süphan in the Eastern Anatolian Volcanic Province (EAVP) have been active throughout the late Quaternary, dispersing ash over wide areas. Numerous eruptions spanning the last interglacial to glacial period (130-30kya) are recorded in outcrops around the volcanoes and in the cores from Lake Van. A comprehensive tephrostratigraphy framework for the EAVP is an essential requirement for synchronising palaeoclimatic and archaeological records across the Mediterranean region. More information is required from the eruption deposits, including glass geochemistry on individual shards, and the stratigraphic order and precise ages for the eruptions.

Here we present the findings of our detailed tephra investigation for the palaeoclimatic record of Lake Van (Turkey), as part of the TephroMed project. The lake is located close to both Nemrut and Süphan. Fourteen visible tephra layers (called V-layers) from Lake Van PALEOVAN ICDP record underwent geochemical characterisation by using major, minor (EPMA) and trace element analysis (LA-ICP-MS). New chemical analyses and 40Ar/39Ar ages of eruption deposits from proximal outcrops, provide detailed insight into the complex volcanic history of the EAVP, particularly of Nemrut. These results have revealed new volcanic origins for certain V-layers to Nemrut and Süphan, with tentative correlations between Lake Van’s fourteen V-layers to previously published dated proximal outcrops. Additionally, new glass geochemistry from dated proximal outcrops confirm the ages of the key eruption events associated with V-51 and V-18a of Lake Van. This improves the chronology of the Lake Van record and provides an understanding for the timing of complex eruptions from Nemrut and Süphan. The results are a major step forward to building a detailed tephrostratigraphic framework for the EAVP.

How to cite: Kearney, R., Goff, J., J. Schwab, M., Neugebauer, I., Smith, V., Appelt, O., Günter, C., Özdemir, Y., Karaoǧlu, Ö., Thirwall, M., Burfod, D., Pickarski, N., Tjallingii, R., and Brauer, A.: Providing a detailed glass geochemistry for key tephra layers of Lake Van, Eastern Anatolian Volcanic Province, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12038, https://doi.org/10.5194/egusphere-egu24-12038, 2024.

EGU24-14734 | ECS | PICO | GMPV11.1

Electrical Conductors Beneath Mt. Erciyes Imaged by Three-dimensional Modeling of Magnetotellurics Data 

Ruken Yazıcı, Sabri Bülent Tank, Serkan Üner, and Mustafa Karaş

Earlier studies propose that the volcanic activity embodying the polygenetic Mt. Erciyes in the Cappadocian Volcanic Province (CVP), Central Anatolia, Türkiye, transpired as an inevitable product of the post-collisional extension experienced along two entities, the Anatolide-Tauride Carbonate Block, and the Central Anatolian Crystalline Complex (CACC). With its sixty-four monogenetic vents, Mt. Erciyes is the highest and most voluminous (3300 km2) stratovolcano in Central Anatolia with its summit reaching as high as 3917m. Strain-partitioning played a key role in the formation of the fault systems and the Erciyes basin that favored the evolution of the volcano. During three survey campaigns conducted in 2013, 2014, and 2018, a total of thirty-eight wide-band magnetotellurics (MT) observations were systematically made unravel the electrical structure beneath the Erciyes stratovolcano complex and the adjacent Erciyes basin, as part of a research initiative funded by the NSF under the title Continental Dynamics / Central Anatolian Tectonics (CD/CAT). Defining the boundaries of the Erciyes volcanic complex, the basin exhibits prominent substantial, particularly three major faults, the Yeşilhisar, Develi and Gesi Faults, with the two of them framing the western and eastern edge and the last delineating runs in the middle of the basin. The Gesi Fault crosses from the central part of the basin and acts as the main branch of the wider Central Anatolian Fault (CAF) Zone. Based on geological evidence, the volcano developed in the Pliocene and Quaternary in two stages. These are the (i) Koç Dağ (>2.8 Ma) and the (ii) New Erciyes (<2.8 Ma) stages with various magmatism types, respectively. In this study, phase tensor analyzes were performed on the electrical conductivity structure beneath Mount Erciyes, the summit region and surrounding data collected from thirty-eight observation points, leading to the development of three-dimensional models using the ModeM inversion algorithm in two different ways, with and without topography information.

How to cite: Yazıcı, R., Tank, S. B., Üner, S., and Karaş, M.: Electrical Conductors Beneath Mt. Erciyes Imaged by Three-dimensional Modeling of Magnetotellurics Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14734, https://doi.org/10.5194/egusphere-egu24-14734, 2024.

EGU24-1504 | Posters on site | TS2.6

Triassic-Jurassic ophiolites of Dinaridic Ozren and Borja-Mahnjača massifs in Bosnia and Herzegovina: Mineralogy, geochronology, and P-T estimates from subducted sole 

Marián Putiš, Ondrej Nemec, Samir Ustalić, Jiří Sláma, Dražen Balen, Elvir Babajić, Ján Soták, and Peter Ružička

The Ozren and Borja-Mahnjača ophiolite complexes in Bosnia and Herzegovina are part of the Dinaridic Triassic-Jurassic ophiolite belt (Putiš et al., 2022; Minerals). Triassic oceanic crust was dated at 242±1 Ma from a relic zircon population in a plagiogranitic layer of partially melted eclogitic sole by LA-ICP-MS U-Pb method, while the main zircon population of 176±1 Ma dates the crystallization of this layer from a metamorphic-anatectic melt. The host sole (Cpx-Grt-Rt) eclogite yielded metamorphic, most likely exhumation zircon age of 168±5 Ma, while rutile gave an age of 165±3 Ma. Jurassic lower oceanic crust was dated from an isotropic gabbro (178±1 Ma, zircon) and plagiogranite (177±1 Ma, zircon). The mantle spinel lherzolites, harzburgites, and dunites are crosscut by Cpx-Pl and Amp-Pl gabbroic, gabbro-pegmatitic, leuco-gabbroic (174±1 Ma, zircon), and doleritic (174±5 Ma, apatite) dykes, all suggesting an advanced evolutional stage and a shallower level of ophiolites due to extension and the deeper mantle melting. The upper oceanic crust pillow basalts are alternating with Bajocian to Callovian radiolarites (~171-162 Ma; Ustalić, Soták et al., 2023; Newsletter of the Slovak Geological Society). The dated N-MORB type sole eclogites-amphibolites indicate the intra-oceanic subduction of the Triassic gabbroic oceanic crust to about 55-60 km that was estimated from Perple_X modelling of 1.9-2.1 GPa and 780°C. Partial melting of subducted slab and a mantle wedge initiated the formation of Jurassic supra-subduction ophiolitic complex detected at ~178-162 Ma. Inferred slab roll-back enhanced the sole extension exhumation between ~170-160 Ma that was coeval with the formation of the upper oceanic crust basalt-radiolarite section. The mineral chemistry-based discrimination diagrams of ultramafic rocks constrain an evolutional trend from MORB to supra-subduction types of ophiolites. An increased depletion of ultramafic rocks is indicated by an increase of Cr# in spinel from ~30 to 60, exceptionally to 75, suggesting transitional abyssal to supra-subduction peridotites and dunites. Relatively thin, often hydrated (Amp-rich) gabbro-dolerite layer of this ophiolite complex may have formed in a fore-arc/back-arc slow-spreading ridge. Ophiolitic breccia, with fragments of the Jurassic oceanic crust and rare Triassic radiolarites, indicates the closure of the Jurassic Neotethys from approximately 160 Ma.

Funding from The Slovak research and development agency projects (APVV-19-0065, APVV-20-0079, APVV-22-0092), VEGA agency (1/0028/24, 2/0012/24), and the RVO67985831 program is acknowledged.

How to cite: Putiš, M., Nemec, O., Ustalić, S., Sláma, J., Balen, D., Babajić, E., Soták, J., and Ružička, P.: Triassic-Jurassic ophiolites of Dinaridic Ozren and Borja-Mahnjača massifs in Bosnia and Herzegovina: Mineralogy, geochronology, and P-T estimates from subducted sole, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1504, https://doi.org/10.5194/egusphere-egu24-1504, 2024.

EGU24-1523 | Posters on site | TS2.6

Magnetic characterization of the Ivrea-Verbano zone (NW Italy): A key to understand the magnetism and structure of the continental lower crust 

Liliana Minelli, Gaia Siravo, Fabio Speranza, Chiara Caricchi, Eugenio Fazio, Silvia Pondrelli, and Michele Zucali

The continental lower crust remains today the less known layer of the external Earth, and only relatively recently became the focus of researches addressing its structure, composition and magnetic characteristics as deduced from seismological, geophysical, geological, geochemical and petrological data. Particularly, very intense magnetic anomalies measured over cratons imply that strong magnetic source exists at lower crustal depths beneath the continents, but its nature has remained elusive so far.

One of the approaches to obtain valuable information on the continental lower crust is studying tectonically uplifted crustal cross-sections. The likely more complete continental lower crustal section exposed on Earth is the Ivrea-Verbano (IV) zone (NW Italy), considered as a petro-geophysical reference of the continental lithosphere. The IV exposes lower crust rocks of Adria (hence of African affinity) uplifted and tilted due to the Mesozoic and subsequent Alpine tectonics. Moving NW-ward along the section, originally deeper lower crust rocks are exposed, lying adjacent to the Insubric line marking the Alpine tectonic boundary. Three main lower crust types exist in the IV zone and their best exposures are along the Val d’Ossola, Val Strona and Val Sesia. Val d’Ossola and Val Strona outcrops show continental lithologies (mafic and felsic protoliths with few marbles) in both amphibolite and granulite metamorphic facies. The Val Sesia section hosts gabbros and diorites originated from a giant input of basaltic magmas underplated at crust-mantle interface in Permian times. Moving towards the Insubric line (lower part of the lower crustal section) few subordinate slices of peridotites are exposed (Megolo, Balmuccia and Finero, this latter in the northeastern most part of the IV zone). For instance, at Balmuccia (Val Sesia), a mantle slice of peridotites is tectonically embedded within the gabbros. Here seismic and gravimetric data suggest that paleo-Moho is very shallow.

We sampled the IV rocks along three sections exposed in the Val d’Ossola, Val Strona and Val Sesia at 34 paleomagnetic sites (eight oriented samples at each site) and 7 non-oriented sites (from two to eight hand-samples) for a total number of 306 samples and measured: 1) the magnetic susceptibility (k), 2) the direction and intensity of the natural remnant magnetization (NRM), 3) hysteresis loop parameters, and 4) density. These results will represent the input data for a forward magnetic model of the IV zone at a crustal scale, to be considered as an analogue for others lower continental crust settings.

These results were gathered in the frame of the Pianeta Dinamico "UNLOCK" INGV project, which aims at improving the knowledge on the structure, composition, magnetic properties and fluid content of the continental lower crust towards the mantle transition, by integrating new seismic, magnetic, mineralogical, petro-structural and geochemical data with unprecedented resolution from two worldwide known sampling localities, the Ivrea-Verbano and Serre (Calabria) lower crust sections.

How to cite: Minelli, L., Siravo, G., Speranza, F., Caricchi, C., Fazio, E., Pondrelli, S., and Zucali, M.: Magnetic characterization of the Ivrea-Verbano zone (NW Italy): A key to understand the magnetism and structure of the continental lower crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1523, https://doi.org/10.5194/egusphere-egu24-1523, 2024.

EGU24-3390 | ECS | Orals | TS2.6

Detrital rutile U-Pb geochronology as a tracer of convergence in the External Western Carpathians 

Ludwik de Doliwa Zieliński, Jakub Bazarnik, Ellen Kooijman, Karolina Kośmińska, Tomáš Potočný, Stanisław Mazur, and Jarosław Majka

The collision of Europe (Laurusia) and Alcapa (part of Adria) lead to the formation and later erosion of high-pressure rocks in the Carpathian arc. Since metamorphic rutile requires relatively high pressure to crystallize, its formation during orogeny is indicative for a subduction setting. To better understand the closure of the Alpine Tethys Ocean in the Western Carpathians, U-Pb geochronology was applied to detrital rutile from medium grained sandstones of the Magura and Silesian Nappes. Twelve samples were collected along a transect through the Magura Nappe and three samples from the Silesian Nappe were added as a reference. Approximately 200 rutile grains were separated from each sandstone and around half of them were selected for further analysis. The dated rutile shows significant differences in age, as well as in appearance (shape, inclusions, zoning etc.) suggesting derivation from various sources.

The most prominent age peaks represent the Variscan (c. 400-280 Ma) and Alpine (c. 160-90 Ma) tectonic events, which are well-represented in all but the oldest dated sample. It is noteworthy that four distinct Alpine maxima were detected in the rutile dataset. The two most prominent peaks of 137-126 Ma and 115-105 Ma are found in the majority of the samples. In two sandstone samples, deposited in the Eocene – Oligocene and the Late Cretaceous – Paleocene, the youngest peak of 94-90 Ma appears. Another peak of 193-184 Ma is also present in these two samples, as well as in another sandstone deposited between the Paleocene and Eocene. In addition, most of the dated sandstones show some Proterozoic ages (approx. 1770 Ma, 1200 Ma, 680 Ma and 600 Ma).

Tentatively, we propose that recognizable events include the Jurassic subduction of the Meliata Ocean (~180-155 Ma), and the Cretaceous thrust stacking and exhumation of the Veporic and Gemeric domains (140-90 Ma). The abundance of Alpine rutile in all but the oldest dated sandstone suggests no physical barrier for supply of detrital material derived from the southern and central Alcapa (part of Adria) to a sedimentary basin developed north of the alleged Oravic (Czorsztyn) continental sliver within the Alpine Tethys Ocean. The lack of young Alpine ages in the oldest sandstone could be a result of either a natural boundary between the basin and the orogen or a lack of rutile-bearing rocks at the surface at that time.

In a broader sense, we propose that synorogenic deposits of the Outer Western Carpathians contain detritus from the formerly subducted, exhumed and imbricated oceanic and continental crustal domains at the southern margin of the ALCAPA microcontinent.

This research is funded by the National Science Centre, Poland, project no. 2021/43/B/ST10/02312.

How to cite: de Doliwa Zieliński, L., Bazarnik, J., Kooijman, E., Kośmińska, K., Potočný, T., Mazur, S., and Majka, J.: Detrital rutile U-Pb geochronology as a tracer of convergence in the External Western Carpathians, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3390, https://doi.org/10.5194/egusphere-egu24-3390, 2024.

The change from a deep-marine, underfilled Flysch to a terrestrial and/or shallow-marine, overfilled Molasse stage of basin evolution is probably one of the major steps in the evolution of a foreland basin. Chrono-stratigraphic and sedimentologic data from the north Alpine foreland basin (NAFB), situated on the northern margin of the Alps, document that such a shift occurred at c. 30 Ma in the western (Swiss and German) part of the basin and c. 10 My later in the eastern (Austrian) segment. We relate these basin-parallel differences in the basin’s evolution to an orogen-parallel variation in subduction tectonics, that itself appears to be conditioned by the segmentation of the European plate during the Mesozoic phase of spreading preceding the build-up of the Alps (Schlunegger and Kissling, 2022). During the Mesozoic, the transition from the continental European plate to its extended margin farther South was most likely offset by a left-lateral fault in the vicinity of Munich, separating the future depositional realms of the NAFB into a western and an eastern segment. As a consequence, during the construction of the Alps from 35 Ma onward, continent-continent collision occurred earlier in the Western Alps (c. 32-30 Ma) than in the Eastern Alps (c. 20 Ma). This collision resulted in the delamination of the subducted European oceanic lithosphere from its continental counterpart beneath the Western Alps. As a consequence, the European continental plate beneath the Western Alps experienced a rebound, thereby causing the build-up of the Alpine topography and the increase in sediment supply to the foreland basin. This is recorded in the Western NAFB by a shift from Flysch- to Molasse-type of sedimentation at 30 Ma. Farther to the East, however, the subducted oceanic lithosphere slab of the European plate was still attached to the European continental plate, with the consequence that Flysch-type of sedimentation still prevailed in the Austrian part of the basin. The situation of sedimentation in an underfilled basin persisted until c. 20 Ma when the Austrian (eastern) part of the NAFB changed from a Flysch- to a Molasse-type of basin evolution. This is the main reason why we propose that continent-continent collision most likely occurred 10 My later in the Eastern Alps than in the Western Alps.

Schlunegger, F., Kissling, E. (2022). Slab load controls beneath the Alps on the source-to-sink sedimentary pathways in the Molasse Basin. Geosciences, 12, 226.

How to cite: Schlunegger, F. and Kissling, E.: Sedimentary records imply that continent-continent collision occurred later in the Eastern than in the Western Alps., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3428, https://doi.org/10.5194/egusphere-egu24-3428, 2024.

EGU24-4070 | ECS | Posters on site | TS2.6

High-resolution 3D geomodel of the central Po-Plain, Northern Italy. 

Daniel Barrera, Giovanni Toscani, Chiara Amadori, Roberto Fantoni, and Andrea Di Giulio

The Po Plain in Northern Italy constitutes an elongated alluvial valley characterized by an intricate geological evolution, extending from the late Paleozoic era to recent times. Notably densely populated, this region accommodates approximately one-third of the Italian population and hosts critical industrial facilities, coupled with a substantial history of oil and gas exploration and production. Given these factors, the creation of a high-resolution subsurface geomodel is imperative for various applications in this region.

Tectonically, the Po Plain is located in the Adria Microplate and is bounded by two opposite verging orogens sharing the same foreland: the Northern Apennines (NA) to the south, and the Southern Alps (SA) and the Western Alps to the north and the west. The SA are a south-verging fold-and-thrust belt, while the NA are a north-northeast-verging fold-and-thrust belt; both belts have their outer thrust front buried beneath the Neogene-Quaternary sediments of the Po Plain. The front of the Northern Apennines is structured into three different arcs with increasing amounts of shortening, from northwest to southeast: the Monferrato Arc, the Emilia Arc, and the Ferrara Arc. Along the Emilia Arc, the juxtaposition of the buried Southern Alps and the buried Northern Apennines is notably close, allowing for a more detailed analysis of their frontal convergence (a few kilometers). Moreover, the influence on the thrust(s) geometry from the inherited and inverted structural highs from the passive Mesozoic platform can be observed more clearly. This combination of factors, among others, makes the central area of the Po-Plain one of the most prolific for oil and gas production, hosting several productive fields.
Despite the long story of hydrocarbon exploration and production, a large-scale comprehensive 3D model using seismic lines and well information has not yet been published, apart from a couple of very good seismic sections, that have been studied and analyzed multiple times. In particular, the Plio-Pleistocene architecture of the basin has been only partially described. In this study, we have used an extensive database provided by ENI Spa to create a high-definition static model and several balanced cross-sections to understand better the distribution of the deformation along the Emilia arc and to comprehend how the complex relationship between NA, SA, and the inherited structural highs have driven the actual architecture of the central Po-Plain subsurface. This new highly detailed 3D geomodel provides the necessary base to implement renewable energy developments (geothermic) in one of the most populated areas in Italy.

How to cite: Barrera, D., Toscani, G., Amadori, C., Fantoni, R., and Di Giulio, A.: High-resolution 3D geomodel of the central Po-Plain, Northern Italy., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4070, https://doi.org/10.5194/egusphere-egu24-4070, 2024.

EGU24-4296 | Orals | TS2.6

Early Collisional Evolution of the Western Alps: how Important are Rift Inheritance and Paleogeography 

Gianreto Manatschal, Pauline Chenin, Gianluca Frasca, and Jean François Ghienne

The Western Alps, along the French-Italian border, are among the best investigated and imaged collisional belts worldwide. A major complexity of the Western Alps is their non-cylindricity and arcuate shape, as well as the occurrence of ultrahigh-pressure (UHP) metamorphic rocks. Our study shows that all these complexities are intimately linked to the interplay between the inherited rift architecture, the changing kinematics of convergence during the early stages of continental collision, and the complex 3D dynamics of the Alpine subduction system. Here we use a multi-disciplinary approach to investigate the evolution of the European/Briançonnais distal margin at the transition from subduction to early collision, which corresponds to the moment when rift inheritance and the paleogeographic configuration are the most important in controlling the orogenic structure and evolution.

In a first part, we reassess the architecture of the Western Alps based on a review of field and recent geophysical studies. This allows us to define the crustal architecture as well as the along and across strike position of the different Alpine units. The use of diagnostic petrologic, stratigraphic, and structural criteria allows us to identify the rift domains of the former European/Briançonnais margin, from which the different present-day orogenic units originated. This enables us to propose a first order, synthetic rifted margin template for the Western Alps. Of particular importance is the location of the necking zone, corresponding to the limit between the thick-crusted proximal and the thin-crusted distal margin. It also separates domains with different rheology and density/buoyancy/floatability, both of which control the subduction, exhumation and accretion behavior during subduction and early collision. We find that all units containing ultrahigh-pressure rocks derive only from the thin-crusted distal hyperextended domain.

In a second part, we revisit the paleogeography of the Alpine Tethys using a global kinematic restoration software (Gplates) and the new building block/rift domain concept that allows us to propose a tight fit restoration and evolution of the Atlantic Tethys junction during the Mesozoic.  In this restoration, the Briançonnais corresponds to a ribbon of slightly thinned continental crust that limits, along necking zones, two overstepping en-échelon rift basins, namely the Valais domain to the northwest and the Piemonte domain to the southeast. We affirm that this uneven-margin architecture can explain most of the Western Alps’ complexity. In our kinematic model, convergence between Adria and Europe was mainly accommodated by strike-slip movements until the late Eocene, which corresponds to the time of formation and exhumation of UHP metamorphic rocks. Early collision was diachronous along the margin and resulted first in the reactivation of the necking zone separating the Briançonnais and Prepiemonte domains. This fundamental structure, which we name the Prepiemonte Basal Thrust, floors the units preserving ultrahigh-pressure rocks. Once the distal margin was accreted, shortening mainly stepped inboard into the European necking domain, resulting in theformation of the Penninic Basal Thrust.

How to cite: Manatschal, G., Chenin, P., Frasca, G., and Ghienne, J. F.: Early Collisional Evolution of the Western Alps: how Important are Rift Inheritance and Paleogeography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4296, https://doi.org/10.5194/egusphere-egu24-4296, 2024.

EGU24-4686 | Posters on site | TS2.6

A new 4D model of Alpine orogenesis based on AlpArray 

Mark R. Handy and the members of the 4D-MB and AlpArray Groups

            Teleseismic Vp tomography from AlpArray suggests that the slab segment beneath the Central Alps comprises European lithosphere, is attached to its orogenic lithosphere and extends down to ~250 km depth, in parts possibly even to the Mantle Transition Zone. This marks a first phase of partial slab detachment, probably in late Paleogene time based on comparing slab length with shortening in the Central Alps and of Adria-Europe convergence since 35 Ma. In contrast, the slab segment beneath the Eastern Alps is detached between 80-150 km depth. The age of this second phase of slab detachment is bracketed at 23-19 Ma by criteria below and by comparing vertical detachment distance with global slab sink rates.

We propose a new model of Alpine mountain-building that features the northward motion of subduction singularities above delaminating and detaching Alpine slab segments, respectively in the Central and Eastern Alps, to explain E-W differences in Oligo-Miocene structure, magmatism, and foreland sedimentation. Mountain-building began at ~35 Ma with a decrease in Adria-Europe convergence to <1cm/yr collision, causing the European slab to steepen and detach beneath both the Central and Eastern Alps. Periadriatic magmatism may have initiated prior to slab detachment due to fluxing of the cold mantle wedge by fluids from devolatilizing crust along the steepened Alpine slab. Thereafter, the Central and Eastern Alps evolved separately. Northward motion of the singularity during slab delamination in the Central Alps increased both horizontal shortening and the taper angle of the orogenic wedge, with rapid exhumation and denudation in the retro-wedge. Slab steepening and delamination are inferred to have been more pronounced in the Eastern Alps, possibly due to the greater negative buoyancy of the slab in the absence of Brianconnais continental lithosphere in the eastern part of Alpine Tethys. Slab delamination in the east drove subsidence and continued marine sedimentation in the Eastern Molasse basin from 29-19 Ma, while the western part of the basin in the Central Alps filled with terrigeneous sediments. Slab detachment beneath the Eastern Alps at ~20 Ma coincided broadly with several dramatic events in the interval 23-17 Ma: (1) a switch from advance of the northern thrust front to indentation of the E. Alps by the eastern Southern Alps along the Giudicarie Fault; (2) rapid exhumation of Penninic nappes in the core of the orogen (Tauern Window) and orogen-parallel escape of orogenic crust toward the Pannonian Basin; (3) rapid filling of the Eastern Molasse basin. These events are attributed to a northward and upward shift of the singularity to within the orogenic crust during Adriatic indentation. Eastward propagation of the uplifting depocenter in the Eastern Molasse basin is interpreted to reflect orogen-parallel slab tearing beneath the Eastern Alps. This tearing ultimately accompanied Miocene rollback subduction in the Carpathians, as inferred from the migrating depocenter around the orogenic foredeep. An possible later slab detachment event (< 20 Ma) is inferred for the Eastern Alps from 3D-tectonic balancing of the Eastern and Southern Alps (McPhee et al., this session).

How to cite: Handy, M. R. and the members of the 4D-MB and AlpArray Groups: A new 4D model of Alpine orogenesis based on AlpArray, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4686, https://doi.org/10.5194/egusphere-egu24-4686, 2024.

EGU24-5390 | ECS | Posters on site | TS2.6

Pre-Alpine Metamorphism in Alpine low-grade metamorphic units in the Eastern Alps 

Kevin Karner-Ruehl, Walter Kurz, Hauzenberger Christoph A., Harald Fritz, Gallhofer Daniela, and Etienne Skrzypek

Pre-Alpine basement units, derived from the northeastern Gondwana margin, are incorporated within the Eastern Alps and were overprinted during Alpine nappe stacking. However, some of these units were only slightly affected by Alpine metamorphism and could therefore provide significant information about the pre-Alpine history of these basement units. The Kaintaleck Metamorphic Complex as part of the Eastern Greywacke Zone and the Silvretta-Seckau Nappe System experienced greenschist facies metamorphic conditions during Eo-Alpine times and are nowadays affiliated to the Upper Austroalpine Subunit.

The Kaintaleck Metamorphic Complex comprises a mafic suite of amphibolite, garnet-amphibolite, greenschist and serpentinite, and a felsic suite, mainly composed of gneiss and mica-schist, some of them garnet-bearing. Geochemical results of metabasites indicate a tholeiitic basalt source with MORB affinity. U-Pb zircon dating of a garnet-bearing amphibolite yields an Early Devonian age of 414 ± 5.6 Ma, interpreted as age of protolith formation. Chemical U-Th-Pb dating of monazites from the felsic suite revealed Late Devonian to Early Carboniferous ages of 362 ± 6 Ma, 358 ± 15 Ma, 351 ± 4 Ma and 349 ± 3 Ma, reflecting peak metamorphic conditions during Variscan orogeny. A two-stage metamorphic history of a HT/LP and a subsequent LT/HP metamorphic event, indicated by Zr-in-rutile thermometry and thermodynamic modeling, relates the Kaintaleck Metamorphic Complex to the opening and closure of the short-lived Balkan-Carpathian Ocean and implies a correlation to other ophiolitic relicts of Devonian age, exposed in the North-Gemeric Klatov and Rakovec Complexes in the Western Carpathians. The Seckau Complex, a part of the Silvretta-Seckau Nappe System is characterized by various metagranitoids, which have been extensively analyzed in recent studies. Based on these studies, the metagranitoids of the Seckau Nappe are subdivided into the Late Cambrian to Early Ordovican Hochreichart Plutonic Suite and the Late Devonian to Early Carboniferous Hintertal Plutonic Suite. The host rock for these large intrusions is the so-called Glaneck Metamorphic Suite, which is mainly composed of fine-grained paragneiss and mica-schist, some of them garnet-bearing. U-Pb zircon ages of the paragneisses indicate a detrital origin and ages of the cores cluster in the Neoarchean, Paleoproterozoic and Ediacaran, between 2.7 Ga and 559 Ma. A migmatized paragneiss yields an age of 505 Ma, which indicates, that migmatization was probably triggered by the intrusion of the Hochreichart Plutonic Suite. The timing of pre-Alpine metamorphism can therefore be constrained to have happened between 559 Ma and 505 Ma. Some samples do show a distinct two-phase garnet growth, suggesting an additional metamorphic event possibly during Variscan times. The Schladming Crystalline Complex, also part of the Silvretta-Seckau Nappe System, again comprises paragneisses, that were intruded by various metagranitoids. In contrast to the Seckau Complex, these metagranitoids do not only show Cambrian and Late Devonian to Early Carboniferous ages, but also Permian ages.

In order to complement the knowledge of the pre-Alpine metamorphic history of the Eastern Alps, new geochronological, geochemical and geothermobarometric data from various metapelitic and metabasic rocks within the Silvretta-Seckau Nappe system are being examined to reconstruct the tectonic development of these units in pre-Alpine times.

How to cite: Karner-Ruehl, K., Kurz, W., Christoph A., H., Fritz, H., Daniela, G., and Skrzypek, E.: Pre-Alpine Metamorphism in Alpine low-grade metamorphic units in the Eastern Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5390, https://doi.org/10.5194/egusphere-egu24-5390, 2024.

EGU24-5735 | ECS | Posters on site | TS2.6

Deep Structure of the Western Alps Derived from New Data — P and S wave velocity images from Finite Frequency Tomography 

Yuantong Mao, Xiaobing Xu, Xiaotian Tang, Liang Zhao, Lei Yang, Stefano Solarino, Anne Paul, Silvia Pondrelli, Coralie Aubert, Simone Salimbeni, Elena Eva, and Stephane Guillot

The Western Alps are a crucial region for studying subduction-collision processes. The deep structure beneath the orogenic belts has been a topic of ongoing debate and has undergone continuous refined investigations. In this study, we utilized the most extensive dataset available, covering the period from 2012 to 2020, with 1093 stations. This dataset comprises 659 permanent stations, 110 CIFALPS and CIFALPS-2 temporary stations, along with 324 AlpArray temporary stations.

We employed the finite-frequency method to conduct inversion of the regional deep velocity structure. Meticulous waveform analyses were performed across various frequency bands for both P and S waves (P: 0.1-0.5Hz, 0.5-2Hz; S: 0.05-0.1Hz, 0.1-0.5Hz). Additionally, for regions with insufficient ray coverage, we utilized the LSBP_Alpscrust1.0 model [Lu et al., 2020], derived from ambient noise tomography, to correct crustal velocities.

We have presented for the first time the deep velocity results of S-waves, demonstrating a good consistency with the P-wave velocity structure. Additionally, we re-selected the dataset pairs for the inversion of Vp/Vs images. Our findings provide further insight into the underground structure beneath the Western Alps, uncovering the presence of a continuous subducted slab. Furthermore, in the southern part of the Western Alps, there is a potential indication of high Vp/Vs ratios within the depth range of 100-150 km.

How to cite: Mao, Y., Xu, X., Tang, X., Zhao, L., Yang, L., Solarino, S., Paul, A., Pondrelli, S., Aubert, C., Salimbeni, S., Eva, E., and Guillot, S.: Deep Structure of the Western Alps Derived from New Data — P and S wave velocity images from Finite Frequency Tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5735, https://doi.org/10.5194/egusphere-egu24-5735, 2024.

EGU24-5930 | Orals | TS2.6

Tectonic architecture of the northern Dora-Maira Massif (Western Alps, Italy): field and geochronological data 

Michel Ballèvre, Paola Manzotti, Francesco Nosenzo, Mikaela Krona, and Marc Poujol

High-pressure and ultra-high-pressure metamorphic terrains display an internal architecture consisting of a pile (or stack) of several coherent tectonic thrust sheets or units. Their identification is fundamental for understanding the scale and mechanisms active during subduction and exhumation of these crustal slices. This study investigates the geometry of the northern Dora-Maira Massif and the kinematics of the major tectonic boundaries, combining field and geochronological data. The tectonic stack of the northern Dora-Maira Massif comprises the following units. The lowermost unit (the Pinerolo Unit) is mainly characterized by Upper Carboniferous fluvio-lacustrine (meta-)sediments. The Pinerolo unit is overthrust by a pre-Carboniferous basement. The latter is subdivided in two tectonic units (the Chasteiran and Muret Units) with different Alpine metamorphism (ultra-high-pressure and high-pressure, respectively). The pre-Carboniferous basement of the Muret Unit is thicker than previously thought for two main reasons. Firstly, some paragneisses, traditionally assumed to be Carboniferous and/or Permian in age, display a dominant detrital zircon source at about 600 Ma. Secondly, three samples of the Granero Orthogneiss, previously assumed to be a Permian intrusive body, have provided zircon U-Pb ages of 447 ± 3 Ma, 456 ± 2 Ma and 440 ± 2 Ma, indicating a late Ordovician or early Silurian age for the protoliths. The uppermost unit (the Serre Unit) comprises porphyritic (meta-) volcanic and volcaniclastic rocks dated to the Permian (271 ± 2 Ma), on top of which remnants of the Mesozoic cover is preserved. Detailed mapping of an area about 140 km2 shows that (i) the ultra-high pressure Chasteiran Unit is localized at the boundary between the Pinerolo and Muret Units, (ii) the Granero Orthogneiss may be considered as the mylonitic sole of the Muret Unit, characterized by a top-to-W sense of shear, and (iii) the contact between the Muret and Serre Units displays ductile-to brittle structures (La Fracho Shear Zone), indicating a top-to-the-NW displacement of the hangingwall with respect to the footwall. A final episode of brittle faulting, cutting across the nappe stack (the Trossieri Fault), indicates an extensional stage in the core of the Alpine belt, as previously documented in more external zones. This work provides a necessary and robust basis for an accurate discussion of processes acting during continental subduction of the Dora-Maira Massif.

How to cite: Ballèvre, M., Manzotti, P., Nosenzo, F., Krona, M., and Poujol, M.: Tectonic architecture of the northern Dora-Maira Massif (Western Alps, Italy): field and geochronological data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5930, https://doi.org/10.5194/egusphere-egu24-5930, 2024.

EGU24-7625 | Posters on site | TS2.6

Deformation processes and origin of fluids during Oligocene-Miocene post-orogenic extension in Alpine Corsica 

Simone Masoch, Michele Fondriest, Nereo Preto, Francesca Prando, and Giulio Di Toro

Alpine Corsica is an accretionary wedge formed during the Alpine orogenesis and exhumed through Oligocene-Miocene lithospheric extension controlled by the eastward migration of Apenninic subduction. Here we integrate field geological surveys with microstructural and carbonate stable isotope (δ18O–δ13C) analyses of fault zone rocks to constrain the evolution of the W-dipping extensional Patrimonio Fault System (PFS). The PFS consists of multiple gouge-bearing fault core strands and splay faults in the footwall damage zone, and exhumed the Schistes Lustrés (e.g., impure quartzites, marbles, calcschists, serpentines) and slices of Hercynian granitoids in the footwall block, accommodating ~6 km of cumulative displacement.

We describe a deformation sequence during exhumation consisting of D1 mylonitic shearing, D2 seismogenic faulting and D3 shallow veining events. D1 mylonitic shearing produced a decameter mylonitic zone forming the roots of PFS, coeval with localized brittle-ductile shear zones and quartz ± chlorite vein arrays observed in the footwall metamorphic units. Ductile shearing was accommodated by low-temperature quartz and calcite crystal-plasticity, and pressure-solution mechanisms at greenschist conditions (i.e., 300-400 °C). D2 seismogenic faulting either overprinted or cut the D1 structures. Ancient seismic faulting is attested by occurrence of (i) altered pseudotachylytes and (ii) cockade-bearing fault-veins injecting into the host-rocks and mutually overprinting dolomite-rich veinlet mesh and mirror-like slip surfaces observed in the footwall splay faults. Seismic faulting is also accommodated by dolomite-quartz(-chalcedony) crack-seal veins, which have isotopic compositions similar to those of the carbonate-rich units of the Schistes Lustrés. These structural and geochemical observations indicate that ancient seismicity was cyclically modulated by overpressured fluids which isotopic composition was buffered by the host-rocks. The later D3 shallow (≤ 1 km depth) veining event consists of calcite-bearing veins and concretions filling open fractures, which have distinct isotopic compositions compared to the Schistes Lustrés units, suggesting percolation of meteoric fluids at depths. Based on these observations, we speculate that the D2 faults may represent a fossil analogue of the extensional faults active in the Apennines where seismicity is driven by CO2-rich deep-sourced fluids.

How to cite: Masoch, S., Fondriest, M., Preto, N., Prando, F., and Di Toro, G.: Deformation processes and origin of fluids during Oligocene-Miocene post-orogenic extension in Alpine Corsica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7625, https://doi.org/10.5194/egusphere-egu24-7625, 2024.

EGU24-8184 | ECS | Orals | TS2.6

Control of inherited structures on deformation and uplift in the European eastern Southern Alps: a multi-scale analogue modelling study 

Anna-Katharina Sieberer, Ernst Willingshofer, Thomas Klotz, Hugo Ortner, and Hannah Pomella

Neogene to ongoing N(W)-directed continental indentation of the Adriatic microplate into Europe controls the evolution of the European eastern Southern Alps (ESA). The Adriatic microplate, traditionally considered as a rigid indenter, demonstrates significant internal deformation, with mostly Miocene shortening being accommodated within a WSW-ENE striking, S-vergent fold-and-thrust belt. The latter overprints a compositionally heterogeneous upper crust linked to Permian intrusives and extrusives and a pre-existing platform-basin geometry related to Jurassic extension.

We present new, multi-scale physical analogue experiments, to address the effect of lateral crustal heterogeneities on strain localization and deformation geometries of the ESA, which is key for establishing causal relations between crustal and lithospheric deformation and surface uplift patterns associated with Miocene basin inversion.

Brittle crustal-scale analogue experiments with inversion of pre-scribed platform-basin geometries, indicate that variations in thickness, shape, and basement structure have impact on timing and uplift of the ESA’s upper crust. Our modelling results demonstrate that experiments with a stronger upper crustal domain (representing Permian volcanic rock on Jurassic platforms) show a smaller number of thrust sheets, being in line with thrust sheet geometries across the natural example of the ESA, and continuous uplift patterns. The latter is supported by continuous exhumation within the last 15 Ma documented by low-temperature thermochronology data between Mauls and Bassano east of the Giudicarie belt (see contribution of Klotz et al., this session). The topographic evolution of the experiments is sensitive to a variation in crustal composition; additional, e.g., basement structures (modelled using a fixed and rigid basal plate whose boundaries represent Permian faults) result in limited uplift of northern model parts, which is consistent with documented little vertical movement of the western ESA north of the Valsugana fault system between Jurassic and Neogene times.

On the scale of the lithosphere, new analogue experiments with pre-scribed platform and basin geometries in the upper crust show similar lateral variations in thrust fault orientation across transfer zones as crustal-scale experiments (Sieberer et al., 2023). Variations in lithospheric strength lead to increasing wavelengths between thrust sheets in models with stronger rheologies, pre-existing heterogeneities in the upper crust to strain localisation at boundaries of strong domains. Additionally, lateral variability of ductile lower crustal thickness predicts stronger uplift in areas of thicker lower crust. A similar relationship has been documented for the northwestern ESA, where Miocene thickening of the lower crust is expected to correlate with higher uplift in the Tauern window (Jozi Najafabadi et al., 2022).

Jozi Najafabadi, A., Haberland, C., Le Breton, E., Handy, M. R., Verwater, V. F., Heit, B., and Weber, M.: Constraints on Crustal Structure in the Vicinity of the Adriatic Indenter (European Alps) From Vp and Vp/Vs Local Earthquake Tomography, Journal of Geophysical Research: Solid Earth, 127, 10.1029/2021jb023160, 2022.

Sieberer, A.-K., Willingshofer, E., Klotz, T., Ortner, H., and Pomella, H.: Inversion of extensional basins parallel and oblique to their boundaries: inferences from analogue models and field observations from the Dolomites Indenter, European eastern Southern Alps, Solid Earth, 14, 647-681, 10.5194/se-14-647-2023, 2023.

How to cite: Sieberer, A.-K., Willingshofer, E., Klotz, T., Ortner, H., and Pomella, H.: Control of inherited structures on deformation and uplift in the European eastern Southern Alps: a multi-scale analogue modelling study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8184, https://doi.org/10.5194/egusphere-egu24-8184, 2024.

EGU24-8582 | ECS | Posters on site | TS2.6

Unraveling the collisional history of the Western Carpathians through deep geophysical sounding 

Tanishka Soni, Christian Schiffer, and Stanisław Mazur

The Pieniny Klippen Belt (PKB) in the Western Carpathian branch of the Alpine-Carpathian-Dinaridic orogenic system is considered to be the surficial representation of the Alpine-Tethys suture. It is a few kilometres wide and about 600 km long unit between the Outer Western Carpathians and Central Western Carpathians and does not show typical characteristics of a suture (Plašienka et al., 1997; Schmid et al., 2008). In fact, the structural relationship between the PKB and surrounding units is ambiguous. The PKB is a sub-vertical unit with mainly shallow marine limestone and flysch deposits in a conspicuous “block-in-matrix” structure (Plašienka et al., 1997). This structure has been explained mainly by two theories: sedimentary structures formed by gravity sliding; and post-sedimentation tectonic shearing due to strike-slip movement affecting the heterolithic composition of the unit (Plašienka et al., 2012; Golonka et al., 2015). The presence of “exotic” sediments in the PKB and the southernmost units of the OWC along with their shallow marine deposition environment led to the theory proposing the presence of a continental sliver called the Czorsztyn Ridge in the Alpine Tethys, dividing it into two oceanic/marine basins: the Magura Ocean to the north and the Vahic Ocean to the south (Plašienka, 2018).

A passive seismic experiment was designed and installed to provide insight into the deep lithospheric structure across the PKB, testing the presence of a tectonic suture along with relaminated remnants of the Czorsztyn Ridge, and potential remnants of subducted or underthrusted lithosphere. Eighteen broadband stations have been deployed in a ~N-S transect under the umbrella of the AdriaArray initiative, cutting across the PKB and the Neotethian Meliata suture to the south. The data obtained during up to three years will complement 10 other permanent and temporary broadband stations, forming an approximate 250 km long profile and will be primarily used to perform receiver function analysis and to build structural and velocity models of the lithosphere (i.e., Schiffer, 2014; Schiffer et al., 2023) beneath the Western Carpathians.

Gravity and magnetic data will be used to construct a 3-D model of the subsurface complementing the seismic experiment. Preliminary assessment of the data has shown that the PKB is represented by an anomaly reaching at least until the 15 kms depth and, therefore, is a deep-seated feature. It leads to a tentative conclusion that the PKB’s “block-in-matrix” structure is rather of tectonic origin. The qualitative analysis of potential field data reveals the presence of three major elements in the deep basement of the northern Carpathians corresponding to the ALCAPA, European Platform, and a previously undefined wedge-shaped block under the Eastern Carpathians. The PKB follows the boundary between the ALCAPA and the remaining two domains.

How to cite: Soni, T., Schiffer, C., and Mazur, S.: Unraveling the collisional history of the Western Carpathians through deep geophysical sounding, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8582, https://doi.org/10.5194/egusphere-egu24-8582, 2024.

EGU24-8854 | ECS | Orals | TS2.6

Mesozoic tectonic inheritance of the European crystalline basement (SE France) revealed by thermochronology 

Louise Boschetti, Frederic Mouthereau, Stephane Schwartz, Yann Rolland, Matthias Bernet, and Melanie Balvay

The Alpine orogenic belt in SE France is the result of the collision between the European, Adriatic and Iberian plates. The accreted Variscan continental crust, which now forms the external crystalline massifs (ECMs), recorded a complex Mesozoic thermal and tectonic evolution, that is not fully understood. In the Maures-Tanneron massif (MTM), the basement has undergone periods of subsidence and uplift, the latter indicated by stratigraphic gaps from the Albian and Upper Turonian to the Maastrichian. In the Ecrins-Pelvoux massif (EPM), differential subsidence is documented during Lower Jurassic by lateral variation from marine to continental environment, but most of the Cretaceous and Paleogene periods correspond to a stratigraphic hiatus that ends with the deposition of upper Eocene sediments. The link between these stratigraphic gaps and inheritance associated with the rifting, opening of the Alpine Tethys, and early convergence between Europe, Iberia and Adria is still not resolved. The goal of this study is to elucidate the thermal evolution of the European basement in SE France (EPM and MTM) during the Mesozoic using apatite and zircon fission track low-temperature thermochronology (AFT and ZFT). ZFT data from the southern EPM indicates a complex thermal history with central ages ranging from 158 to 45 Ma, thus revealing significant Jurassic to Eocene resetting and cooling. These ages are interpreted as resulting from several tectonic stages related to (1) Jurassic rifting (2) Mesozoic shortening and erosion and/or (3) incomplete Alpine reset during the main phase of underthrusting below the Penninic Frontal Thrust during the Oligocene. In contrast, the MTM shows several thermal events, comprising a major cooling stage at ca. 200 Ma coincident with the CAMP event preserved in the northern part of the massif. A final cooling event between 30 and 25 Ma, that is mostly represented to the South of the massif, is related to the opening of the Ligurian sea. Intermediate AFT ages between these two events are also identified, likely reflecting cooling events during the Mesozoic that can be resolved using thermal modelling. Finally, the long-term thermal evolution reported from SE France ECMs allows refining the geodynamics of this region from Pangea fragmentation to the onset of Alpine orogeny.

How to cite: Boschetti, L., Mouthereau, F., Schwartz, S., Rolland, Y., Bernet, M., and Balvay, M.: Mesozoic tectonic inheritance of the European crystalline basement (SE France) revealed by thermochronology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8854, https://doi.org/10.5194/egusphere-egu24-8854, 2024.

EGU24-9322 | Posters on site | TS2.6

3D thermo-mechanical modelling of oblique continental collision: relative role of slab tearing in along-strike topography evolution 

Giridas Maiti, Alexander Koptev, Paul Baville, Taras Gerya, Silvia Crosetto, and Nevena Andrić-Tomašević

It is assumed that slab tearing (or the lateral propagation of slab break-offs) in collisional belts controls the progressive along-strike uplift of mountains and the development of adjacent basins. However, differential continental collision due to obliquity or other irregularities of the original passive margin can introduce additional complications and influence the progressive topographic growth. Here, we use a 3D thermo-mechanical numerical modelling approach to distinguish the topographic response to slab break-off propagation from the surface uplift caused by along-strike differential collision. To this end, we examine the effects of several key factors, including (1) the obliquity of the passive margin, (2) the age of the oceanic slab, (3) the rate of convergence between colliding plates, and (4) the presence of a microcontinental block between passive and active margins. In all experiments, slab break-off initiates earlier than continental collision due to the transition from oceanic to continental subduction beneath the fore- and back-arc domain formed during the previous retreat of the subduction zone. The topographic uplift associated with slab tearing is more pronounced and spreads laterally much faster than in the subsequent collision phase. The parametric analysis shows that the lateral migration of the continental collision is controlled by the convergence rate, while the horizontal velocity of slab tearing depends mainly on the obliquity angle and slab age. The presence of additional structural complexity - a microcontinental block that has detached from the passive margin - leads to a transition from horizontal to vertical slab tearing and to more intense syn-collisional mountain growth.

How to cite: Maiti, G., Koptev, A., Baville, P., Gerya, T., Crosetto, S., and Andrić-Tomašević, N.: 3D thermo-mechanical modelling of oblique continental collision: relative role of slab tearing in along-strike topography evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9322, https://doi.org/10.5194/egusphere-egu24-9322, 2024.

EGU24-9371 | Posters on site | TS2.6

Kinematic restoration of the western Tauern Window 

Julia Rudmann, David Colin Tanner, Michael Stipp, Hannah Pomella, and Christian Brandes

The Tauern Window (TW) in the European Alps is one of the largest tectonic windows in the world. Its formation started in the Cretaceous with subduction of the Penninic realm beneath the northern margin of Adria leading to the collision between Europe (Subpenninic) and the Adria margin (Austroalpine). The resulting Penninic and Subpenninic nappe stack was exhumed by ca. 20 km by the approach of the Dolomites Indenter (Eastern Southern Alps) in the Miocene. This last deformation stage resulted in synkinematic N-S shortening of the western TW (ca. 70 km), W-E extension and lateral extrusion towards the east. However, how the Subpenninic core (Venediger Duplex; VD) and the Penninic and Austroalpine nappes (PN and AN, respectively) in the hanging-wall were tectonically stacked, upright folded and emplaced is poorly understood. This study investigates the deformation accommodated by each major tectonic basement unit of the western TW, and contributes to a better understanding of orogenic processes in general.

We kinematically restore the cross-section of [1] along the Brenner Base Tunnel (W of the TRANSALP seismic profile) using the software MOVEtm (Petroleum Experts), focusing firstly on the VD. We choose area balancing as minimum criteria, because we do not know how much material was transported out of the plane of cross-section by extension and lateral extrusion. We integrate zircon fission-track data (ZFT) as a temporal constraint and test different geothermal gradients. Petrological data are used to define the maximum depth the VD reached at the time of indentation and as marker for the transition from brittle to viscous conditions of the felsic rocks of the VD (lowest temperature for folding). Finally, we reconstruct the hanging-wall nappes above the restored VD, thereby precisely constraining the position of the AN at that time. The surface samples taken from the AN must have reached thermal conditions between the annealing zones of apatite fission-tracks and ZFT (115°C and 180°C, respectively) as only the former system was reset in the Miocene.

We first displace the entire VD down along the Sub-Tauern Ramp below the 300°C isotherm (brittle to viscous transition of felsic rocks). For this, the geothermal gradient of 50°C/km fits well to the petrological data. ZFT ages reveal upright folding of the VD terminated at ca. 17 +/- 2 Ma. Subsequent unfolding of the gneiss cores, while conserving surface area, reveals the model to be extended ca. 70 km to the south (i.e. thus equaling indenter shortening), which means that no material left the plane of cross-section by W-E extension or lateral extrusion. However, the situation for the hanging-wall nappes is different: The total thickness of the northern limbs of the AN and the PN together is twice as much after restoration compared to today. We postulate that the extension on the Brenner Normal Fault mainly caused this tectonic thinning, which is approximately 10 km.   

References

[1] Reiter, F., Freudenthaler, C., Hausmann, H., Ortner, H., Lenhardt, W., & Brandner, R. (2018). Tectonics, 37(12), 4625-4654.

How to cite: Rudmann, J., Tanner, D. C., Stipp, M., Pomella, H., and Brandes, C.: Kinematic restoration of the western Tauern Window, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9371, https://doi.org/10.5194/egusphere-egu24-9371, 2024.

EGU24-9709 | ECS | Orals | TS2.6

Dinarides slab gap - fact or fiction 

Lucija Golub, Stéphane Rondenay, and Josip Stipčević

Ever since the first regional teleseismic tomography images of the central Mediterranean region, one aspect that has stood out in nearly every model is the missing deep slab under the north and central Dinarides. In contrast, concurrent investigations of crustal formation have pointed to a deep crustal root under the whole of the Dinarides, supporting the hypothesis of a laterally continuous slab. In the last decade, several attempts have been made to untangle this conundrum but without much success. Nevertheless, these efforts have yielded some notable new findings, such as possible lithospheric delamination under the central Dinarides. This study aims to utilize all the available seismological results in combination with several new analyses to shed light on the upper mantle structure beneath the central Dinarides. We conducted the SKS shear-wave splitting analysis using 21 stations from the Croatian national seismic network and 7 stations from the AlpArray network. We considered events that occurred between 2010 and 2022 with magnitudes greater than MW = 6.0 and epicentral distances ranging between 85° and 120°. In parallel, a teleseismic Generalized Radon Transform (GRT) migration was conducted along a set of 2D profiles to provide structural insights into the subduction zone within the study area. Data from the Croatian national seismic network, the CRONOS temporary network, and the AdriaArray Temporary Network were used for the migration. For this approach, we considered events that occurred after January 2020 within the epicentral distance range of 30° - 100° and magnitudes greater than MW = 5.5. In addition to these two new analyses, we used other seismological results from previous investigations (including S-receiver functions and ambient noise tomography) to fill in the gaps in our investigation of the lithospheric structure under central Dinarides. Preliminary results exhibit distinctive patterns: the orientation of SKS fast axes, indicative of mantle flow, in the north and central External Dinarides aligns perpendicular to the mountain chain’s strike. However, this orientation abruptly transitions to a NW-SE direction further from the coast and continues in the northern part of Croatia. Results from converted/scattered-waves and ambient noise, for their part, point to a thickened crust under the central and southern External Dinarides, with a high-velocity anomaly reaching at least 100 km depth but a relatively thin lithosphere. Taken together these results suggest that the slab blocks the mantle flow up to depths of 100 – 150 km.

How to cite: Golub, L., Rondenay, S., and Stipčević, J.: Dinarides slab gap - fact or fiction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9709, https://doi.org/10.5194/egusphere-egu24-9709, 2024.

EGU24-9804 | ECS | Orals | TS2.6

AI based 3D P- & S-wave velocity model for the Alpine mountain chain from Local Earthquake Tomography 

Benedikt Braszus, Andreas Rietbrock, Christian Haberland, and Trond Ryberg

We present a new 3D P & S-wave model based on Local Earthquake Tomography (LET) of the European Alpine mountain chain using data from a total of more than 1100 broadband stations of the AlpArray Seismic Network and additional permanent and temporary stations. We use "SeisBench - A toolbox for machine learning in seismology" to assess the performance of the most commonly used AI pickers and find PhaseNet to be the most suitable. Our final data set comprises 2374 events of Ml >= 1.5 yielding 89,000 Pg-, 64,000 Pn-, 41,000 Sg- & 23,000 Sn-phases. Initially, we include observations from <130km epicentral distance to simultaneously relocate the quakes and invert for upper crustal velocity structure using the SIMUL2017 inversion algorithm. Subsequently, we add the remaining travel times to invert for velocities in the entire crust and upper mantle while fixing the hypocentres from the initial inversion run. 
First order features of our final vp model such as sediment basins and the Alpine orogenic root are in good agreement with previous tomographies and Moho studies of the area. In the Western Alps the well studied Ivrea Geophysical Body (IGB) is imaged as a high velocity anomaly where mantle velocities are present at depths of 15-20km. West of the IGB we find lower crustal velocities reaching depths of ~50km. Both observations are coinciding with the previously imaged Moho jump between deep European and shallow Adriatic Moho.
Similarly, we image the orogenic root in the Northern Apennines as an area of low vp with increased vp/vs-ratio. Beneath the Eastern Po plain we find mantle velocities at shallower depths than published Moho values would suggest. 

How to cite: Braszus, B., Rietbrock, A., Haberland, C., and Ryberg, T.: AI based 3D P- & S-wave velocity model for the Alpine mountain chain from Local Earthquake Tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9804, https://doi.org/10.5194/egusphere-egu24-9804, 2024.

EGU24-10513 | Orals | TS2.6

Where data-based structure meets process simulation - how heterogeneities relate to lithosphere deformation in the Alps 

Leni Scheck-Wenderoth, Ajay Kumar, Mauro Cacace, Judith Bott, Hajo Götze, and Boris Kaus

To address the question of how the present-day architecture of the lithosphere and the heterogenous density configuration of the uppermost mantle influence deformation in the Alpine orogenic system we use data-derived 3D configurations as input to dynamic simulations. This includes on the one hand the consideration of a detailed crustal model of the Alpine region and its forelands that resolves first-order contrasts in the thermophysical properties of the crust consistent with available geoscientific observables (active and passive seismic, gravity, geological, geothermal). In addition, we tested an ensemble of configurations of upper mantle thermophysical properties derived from published seismic tomography models. Using a Gibbs-free energy minimization algorithm (https://zenodo.org/records/6538257) we convert the results of regional shear-wave seismic tomography models to temperature models and define the base of the lithosphere and the geometry of slabs in the asthenosphere with a threshold temperature of 1300°C. As a first step we model topography and deformation velocities as resulting from buoyancy-forces driven by a quasi-instantaneous flow resulting from the first-order rheological structure of the lithosphere-asthenosphere system using the open source geodynamic code LaMEM (https://github.com/UniMainzGeo/LaMEM). The simulation results indicate that a slab detached beneath the Alps, but attached beneath the Northern Apennines captures first-order patterns in topography, vertical surface velocities, and mantle flow. The presence of an attached slab beneath the northern Apennines also explains the observed sub-crustal seismicity in contrast to the seismicity in the Alps restricted to the upper-crustal domain.

How to cite: Scheck-Wenderoth, L., Kumar, A., Cacace, M., Bott, J., Götze, H., and Kaus, B.: Where data-based structure meets process simulation - how heterogeneities relate to lithosphere deformation in the Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10513, https://doi.org/10.5194/egusphere-egu24-10513, 2024.

EGU24-10762 | ECS | Orals | TS2.6

Submarine canyons cutting through the Annot Sandstones, a key-element of the evolution of the Alpine Foreland Basin during the Rupelian 

Louison Mercier, Sébastien Migeon, Jean-Loup Rubino, Jenny Trevisan, Speranta-Maria Popescu, Mihaela Carmen Melinte Dobrinescu, Miroslav Bubík, Yamirka Rojas-Agramonte, Anna Hagen, and Romain Bousquet

Submarine canyons are commonly controlled by tectonic structures and, therefore, are key elements of the evolution of convergent margins such as the Southern French Alpine Foreland Basin. Here we use the outcrops of Grès d’Annot and Schistes à Blocs formations of the Sanguinière-Restefond and Trois Eveches sub-basins, to study the morphology of ancient canyons respectively in relation to extensive and compressive tectonics. The Grès d’Annot Upper Erosion Surface (GAUES) and faults have been mapped in the field and using airborne and drone pictures. Moreover, the deposition age of the Schistes à Blocs Formation has been constrained by the analysis of calcareous nannofossils and benthic foraminifera coming from 9 samples. We also compared ages of detrital zircons by U-Pb thermochronology from 4 samples. One of them was sampled within Annot Sandstones while the other come from the turbidites of the Schistes à Blocs Formation that seals the GAUES.

The Colombart Structure in the Sanguinière-Restefond area is composed of two normal faults with a N80°E orientation and a southern vergence, bordering a northward dipping rollover anticline. The Colombart Structure axially controls the 700 m deep La Bonette Canyon cutting through the underlying Annot Sandstones. The submarine canyon is made of a succession of sharp erosive features, such as erosive walls, ramps and terraces. The cross-section profile of the canyon exhibits a tectonic control at several scales: it is asymmetric as well as the thalweg is. Faults also commonly control smaller scale morphologies, but also the capture of tributaries at right angles with the canyon axis, which testifies for a rectangular drainage pattern. The preliminary study of the GAUES in the Trois Eveches Sub-basin also exhibits a strong relationship between tectonics and submarine erosion. The last shows a 300 m-high scarp frontally eroding a NW-SE oriented thrust which affects the underlying sandstones. Moreover, biostratigraphic dating of the Schistes à Blocs Formation indicates NP22-lower NP23 biozones, i.e. the Early Rupelian. Detrital zircons analysis by U-Pb method show that Annot Sandstones and Schistes à Blocs Formation have the same signal. Finally, within both sub-basins, the thin bedded turbidites of the Schistes à Blocs Formation exhibit paleocurrent directions which are almost opposed to those measured within the Annot Sandstones. Paleocurrents within the Trois Eveches Sub-basin also locally change depending on which thrusts is located below the Schistes à Blocs Formation.

Consequently, the GAUES mainly results from retrogressive erosion affecting partially lithified turbidites following two main triggering factors which are: i) the foreland deformation with a deformation direction that potentially locally changes, and ii) the 3rd order eustatic fall linked to the Oi1a δ18O event. The creation of submarine canyons affecting previously deposited turbidite lobes testifies of a strong paleogeographical modification of the foreland before the Autapie nappe emplacement. This change is also evidenced by the paleocurrent reorganization after the submarine erosion. Nevertheless, the complete understanding of the whole Early Rupelian source-to-sink system would need to enlarge the study of the Schistes à Blocs Formation to the whole foreland, including the use of other methods.

How to cite: Mercier, L., Migeon, S., Rubino, J.-L., Trevisan, J., Popescu, S.-M., Melinte Dobrinescu, M. C., Bubík, M., Rojas-Agramonte, Y., Hagen, A., and Bousquet, R.: Submarine canyons cutting through the Annot Sandstones, a key-element of the evolution of the Alpine Foreland Basin during the Rupelian, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10762, https://doi.org/10.5194/egusphere-egu24-10762, 2024.

EGU24-10978 | ECS | Orals | TS2.6

Coesite in Alpine meta-ophiolites: hidden but widespread, and tectonically relevant  

Stefano Ghignone, Federica Boero, Marco Bruno, Mattia Gilio, Emanuele Scaramuzzo, and Alessia Borghini

The occurrence of coesite, a Ultrahigh Pressure (UHP) index mineral,  in tectono-metamorphic belts is of paramount importance to pinpoint the depths attained during subduction. Such minerals are generally found as inclusions within garnets and are often the sole remnants of an UHP mineralogy in largely re-equilibrated rocks. UHP tectonometamorphic units in subducted oceanic lithosphere are of particular interest because they are natural laboratories to study element-exchange and fluid rock interactions occurring in a subducting slab at depths > 80 km. In this context, the meta-ophiolites of the Western Alps are a perfect case study, as they offer a continuous outcrop along the entire belt. Here, we focus on the UHP meta-ophiolites of the Internal Piedmont Zone (IPZ) in the Western Alps, where coesite inclusions in garnet have recently been found (Ghignone et al., 2023 and Boero, 2023). These localities lay on the same structural position of the Lago di Cignana Unit, wherein coesite was discovered in the early 90’s (Reinecke, 1991). In addition, these three UHP localities share similar metamorphic peak conditions and their PT estimates lie on the same metamorphic gradient (roughly 6°C/Km).

A targeted sampling campaign along the entire Western Alpine meta-ophiolitic belt allowed to better understand the distribution of coesite-bearing rocks. Metasediments (Grt-quartzite, Grt-Cld micaschist, Grt-calcschist) are the best lithotypes that preserved coesite, but also some meta-mafic lithotypes (eclogite, Grt-metabasite) contain it. Usually, garnets within metasediments are strongly zoned, whereas in meta-mafic lithotypes they have a more constant composition. Coesite was identified via µ-Raman spectroscopy, showing the typical vibrational modes of the phase (521, 427, 271 and 180 cm-1), slightly shifted due to elastic residual strain. Coesite occur as pristine tiny crystals (<40 µm) entirely trapped in garnet, both isolated and clustered. Their shape varies from well-faceted to strongly anhedral with morphological evidence of resorption (i.e., lobed morphologies with rounded shapes and/or embayment). Bigger inclusions of quartz (>40 µm) present the typical features of re-equilibration after coesite (i.e., radial cracks, polycrystalline aggregates). 

Among the different UHP localities, the presence of coesite is limited to a specific garnet shell (e.g., core, mantle), identifying a specific moment of garnet growth in UHP metamorphic conditions. The other shells, contrarily, preserve inclusions of quartz. These differences allowed to reconstruct the prograde or retrograde evolution through a detailed inclusion study of their preserved elastic properties (i.e., elastic geobarometry).

Our results highlight that the entire IPZ eclogite-facies meta-ophiolites underwent UHP metamorphism in the coesite stability field. This suggests that a large volume of oceanic lithosphere was subducted at ca. 100 km depth and then returned to the surface. This is an important constrain to create  reliable tectonic models of  subduction and exhumation of the oceanic lithosphere in collisional subduction/accretionary systems.

 

Boero, F., 2023. Master Thesis, University of Turin. 115 pp.

Ghignone, S., Scaramuzzo, E., Bruno, M., Livio, F., 2023. Am Mineral, 108(7), 1368-1375.

Reinecke, T., 1991. Eur J Mineral, 3, 7-17.

How to cite: Ghignone, S., Boero, F., Bruno, M., Gilio, M., Scaramuzzo, E., and Borghini, A.: Coesite in Alpine meta-ophiolites: hidden but widespread, and tectonically relevant , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10978, https://doi.org/10.5194/egusphere-egu24-10978, 2024.

EGU24-11066 | Posters on site | TS2.6

New insights into seismic structures around the Tauern Window and the Periadriatic Fault System from reprocessing of TRANSALP seismic reflection data 

Klaus Bauer, Benjamin Schwarz, Rahmantara Trichandi, Britta Wawerzinek, Peter McPhee, and Mark R. Handy

The TRANSALP project carried out around the Millenium provided unique geophysical sections across the orogenic structure in the Eastern Alps. Active and passive seismic experiments were conducted along a 300 km long profile between Munich and Venice. From North to South, the transect covered parts of the eastern Molasse Basin, the Northern Calcareous Alps and European Alpine crust, the Peninnic units of the Tauern Window, the Periadriatic Fault System (PFS), the Dolomite Mountains and Adriatic crustal indenter, and the foreland basin of the Venetian-Friulian plain. The comprehensive data sets were used to derive seismic velocity models, structural images from processing of seismic reflection data and Receiver Function analysis, azimuthal anisotopy from shear wave splitting, and to provide constraints for density modelling with gravity data.

More recently, new geophysical, mostly seismological experiments were conducted in the Central and Eastern Alps within the framework of the priority programme "Mountain Building Processes in Four Dimensions" (4D-MB) as part of the AlpArray mission. The general scope of this programme is to image the structure of the Alps from their surface down to lithospheric depth. A multi- and interdisciplinary approach is used to improve understanding of linked processes between surface and mantle beneath mountain belts, where integration of geophysical and geological observations with modeling enable to look backward and forward in time during these processes.

In the Eastern Alps, the pre-existing geophysical transects along TRANSALP (around 12°E) and EASI (around 13.3°E) are often used as reference sections to compare and discuss new 3D and 4D models along these 2D high resolution profiles. However, there is still controversy on the interpretation of these previous cross-sections. Of particular interest are crustal structures which can be used to test the hypothesized change of subduction polarity from S-directed subduction along TRANSALP towards N-directed subduction along the EASI profile, more eastward. Hence, in our sub-project we reprocess the pre-existing seismic reflection data along TRANSALP with promising, more recently developed methods that were not applied to this data set so far. The first approach is based on the extraction and usage of diffractions for the seismic imaging of the subsurface. Controlled numerical simulations explain the workflow and demonstrate the performance of the method. Application to the northernmost part of the TRANSALP seismic line reveals a number of sub-vertical structures which match with the location of known faults and fracture systems both in the Molasse and the Northern Calcareous Alps. The second approach is based on coherency analysis of pre-stack data. For the subsequent depth migration we test a wide range of existing velocity models, both from previous work and new results from the 4D-MB project. Most prominent sub-vertical structures are imaged in the central part of the Tauern Window and around the PFS. Ongoing tests with different velocity models are used to derive robust images of these key structures in the central part of the TRANSALP profile. The results are reconciled with surface geology and other geophysical studies, and will ultimately provide additional constraints for 3D and 4D geological modeling.

How to cite: Bauer, K., Schwarz, B., Trichandi, R., Wawerzinek, B., McPhee, P., and Handy, M. R.: New insights into seismic structures around the Tauern Window and the Periadriatic Fault System from reprocessing of TRANSALP seismic reflection data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11066, https://doi.org/10.5194/egusphere-egu24-11066, 2024.

EGU24-12811 | Posters on site | TS2.6

SECOS24: New insights into seismicity, deformation and crustal stresses in the Central Alps Region from a baseline seismotectonic earthquake catalog 

Tobias Diehl, Julia Heilig, Carlo Cauzzi, Nicolas Deichmann, John Clinton, Sandro Truttmann, Marco Herwegh, and Stefan Wiemer

The base data for any seismotectonic study consist of accurate and precise hypocenter information, consistent magnitude estimates, and focal mechanisms derived either from the analysis of first-motion (FM) polarities or moment-tensor (MT) inversions. In this study, we present a new baseline seismotectonic earthquake catalog of Switzerland and surrounding regions (SECOS24), which covers the Central Alps (CA) region between 45.4°N/5.6°E and 48.4°N/11.1°E. The SECOS24 catalog includes instrumental seismicity routinely detected and located by the Swiss Seismological Service (SED) between 1975 and 2024 (about 49 years). For the digital era of the SED bulletin (phase picks and seismograms available in digital form) starting in 1984, hypocenters were consistently relocated in absolute terms using a recent Pg and Sg 3-D velocity model. Starting from these improved hypocenters, double-difference relative relocations were performed at different scales (single clusters as well as at regional scales), combining differential times from manual picks and waveform cross correlations. Based on available solutions and resulting location quality, a preferred solution was selected for each hypocenter of the SECOS24 catalog, in order to provide the maximum possible hypocenter accuracy and precision for each event. The SECOS24 catalog contains about 36,000 earthquakes with magnitudes ranging between ML -0.7 to 5.3. In addition to ML, the catalog reports complementary magnitudes for a subset of events. For 71 events, an MW magnitude was derived from a revised MT inversion for events starting in 1999. For events since 2009, a spectral MW was calculated if possible. This magnitude compilation allows for the assessment and improvement of existing ML-MW scaling relations. Finally, we linked each hypocenter with the revised MT catalog as well as solutions of an augmented FM catalog, which contains 492 high-quality, manually reviewed mechanisms based on P-wave first-motion polarities.

The SECOS24 catalog is used for down-stream seismotectonic analysis of the CA region. In this presentation, we show updated maps of seismicity and moment release in the CA and their foreland. In addition, we provide updated maps of deformation regimes and stress orientations derived from the analysis and inversion of the FM data. Besides previously known features, the SECOS24 catalog reveals several new features in the CA and their foreland like newly imaged seismogenic fault zones, lateral changes in the deformation regime along the Alpine Front of the CA, and ongoing shortening at shallow crustal levels in the Jura fold-and-thrust belt. In addition, the updated stress inversion provides more stable results and, in several places, higher spatial resolution in comparison to previous studies. The SECOS24 catalog therefore contributes to an improved understanding of present-day tectonic processes in the CA region and is crucial input for next-generation seismic hazard models of the region.

How to cite: Diehl, T., Heilig, J., Cauzzi, C., Deichmann, N., Clinton, J., Truttmann, S., Herwegh, M., and Wiemer, S.: SECOS24: New insights into seismicity, deformation and crustal stresses in the Central Alps Region from a baseline seismotectonic earthquake catalog, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12811, https://doi.org/10.5194/egusphere-egu24-12811, 2024.

Mt. Moslavačka Gora (MG) is a small crystalline exposure in the western segment of the Sava suture zone (SSZ) that divides the Europe-derived Tisia and Dacia from the Adria-derived units. The MG differs from other crystalline exposures of the SSZ by the presence of Cretaceous LP/HT metamorphic rocks and Alpine S-type granitic pluton. Our study of geochemical variability, source characteristics and geodynamic setting is based on geochemical dataset for the two predominant Late Cretaceous granite types sampled throughout the northern and central part of the pluton: two-mica granites (TMG; Bt>>Ms) that comprise the main plutonic body and subordinate muscovite (± tourmaline) granites i.e. leucogranites s.s. (LG) that crosscut the pluton. Most of the samples are highly peraluminos granites (ASI 1.1-1.6) with high SiO2 content (70-77 wt %). They correspond to magnesian to ferroan alkali-calcic and calc-alkalic granites. Major element characteristics show decreasing TiO2 (0.42-0.03 wt %), MgO (1.09-0.04 wt %), FeOtot (2.47-0.38 wt %), Al2O3 (15.34-13.18 wt %) and CaO (1.45-0.19 wt %) with increasing SiO2, with lowest abundances in the LG type. The Zr, Th and La quantities decrease from TMG toward the LG samples, consistent with petrological observations and fractionation of accessory phases (zircon, monazite and apatite). REE patterns point to vapour-absent partial melting of metasedimentary source, presence of residual feldspar during partial melting and retention of monazite within residual biotite in the source, more pronounced in the case of LG. Our data suggests that LG samples are generated as minimum melts by reactions involving predominantly breakdown of muscovite. TMG samples show geochemical variability indicative of involvement of biotite in melting reactions. Rb, Ba and Sr content are consistent with the observed mineralogy and further corroborate low melt fraction vapour-absent or vapour-deficient melting conditions. Multiple diagrams (e.g. Al2O3/TiO2 vs. CaO/Na2O, A-B discrimination diagram) point to Pl-enriched source and higher melting temperatures for the TMG source whilst LG source corresponds to Pl-poor/clay-rich source and lower melting temperatures which is in good agreement with Zr saturation temperatures for both types (c. 730 °C for TMG and c. 650 °C for LG, respectively). Based on geochemical, mineralogical and field characteristics of Bt-dominated (TMG) and Ms (±Tur)-dominated (LG) granites, partial melting of different portions of crustal source composed of felsic igneous rock or immature metasediments under similar melting conditions seems like a plausible genetic model. Studied samples categorize predominantly as collision-related peraluminous granites. Previous research tentatively ascribed the origin of MG granitoids to partial melting induced by (localized) mafic magma underplating in a subduction/collisional setting of the SSZ. However, the presence of regionally metamorphosed metasedimentary rocks of amphibolite to granulite facies in the parts of the pluton supports the idea that localized strain heating has also contributed to the Late Cretaceous crustal melting and granite magmatism in the studied area or even had a dominant role. This is further corroborated by our geochemical data that point to derivation of TMG and LG from metasedimentary source similar to the exposed metamorphic rocks.

How to cite: Petrinec, Z., Mureta, L., and Balen, D.: Late Cretaceous peraluminous collisional granites from the Sava Suture Zone (Moslavačka Gora, Croatia): geochemical variability, source characteristics and geotectonic interpretation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15277, https://doi.org/10.5194/egusphere-egu24-15277, 2024.

EGU24-15665 | ECS | Orals | TS2.6

The 2021 and 2023 Vienna Basin seismic sequences: Insights from earthquake relocation and moment tensor inversion 

María del Puy Papí Isaba, Elisa Buforn, Maurizio Mattesini, Gesa Petersen, Simone Cesca, Helmut Hausmann, and Wolfgang Lenhardt

Three peculiar seismic sequences occurred between March and May 2021 near Breitenau and Gloggnitz, about 50 km from Vienna, Austria. The seismic sequences’ mainshock epicentres are less than 15 km apart. In March 2023, seismic activity resumed in the Gloggnitz area and continued to be relatively high in comparison with the average background seismicity of the region.

The first of these sequences started on March 30th, 2021, with the occurrence of an ML4.6 and h = 9 km earthquake close to Breitenau. A period of increased seismic activity lasted ~2 weeks, before decreasing to the background seismicity rate by mid-April. On April 19th, 2021, an earthquake with similar magnitude and depth (ML4.4 and 9 km) occurred only 1 km northeast of the previous ML4.6. The following seismic sequence lasted until the end of May 2021. The third seismic sequence started on April 20th, 2021, ~15 km SW of the Breiteau sequences, with a shallow (h = 5 km) ML3.5 earthquake followed by the mainshock (ML3.8 and h = 5 km) on April 23rd, 2021 (ML3.8 and h = 5 km). Seismicity decayed to background rates by early May. On March 30th, 2023, the seismic activity resumed in the Gloggnitz area with a mainshock (ML4.2 and h = 10 km). Its epicentre was located between the 2021 Gloggnitz foreshock (ML3.5) and the mainshock (ML3.8). Compared to the 2021 Gloggnitz sequence, there was no significant surge in seismic activity following the ML4.2 event, and the seismicity levels remained moderately high, compared to the typical seismic activity observed in the year 2021, until the beginning of October.

In this study, we relocated all events using a non-linear location method and used a probabilistic full waveform inversion tool to derive full moment tensor solutions for the largest earthquakes of the sequences (ML4.6, ML4.4, ML4.2 and ML3.8). These neighbouring sequences, which cluster spatially along a narrow seismicity band, but show different focal mechanisms and different temporal evolutions, shed light on the segmentation of local seismogenic processes and complex fault system along the seismogenic lineament.

How to cite: Papí Isaba, M. P., Buforn, E., Mattesini, M., Petersen, G., Cesca, S., Hausmann, H., and Lenhardt, W.: The 2021 and 2023 Vienna Basin seismic sequences: Insights from earthquake relocation and moment tensor inversion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15665, https://doi.org/10.5194/egusphere-egu24-15665, 2024.

EGU24-16122 | ECS | Posters on site | TS2.6

Provenance analysis of the Permo-Triassic Lantschfeld quartzite in the Austroalpine of the Radstädter Tauern, European Eastern Alps 

Johannes Rembe, Edward Sobel, Susanne Schneider, and Axel Gerdes

The Permo-Triassic shallow marine to continental deposits of the Alpine Verrucano and the Lantschfeld quartzite discordantly overly the Variscan basement in the Eastern Alps. The late Permian Alpine Verrucano is characterized by fine- to coarse-clastic (meta-)sediments with local calcareous and/or conglomeratic layers. The well sorted and more mature, early Triassic Lantschfeld quartzite is carbonate free, shows pale green to white coloring and rare conglomeratic layers. Both provide an important detrital record of post-Variscan landscape evolution. Investigations on non metamorphic Permo-Triassic units of the Northern Calcareous Alps (Haas et al., 2020) provided zircons connected to processes of the Pan-African, Cadomian and Variscan Orogenies. However, they show large disparities between different nappes. This underlines the varied character of the Variscan basement units, and a better understanding may provide interesting hints for the assignment of tectonic slivers to certain nappe complexes.

In this contribution we present detrital age spectra from the metamorphic Lantschfeld quartzite of the Lower Austroalpine Radstadt Nappe and the Upper Austroalpine Silvretta-Seckau Nappe System. By combing detrital zircon U-Pb dating with detrital rutile U-Pb and rutile geochemistry data, we can better trace the metamorphic history of the Variscan basement units contributing to the early Triassic basin fill.

Haas I, Eichinger S, Haller D, Fritz H, Nievoll J, Mandl M, Hippler D and Hauzenberger C 2020 Gondwana Research 77 204–22

How to cite: Rembe, J., Sobel, E., Schneider, S., and Gerdes, A.: Provenance analysis of the Permo-Triassic Lantschfeld quartzite in the Austroalpine of the Radstädter Tauern, European Eastern Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16122, https://doi.org/10.5194/egusphere-egu24-16122, 2024.

EGU24-16199 | Posters on site | TS2.6

Seismicity recorded by DIVEnet, a temporary network covering the northern Ivrea-Verbano Zone 

Simone Salimbeni, Judith Confal, Silvia Pondrelli, and György Hetényi and the DIVENet Team

As part of the ICDP-DIVE project (www.dive2ivrea.org), the temporary seismic network DIVEnet has been installed across the northeastern part of the Ivrea Verbano zone (IVZ). The DIVE project aims to find answers to fundamental questions about the lower continental crust and its transition to the mantle with two scientific boreholes and a combination of geochemical, geological and geophysical analyses. Since due to Alpine collision lower crustal rocks are at the surface, and the Ivrea geophysical body is at a very shallow depth (locally ~1±1 km b.s.l.), the site is unique and offers an excellent frame for new discoveries. The DIVE project includes a first drillhole DT-1B which has been completed in Ornavasso, and a second, currently ongoing DT-1A in Megolo. To monitor natural seismicity as well as drilling-induced noise and possible signals in the area, we have deployed DIVEnet in Autumn 2021, a temporary seismic network consisting of 13 seismometers. In September 2023, a broadband borehole instruments has been lowered in the first, completed borehole and is now recording at 250 m depth. This long-term monitoring produced a catalog of local seismicity that shows that the main seismic activity is located around the well-known principal tectonic lines of the region, i.e. the Insubric Line, which, geologically speaking, are considered as inactive. Seismic monitoring techniques have been redefined to improve the detection ability, which has become possible thanks to tested and continuously improved quality checks. Additionally we use the data for various geophysical analyses. Together with other permanent and temporary seismic stations in the region, receiver function analysis and its back-azimuthal harmonics are being calculated to get a better image of the IVZ by checking the presence of anisotropy in this anomalous body and its surrounding lithosphere.

 

 

How to cite: Salimbeni, S., Confal, J., Pondrelli, S., and Hetényi, G. and the DIVENet Team: Seismicity recorded by DIVEnet, a temporary network covering the northern Ivrea-Verbano Zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16199, https://doi.org/10.5194/egusphere-egu24-16199, 2024.

EGU24-16377 | ECS | Orals | TS2.6

The Alpine cooling history of the western Dolomites Indenter, European Southern Alps 

Thomas Klotz, Anna-Katharina Sieberer, Hugo Ortner, István Dunkl, and Hannah Pomella

The NW to N directed indentation of the Adriatic microplate into the European lithospheric domain, initiated in the upper Eocene following the closure of the Piemont-Liguria and Valais oceanic basins, constitutes a key feature of the Neoalpine orogenesis. The separation of the eastern Southern Alps (Dolomites Indenter) along the Giudicarie fault system from the late Oligocene (Middle Miocene at the latest) on and its increased northward push contributes significantly to major tectonic processes in the Eastern Alps north of the Dolomites Indenter: updoming, piggy-back top-N thrusting, and eastward lateral escape of the Tauern Window.

The interior of the Dolomites Indenter undergoes deformation as well, as documented, e.g., by the prominent, dominantly SSE-vergent fold and thrust belt of the Dolomites, as well as the top-WSW directed thrusts of the Dinaric chain and associated flysch sedimentation. New and compiled Apatite (U-Th)/He (AHe) and Fission Track (AFT) data allow the tracing of the exhumation history.

AFT data from the western Dolomites Indenter tend to cluster within consistent Dinaric and Neoalpine distinguishable tectonic blocks. However, the data are quite scattered. AHe data primarily indicate exhumation during the post-15 Ma Valsugana phase, showing a tendency of getting younger towards the east. A subordinate number of AHe datapoints document Eocene to Oligocene cooling as well.

Regional age-elevation profiles of consistent fault-delimited blocks exhibit (i) moderate cooling during the Mesoalpine Penninic subduction, (ii) fast Dinaric exhumation (in the Plose area), and (iii) fast Valsugana phase exhumation starting at approximately 15 Ma; Notably, this exhumation pulse starts earlier (Chattian/Aquitanian) in the northernmost tectonic block at the Indenter tip.

Time-temperature path modelling confirms the Valsugana phase as the most significant period of tectonic exhumation within the western Dolomites Indenter. According to the modeling, prior to this phase, a significant number of samples remained within the AFT annealing zone for an extended period of time, at least from Ladinian times onwards. This is due to a wide dispersion of single grain ages and suggests, the data does not necessarily represent a tectonic pulse. Moreover, many samples from sedimentary rocks of the Permian and Lower Triassic periods show a complete reset of the AFT system during the Middle Triassic, well before the maximum burial indicated by the stratigraphic record. This high-temperature anomaly could be attributed to the extensive Ladinian volcanism in the study area.

Based on the new thermochronological data, it can be inferred that the Middle Miocene Valsugana phase is the most significant exhumation phase in the Dolomites Indenter. Additionally, this phase begins earlier in the north than in the south. It is essential to consider the complex thermal history of the Dolomites Indenter and the possible long residence time of samples within the partial annealing zone prior to the Neoalpine exhumation when interpreting new data.

How to cite: Klotz, T., Sieberer, A.-K., Ortner, H., Dunkl, I., and Pomella, H.: The Alpine cooling history of the western Dolomites Indenter, European Southern Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16377, https://doi.org/10.5194/egusphere-egu24-16377, 2024.

EGU24-16390 | ECS | Orals | TS2.6

Subduction and exhumation of an Ultra-High Pressure oceanic slab in the Western Alps, new insights from the Lago Superiore Unit 

Emanuele Scaramuzzo, Franz Livio, Alessia Borghini, Mattia Gilio, Michele Locatelli, Federica Boero, and Stefano Ghignone

Ultra-high pressure (UHP) units sample the deepest portion of a subduction zone that returned to the surface, escaping their fate of disappearing deep into the mantle. Several mechanisms have been proposed for the exhumation of UHP units in collisional orogens but the topic remains still controversial and poorly understood.

The models invoked for the exhumation of UHP units generally require a positive buoyancy as trigger of exhumation. However, Ghignone et al. (2023) reported for the first time the occurrence of a slice tens of kilometres in length of oceanic slab, i.e., the Lago Superiore Unit (LSU), that reached UHP depth. This latter represents a portion of the former Alpine Tethys oceanic lithosphere now accreted within the Western Alpine collisional system (Ghignone et al., 2023).

In this contribution we present new insights on the subduction-accretionary processes preserved in the UHP Lago Superiore Unit. Our study is based on i) a new structural map of the LSU considering new data, ii) structural and kinematic field data, and iii) new prograde and retrograde P-T estimations calculated combining quartz-in-garnet elastic thermobarometry with Zr-in rutile and Ti-in-quartz thermometry.

Our new integrated kinematic and thermobarometric model suggests that the primary process driving the exhumation of the UHP Lago Superiore Unit was the progressive extraction of a composite metamorphic wedge. Final extension as revealed by thermobarometric constrain, allowed the exhumation of the Lago Suepriroe Unit at shallow crustal levels.

Ghignone, S., Scaramuzzo, E., Bruno, M., Livio, F., 2023. Am Mineral, 108(7), 1368-1375.

How to cite: Scaramuzzo, E., Livio, F., Borghini, A., Gilio, M., Locatelli, M., Boero, F., and Ghignone, S.: Subduction and exhumation of an Ultra-High Pressure oceanic slab in the Western Alps, new insights from the Lago Superiore Unit, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16390, https://doi.org/10.5194/egusphere-egu24-16390, 2024.

EGU24-16584 | Posters on site | TS2.6

Seismicity clusters in the Eastern Alps: New insights from the large-N Swath-D seismic network 

Rens Hofman, Gesa Petersen, Jörn Kummerow, and Simone Cesca and the The AlpArray Swath-D Working Group

The installation of the temporary, large-N Swath-D seismic network in the years 2017-2019 (Heit et al., 2021) provided the basis for the recent compilation of a high-resolution, consistently processed seismicity catalogue for the eastern and southern Alps (Hofman et al., 2023). The catalogue contains more than 6,000 earthquakes with magnitudes down to −1.7 ML.

 

In the present study, we analyse in more detail several of the newly detected microseismic clusters in the study area, which includes the most active parts of the Alps as well as particularly quiet regions with very little previously reported seismicity. We combine inter-event waveform similarity clustering, catalogue statistics and rupture mechanisms to characterise the clustered seismicity swarms and mainshock-aftershock sequences. We apply a relative location technique based on differential Ts-Tp arrival times to better resolve the seismogenenic structures. For subgroups of microseismic events with magnitudes Mw 1.2-3.0, we obtain moment tensor solutions using the flexible probabilistic inversion framework Grond, which allows to combine different fitting targets and frequency bands, while providing meaningful estimates of uncertainties (Heimann et al., 2018, Petersen et al., 2021). This adds to resolve subtle, but systematic variations of the inner-cluster seismicity.

Thanks to the outstanding network density, we can report a variability of seismic sequences and microseismic event mechanisms across the study area and interpret them with in terms of long-term tectonic and intermediate triggering processes.

How to cite: Hofman, R., Petersen, G., Kummerow, J., and Cesca, S. and the The AlpArray Swath-D Working Group: Seismicity clusters in the Eastern Alps: New insights from the large-N Swath-D seismic network, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16584, https://doi.org/10.5194/egusphere-egu24-16584, 2024.

EGU24-16705 | ECS | Posters on site | TS2.6

Changes in anisotropy with depth revealed by splitting intensity tomography beneath the Alps and surrounding regions 

Judith Confal, Paola Baccheschi, and Silvia Pondrelli

Complex tectonics and strong heterogeneity due to thickened crust, subducting lithosphere, and the movement of the surrounding asthenosphere can be well described by seismic anisotropy, a good indicator for active and past tectonic events. Most of methodologies adopted so far to reconstruct anisotropy have a poor depth resolution. To overcome this problem we are using splitting intensity, which is related to the energy on the transverse component of the waveform and is linearly related to the mediums elastic perturbations through 3D finite-frequency sensitivity kernels. Here, we have paid special attention to three regions: the Western Alpine orogen; the Upper Rhine Graben and the still active oceanic subduction in Southern Tyrrhenian region. We used 822 stations in the Central Mediterranean to compute 12480 splitting intensity measurements, afterwards they were inverted for depth dependent anisotropy. The 3D anisotropy models show a complex pattern in the shallower parts (60-100 km depth), becoming more aligned parallel to the slabs in the deeper parts (100-350 km depth) and influenced only by strong mantle flows. In the Upper Rhine Graben we are finally able to appoint an anisotropy pattern of NNW-SSE oriented fast polarisation directions, which are parallel to faults in the graben structure, to the lithosphere and a lower layer with orientations pointing NE-SW, to asthenospheric flow. While between 100 and 250 km depth the strength of anisotropy is very small. In the Western Alps we see complex shallow anisotropy pattern and possible mantle flow around the Alpine slab. Beneath the southern Tyrrhenian subduction system looking at the anisotropy tomography images we are able to identify circular mantle flow directions around the edge of the slab (beneath the Sicily Channel) and possible break-offs in the continuity of the slab.

How to cite: Confal, J., Baccheschi, P., and Pondrelli, S.: Changes in anisotropy with depth revealed by splitting intensity tomography beneath the Alps and surrounding regions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16705, https://doi.org/10.5194/egusphere-egu24-16705, 2024.

EGU24-17724 | ECS | Orals | TS2.6

Late Cenozoic evolution of the Dent Blanche Tectonic Nappe in the Western Alps imaged by low-t thermochronology. 

Lorenzo Gemignani, Julian Hülscher, Michele Zucali, Edward R. Sobel, Klaudia Kuiper, and Irene Albino

The Cenozoic uplift evolution of the Western Alps has been examined from various perspectives. Several studies have suggested that a Late Miocene-Pliocene European slab break-off, coupled with increased erosion due to enhanced glaciation, serves as a driving factor controlling the Western Alps topography. Alternatively, strain partitioning resulting from Adriatic indentation and Oligocene clockwise rotation leads to contrasting kinematic regimes, segmenting the Western Alps into blocks with differential exhumation. Here, we analyze the evolution of the Dent Blanche Tectonic System (DBTS), an Austroalpine nappe in the Western Alps surrounded by oceanic units from the former Liguro-Piemontese ocean.

We apply Low-T thermochronology (apatite and zircon (U-Th)/He) and high resolution mica 40Ar/39Ar dating from the DBTS. ZHe sample ages from the DBTS are ~30 Ma, with an extremely low eU sample from the lower elevation of the Valpelline Valley as young as ~7 Ma. AHe samples are younger, ranging from ~20 Ma to ~3 Ma. Reliable mica Ar ages range from the Paleocene to Oligocene. Most of the samples' age distributions have low radiogenic Ar yields (low 40Ar*), and part of the analyzed muscovite shows low K/Ca ratios, likely indicating chloritization.

Inverse modelling of the cooling ages from selected samples from the core of the DBTS (Arolla Units) shows that the exhumation rate of the DBTS is one-fold lower than the exhumation rates derived in the units north of the nappe. These rates are comparable with slower exhumation rates south of the nappe.

We propose that the DBTS system underwent its highest exhumation rates in the Oligocene to Late Miocene, predating the proposed Pliocene slab break-off as well as Pliocene increased glaciation. The identification of Pliocene-Pleistocene ages from one sample is interpreted to reflect glacial erosion localized in the Valpelline Valley; this is aligned with similar increased denudation rates since Pliocene observed in other Western Alps regions. However, this single cooling age does not provide conclusive evidence that glaciation drove the DBTS’s exhumation from ~3 Ma ago.

How to cite: Gemignani, L., Hülscher, J., Zucali, M., Sobel, E. R., Kuiper, K., and Albino, I.: Late Cenozoic evolution of the Dent Blanche Tectonic Nappe in the Western Alps imaged by low-t thermochronology., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17724, https://doi.org/10.5194/egusphere-egu24-17724, 2024.

EGU24-18831 | ECS | Posters on site | TS2.6

A critical review of petrological data in the Penninic domain of the Central Alps (Lepontine dome and its E-NE metasedimentary covers)  

Alessia Tagliaferri, Enrico Pigazzi, Sabrina Morandi, Paola Tartarotti, and Filippo Luca Schenker

In the Central Alps, the Penninic domain is formed by Europe-derived crystalline basement units that experienced a complex geodynamic history. This geodynamic history spans from subduction-related HP-LT (high pressure-low temperature) at ca. 38 Ma up to Barrovian metamorphic conditions peaked at ca. 31 Ma, followed by a more or less pervasive greenschist facies re-equilibration more evident in the northern units. This history led to the piling of polymetamorphic crystalline basement nappes that nowadays are up arched forming the Lepontine dome.

The Lepontine dome is a structural and metamorphic dome characterized by a widespread Barrovian metamorphic imprint. The temperatures of the Barrovian metamorphism increment towards the south and have a concentric distribution, locally intersecting the nappe contacts.

Here, we present a critical review of petrological data from the literature within the Lepontine dome, coupled with new temperature data computed with Raman spectroscopy acquired on the E-NE margin (up to the Tambo nappe) of the Lepontine dome. This work aims to identify the finite shape of isotherms at the base and on the roof of the Adula HP nappe and to trace the peak temperature conditions according to their relation to the Adula nappe emplacement (pre-, syn- or post- deformation). Two endmembers are envisaged in the literature: (1) a history where the temperature peak is attained during deformation and, according to thermodynamic studies, evolves from a single prograde PT loop, and (2) a post-deformation thermal peak formed after the HP deformation. The spatial distribution of rocks recording these different thermo-mechanical histories and the geochronological ages of the peak thermal conditions will help to postulate coherent geodynamic scenarios.

Petrological data from the Lepontine crystalline basement nappes point to peak conditions developed during nappe emplacement. On the other hand, the metamorphism and deformation of the northern metasedimentary covers suggest that a second thermal imprint is responsible for the peak temperatures registered close to the Adula nappe. This might suggest that the heat surplus developed during deformation of the Adula nappe was diffused to the close units also after its emplacement.

How to cite: Tagliaferri, A., Pigazzi, E., Morandi, S., Tartarotti, P., and Schenker, F. L.: A critical review of petrological data in the Penninic domain of the Central Alps (Lepontine dome and its E-NE metasedimentary covers) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18831, https://doi.org/10.5194/egusphere-egu24-18831, 2024.

EGU24-18901 | ECS | Orals | TS2.6

Stable isotope paleoaltimetry reveals Early to Middle Miocene along-strike elevation differences of the European Alps 

Armelle Ballian, Maud M. J. Meijers, Isabelle Cojan, Damien Huygue, Katharina Methner, Daniel Boateng, Sebastian G. Mutz, Walter Kurz, Emilija Krsnik, Horst Zwingmann, Yann Rolland, Todd Ehlers, Jens Fiebig, and Andreas Mulch

The European Alps, one of the most studied mountain ranges worldwide, are hypothesized to have experienced diachronous surface uplift resulting from slab-breakoff (Schlunegger and Kissling, 2018; Handy et al., 2015). However their surface elevation history is yet not well constrained (Campani et al., 2012; Krsnik et al., 2021; Botsyun et al., 2020). Quantifying surface elevation of an orogen through geological time is essential for our understanding of the geodynamic drivers, as well as the paleoenvironmental impacts of surface uplift.

Here, we present Early to Middle Miocene stable isotope-based paleoelevation reconstructions of the Western, Central, and Eastern Alps. Stable isotope paleoaltimetry (the 𝛿-𝛿 approach) is based on the systematic decrease of oxygen (𝛿18O) and hydrogen (𝛿D) isotopic composition of precipitation with increasing elevation and strongly benefits from contrasting high and low elevation records of past rainfall.

Accordingly, contrasting temperature-corrected near sea level pedogenic carbonate 𝛿18O values with time-equivalent 𝛿D values of K-Ar dated clay minerals from fault gouges allows for the calculation of the differential elevation between a foreland basin and an orogen’s interior through time. Recent paleoaltimetry research with focus on the Middle Miocene Central Alps indicates elevations exceeding 4 km (Krsnik et al., 2021).

With a spatiotemporally enhanced coverage of the European Alps, we present estimates of paleoelevation covering the time interval between ca. 23 and 12 Ma. In addition, paleoclimate simulations for a number of topographic scenarios allow for the isolation of contribution of local elevation complex climate change, and regional topographic configuration signals (Boateng et al., 2023).

Our quantitative stable isotope paleoaltimetry estimates indicate peak elevations of >4km in the Central Alps already during the earliest Miocene (ca. 23 Ma). 𝛿D values from fault gouge-derived illites are up to 25 ‰ higher in the Eastern Alps than in the Central Alps for the time interval between 21-16 Ma and suggest that the Eastern Alps were significantly lower during that time interval. Our results from the Mont Blanc massif are in line with isotopic measurements from fluid inclusions in quartz veins, which highlight the Mont Blanc massif in the Western Alps, did not exceed an average elevation of ca. 1 km until the end of the Miocene (Melis, 2023). Collectively, these results confirm a scenario of west-to-east surface uplift as suggested on the basis of slab-breakoff and tearing.

How to cite: Ballian, A., Meijers, M. M. J., Cojan, I., Huygue, D., Methner, K., Boateng, D., Mutz, S. G., Kurz, W., Krsnik, E., Zwingmann, H., Rolland, Y., Ehlers, T., Fiebig, J., and Mulch, A.: Stable isotope paleoaltimetry reveals Early to Middle Miocene along-strike elevation differences of the European Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18901, https://doi.org/10.5194/egusphere-egu24-18901, 2024.

EGU24-20494 | ECS | Posters on site | TS2.6

Pre to syn orogenic evolution of the Piedmont-Ligurian oceanic covers: clues on the Flysch units of the Western Ligurian Alps (CARG project – Ormea sheet 244).  

Simone Lombardi, Lorenzo Stori, Laura Federico, Laura Crispini, Seno Silvio, and Maino Matteo

The evolution of the European margin before and during the collisional phase of the alpine orogenesis is still a debated topic. The Western Ligurian Alps are a complex key area that can help to better understand this tectonic evolution. Here the contact between two different domains crops out: Briançonnais domain (European passive margin) and the Piedmont-Ligurian sedimentary covers (oceanic domain). These last units are characterized by several deformation stages, presented by many thrust sheets and non-cylindrical folds that make difficult to understand their relationships and their three-dimensional setting. Moreover, they are characterized by low-grade metamorphism that often masks their sedimentary structures and features, resulting in a challenging reconstruction of the pre-orogenic stratigraphic and structural setting. Previous works have hypothesized that these turbidite systems have been deposited in an abyssal plain resulted from the Piedmont-Ligurian Oceanic rifting and spreading. They are characterized by a lower part of basal complexes with thin bedded and very-thin bedded turbidites and often containing olistostromes. These basal complexes are overlain by sand- or carbonate-rich turbidite systems (Decarlis et al. 2014; Lanteaume et al.1990) that are interpreted as trench environment deposits (Di Giulio, 1992; Mueller et al. 2017). During the progressive advance of the accretionary wedge towards the European foreland, these units have migrated and stacked in reverse order, with the oldest one in the topmost part. The aim of the study is to review and integrate the previous works with new data following a multidisciplinary approach with a particular focus on the basal complexes of the flysch units. The CARG project is focused on the detailed fieldwork mapping that is already in progress with the aim of realizing the geological map of Ormea Sheet 244. During this activity, samples are collected for laboratory analysis. Specifically, petrographic characterization of samples collected in the basal complexes is currently carried out to better understand the source area of the sediments. Geochemical analyses are also in progress on basalt clasts found in the chaotic bodies. Another aim is to investigate the metamorphic grade by analysing fluid inclusions and vitrinite reflectance. Geochronological analysis will be performed with U/Pb analytical techniques on zircons to compare the results with surrounding crystalline basements to put an additional time constrain to the poor biostratigraphic data.

REFERENCES

Decarlis A., Maino M., Dallagiovanna G., Lualdi A., Masini E., Toscani G., Seno S., 2014. Salt tectonics in the SW Alps (Italy-France): from rifting to the inversion of the European continental margin in a context of oblique convergence. «Tectonophysics» 636, 293-314

Di Giulio A., 1992. The evolution of the Western Ligurian Flysch Units and the role of mud diapirism in ancient accretionary prisms (Maritime Alps, Northwestern Italy) «International Journal of Earth Sciences (Geologische Rundschau)» 81, 655-668

Lanteaume M., Radulescu N., Gavos., Feraud J., 1990. «Notice explicative, Carte Géol. De France (1/50000), feuille Viève-Tende» 948, Orleans, BRGM. 139 pp.

Mueller P., Patacci M., Di Giulio A., 2017. A Hybrid event beds in the proximal to distal extensive lobe domain of the coarse-grained and sand-rich Bordighera turbidite system (NW Italy). «Marine and Petroleum Geology» 86, 908-931

How to cite: Lombardi, S., Stori, L., Federico, L., Crispini, L., Silvio, S., and Matteo, M.: Pre to syn orogenic evolution of the Piedmont-Ligurian oceanic covers: clues on the Flysch units of the Western Ligurian Alps (CARG project – Ormea sheet 244). , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20494, https://doi.org/10.5194/egusphere-egu24-20494, 2024.

EGU24-20770 | Posters on site | TS2.6

Tectonostratigraphy of the Koralpe Mountain ridge (Eastern Alps) 

Ralf Schuster, Gerald Schuberth-Hlavač, Tanja Knoll, Heinrich Mali, and Annika Geringer

The investigated area of the Eastern Alps consists of Austroalpine basement units composed of various types of mica schist and paragneiss with intercalations of amphibolites or eclogites, marbles and quartzites. Furthermore, Permian magmatic rocks are represented by gabbros, pegmatites and the Wolfsberg orthogneiss. All rocks belong to the Koralpe nappe system and are characterized by main imprints during Permian HT/LP metamorphism and Cretaceous LT/HP overprint and nappe stacking in the course of the Eoalpine orogenic event. Geological maps show only a rudimentary tectonic subdivision, although there are indications for a complex internal structure. To study the internal structure a W-E orientated section across the Großer Speikkogel (2140 m) is most suitable. Along this section the E-dipping Cretaceous schistosity is gently folded by WNW-ESE trending axes with steep axial planes. From bottom to the top two amphibolite-facies, three eclogite-facies and again amphibolite-facies nappes can be identified. This indicates an inverted metamorphic field gradient in the footwall and an upright gradient in the hanging wall.

The tectonically deepest part crops out in the Wolfsberg Window, where amphibolite-facies rock units of the northerly-situated Gleinalpe Mountains reappear at the surface. They comprise the Vordergumitsch nappe, which is mainly built up by biotite-rich mica schist, paragneiss and amphibolite of the Klining Complex. Additionally it includes the Wolfsberg orthogneiss. Above the Pusterwald nappe is situated. It is built up by the Rappold (Preims) Complex, mainly composed of garnet-bearing mica schist, paragneiss and marble with additional amphibolite, quartzite and pegmatites. The latter show relatively low grades of fractionation.

The lowermost eclogite-bearing unit is the several hundred meters thick Brandhöhe nappe. It represents an upright section through the lower and middle part of the Permian crust. Its lower part mainly consists of paragneiss, which experienced high amphibolite-facies and anatexis during the Permian event. Usually it contains several millimetres large aggregates of fine-grained kyanite ("Disthenflasergneis"). In the upper part paragneiss with up to several decimetres long kyanite pseudomorphs appears, which developed from Permian greenschist-facies schists with chiastolitic andalusite ("Paramorphosenschiefer”). Within the metasedimentary matrix some huge eclogite bodies appear. While pegmatitic mobilisates and weakly fractionated simple pegmatites occur in the lower part of the succession, fractionated pegmatites and spodumene pegmatite dikes of the Weinebene locality are situated in the upper part. Maybe the spodumene pegmatites from Trahütten and Klementkogel are also at this level. The overlying Hoher Speikkogel nappe is characterised by migmatic paragneiss again. Its upper boundary is masked by the Plattengneis shear zone. Therein, thick evolved pegmatites occur near the base, whereas above only millimetre thick pegmatitic mobilisates appear. This transition marks the base of the overlying Deutschlandsberg nappe. In its less deformed upper part bodies of Permian gabbro-eclogite, the leucogranite of Trahütten and most probably the spodumene pegmatite of the Gupper quarry are situated.

Along the western foothills of the Koralpe Mountain ridge amphibolite-facies rock assemblages are dominated by garnet mica schist. It is yet not clear whether they represent one continuous nappe sheet or several nappe sheets.

How to cite: Schuster, R., Schuberth-Hlavač, G., Knoll, T., Mali, H., and Geringer, A.: Tectonostratigraphy of the Koralpe Mountain ridge (Eastern Alps), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20770, https://doi.org/10.5194/egusphere-egu24-20770, 2024.

In Neogene time, the Eastern Alps underwent a profound tectonic reorganisation. This featured northward indentation of the Alpine orogenic wedge by the Adriatic plate, eastward lateral extrusion between conjugate strike-slip faults, and a shift from thrust propagation on the European lower plate to the Adriatic upper plate. We investigate the triggers of this reorganisation with new sequentially restored orogen-scale cross-sections along the TRANSALP (12°E, western Tauern Window) and EASI (13.3°E, eastern Tauern Window) transects, plus an E-W orogen-parallel cross-section (46.5°E). We use a map-view reconstruction to restore the effects of out-of-section transport by lateral extrusion and compare our results with P-wave local earthquake (LET) and teleseismic tomographic models of the crust and upper mantle.

The geologic record reveals two phases of indentation: Phase 1 (c. 23-14 Ma): The Adriatic Plate was an undeformed indenter, with northward motion relative to Europe accommodated by sinistral motion along the Giudicarie Fault and shortening within the Eastern Alps orogenic wedge. Upright folding of nappes mostly derived from the downgoing European Plate, and lateral extrusion of the entire metamorphic edifice and North Calcareous Alps accommodated this N-S shortening. This shortening required ongoing subduction of European lithosphere, ruling out previous models involving north-dipping Adriatic subduction. A purported detachment below the Venediger Nappes may have served as the base of the laterally extruding wedge.

Phase 2 (c. 14 Ma-Present): The leading edge of the Adriatic indenter has been deforming since c. 14 Ma, forming the thick-skinned South Alps fold-thrust belt. The onset of S-directed thrusting is recorded by Langhian-Serravallian flysch in the footwall of the Valsugana thrust. The Adriatic lower crust was decoupled and transported northwards into the orogenic wedge, indenting and exhuming the deeply buried equivalents of the Venediger Nappes in the Tauern Window. A high-velocity (6.8 - 7.25 km/s) bulge in LET models of the TRANSALP section images this indenter, which comprises mostly Adriatic lower crust, but possibly also includes some accreted European lower crust.

In P-wave teleseismic tomography along the EASI section, the European slab appears to be detached at a locus marked by a Moho gap and a shallow discontinuity in the positive velocity anomaly beneath the orogenic wedge. In contrast, no such discontinuity occurs beneath the TRANSALP section, where S-dipping European lithospheric mantle still extends beneath and south of the orogenic wedge. If the southern end of this relict slab segment marks the locus of a detachment, we find that the current slab length is less than the amount of N-S shortening in the TRANSALP section since 23 Ma. To explain this mismatch, we propose that the most recent slab detachment in the Eastern Alps event occurred after 23 Ma, and likely after 14 Ma (Phase 2 indentation). Note that this does not preclude earlier detachment events, notably at 22-19 Ma when the eastern Molasse Basin rapidly filled and orogenic vergence shifted from north to south (see Handy et al., this session).

How to cite: McPhee, P. and Handy, M.: Post-collisional reorganisation of the Eastern Alps in 4D – Crust and mantle structure, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21023, https://doi.org/10.5194/egusphere-egu24-21023, 2024.

EGU24-21804 | Posters on site | TS2.6

3D Geomodelling of Alpine structures: the Misox Shear Zone (Swiss) 

Riccardo Monti, Andrea Bistacchi, and Stefano Zanchetta

3D models are fundamental tools for studying the evolution of complex geological structures, such as shear zones in the metamorphic core of the Alps.
The study’s case is the area of the San Bernardino Pass (Swiss), focusing on the study of the structural and metamorphic evolution of HP units outcropping here.
The area of the San Bernardino Pass is part of the Penninic domain, an Alpine domain consisting of continental and oceanic crust derived from the distal margin of Europe, subducted during the Alpine orogeny.
In this area, the Adula nappe is in contact with the overlying Tambò nappe (part of the eastern flank of the Lepontine Dome) along a wide shear zone of several hundreds of metres.
This work is focused on the 3D modelling of the shear zone and the superposed fold system developed within the Adula nappe, in the hanging wall of the shear zone
Starting from original field data and available geological maps, structures were approximated and drawn using the open-source software QGIS to create a simplified geological-structural map.
These data are fundamental constraints for drawing geological sections using the open-source software PZero (https://github.com/andrea-bistacchi/PZero).
After careful reconstruction of serial geological cross-sections in PZero, advanced interpolation techniques such as implicit methods can be applied to develop accurate geological models.

PZero is an open-source software currently in development, dedicated to 3D geological modeling, featuring a user-friendly interface designed for structural geologists.

How to cite: Monti, R., Bistacchi, A., and Zanchetta, S.: 3D Geomodelling of Alpine structures: the Misox Shear Zone (Swiss), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21804, https://doi.org/10.5194/egusphere-egu24-21804, 2024.

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