EGU General Assembly 2022  

The geochemical toolkit is pertinent to fields other than that of Earth and Planetary Sciences for which it is traditionally and commonly used. Here we show two recent examples of its application to numismatics, archaeology, and ancient history. High-precision Pb isotopes treated by novel statistical tools were used to provide data-based answers to important research questions revolving around the sources of silver used for money, jewelry, and other valuable artefacts in the ancient world.

In the first example, we studied remnants of the silver making up the largest treasure of precious metals reported in ancient Western history, namely that of Alexander the Great which he looted in his conquest of the Persian Empire, by analyzing a large set of ancient silver coins (alexanders, sigloi, Greek coins, and early Indian pseudo-coinage) for their Pb isotopic compositions. The high-precision data were treated using a new statistical approach in the form of calculated Pb model ages combined with cluster analysis and convex-hull theory, which allows the tracking of silver provenance with greater accuracy and precision than was previously possible when using only raw Pb isotope ratios and manually comparing artefacts with known ores on a one-to-one basis. Based on the Pb isotopic compositions of the analyzed silver coins compared with a ca. 6700-entry Pb isotope database on ores that we have compiled from the literature and our own work, we established that the bulk of the silver sources can be traced to the southern Aegean, Macedonia, and Thrace [1]. These origins had so-far only been the subject of speculation by numismatists, archaeologists, and historians, whereas now they are supported by high-precision isotope data and objective data analysis. Furthermore, we were able to confidently exclude India as a source [1], thereby putting to rest a long-standing debate around a possible Indian silver contribution to the Persian treasury.

In the second example [2], we measured high-precision Pb isotopes on pieces of hoarded Hacksilber (irregularly cut silver bullion) in the southern Levant, which facilitated trade and transactions from the beginning of the second millennium BCE until the late fourth century BCE. In a similar fashion to the first example, we treated the data using cluster analysis and convex-hull theory applied to Pb model ages calculated from measured high-precision Pb isotopic compositions. We found that exchanges between the Levant and the Aegean world continued at least intermittently from the Late Bronze Age through to the Iron Age III. Importantly, contrary to common belief that silver trade had come to an end following the Late Bronze Age collapse, we demonstrated that despite the Aegean world dominating silver supply during the Iron Age, exchanges between the eastern and the western Mediterranean did not cease altogether. People around the Mediterranean remained connected with silver flowing to the Levant possibly as a result of trade or plunder.

[1] Blichert-Toft, J., de Callatay, F., Télouk, P., Albarède, F., submitted. J. Archaeo. Meth. Theo.

[2] Gentelli, L., Blichert-Toft, J., Davis, G., Gitler, H., Albarède, F., 2021. J. Archaeo. Sci. 134, Article 105472.

How to cite: Blichert-Toft, J., Gentelli, L., Davis, G., Gitler, H., de Callataÿ, F., and Albarède, F.: When Geochemistry encounters Archaeology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1035, https://doi.org/10.5194/egusphere-egu22-1035, 2022.

The controls on the style of silicic eruptions – hazardously explosive, more gently effusive, or hybrid explosive-effusive – are poorly constrained. Current models invoke escape of gas through a connected foam, or through fractures, as the primary mechanism for the transition from explosive to effusive eruption. We propose a new model, in which hybrid and effusive silicic eruptions are typically explosive at depth, but the clastic products of this 'cryptic fragmentation' sinter and weld in the conduit to produce coherent lava at the surface. Drawing on numerous case studies of natural textures within eruptive products and dissected conduits, we show that effusive silicic eruptions are best interpreted as being the welded, squeezed-out remnant of ongoing or recent subsurface explosive behaviour. We demonstrate that effusively erupted lavas have microtextures diagnostic of a welding/sintering genesis and are comparable with those found in rheomorphic and welded ignimbrites. All eruptive products share pore network geometries and associated mechanical and hydraulic property-porosity relationships that are consistent with models for sintered materials. We conclude that silicic lava is generally clastogenic, and that, after it is sinter-assembled, it may undergo gas-driven fracturing that produces lava plug-cutting tuffisites (closed fractures filled with sintered particles), and sintered pyroclasts (from ash- to bomb-sized). At some sites (e.g. Volcán Chaitén 2008), the first material to be extruded from the vent is a pyroclastic rubble similar texturally to the volcanic bombs from the same site. We propose therefore that the shallow conduit is filled with pyroclastic and lithic rubble; a volume that variably compacts over time to produce a plug of densified lava. Envisaging the shallow conduit as a compacting rubble pile instead of a coherent magma-filled pipe or crack leads us to posit that the explosive-effusive transition is a blurred behavioural switch controlled by the competition between material supply at the underlying fragmentation front, and shallow particle capture, welding and lava production above. This framework has broad top-down implications for geochemical and geophysical predictions of shallow silicic volcanism, which we will explore in this presentation.

How to cite: Wadsworth, F. B., Llewellin, E. W., Vasseur, J., Gardner, J. E., and Tuffen, H.: A reappraisal of explosive-effusive silicic eruption dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13600, https://doi.org/10.5194/egusphere-egu22-13600, 2022.

Stable oxygen isotopic composition (δ¹⁸O) of CO₂ produced from carbonates in natural archives is a useful proxy for paleo precipitation and paleo temperature reconstruction. However, there exist multiple factors controlling the δ¹⁸O values, the applications of the δ¹⁸O alone for paleoclimate studies are thus limited. Anomaly in ¹⁷O in carbonates, expressed by Δ′¹⁷O=1000*ln(δ¹⁷O/1000+1)-λ*1000*ln(δ¹⁸O/1000+1) is another proxy to independently constrain aspects of climatic variables such as precipitation source variation and kinetic effects during carbonate precipitation. However, to use ¹⁷O anomaly for such studies, the triple oxygen isotope fractionation exponent (θ= lnα¹⁷/lnα¹⁸) must be known precisely. Knowledge of this parameter is central to emerging applications of carbonate triple oxygen isotopes to paleoclimate and paleo-hydrology studies. Though a number of theoretical and experimental studies have been carried out in the last few years, there remains no consensus on 𝛳 value for carbonate-water system, likely due to kinetic isotope fractionation during precipitation.

Here, we measured Δ′¹⁷O in synthetic carbonates as well as in the water from which the carbonates are precipitated to check how reliable the Δ′¹⁷O value of the parent water can be reconstructed from the carbonates or carbonate-digested CO₂. To determine θ_{carbonate_CO2-water} for precipitated carbonates, we synthesized carbonates in the laboratory at temperatures ranging from 10 ⸰C to 66 ⸰C using passive/active CO₂ degassing method. Triple oxygen isotope compositions of the water were determined using water-CO₂ equilibration followed by CO₂-O₂ exchange method and of the carbonate (CO₂ liberated by acid digestion) using CO₂-O₂ exchange method. We analyzed our isotope data for their possible kinetic isotope effect and determined the 𝛳_{carbonate_CO2-water} value for precipitated carbonates. We find that most of our synthetic carbonate samples did not attain the equilibrium. The 𝛳_{carbonate_CO2-water} increases as the disequilibrium effect increases. We determined the θ_{carbonate_CO2-water} from the samples precipitating in equilibrium. Furthermore, we do not find any differences in the 𝛳_{carbonate_CO2-water} value for carbonate precipitated in equilibrium at 25 ⸰C and 35 ⸰C. An important issue of using Δ′¹⁷O in carbonates is to resolve the 𝛳_acid for acid digestion which is resolved in the present study. Additionally, we determined the temperature dependent variation in 𝛳_acid and find no significant changes between 0 ⸰C and 70 ⸰C.

How to cite: Roy, P., Laskar, A., and Liang, M.-C.: Triple oxygen isotope fractionation of carbonate during carbonate precipitation and acid digestion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-626, https://doi.org/10.5194/egusphere-egu22-626, 2022.

Correlative analytical approaches involving high-spatial resolution microscopy techniques allow for the compositional measurements and spatial imaging of materials at the near-atomic scale. By combining electron backscatter diffraction (EBSD) mapping, electron channeling contrast imaging (ECCI), scanning transmission electron microscopy (STEM) and atom probe tomography (APT) on various geological materials such as minerals and glasses, we have successfully documented element mobility regulated by structural defects. Although these techniques were initially developed in the materials sciences, they are now being applied to a broad range of applications within many subdisciplines of geosciences including geochemistry, geochronology, and economic geology. In one set of experiments, we applied a correlative approach on naturally deformed pyrite from an orogenic gold mine in northern Canada to assess the impact of crystal-plastic deformation on the remobilization of trace elements. This study has led us to propose a new paragenetic model for metallic ore deposits in which deformation creates nanostructures that act as traps for base- and precious-metals. By applying our approach on pyrite that is rich with fluid inclusions, we have also documented two processes that led to proposing a new fluid inclusion-induced hardening model, which is in contrast to the more commonly reported weakening effect of fluids on minerals. To broaden the applications of our approach, we have applied the same suite of analytical techniques to a synthetic andesitic glass to assess whether nanoscale chemical heterogeneities can act as nucleation sites for gas bubbles. The combined results demonstrate the existence of nanoscale chemical heterogeneities within the melt and at the bubble-melt interface supporting the hypothesis that homogeneous nucleation could in fact be a variety of heterogeneous nucleation. The interactions between trace elements and structural defects plays a vital role in determining the mechanical properties of minerals, particularly in fluid-rich environments. These sub-nanometer scale exchanges consequently control meso- to tectonic-scale geological processes. Our research work not only demonstrates the latest advancements in analytical microscopy resolving long-standing geological problems but also brings us closer to bridging the gap between the fields of materials sciences and geosciences.

How to cite: Dubosq, R., Schneider, D., Rogowitz, A., and Gault, B.: Unraveling the secrets of the Earth through nanogeology: A correlative microscopy approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1186, https://doi.org/10.5194/egusphere-egu22-1186, 2022.

Understanding earth materials is critical to creating a sustainable, carbon-neutral society. Earth materials control the feasibility of subsurface energy storage, geothermal energy extraction, and are a source of critical elements for future-proof battery technologies. Perturbations to geological systems can also result in hazards, such as human-induced earthquakes. If we want to tackle the current, pressing scientific questions related to sustainable development for a circular economy, there is an urgent need to make multi-scale, multi-dimensional characterisations of earth materials available to a broad spectrum of earth-science disciplines. In addition to the society-relevant topics, the properties of earth materials determine how the Earth workson the most fundamental level.To overcome this challenge, 15 European facilities for electron and X-ray microscopy join forces to establish EXCITE. EXCITE is a Horizon Europe infrastructure project, and enables access to high-end microscopy facilities and to join the knowledge and experience from the different institutions. By doing so, EXCITE will develop community-driven technological imaging advancements that will strengthen and extend the current implementation of leading-edge microscopy for earth-materials research. In particular, the EXCITE strategy is to integrate joint research programmes with networking, training, and trans-national access activities, to enable both academia and industry to answer critical questions in earth-materials science and technology. As such, EXCITE builds a community of highly qualified earth scientists, develops correlative imaging technologies providing access to world-class facilities to particularly new and non-expert users that are often hindered from engaging in problem-solving microscopy of earth-materials.This presentation gives an overview EXCITE, its activities and open calls, and the progress of the first year of the project.

How to cite: Walter, S., Cnudde, V., Plümper, O., and ter Maat, G.: EXCITE: A European infrastructure to promote electron and X-ray microscopy of Earth materials, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2517, https://doi.org/10.5194/egusphere-egu22-2517, 2022.

Due to the fine-grained nature of shale, organic matter particles are generally micro- and nano-scale in size. Functional groups differ between different organic matter types and as such provide unique chemical information for organic matter. Micro-FTIR can provide direct measurement to characterize sample features at the micrometer scale. However, optical diffraction limits its application at the nanometer scale. As a non-destructive high-resolution scanning probe technique, atomic force microscopy (AFM) is very powerful in nanoscale research and has been widely used in the fields of polymers, semiconductors, electrochemistry and biology. To provide a better combination of AFM’s unique advantages with nanoscale chemical analysis, the AFM-IR technique has been developed in recent years and also attracted the attention of geologists to explore the application in geological materials.

In this research, AFM-IR which is a quite new technique in geological research was used to investigate the in-situ geochemical characteristics of organic matter in shale. Nanoscale molecular composition of individual organic particles was captured nondestructively, and the distribution of typical functional groups was displayed via 2D IR mapping. In our samples, both alginite and inertinite display chemical homogeneity. The former is dominated by oxygenated and aliphatic contents which indicates a higher hydrocarbon generation potential, whereas the latter is dominated by aromatic carbon. In contrast, migrated solid bitumen particles show compositional heterogeneities at the nanometer scale as some are aromatic-rich and others are aliphatic-rich. Finally, linking this advanced nanochemical technique to potential applications in subsurface energy was explored. This research demonstrates that AFM-IR is a powerful tool to examine the in-situ nanoscale geochemical characteristics of different organic matter types, which can also provide implications for energy applications.

How to cite: Wang, K., Ma, L., and Taylor, K. G.: In-situ nanoscale geochemical characterization of organic matter in shale by AFM-IR, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3234, https://doi.org/10.5194/egusphere-egu22-3234, 2022.

Geochronology is fundamental for the understanding of rates and mechanisms of Earth processes, including tectonics, crust formation, ore formation and magmatism. Analytical techniques are mostly applied to the mineral zircon, particularly LA-ICPMS and ID-TIMS dating, which offer the required accuracy, precision and analytical throughput to solve outstanding scientific questions. However, zircon can record multiple geological events within discrete crystallographic domains, so it is crucial to ensure that measurements are completed using optimal precision and accuracy while specifically targeting crystal domains of interest to resolve potentially complex zircon systematics. We explore here a case where the combination of xenocrystic and autocrystic growth zones within same crystals, together with decay damage related lead loss, leads to apparently protracted age spectra, which can erroneously be interpreted in terms of magmatic evolution.

We present LA-ICP-MS and ID-TIMS U-Pb zircon data from a Variscan, 335 Ma old granodiorite from the Alpine basement in the Aar massif (Switzerland), which highlight the potential complexities present in zircon samples and address the need for careful zircon pre-treatment. CL imagery of zircon reveals minor but pervasive secondary alteration, leading to the observed excess scatter in LA-ICPMS dates. Chemical abrasion (CA) as a pre-treatment prior to LA-ICPMS analysis significantly reduces this scatter. CA-ID-TIMS analyses of zircon from this sample yield extremely high precision due to very high radiogenic/common Pb ratios (Pb*/Pb_c), with significant ²⁰⁶Pb/²³⁸U scatter. Due to the elevated precision of these analyses, it is possible to resolve a linear discordance for these data. This indicates that Pb-loss is not the only age component observed, and the volume of zircon analyzed via CA-ID-TIMS does not purely reflect Variscan igneous crystallization. Since CL images also show thin and poorly visible metamorphic rims, we carried out a physical abrasion (PA) pre-treatment prior to chemical abrasion to isolate the Variscan zircon zones from later Alpine overgrowth for CA-ID-TIMS analysis. We interpret a high-precision PA-CA-ID-TIMS ²⁰⁶Pb/²³⁸U age of 335.479 ± 0.041/0.096 Ma (internal non-systematic/external systematic error; MSWD=0.27) as best estimate for Variscan zircon crystallization for this sample. This age overlaps with the result of CA-LA-ICPMS analyses when properly accounting for the total analytical uncertainty, including matrix effects on concentration ratio standardization.

From these data we conclude: (1) mixing of two age components in zircon may lead to an apparent protracted range in ²⁰⁶Pb/²³⁸U age, which can be resolved if isotope analyses yield very high Pb*/Pb_c ratios and thus are very precise. At lower precision zircon age spectra can be erroneously interpreted as reflecting protracted growth, since they will overlap concordia due to elevated ²⁰⁷Pb/²³⁵U uncertainties, as well as in between individual ²⁰⁶Pb/²³⁸U ages. (2) By combining physical and chemical abrasion, we can resolve the observed complexities, by selectively analyzing zircon domains of interest while simultaneously mitigating diffusive Pb-loss. (3) This study shows how analytical precision may dramatically impact on scientific interpretation, as less precise data can easily be mistaken to reflect prolonged magmatic growth, rather than two-component mixing with xenocrystic material. This difference can significantly impact the interpreted lifespan of magmatic systems.

How to cite: Schaltegger, U., Gaynor, S. P., Ruiz, M., and Ulianov, A.: Protracted U-Pb age spectra from complex zircon crystals resolved using high-precision geochronology and selective sample pre-treatment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3540, https://doi.org/10.5194/egusphere-egu22-3540, 2022.

Dating of the extrusive parts of large igneous provinces has been a challenge because of the lack of mineral phases that can be dated by high-precision techniques. This is the case for the rapidly emplaced Drakensberg lavas, part of the Karoo LIP in South Africa and Lesotho. The circulation of hot fluids through the lava stack during rapid emplacement of continental flood basalts develops relatively high degrees of fracturing and alteration of the rocks, which often results in the re-opening of isotopic systems and inaccurate dates. This alteration occurs on varying length scales, from the outcrop to the micrometric scales, creating Argon loss in minerals of interest for ⁴⁰Ar/³⁹Ar dating (i.e. plagioclase) and making the procedure of separation for step-heating ⁴⁰Ar/³⁹Ar a tedious and sometimes ineffective task. Here, we re-approach measuring ⁴⁰Ar/³⁹Ar by directly analyzing leached and unleached thin sections without having to go through mineral separation, and therefore effectively eliminating the mixing issue of mechanically separating the plagioclase crystals. Half of each plagioclase aliquot was leached in acid, and then irradiated at the TRIGA reactor (Oregon State). We used a 193nm excimer UV-laser attached to a noble gas extraction and purification line, and an Argus VI mass spectrometer at the University of Geneva on thick sections for in-situ analysis. Plagioclase separates from the same Karoo lava flow samples were previously analyzed for ⁴⁰Ar/³⁹Ar geochronology using step heating, on aliquots of both leached and unleached plagioclase separates, using the same noble gas analytical equipment. This allows for a direct comparison of the in-situ­ analysis, testing the potential differences between the two different analytical systems and a potential way of assessing differences in accuracy between the two. Preliminary results show that accurate ages can be achieved by this technique at the cost of a larger precision.  

How to cite: Antoine, C., Spikings, R. A., Gaynor, S. P., and Schaltegger, U.: 40Ar/39Ar In-Situ Dating of Altered Mafic Rocks in the Karoo Large Igneous Provinces., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3987, https://doi.org/10.5194/egusphere-egu22-3987, 2022.

Hydrous lattice point defects (OH defects) in quartz (SiO₂) occur through coupled substitution of Si⁴⁺ with a trivalent cation (most commonly Al³⁺) and a hydroxyl group (OH^-). These impurities can be used to investigate its host rock’s crystallization history and may therefore also serve as a tracer for sediment provenance analyses, but are also economically relevant (e.g., high purity quartz sources).

Transmission infrared (IR) spectroscopy has proven to be a very effective method to analyze OH defects down to concentrations of a few weight parts per million water equivalent. This technique, however, requires thin (100 to 200 µm), polished quartz wafers that are cut perpendicular to the crystallographic c-axis. Preparation of a statistically significant number (i.e. > 100) of grains using this approach is very time consuming and requires a skilled operator. Furthermore, IR spectral analysis so far does not follow a standardized protocol, possibly introducing individual biases and hampering reproducibility of as well as comparability between datasets.

In this work, we present a new, standardized procedure for sample preparation, measurement, and data analysis of OH defects in quartz. Sample preparation and IR measurements are significantly sped up and simplified and require relatively little specialized laboratory equipment. Additionally, our data analysis is performed largely automated and based on spectral deconvolution and generation of synthetic spectra before quantification, ensuring quick generation of reproducible results. This new protocol may therefore be another step towards making OH defect analysis accessible to a wider range of geoscientific fields.

How to cite: Jaeger, D. and Stalder, R.: Quantification of OH in quartz via infrared spectroscopy – new protocol for sample preparation and spectral analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4954, https://doi.org/10.5194/egusphere-egu22-4954, 2022.

The spatial distribution of mineral phases in a thin section provides information about the mineral reactions and deformation history of the sample. This information is often difficult to obtain using classical optical microscopy or SEM analyses, as the spatial resolution is too small to provide the necessary overview. SEM Automated Mineralogy (AM) delivers false colour mineral phase maps at the full thin section scale. Combined with full-sized PPL and XPL thin section scans, this provides an exceptional high-resolution overview of the mineral content and microstructures. Moreover, SEM-AM provides quantitative information about the mineral and bulk rock compositions, which can subsequently be used in thermodynamic modelling to establish P-T conditions for the entire, or a subset of, the rock sample.

The structural geology group at Utrecht University recently acquired a SEM-EDS system with Automated Mineralogy capabilities. The accuracy of the EDS system was compared against WDS microprobe measurements, while the SEM-AM based bulk rock composition of the thin section was compared against XRF data from the corresponding sample dummy. Subsequently, the SEM-AM bulk rock composition was used as input for thermodynamic modelling using Perple_X. Independent temperature estimates were established using; i) SEM-EBSD based CPO results on quartz, in conjunction with the quartz recrystallization mechanisms and recrystallized grain size; and ii) titanium-in-quartz using nano-SIMS analyses. Further constraints on fluid-rock-melt interactions were obtained by using LA-ICP-MS.

This workflow is applied to samples from the Cap de Creus region in northeast Spain. Located in the axial zone of the Pyrenees, the pre-Cambrian metasediments underwent HT-LP greenschist- to amphibolite-facies metamorphism, are intruded by pegmatite bodies, and overprinted by greenschist-facies shear zones. The SEM-AM workflow allowed to further constrain the prograde and retrograde P-T conditions in the different metamorphic zones. In addition, at the thin section scale, the results show temporal and spatial variations in the mineral reactions that occurred.  

In the near future, this workflow will be refined and included in the broader correlative microscopy workflow that will be applied in the H2020-funded EXCITE project (https://excite-network.eu/), a European collaboration of electron and x-ray microscopy facilities and researchers aimed at structural and chemical imaging of earth materials. The data will be made available in a FAIR manner through the EPOS (European Plate Observing System) data publication chain (https://epos-msl.uu.nl/).

How to cite: Wessels, R., Kok, T., van Melick, H., and Drury, M.: Constraining P-T conditions using a SEM Automated Mineralogy based workflow – an example from Cap de Creus, NE Spain, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6179, https://doi.org/10.5194/egusphere-egu22-6179, 2022.

Identification of unknown micro- and nano-sized mineral phases is commonly achieved by analysing chemical maps generated from hyperspectral datasets, particularly scanning electron microscope - energy dispersive X-ray spectroscopy (SEM-EDX). However, the accuracy and reliability are limited by subjective human interpretation and instrumental artefacts in the chemical maps. At the same time, machine learning has emerged as a powerful method to overcome the roadblocks. Here, we propose a self-supervised machine learning approach to not only identify unknown phases but also unmix the overlapped chemical signals of individual phases with no need for user expertise in mineralogy. This approach leverages the guidance of gaussian mixture modelling (GMM) clustering fitted on an informative latent space of pixel-wise elemental data points modelled using a neural network autoencoder, and deconvolutes the overlapped chemical signals of phases using non-negative matrix factorisation (NMF). We evaluate the reliability and the accuracy of the new approach using two hyperspectral EDX datasets. The first dataset was measured from an intentionally fabricated sample, where seven known mineral particles are physically overlapping with each other as well as the substrate. Without any prior knowledge, the proposed approach successfully identified all major phases and recovered the original chemical spectra of the individual phases with high accuracy. In the second case, the dataset was collected from a potential vehicular source of particulate matter air pollution, where identification of the individual pollution particles is complicated by the complex nature of the sample. The approach once again was able to identify the potential Fe-bearing ultrafine particles and isolate the background-subtracted elemental signal. We demonstrate a robust approach that potentially brings a significant improvement of mineralogical and chemical analysis in a fully automated manner. In addition, the proposed analysis process has been built into a user-friendly Python code with graphical user interface (GUI) for ease of use by general users.

How to cite: Tung, P.-Y., Sheikh, H., Ball, M., Nabiei, F., and Harrison, R.: Self-supervised Automated Mineralogical and Chemical Analysis for Hyperspectral Datasets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6787, https://doi.org/10.5194/egusphere-egu22-6787, 2022.

The determination of the electronic structure of iron-bearing compounds at high pressure and high temperature (HPHT) conditions is of crucial importance for the understanding of the Earth’s interior and planetary matter. Information on their electronic structure can be obtained by X-ray emission spectroscopy (XES) measurements, where the iron’s Kβ_1,3 emission provides information about the spin state and the valence-to-core region focusses on the coordination chemistry around the iron and its electronic state. Furthermore, resonant XES (RXES) at the iron’s K-edge reveals even more detailed information about the electronic structure [1].

We present a setup to investigate the electronic structure of iron-bearing compounds in situ at HPHT conditions using XES and RXES. The HPHT conditions are accomplished by diamond anvil cells (DACs) in combination with a portable double-sided Yb:YAG-laser heating setup [2]. The spectroscopy setup contains a wavelength dispersive von Hamos spectrometer in combination with a Pilatus 100K area detector [3]. This setup provides a full Kβ_1,3 emission spectrum including valence-to-core emission in a single shot fashion. In combination with a dedicated sample preparation and use of highly intense synchrotron radiation of beamline P01 at PETRA III, the duration of the measurements is shortened to an extend that in situ XES, including valence-to-core, as well as in situ spin state imaging becomes feasible. The use of miniature diamonds [4] enables RXES measurements at the Fe-K edge. By using different analyzer crystals for the von Hamos spectrometer, simultaneous Kα and Kβ detection are feasible, which provides L-edge and M-edge like information.

The presented sample is siderite (FeCO₃), which is in focus of recent research as it is a candidate for the carbon storage in the deep Earth. Siderite exhibits a complex chemistry at pressures above 50 GPa and temperatures above 1400 K resulting in the formation of carbonates featuring tetrahedrally coordinated CO₄-groups instead of the typical triangular-planar CO₃-coordination. These carbonates are well understood on a structural level but information on their electronic structure is scarce [5-7]. We present information on the sample’s spin state at in situ conditions of about 75 GPa and 2000 K XES Kβ_1,3 imaging  as well as RXES measurements for low and high pressure siderite at ambient temperature conditions for Kα and Kβ emission.

[1] M. L. Baker et al., Coordination Chemistry Reviews 345, 182 (2017)

[2] G. Spiekermann et al.,  Journal of Synchroton Radiation, 27, 414 (2020)

[3] C. Weis et al., Journal of Analytical Atomic Spectroscopy 34, 384 (2019)

[4] S. Petitgirard et al., J. Synchrotron Rad. , 24, 276 (2017)

[5] J. Liu et al., Scientific Reports, 5, 7640 (2015)

[6] M. Merlini et al., American Mineralogist, 100, 2001, (2015)

[7] V. Cerantola et al., Nature Communications 8, 15960 (2017)

How to cite: Albers, C., Sakrowski, R., Spiekermann, G., Libon, L., Wilke, M., Thiering, N., Gretarsson, H., Sundermann, M., Kaa, J., Tolan, M., and Sternemann, C.: Setup to study the electronic structure of iron-bearing compounds in situ at conditions of the Earth’s lower mantle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7132, https://doi.org/10.5194/egusphere-egu22-7132, 2022.

Next generation, high-resolution datasets to assess the dynamics of geological systems are becoming increasingly important to answer scientific questions that require higher spatial and temporal resolution than the current state-of-the-art. Such questions involve the couplings and feedbacks between tectonic, climatic, and surficial processes that constitute a heavily debated topic in Earth-Systems research. Over the last decades, the insufficient temporal resolution of conventionally derived (U-Th)/He thermochronometric datasets has limited the necessary quantification to track recent changes in erosion rates and relief—two metrics essential to reconstruct the past dynamics of landscapes and evaluate the relative contribution of surface and tectonic processes on erosion.

To overcome this limitation, the ERC-funded COOLER project aims to further the development of high-resolution, ultra-low temperature thermochronology by setting up a world-leading ⁴He/³He laboratory at the University of Potsdam. The centerpiece of the newly established laboratory is a split-flight-tube multi-collector gas-source sector mass spectrometer from Thermo Scientific™ connected to a sample-gas preparation bench, which includes He gas purification equipment along with a diode laser for stepped-heat sample degassing. Important topics of research the instrument will be utilized for include 1) investigation of the glacial imprint on topography, 2) characterization of the couplings between tectonic activity and topographic relief development in response to glaciation, and 3) quantification of glacial erosion relative to fluvial erosion in mountain belts. In addition to serving researchers and students at the University of Potsdam and collaborating institutions, the facility will provide analytical, research, and educational opportunities within the frame of the COOLER project to researchers from across the globe through external workshops.

To illustrate the capabilities of the new laboratory, we present our analytical and experimental methodologies used to obtain reliable high-resolution ⁴He/³He datasets. We focus on accuracy and cross-calibration to ensure minimal analytical bias in our measurements. Growing efforts in the (geo)science community are aimed at establishing best standardization practices and ensuring consistencies between laboratories and/or communities. Accordingly, we focus on ensuring that our methodologies are leading toward a noble-gas standardized method to compare mass spectrometry capabilities over various laboratories, and analytical techniques among the noble-gas communities. Accordingly, our standardized approach, coupled with analytical automation will lead to significant improvement in the accessibility and efficiency of routine ⁴He/³He analyses for geologic applications.

How to cite: Amalberti, J., van der Beek, P., Colleps, C., and Bermard, M.: New high-resolution 4He/3He laboratory at the University of Potsdam: Toward standardized approaches for efficient and reliable routine 4He/3He analyses for thermochronology applications., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7412, https://doi.org/10.5194/egusphere-egu22-7412, 2022.

Volatile organic sulfur compounds (VOSC) are known to occur in natural gas and petroleum reservoirs. These compounds are typically accompanied by H₂S which together, degrade the quality of the petroleum, complicate production due to corrosion of piping, and pose a health risk to workers and local communities. The origins of both H₂S and VOSC in natural gas are only partially understood with the latter being analyzed in only a few cases and its formation processes virtually unknown. Nevertheless, several studies have linked VOSC to H₂S in processes such as thermochemical sulfate reduction (TSR) and kerogen cracking. Hence, VOSC have the potential to act as a proxy for the natural gas and H₂S origins, in-situ TSR and fluid migration pathways.

To better understand the pathways of VOSC formation in natural gas reservoirs, we analyzed natural gas samples (Permian reservoirs, Sichuan Basin, China) and performed a series of pyrolysis experiments. The results of the experiments between methane (CH₄) and H₂S at 360°C for 4-96 hours revealed the only VOSC formed is methanethiol (MeSH) which was identified at ppm concentrations in all experiments. The δ³⁴S values of the MeSH were 2 to 3‰ heavier than the initial H₂S. For comparison, Meshoulam et al., (2021) reported that the reaction between H₂S and pentane (i.e. “wet gas”) that yielded a variety of VOSCs from thiols to methyl-thiophenes in the gas phase and up to methyl-benzothiophenes in the liquid phase. The analysis of natural gases showed that the samples contain a large variety of thiols and sulfides. The diversity of VOSC identified carries some resemblance to that observed by Meshoulam et al., (2021) and may suggest these VOSC are the result of in-reservoir reaction of C₂+ hydrocarbons with H₂S. The analysis of δ³⁴S values of the VOSCs showed they cover a range between +10 to +30‰ while most samples had their VOSC in a narrower range of approximately 8‰. Generally, samples show a positive correlation between H₂S content and VOSCs concentration- thereby implying VOSCs formation in the gas-phase. The δ³⁴S of thiols in five of the samples covered a narrower isotopic range of about 2‰ while the sulfides in the samples spread over a large isotopic range of up to 10‰. This observation suggests the thiols are in isotopic equilibrium with their associated H₂S while the sulfides are not. The reason for this difference is unclear. Further analysis will shed more light on isotopic fractionations between VOSC and H₂S and will thus allow identification of H₂S origins in the studied area.

[1] Meshoulam, A., Said-Ahmad, W., Turich, C., Luu, N., Jacksier, T., Shurki, A., Amrani, A., 2021. Experimental and theoretical study on the formation of volatile sulfur compounds under gas reservoir conditions. Organic Geochemistry, 152, 104175

How to cite: Kutuzov, I., Cai, C., and Amrani, A.: The origins of volatile organic sulfur compounds in natural gas reservoirs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9146, https://doi.org/10.5194/egusphere-egu22-9146, 2022.

The isotope composition of rainfall provides information on the initial isotope composition of the moisture source, conditions during evaporation and condensation of water vapor, and the rain-out history of an air-parcel. A standard method to analyze the rainfall isotope composition is by using Cavity Ring Down Spectrometry (CRDS). The accuracy of the analysis highly depends on the water isotope standards used, which determines the degree to which absolute values from different labs can be compared. The amount of international water isotope standards like VSMOW2 and SLAP2 primary water standards is extremely limited; therefore the International Atomic Energy Agency recommends calibrating in-house water isotope standards once a year by using VSMOW2 and SLAP2. The isotope range between VSMOW2 and SLAP2 is extreme, with 55.5‰ for d¹⁸O and 427.5‰ for d²H. The isotope range used in a sequence poses a problem for CRDS techniques that are characterized by significant memory effects.

In this study, we compare the behaviors of two different CRDS systems: a Picarro L2140i and a LGR WIA 35EP. We evaluate the relation between isotope differences of subsequent samples and the memory effect. We show that after 100 injections, memory effects may still be visible in hydrogen. Even when the isotope composition of subsequent injections of the same standard or sample does not show a trend anymore, the raw isotope data seems biased towards the isotope composition of multiple different samples or standards run prior. Running long sequences of for example 1100 injections in high precision ¹⁷O mode, also requires several vaporizer septa changes. The timing of a septa change is important, because opening the vaporizer allows water vapor from the atmosphere to enter the otherwise closed system, from which it takes approx. 20 injections to recover to the prior absolute values. Here we aim to provide a more practicle approach to a calibration sequence architecture and number of injections per primary and in-house standards, taking into account the potential drift of the analyzers.

How to cite: Wassenburg, J. A. and Sinha, N.: Improving calibrations of in-house water isotope standards using CRDS and OA-CRDS: memory effects versus drift, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11603, https://doi.org/10.5194/egusphere-egu22-11603, 2022.

High pressure and high temperature experiments performed with laser-heated diamond anvil cells (LH-DAC) are being extensively used in geosciences in order to study matter at conditions prevailing in planetary interiors. Due to the size of the apparatus itself, the samples that are produced are extremely small, on the order of few tens of micrometers. There are several ways to analyze the samples and extract physical, chemical or structural information, using either in situ or ex situ methods. Here, we will compare two nanoprobe techniques, namely nano X-ray fluorescence (nano-XRF) and Nanoscale secondary ion mass spectrometry (NanoSIMS), that can be used to analyze samples synthetized in LH-DAC and recovered using Focused Ion Beam. The two techniques are very different in various aspects, the most important one being that nano-XRF is a deeply penetrative but nondestructive method, whereas NanoSIMS is a surface sensitive and destructive method. The second major difference between the two techniques is that NanoSIMS can probe isotopes, whereas nano-XRF cannot. With both, it is possible to obtain the spatial distribution of chemical elements in the samples.

We used these two nanoprobes to retrieve elemental concentrations and ratios of dilute moderately and highly siderophile elements (few tens of ppm) in quenched experimental melts relevant for the formation of the core of the Earth. We will show those results and discuss the importance of proper calibration for the acquisition of quantifiable results. We have also performed metal–silicate partitioning experiments in which tungsten and molybdenum were incorporated. Those experiments are especially relevant to understand the core–mantle differentiation of the Earth, about 4.5 billion years ago. We will first present and compare metal–silicate partition coefficient obtained by both nano-XRF and NanoSIMS, and second also with results obtained independently by electron microprobe.

How to cite: Blanchard, I., Petitgirard, S., Laurenz, V., Miyajima, N., Wilke, M., Rubie, D., Lobanov, S. S., Hennet, L., Morgenroth, W., Tucoulou, R., Bonino, V., Zhao, X., and Franchi, I.: Chemical Analysis of Trace Elements at the Nanoscale in Samples Recovered from Laser-Heated Diamond Anvil Cell Experiments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13173, https://doi.org/10.5194/egusphere-egu22-13173, 2022.

The European infrastructure In-service Aircraft for a Global Observing System (IAGOS) (www.IAOGS.org) has implemented an automatic workflow for data management organizing the dataflow starting at the sensor towards the central data-portal located in Toulouse. The workflow is realized and documented using the web-based Django framework with a model-based approach using Python.

This workflow performs all necessary data processing and QA/QC tests to automated upload NRT processed data and serves the PI as basis for approval decisions. This includes repeated cycles for different stages of data maturity. The PI can monitor the status of all tasks by web-based reports produced by the Task Manager.  An automated reprocessing is possible by storing metadata on all steps as well as decisions of the PI. The implementation of the workflow is one big step to make IAGOS data handling compliant with the FAIR principles (findable, accessible, interoperable, reusable).

The workflow is easy adaptable to manage the workflow of other Infrastructures or research institutes. Thus, we will open the development under MIT license and invite other datacenters to contribute to the development.

Acknowledgments:

This work was supported by European Union's Horizon 2020 research and innovation programme under grant agreement No 824068 and by Helmholtz STSM Grant “DIGITAL EARTH”

How to cite: Bundke, U., Kennert, M., Mahnke, C., Rohs, S., and Petzold, A.: Implementation of a FAIR Compliant Automated Workflow for Infrastructures, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6332, https://doi.org/10.5194/egusphere-egu22-6332, 2022.

Urban territories collect many types of geochemical and physico-chemical data relative to, e.g., soil quality or soil functions. Such data may serve for various purposes like verifying the compatibility with current or future uses, defining (pedo)geochemical backgrounds, establishing levels of exposure to soil pollutants, identifying management options for polluted sites or for excavated soils, verifying the evolution of infiltration ponds, assessing carbon storage, etc. They may also serve to prioritize soil functions and associated ecosystem services such as, e.g., soil fertility, surface and groundwater storage or supply, purification of infiltrated rainwater, etc. Gathering such data in national databases and making them available to stakeholders raises many issues that are technical, legal and social.  Should all of the data be made available or only selected portions? How can access and reuse of the data be ensured in a legal fashion? Are statistical and geostatistical methods able to deal with data from heterogeneous origins, allowing their reuse for other purposes than the initial one? In this context, it is necessary to take into account scientific as well as practical considerations and to collect the societal needs of end-users like urban planners.

To illustrate the complexity of these issues and ways to address them, we propose to share the French experience:

• on gathering urban soil geochemical data in the French national database BDSolU. We will present how this database was created, the choices made in relation with the national context, the difficulties encountered, and the questions that are still open.
• on a new interrogation system linking agricultural and urban soil databases (DoneSol and BDSolU), which have different requirements, and the corresponding standards. Such linkage based on interoperability is important in the context of changes of soil use, with for example agricultural soils becoming urbanised soils, or soils from brownfields intended for gardening. It is also necessary to ensure a territorial continuity for users.

The objective is to define a robust and standardised methodology for database conceptualisation, sharing and final use by stakeholders including scientists

How to cite: Le Guern, C., Brunet, J.-F., Négrel, P., Lemal, S., Taffoureau, E., Grellet, S., Beaufils, M., Lattelais, C., Le Bas, C., and Roussel, H.: French feedback from urban soil geochemical data archive to data sharing: state of mind and intent, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7228, https://doi.org/10.5194/egusphere-egu22-7228, 2022.

Automatic Weather Stations (AWS) deployed in the context of research projects provide very valuable data thanks to the flexibility they offer in term of measured meteorological parameters, choice of sensors and quick deployment and redeployment. However this flexibility is a challenge in terms of metadata and data management. Traditional approaches based on networks of standard stations can not accommodate these needs and often no tools are available to manage these research AWS, leading to wasted data periods because of difficult data reuse, low reactivity in identifying potential measurement problems, and lack of metadata to document what happened.

The Data Access Made Easy (DAME) effort is our answer to these challenges. At its core, it relies on the mature and flexible open source MeteoIO meteorological pre-processing library. It was originally developed as a flexible data processing engine for the needs of numerical models consuming meteorological data and further developed as a data standardization engine for the Global Cryosphere Watch (GCW) of the World Meteorological Organization (WMO). For each AWS, a single configuration file describes how to read and parse the data, defines a mapping between the available fields and a set of standardized names and provides relevant Attribute Conventions Dataset Discovery (ACDD) metadata fields, if necessary on a per input file basis. Low level data editing is also available, such as excluding a given sensor, swapping sensors or merging data from another AWS, for any given time period. Moreover an arbitrary number of filters can be applied on each meteorological parameter, restricted to specific time periods if required. This allows to describe the whole history of an AWS within a single configuration file and to deliver a single, consistent, standardized output file possibly spanning many years, many input data files and many changes both in format and available sensors. Finally, all configuration files are kept in a git repository in order to document their history.

A basic email-based interface has been developed that allows to create new configuration files, modify an existing configuration file or request data on-demand for any time period. Every hour, the data for all available configuration files is regenerated for the last 13 months and stored on a shared drive so all are able to access the current data without even having to submit a request. A table is generated showing all warnings or errors produced during the data generation along with some metadata such as the data owner email in order for the data owner to quickly spot troublesome AWS.

How to cite: Bavay, M., Fierz, C., and Nitu, R.: Data Access Made Easy: flexible, on the fly data standardization and processing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8262, https://doi.org/10.5194/egusphere-egu22-8262, 2022.

The TRR170-DB data repository (https://planetary-data-portal.org/) is a Re3data (r3data.org) referenced repository that manages new machine-readable data and resources from the collaborative research center ‘Late Accretion onto Terrestrial Planets’ (TRR 170) and from other institutions in in the planetary science community. Data in the repository reflect the diverse methods and approaches applied in the planetary sciences, including astromaterials data, experimental studies, remote sensing data, images and geophysical modeling data. The TRR170-DB repository follows a data policy and practice that supports Open Science and the FAIR principles (Wilkinson et al., 2016) as promoted by the German National Research Data Infrastructure (www.nfdi.de) and various national and international funding agencies and initiatives. The TRR170-DB framework supports users to align their data storage with the data life cycle of data sharing, persistent data citation, and data publishing. The permanent host of the TRR170-DB is Freie Universität Berlin. This long-term preservation and access of TRR170-DB’s published data ensures them being reused by researchers and the interested public.

The TRR170-DB repository is operated on the open source data management software Dataverse (dataverse.org). A web portal provides access to the storage environment of the datasets. The web portal guides users through the process of data storage and publication. It also informs about legal conditions and embargo periods to safeguard the data publication process. Additional information is available informing the user about data management and data publication related news and training events.

A user can search metadata information to find specific published data collections and files without logging in to TRR170-DB. A recently integrated new tool, the data explorer, assists the user in advanced searches to browse and find published data content. Data suppliers receive data curation services, a permanent archive and a digital object identifier (DOI) to make the dataset unique and findable. We encourage TRR 170 members and other users to store replication datasets by implementing publishing workflows to link publications to data. These replication datasets are freely available, and no permission is required for reuse and verification of a study. TRR170-DB has a flexible data-driven metadata system that uses tailored metadata blocks for specific data communities. Once a dataset has been published, its metadata and files can be exported in various open metadata standards and file formats. This ensures that all data published in the repository are generally accessible for other external databases and repositories (“interoperability”).

We are currently expanding metadata templates to improve interoperability, findability, preservation, and reuse of geochemical data in TRR170-DB. New geochemical metadata templates will incorporate additional standardized information on samples and materials, analytical methods and additional experimental data.  Advancing metadata templates will be an ongoing process in which the international scientific community and various initiatives (OneGeochemistry, Astromaterials Data System, etc.) need to interact and discuss what is required.

How to cite: Lehmann, E. and Becker, H.: The TRR170-DB Data Repository: The Life Cycle of FAIR Planetary Data from Archive to Publication, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9960, https://doi.org/10.5194/egusphere-egu22-9960, 2022.

As volumes of geoanalytical data grow, research in geochemistry, volcanology, petrology, and other disciplines working with geoanalytical data is evolving to data-driven and computational approaches that have enormous potential to lead to new scientific discoveries. Application of advanced methods for data mining and analysis including Machine Learning, and Artificial Intelligence, as well as the generation of models for simulating natural processes all require seamless machine-readable access to large interoperable stores of consistently structured and documented geochemical data. Standard protocols, formats, and vocabularies are also critical in order to process, manage, and publish these growing data volumes efficiently with seamless workflows that are supported by interoperable tools.

Today, easy integration of data into Analysis Ready Data stores and the successful and efficient application of new research methodologies to these data stores is hindered by the fragmentation of the international geochemical data landscape that lacks the technical and semantic standards for interoperability; organizational structures to guide and govern these standards; and a scientific culture that supports and prioritizes a global sustainable data infrastructure. In order to harness the scientific treasures hidden in BIG volumes of geochemical data, the science community, geochemistry data providers, publishers, funders, and other stakeholders need to come together to develop, implement, and maintain standards and best practices for geochemical data, and commit to changing the current data culture in geochemistry. The benefits will be wide-ranging and increase the relevance of the discipline. 

Although many research data initiatives today focus on the implementation of the FAIR principles for Findable, Accessible, Interoperable, and Reusable data, most data is only human-readable, even though the original purpose of the FAIR principles has been to make data machine-actionable. The development of standards today should not focus on spreadsheet templates used to format and compile project-centric databases that are hard to re-purpose. These methods are not scalable. The focus should be on global solutions where any digital data are born connected to agreed machine readable standards so that researchers can utilize the latest AI and ML techniques.

Global standards for geochemical data should not be perceived as ‘one ring to rule them all’, but rather as a series of interoperable ‘rings’ of data, which like the Olympic rings will integrate data from the all continents and nations.

How to cite: Lehnert, K. and Wyborn, L.: Global Data Standards for Geochemistry: Not the ‘One Ring to Rule Them All’, but a set of ‘Olympic Rings’ that Link and Integrate across Continents, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10726, https://doi.org/10.5194/egusphere-egu22-10726, 2022.

Some disciplines, especially those that look at the Earth system, work with large to very large amounts of data. Storing this data, but also processing it, places completely new demands on scientific work itself.

Let's take the example of climate research and specifically climate modelling. In addition to long-term meteorological measurements in the recent past, results from climate models form the main basis for research and statements on past and possible future global, regional and local climate. Climate models are very complex numerical models that require high-performance computing. However, with the current and future increasing spatial and temporal resolution of the models, the demand for computing resources and storage space is also increasing. Previous working methods and processes no longer hold up and need to be rethought.

Taking the German Climate Computing Centre (DKRZ) as an example, we analysed the users, their goals and working methods. DKRZ provides the climate science community with resources such as high-performance computing (HPC), data storage and specialised services and hosts the World Data Center for Climate (WDCC). In analysing users, we distinguish between two groups: those who need the HPC system to run resource-intensive simulations and then analyse them, and those who reuse, build on and analyse existing data. Each group subdivides into subgroups. We have analysed the workflows for each identified user and found identical parts in an abstracted form and derived Canonical Workflow Modules.

In the process, we critically examined the possible use of so-called FAIR Digital Objects (FDOs) and checked to what extent the derived workflows and workflow modules are actually future-proof.

The vision is that the global integrated data space is formed by standardised, independent and persistent entities that contain all information about diverse data objects (data, documents, metadata, software, etc.) so that human and, above all, machine agents can find, access, interpret and reuse (FAIR) them in an efficient and cost-saving way. At the same time, these units become independent of technologies and heterogeneous organisation of data, and will contain a built-in mechanism that supports data sovereignty. This will make the handling of data sustainable and secure.

So, each step in a research workflow can be a FDO. In this case, the research is fully reproducible, but parts can also be exchanged and, e.g. experiments can be varied transparently. FDOs can easily be linked to others. The redundancy of data is minimised and thus also the susceptibility to errors is reduced. FDOs open up the possibility of combining data, software or whole parts of workflows in a new and simple but at all times comprehensible way. FDOs will make an important contribution to the reproducibility of research results, but they are also crucial for saving storage space. There are already data that are FDOs, but also self-contained frameworks that store data via tracking workflows. Similar to the TCP/IP standard, DO interface protocols are already developed. However, there are still some open points that are currently being worked on and defined with regard to FDOs in order to make them a globally functioning system.

How to cite: Anders, I., Peters-von Gehlen, K., Thiemann, H., Bergemann, M., Buurman, M., Fast, A., Kadow, C., Kulüke, M., and Wachsmann, F.: Data amounts and reproducibility: How FAIR Digital Objects can revolutionise Research Workflows, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11103, https://doi.org/10.5194/egusphere-egu22-11103, 2022.

Geochemical data are fundamental to understanding many planetary and environmental processes – yet in the absence of a community-endorsed data culture that adheres to common data standards, the geochemical data landscape is highly fragmented. The GEOROC and PetDB databases are leading, open-access resources for geochemical and isotopic rock and mineral data that have collaborated for nearly 25 years to provide researchers with access to large volumes of curated and harmonized data collections. PetDB is a global synthesis of published chemical, isotopic and mineralogical data for rocks, minerals and melt inclusions with a focus on data for igneous and metamorphic rocks from the ocean floor, ophiolites, xenolith samples from the Earth's mantle and lower crust and tephra, operated by the EarthChem data facility. Its counterpart, GEOROC hosts a collection of published analyses of volcanic and plutonic rocks, minerals and mantle xenoliths, predominantly derived from ocean islands and continental settings. These curated, domain-specific databases are increasingly valuable to data-driven and interdisciplinary research and form the basis of hundreds of new research articles each year across numerous earth data disciplines. 

Over the last two decades, both GEOROC and EarthChem have invested great efforts into operating data infrastructures for findable, accessible, interoperable and reusable data, while working together to develop and maintain the EarthChem Portal (ECP) as a global open data service to the geochemical, petrological, mineralogical and related communities. The ECP provides a single point of access to >30 million analytical values for >1 million samples, aggregated from independently operated databases (PetDB, NAVDAT, GEOROC, USGS, MetPetDB, DARWIN). Yet one crucial element of FAIR data is still largely missing: interoperability across different data systems, that allows data in separately curated databases, such as GEOROC and PetDB, to be integrated into comprehensive, global geochemical datasets.

Both EarthChem and GEOROC have recently embarked on major new developments and upgrades to their systems to improve the interoperability of their data systems. The new Digital Geochemical Data Infrastructure (DIGIS) initiative for GEOROC 2.0 aims to develop a connected platform to meet future challenges of digital data-based research and provide advanced services to the community. EarthChem has been developing an API-driven architecture to align with growing demands for machine-readable, Analysis Ready Data (ARD). This has presented an opportunity to make the two data infrastructures more interoperable and complementary. EarthChem and DIGIS have committed to cooperation on system architecture design, data models, data curation, methodologies, best practices and standards for geochemistry. This cooperation will include: (a) joint research projects; (b) optimized coordination and alignment of technologies, procedures and community engagement; and (c) exchange of personnel, data, technology and information. The EarthChem-DIGIS collaboration integrates with the international OneGeochemistry initiative to create a global geochemical data network that facilitates and promotes discovery and access of geochemical data through coordination and collaboration among international geochemical data providers, in close dialogue with the scientific community and with journal publishers.

How to cite: Klöcking, M., Lehnert, K., Profeta, L., Sarbas, B., Brase, J., Cao, S., Figueroa, J. D., Horstmann, W., Ji, P., Johansson, A., Kallas, L., Möller-McNett, S., Mukhumova, M., Nieschulze, J., Sturm, A., Sweets, H., Willbold, M., and Wörner, G.: GEOROC and EarthChem: Optimizing Data Services for Geochemistry through Collaboration, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11348, https://doi.org/10.5194/egusphere-egu22-11348, 2022.

CaosDB is a flexible semantic research data management system, released as open source software. Its versatile data model and data integration toolkit allows for applications in complex and very heterogeneous scientific workflows and different scientific domains. Successful implementations include biomedical physics [1] and glaciology [2]. Here, we present a recent implementation of a use case in marine biogeochemistry which has a special focus on bridging between experimental work and numerical ocean modelling. CaosDB is used to store, index and link data during different stages of research on the marine carbon cycle: Data from experiments and field campaigns is integrated and mapped onto semantic data structures. This data is then linked to data from numerical ocean simulations. The ocean model, here with a specific focus on natural marine carbon sequestration of dissolved organic carbon (DOC), uses the georeferenced data to evaluate model performance. By simultaneously linking empirical data and the sampled model parameter space together with the model output, CaosDB enhances the efficiency of model development. In the current implementation simulated data is linked to georeferenced DOC concentration data. We plan to expand it to complex data sets including thousands of dissolved organic matter molecular formulae and metagenomes of pelagic microbial communities. The combined management of these heterogeneous data structures with semantic models allows us to perform complex searches and seamlessly connect to automated data analysis pipelines.


[1] Fitschen, T.; Schlemmer, A.; Hornung, D.; tom Wörden, H.; Parlitz, U.; Luther, S. CaosDB—Research Data Management for Complex, Changing, and Automated Research Workflows. Data 2019, 4, 83. https://doi.org/10.3390/data4020083
[2] Schlemmer, A.; tom Wörden, H.; Freitag, J.; Fitschen, T.; Kerch, J.; Schlomann, Y.; ... & Luther, S. Evaluation of the semantic research data management system CaosDB in glaciology. deRSE 2019. https://doi.org/10.5446/42478

How to cite: Schlemmer, A., Merder, J., Dittmar, T., Feudel, U., Blasius, B., Luther, S., Parlitz, U., Freund, J., and Lennartz, S. T.: Implementing semantic data management for bridging empirical and simulative approaches in marine biogeochemistry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11766, https://doi.org/10.5194/egusphere-egu22-11766, 2022.

In this abstract we introduce a suite of free applications to produce FAIR consistent, clean and easily available geoscience data for research and industry alike. 

Creation of data starts with sample collection in the field and the assigning of an unique global IGSN sample identifier to samples, these samples are stored along with any subsequent  analytical data in our fine-grained and detailed geochemical data models allowing visualising and publishing acquired datasets. This unique solution has been developed by Lithodat Pty Ltd in conjunction with the AuScope Geochemical Network (AGN), Australian geochemical laboratories and can be accessed by the public on the AusGeochem web platform. 

Using our fully integrated field application users can enter and store all sample details on-the-fly during field collection, the data will be stored in the user's private data collection. Once the researchers return from the field they can log into their account on the browser-based AusGeochem platform and view or edit all collected samples. After running subsequent geochemical analyses on the sample those results, including all metadata, can be stored in the database and attached to the sample. Once uploaded, data can be visualised within AusGeochem, using simple data analytics via technique-specific dashboards and graphs. The data can be shared with collaborators, downloaded in multiple formats and made public enabling FAIR data for the research community. 

Here we show a complete sample workflow example, from collection in the field to the final result as a thermochronology study. Sample analysis using fission track and (U-Th)/He and all associated data will be uploaded and stored in the AusGeochem platform. Once all analyses are complete, the data will be shared with collaborators and made available to the public. An important step during this process is by having an integrated IGSN minting option which will give the sample a unique global sample identifier, making the sample globally discoverable. 

Having all data stored in a clean and curated relational database with very detailed and fine-grained data models gives researchers free access to large amounts of structured and normalised data, helping them develop new technologies using machine learning and automated data integration in numerical models. Having all data in one place including all metadata such as ORCIDs from involved researchers, funding sources, grant numbers and laboratories enables the quantification and quality assessment of research projects over time.

How to cite: Theile, M., Noble, W., Beucher, R., McMillan, M., Boone, S., and Kohlmann, F.: From Field Application to Publication: An end-to-end Solution for FAIR Geoscience Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11980, https://doi.org/10.5194/egusphere-egu22-11980, 2022.

The European Multidisciplinary Seafloor and water-column Observatory (EMSO) European Research Infrastructure Consortium (ERIC) is a large-scale European Strategy Forum on Research Infrastructure (ESFRI) member with strategically placed sea observatories with the essential scientific objective of real-time, long-term monitoring of environmental processes related to the interaction between the geosphere, biosphere, and hydrosphere. EMSO ERIC collects, curates, and provides high-quality oceanographic measurements from surface to deep seafloor to assess long-term time series and oceanographic modeling. In addition, EMSO ERIC has developed a set of data services that harmonize its regional facilities’ data workflows, enhancing efficiency and productivity, supporting innovation, and enabling data- and knowledge-based discovery and decision-making. These services are developed in connection with the ESFRI cluster of Environmental Research Infrastructures (ENVRI) through the adoption of FAIR data principles (findability, accessibility, interoperability, and reusability) and supported by the ENVRI-FAIR H2020 project. 

EMSO ERIC’s efforts in adopting FAIR principles include the use of globally unique and resolvable persistent identifiers (PIDs) in alignment with the ENVRI-FAIR task forces. We present a service for the identification and long-lasting citability of dynamic data queries on harmonized data sets generated by EMSO ERIC users. The service is aligned with the Research Data Alliance (RDA) working group on data citation and has been integrated into the EMSO ERIC data portal. User-built queries on the data portal are served by the EMSO ERIC Application Programming Interface (API), which retrieves the user requested data and provides a Uniform Resource Identifier (URI) to the query, visualizations, and data sets in CSV and NetCDF formats. The data portal allows users to request a PID to the data query by providing mandatory and optional metadata information through an online form. The mandatory metadata consists of the description of the data and specific information about the creators, personal or organizational, including their identifiers and affiliations. The optional metadata consists of different types of titles and descriptions that the user finds compelling. The service provides a permalink to a web page maintained within the data portal with the PID reference, metadata information, and the URI to the data query. The web pages associated with PIDs also provide the option to request a Digital Object Identifier (DOI) if users are authorized via the EMSO ERIC Authorization and Authentication Infrastructure (AAI) system.

How to cite: Rodero, I., Fornós, A., Bardaji, R., Chiappini, S., and Dañobeitia, J.: Identification and Long-lasting Citability of Dynamic Data Queries on EMSO ERIC Harmonized Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12096, https://doi.org/10.5194/egusphere-egu22-12096, 2022.

The UCLA Cosmochemistry Database was initiated as a data rescue project aiming to archive a variety of cosmochemical data acquired at the University of California, Los Angeles. The database will ensure that future studies can use and reference these data in the examination, analysis and classification of new extraterrestrial samples.

The database is developed in collaboration with the Astromaterials Data System (AstroMat) that will provide persistent access to and archiving of the database. The database is a project in progress. We will continue to make additions, updates, and improvements to the database.

The database includes elemental compositions of extraterrestrial materials (including iron meteorites, chondrites, Apollo samples, and achondrites) analyzed by John T. Wasson, Paul H. Warren and their coworkers using atomic absorption spectrometry (AAS), neutron activation analysis (NAA), and electron microprobe analysis (EMPA) at UCLA over the last six decades. The team started to use INAA to analyze iron meteorites, lunar samples, and stony meteorites starting from the late 1970s [1]. Some achondrites and lunar samples were analyzed by EMPA. Some of the UCLA data have been published, but most of the data were neither digitized nor stored in a single repository.

Compositional data have been compiled by the UCLA team from publications, unpublished files, and laboratory records into datasets using Astromat spreadsheet templates. These datasets are submitted to the Astromat repository. Astromat curators review the datasets for metadata completeness and correctness, register them with DataCite to obtain a DOI and make them citeable, and package them for long-term archiving. To date, we have compiled data from 52 journal articles; each article has its own separate dataset. Data and metadata of these datasets are then incorporated into the Astromat Synthesis database.

The UCLA datasets are publicly accessible at the Astromat Repository, where individual datasets can be searched and downloaded. The UCLA cosmochemical data can also be accessed as part of the Astromat Synthesis database, where they are identified as a special ‘collection’. Users may search, filter, extract, and download customized datasets via the user interface of the Astromat Synthesis database (AstroSearch).  Users will be able to access the UCLA Cosmochemistry Database directly from the home page of AstroMat (https://www.astromat.org/).

We plan to include EMPA data of lunar samples and achondrites, and add scanned PDF files of laboratory notebooks and datasheet binders that are not commonly published in journals. These PDF files contain information on irradiation date, mass, elemental concentrations, and classification for each iron specimen, and John Wasson’s personal notes on meteorites. We will also add backscattered-electron (BSE) images, energy dispersive spectroscopy (EDS) images, and optical microscopy images.

The Astromat team is currently working to develop plotting tools for the interactive tables.

Acknowledgments: We thank John Wasson and his coworkers for collecting the cosmochemical data for the last 60 years. Astromat acknowledges funding from NASA (grant no. 80NSSC19K1102).

References: [1] Scott E.R.D et al. (1977) Meteoritics, 12, 425–436.

How to cite: Zhang, B., Warren, P. H., Rubin, A. E., Lehnert, K., Profeta, L., Johansson, A., Ji, P., Figueroa-Solazar, J. D., and Mays, J.: The UCLA Cosmochemistry Database, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13188, https://doi.org/10.5194/egusphere-egu22-13188, 2022.

When researchers collect or create physical samples they usually assign a user-generated number to each sample. Subsequently, that sample can be submitted to a laboratory for analysis of a variety of analytes. However, as geoanalytical laboratories are generating ever increasing volumes of data, most laboratories have automated workflows and it is no longer feasible for laboratories to use researcher-supplied sample numbers, particularly as it is not guaranteed that user-supplied numbers will be unique in comparison to numbers submitted by other users to the same laboratory. To address this issue new, laboratory-generated numbers may be assigned to that sample.

Moreover, as a single laboratory rarely has the capability to offer all analytical techniques, individual samples tend to move from laboratory to laboratory to acquire the desired suite of analytes.  Each laboratory may implement a different number to that sample. At the conclusion of their project, the researcher may submit the same sample to a museum or institutional repository, where the sample will be assigned yet another institution-generated number to ensure that all samples are uniquely identified in their repository. 

Ultimately, by the time the researcher submits an article to a journal and wants to identify samples in the text or tables, they may have a multitude of locally-generated numbers to choose from. Not one of the locally assigned numbers to that sample can be guaranteed to be globally unique. It is also unlikely that any of these local numbers will be persistent over the longer term (decades), or be resolvable to enable the location of the identified resource or any information about it elsewhere on the web (metadata, landing page, services related to it, etc).

Globally unique, persistent, resolvable identifiers such as the IGSN play a critical role in the unique identification of geoanalytical samples that pass between systems and organisations: they cannot be duplicated by another researcher, laboratory or sample repository. They persistently link to information about the origin of the sample; to personas in the creation of the sample (collector, institution, funder); to the laboratory data and their creation (analyst, laboratory, institution, funder, data software); and to the sample curation phase (curator, repository, funder). They connect the phases of a sample’s path from collection in the field to lab analysis to the synthesis/research phase to the publication to the archive. Globally unique sample identifiers also enable cross linkages to any artefacts derived from that sample (images, analytical data, other articles). Further, identifiers like IGSN enable sub samples or sample splits to be linked back to their parent sample, creating a holistic picture of any information derived from the initial sample. 

Hence, best practice is clearly to assign the globally unique resolvable identifier to the initial resource. Like a birth certificate, the identifier can be carried through the progressive stages of the research ‘life-cycle’ including laboratory analysis, generation of further data, images, publication, and ultimately curation and preservation. Where any subsamples are derived, they, and any data generated on them, can be linked back to the parent identifier.

How to cite: Lehnert, K., Klump, J., Ramdeen, S., Elger, K., and Wyborn, L.: The critical role of unique identification of samples for the geoanalytical data pipeline, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13317, https://doi.org/10.5194/egusphere-egu22-13317, 2022.

How to cite: DiMaggio, E., Mana, S., and VanHazinga, C.: EARThD: an effort to make East African tephra geochemical data available and accessible, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13330, https://doi.org/10.5194/egusphere-egu22-13330, 2022.

The Watershed Function Scientific Focus Area (WFSFA) is a U.S. Department of Energy research project that seeks to determine how mountainous watersheds retain and release water, carbon, nutrients, and metals. The WFSFA maintains a community field observatory at its primary field site in the East River, Colorado. The WFSFA collects diverse environmental data and has developed a “Field-Data” workflow that standardizes data management across the project, from field collection to laboratory analysis to publication. This workflow enables the WFSFA to address data quality and management challenges that environmental observatories face. 

Through this workflow, the WFSFA has increased the use of the data curated from the project by (1) providing detailed metadata with unique identifiers for samples, locations, and sensors, (2) streamlining the data sharing and publication process through early sharing of data internally within the team and publication of data on the ESS-DIVE repository following curation, and (3) adopting machine-readable and FAIR community data standards (Findability, Accessibility, Interoperability, Reusability). 

We describe an example application of this workflow for geochemical data, which utilizes a community geochemical data standard for water-soil-sediment chemistry (https://github.com/ess-dive-community/essdive-water-soil-sed-chem) developed by Environmental Systems Science Data Infrastructure for a Virtual Ecosystem (ESS-DIVE). This data standard is designed to standardize geochemical data, metadata, and file-level metadata, and was applied to WFSFA geochemical data, including ICP-MS, Isotope, Ammonia-N, Anion, DIC/NPOC/TDN datasets. This ensures important metadata is contained within the data file, such as precision of data analysis, storage and sample processing information, detailed sample names, material information, and unique identifiers associated with the samples (IGSNs). This metadata is essential to understand and reuse data products, as well as enable machine-readability for future model applications. Detailed examples of the standardized geochemical data types were created and are now being used as templates by WFSFA researchers to standardize their geochemical data. The adoption of this community geochemical data standard and more broadly the Field-Data workflow will improve the findability and reusability of WFSFA datasets. 

How to cite: O'Ryan, D., Varadharajan, C., Alper, E., Boye, K., Burrus, M., Christianson, D., Cholia, S., Crystal-Ornelas, R., Damerow, J., Dong, W., Elbashandy, H., Faybishenko, B., Hendrix, V., Johnson, D., Kakalia, Z., Versteeg, R., Williams, K., Wong, C., and Agarwal, D.: A workflow to standardize collection and management of large-scale data and metadata from environmental observatories, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13338, https://doi.org/10.5194/egusphere-egu22-13338, 2022.

Efforts towards standardizing biogeochemical data from palaeoclimate archives such as speleothems, ice cores, corals, trees or marine sediments allow to tackle global-scale changes in palaeoclimate dynamics. These endeavours are sometimes initiated for very specific research questions. One such example is the multi-archive, multi-proxy dataset used in a characterization of changes in temperature variability from the last Glacial Maximum to the current Interglacial [1]. Here, we focused on collecting all published proxy time series for temperature that fulfilled sampling criteria, but we did not include a lot of metadata.

Another, quite prominent, example is the database that grew out of the working group on Speleothem synthesis and analysis (SISAL) in the Past Global Changes (PAGES) network. In its construction, researchers from all over the world collaborated, producing a quality-controlled data product with rich metadata. SISAL v2 [2] contains data from 691 speleothem records published over the decades, for more than 500 standardized age models were established. The design and data collection in the community allowed to draw together metadata and observations to reproduce the age modeling process of individual studies. This database has a rich set of purposes, ranging from the evaluation of monsoon dynamics, to that of isotope-enabled climate models [3].

Contrasting these two approaches I will discuss the challenges arising when multiple proxies, archives, modeling purposes and community standards need to be considered. I argue that careful design of standardized data products allows for a new type of geoscience work, further catalyzed by digitization, forming a basis for tackling future-relevant palaeoclimatic and palaeoenvironmental questions at the global scale. 

[1] Rehfeld, K., et al. "Global patterns of declining temperature variability from the Last Glacial Maximum to the Holocene." Nature 554.7692: 356-359, https://doi.org/10.1038/nature25454, 2018

[2] Comas-Bru, L., et al. (incl. SISAL Working Group members): SISALv2: a comprehensive speleothem isotope database with multiple age–depth models, Earth Syst. Sci. Data, 12, 2579–2606, https://doi.org/10.5194/essd-12-2579-2020, 2020.

[3] Bühler, J. C. et al: Comparison of the oxygen isotope signatures in speleothem records and iHadCM3 model simulations for the last millennium, Clim. Past, 17, 985–1004, https://doi.org/10.5194/cp-17-985-2021, 2021.

How to cite: Rehfeld, K.: Science building on synthesis: From standardized palaeoclimate data to climate model evaluation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13382, https://doi.org/10.5194/egusphere-egu22-13382, 2022.

Over the last two years, the Australian AuScope Geochemistry Network (AGN) has developed AusGeochem in collaboration with geoscience-data-solutions company Lithodat Pty Ltd. This open, cloud-based data platform (https://ausgeochem.auscope.org.au) serves as a geo-sample registry, with IGSN minting capability, a geochemical data repository and a data analysis tool. With guidance from experts in the field of geochemistry from a number of Australian institutions, and following international standards and best practices, various sample and geochemistry data models were developed that align with the FAIR data principles. AusGeochem is currently accepting data of SIMS U-Pb as well as of fission track and (U-Th-Sm)/He techniques with LA-ICPS-MS U-Pb and Lu-Hf, ⁴⁰Ar/³⁹Ar data models under development. Special attention is paid to the implementation of streamlined workflows for AGN laboratories to facilitate ease of data upload from analytical sessions. Analytical results can then be shared with users through AusGeochem and where required can be kept fully confidential and under embargo for specified periods of time. Once the analytical data on individual samples are finalized, the data can then be made more widely accessible, and where required can be combined into specific datasets that support publications.

How to cite: Prent, A. M., Boone, S. C., Dalton, H., Gréau, Y., Florin, G., Kohlmann, F., Theile, M., Noble, W., Hodgekiss, S.-A., Ware, B., Philips, D., Kohn, B., O’Reilly, S., Gleadow, A., McInnes, B., and Rawling, T.: AusGeochem: an Australian AuScope Geochemistry Network data platform for laboratories and their users, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13429, https://doi.org/10.5194/egusphere-egu22-13429, 2022.

MetBase is the world’s largest database for meteorite compositions [1], currently hosted in Germany. MetBase started more than 20 years ago with collecting cosmochemical data by a private collector. Among others, the database consists of more than 500.000 individual data of, for instance, bulk and component chemical, isotopic and physical properties. Further, the database holds more than 90,000 references from 1492 until today. In 2006, the high value of the database was acknowledged by the Meteoritical Society with its Service Award. MetBase has seen substantial transitions in the past years from a purely commercial to a donation, free-of-charge database. The technical foundation has been completely modernised.

More recently, the Astromaterials Data System (AstroMat) has been developed as a data infrastructure to store, curate, and provide access to laboratory data acquired on samples curated in NASA’s Astromaterials Collections. AstroMat is intended to host data from past, present, and future studies. AstroMat is developed and operated by a team that has long-term experiences in the development and operation of data systems for geochemical, petrological, mineralogical, and geochronological laboratory data acquired on physical samples – EarthChem and PetDB.

Astromat and MetBase are two initiatives with two very different histories – but a shared goal. Astromat and MetBase therefore plan a common future. As a part of this, we are currently starting a project to make MetBase data fully FAIR (findable, accessible, interoperable and reusable, [2]), thereby implementing the recently established Astromat database schema [3], which is based on the EarthChem data model. Astromat and MetBase currently also work on new solutions for a long term and centralized hosting of both databases and a data input backbone.

Both MetBase and Astromat participate in the OneGeochemistry initiative, to contribute to the development of  community endorsed and governed standards for FAIR lab analytical data that will allow seamless data exchange and integration. Data access to the MetBase content will be provided both through Astromat and via a front-end that is part of the recently initiated ›National Data Infrastructure Initiative‹ (NFDI), covering all scientific areas [4].

References: [1] http://www.metbase.org. [2] Stall et al. 2019. Make scientific data FAIR. Nature 570(7759): 27-29. [3] https://www.astromat.org [4] https://www.dfg.de/en/research_funding/programmes/nfdi/index.htm [5] https://www.nfdi4earth.de

How to cite: Hezel, D. C. and Lehnert, K. A.: Closing the gap between related databases: MetBase and the Astromaterials Data System (Astromat) plan for a common future, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13457, https://doi.org/10.5194/egusphere-egu22-13457, 2022.

Harmful algal blooms (HABs) are a threat to freshwater quality, public health, and aquatic ecosystems. The economic losses suffered by the agricultural, fishing, and tourism industries as a result of HABs exceed billions of dollars worldwide annually, with cleanup costs from local and national governments reaching a similar price. Current manual field-based sampling methods followed by laboratory analysis to detect and monitor HABs in expensive, labor-intensive, and slow, delaying critical management decisions. Moreover, current detection methods have limited success documenting HABs in freshwater bodies and such attempts employ satellite-based multispectral remote sensing; however, satellite-based methods are limited by cost, low spatial and spectral resolution, and restricting temporal windows for on-demand revisits. Our study used relatively low-cost unpiloted aerial systems (UAS) and hyperspectral sensors to detect HABs with higher resolution while having the capacity to conduct near real-time detection. Additionally, our hyperspectral remote sensing can detect and differentiate between HABs that produce cyanobacteria and other chlorophyll-producing plants. We detected a spectral peak of 710 nm that is characteristic of cyanobacteria producing HABs. Principal components analysis (PCA) was useful to spatially highlight HABs over wide areas. By utilizing hyperspectral remote sensing with UAS, HABs can be monitored and detected more efficiently. This new state-of-the-art research methodology will allow for targeted assessment, monitoring, and design of HABs management plans that can be adapted for other impacted inland freshwater bodies. 

How to cite: Pirro, J., Thomas, C., Wallace, C., Alpert, Z., Tuohy, M., de Smet, T., Yokota, K., Jackson, P., Cleckner, L., Wigdahl-Perry, C., Young, K., Amejecor, K., and Scheer, A.: Utilizing Hyperspectral Remote Sensing to Detect Concentration of Cyanobacteria in Freshwater Ecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-629, https://doi.org/10.5194/egusphere-egu22-629, 2022.

The lignite mine called 'Friendship of Nations - Babina Shaft', located on the border between Poland and Germany, was closed almost 50 years ago. Despite the cessation of mining works (carried out by opencast and underground methods) and carrying out reclamation process, the negative effects of the former mineral exploitation are still observed in this region (e.g. sinkholes, local flooding, subsidence). It should be emphasized that the area of ​​the currently closed mine is also characterized by a complicated glaciotectonic structure, which is the result of successive glacial periods in the past. Both factors, i.e., the past mining activity and geological conditions, may affect the condition of soils and vegetation of the analysed area. The aim of this study was to determine, whether and to what extent the former lignite mining and the complicated glaciotectonic structure had an impact on the changes in the state of plant cover and soils, noted in the period of 1989-2019. A new index, Mining and Geology Impact Factor (MaGIF), was developed to describe the strength and the nature of the relationship between the aforementioned factors within four test fields, based on coefficients’ values and variables of six Ordinary Least Squares (OLS) models. In the research 12 independent variables, representing geological and mining conditions of the area, were prepared. The dependent variables, statistics of selected spectral indices obtained for 1989-2019, were determined in the GIS environment, within individual pixels of the research area. In this study, two vegetation indices (NDVI and NDII) and four soil indices (DSI, SMI, Ferrous Minerals and SI3), calculated on the basis of Landsat TM/ETM +/OLI images, were used. The values of the obtained MaGIF index were ​​in the range of -9.99 - 0.62, and their distribution in the test fields proved that the former mining and geological conditions had the strongest impact on the vegetation and soils of the central part of field no. 1, as well as on north-western and south-eastern parts of field no. 4. The nature of the influence of explanatory factors on the indicated components of the environment was negative (an increase or decrease in the value of the independent variable correlated with a decrease or increase in the value of a given spectral index, respectively). In the western and southern parts of field no. 1, eastern part of field no. 3, central and eastern parts of field no. 4, as well as in a major part of field no. 2, the influence of explanatory factors was the smallest. Only in fields no. 2 and 4, the small zones of positive impact of the independent variables were observed. The results indicate that the former mining and geological conditions have a significant influence on the condition of the vegetation and soils of post-mining areas. Therefore, it is extremely important to monitor the changes taking place in these regions in order to undertake appropriate preventive works and eliminate the resulting damage.

How to cite: Buczyńska, A. and Blachowski, J.: New index for assessment of environment in post-mining area – Mining and Geology Impact Factor (MaGIF), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1107, https://doi.org/10.5194/egusphere-egu22-1107, 2022.

Airborne Laser Scanning (ALS) is a widely used method in Earth science, Agriculture or Forestry. This method could provide high resolution and accurate spatial data for the better understanding of surface structures, moreover, based on the laser pulses, it can even show important features of the ground below dense vegetation. However, these ALS surveys requires specially designed aircrafts, pilots and operators, detailed flight planning, which leads to an expensive way of data analysis. The application of laser scanners for Unmanned Aerial Systems (UAS) has started in the last few years. These sensor payloads provide less weight and size and decreased accuracy compared to the traditional ALS surveys but still serve as more reliable mapping technology contrary to the photogrammetric methods in many cases. However, several new UAS laser scanners are being developed but their accuracy conditions and applicability for agricultural monitoring must be studied in many ways.

In our study we applied the novel Zenmuse L1 LiDAR sensor mounted on a DJI Matrice M300 RTK UAS. We surveyed a ~50 ha area of corn field near Berettyóújfalu, Hungary in the summer of 2021. Our aim was to reveal the applicability of UAS laser scanning for the precise ground surface reconstruction. In this period, the corn was under irrigated condition, therefore, extensive weed patches were observed between the paths. The laser scanner ground filtering data was compared to a photogrammetry-based aerial survey that we have carried out at the beginning of the vegetation cycle at the same parcel. Our results showed both the potentials and limitations of this sensor for precision agriculture. The laser beams produced significant amount of noise between the paths that had to be cleaned to extract the ground surface below the corn canopy. Based on our data processing methods we were able to delineate similar drainage networks within the parcel that was also processed from the initial aerial survey. However, the UAS LiDAR gained the most accurate surface reconstruction at the more clear grassland patches around the parcel. 

L. Bertalan was supported by the INKP2022-13 grant of the Hungarian Academy of Sciences. This research was funded by the Thematic Excellence Programme (TKP2020-NKA-04) of the Ministry for Innovation and Technology in Hungary. This research was also influenced by the COST Action CA16219 “HARMONIOUS - Harmonization of UAS techniques for agricultural and natural ecosystems monitoring”.

How to cite: Bertalan, L., Riczu, P., Bors, R., Szabó, S., and Eltner, A.: Application of UAS laser scanning for precision crop monitoring in Hungary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1185, https://doi.org/10.5194/egusphere-egu22-1185, 2022.

Land cover dynamics play a vital role in many scientific fields, such as natural resources management, environmental research, climate modeling, and soil biogeochemistry studies; thus, understanding the spatio-temporal land cover status is important to design and implement conservation measures. Remote sensing products provide relevant information regarding spatial and temporal changes on the earth’s surface, and recently, time series analyses based on satellite images, and spectral indices have become a new tool for accurate monitoring of the spatial trend, and land cover changes over large areas. This work aims to determine the trends of vegetation spectral response expressed as the Normalized Difference Vegetation Index (NDVI) over the period 2005 and 2018 and compare these trends with the land-use and cover changes between 2005 and 2018 in wetland areas across Denmark. Change detection methods between two years based on bi-temporal information may lead up to the detection of pseudo-changes, which hinders the land-use and cover monitoring process at different scales. We studied the potentiality of including NDVI temporal curves derived from a yearly time-series Landsat TM images (30-m spatial resolution) to obtain more accurate change detection results. We computed the NDVI temporal trends using pixel-wise Theil-Sen and Man-Kendall tests, then we explored the relationship between NDVI trends and the different land-use and cover change classes. We found a significant relationship between NDVI trends and changes in land use and cover. Changes from cropland to wetland and cropland to forest coincided with statistically significant (p≤0.05) negative NDVI, and positive NDVI trends, respectively. Changes from grasslands to permanent wetlands corresponded with statistically significant negative NDVI trends. The difference in vegetation productivity trends could be indicative of the combined effect of human activity and climate. We show that this combined analysis provides a more complete picture of the land use and cover changes in wetland areas over Denmark. This analysis could be improved if the NDVI time series is seasonally aggregated.

How to cite: Gutierrez Diaz, J. S., Humlekrog Greve, M., and Wollesen de Jonge, L.: Trends in vegetation changes over wetland areas in Denmark using remote sensing data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2545, https://doi.org/10.5194/egusphere-egu22-2545, 2022.

Spectral libraries of different components forming forests – such as leaves, bark and forest floor – are needed in the development of remote sensing methods and land surface models, and for understanding the shortwave radiation regime and ecophysiological processes of forest canopies. This poster summarizes spectral libraries of boreal forest vegetation and lichens collected in several projects led by Aalto University. The spectral libraries comprise reflectance and transmittance spectra of leaves (or needles) of 25 tree species, reflectance spectra of tree bark, and reflectance spectra of different types of forest floor vegetation and lichens. The spectral libraries have been published as open data and are now readily available for the community to use. 

How to cite: Rautiainen, M., Hovi, A., Forsström, P., Juola, J., Kuusinen, N., and Schraik, D.: Open data sets on spectral properties of boreal forest components, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2711, https://doi.org/10.5194/egusphere-egu22-2711, 2022.

Although the C–H chains of petroleum derivatives display unique absorption features in the short-wave infrared (SWIR), it is a challenge to identify plastics on terrestrial surfaces. The diverse reflectance spectra caused by chemically varying polymer types and their different kinds of brightness and transparencies, which are, moreover, influenced further by the respective surface backgrounds. This paper investigates the capability of WorldView-3 (WV-3) satellite data, characterized by a high spatial resolution and equipped with eight distinct and relatively narrow SWIR bands suitable for global monitoring of different types of plastic materials. To meet the objective, hyperspectral measurements and simulations were conducted in the laboratory and by aircraft campaigns, based on the JPL-ECOSTRESS, USGS, and inhouse hyperspectral libraries, all of which are convolved to the spectral response functions of the WV-3 system. Experiments further supported the analyses wherein different plastic materials were placed on different backgrounds, and scaled percentages of plastics per pixel were modeled to determine the minimum detectable fractions. To determine the detectability of plastics with various chemical and physical properties and different fractions against diverse backgrounds, a knowledge-based classifier was developed, the routines of which are based on diagnostic spectral features in the SWIR range. The classifier shows outstanding results on various background scenarios for lab experimental imagery as well as for airborne data and it is further able to mask non-plastic materials. Three clusters of plastic materials can clearly be identified, based on spectra and imagery: The first cluster identifies aliphatic compounds, comprising polyethylene (PE), polyvinylchloride (PVC), ethylene vinyl acetate copolymer (EVAC), polypropylene (PP), polyoxymethylene (POM), polymethyl methacrylate (PMMA), and polyamide (PA). The second and third clusters are diagnostic for aromatic hydrocarbons, including polyethylene terephthalate (PET), polystyrene (PS), polycarbonate (PC), and styrene-acrylonitrile (SAN), respectively separated from polybutylene adipate terephthalate (PBAT), acrylonitrile butadiene styrene (ABS), and polyurethane (PU). The robustness of the classifier is examined on the basis of simulated spectra derived from our HySimCaR model, which has been developed inhouse. The model simulates radiation transfer by using virtual 3D scenarios and ray tracing, hence, enables the analysis of the influence of various factors, such as material brightness, transparency, and fractional coverage as well as different background materials. We validated our results by laboratory and simulated datasets and by tests using airborne data recorded at four distinct sites with different surface characteristics. The results of the classifier were further compared to results produced by another signature-based method, the spectral angle mapper (SAM) and a commonly used technique, the maximum likelihood estimation (MLE). Finally, we applied and successfully tested the classifier on WV-3 imagery of sites known for a high abundance of plastics in Almeria (Spain), Cairo (Egypt), and Accra, (Ghana, West Africa). Both airborne and WV-3 data were atmospherically corrected and transferred to “at-surface reflectances”. The results prove the combination of WV-3 data and the newly designed classifier to be an efficient and reliable approach to globally monitor and identify three clusters of plastic materials at various fractions on different backgrounds.

How to cite: Zhou, S.: A knowledge-based, validated classifier for the identification of aliphaticand aromatic plastics by WorldView-3 satellite data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3130, https://doi.org/10.5194/egusphere-egu22-3130, 2022.

The “La Fossa” summit crater of Vulcano island (Sicily, Italy) showed increasing volcanic activities, characterized by strong gases emissions and high soil temperatures, during July 2021 (https://cme.ingv.it/stato-di-attivita-dei-vulcani-eoliani/crisi-idrotermale-vulcano-2021). The National Civil Protection Department declared the “yellow alert” level and the Mayor of the island issued an order to prohibit citizens to stay in areas surrounding the harbor due to large amounts of gases emitted; an alternative accommodation was sought for about 250 persons. In this work, we report and analyze the surface temperature estimated by using satellite data (ASTER and Landsat-8) from 2000 to 2022. These analyses extend the study described in “Silvestri et al., 2018” which reports a time series of thermal anomalies from 2000 to 2018, with a focus on two specific sites of the Vulcano island: “La Fossa” and “Fangaia”. So, we updated the dataset up to 2022 and analyzed space-borne remotely sensed data of the surface temperature on the whole island. We applied the Pixel Purity Index technique to ASTER and Landsat-8 satellite data (GSD=90 m) in order to detect pixels that are most relevant from the thermal point of view; thus, we used these pixels as significant points for the time series analysis. Moreover, strong carbon dioxide emissions could be detected from satellite data acquired by the new Italian space mission PRISMA (GSD=30 m) carrying onboard a hyperspectral sensor operating in the range 0.4-2.5 µm; this possibility will be explored by analyzing data on active fumaroles in the island. The goal of the analysis is also to verify if volcanic activity variations (in terms of thermal anomalies and gases emissions), in the Vulcano island, can be detected by satellite data.

How to cite: Silvestri, M., Rabuffi, F., Romaniello, V., Musacchio, M., and Buongiorno, M. F.: The use of satellite data to support the volcanic monitoring during the last Vulcano island crisis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3532, https://doi.org/10.5194/egusphere-egu22-3532, 2022.

Forecasting volcanic and limnic eruption for improving early warning systems is crucial to prevent severe impact on human lives. One of the main triggers of explosive eruptions is volcanic gases which, contrary to the atmosphere, are easily detected in water column, particularly using hydro-acoustic methods [1]. Two pioneering studies have monitored gas venting into Kelud Crater Lake (Indonesia) from a hydroacoustic station shortly before a Plinian eruption in 1990 [1] and, nearly two decades later, by empirically quantifying CO2 fluxes by acoustic measurements in the same lake just before a non-explosive eruption [2]. However, despite hydroacoustic detection capabilities, fundamental advances are limited by technology performances. Overall acoustic detection of a bubble field is easy, while its quantification remains complex due to the 3D structure of clouds, heterogeneous bubbles sizes and acoustic interactions between them. It is thus necessary to accurately map the different bubble clouds, to monitor their evolution through time to reduce the volcanic risk, which is major in aqueous environments. Here, we present preliminary results of water column gas distributions and quantification from an Eifel crater lake (Germany), using iXblue Seapix 3D multi splitbeam echosounder. SeapiX acoustic array is based on very special geometry, a dual/steerable multibeam echosounder with a Mills Cross configuration. It allows a 120° x120° coverage (quasi realtime coverage) with 1.6° resolution, made by 128 single elements. All beams in all steering direction process Split Beam TS measurement to provide true acccurate volumic TS from all single target in the volume. Backscatter profiles of elements in the water column allowed to distinguish fish and gas bubbles, which demonstrates a potential for the development of an automatic gas detection module using the Seapix software. Ongoing research on the Target Strengh (TS) of bubbles suggest they are of very small size (35 μm), much smaller than observed elsewhere using single beam echosounders, which might also explain why, in the same spot, we did not observe gas bubbles using camera mounted on ROV. Using the steerable capability of the system, a recent mission performed a 4D monitoring of gas bubbling of a single gas plume, in a static position placed on a USV and anchored, raising new perspectives to anticipate the tipping point of a critical enhancement of gas release and to mitigate the volcanic risk.

[1] Vandemeulebrouck et al (2000) J. Volcanol. Geotherm. Res 97, 1-4: 443-456

[2] Caudron et al (2012) JGR: Solid Earth 117, B5

How to cite: Jouve, G., Caudron, C., Matte, G., and Mosca, F.: Monitoring gas dynamics in underwater volcanic environments using iXblue SeapiX multi split beam echosounder: an example from the Laacher See (Eifel, Germany), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3583, https://doi.org/10.5194/egusphere-egu22-3583, 2022.

Remote sensing is being used widely to detect, map, and monitor environmental changes and remains a rapidly developing field. The detection of dune movement rates is carried out in field since the 20^th century and through remote sensing, once the technical requirements were met in the 1970^th (Hugenholtz et al. 2011). A wide variety of imagery from the last four decades is freely available in the archives of Sentinel-2 and Landsat 5 to 8 satellite images with spatial resolutions ranging between 10 and 25 meters. Complementing these data sources, in this study, we additionally used CORONA KH-4B images from the 1960s and 1970s. Despite its age, the KH-4B satellite delivered a considerably high spatial resolution of up to 1.8 m, thus bridging a considerable time gap of high resolution imagery and enabling the detection and mapping of singular dunes and dune fields. These satellites were originally used to record military intelligence images before being declassified for scientific use in 1995. After georeferencing, these images were utilized to detect and quantify the rates and directions of sand dune movement as well as for the estimation of dune height through a simple trigonometric approach.

We focus on single dunes and their movement rates in the high-altitude intramontane Gonghe Basin in Central Asia. The location of the study area at the north-eastern edge of the Asian summer monsoon and the mid-latitude Westerlies makes it especially sensitive to climatic variability (Vimpere et al. 2020). The dominant south easterly dune migration directions are in good agreement with the prevailing wind patterns. Dune heights of ~8–28 meters and ~3-31 meters for the late 1960s and 2020s, respectively, were calculated. Also, movement rates of under one meter up to ~24 meters per year were assessed for the time range of the late 1960s and 2020s.References:

Hugenholtz, C., H., Levin, N., Barchyn, T.E., Baddock, M., C. (2012): Remote sensing and spatial analysis of Aeolian sand dunes: A review and outlook. Earth-Science Reviews 111, 319–334, https://doi.org/10.1016/j.earscirev.2011.11.006

Vimpere, L., Watkins, S., E., Castelltort, S. (2021): Continental interior parabolic dunes as a potential proxy for past climates. Global and Planetary Change, 206: 103622, https://doi.org/10.1016/j.gloplacha.2021.103622

How to cite: Dörwald, L., Walk, J., Lehmkuhl, F., and Stauch, G.: Remotely sensed dune movement rates in desert margins of Central Asia over five decades using satellite imagery, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4460, https://doi.org/10.5194/egusphere-egu22-4460, 2022.

Remote sensing measurements have benefited from a great technological improvement, which has allowed a higher degree of automation while increasing spatial and temporal resolution of the collected data. Multi-     scale and multi-frequency optical and radar satellite sensors, often adopted in an integrated manner, are starting to provide efficient solutions for controlling and monitoring rapidly evolving urban and natural areas. On the other hand, close range remote-sensing techniques, such as operated by UAV platforms, and innovative ground-based instruments offer, respectively, the chance to downscale the observation performing site-specific analysis at an enhanced resolution and to collect in-situ dataset for calibration and data quality. By improving the quantity and quality of the collected data, a better understanding of the in-going processes is possible and the setting up of a numerical forecast model for future scenarios.

Therefore, implementation of integrated techniques for environmental monitoring turns out to be a strategic solution to analyze hazardous areas at different spatial and temporal resolution. Research devoted to the optimization of data processing tools by means of AI algorithms has evolved with the aim of improving the level of information and its reliability. In this context, a great impact is linked to the availability of open data and open-source processing tools distributed after the Copernicus Program.

A review of the available technologies for environmental monitoring is provided including examples on experimental cases in areas affected by natural hazards (volcanic eruptions, landslides, coastal erosion, flooding, etc.) and human activities that can produce incidental damages on the environment (urbanization, agriculture, infrastructures, landfills, dumpsites, pollutions, etc.). In addition, the same approach is useful for monitoring the degradation of the cultural heritage sites. Finally, the capability of collecting fat at a global level contributed to the analysis of environmental and economic impacts consequent the Covid-19 pandemic.

How to cite: Marsella, M., Celauro, A., and Moriero, I.: An integrated approach for environmental multi-source remote sensing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6153, https://doi.org/10.5194/egusphere-egu22-6153, 2022.

Geochemical investigations of agricultural soils are fundamental to characterize pedosphere dynamics that sustain ecosystem services linked with agriculture. Parameters like soil moisture, soil organic matter (SOM), and soil organic carbon (SOC) are strong instruments to evaluate carbon sink potential.

Satellite Earth Observation is a significant source of free data that can be linked to soil characteristics and dynamics and employed to produce temporal series. Access to these data is nowadays facilitated by platforms such as ADAM (https://adamplatform.eu), which allow users to quickly search for, visualize and subset data products, greatly reducing the volume of data that end users must handle.

In this work we demonstrate the usefulness of such systems by carrying out a geochemical investigation of 100 superficial (0-15 cm) soil samples collected in the province of Ferrara (North-Eastern Italy) and using the ADAM platform to associate to each a time series of Sentinel 2 data. The samples were collected in October 2021 in fields that were ploughed or mono-cultivated at maize, soybean, rice, and winter vegetables. To obtain the average soil properties over a spatial scale larger than the satellite sensor resolution, we adopted a composite sampling strategy, merging 5 sub-samples collected at the vertexes and at the center of a 30x30 m² area. Soil granulometry was recognized from clay to medium sand, with exception of peat deposits. Soil moisture, and SOM, contents were estimated by loss on ignition (LOI), respectively at 105°C (values from 0.3 to 7.4 wt%), and 550°C (values from 2.1 to 21.0 wt%). SOC contents (values from 0.7 to 9.3 wt%) were determined through DIN19539 analysis performed with an Elementar soliTOC Cube. Using the ADAM platform, we associated a temporal series from 2016 to 2021 of the Sentinel 2 NDVI data product to each sampling location, using a cloud coverage mask to eliminate values taken on cloudy days. Localized phenological cycles for each year are recognizable in the remotely-sensed data. Hence, our database describes for each parcel, geochemical parameters and vegetative temporal series.

In a separate study, we also attempted to train a neural network to predict geochemical properties from the soil spectrum measured by the hyperspectral satellite PRISMA. We used the geochemical properties of our 100 samples as training data, associated with the PRISMA spectra of the sampling locations measured on April 7 2020, when, according to our NDVI data, none was covered in vegetation.

How to cite: Salani, G. M., Lissoni, M., Natali, S., and Bianchini, G.: Geochemical investigations of 100 superficial soils observed by Sentinel 2 and PRISMA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6983, https://doi.org/10.5194/egusphere-egu22-6983, 2022.

Many hydromorphological restoration measures have been applied on German water courses since 2000 the European water framework directive has been induced. The measures aim to improve the diversity of habitat alteration. Often a positive effect on aquatic biota can’t be detected, therefore implementation and the hydromorphological development of such measures can be questioned. But also the common monitoring and assessment methods for physical river habitat mapping can be questioned as they are limited in spatial scale and objectiveness of the mapper itself.

In the last decade, Unmaned Areal Vehicle (UAV) in combination with high-resolution sensors open new opportunities in a spatial and temporal scales. This research shows a case study of the river Lippe for the detection of hydromorphological habitat structures using Structure from Motion (SfM) and Deep learning based classification methods. In detail, this work discusses the difficulties of creating digital surface and orthomosaics from field survey data, but also shows results from a case study using a deep learning classification approach to identify physical river habitat structures.

How to cite: Dacheneder, F., Schulz, K., and Niemann, A.: AI-based hydromorphological assessment of river restoration using UAV-remote sensing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6995, https://doi.org/10.5194/egusphere-egu22-6995, 2022.

Indices are designed to differentiate land use and land cover classes to avoid misinterpretation of landscape features. The resemblances of spectral reflectance of mines with urban built-up and barren land cause difficulties in identification of objects. Open pit mines of Rampura-Agucha for Zn and Pb were selected for this study. The freely available data of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) was selected from the year of 2001 and 2003. It is observed that b1-b5/b1+b5 equation of ASTER imagery significantly differentiate Zn-Pb mine from urban settlement and other features. The reflected range (µm) for b1 and b5 is 0.52-0.60 (Visible and Near-Infrared) and 2.145-2.185 (Shortwave Infrared) respectively. The pixel values indicate higher reflectance of open pit suggesting feasibility of equation for differentiating it from barren and built-up area. The mine is rich in sphalerite followed by galena, pyrite and pyrrhotite in different proportions of abundance. Spectral reflectance depends on type of minerals hence need further studies to develop the index according to specific minerals and mines. In the mining regions, the role of temperature, moisture content, vegetation covers and high concentration of pollutants in variation of spectral reflectance are highly important. The developed index would be beneficial for tracing the extent of overburden dumps, tailings and mines at faster rate.

How to cite: Punia, A., Bharti, R., and Joshi, P. K.: Satellite imagery band ratio for mapping the open pit mines: A preliminary study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8296, https://doi.org/10.5194/egusphere-egu22-8296, 2022.

Identification of relatively stable ground control points is always difficult in satellite-based remote sensing microwave technology. In our case, we have analyzed the amplitude and phase of backscattered signal of artificial objects in the resolution cell. In 2020, we have temporarily installed a compact active transponder (CAT) to the top of the Satellite Geodetic Observatory (SGO). During this probation period we had tested the operation of this electronic corner reflector (ECR).

In November, 2021 we have deployed, adjusted and precisely aligned the CAT and also mounted a 90 cm inner leg of passive double-backflip triangular corner reflector pair (part of the Integrated Geodetic Reference Station) to serve as Persistent Scatterers. Hence, we have observed the behaviour of the complex microwave signal using interferometric synthetic aperture radar technique (InSAR), utilizing Sentinel-1 SAR high resolution images. We have concentrated to demonstrate the effect of the corner reflector (CR) installation: estimate the Signal-to-Clutter Ratio (SCR), calculate the Radar Cross Section (RCS), define the phase center in sub-pixel dimension over well-specified stack of time-series.

We are expecting and focusing to integrate the CRs as benchmarks, into our developing processing algorithm system to achieve more accurate results of surface displacement using ground control points. In addition, the function of this project is to contribute and ensure the extension of our passive corner reflector reference network (SENGA). In this paper, we present the interpretation of the recent outcomes.

How to cite: Horváth, R., Magyar, B., and Tóth, S.: Impact of different corner reflectors installation on InSAR time-series, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8417, https://doi.org/10.5194/egusphere-egu22-8417, 2022.

Coastal areas are socially, economically, and environmentally intensive zones. Their risk to various natural coastal hazards like coastal flooding, erosion, and storm surges has increased due to climate-induced changes in their forcing agents or hazard drivers (e.g. sea-level rise). The increased exposure (e.g. dense population living near the coast) and vulnerability (e.g. insufficient adaptation) to these hazards in the coastal areas have complicated the adaptation challenges.

Thus, monitoring coastal hazards is essential to inform suitable adaptation to increase the climate resilience of the coastal areas. In monitoring coastal climate hazards to develop coastal climate resilience, both the forcing agents and the coastal responses should be observed.

As coastal monitoring is often expensive and challenging, creating a database through a systematic analysis of low-cost sensing technologies, like UAV photogrammetry for monitoring the hazards and their drivers would be beneficial to the stakeholders. Real-time information from these low-cost sensors in complement to the existing institutional sensors will facilitate better adaptation policies including the development of early warning support for building coastal resilience. In addition, it would also provide a valuable dataset for validating coastal numerical models and providing insights into the relationship between these hazards and forcing agents. Additionally, such low-cost sensors would also create opportunities for engaging citizens in the data collection process, for efficient data collection, and increasing scientific literacy amongst the general public. For instance, in the Sensing Storm Surge Project (SSSP), citizen science was used to collect technical data to characterise estuarine storm surges, generating data useable in peer-reviewed Oceanography journals. Coastal areas show complex morphological changes in response to the forcing agents over a wide range of temporal and spatial scales. Thus, monitoring the hazards with a sufficient temporal and spatial resolution is imperative to distinguish the changes in these hazards/drivers due to climate change from natural variability. This will not only help address the response strategies to these hazards but also adjust these response strategies according to the changing vulnerability of a particular region.

The database of the low-lost sensors thus created is in no way exhaustive since those have been retrieved through a certain combination of keywords in databases like Sciencedirect, Web of Science, and Scopus, nonetheless it is useful as these are the latest low-cost sensors available to monitor the major coastal hazards in the vulnerable coastal regions.

How to cite: Ahmed, T., Creedon, L., Anton, I., and Gharbia, S.: The use of low-cost sensors for monitoring coastal climate hazards and developing early warning support against extreme events., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8825, https://doi.org/10.5194/egusphere-egu22-8825, 2022.

Recently, numerous agencies and administrations in their latest reports show how it’s impossible to overlook the negative impact of atmospheric air pollution on human health. In this regard, it’s essential to be able to understand the spatial and temporal distribution of the concentration of main pollutants, and its ways to change. Among the numerous strategies proposed to tackle this problem, from the ’70s the study of satellite data assumed a key role, extending the analyzes carried out only with ground tools.

In this work we analyzed the data acquired by TROPOMI (TROPOspheric Monitoring Instrument), a multispectral imaging spectrometer mounted onboard the ESA Copernicus Sentinel-5P satellite (orbiting since October 2017) and specifically focused on mapping atmospheric composition. In particular, we processed the TROPOMI NO₂ products acquired over Piedmont Region (Italy) between 2018 and 2021.  We obtain preliminary results by comparing the satellite-derived tropospheric NO₂ columns data with ground-based NO₂ concentration acquired by the ARPA-Piemonte network in different urban and geomorphological contexts. In particular, we compared the TROPOMI-derived time series with the acquisitions of ground stations located in urban and suburban areas (e.g. in the city of Turin), identified as “traffic stations”, and in rural areas (low population density and countryside areas) identified as “background stations”. The results allow us to investigate the correlation and coherence between the two datasets and discuss the added values and limits of satellite data in different environmental contexts, with the prospective of providing NO₂ concentration maps of the Piedmont Region.

How to cite: Campus, A., Acquaotta, F., and Coppola, D.: Mapping NO2 pollution in Piedmont Region (Italy) using TROPOMI: preliminary results, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9328, https://doi.org/10.5194/egusphere-egu22-9328, 2022.

Remote sensing techniques are an ever-growing reliable means for monitoring, detecting and analysing the spatial and temporal changes of solid waste and landfill sites. In this paper, different UAV and satellite sensors are used to detect, characterize and monitor dumpsites in Sicily (Italy). In particular, data acquired and processed are (i) high-density point clouds detected from LIDAR sensor; (ii) optical photograms with a resolution of 3 cm; (iii) thermal photograms with a resolution of 5 cm/pixel and (iv) multispectral photograms with 5 cm/pixel. High spatial resolution UAV multispectral and thermal remote sensing allowed for the extraction of indicators, such as the Normalized Difference Vegetation Index (NDVI) and the Land Surface Temperature (LST), useful to characterize the changes in the vegetation and the skin temperature increase due to organic waste decomposition, respectively. On the other hand, the processing of UAV optical images to extract high-resolution orthophotos and their integration with high-density point clouds obtained from LIDAR, were used to provide the identification of the effective perimeter of the landfill body and the extraction of waste volumes. These products were integrated and compared with those obtained from different kinds of medium-to-high spatial resolution satellite images, such as from Landsat, Aster, Sentinel-2 and Planetscope sensors. Results show that UAV data represents an excellent opportunity for detecting and characterizing dumpsites with an extremely high detail, and that the joint use with satellite data is recommended for having a comparison on different scales, allowing continuous monitoring. Additional SAR data methodologies will be investigated for evaluating the landfill body landslides over the years that could be integrated with high resolution satellite multispectral and hyperspectral images for monitoring dumpsites environmental impact.

How to cite: Celauro, A., Cagnizi, M., Cappello, A., D'Amato, E., D'Aranno, P. J. V., Ganci, G., Lodato, L., Marini, I., Marsella, M., and Moriero, I.: Large and small-scale multi-sensors remote sensing for dumpsites characterization and monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10455, https://doi.org/10.5194/egusphere-egu22-10455, 2022.

Information of crop sowing dates is important to enhance the accuracy of crop models and for the assessments of crop requirements during the growing seasons. The sowing calendars of densely harvested areas are often driven by heterogeneous factors like annual crop rotations, crop switches and the alternation of winter and summer products over the same fields. Remote sensing is widely used for agricultural applications, especially to maximize crop yields through precision farming tools. Indices combining optical and infrared bands are particularly suitable for the crop classification algorithms and the plant health monitoring. Synthetic Aperture Radar (SAR) is often used in agriculture to classify irrigated and rainfed fields, due to its high sensitivity to soil water content. Despite SAR data are also used to identify changes in the ground roughness, this information has been rarely combined with optical data to identify crop sowing dates at the field scale.

In this study, SAR data from Sentinel-1 and NDVI derived from multispectral (MSI) acquisitions of Sentinal-2 have been used to identify the sowing dates of maize over a densely harvested pilot area in South Piedmont (Italy). NDVI data have been used to identify maize fields together with the agricultural geodatabase provided by the Piedmont public authority. The moisture-induced noise of SAR data has been filtered to avoid the impact of precipitation on the radar signal during the bare soil phase. Combining the VH and VV bands acquired by Sentinel-1 it was possible to identify the moment when maize plants break through the soil in each field.

Results show a good alignment with the information of sowing periods acquired from local farmers, also in terms of multiple growing seasons due to the presence of different maize types. The distribution of sowing dates points out that most of the maize is sown during the second half of May, while the other fields are sown even a month later after the harvesting of winter crops. The method proposed in this study may lead to significant applications in the agriculture monitoring, providing useful information for crop-related management policies. The combined use of SAR and NDVI data has the potential to improve the crop models for the benefit of yields and food security.

How to cite: Rolle, M., Zribi, M., Tamea, S., and Claps, P.: Estimation of maize sowing dates from Sentinel 1&2 data, over South Piedmont, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10490, https://doi.org/10.5194/egusphere-egu22-10490, 2022.

Tenosique is a small town located on the border between Mexico and Guatemala, on the banks of the Usumacinta River. The area is considered a tropical climate with swampy and jungle areas. Previous studies had exposed the changes in vegetation cover related to the public policies applied at the site. Some examples of these policies are: the 1917 agrarian reform of land distribution to the peasants for cultivation, in 1938 concessions were made to national and foreign companies to exploit forest resources; in 1958 the agrarian reform for cultivation made the agricultural zone advance towards the jungle forest; in 1965 the food crisis promoted livestock; in 1976 it opted for the extraction of oil, and with the economic crisis in 1982 the financial support to the peasants and their ejidos is withdrawn, and finally in 2008 this area becomes a flora and fauna protection area. Past studies have been developed from a social and artistic point of view as well as quantifiable with the use of Landsat satellite images, covering large temporalities as well as a regional coverage scale, however, the results resolutions have made their interpretation difficult, reporting only the 20% plant loss over time. The objective of this project is to update the pre-existing study using high-resolution images, on a smaller surface. For this, 5-meter resolution Rapideye satellite images were downloaded from the Planet platform (Planet Application Program Interface: In Space for Life on Earth) with the help of an educational license obtained from an artistic quality project. The temporality of the images ranges from 2010 to 2020. The methodology includes corresponding atmospheric corrections, the supervised classification, and the coverage analysis obtained from the application of the Normalized Difference Vegetation Index (NDVI).  Conclusions show the impact of the inputs resolution improvement in the study.

How to cite: Nieto Butrón, J. J., Ramírez Serrato, N. L., Jácome Paz, M. P., Ruiz Santos, T. X., and Manuel Núñez, J.: Use of Rapideye images from the planet platform to update vegetation cover studies in Tenosique, Tabasco, Mexico., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10607, https://doi.org/10.5194/egusphere-egu22-10607, 2022.

In sub-Saharan Africa, artisanal and small-scale mining (ASM) represents a source of subsistence for a significant number of individuals. While 40 million people officially work in ASM across 80 countries, more than 150 million rely indirectly upon ASM. However, because ASM is often illegal, and uncontrolled, the materials employed in the excavation process are highly dangerous for the environment, as well as for the people involved in the mining activities. One of the most important aspects regarding ASM is their localization, which currently is missing in most of the African regions. ASM inventories are crucial for the planning of safety and environmental remediation interventions. Furthermore, the past location of ASM could be used to predict the spatial probability of the creation of newborn mines. To this end, we propose a Deep Learning (DL) based approach able to exploit Sentinel-2 open-source data and a non-complete small-size mine inventory to accomplish this task. The area chosen for this study lies in northern Burkina Faso, Africa. The area is chosen for its peculiar semi-desert environment which, in addition to being a per se challenging mapping environment, presents a wide spatial variability. Moreover, given the high level of danger involved in field mapping, it is fundamental to develop reliable remote sensing-based methods able to detect ASM. Performance comparison of two convolutional neural networks (CNNs) architectures is provided, along with an in-depth analysis of the predictions when dealing both with dry and rainy seasons. Models’ predictions are compared against an inventory obtained by manual mapping of Sentinel-2 tiles, with the help of multitemporal interpretation of Google Earth imagery. The findings show that this approach can detect ASM in semi-desertic areas starting with a few samples at a low cost in terms of both human and financial resources.

How to cite: Cuevas-González, M., Nava, L., Monserrat, O., Catani, F., and Meena, S. R.: Deep Learning and Sentinel-2 data for artisanal mine detection in a semi-desert area, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11409, https://doi.org/10.5194/egusphere-egu22-11409, 2022.

Palo Verde National Park, located in the northwest of Costa Rica, contains a wetland plain of international ecological importance in Central America. It is home of a rich biodiversity and provides vital shelter for over 60 species of migratory and resident birds.

From the 1980’s onward, the wetland landscape has shifted from diverse vegetation and large open water areas to a near monotypic stand of cattail (Typha domingensis). This resulted into a sharp reduction in the number of birds in the area, as many bird species prefer other native plants and open water for feeding, nesting and for shelter. The Fangueo technique, which consists in crushing the plant under water using a tractor equipped with angle-iron paddle wheels has been adopted to reduce the spread of Typha.

This plant management technique typically results in a significant decrease in Typha population in the first year after its implementation, as well as an increase in plant diversity and open water area.

In this study, we used historical Landsat and Sentinel imagery to investigate the medium to long-term impact of Fangueo on vegetation and open water. We found that invasive vegetation regrowth happened faster than previous studies had indicated. The increase in open water areas was therefore short-lived. This result questions the adequacy of this technique for invasive plant management.

This work highlights how crucial simple remote sensing methods can be for assessing the adequacy of supposedly effective environmental management practices, and for informing stakeholders.

How to cite: Toussaint, F., Alonso, A., and Javaux, M.: Questioning the adequacy of an invasive plant management technique through remote sensing observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11908, https://doi.org/10.5194/egusphere-egu22-11908, 2022.

Underground mining, regardless of the excavation method used, has an impact on the terrain surface. For this reason, continuous monitoring of the ground surface above the excavations is necessary. Deformations on the ground surface occur with a time delay in relation to the mining works, which poses a risk of significant deformations in built-up areas, leading to building disasters. In addition to monitoring, it is therefore necessary to forecast displacements, which at present is usually done using the empirical integral models, which describes the shape of a fully formed subsidence basin and require detailed knowledge of the geological situation and parameters of the deposit. However, insufficiently precise determination of coefficients may lead to significant errors in calculations. Machine learning can be an interesting alternative to predict ground displacement in mining areas. Machine learning algorithms fit a model to a set of input data so that it best represents all the correlations and trends detected in the set. However, the fitting process must be controlled to avoid overfitting. The validated model can then be used to detect new deformations on the ground surface, categorize the resulting displacements, or predict the value of subsidence. In this case ARIMA model (Auto-Regressive Integrated Moving Average) was used to predict deformation values for single points placed in the centers of the subsidence basins in the LGCB (Legnica-Głogów Copper Belt) area. The InSAR time series calculated using the SBAS method for the years 2016-2021 was used as input data. The results were compared with the persistence model, against which there was an improvement in accuracy of several percentage points.

How to cite: Sompolski, M., Tympalski, M., Kopeć, A., and Milczarek, W.: Application of the autoregressive integrated moving average (ARIMA) model in prediction of mining ground surface displacement, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12697, https://doi.org/10.5194/egusphere-egu22-12697, 2022.

In our study, we tested a UAV-based IRT and Structure from Motion (SfM) for the identification of CO2 rich gas emission areas at Ciomadul dormant volcanic area, Eastern Carpathians. Our aim is to demonstrate the efficiency of the identification method providing example from a case-study in the Eastern Carpathians.

The gas emissions from Ciomadul come with high flux and are of magmatic origin, associated with the volcanic activity in the past. We had the following assumptions before performing the measurements with the drone: the temperature of the gas vents is constant, as well as their flux, variability is represented only by the changes in ambient temperature. We had previous knowledge on the temperature of the gas emissions (6 °C), so we chose periods when the ambient temperature is either lower or higher than the temperature of the gas. We performed several field observations with the camera both at daytime and in the evening.

The acquisition of UAV photography was made using a DJI Mavic 2 Enterprise Dual drone. This device is equipped with a 12 MP visual camera (RGB) with a 1/2.3" CMOS sensor. The visual camera has a lens with field of view of approx. 85°, 24 mm (35 mm format equivalent) lens with an aperture of f/2.8. It was also equipped with an Integrated Radiometric FLIR® Thermal Sensor. It is an Uncooled VOx Microbolometer with a horizontal field of view of 57° and f/1.1 aperture, sensor resolution is 160x120 (640x480 image size) and a spectral band of 8-14 μm.

The gas vents were clearly visible on the thermal images, and we discovered additional seeps that were not identified before. Later we confirmed the presence of the gas emissions with in situ measurements on the concentrations of CO2. The visibility of the gas emissions was influenced by parameters like temperature, the orientation of the gas vent, the influence of sunlight, the flux of the gas vent, etc.

How to cite: Kis, B., Tămaș, D. M., Tămaș, A., and Szalay, R.: Using UAV-based Infrared Thermometry in the identification of gas seeps: a case study from Ciomadul dormant volcano (Eastern Carpathians, Romania), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12774, https://doi.org/10.5194/egusphere-egu22-12774, 2022.

The large difference in the degree of discrimination of stable carbon isotopes (δ¹³C) between C₃ and C₄ plants has been widely used to retrieve the palaeoenvironmental condition by analysing δ¹³C of bulk sedimentary organic matter (SOM). Underlying in these studies was the assumption that carbon retains the pristine signature of its photosynthetic pathway during later stages of decomposition in soil and sediments. However, there remains considerable uncertainty associated with studies of SOM, especially those from marginal marine environments. The probable presence of organic matter derived from varied sources, e.g., marine sources, terrestrial C_3, and C₄ plants make reconstruction of the paleo-environment difficult using δ¹³C_SOM as a stand-alone tool. The sediments also undergo different stages of microbial decomposition, which can also alter the original organic carbon source signatures. Hence a robust method needs to be developed for identifying the specific phase that can withstand the alteration of the original δ¹³C of SOM. In the present study, we attempted to develop a simple means for identifying a robust oxidation-resistant organic carbon (OROC) phase for bulk isotopic analysis. The data along with the straight-chain n-alkane lipid compound were used to retrieve the Holocene (last 10 Kyr) paleo-environment from a sediment core raised from the Rann of Kachchh, western India. One purpose was to see if the climate had any role in the growth and collapse of an Indus Valley Civilisation (IVC) metropolis Dholavira, a UNESCO heritage site in the vicinity of the core location.

The sediment samples were chemically treated over different oxidation times (24 to 240 hours) following the commonly used dichromate oxidation method (0.1M K₂Cr₂O₇/ 2M H₂SO₄, 60 ⁰C). No more oxidation loss was observed between pre-and post-treatment of SOM after 72 hours suggesting that the remaining organic carbon represents the most resistant phase. The isotopic composition (δ¹³C_OROC)would thus represent the original isotopic signature of the refractory organic carbon. In the specific sediment core, the δ¹³C_OROC values showed no significant difference from the δ¹³C_SOM exhibiting a good down-depth correlation (R² >0.8). The δ¹³C data of the core top sediment along with the modern plants in the Rann suggest that local vegetation dominantly controlled the organic matter composition. The efficacy of the method was also tested by analysing δ¹³C_OROC and δ¹³C_SOM (δ¹³C_SOM ranged from -18.2 ‰ to -20.6 ‰) in ten marine sediment samples from the northern Indian Ocean indicating preservation of marine organic matters after the oxidation experiment. The sediment core data suggest a mixture of terrestrial C₃, C₄, and marine organic matter throughout the Holocene period. A significant increase in the concentration of C₄ photosynthesizing plant groups around 4.2 Kyr is observed and most likely is an expression of enhanced aridity due to the Meghalayan age drought that pervaded the Indian subcontinent and beyond. This is fascinating as the drought has earlier been linked to the collapse of the IVC based on other proxies.

How to cite: Ram, F., Thakkar, M., Chauhan, G., Bhusan, R., Juyal, N., and Sarkar, A.: Carbon isotope and organic geochemistry of the Holocene sediments from Rann of Kachchh: implications to the preservation of organic matter and climate during the Indus Valley Civilisation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-555, https://doi.org/10.5194/egusphere-egu22-555, 2022.

Vertical profiles of Tl, Pb and Zn concentrations and Tl and Pb isotopic ratios in a contaminated peatland/fen (Wolbrom, Poland) were studied to address questions regarding (i) potential long-term immobility of Tl in a peat profile, and (ii) a possible link in Tl isotopic signatures between a Tl source and a peat sample. Both prerequisites are required for using peatlands as archives of atmospheric Tl deposition and Tl isotopic ratios as a source proxy. We demonstrate that Tl is an immobile element in peat with a conservative pattern synonymous to that of Pb, and in contrast to Zn. However, the peat Tl record was more affected by geogenic source(s), as inferred from the calculated element enrichments. The finding further implies that Tl was largely absent from the pre-industrial emissions (>~250 years BP). The measured variations in Tl isotopic ratios in respective peat samples suggest a consistency with anthropogenic Tl (ε²⁰⁵Tl between ~ -3 and −4), as well as with background Tl isotopic values in the study area (ε²⁰⁵Tl between ~0 and −1), in line with detected ²⁰⁶Pb/²⁰⁷Pb ratios (1.16–1.19). Therefore, we propose that peatlands can be used for monitoring trends in Tl deposition and that Tl isotopic ratios can serve to distinguish its origin(s). However, given that the studied fen has a particularly complicated geochemistry (attributed to significant environmental changes in its history), it seems that ombrotrophic peatlands could be better suited for this type of Tl research.

How to cite: Vanek, A., Vejvodova, K., Mihaljevic, M., Ettler, V., Penizek, V., Trubac, J., Sutkowska, K., Teper, L., Golias, V., and Vankova, M.: Thallium and lead variations in a contaminated peatland: An isotopic study from a mining/smelting area, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1056, https://doi.org/10.5194/egusphere-egu22-1056, 2022.

Nitrous oxide (N₂O) dominates greenhouse gas emissions in wastewater treatment plants (WWTPs). Formation of N₂O occurs during biological nitrogen removal, involves multiple microbial pathways, and is typically very dynamic. Consequently, N₂O mitigation strategies require an improved understanding of nitrogen transformation pathways and their modulating controls. Analyses of the nitrogen (N) and oxygen (O) isotopic composition of N₂O and its substrates at natural abundance have been shown to provide valuable information on formation and reduction pathways in laboratory settings, but have never been applied to full-scale WWTPs.

Here we show that N-species isotope ratio measurements at natural abundance level, combined with long-term N₂O monitoring, allow identification of the N₂O production pathways in a full-scale plug-flow WWTP (Hofen, Switzerland). The proposed approach can also be applied to other activated sludge systems. Heterotrophic denitrification appears as the main N₂O production pathway under all tested process conditions, while nitrifier denitrification was less important, and more variable. N₂O production by hydroxylamine oxidation was not observed. Fractional N₂O elimination by reduction to dinitrogen (N₂) during anoxic conditions was clearly indicated by a concomitant increase in SP, δ¹⁸O(N₂O) and δ¹⁵N(N₂O). The extent of N₂O reduction correlated with the availability of dissolved inorganic N and organic substrates, which explains the link between diurnal N₂O emission dynamics and organic substrate fluctuations. Consequently, dosing ammonium-rich reject water under low-organic-substrate conditions is unfavourable, as it is very likely to cause high net N₂O emissions.

Our results demonstrate that monitoring of the N₂O isotopic composition holds a high potential to disentangle N₂O formation mechanisms in engineered systems, such as full-scale WWTP. Our study serves as a starting point for advanced campaigns in the future combining isotopic technologies in WWTP with complementary approaches, such as mathematical modelling of N₂O formation or microbial assays to develop efficient N₂O mitigation strategies.

How to cite: Mohn, J., Gruber, W., Magyar, P., Zeyer, K., von Känel, L., Morgenroth, E., Lehmann, M. F., Braun, D., and Joss, A.: Tracing N2O formation in full-scale wastewater treatment with natural abundance isotopes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2352, https://doi.org/10.5194/egusphere-egu22-2352, 2022.

Impurities in CaCO₃ minerals, present as ion substitutions (e.g., Mg²⁺ for Ca²⁺, SO₄^2- for CO₃^2-), are common and known to affect the fractionation of isotopes between the mineral and its parent fluid (e.g., the carbonate–water O isotope fractionation, the CAS–SO₄^2- S isotope fractionation). The difficulty in achieving isotopic equilibrium during experimental precipitation of carbonate minerals motivates the calculation of such effects by ab initio DFT methods. However, even a single substitution in a model lattice composed of as many atoms as computationally possible results in impurity concentrations that are much higher than those typical of most natural and experimental samples. For example, calculations of the CAS–SO₄^2- S isotope fractionation were performed at CAS concentrations of 59,000 and 30,000 ppm in calcite and aragonite, respectively, ∼threefold higher than the highest natural concentrations. The calculations yielded a CAS–SO₄^2- S isotope fractionation of 3.6 and 4.5‰ in calcite and aragonite (at 25°C), respectively, at odds with experimental values of ∼1‰ at the highest CAS concentrations in both calcite and aragonite. It is unknown whether the disagreement arises from the much higher CAS concentration in the calculations than in the experiments.

To overcome these computational limitations, we developed an approach in which the fractionation in the computationally largest possible “doped” model lattice is combined with the fractionation in a “pure” lattice. Using this approach, we determined the dependence of mineral–solution isotopic fractionation on the concentration of SO₄^2- and Mg²⁺ impurities in CaCO₃. The doped and pure lattices were modeled using ab initio methods implemented in the PWscf code of the Quantum ESPRESSO package, using periodic boundary conditions and the PBE exchange-correlation functional. Trigonal calcite and orthorhombic aragonite unit cells were used to form supercells of various dimensions containing 10 to 540 atoms. The ionic cores were described by ultrasoft pseudopotential and the Brillouin zone sampling was restricted to a single k-point for large supercells. Doped supercells contained a single SO₄^2- or Mg²⁺, and pure cells contained none. We calculated the defect formation energies and observed that the spurious effect from the impurities in imaginary supercells is minimized for a supercell size of ∼40 atoms or more. Phonon frequencies were calculated for various isotopic combinations using the PHonon code, and the frequencies were used to calculate the isotopic fractionation using the reduced partition function theory. The dependence of the bulk mineral–solution isotopic fractionation on the impurity concentration was then calculated as a weighted average of a single doped supercell and an arbitrary number of pure supercells. We will present the impurity dependence of the mineral–solution fractionation of O, C, Ca, Mg, and S isotopes and the carbonate clumped isotope composition of the CaCO₃, and compare to observations, where available. We suggest that a similar approach can be used to study the effect of any impurity, at an arbitrary concentration, on any isotopic system, in any mineral.

How to cite: Pramanik, C. and Halevy, I.: Ab initio calculations of the isotopic effects of sulfate and Mg impurities in carbonate minerals, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2569, https://doi.org/10.5194/egusphere-egu22-2569, 2022.

The impact of submarine groundwater discharge (SGD) on coastal biogeochemistry is currently under intense investigation. SGD can impact diagenesis and in general act as a potential source of elements, especially dissolved carbon, to coastal surface waters. However, qualitative and quantitative assessments of SGD are challenging since it requires the identification of suitable geochemical tracers for the complex hydrological and biogeochemical processes in the subterranean estuary. In this communication, we report on combined investigations carried out in Königshafen Bay (North Frisian island Sylt, Germany), a tidal area in the eastern North Sea. Sampling encompassed vertical porewater gradients, and surface waters collected through transects in the bay, and in tidal cycles at the outlet of the bay. Potential surface and subterrestrial freshwater endmembers are used to assess the results. Besides major and minor elements, this study focuses on the stable carbon isotope composition of dissolved inorganic carbon (DIC) and the activity of radium (Ra) isotopes. Our main aim is to characterize the interaction between diagenesis and the composition of SGD, as well as the resulting impact on the carbon system of the water column, and, via tidal exchange extended to the coastal North Sea. Porewaters showed usually an increase of isotopically light DIC with depth and a freshening already in the top 50 cmbsf at some sites. This indicates that both, carbon diagenesis and mixing of seawater with fresh groundwaters at depth impact the distribution of DIC. The activities of the short-living Ra isotope (²²⁴Ra_ex) were higher in the bay compared to the open North Sea. Porewater activities were up to 30 times higher than in the bay’s surface waters with a maximum development at intermediate salinities. In the water column at the outlet of the bay, ²²⁴Ra_ex and ²²³Ra showed maximum activities during low tide as a consequence of the highest contribution of waters in contact with the sediments of the bay. Moreover, due to the high hydraulic gradient developed during low tide more contribution from potential endmembers enriched in Ra can be expected. Further work is on the way to quantify the impact of SGD on the tidal basin and the indirect role for the North Sea carbon system on different temporal and spatial scales.

 The investigations are supported by the DFG-project KiSNet, the BMBF project COOLSTYLE (CARBOSTORE), the DAAD, the DFG RTG Baltic TRANSCOAST, and the Leibniz IOW.

How to cite: Ehlert von Ahn, C. M., Jenner, A.-K., Scholten, J., Schell, A., Schmiedinger, I., Hoffmann, J., Roeser, P., Nantke, C., and Böttcher, M.: Isotope hydrogeochemistry investigations (223,224Ra, DI13C) on submarine groundwater discharge in a tidal bay (eastern North Sea), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3715, https://doi.org/10.5194/egusphere-egu22-3715, 2022.

The purpose of this study was to investigate the key geochemical and mineralogical factors that could affect the fractionation of stable thallium (Tl) isotopes in soil. A set of grassland soil samples enriched in geogenic Tl in combination with selected Tl-containing mineral materials from the Czech Republic (Kluky) were investigated for this purpose. A combination of X-ray diffraction analysis (XRD), chemical extractions and stable isotope analysis were used to understand the behaviour of Tl and its isotope systematics within the soil profile. The results demonstrate significant incorporation of Tl in pedogenic Mn-oxide, which led to a large accumulation of the heavy ²⁰⁵Tl isotope (~+14 ε²⁰⁵Tl units), presumably resulting from continuous redox reactions with Mn-oxides and systematic accumulation of heavy isotope fraction onto the oxide surface(s). Consequently, we concluded that the Mn-oxide-controlled Tl uptake is the primary cause of the observed ²⁰⁵Tl enrichment in the middle profile zone, at the A/B soil horizon interface, with up to +4 of ε²⁰⁵Tl. Furthermore, our results displayed a clear relationship between the Tl isotopic fractionation degree and the Mn-oxide soil concentration (R² = 0.6), as derived from the oxalate-extractable data. A combination of soil and mineralogical considerations suggests that ²⁰⁵Tl enrichment in the soil samples is also partly due to the Tl present in micaceous clay minerals, mainly illite, which is the predominant pedogenic Tl host phase. Supported by our previous results, this Tl behaviour can be inferred from systematic Mn-oxide degradation and the associated Tl (enriched in ²⁰⁵Tl) cycling in the studied soils and therefore, presumably in the redoximorphic soils in general.

How to cite: Vejvodová, K., Vaněk, A., Mihaljevič, M., Ettler, V., Trubač, J., Vaňková, M., Drahota, P., Vokurková, P., Penížek, V., Zádorová, T., Tejnecký, V., Pavlů, L., and Drábek, O.: The key controls of thallium isotopic fractionation in soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4462, https://doi.org/10.5194/egusphere-egu22-4462, 2022.

The soft-water lake vegetation is sensitive to changes in water quality, especially pH and nutrient concentration. Furthermore, little is known about the biogeochemistry of those types of water bodies. Therefore, to recognize the relationship between the aquatic plants and the co-created sediments, we applied in our study the analysis of stable carbon and nitrogen isotopic composition (δ¹³C and δ¹⁵N) of organic matter of ten characteristic plants for soft-water lakes and sediments on which they have grown. We investigated physicochemical parameters of two types of water: one from the immediate surroundings of plants and the second type collected just above or directly from sediment (if they were more organic and looser). In the middle of the vegetation season (June 2020), the studies were performed on 14 soft-water lakes along a pH gradient (from 4.78 to 9.21). We found a high positive relationship between δ¹³C values of plants and sediments (Spearman rank correlations r= 0.69; N=85) and moderate positive relationships between δ¹⁵N values of plants and sediments (r= 0.31; N=85). Both for δ¹³C and δ¹⁵N, the variability of plants isotopic values was higher in plants organic matter than in sediments (for plants; δ¹³C from -33.76‰ to -9.93‰ and δ¹⁵N from -5.49‰ to 5.95‰; for sediments δ¹³C from -30.13‰ to -13.60‰ and δ¹⁵N from -2.92‰ to 4.82‰). In the case of Lobelia dortmanna, Fontinalis antipyretica, Luronium natans and Isoëtes lacustris δ¹³C values were higher in organic matter of the sediments than in investigated aquatic plants. On the other hand, especially samples for Elodea canadensis and Myriophyllum alterniflorum had opposite patterns, where values of δ¹³C were much higher in plants. The δ¹⁵N values of plants were lower than those reported for the deposits, and this pattern was more constant, with two exceptions recorded for Luronium natans and Chara globularis. Comparing the physicochemical parameters of surrounding and sediments waters, we found only high differences in total nitrogen concentration (TN) where higher concentration was reported in sediment water. In addition, the distribution of environmental variables for both water from anong plants and sedimentary water (Principal Components Analyzes - PCA's) indicates a higher relationship between the values of δ¹³C and δ¹⁵N of plant and sediments organic matter and the TN concentration in the sediment water. Moreover, the results of PCA for both waters types showed some relationship of δ¹³C of plants and sediments with pH, conductivity and Ca²⁺ concentration, which were more evident for sediment water. Founded here, strong relationships between plants and sediments δ¹³C values might confirm that in the cases of most investigated plants, they highly participate in sediment creation in those low-productive soft-water lakes. However, this assumption is less established when we focus on δ¹⁵N results. Moreover, both δ¹³C and δ¹⁵N of plants organic matter varied more than sediments, suggesting that allochthonous materials are also engaged in sediments creations. The further species-specific analysis is needed to better explain the present trends and relationships.

The studies were financed by Polish National Science Centre, under project No 2019/32/C/NZ8/00147.

How to cite: Pronin, E., Banaś, K., Chmara, R., Ronowski, R., Merdalski, M., Szmeja, J., Santoni, A.-L., and Mathieu, O.: Variation of stable carbon and nitrogen isotopes composition of plants and sediments along pH gradient of soft-water lakes in Poland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4830, https://doi.org/10.5194/egusphere-egu22-4830, 2022.

The role that of fresh surface and ground water sources play on the coastal water balance, element balances, and the associated biogeochemical processes is currently a matter of intense debate and investigation. The measures of fresh and saline water mixing in coastal areas have been found to be challenging, however stable water isotopes (O-16, O-17, O-18), in combination with further hydrochemical tracers, provide a valuable tool to identify different sources, that are furthermore linked to different biogeochemical processes, e.g. impacting the benthic and pelagic carbon cycle.

In the present communication, we report on combined investigations in pore and surface waters of Königshafen Bay (North Frisian island Sylt, Germany), a tidal area in the eastern North Sea. In addition, tidal cycles at the outlet of the bay were sampled. Results are compared to potential surface and subterrestrial fresh water endmembers, open North Sea, submarine groundwater discharge in the backbarrier tidal area of Spiekeroog, as well as the Elbe river estuary. Besides dissolved major and minor elements, the stable water isotope composition is used to characterize the temporal and spatial distribution of different water sources to the bay and the seasonal dynamics in the water column. Porewater gradients indicate different degrees of freshening, locally already in the top 50 cm below the seafloor with spatial heterogeneity. Different fresh water endmembers are indicated both by the water isotope and hydrochemical signatures. It turns that at least two fresh water sources can be identified for sediments under SGD impact, that differ in composition from surface water sources draining into the southern North Sea. Further work is on the way to investigate the dynamics in the (sub)surface fresh water sources for the tidal basin and the link to other geochemical tracers, as well as the coupling to the dissolved carbon system on different temporal and spatial scales.

The investigations are supported by the DFG-project KiSNet, the BMBF project COOLSTYLE (CARBOSTORE), the DAAD, the DFG project Baltic Transcoast, and Leibniz IOW.

How to cite: Böttcher, M. E., Jenner, A.-K., Nantke, C., von Ahn, C. M. E., Schmiedinger, I., Schell, A., Patricia, R., Riedel, R., Janßen, S., Gilfedder, B. S., and Moosdorf, N.: Hydrology and -chemistry of a tidal basin (Königshafen, North Sea): A water isotope perspective, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5359, https://doi.org/10.5194/egusphere-egu22-5359, 2022.

Recent studies suggest that isotope ratios of the carbon-bound non-exchangeable hydrogen (δ²H) in plant cellulose and lipids can indicate changes in the primary carbon and energy metabolism; however, systematic investigations are scarce.

Here, we studied δ²H patterns in two different tobacco (N. sylvestris) model systems, where severe changes in the plant primary metabolism were known: 1) along a nitrogen (N) supply gradient and 2) in a starch-less knockout mutant (pgm). Specifically, we measured δ²H of water, bulk soluble sugars, transitory starch, and cellulose in leaves and roots, using a novel hot water vapor equilibration method and TC/EA-IRMS. Besides, we measured δ²H values of leaf n-alkanes with GC-IRMS.

We observed clear δ²H differences in sugars and starch along the N gradient and a ²H-enrichment of both assimilates in pgm compared to a wild type control. The photosynthetic ²H-fractionation between leaf water and sugars/starch reached a maximum of ca. 100‰ in both model systems and was related to changes in concentrations of primary metabolites (e.g. sugars, starch, organic and amino acids), enzymatic activities, gas-exchange, and growth. The signal of the primary carbon metabolism was also visible in δ²H of leaf and root cellulose in both system, but dampened compared to those of sugars and starch. In contrast, the signal was absent in leaf n-alkanes in both systems.

Our results provide the first direct evidence that changes in the primary leaf carbon metabolism are imprinted on δ²H of plant carbohydrates in leaf and roots. The metabolic signal might therefore be reconstructed from plant material of important paleo archives (e.g. tree-ring cellulose, lake sediments) and help to better understand plant-climate interactions. The absence of the signal in δ²H of leaf n-alkanes is surprising and suggests a strong difference in metabolic fluxes between carbohydrates and lipids. Yet, this observation may help to further disentangle the processes shaping hydrogen isotopes in plants.

How to cite: Lehmann, M. M., Schuler, P., Cormier, M.-A., Ghiasi, S., Werner, R. A., Saurer, M., and Wiesenberg, G.: Hydrogen isotopes in assimilates and cellulose, but not in n-alkanes, integrate signals of the plant primary carbon metabolism, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5442, https://doi.org/10.5194/egusphere-egu22-5442, 2022.

The Great Lakes basin is one of the world’s most important freshwater resources, critical not only to public water supply but also for agriculture, transportation, hydroelectric power, and as an ecosystem. Anthropogenic contamination in all Great Lakes has been causally linked to ecosystem deterioration since the start of the industrial revolution, and it has been pervasive and cumulative. A major anthropogenic contaminant in the Great Lakes is copper [(Cu): a trace metal that has been a concern for decades. Point-sources for Cu include industrial activities such as metal mining, smelting, and chemical industries. However, Cu is also introduced to surface waters from diffuse sources, such as fertilizer application or urban runoff, as well as by atmospheric deposition and natural weathering processes. The importance of these geogenic versus anthropogenic sources is spatiotemporally variable and there are a multitude of sources and processes controlling the environmental fate of Cu in the Great Lakes region that remain poorly quantified (Bentley et al., 2022). Nontraditional stable isotopes have proven useful as environmental tracers for metal contaminants in human-impacted areas and served as an excellent tool to quantify a variety of biogeochemical processes (i.e., adsorption to mineral and organic surfaces, biological uptake). To understand the impacts of anthropogenic activities on Cu concentrations in the environment, background Cu isotope compositions of relatively pristine environments must first be determined. However, Cu isotopic analyses of baseline conditions in the Great Lakes are extremely scarce. In this work, we explore the use of Cu isotope analyses to quantify the baselines and sources of Cu in two tributaries in the Great Lakes. Surface water samples were collected from 44 locations along the Spanish River (Lake Huron) and Trent River (Lake Ontario) in August 2021, together with samples of probable endmember phases that include (agricultural) soils, municipal wastewater effluents and mine waste materials in the respective catchments. Water quality in the studied catchments was variable (6.6 < pH < 9.1; 58.7 mg/L < alkalinity < 216.7 mg/L), with recorded Cu concentrations in the river water samples ranging between 0.79 to 4.88 ng/ml, tending towards higher concentrations upstream compared to downstream, and presenting peaks in specific locations, suggesting anomalous Cu input in these areas. δ⁶⁵Cu in the rivers analyzed (−1.02 to 0.09‰) present values above the natural average of upper continental crust (0.07 ± 0.10‰) and uncontaminated sedimentary materials from estuaries (−0.04 ± 0.18‰), revealing distinct mixing of two or more sources (including geogenic, mine waste and agriculture fertilizers). We contextualize the Cu compositions observed in surface water samples to those in endmember materials with mixing models and geospatial analysis of the catchments to quantify possible sources. Our results may help distinguish historic versus new contaminant sources and geogenic versus anthropogenic contributions, as well as major pathways by which metals are loaded into the Great Lakes, besides facilitating the protection of this critical freshwater resource from legacy and emerging metal pollution.

How to cite: Junqueira, T., Sullivan, K., Harrison, A., and Vriens, B.: Source-tracking metal contamination using Cu isotopes in two tributaries in the Great Lakes region, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6485, https://doi.org/10.5194/egusphere-egu22-6485, 2022.

Calcium sulfates are the dominating salts but the respective sulfate sources are debated. In order to quantify the relative contribution and spatial distribution of sulfate sources and to identify biological sulfate recycling processes, we analyzed δ¹⁸O_SO4, Δ¹⁷O_SO4, ⁸⁷Sr/⁸⁶Sr, and δ³⁴S_SO4 of sulfate from Atacama Desert soils (Chile). Surface samples were taken along four W-E transects from the Pacific coast to the Pre-Andean Cordillera between 19.5°S and 25°S. Additionally, lacustrine gypsum and sulfate extracted from groundwater feeding the Salar de Llamará and sodium sulfates from the Salar del Huasco were analyzed.

Sulfur from the ocean comprise high δ³⁴S_SO4 values compared with low δ³⁴S_SO4 volcanic sulfate allowing to estimate the marine sulfur contribution to the total sulfate sample. δ³⁴S_SO4 decreases with distance from the coast principally confirming previously published results [1]. Because Sr substitutes for Ca in Ca-Sulfates, ⁸⁷Sr/⁸⁶Sr follows similar systematics, at least for samples taken within the coastal fog zone (<1200 m).  However, δ³⁴S_SO4 and ⁸⁷Sr/⁸⁶Sr of samples taken above 1200 m are decoupled indicating sulfate dissolution and re-precipitation or deposition of supra-regional Ca-rich aerosols with high ⁸⁷Sr/⁸⁶Sr values.

Positive ∆¹⁷O_SO4 values observed in all analyzed samples (0.1‰ to 1.1‰) suggest a significant contribution from secondary atmospheric sulfate (SAS) to Atacama Desert soils. Distinct mass-independent ¹⁷O anomalies of SAS originate from atmospheric oxidation of reduced sulfur species from volcanic or anthropogenic emissions, or biogenic sulfur gases such as dimethyl sulfide (DMS) by O₃ or H₂O₂. Within our dataset we can distinguish between a SAS_(DMS) endmember, comprising high ∆¹⁷O_SO4 and δ³⁴S_SO4 and a SAS_Atacama endmember comprising moderate Δ¹⁷O_SO4 and low δ³⁴S_SO4. Highest Δ¹⁷O_SO4 values, interpreted to represent a pure SAS_Atacama endmember, are observed in samples from the Coastal Cordillera of the southernmost transect which is generally higher than the present maximum level of fog advection (1200 m). Lowering of Δ¹⁷O_SO4 values results from 1) dilution of the positive Δ¹⁷O_SO4 fromSAS by marine and/or terrestrial sulfate with Δ¹⁷O_SO4 ≈ 0‰, and 2) resetting of Δ¹⁷O_SO4 due to biological sulfate reduction and reoxidation. Lowest Δ¹⁷O_SO4 values are observed in sulfates from salars and soils from alluvial fans.

In general, Δ¹⁷O_SO4 andδ¹⁸O_SO4 of our data show an inverse relationship reflecting not only the source contributions but also biological sulfate cycling. Thus, large Δ¹⁷O_SO4 anomalies (≈1‰) that suggest a dominant contribution from SAS_Atacama, also indicate the relative absence of biologically processed sulfate and thus, low water availability.

[1] Rech et al. (2003), Geochim. Cosmochim. Acta 67, 575-586

How to cite: Klipsch, S., Herwartz, D., Voigt, C., Münker, C., Chong, G., Böttcher, M. E., and Staubwasser, M.: Insights into sulfate sources and water availability in the Atacama Desert through triple oxygen, strontium, and sulfur isotopes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7528, https://doi.org/10.5194/egusphere-egu22-7528, 2022.

The measurement of δ²H of non-exchangeable-H (δ²H_n) in organic matter (OM) by isotope-ratio mass spectrometry is often hampered by the difficulties in controlling H isotope exchange of the exchangeable H fraction (f_ex) and removal of residual moisture. The determination of δ²H_n in organic matter requires control of the isotopic composition of f_ex. This can be achieved through dual water H isotope exchange experiments. However, these experiments are laborious, sensitive to the method used (e.g. prior sample treatment, temperature, time) and are costly. This has resulted in a wide range of reported f_ex for known isotopic references. Moreover, it is not always clear that samples are completely dry following the H exchange experiments, leading to even larger variations. The δ²H_n data is typically used in ecological studies for source attribution due to the large observed separation between contributing end members. However, it is not clear to what degree the analytical errors in δ²H determined by incomplete H isotope exchange of f_ex and the residual moisture impact the source attribution. Here we developed a simple offline sample preparation system, the Isobox, and a protocol for the measurement of δ²H_n in natural OM as well as pure organic compounds. We performed dual water H isotopic exchange experiments with both liquid and vapor water at near 0 and 105°C respectively. We analyzed three keratin reference materials (KHS, CBS and USGS42), two amino acids (Isoleucine and Threonine), along with caffeine (USGS62) and polyethylene (IAEA-CH-7) as drying references. We have also used natural samples of demineralized soil and green algae to create known mixtures to test these methods and their analytical uncertainty impact on the source attribution. We show that the liquid water exchange experiments led to f_ex close to the theoretical expectations for both keratin and pure compounds. Depending on the research question careful determination with controlled dual water procedure for the determination of δ²H_n may be required. However, simple sample treatment with exposure to a single isotopically known water can be used to derive δ²H for source attribution. The offline sample preparation system and equilibration method we developed is simple, accurate and cost effective and can be implemented in virtually any laboratory for the analysis of a wider range of OM types.

How to cite: Gudasz, C., Lundholm, J., Geibrink, E., Öquist, M., and Karlsson, J.: An offline sample preparation system and water exchange reaction method for the measurement of δ2H of non-exchangeable hydrogen in organic matter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8197, https://doi.org/10.5194/egusphere-egu22-8197, 2022.

The Nova-Bollinger Ni-Cu sulfide ore deposit is hosted in layered mafic and ultramafic intrusive rocks of the Mesoproterozoic Albany-Fraser zone, located about 160 km east-northeast of Norseman, Western Australia. Nova and Bollinger are two adjacent but spatially distinct orebodies with a combined pre-mining resource estimate of 13.1 million tonnes (Mt) with about 2 % Ni, 0.8 % Cu, and 0.1 % Co (IGO Ltd., unpublished data, 2018) ¹. Significant challenges are posed in exploring for magmatic Ni-Cu deposits that are buried under post-mineral cover. For example, electromagnetic and gravity surveys identify numerous targets but are unable to distinguish economic mineralization. Previously, it was suggested that the regular pattern of S isotope compositions (δ³⁴S_CDT) of surficial sulfate in lakes and groundwaters in southern Australia provides an ideal baseline against which to search for anomalous δ³⁴S_CDT values associated with base-metal or gold mineralization ². In the absence of lakes and readily accessible groundwaters in prospective areas, soils and rocks make a convenient sampling medium. Here, we investigated the exploration potential of δ³⁴S_CDT of the trace sulfur content of unconsolidated surface sediments, saprolite, and bedrock samples above Nova and two nearby sub-economic prospects, Griffin and Chimera. The δ³⁴S_CDT values likely reflect a two end-member system, with values ranging from -5.8 at depth to 21.4 ‰ near the surface, showing little dependence on lithology. Values in samples closer to the surface are similar to modern seawater sulfate that has a globally homogenous δ³⁴S_CDT value of 21.0 ± 0.2 ‰ ³, whereas at depth, values approach typical mantle S isotopic compositions of 0 ± 2 ‰ ⁴. In support of this, rocks at Nova have a δ³⁴S_CDT of around 0 ‰ and regional metagabbro are between -2 and 4 ‰ ⁵. On a regional scale, in both Western Australia (Yilgarn Block) and South Australia, the δ³⁴S_CDT values of surficial gypsum have a regular pattern over distances of up to 1000 km, with the highest values (~ 21 ‰) near coastlines decreasing to δ³⁴S_CDT values of ~ 14 ‰ further inland ². This is suggested to be predominantly the result of the delivery of salts to the Australian landscape as aerosols, with volatile biogenic S compounds of mostly marine origin (δ³⁴S_CDT of ~ 1 ‰) that proportionately increase in importance further inland resulting in decreasing  δ³⁴S_CDT values ². Located approximately 200 km inland, δ³⁴S_CDT results in samples within 10 metres of the surface at Nova, Griffin, and Chimera are in agreement with this and range from 12.6 to 20.4 ‰. Given that near-surface δ³⁴S_CDT values above Nova, Griffin, and Chimera appear to be mostly related to seawater-derived sulfate with minimal magmatic influence, δ³⁴S_CDT shows little potential as a field sampling technique to vector for deposits buried under post-mineral cover. However, at depth, δ³⁴S_CDT shows a clear relationship between the mixing of seawater sulfate and magmatic S weathering into the environment, indicating that analysis of S isotopes of otherwise apparently barren cores has utility in mineral exploration.

How to cite: Sullivan, K., Drummond, J., Polito, P., Stoltze, A., and Leybourne, M. I.: Sulfur isotope compositions in the weathering profile of magmatic Ni-Cu deposits in SW Australia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8563, https://doi.org/10.5194/egusphere-egu22-8563, 2022.

Rhenium (Re) is a redox-sensitive element. Recent advances in the precision of measurement of the stable isotopic composition of Re (δ¹⁸⁷Re) allow exploration of its potential as a proxy for paleoredox and/or chemical weathering ^[1]. However, as yet, there have been few studies reporting the geochemical cycling of Re and stable Re isotopes in the modern environments ^{[2] [3]}, and processes that regulate the Re isotope behavior in hydrothermal systems remain unexplored.

Here we present results of the analysis of Re concentration and δ¹⁸⁷Re (relative to NIST3143) for water samples collected from hydrothermal and groundwater systems in Iceland. We show that Re in basalt-hosted boiled hydrothermal fluids from Hellisheidi, Nesjavellir, Reykjanes and Svartsengi sites is isotopically heavier (δ¹⁸⁷Re = –0.01 to +0.32‰) than Re in Icelandic basalts (δ¹⁸⁷Re = ~–0.32‰). The direction of fractionation holds regardless of types of fluid reservoir (meteoric vs. seawater), and is consistent with precipitation of isotopically light sulfides in the hydrothermal system and/or kinetic fractionation of Re during degassing. By contrast, Re in cold (< 10°C) groundwaters collected from the Mývatn area is isotopically indistinguishable from host basalt. Natural hot spring waters exhibit variable δ¹⁸⁷Re values (–0.28 to +0.26‰), likely reflecting mixing between hydrothermal and groundwater endmembers. The relatively isotopically heavy δ¹⁸⁷Re from hydrothermal sources has the potential to modify the oceanic budget, which has implications for the isotope mass balance of Re.

[1] Dellinger et al. (2020) JAAS, 35, 377. [2] Dickson et al. (2020) GCA, 287, 221-228. [3] Dellinger et al. (2021) EPSL, 573, 117131.

How to cite: Wang, W., Dickson, A., Dellinger, M., Burton, K., Clark, D., Eggertsson, G. H., Einarsdóttir, Í. E., Hilton, R., Ingimarsson, H., Mesfin, K. G., and Prytulak, J.: Fractionation of stable rhenium isotopes in terrestial hydrothermal systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12211, https://doi.org/10.5194/egusphere-egu22-12211, 2022.

Land-ocean interactions in the coastal zone are of particular interest regarding the exchange of substances, like nutrients, carbon, sulfur, metals, and water. The rising sea level is and will enhance the pressure of salty solutions on previously fresh water ecosystems. We present here new results on the isotope biogeochemistry of a rewetted peatland, at the southern Baltic Sea, that is impacted by event-type flooding with brackish seawater. Sediment cores on transects through the wetland were investigated for their pore water and solid phase (mineral and organic matter) composition. Different fractions of the soils and solutions were analyzed for the elemental composition, mineral micro-textures, and the stable isotope composition (H, C, O, S) to understand the changes in water and biogeochemical carbon-sulfur-metal cycles due to flooding and the consequence for the development of sulfur isotope signatures in authigenic mineral phases and organic matter.

Flooding events with brackish water increased the availability of sulfate as an electron acceptor for microbial carbon transformations. This added sulfur impacted the remineralization capacity of organic substrates and created space for mineral authigenesis, with related iron sulfide textures. It yields isotope signals that are indicative for non-steady state biogeochemistry of coastal ecosystems and allow for a transfer of proxy information to other modern and past coastal organic-rich peatlands.

The soil cores from the peatland reflects the intense activity of sulfate-reducing bacteria and the associated formation of iron sulfides (essentially pyrite) and provided the isotope evidence for site-dependent sulfurization of organic matter. Sedimentary sulfur fractions and their stable isotope signatures are controlled by the availability of dissolved organic matter and/or methane, reactive iron, and in particular dissolved sulfate and, thereby, from the relative position with respect to the coast line, and depend on the surface topography and soil characteristics. Further mechanistic investigations consider the role of DOS upon changing sulfur substrate availability.

Acknowledgement for support by DFG-Baltic TRANSCOAST, ERASMUS, DAAD, Leibniz-IOW

How to cite: Jenner, A.-K., Böttcher, M. E., Fernández-Fernández, L. E., Otto, D., Zeller, M. A., Koebsch, F., Jurasinski, G., Kreuzburg, M., Rach, B., Winski, L., Westphal, J., Ehlert von Ahn, C. M., and Schmiedinger, I.: After the flood: Sulfur authigenesis and isotope discrimination in a rewetting coastal fen, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12236, https://doi.org/10.5194/egusphere-egu22-12236, 2022.

Contamination of soils by organic pollutants such as pesticides, hydrocarbons or chlorinated solvents in agricultural, urban and industrial soils is a widespread issue. Knowledge on the occurrence, extent and pathways of (bio)degradation of persistent pollutants in soil is crucial to improve the monitoring of their persistence and predict ecotoxicological risks. One of the latest important analytical developments is the coupling of gas/liquid-chromatography to continuous-flow isotope ratio mass spectrometry allowing to measure various stable isotopes ratios specific to each pollutant molecule. Starting from about the year 2000, compound-specific isotope analysis (CSIA), based on natural abundance, has successfully been applied to evaluate the occurrence and transformation pathways of industrial pollutants in groundwaters. However, the need of a sufficient mass of analyte for CSIA combined with low pesticide concentrations (sub-ug g^-1) and the co-enrichment of non-volatile soil components, leading to the so-called ‘matrix effect’ during chromatographic separation, currently challenge CSIA application to pesticide residues in soil. Here, we examined preparation procedures of soil samples to maximize the analytical performance for precise and sensitive CSIA without altering the isotope ratio of the target pesticides. Overall, our results emphasize the versatility of QuEChERS approaches as a standard preparation method for pesticide CSIA from soil samples and possible adaptations for specific matrix-analyte combinations to reach more selective extraction. Different families of pesticides with contrasted physico-chemical properties were extracted from various types of soil for CSIA from microcosms, mesocosms and field studies. No significant isotope fractionation for carbon (Δδ¹³C ≤ 1‰) and nitrogen (Δδ¹⁵N ≤ 0.5‰) was observed, despite variable extraction efficiencies. CSIA coupled to enantioselective analysis (ESIA) enabled to evaluate the degradation extent and mechanisms in soil of the chiral fungicide metalaxyl (i.e., S-MTY and R-MTY enantiomers). Significant enantioselective degradation (k_S-MTY= 0.007 – 0.011 day⁻¹ < k_R-MTY=0.03 – 0.07 day⁻¹) was associated with significant carbon stable isotope fractionation (Δδ¹³C_S-MTY from 2 to 6‰). Column mesocosm experiments showed that biodegradation of anilide herbicides and fungicides (i.e. acetochlor, alachlor, S-metolachlor, butachlor and metalaxyl) was favored in the soil solution of soil-plant systems, independently of the soil type, whereas degradation in soil remained limited. CSIA of terbutryn, an urban biocide commonly added in facade paints and renders, highlighted its persistence in outdoor soil lysimeters and its potential transport into groundwater. In a field study, we demonstrated the applicability of CSIA to track at the catchment scale the degradation and export of the pre-emergence herbicide S-metolachlor from soil to water and identify the contributing source areas. Based on maximum shifts in carbon stable isotope signatures (Δδ¹³C = 4.6 ± 0.5‰) of S-metolachlor we estimated maximum degradation in soil to have reached 96 ± 3% two months after first application. Altogether, this study emphasizes the variability degradation of different pesticides in soils and proposes a framework using CSIA to examine the contribution of pesticide dissipation processes in polluted urban and agricultural soils.

How to cite: Imfeld, G., Masbou, J., and Payraudeau, S.: Compound-specific isotope analysis (CSIA) of pesticide residues in soil to evaluate in situ degradation over space and time, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12261, https://doi.org/10.5194/egusphere-egu22-12261, 2022.

The Kigezi highlands, southwestern Uganda, is a mountainous tropical region with a high population density, intense rainfall, alternating wet and dry seasons and high weathering rates. As a result, the region is regularly affected by multiple natural hazards such as landslides, floods, heavy storms, and earthquakes. In addition, deforestation and land use changes are assumed to have an influence on the patterns of natural hazards and their impacts in the region. Landscape characteristics and dynamics controlling the occurrence and the spatio-temporal distribution of natural hazards in the region remain poorly understood. In this study, citizen science has been employed to document and understand the spatial and temporal occurrence of natural hazards that affect the Kigezi highlands in relation to the multi-decadal landscape change of the region. We present the methodological research framework involving three categories of participatory citizen scientists. First, a network of 15 geo-observers (i.e., citizens of local communities distributed across representative landscapes of the study area) was established in December 2019. The geo-observers were trained at using smartphones to collect information (processes and impacts) on eight different natural hazards occurring across their parishes. In a second phase, eight river watchers were selected at watershed level to monitor the stream flow characteristics. These watchers record stream water levels once daily and make flood observations. In both categories, validation and quality checks are done on the collected data for further analysis. Combining with high resolution rainfall monitoring using rain gauges installed in the watersheds, the data are expected to characterize catchment response to flash floods. Lastly, to reconstruct the historical landscape change and natural hazards occurrences in the region, 96 elderly citizens (>70 years of age) were engaged through interviews and focus group discussions to give an account of the evolution of their landscape over the past 60 years. We constructed a historical timeline for the region to complement the participatory mapping and in-depth interviews with the elderly citizens. During the first 24 months of the project, 240 natural hazard events with accurate timing information have been reported by the geo-observers. Conversion from natural tree species to exotic species, increased cultivation of hillslopes, road construction and abandonment of terraces and fallowing practices have accelerated natural hazards especially flash floods and landslides in the region. Complementing with the region’s historical photos of 1954 and satellite images, major landscape dynamics have been detected. The ongoing data collection involving detailed ground-based observations with citizens shows a promising trend in the generation of new knowledge about natural hazards in the region.

How to cite: Kanyiginya, V., Twongyirwe, R., Kagoro, G., Mubiru, D., Kervyn, M., and Dewitte, O.: Understanding natural hazards in a changing landscape: A citizen science approach in Kigezi highlands, southwestern Uganda, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2024, https://doi.org/10.5194/egusphere-egu22-2024, 2022.

Human life in cities is already affected by climate change. The effects will become even more pronounced in the coming years and decades. Next-generation of city climate services is necessary for adapting infrastructures and the management of services of cities to climate change. These services are based on advanced weather forecast models and the access to diverse data. It is essential to keep in mind that each citizen is a unique individual with their own peculiarities, preferences, and behaviors. The base for our approach is the individual specific exposure, which considers that people perceive the same conditions differently in terms of their well-being. Individual specific exposure can be defined as the sum of all environmental conditions that affect humans during a given period of time, in a specific location, and in a specific context. Thereby, measurable abiotic parameters such as temperature, humidity, wind speed, pollution and noise are used to characterize the environmental conditions. Additional information regarding green spaces, trees, parks, kinds of streets and buildings, as well as available infrastructures are included in the context. The recording and forecasting of environmental parameters while taking into account the context, as well as the presentation of this information in easy-to-understand and easy-to-use maps, are critical for influencing human behavior and implementing appropriate climate change adaptation measures.

We will adopt this approach within the frame of the recently started, EU-funded CityCLIM project. We aim to develop and implement approaches which will explore the potential of citizen science in terms of current and historical data collecting, data quality assessment and evaluation of data products.  In addition, our approach will also provide strategies for individual climate data use, and the derivation and evaluation of climate change adaptation actions in cities.

In a first step we need to define and to characterize the different potential stakeholder groups involved in citizen science data collection. Citizen science offers approaches that consider citizens as both  organized target groups (e.g., engaged companies, schools) and individual persons (e.g. hobby scientists). An important point to be investigated is the motivation of citizen science stakehoder groups to sustainably collect data and make it available to science and reward them accordingly. For that purpose, strategic tools, such as value proposition canvas analysis, will be applied to taylor the science-to-business and the science-to-customer communications and offers in terms of the individual needs.

How to cite: Dietrich, P., Ködel, U., Schütze, S., Schmidt, F., Schütze, F., Bonn, A., Herrmann, T., and Schütze, C.: Possible Contributions of Citizen Science in the Development of the Next Generation of City Climate Services, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2929, https://doi.org/10.5194/egusphere-egu22-2929, 2022.

Picture Pile is a flexible web-based and mobile application for ingesting imagery from satellites, orthophotos, unmanned aerial vehicles and/or geotagged photographs for rapid classification by volunteers. Since 2014, there have been 16 different crowdsourcing campaigns run with Picture Pile, which has involved more than 4000 volunteers who have classified around 11.5 million images. Picture Pile is based on a simple mechanic in which users view an image and then answer a question, e.g., do you see oil palm, with a simple yes, no or maybe answer by swiping the image to the right, left or downwards, respectively. More recently, Picture Pile has been modified to classify data into categories (e.g., crop types) as well as continuous variables (e.g., degree of wealth) so that additional types of data can be collected.

The Picture Pile campaigns have covered a range of domains from classification of deforestation to building damage to different types of land cover, with crop type identification as the latest ongoing campaign through the Earth Challenge network. Hence, Picture Pile can be used for many different types of applications that need image classifications, e.g., as reference data for training remote sensing algorithms, validation of remotely sensed products or training data of computer vision algorithms. Picture Pile also has potential for monitoring some of the indicators of the United Nations Sustainable Development Goals (SDGs). The Picture Pile Platform is the next generation of the Picture Pile application, which will allow any user to create their own ‘piles’ of imagery and run their own campaigns using the system. In addition to providing an overview of Picture Pile, including some examples of relevance to SDG monitoring, this presentation will provide an overview of the current status of the Picture Pile Platform along with the data sharing model, the machine learning component and the vision for how the platform will function operationally to aid environmental monitoring.

How to cite: Sturn, T., See, L., Fritz, S., Karanam, S., and McCallum, I.: Extending Rapid Image Classification with the Picture Pile Platform for Citizen Science, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4168, https://doi.org/10.5194/egusphere-egu22-4168, 2022.

Last year, the Institute for Soil Sciences, Centre for Agricultural Research launched Hungary's first citizen science project with the aim to obtain information on the biological activity of soils using a simple estimation procedure. With the help of social media, the reactions on the call for applications were received from nearly 2000 locations. 

In the Hungarian version of the international Soil your Undies programme, standardized cotton underwear was posted to the participants with a step-by-step tutorial, who buried their underwear for about 60 days, from mid of May until July in 2021, at a depth of about 20-25 cm. After the excavation, the participants took one digital image of the underwear and recorded the geographical coordinates, which were  uploaded to a GoogleForms interface together with several basic information related to the location and the user (type of cultivation, demographic data etc.).

By analysing digital photos of the excavated undies made by volunteers, we obtained information on the level to which cotton material had decomposed in certain areas and under different types of cultivation. Around 40% of the participants buried the underwear in garden, 21% in grassland, 15% in orchard, 12% in arable land, 5% in vineyard and 4% in forest (for 3% no landuse data was provided).

The images were first processed using Fococlipping and Photoroom softwares for background removing and then percentage of cotton material remaining was estimated based on the pixels by using R Studio ‘raster package’.

The countrywide collected biological activity data from nearly 1200 sites were statistically evaluated by spatially aggregating the data both for physiographical and administrative units. The results have been published on various platforms (Facebook, Instagram, specific web site etc.), and a feedback is also given directly to the volunteers.

According to the experiments the first citizen science programme proved to be successful. 

Acknowledgment: Our research was supported by the Hungarian National Research, Development and Innovation Office (NKFIH; K-131820)

Keywords: citizen science; soil life; soil health; biological activity; soil properties

How to cite: Árvai, M., László, P., Takáts, T., Kovács, Z. A., Takács, K., Mészaros, J., and Pásztor, L.: Life in undies – Preliminary results of a citizen science data collection targeting soil health assessement in Hungary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5094, https://doi.org/10.5194/egusphere-egu22-5094, 2022.

Citizen science is often heavily dependent on software tools that allow members of the general population to collect, view and submit environmental data to a common database. While several such software platforms exist, these often require expert knowledge to set up and maintain, and server and data hosting costs can become quite costly in the long term, especially if a project is successful in attracting many users and data submissions. In the context of time-limited project funding, these limitations can pose serious obstacles to the long-term sustainability of citizen science projects as well as their ownership by the community.

One the other hand, distributed database systems (such as Qri and Constellation) dispense with the need for a centralised server and instead rely on the devices (smartphone or computer) of the users themselves to store and transmit community-generated data. This new approach leads to the counterintuitive result that distributed systems, contrarily to centralised ones, become more robust and offer better availability and response times as the size of the user pool grows. In addition, since data is stored by users’ own devices, distributed systems offer interesting potential for strengthening communities’ ownership over their own environmental data (data sovereignty). This presentation will discuss the potential of distributed database systems to address the current technological limitations of centralised systems for open data and citizen science-led data collection efforts and will give examples of use cases with currently available distributed database software platforms.

How to cite: Malard-Adam, J., Harms, J., and Medema, W.: Distributed databases for citizen science, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5147, https://doi.org/10.5194/egusphere-egu22-5147, 2022.

During the last decades, countless seismic sensors have been deployed throughout the planet by different countries and institutions. In recent years, it has been possible to manufacture low-cost MEMS accelerometers thanks to nanotechnology and large-scale development. These devices can be easily configured and accurately synchronized by GPS. Customizable microcontrollers like Arduino or RaspBerryPI can be used to develop low-cost seismic stations capable of local data storage and real-time data transfer. Such stations have a sufficient signal quality to be used for complementing conventional seismic networks.

In recent years Instituto Volcanológico de Canarias (INVOLCAN) has developed a proprietary low-cost seismic station to implement the Canary Islands School Seismic Network (Red Sísmica Escolar Canaria - RESECAN) with multiple objectives:

• supporting the teaching of geosciences.
• promoting the scientific vocation.
• strengthening the resilience of the local communities by improving awareness toward volcanism and the associated hazards.
• Densifying the existing seismic networks.

On Sept. 19^th 2021, a volcanic eruption started on the Cumbre Vieja volcano in La Palma. The eruption was proceeded and accompanied by thousands of earthquakes, many of them felt with intensities up to V MCS. Exploiting the attention drawn by the eruption, INVOLCAN started the deployment of low-cost seismic stations in La Palma in educational centres. In this preliminary phase, we selected five educational centres on the island.

The project's objective is to create and distribute low-cost stations in various educational institutions in La Palma and later on the whole Canary Islands Archipelago, supplementing them with educational material on the topics of seismology and volcanology. Each school will be able to access the data of its station, as well as those collected by other centres, being able to locate some of the recorded earthquakes. The data recorded by RESECAN will also be integrated into the broadband seismic network operated by INVOLCAN (Red Sísmica Canaria, C7). RESECAN will be an instrument of scientific utility capable of contributing effectively to the volcano monitoring of the Canary Islands, reinforcing its resilience with respect to future volcanic emergencies.

How to cite: García-Hernández, R., Barrancos, J., D'Auria, L., Domínguez, V., Montalvo, A., and Pérez, N.: RESECAN: citizen-driven seismology on an active volcano (Cumbre Vieja, La Palma Island, Canaries), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5571, https://doi.org/10.5194/egusphere-egu22-5571, 2022.

Only a few of the increasing number of citizen science projects set out to determine the projects impact on diverse learning outcomes of citizen scientists. However, besides pure completion of project activities and data collection, measurable benefits as individual learning outcomes (ILOs) (Phillips et al. 2014) should reward voluntary work.

Within the citizen science project „TeaTime4Schools“, Austrian students in the range of 13 to 18 years collected data as a group activity in a teacher guided school context; tea bags were buried into soil to investigate litter decomposition. In an online questionnaire a set of selected scales of ILOs (Phillips et al. 2014, Keleman-Finan et al. 2018, Wilde et al. 2009) were applied to test those ILOs of students who participated in TeaTime4Schools. Several indicators (scales for project-related response, interest in science, interest in soil, environmental activism, and self-efficacy) were specifically tailored from these evaluation frameworks to measure four main learning outcomes: interest, motivation, behavior, self-efficacy. In total, 106 valid replies of students were analyzed. In addition, 21 teachers who participated in TeaTime4Schools, answered a separate online questionnaire that directly asked about quality and liking of methods used in the project based on suggested scales about learning tasks of University College for Agricultural and Environmental Education (2015), which were modified for the purpose of this study. Findings of our research will be presented.

How to cite: Wawra, A., Scheuch, M., Stürmer, B., and Sanden, T.: Analysis of individual learning outcomes of students and teachers in the citizen science project TeaTime4Schools, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6970, https://doi.org/10.5194/egusphere-egu22-6970, 2022.

Already sensitive because of its geology (seismic-tsunamic risk) and its interface between arid and temperate ecosystems, the Mediterranean Basin is being transformed by climate change and major urban pressure on resources and spaces. Lebanon concentrates on a small territory the environmental, climatic, health, social and political crises of the Middle East: shortages and degradation of surface and groundwater quality, air pollution, landscape fragmentation, destruction of ecosystems, erosion of biodiversity, telluric risks and very few mechanisms of information, prevention and protection against these vulnerabilities. Further, Lebanon is sorely lacking in environmental data at sufficient temporal and spatial scales to cover the range of key phenomena and to allow the integration of environmental issues for the country's development. This absence was sadly illustrated during the August 4th, 2020, explosion at the port of Beirut, which hindered the effective management of induced threats to protect the inhabitants. In this degraded context combined with a systemic crisis situation in Lebanon, frugal  innovation is more than an option, it is a necessity. Initiated in 2021 within the framework of the O-LIFE lebanese-french research consortium (www.o-life.org), the « Seismic and air monitoring observatory  for greater Beirut » (SMOAG) project aims at setting up a citizen observatory of the urban health of Beirut by deploying innovative, connected, low-cost, energy-efficient and robust environmental and seismological instruments. Through co-constructed web services and mobile applications with various stakeholders (citizens, NGOs, decision makers and scientists), the SMOAG citizen observatory will contribute to the information and mobilization of Lebanese citizens and managers by sharing the monitoring of key indicators associated with air quality, heat islands and building stability, essential issues for a sustainable Beirut.

The first phase of the project was dedicated to the development of a low-cost environmental sensor enabling pollution and urban weather measurements (particle matters, SO2, CO, O3, N02, solar radiation, wind speed, temperature, humidity, rainfall) and to the development of all the software infrastructure, from data acquisition to the synoptic indicators accessible via web and mobile application, while following the standards of the Sensor Web Enablement and Sensor Observation System of the OGC and to the FAIR principles (Easy to find, Accessible, Interoperable, Reusable). A website and Android/IOS applications for the restitution of data and indicators and a dashboard allowing real time access to data have been developed. Environmental and low-cost seismological stations (Raspberry Shake) have been already deployed in Beirut, most of them hosted by Lebanese citizens. These instrumental and open data access efforts were completed by participatory workshops with various stakeholders  to improve the ergonomy of the web and application interfaces and to define roadmap for the implantation of future stations, consistently with  most vulnerable populations identified by NGOs and the current knowledge on the air pollution and heat islands in Beirut.

How to cite: Cornou, C., Drapeau, L., El Bakouny, Y., Lahoud, S., Polikovitch, A., Abdallah, C., Abou Chakra, C., Afif, C., Al Bitar, A., Cartier, S., Fanice, P., Fenianos, J., Guillier, B., Khater, C., and Khoury, G. and the SMOAG Team: Seismic and air monitoring observatory for greater Beirut : a citizen observatory of the "urban health" of Beirut, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7164, https://doi.org/10.5194/egusphere-egu22-7164, 2022.

Water quality in the rivers and tributaries of the Brantas catchment (about 12.000 km²) is deteriorating due to various reasons, including rapid economic development, insufficient domestic water treatment and waste management, and industrial pollution. Various water quality parameters are at least measured on monthly basis by agencies involved in water resource development and management. However, measurements consistently demonstrate exceedance of the local water quality standards. Recent claims presented by the local Environmental Protection Agency indicate that the water quality is much more affected by the domestic sources compared to the others. In an attempt to examine this, we proposed a citizen science campaign by involving people from seven communities living close to the river, a network organisation that works on water quality monitoring, three government agencies, and students from a local university. Beginning in 2022, we kicked off our campaign by measuring with test strips for nitrate, nitrite, and phosphate on weekly basis at twelve different locations from upstream to downstream of the catchment. In the effort to provide education on water stewardship and empower citizens to participate in water quality management, preliminary results – the test strips, strategies, and challenges - will be shown.

How to cite: Pramana, R., Houser, S., Rini, D., and Ertsen, M.: Citizen science for better water quality management in the Brantas catchment, Indonesia? Preliminary results, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7323, https://doi.org/10.5194/egusphere-egu22-7323, 2022.

Available quality-checked institutional meteorological data is often not measured at locations of particular interest for observing specific small-scale and meso-scale atmospheric processes. Similarly, institutional data can be hard to obtain due to data policy restrictions. On the other hand, a lot of people are highly interested in meteorology, and they frequently deploy meteorological instruments at locations where they live. Such citizen data are often shared through public data repositories and websites with sophisticated visualization routines.  As a result, the networks of citizen meteorological stations are, in numerous areas, denser and more easily accessible than are the institutional meteorological networks.  

Several examples of publicly available citizen meteorological networks, including school networks, are explored – and their application to published high-quality scientific papers is discussed. It is shown that for the data-based analysis of specific atmospheric processes of interest, such as mesoscale convective disturbances and mesoscale atmospheric gravity waves, the best qualitative and quantitative results are often obtained using densely populated citizen networks.  

Finally, a “cheap and easy to do” project of constructing a meteorological station with a variable number of atmospheric sensors is presented. Suggestions on how to use such stations in educational and citizen science activities, and even in real-time warning systems, are given.  

How to cite: Sepic, J., Vranic, J., Aviani, I., Milanovic, D., and Burazer, M.: Citizen science - an invaluable tool for obtaining high-resolution spatial and temporal meteorological data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7916, https://doi.org/10.5194/egusphere-egu22-7916, 2022.

Among the greatest constraints to accurately monitoring and understanding climate and climate change in many locations is limited in situ observing capacity and resolution in these places. Climate behaviours along with dependent environmental and societal processes are frequently highly localized, while observing systems in the region may be separated by hundreds of kilometers and may not adequately represent conditions between them. Similarly, generating climate equity in urban regions can be hindered by an inability to resolve urban heat islands at neighborhood scales. In both cases, higher density observations are necessary for accurate condition monitoring, research, and for the calibration and validation of remote sensing products and predictive models. Coincidentally, urban neighborhoods are heavily populated and thousands of individuals visit remote locations each day for recreational purposes. Many of these individuals are concerned about climate change and are keen to contribute to climate solutions. However, there are several challenges to creating a voluntary citizen science climate observing program that addresses these opportunities. The first is that such a program has the potential for limited uptake if participants are required to volunteer their time or incur a significant cost to participate. The second is that researchers and decision-makers may be reluctant to use the collected data owing to concern over observer bias. This paper describes the on-going development and implementation by 2DegreesC.org of a technology-driven citizen science approach in which participants are equipped with low-cost automated sensors that systematically sample and communicate scientifically valid climate observations while they focus on other activities (e.g., recreation, gardening, fitness). Observations are acquired by a cloud-based system that quality controls, anonymizes, and makes them openly available. Simultaneously, individuals of all backgrounds who share a love of the outdoors become engaged in the scientific process via data-driven communication, research, and educational interactions. Because costs and training are minimized as barriers to participation, data collection is opportunistic, and the technology can be used almost anywhere, this approach is dynamically scalable with the potential for millions of participants to collect billions of new, accurate observations that integrate with and enhance existing observational network capacity.

How to cite: Shein, K.: Linking citizen scientists with technology to reduce climate data gaps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10634, https://doi.org/10.5194/egusphere-egu22-10634, 2022.

The 2019-2020 bushfire season (the Black Summer) in Australia was unprecedented in its breadth and severity as well as the disrupted resources and time dedicated to studying it.  Right after one of the most extreme fire seasons on record had hit Australia, a once-in-a-century global pandemic, COVID-19, occurred. This pandemic caused world-wide lockdowns throughout 2020 and 2021 that prevented travel and field work, thus hindering researchers from assessing damage done by the Black Summer bushfires. Early assessments show that the bushfires on Kangaroo Island, South Australia caused declines in soil nutrients and ground coverage up to 10 months post-fire, indicating higher risk of soil erosion and fire-induced land degradation at this location. In parallel to the direct impacts the Black Summer bushfires had on native vegetation and soil, the New South Wales Nature Conservation Council observed a noticeable increase in demand for fire management workshops in 2020. What was observed of fires and post-fire outcomes on soil and vegetation from the 2019-2020 bushfire season that drove so many citizens into action? In collaboration with the New South Wales Nature Conservation Council and Rural Fire Service through the Hotspots Fire Project, we will be surveying and interviewing landowners across New South Wales to collect their observations and insights regarding the Black Summer. By engaging landowners, this project aims to answer the following: within New South Wales, Australia, what impact did the 2019-2020 fire season have on a) soil health and native vegetation and b) human behaviours and perceptions of fire in the Australian landscape. The quantity of insights gained from NSW citizens will provide a broad assessment of fire impacts across multiple soil and ecosystem types, providing knowledge of the impacts of severe fires, such as those that occurred during the Black Summer, to the scientific community. Furthermore, with knowledge gained from reflections from citizens, the Hotspots Fire Project will be better able to train and support workshop participants, while expanding the coverage of workshops to improve support of landowners across the state. Data regarding fire impacts on soil, ecosystems, and communities has been collected by unknowing citizen scientists all across New South Wales, and to gain access to that data, we need only ask.

How to cite: Ondik, M., Ooi, M., and Muñoz-Rojas, M.: Insights from landowners on Australia's Black Summer bushfires: impacts on soil and vegetation, perceptions, and behaviours, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10776, https://doi.org/10.5194/egusphere-egu22-10776, 2022.

High air pollution concentration levels and increased urban heat island intensity, are amongst the most critical contemporary urban health concerns. This is the reason why various municipalities are starting to invest in extensive direct air quality and microclimate sensing networks. Through the study of these datasets it has become evident that the understanding of inter-urban environmental gradients is imperative to effectively introduce urban land-use strategies to improve the environmental conditions in the neighborhoods that suffer the most, and develop city-scale urban planning solutions for a better urban health.  However, given economic limitations or divergent political views, extensive direct sensing environmental networks have yet not been implemented in most cities. While the validity of citizen science environmental datasets is often questioned given that they rely on low-cost sensing technologies and fail to incorporate sensor calibration protocols, they can offer an alternative to municipal sensing networks if the necessary Quality Assurance / Quality Control (QA/QC) protocols are put in place.

This research has focused on the development of a QA/QC protocol for the study of urban environmental data collected by the citizen science PurpleAir initiative implemented in the Bay Area and the city of Los Angeles where over 700 purple air stations have been implemented in the last years. Following the QA/QC process the PurpleAir data was studied in combination with remote sensing datasets on land surface temperature and normalized difference vegetation index, and geospatial datasets on socio-demographic and urban fabric parameters. Through a footprint-based study, and for all PurpleAir station locations, the featured variables and the buffer sizes with higher correlations have been identified to compute the inter-urban environmental gradient predictions making use of 3 supervised machine learning models: - Regression Tree Ensemble, Support Vector Machine, and a Gaussian Process Regression.

How to cite: Llaguno-Munitxa, M., Bou-Zeid, E., Rueda, P., and Shu, X.: Citizen-science urban environmental monitoring for the development of an inter-urban environmental prediction model for the city of Los Angeles, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11765, https://doi.org/10.5194/egusphere-egu22-11765, 2022.

Routine monitoring of soil chemistry is needed for effective crop management since a poor understanding of nutrient levels affects crop yields and ultimately farmers’ livelihoods.¹ In low- and middle-income countries soil sampling is usually limited, due to required access to analytical services and high costs of portable sampling equipment.² We are developing portable and low-cost sampling and analysis tools which would enable farmers to test their own land and make informed decisions around the need for fertilizers. In this study we aimed to understand attitudes of key stakeholders towards this technology and towards collecting the data gathered on public databases which could inform decisions at government level to better manage agriculture across a country.

In Kenya, we surveyed 549 stakeholders from Murang’a and Kiambu counties, 77% men and 23% women. 17.2% of these respondent smallholder farmers were youthful farmers aged 18-35 years with 81.9% male and 18.1% female-headed farming enterprises. The survey covered current knowledge of soil nutrition, existing soil management practices, desire to sample soil in the future, attitudes towards our developed prototypes, motivation towards democratization of soil data, and willingness to pay for the technology. In Vietnam a smaller mixed methods online survey was distributed via national farming unions to 27 stakeholders, in particular engaging younger farmers with an interest in technology and innovation.

Within the Kenya cohort, only 1.5% of farmers currently test for nutrients and pH. Reasons given for not testing included a lack of knowledge about soil testing (35%), distance to testing centers (34%) and high costs (16%). However, 97% of respondents were interested in soil sampling at least once a year, particularly monitoring nitrates and phosphates. Nearly all participants, 94-99% among the males/females/youths found cost of repeated analysis of soil samples costing around USD 11-12 as affordable for their business. Regarding sharing the collecting data, 88% believed this would be beneficial, for example citing that data shared with intervention agencies and agricultural officers could help them receive relevant advice.

In Vietnam, 87% of famers did not have their soil nutrient levels tested with 62% saying they did not know how and 28% indicating prohibitive costs. Most currently relied on local knowledge and observations to improve their soil quality. 87% thought that the system we were proposing was affordable with only 6% saying they would not be interested in trialing this new technology. Regarding the soil data, respondents felt that it should be open access and available to everyone.

Our surveys confirmed the need and perceived benefit for our proposed simple-to-operate and cost-effective workflow, which would enable farmers to test soil chemistry themselves on their own land. Farmers were also found to be motivated towards sharing their soil data to get advice from government agencies. The survey results will inform our further development of low-cost, portable analytical tools for simple on-site measurements of nutrient levels within soil.

1. Dimkpa, C., et al., Sustainable Agriculture Reviews, 2017, 25, 1-43.

2. Zingore, S., et al., Better Crops, 2015, 99 (1), 24-26.

How to cite: Richardson, S., Kamau, P., Parsons, K. J., Halstead, F., Ndirangu, I., Minh, V. Q., Tri, V. P. D., Le, H., Pamme, N., and Gitaka, J.: Attitudes towards a cafetiere-style filter system and paper-based analysis pad for soil nutrition surveillance in-situ: evidence from Kenya and Vietnam, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11797, https://doi.org/10.5194/egusphere-egu22-11797, 2022.

Keywords: preconcentration, heavy metal, cafetiere, citizen science, paper-based microfluidics

Heavy-metal analysis of water samples using microfluidics paper-based analytical devices (µPAD) with colourimetric readout is of great interest due to its simplicity, affordability and potential for Citizen Science-based data collection [1]. However, this approach is limited by the relatively poor sensitivity of the colourimetric substrates, typically achieving detection within the mg L^-1 range, whereas heavy-metals exist in the environment at <μg L^-1 quantities   [2]. Preconcentration is commonly used when analyte concentration is below the analytical range, but this typically requires laboratory equipment and expert users [3]. Here, we are developing a simple method for pre-concentration of heavy metals, to be integrated with a µPAD workflow that would allow Citizen Scientists to carry out pre-concentration as well as readout on-site.

The filter mesh from an off-the-shelf cafetière (350 mL) was replaced with a custom-made bead carrier basket, laser cut in PMMA sheet featuring >500 evenly spread 100 µm diameter holes. This allowed the water sample to pass through the basket and mix efficiently with the 2.6 g ion-exchange resin beads housed within (Lewatit^® TP207, Ambersep^® M4195, Lewatit^® MonoPlus SP 112). An aqueous Ni²⁺ sample (0.3 mg L^-1, 300 mL) was placed in the cafetiere and the basket containing ion exchange material was moved up and down for 5 min to allow Ni²⁺ adsorption onto the resin. Initial investigations into elution with a safe, non-toxic eluent focused on using NaCl (5 M). These were carried out by placing the elution solution into a shallow dish and into which the the resin containing carrier basket was submerging. UV/vis spectroscopy via a colourimetric reaction with nioxime was used to monitor Ni²⁺ absorption and elution.

After 5 min of mixing it was found that Lewatit^® TP207 and Ambersep^® M4195 resins adsorbed up to 90% of the Ni²⁺ ions present in solution and the Lewatit^® MonoPlus SP 112 adsorbed up to 60%. However, the Lewatit^® MonoPlus SP 112 resin performed better for elution with NaCl. Initial studies showed up to 30% of the Ni²⁺ was eluted within only 1 min of mixing with 10 mL 5 M NaCl.

Using a cafetière as pre-concentration vessel coupled with non-hazardous reagents in the pre-concentration process allows involvement of citizen scientists in more advanced environmental monitoring activities that cannot be achieved with a simple paper-based sensor alone. Future work will investigate the user-friendliness of the design by trialling the system with volunteers and will aim to further improve the trapping and elution efficiencies.

References:

• Almeida, M., et al., Talanta, 2018, 177, 176-190.
• Lace, A., J. Cleary, Chemosens., 2021. 9, 60.
• Alahmad, W., et al.. Biosens. Bioelectron., 2021. 194, 113574.

How to cite: Sari, M., Richardson, S., Mayes, W., Lorch, M., and Pamme, N.: Method development for on-site freshwater analysis with pre-concentration of nickel via ion-exchange resins embedded in a cafetière system and paper-based analytical devices for readout, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11892, https://doi.org/10.5194/egusphere-egu22-11892, 2022.

Hurtigruten Expeditions, a member of the International Association of Antarctica Tour Operators (IAATO) and the Association of Arctic Expedition Cruise Operators (AECO) has been visiting the fragile polar environments for two decades, witnessing the effects of climate change. Tourism and the number of ships in the polar regions has grown significantly. As a stakeholder aware of the need for long-term protection of these regions, we promote safe and environmentally responsible operations, invest in the understanding and conservation of the areas we visit, and focus on the enrichment of our guests.

For the last couple of years, we have supported the scientific community by transporting researchers and their equipment to and from their study areas in polar regions and we have established collaborations with numerous scientific institutions. In parallel we developed our science program with the goal of educating our guests about the natural environments they are in, as well as to further support the scientific community by providing our ships as platforms of opportunity for spatial and temporal data collection. Participation in Citizen Science programs that complement our lecture program provides an additional education opportunity for guests to better understand the challenges the visited environment faces while contributing to filling scientific knowledge gaps in remote areas and providing data for evidence-based decision making.

We aim to continue working alongside the scientific community and developing partnerships. We believe that scientific research and monitoring in the Arctic and Antarctic can hugely benefit from the reoccurring presence of our vessels in these areas, as shown by the many projects we have supported so far. In addition, our partnership with the Polar Citizen Science Collective, a charity that facilitates interaction between scientists running Citizen Science projects and expedition tour operators, will allow the development of programs on an industry level, rather than just an operator level, increasing the availability and choice of platforms of opportunity for the scientific community.

How to cite: Meraldi, V., Morgan, T., Lynnes, A., and Grams, Y.: Collection of valuable polar data and increase in nature awareness among travellers by using Expedition Cruise Ships as platforms of opportunity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12972, https://doi.org/10.5194/egusphere-egu22-12972, 2022.

Heavy rainfall, floods and debris flow on the Rimac river watershed are recurring events that impact Peruvian people in vulnerable situations.There are few historical records, in terms of hydrometeorological variables, with sufficient temporal and spatial accuracy. As a result, Early Warning Systems (EWS) efficiency, dealing with these hazards, is critically limited.

In order to tackle this challenge, among other objectives, the Participatory Monitoring Network (Red de Monitoreo Participativo or Red MoP, in spanish) was formed: an alternative monitoring system supported by voluntary community collaboration of local population under a citizen science approach. This network collects and communicates data captured with standardized manual rain gauges (< 3USD). So far, it covers districts in the east metropolitan area of the capital city of Lima, on dense peri-urban areas, districts on the upper Rimac watershed on rural towns, and expanding to other upper watersheds as well.

Initially led by Practical Action as part of the Zurich Flood Resilience Alliance, it is now also supported by SENAMHI (National Meteorological and Hydrological Service) and INICTEL-UNI (National Telecommunications Research and Training Institute), as an activity of the National EWS Network (RNAT).

For the 2019-2022 rainfall seasons, the network has been gathering data and information from around 80 volunteers located throughout the Rimac and Chillon river watersheds (community members, local governments officers, among others): precipitation, other meteorological variables, and information regarding the occurrence of events such as floods and debris flow (locally known as huaycos). SENAMHI has provided a focalized 24h forecast for the area covered by the volunteers, experimentally combines official stations data with the network’s for spatial analysis of rainfall, and, with researchers from the University of Bristol, analyses potential uses of events gathered through this network. In order to facilitate and automatize certain processes, INICTEL-UNI developed a web-platform and a mobile application that is being piloted.

We present an analysis of events and trends gathered through this initiative (such as a debris flow occurred in 2019). Specifically, hotspots and potential uses of this sort of refined spatialized rainfall information in the dry & tropical Andes. As well, we present a qualitative analysis of volunteers’ expectations and perceptions. Finally, we also present a meteorological explanation of selected events, supporting the importance of measuring localized precipitation during the occurrence of extreme events in similar complex, physical and social contexts.

How to cite: Arestegui, M., Ordoñez, M., Cisneros, A., Madueño, G., Almeida, C., Aliaga, V., Quispe, N., Millán, C., Lavado, W., Huaman, S., and Phillips, J.: Participatory rainfall monitoring: strengthening hydrometeorological risk management and community resilience in Peru, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13115, https://doi.org/10.5194/egusphere-egu22-13115, 2022.

Remotely piloted airborne system (RPAS) based structure-from-motion (SfM) photogrammetry is a recognised tool in geomorphological applications. However, time constraints, methodological requirements and ignorance can easily compromise photogrammetric rigour in geomorphological fieldwork. Light RPAS mounted sensors often provide inherent low geometric stability and are thus typically calibrated on-the-job in a self-calibrating bundle adjustment. Solving interior (lens geometry) and exterior (position and orientation) camera parameters requires variation of sensor-object distance, view angles and surface geometry.

Deficient camera calibration can cause systematic errors resulting in final digital elevation model (DEM) deformation. The application of multi-sensor systems, common in geomorphological research, poses additional challenges. For example, the low contrast in thermal imagery of vegetated surfaces constrains image matching algorithms.

We present a pre-calibration workflow to separate sensor calibration and data acquisition that is optimized for geomorphological field studies. The approach is time-efficient (rapid simultaneous image acquisition), repeatable (permanent object), at survey scale to maintain focal distance, and on-site to avoid shocks during transport.

The presented workflow uses a stone building as a suitable 3D calibration structure (alternatively boulder or bridge) providing structural detail in visible (DJI Phantom 4 Pro) and thermal imagery (Workswell WIRIS Pro). The dataset consists of feature coordinates extracted from terrestrial laser scanner (TLS) scans (3D reference data) and imagery (2D calibration data). We process the data in the specialized software, vision measurement system (VMS) as benchmark and the widely applied commercial SfM photogrammetric software, Agisoft MetaShape (AM) as convenient alternative. Subsequently, we transfer the camera parameters to the application in an SfM photogrammetric dataset of a river environment to assess the performance of self- and pre-calibration using different image network configurations. The resulting DEMs are validated against GNSS reference points and by DEMs of difference. 

We achieved calibration accuracies below one-third (optical) and one-quarter (thermal) of a pixel. In line with the literature, our results show that self-calibration yields the smallest errors and DEM deformations using multi-scale and oblique datasets. Pre-calibration in contrast, yielded the lowest overall errors and performed best in the single-scale nadir scenario. VMS consistently performed better than AM, possibly because AM's software “black-box” is less customisable and does not allow purely marker-based calibration. Furthermore, we present findings regarding sensor stability based on a repeat survey.

We find that pre-calibration can improve photogrammetric accuracies in surveys restricted to unfavourable designs e.g. nadir-only (water refraction, sensor mount). It can facilitate the application of thermal sensors on surfaces less suited to self-calibration. Most importantly, multi-scale survey designs could potentially become redundant, thus shortening flight time or increasing possible areal coverage.

How to cite: Senn, J. A., Mills, J., Walsh, C. L., Addy, S., and Peppa, M.-V.: Assessment of sensor pre-calibration to mitigate systematic errors in SfM photogrammetric surveys, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-279, https://doi.org/10.5194/egusphere-egu22-279, 2022.

How to cite: Lynch, J., McDougall, D., and Maddock, I.: A sensitivity analysis of Rillstats for soil erosion estimates from UAV derived digital surface models., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-344, https://doi.org/10.5194/egusphere-egu22-344, 2022.

Recent advances in repeated data acquisition by UAV-borne photogrammetry and laser scanning for geoscientific monitoring extend the possibilities for analysing surface dynamics in 3D at high spatial (centimeter point spacing) and temporal (up to daily) resolution. These techniques overcome common challenges of ground-based sensing (occlusion, heterogeneous measurement distribution, limited spatial coverage) and provide a valuable additional data source for topographic change analysis between successive epochs.

We investigate point clouds derived from UAV-borne photogrammetry and laser scanning as input for change analysis. We apply and compare two state-of-the-art methods for pairwise 3D topographic change quantification. Our study site is the active rock glacier Äußeres Hochebenkar in the Eastern Austrian Alps (46° 50’ N, 11° 01’ E). Whereas point clouds derived from terrestrial laser scanning (TLS) have become a common data source for this application, point clouds derived from UAV-borne sensing techniques have emerged only in recent years and their potential for methods of 3D and 4D (3D + time) change analysis is yet to be exploited.

We perform change analysis using (1) the Multi Scale Model to Model Cloud Comparison (M3C2) algorithm [1] and (2) the correspondence-driven plane-based M3C2 [2]. Both methods have shown to provide valuable surface change information on rock glaciers when applied to successive terrestrial laser scanning point clouds of different time spans (ranging from 2 weeks to several years). The considerable value of both methods also lies in their ability to quantify the uncertainty additionally to the associated change. This allows to distinguish between significant change (quantified magnitude of change > uncertainty) and non-significant or no change (magnitude of change ≤ uncertainty) and hence enables confident analysis and geographic interpretation of change.

We will extend the application of the two methods by using point clouds derived using (1) photogrammetric techniques on UAV-based images and (2) UAV-borne laser scanning. We investigate the influence of variations in measurement distribution and density, completeness of spatial coverage and ranging uncertainty by comparing UAV-based point clouds to TLS data of the same epoch. Using TLS-TLS-based change analysis as reference, we examine the performance of the two methods with respect to their capability of quantifying surface change based on point clouds originating from different sensing techniques.

Results of this assessment can support the theoretical and practical design of future measurement set-ups. Comparing results of both methods further aids the selection of a suitable method (or combination) for change analysis in order to meet requirements e.g., regarding uncertainty of measured change or spatial coverage of the analysis. To ease usability of a broad suite of state-of-the-art methods of 3D/4D change analysis, we are implementing an open source Python library for geographic change analysis in 4D point cloud data (py4dgeo, www.uni-heidelberg.de/3dgeo-opensource). Finally, our presented study provides insights how methods for 3D and 4D change analysis should be adapted or developed in order to exploit the full potential of available close-range sensing techniques.

[1] https://doi.org/ 10.1016/j.isprsjprs.2013.04.009

[2] https://doi.org/10.1016/j.isprsjprs.2021.11.018

How to cite: Zahs, V., Winiwarter, L., Anders, K., Bremer, M., Rutzinger, M., Potůčková, M., and Höfle, B.: Evaluation of UAV-borne photogrammetry and UAV-borne laser scanning for 3D topographic change analysis of an active rock glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2513, https://doi.org/10.5194/egusphere-egu22-2513, 2022.

The main type of research material is multi-season aerial photography of the oil mining karst river basin was carried out by unmanned aerial vehicle.

Visual photo delineation revealed the consequences of mechanical transformations, some hydrocarbon inputs (bitumization) and salts (technogenic salinization) were also identified. The last processes were verified using materials from direct geochemical surveys (chemical analyses of soils, surface waters and sets of ordinary photo of sample plots).

It has been established that mechanical transformations, as a rule, is detected by the color and shape of objects. Less often, it is necessary to additionally analyze indirect photo delineation signs: shape of the shadow, configuration of the borders, traces of heavy vehicle tracks. Photo delineation signs of technogenic salinization are turbidity of water and the acquisition of a bluish-whitish color; the change of the color of the water body to green-yellow; white ground salt spots. The bituminization process is sufficiently reliably identified only in the presence of open oil spills on the surface of soil or water. Despite the difficulty of photo delineation, the use of orthophotos allows to identify 13 new sites (26 in total in the studied area) of the processes of bitumization and technogenic salinization, which had not been noted during previous large-scale field survey.

The use of orthophotos to detect the processes of bitumization and technogenic salinization is effective, especially in combination with direct field studies. Conditions for using aerial photography to identify the consequences of oil mining technogenesis: pixel resolution should be equals or more precise than 20 cm / pixel (more desirable – equals or more precise than 10 cm / pixel), snowless shooting season, lack or low level of cloud cover, relatively low forest cover percent. The spatial distribution of the identified areas of all types of technogenesis indicates a close relationship with the location of oil mining facilities.

A promising direction for the development of the research is associated with the use of multispectral imaging, the improvement of attend field surveys, as well as the expansion of the experience of aerial photography of oil fields located in other natural conditions.

The reported study was funded by Russian Foundation for Basic Research (RFBR) and Perm Territory, project number 20-45-596018.

How to cite: Sannikov, P., Khotyanovskaya, Y., and Buzmakov, S.: Applicability of aerial photography for identifying of oil mining technogenesis: mechanical transformations, bitumization, technogenic salinization, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2643, https://doi.org/10.5194/egusphere-egu22-2643, 2022.

Pyrenean glaciers have shown a marked area and thickness decrease in the last century, especially in the last decades, and currently are highly threatened by climate change. Out of the 39 glaciers existing in the Pyrenees in 1984, 23 very small glaciers remain in this mountain range, from which only four have more than 10 ha. Probably, the most emblematic glacier of these four is Aneto glacier as it is located in the North-East face of the highest summit in the Pyrenees, the Aneto peak (3404 m a.s.l.). This work presents the Aneto glacier surface reconstruction from aerial images obtained in 1981, and its comparison with the glacier surface obtained in 2021 with Unmanned Aerial Vehicles (UAV) images.

The 1981 and 2021 images have been processed with Structure from Motion (SfM) algorithms to reconstruct the Digital Surface Model (DSM) of the glacier and nearby terrain. Taking advantage of the accurate geolocation of the UAV images in 2021 (GPS with RTK/PPK surveying), the DSM obtained has a precise representation of the glacier surface. Oppositely the aerial images of 1981 lack precise geolocation and thus require a post-processing analysis. The aerial images of the '80s have been firstly geolocated with Ground Control Points (GCPs) of known coordinates within the study area (summits, crests, and rock blocks with unaltered position). After this initial geolocation, the DSM of 1981 was generated with SfM algorithms. Nevertheless, this DSM still lacks a geolocation accuracy. To allow a comparison between the 1981 and the 2021 DSMs, the glacier surface in 1981 was registered to the 2021 surface with an Iterative Close Point (ICP) routine in the surrounding area of the glacier. The technique described in this work may be applicable to other historical aerial images, which may allow studying glacier evolutions all over the world for dates without field observations.

The surface comparison generated with images that have a temporal difference of 40 years has shown the dramatic area and thickness loss of this glacier, with areas decreasing more than 68 m, and an average thickness reduction of 31.5 m. In this period, the glacier has reduced its extent by about a 60%. There is a recent acceleration in the rate of shrinkage if we compare these data with the obtained for the period 2011-2021, in which area loss reaches 15% and thickness reduction almost reaches 10 m. During the 1981-2021 period the shrinkage rate is 0.78 m thickness/year and 1.5% area/year, meanwhile, during the 2011-2021 period the shrinkage rate is 0.99 m thickness/year and 2.7% area/year.

How to cite: Vidaller, I., Revuelto, J., Izagirre, E., García, J., Rojas-Heredia, F., and López-Moreno, J. I.: Comparison of 3D surfaces from historical aerial images and UAV acquisitions to understand glacier dynamics: The Aneto glacier changes in 40 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3163, https://doi.org/10.5194/egusphere-egu22-3163, 2022.

Data on grain sizes of pebbles in gravel-bed rivers are a well-known proxy for sedimentation and transport conditions, and thus a key quantity for the understanding of a river system. Therefore, methods have been developed to quantify the size of gravels in rivers already decades ago. These methods involve time-intensive fieldwork and bear the risk of introducing sampling biases. More recently, low-cost UAV (unmanned aerial vehicle) platforms have been employed for the collection of referenced images along rivers with the aim to determine the size of grains. To this end, several methods to extract pebble size data from such UAV imagery have been proposed. Yet, despite the availability of information on the precision and accuracy of UAV surveys, a systematic analysis of the uncertainty that is introduced into the resulting grain size distribution is still missing.

Here we present the results of three close-range UAV surveys conducted along Swiss gravel-bed rivers with a consumer-grade UAV. We use these surveys to assess the dependency of grain size measurements and associated uncertainties from photogrammetric models, in turn generated from segmented UAV imagery. In particular, we assess the effect of (i) different image acquisition formats, (ii) specific survey designs, and (iii) the orthoimage format used for grain size estimates. To do so, we use uncertainty quantities from the photogrammetric model and the statistical uncertainty of the collected grain size data, calculated through a combined bootstrapping and Monte Carlo (MC) modelling approach.

First, our preliminary results suggest some influence of the image acquisition format on the photogrammetric model quality. However, different choices for UAV surveys, e.g., the inclusion of oblique camera angles, referencing strategy and survey geometry, and environmental factors, e.g., light conditions or the occurrence of vegetation and water, exert a much larger control on the model quality. Second, MC modelling of full grain size distributions with propagated UAV uncertainties shows that measured size uncertainty is at the first order controlled by counting statistics, the selected orthoimage format, and limitations of the grain size determination itself, i.e., the segmentation in images. Therefore, our results highlight that grain size data are consistent and mostly insensitive to photogrammetric model quality when the data is extracted from single, undistorted orthoimages. This is not the case for grain size data, which are extracted from orthophoto mosaics. Third, upon looking at the results in detail, they reveal that environmental factors and specific survey strategies, which contribute to the decrease of the photogrammetric model quality, also decrease the detection of grains during image segmentation. Thereby, survey conditions that result in a lower quality of the photogrammetric model also lead to a higher uncertainty in grain size data.

Generally, these results indicate that even relative imprecise and not accurate UAV imagery can yield acceptable grain size data for some applications, under the conditions of correct photogrammetric alignment and a suitable image format. Furthermore, the use of a MC modelling strategy can be employed to estimate the grain size uncertainty for any image-based method in which individual grains are measured.

How to cite: Mair, D., Do Prado, A. H., Garefalakis, P., Lechmann, A., and Schlunegger, F.: Uncertainty of grain sizes from close-range UAV imagery in gravel bars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3516, https://doi.org/10.5194/egusphere-egu22-3516, 2022.

Near-continuous time series of 3D point clouds capture local landscape dynamics at a large range of spatial and temporal scales. These data can be acquired by permanent terrestrial laser scanning (TLS) or time lapse photogrammetry, and are being used to monitor surface changes in a variety of natural scenes, including snow cover dynamics, rockfalls, soil erosion, or sand transport on beaches.

Automatic methods are required to analyze such data with thousands of point cloud epochs (acquired, e.g., hourly over several months), each representing the scene with several million 3D points. Usually, no a-priori knowledge about the timing, duration, magnitude, and spatial extent of all spatially and temporally variable change occurrences is available. Further, changes are difficult to delineate individually if they occur with spatial overlap, as for example coinciding accumulation processes. To enable fully automatic extraction of individual surface changes, we have developed the concept of 4D objects-by-change (4D-OBCs). 4D-OBCs are defined by similar change histories within the area and timespan of single surface changes. This concept makes use of the full temporal information contained in 3D time series to automatically detect the timing and duration of changes. Via spatiotemporal segmentation, individual objects are spatially delineated by considering the entire timespan of a detected change regarding a metric of time series similarity (cf. Anders et al. 2021 [1]), instead of detecting changes between pairs of epochs as with established methods.

For hourly TLS point clouds, the extraction of 4D-OBCs improved the fully automatic detection and spatial delineation of accumulation and erosion forms in beach monitoring. For a use case of snow cover monitoring, our method allowed quantifying individual change volumes more accurately by considering the timespan of changes, which occur with variable durations in the hourly 3D time series, rather than only instantaneously from one epoch to the next. The result of our time series-based method is information-rich compared to results of bitemporal change analysis, as each 4D-OBC contains the full 4D (3D + time) data of the original 3D time series with determined spatial and temporal extent.

The objective of this contribution is to present how interpretable information can be derived from resulting 4D-OBCs. This will provide new layers that are supporting subsequent geoscientific analysis of observed surface dynamics. We apply Kalman filtering (following Winiwarter et al. 2021 [2]) to model the temporal evolution of individually extracted 4D-OBCs. This allows us to extract change rates and accelerations for each point in time, and to subsequently derive further features describing the temporal properties of individual changes. We present first results of this methodological combination and newly obtained information layers which can reveal spatial and temporal patterns of change activity. For example, deriving the timing of highest change rates may be used to examine links to external environmental drivers of observed processes. Our research therefore contributes to extending the information that can be extracted about surface dynamics in natural scenes from near-continuous time series of 3D point clouds.

References:

[1] https://doi.org/10.1016/j.isprsjprs.2021.01.015

[2] https://doi.org/10.5194/esurf-2021-103

How to cite: Anders, K., Winiwarter, L., and Höfle, B.: Automatic Extraction and Characterization of Natural Surface Changes from Near-Continuous 3D Time Series using 4D Objects-By-Change and Kalman Filtering, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4225, https://doi.org/10.5194/egusphere-egu22-4225, 2022.

Ol Doinyo Lengaï (OL) in north Tanzania is the only active volcano in the world emitting natrocarbonatite lavas. This stratovolcano (2962 m a.s.l) is mostly characterized by effusive lava emissions since 1983. However, on the 4^th of September 2007, explosive events marked the beginning of a new eruptive style that lasted until April 2008. This new phase involved short-lived explosive eruptions that generated volcanic ash plumes as high as 15 km during its paroxysmal stage. This explosive activity resulted in the formation of a 300 m wide and 130 m deep crater in place of the growing lava platform that had filled the crater since 1983. Since then the effusive activity at OL resumed within the crater and has been partially filling it over the last 14 years. Due to the remote location of the volcano there is a lack of monitoring of its activity and, hence, its eruptive and morphological evolution over the last years is not well constrained (e.g., emission rates, number of vents, unstable areas). This absence of monitoring, preventing the detection of features, such as instabilities of the summit cone, could have hazard implications for the tourists regularly visiting the summit area.

In this study, we quantify the evolution of OL crater area over the last 14 years by reconstructing its topography at regular time interval. We collated several sources of optical images including Unoccupied Aircraft Systems (UAS) images, videos and ground-based pictures that have been collected over the period 2008-2021 by scientists and tourists. Those data have been sorted by year and quality in order to reconstruct the most accurate topographical models using Agisoft Metashape Pro, a software for Structure from Motion (SfM) photogrammetry, and CloudCompare a 3D point cloud processing software. This enables estimating the emitted volume of lava, the emission rate and the remaining crater volume available before crater overflow. It also allows identifying punctual events, such as hornito formation or destruction, and partial crater collapses. Our results indicate that the main lava emission area has repeatedly moved over the years within the crater floor and that OL’s effusion rate has been increasing over the last few years, with more than two times higher lava emission in the period 2019-2021 compared to 2017-2019. Assuming a similar lava effusion rate in the coming years, the crater could again be filled within the next decade leading to new lava overflows. There is thus a need for periodic assessment of the situation at OL. New cost- and time-effective photogrammetry techniques, including UAS and SfM processing, offer a solution to improve the monitoring of such remote volcanoes.

How to cite: Tournigand, P.-Y., Smets, B., Laxton, K., Dille, A., Dalton-Smith, M., Schachenmann, G., Wauthier, C., and Kervyn, M.: Morphological evolution of volcanic crater through eruptions and instabilities: The case of Ol Doinyo Lengaï since the 2007-08 eruption, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4522, https://doi.org/10.5194/egusphere-egu22-4522, 2022.

Solifluction is the slow downslope movement of soil mass due to freeze-thaw processes. It is widespread on hillslopes in Polar and Alpine regions and contributes substantially to sediment transport. As solifluction lobe movement is in the order of millimeters to centimeters per year, it is tricky to measure with a high spatial and temporal resolution and accuracy. We developed a semi-automated approach to monitor movement of three solifluction lobes with different degrees of vegetation cover along an elevational gradient between 2,170 and 2,567 m in Turtmann Valley, Swiss Alps. Subsequently, we compared movement rates and patterns with environmental factors.

• For solifluction movement monitoring, we applied a combination of the Phantom 4 Pro Plus and Phantom 4 RTK (Real Time Kinematic) drones, image co-alignment and COSI-CORR (Co-registration of Optically Sensed Images and Correlation) to track movement on orthophotos between 2017 and 2021. This drone data acquisition and co-alignment procedure enable a simple, time-saving field setup without Ground Control Points (GCPs).
• Our high co-registration accuracy enabled us to detect solifluction movement if it exceeds 5 mm with sparse vegetation cover. Dense vegetation cover limited feature tracking but detected movement rates and patterns still matched previous measurements using classical total station measurements at the lowest, mostly vegetated lobe.
• In contrast to traditional solifluction monitoring approaches using point measurements, our monitoring approach provides spatially continuous movement estimates across the complete extend of the lobe. Lobe movement rates were highest at the highest elevations between 2,560 and 2,567 m (up to 14.0 cm/yr for single years) and lowest at intermediate elevations between 2,417 and 2,427 m (up to 2.9 cm/yr for single years). We found intermediate movement rates at lowest elevations between 2,170 and 2,185 m (up to 4.9 cm/yr for single years). In general, movement had the highest rates at the solifluction lobes center and the lowest rates at the front of solifluction lobes.
• We linked observed movement patters to environmental factors possibly controlling solifluction movement, such as geomorphic properties, vegetation species and coverage, soil properties determined from electrical resistivity tomography (ERT), and soil temperature data. The least movement at the lobe front is characterized by coarse material and plant species stabilizing the risers or plant species growing here due to the stable risers. Most movement at the lobe center is characterized by fine material and no vegetation or plant species promoting movement. The soil temperature data further suggests that snow cover reduced freezing rates at solifluction lobes and potentially decreased solifluction movement at the lobe between 2,417 and 2,427 m.

This study is the first to demonstrate the use of drone-based images and a semi-automated method to reach high spatiotemporal resolutions to detect subtle movements of solifluction lobes at timescales of years at sub-centimeter resolution. This provides new insights into solifluction movement and into drivers of and factors controlling solifluction movement and lobe development. Therefore, our semi-automated approach may have a great potential to uncover the fundamental processes to understand solifluction movement.

How to cite: Harkema, M., Eichel, J., Nijland, W., de Jong, S., Draebing, D., and Kattenborn, T.: Using high-resolution topography to solve “periglacial puzzles”: A semi-automated approach to monitor solifluction movement, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4763, https://doi.org/10.5194/egusphere-egu22-4763, 2022.

River canyons are characteristic features of transient fluvial systems responding to perturbations in base level and/or sediment supply. Investigating the dynamics of canyon formation and development is challenging due to the typically long time scales and the possible experimental confounding involved. In this context, the lower portion of the Marecchia River, with a history of gravel mining on alluvial deposits resting on highly erodible (i.e., claystones and poorly consolidated sands) bedrock, offers the opportunity to set up a natural experiment and investigate the onset of canyon incision and its subsequent stages of development across five decades (1955-1993). To these ends, we evaluate decadal geomorphic changes of 10-km valley segment of the Marecchia River between Ponte Verucchio and Rimini (Northern Italy) through analysis of Digital Elevation Models derived from the application of Structure from Motion to archival aerial imagery (i.e., 1955, 1969, 1976, 1985, 1993) and from a reference-LiDAR survey (i.e. 2009), in conjunction with analysis of planimetric changes in active channel width and lateral confinement.

During the 1955-2009 period, fluvial incision led to the formation of a 6-km canyon, with average vertical incision of about 15 m (in places exceeding 25 m) and a corresponding annual knickpoint migration rate of about 100 m/yr. In volumetric terms, canyon formation and evolution has involved 6.1 10⁶ m³ (95%) of degradation and 0.29 10⁶ m³ of aggradation (5%), with a corresponding net volume loss of 5.8 10⁶ m³. As a result of canyon development, the active channel has narrowed by about 80%, and channel pattern has drastically changed from braided unconfined to single-thread tightly confined one. These processes were especially important during the 1955-1993 period. Since 1993 to the present, main channel is characterized by a general stability of the active channel width with evidences of a slight recovery through mass wasting processes within it. Local disturbance associated with ongoing canyon development have propagated and are still propagating upstream, posing immediate threat to infrastructures.

How to cite: Llena, M., Simonelli, T., and Brardinoni, F.: Rapid formation of a bedrock canyon following gravel mining in the Marecchia River, Northern Apennines., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6894, https://doi.org/10.5194/egusphere-egu22-6894, 2022.

Long-term records of glaciers are more than ever crucial to understand their response to climate change. High-quality photogrammetric products, Digital Elevation Models (DEMs) and orthophotographs from early satellites are essential, as they offer a unique high-resolution view on the historical glacial dynamics. However, obtaining and producing high-resolution datasets from historical imagery can be a challenge.

In our study, we are extending available satellite images time series using images from Soviet Era KFA-1000 satellite cameras. Each KFA-1000 has a 1000 mm objective, holding 1800 frames in its magazine. Each frame is typically 18x18 cm or 30 × 30 cm, with an 80 km swath width, providing panchromatic images. They supplement the very sparse data period between aerial images and high-resolution modern satellites, giving us high-resolution insight of Antarctica and Greenland dating from 1974 to 1994. Since these images have been largely underused, they have the potential to improve our knowledge of glaciers and open new scientific perspectives. They could help us improve models in studies regarding, for instance the frontal position, the flow-velocity (by doing feature tracking), the surface elevation or the grounding line of the glaciers, etc. With a spatial resolution up to 2 m and images recorded in stereo geometry, they offer a valuable complement to other historical satellite archives such as the declassified American KH imagery. Here, we use structure-from-motion (SfM) to reconstruct former glacier surfaces and flow of main outlet glaciers in both Antarctica and Greenland. We compare and assess the quality of the results by comparing the produced DEMs with recent high-resolution imagery from Worldview’s ArcticDEM. We combine the historical DEMs with recent satellite imagery of the ice elevation and reconstruct the comprehensive history of volume change over southeast and northeast Greenland glaciers since the 90s. Mostly lost from sight for 50 years, we are now resurrecting these highly valuable records and will make them freely available to science and the public.

How to cite: Huiban, F., Dømgaard, M., Girod, L., Millan, R., Dehecq, A., Mouginot, J., Schomacker, A., Rignot, E., and Bjørk, A.: Expanding glacier time series of Antarctica and Greenland using Soviet Era KFA-1000 satellite images, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7374, https://doi.org/10.5194/egusphere-egu22-7374, 2022.

Historical aerial imagery dating back to the mid-twentieth century offers high potential to distinguish anthropogenic impacts from natural causes of environmental change and reanalyze the long-term surface evolution from local to regional scales. However, the older portion of the imagery is often acquired in panchromatic grayscale thus making image classification a very challenging task.  This research aims to compare deep learning image colorisation methods, namely, , the Neural Style Transfer (NST) and the Cycle Generative Adversarial Network (CycleGAN), for colorizing archival images of Japanese river basins for land cover analysis. Historical monochrome images were examined with `4096 x 4096` pixels of three river basins, i.e., the Kurobe, Tenryu, and Chikugo Rivers. In the NST method, we used the transfer learning model with optimal hyperparameters that had already been fine-tuned for the river basin colorization of the archival river images (Ishii et al., 2021). As for the CycleGAN method, we trained the CycleGAN with 8000 image tiles of `256 x256` pixels to obtain the optimal hyperparameters for the river basin colorization. The image tiles used in training consisted of 10 land-use types, including paddy fields, agricultural lands, forests, wastelands, cities and villages, transportation land, rivers, lakes, coastal areas, and so forth. The training result of the CycleGAN reached an optimal model in which the root mean square error (RMSE) of colorization was 18.3 in 8-bit RGB color resolution with optimal hyperparameters of the dropout ratio (0.4), cycle consistency loss (10), and identity mapping loss (0.5). Colorization comparison of the two-deep learning methods gave us the following three findings. (i) CycleGAN requires much less training effort than the NST because the CycleGAN used an unsupervised learning algorithm. CycleGAN used 8000 images without labelling for training while the NST used 60k with labelling in transfer learning. (ii) The colorization quality of the two methods was basically the same in the evaluation stage; RMSEs in CycleGAN were 15.4 for Kurobe, 13.7 for Tenryu and 18.7 for Chikugo, while RMSE in NST were 9.9 for Kurobe, 15.8 for Tenryu, and 14.2 for Chikugo, respectively. (iii) The CycleGAN indicated much higher performance on the colorization of dull surfaces without any textual features, such as the river course in Tenryu River, than the NST. In future research work, colorized imagery by both the NST and CycleGAN will be further used for land cover classification with AI technology to investigate its role in image recognition. [Reference]: Ishii, R. et al.(2021) Colorization of archival aerial imagery using deep learning, EGU General Assembly 2021, EGU21-11925, https://doi.org/10.5194/egusphere-egu21-11925.

How to cite: Tanaka, S., Miyamoto, H., Ishii, R., and Carbonneau, P.: Comparison of deep learning methods for colorizing historical aerial imagery, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7686, https://doi.org/10.5194/egusphere-egu22-7686, 2022.

Photogrammetry and Structure-from-Motion have become widely assessed tools for geomorphological 3D reconstruction, and especially for monitoring remote and hardly accessible alpine environments. UAV-based photogrammetry enables large mountain areas to be modelled with high accuracy and limited costs. However, they still require a human intervention on-site. The use of fixed time-lapse cameras for retrieving qualitative and quantitative information on glacier flows have recently increased, as they can provide images with high temporal frequency (e.g., daily) for long-time spans, and they require minimum maintenance. However, in many cases, only one camera is employed, preventing the use of photogrammetry to compute georeferenced 3D models. This work presents a low-cost stereoscopic system composed of two time-lapse cameras for continuously and quantitatively monitoring the north-west tongue of the Belvedere Glacier (Italian Alps), by using a photogrammetric approach. Each monitoring station includes a DSLR camera, an Arduino microcontroller for camera triggering, and a Raspberry Pi Zero with a SIM card to send images to a remote server through GSM network. The instrumentation is enclosed in waterproof cases and mounted on tripods, anchored on big and stable rocks along the glacier moraines. The acquisition of a defined number of images and the timing can be arbitrary scheduled, e.g., 2 images per day acquired by each camera, around noon. A set of ground control points is materialized on stable rocks along the moraines and measured with topographic-grade GNSS receivers at the first epoch to orient stereo-pairs of images. From daily stereo-pairs, 3D models are computed with the commercial Structure from Motion software package Agisoft Metashape, and they can be used to detect morphological changes in the glacier tongue, as well as to compute daily glacier velocities. The work is currently focused on improving the orientation of stereo-pairs: the use of computer vision algorithms is under study to automatize the process and increase the robustness of consecutive orientation of stereo-images, e.g., by including images coming from different epochs in the same bundle block adjustment and dividing them afterwards for dense 3D reconstruction. Change detection can be then computed from 3D point clouds by using M3C2 algorithms. Although the stereoscopic system is already installed on the Belvedere Glacier and it is properly taking daily images of the glacier tongue, the processing workflow of stereo-pairs needs to be tuned and automatized to enable high-accurate continuous 3D photogrammetric monitoring of an alpine glacier, computing short-term and infra-seasonal ice volume variations and velocities, as well as detecting icefalls.

How to cite: Ioli, F., Bianchi, A., Cina, A., De Michele, C., and Pinto, L.: Time-lapse stereo-cameras and photogrammetry for continuous 3D monitoring of an alpine glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7967, https://doi.org/10.5194/egusphere-egu22-7967, 2022.

Historical aerial photographs captured since the early 1900s and spy satellite photographs from the 1960s onwards have long been used for military, civil, and research purposes in natural sciences. These historical photographs have the unequalled potential for documenting and quantifying past environmental changes caused by anthropogenic and natural factors.

The increasing availability of historical photographs as digitized/scanned images, together with the advances in digital photogrammetry, have heightened the interest in these data in the scientific community for reconstructing long-term surface evolution from local to regional scale.

However, despite the available volume of historical images, their full potential is not yet widely exploited. Currently, there is a lack of knowledge of the types of information that can be derived, their availability over the globe, and their applications in geoscience. There are no standardized photogrammetric workflows to automatically generate 3D (three-dimensional) products, in the form of point clouds and digital elevation models from stereo images (i.e. images capturing the same scenery from at least two positions), as well as 2D products like orthophotos. Furthermore, influences on the quality and the accuracy of the products are not fully understood as they vary according to the image quality (e.g. photograph damage or scanning properties), the availability of calibration information (e.g. focal length or fiducial marks), and data acquisition (e.g. flying height or image overlap).

We reviewed many articles published in peer reviewed journals from 2010 to 2021 that explore the potential of historical images, covering both photogrammetric reconstruction techniques (methodological papers) and the interpretation of 2D and 3D changes in the past (application papers) in different geoscience disciplines such as geomorphology, cryosphere, volcanology, bio-geosciences, geology and archaeology. We present an overview of these published studies and a summary of available image archives. In addition, we compare the main methods used to process historical aerial and satellite images, highlighting new approaches. Finally, we provide our advice on image processing and accuracy assessment.

How to cite: Ressl, C., Dehecq, A., Dewez, T., Elias, M., Eltner, A., Girod, L., McNabb, R., and Piermattei, L.: Review on the processing and application of historical aerial and satellite spy images in geosciences, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8738, https://doi.org/10.5194/egusphere-egu22-8738, 2022.

The thermal regime of permafrost, as well as the retreat of sea ice, influence coastal erosion in Arctic environments. Warming permafrost temperatures might lead to enhanced instabilities, while shorter periods of sea ice expose coastal cliffs to waves and tides for longer periods. Although most studies focus on erosion rates in ice-rich permafrost, coastal cliffs and their permafrost thermal regime are still poorly understood.

In this study, we investigate the long-term evolution of the coastline along Brøgger Peninsula (~30 km2), Svalbard. Based on high-resolution aerial orthophotos and, when available, digital elevation model (DEMs) we automatically derive the coastline from 1936 (Geyman et al., 2021), 1970, 1990, 2011 and 2021. Therefore, we quantified coastal erosion rates along the coastal cliffs over the last 85 years. Due to their high spatial resolution and accuracy, the two DEMs from 1970 and 2021 are used to calculate the erosion volumes within this time. Elevation data and coastline mapping from 2021 is validated with dGPS measurements from August 2021 along three transects of the coastline. In addition, we measured surface temperature of the coastal bedrock from September 2020 to August 2021.

Our preliminary results show erosion rates along the coastal cliffs of Brøgger Peninsula. Uncertainties remain due to mapping issues, which include resolution of aerial images and DEMs, and shadow effects. Overall, historical aerial images combined with recent data provide insight into coastal evolution in an Arctic environment where permafrost temperatures are close to the thaw threshold and might become prone to failure in future.

Geyman, E., van Pelt, W., Maloof, A., Aas, H. F., & Kohler, J. (2021). 1936/1938 DEM of Svalbard [Data set]. Norwegian Polar Institute. https://doi.org/10.21334/npolar.2021.f6afca5c

How to cite: Aga, J., Piermattei, L., Girod, L., and Westermann, S.: Coastal erosion dynamics of high-Arctic rock walls: insights from historical to recent orthoimages and DEMs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9799, https://doi.org/10.5194/egusphere-egu22-9799, 2022.

Pattern recognition remains a complex endeavour for ‘structure/function’ approaches to ecosystem functioning. It is particularly challenging in dryland environments where spatial heterogeneity is the inherent functional trait related with overland flow redistribution processes. Within this context, the concept of Soil Surface Components (SSCs) emerged, representing Very-High-Resolution (VHR) hydrogeomorphic response units. SSCs are abstraction entities where spatial patterns of the soil surface and erosional functional processes are linked, according to a large pool of experimental evidence.  

Τhis abstraction complexity, particularly in the abiotic domain, has  so far mandated the use of on-screen visual photointerpretation for the mapping of SSCs, thus limiting the extent of the study cases and their potential for providing answers to the ongoing research discourse. Although significant advances have been achieved with regards to the VHR mapping of vegetation traits with either shallow or deep machine learning algorithms, mapping the full range of SSCs requires bridging the existing gap related with the abiotic domain.

The current confluence of technical advances in: (i) Unoccupied Aerial Systems (UAS), for VHR image acquisition and high geometric accuracy; (2) photogrammetric image processing (e.g. Structure from Motion, SfM), for accurately adding the third dimension, and (3) Deep Learning (DL) architectures that consider the spatial context (i.e. Convolutional Neural Networks, CNN), offers an unprecedented opportunity for achieving the pattern recognition quality required for the automated mapping of SSCs.

We decompose this complex issue with a stepwise approach in an attempt to optimise protocols across all stages of the entire process. For the initial step of image acquisition, we focus on the design of optimal UAS flight parameters, particularly with regards to flight height and image resolution, as this relates to the scale of the analysis: a critical issue for hillslope and catchment scale surveys. At the core of the methodological framework, we then approach the challenge of mapping the patchy mosaic of SSCs as a hierarchical image segmentation problem, decomposed into classification (i.e. discrete) and regression (i.e. continuous fields) tasks, required for dealing with the biotic (e.g. vegetation) and abiotic (e.g. fractional cover of rock fragments) domains, respectively.

Our pilot study area is a hillslope transect near Benidorm, a representative case in semi-arid environment of SE Spain. In this area, the mapping of SSCs was previously undertaken via visual image interpretation. We obtain satisfactory results that allow for the differentiation of plant physiognomies (i.e. annual herbaceous, shrubs, perennial tussock grass and trees). Regarding the abiotic SSCs, in addition to the identification of rock outcrops, we are also able to quantify the fractional cover of rock fragments (RF): an improvement to the visual photointerpretation of only three intervals of RF coverage. A number of challenges remain, such as the position of RF and the transferability of our methodological framework to sites with different lithological and climatological properties.

How to cite: Arnau-Rosalén, E., Pons-Crespo, R., Marqués-Mateu, Á., López-Carratalá, J., Korkofigkas, A., Karantzalos, K., Calvo-Cases, A., and Symeonakis, E.: Automated mapping of Soil Surface Components (SSCs) in highly heterogeneous environments with Unoccupied Aerial Systems (UAS) and Deep Learning: working towards an optimised workflow, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10060, https://doi.org/10.5194/egusphere-egu22-10060, 2022.

Mountain glaciers are responding in concert to a warming global climate over the past century. However, on interannual to decadal time scales, glaciers show temporally non-linear dynamics and spatially heterogeneous response, as a function of regional climate forcing and local geometry. Deriving long-term geodetic glacier change measurements from historical aerial photography can inform efforts to understand and project future response. 

We present interannual to decadal glacier and geomorphic change measurements at multiple sites across Western North America from the 1950s until present. Glacierized study sites differ in terms of glacial geometry and climatology, from continental mountains (e.g., Glacier National Park) to maritime stratovolcanoes (e.g., Mt. Rainier). Quantitative measurements of glacier and land surface change are obtained from Digital Elevation Models (DEMs) generated using the Historical Structure from Motion (HSfM) package. We use scanned historical images from the USGS North American Glacier Aerial Photography (NAGAP) archive and other aerial photography campaigns from the USGS EROS Aerial Photo Single Frames archive. 

The automated HSfM processing pipeline can derive high-resolution (0.5-2.0 m) DEMs and orthomosaics from scanned historical aerial photographs, without manual ground control point selection. We apply a multi-temporal bundle adjustment process using all images for a given site to refine both extrinsic and intrinsic camera model parameters, prior to generating DEMs for each acquisition date. All historical DEMs are co-registered to modern reference DEMs from airborne lidar, commercial satellite stereo or global elevation basemaps. The co-registration routine uses a multi-stage Iterative Closest Point (ICP) approach to achieve high relative alignment accuracy amongst the historical DEMs, regardless of reference DEM source. 

We examine the impact of regional climate forcing on glacier elevation change and dynamics using downscaled climate reanalysis products. By augmenting the record of quantitative glacier elevation change measurements and examining the relationship between climate forcing and heterogeneous glacier response patterns, we aim to improve our understanding of regional glacier mass change across multiple temporal scales, as well as inform management decisions impacting downstream water resources, ecosystem preservation, and geohazard risks.

How to cite: Knuth, F., Shean, D., McNeil, C., Schwat, E., and Bhushan, S.: Historical Structure From Motion (HSfM): An automated historical aerial photography processing pipeline revealing non-linear and heterogeneous glacier change across Western North America, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10190, https://doi.org/10.5194/egusphere-egu22-10190, 2022.

Given the global decline in oyster reef coverage, conservation and restoration efforts are increasingly needed to maintain the ecosystem services these biogenic features offer. However, monitoring and restoration are constrained by a lack of continuous quantitative metrics to effectively assess reef health. Traditional sampling methods typically provide a limited perspective of reef status, as sampling areas are just a fraction of the total reef area. In this study, an unoccupied aircraft system collected LiDAR data over oyster reefs in Cedar Key, FL, USA to develop digital surface models (DSMs) of their 3D structure. Ground sampling was also conducted in randomly placed quadrats to enumerate the live and dead oysters within each plot. Over 20 topographic complexity metrics were derived from the DSM, allowing relationships between various geomorphometric measures and reef health to be quantified. These data informed generalized additive models that explained up to 80% of the deviation of live to dead oyster ratios in the quadrats. While topographic complexity has been associated with reef health in the past, this process quantifies the relationships and indicates what metrics can be relied on to efficiently monitor intertidal oyster reefs using DSMs. The models can also inform restoration efforts on which surface characteristics are best to replicate when building restored reefs.  

How to cite: Espriella, M. C., Lecours, V., Lassiter, H. A., and Wilkinson, B.: Using UAS-based LiDAR data to quantify oyster reef structural characteristics for temporal monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10513, https://doi.org/10.5194/egusphere-egu22-10513, 2022.

The USGS digitized many historical photos of Antarctica which could provide useful insights into this region from before the satellite era. However, these images are merely scanned and do not contain semantic information, which makes it difficult to use or search this archive (for example to filter for cloudless images). Even though there are countless semantic segmentation methods, they are not working properly with these images. The images are only grayscale, have often a poor image quality (low contrast or newton’s rings) and do not have very distinct classes, for example snow/clouds (both white pixels) or rocks/water (both black pixels). Furthermore, especially for this archive, these images are not only top-down but can also be oblique.

We are training a machine-learning based network to apply semantic segmentation on these images even under these challenging conditions. The pixels of each image will be labelled into one of the six different classes: ice, snow, water, rocks, sky and clouds. No training data was available for these images, so that we needed to create it ourselves. The amount of training data is therefore limited due to the extensive amount of time required for labelling. With this training data, a U-Net was trained, which is a fully convolutional network that can work especially with fewer training images and still give precise results.

In its current state, this model is trained with 67 images, split in 80% training and 20% validation images. After around 6000 epochs (approx. 30h of training) the model converges and training is stopped. The model is evaluated on 8 randomly selected images that were not used during training or validation. These images contain all different classes and are challenging to segment due to quality flaws and similar looking classes. The model is able to segment the images with an accuracy of around 75%. Whereas some classes, like snow, sky, rocks and water can be recognized consistently, the classes ice and clouds are often confused with snow. However, the general semantic structure of the images can be recognized.

In order to improve the semantic segmentation, more training imagery is required to increase the variability of each class and prepare the model for more challenging scenes. This new training data will include both labelled images from the TMA archive and from other historical archives in order to increase the variability of classes even more. It should be checked if the quality of the model can be further improved by including metadata of the images as additional data sources.

How to cite: Dahle, F., Lindenbergh, R., Tanke, J., and Wouters, B.: Semantic segmentation of historical images in Antarctica with neural networks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10597, https://doi.org/10.5194/egusphere-egu22-10597, 2022.

Before modern remote sensing techniques, quantifying rock wall retreat due to rockfall events in the high alpine environment was limited to low-frequency post-event measurements for high-magnitude events. LiDAR and SFM now provide precise and accurate 3D models for computing 3D volume changes over time. Otherwise, mid- and low-sized events can remain unobserved due to the remoteness of the rockwalls and the lack of remnant evidence due to the rapid sequestration of ice in surrounding valley and cirque glaciers. To extend rockfall event measurement an initial measurement (t0) is necessary. The Mont-Blanc Massif (MBM, European Alps) High Resolution Topography Project is currently completing high-precision 3D models in the MBM using ground-based and aerial LiDAR, and drone-based structure-from-motion (SFM). In 2021, we began acquisition with initial measurements of 11 major sectors of the massif, representing about 80 km² of rock and ice slopes, between 1700m - 4810m in elevation. By choosing a study area with robust existent photographic and film archives, such as the MBM, it is possible to extend 3D models back in time for comparison with current datasets. Despite existent high-quality image archives, SFM processing is more challenging and error-prone than from contemporary images due to a lack of metadata, such as camera and lens type, precise dates of images, and the general degradation of the original material.  Despite these limitations, the use of historical-image-based SFM in combination with modern LiDAR data can allow the reconstruction of significant slopes of the MBM over several decades in order to i) obtain estimates of erosion rates, ii) to document rockfall events, and iii) to quantify the extent change and volume loss of hanging glaciers and ice aprons. We thus explore geomorphic processes in the high mountain environment in context of warming climate, as well as the limits of input data (image sets) in terms of practical output resolution.

How to cite: Uhlmann, D., Jaboyedoff, M., Derron, M.-H., Ravanel, L., Vicari, J., Wolff, C., Fei, L., Choanji, T., and Gutierrez, C.: High-resolution topography project on the rock walls of the Mont-Blanc massif to reconstruct volume change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10943, https://doi.org/10.5194/egusphere-egu22-10943, 2022.

The use of 3D point clouds has become ubiquitous in studying geomorphology. The richness of the acquired data, together with the high availability of 3D sensing technologies, enables a fast and detailed characterisation of the terrain and the entities therein. However, the key for a comprehensive study of landforms relies on detecting geomorphological features in the data. These entities are of complex forms that do not conform to closed parametric shapes. Furthermore, they appear in varying dimensions and orientations, and they are often seamlessly embedded within the topography. The large volume of the data, uneven point distribution and occluded regions present even a greater challenge for autonomous extraction. Therefore, common approaches are still rooted in utilising standard GIS tools on rasterised scans, which are sensitive to noise and interpolation methods. Schemes that investigate morphological phenomena directly from the point cloud use heuristic and localised methods that target specific landforms and cannot be generalised. Lately, machine-learning-based approaches have been introduced for the task. However, these require large training datasets, which are often unavailable in natural environments.

This work introduces a new methodology to extract 3D geomorphological entities from unstructured point clouds. Based on the level-set model, our approach does not require training datasets or labelling, requires little prior information about existing objects, and wants minor adjustments between different types of scenes. By developing the level-set function within the point cloud realm, it requires no triangulated mesh or rasterisation. As a driving force, we utilise visual saliency to focus on pertinent regions. As the estimation is performed pointwise, the proposed model is completely point-based, driven by the geometric characteristics of the surface. The result is three-dimensional entities extracted by their original points, as they were scanned in the field. We demonstrate the flexibility of the proposed model on two fundamentally different datasets. In the first scene, we extract gullies and sinkholes in an alluvial fan and are scanned by an airborne laser scanner. The second features pockets, niches and rocks in a terrestrially scanned cave. We show that the proposed method enables the simultaneous detection of various geomorphological entities, regardless of the acquisition technique. This is facilitated without prior knowledge of the scene and with no specific landform in mind. The proposed study promotes flexibility of form and provides new ways to quantitatively describe the morphological phenomena and characterise their shape, opening new avenues for further investigation.

How to cite: Arav, R., Poeppl, F., and Pfeifer, N.: Extraction of geomorphological entities from unstructured point clouds – a three-dimensional level-set-based approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11081, https://doi.org/10.5194/egusphere-egu22-11081, 2022.

Ice, Cloud, and land Elevation Satellite 2 (ICESat-2), part of NASA's Earth Observing System, is a satellite mission for measuring ice sheet elevation as well as land topography. ICESat-2 is equipped with the Advanced Topographic Laser Altimeter System (ATLAS), a spaceborne lidar that provides topography measurements of land surfaces around the globe. This study intends to utilize ICESat-2 ATL03 elevation data to identify the outdated part in Taiwan’s Digital Elevation Model (DEM). Because the update of DEM takes time and is relatively expensive to renew by airborne LiDAR, a screen of elevation change is crucial for planning the flight route. ICESat-2 has not only a dense point cloud of elevation but also a short revisit time for data collection. That is, ICESat-2 may have a chance to provide a reference for the current condition of terrain formation.

In this study, we aim to verify the 20-meter DEM from the Ministry of the Interior, Taiwan, by ICESat-2 elevation data. The goal is to find out the patches that have experienced significant changes in elevation due primarily to landslides. We select a typical landslide hillside in southern Taiwan as an example, and compare the DEM with ICESat-2 ATL03 photon-based heights before and after the occurrence of landslide events. In our preliminary results, the comparison of DEM and ICESat-2 ATL03 heights has a high degree of conformity inaccuracy (within meter level), indicating ICESat-2’s ability for DEM renewal.

How to cite: Pan, P.-C. and Tseng, K.-H.: Terrain Change Detection with ICESat-2: A Case Study of Central Mountain Range in Taiwan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12200, https://doi.org/10.5194/egusphere-egu22-12200, 2022.

The determination of the pressure and temperature (P-T) history experienced by mantle xenoliths, especially the pressure, is essential for elucidating the physicochemical layering structure of the uppermost mantle. However, the lack of continuous reactions between solid solution minerals with large volume changes in spinel-lherzolites makes it difficult to apply conventional geobarometry based on mineral chemistry. Here, elastic geobarometry (Angel et al., 2014; Angel et al., 2017), a complementary technique for determining equilibrium P-T conditions of rocks, was applied to spinel inclusions in olivine in a spinel-lherzolite xenolith.

To utilize elastic geobarometry, reliable equations of state (EoS) for the host mineral and inclusion are essential. Although the EoS for mantle olivine is well constrained by Angel et al. (2018), detailed studies on the EoS for spinel are scarce. Therefore, we firstly conducted a comprehensive review of previous studies investigating the temperature and/or pressure dependence of volume, bulk modulus, and heat capacity, and then determined the EoS for end member spinel using EoSfit7c (Milani et al., 2017).

Next, using Raman spectroscopy, we attempted to estimate the residual pressure of spinel inclusions (P_inc) trapped in olivine in a mantle xenolith from Ennokentiev, Sikhote-Alin, Far Eastern Russia (see Yamamoto et al. (2012) for the chemical composition of the sample). As a result, the peaks of the spinel inclusions were always shifted to higher wavenumbers than those of the unstrained reference spinel crystal from the same xenolith, but only E_g (~410 cm^-1) and A_1g (~750 cm^-1) peak positions could be measured with sufficient accuracy for quantitative analysis of residual pressure. When P_inc was estimated using relation between spinel peak position and pressure reported by Chopelas and Hofmeister (1991), the data obtained from the center of the inclusion showed positive P_inc from both A_1g and E_g peaks, and they agreed within error. However, it is desirable to use the A_1g peak for the calculation of P_inc because 1) the E_g peak has low Raman scattering intensity, 2) depending on the crystal orientation of the host olivine, the E_g peak of spinel could interfere with the B_3g peak of olivine, and 3) the E_g peak is expected to be sensitive to the differential stress because the P_inc calculated from the E_g peak obtained from the edge of the inclusion is unusually higher than that calculated from the A_1g peak. Since positive residual pressures were obtained from all the inclusions investigated, by combining the EoS of spinel constrained in this study and measured P_inc, spinel inclusions trapped in olivine can be expected to be a new method for estimating the depth provenance of spinel-bearing peridotite.

References

Angel et al. (2014) Am Mineral, 99, 2146-2149; Angel et al. (2017) Am Mineral, 102, 1957-1960; Angel et al. (2018) Phys Chem Miner, 45, 95-113, Chopelas and Hofmeister (1991) Phys Chem Miner, 18, 279-293; Milani et al. (2017) Am Mineral, 102, 851-859; Yamamoto et al. (2012) Tectonophysics, 554-557, 74-82.

How to cite: Hagiwara, Y., Angel, R., Gilio, M., Yamamoto, J., and Alvaro, M.: Evaluation of elastic geobarometry of spinel inclusions in olivine and its application to mantle xenoliths, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-199, https://doi.org/10.5194/egusphere-egu22-199, 2022.

Copper deposits or sulfide enrichment have been found along the crust-mantle transition zones in ophiolites and along the oceanic Moho. However, scarcity of suitable exposures limits our knowledge on the migration of chalcophile metals across the subcontinental crust-mantle boundary. This study aims to provide new constraints on the migration of sulfide-associated chalcophile metals at the transition between the subcontinental mantle peridotites of the Balmuccia massif and lower crustal gabbronorites of the Mafic Complex (Ivrea-Verbano Zone, NW Italy).

An ~80-m-thick zone composed of interlayered pyroxenites and gabbronorites (Contact Series; CS) showing igneous contact with the mantle peridotites was sampled along the Val Sesia river, near the Isola village. We investigated a transect from the mantle peridotites (rich in pentlandite) through the CS to the lower crustal gabbronorites (rich in pyrrhotite or pyrite). The CS zone comprises three sampling sites located 0–5 m (CS1), 65–70 m, and 75–80 m from the mantle peridotites and is characterized by the along-transect Mg# variations (Mg# of 71–57). The mantle peridotites are sulfide poor (average of 0.12 vol.‰), in contrast to the CS rocks (up to 7.8 vol.‰). The enhanced sulfide abundances in mafic rocks of the CS correlate with higher S, Cu, Ag, and Cd contents. This sulfide- and chalcophile-rich metal zone within the CS ends ~75 m away from the margin of mantle peridotites implying a probable thickness of the enrichment zone. Sulfides from mantle peridotites and CS1 are pyrrhotite-(troilite)-chalcopyrite-(cubanite)-pentlandite assemblages of magmatic origin, which is supported by δ³⁴S ranging from –0.6‰ to +1.8‰ (average of 0.0‰; cf., Oeser et al., 2012 – Chemical Geology).

The in-situ Fe isotope signatures of polyphasic sulfide grains from CS1 show a strong fractionation between the various phases. The δ⁵⁶Fe values of pyrrhotites are negative ranging from –0.8‰ to 0.0‰, whereas chalcopyrite exhibit positive values of 1.3–1.7‰. The mass balance calculations of the δ⁵⁶Fe for the bulk composition of the sulfide grains from CS1 show unfractionated (magmatic or mantle) values of 0.0 ± 0.2‰ (cf., Craddock et al., 2013 – EPSL).

The stagnant melts at the crust-mantle boundary extensively react with the mantle yielding enrichment in sulfides and chalcophile elements, which is known to yield enrichment in sulfides (Ciazela et al., 2018 - GCA; Patkó et al., 2021 - Lithos). However, the contact between the Balmuccia mantle peridotites and the lower continental crust of the Mafic Complex is highly heterogeneous with alternating layers of pyroxenites and gabbronorites. These layers may have formed from distinct magma batches as suggested by the along-transect Mg# variations. Therefore, the mechanism of observed enrichment in sulfides and chalcophile elements probably involves several stages of melt-peridotite and melt-pyroxenite reactions. These might explain the exceptionally large ~75-m-thick sulfide-rich horizon observed at the CS. Our results indicate that substantial chalcophile metal inventory is trapped at the CS. Assuming they behave the same at the Moho level, this would explain the relative deficit of these elements in the continental crust when compared its bulk composition to the composition of primitive mantle melts.

This research was funded by the NCN Poland (2018/31/N/ST10/02146)

How to cite: Pieterek, B., Ciążela, J., Tribuzio, R., Matusiak-Małek, M., Muszyński, A., Strauss, H., Lazarov, M., Weyer, S., Horn, I., Kuhn, T., and Nowak, I.: New constraints on the origin of metal enrichment at the crust-mantle boundary from the Ivrea-Verbano Zone, NW Italy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-328, https://doi.org/10.5194/egusphere-egu22-328, 2022.

Holes CM1A and CM2B of the International Continental Scientific Drilling Program (ICDP) Oman Drilling Project (OmanDP, https://www.omandrilling.ac.uk/)  drilled  through  the Moho  Transition  Zone  (MTZ).  CM1A is composed  of layered gabbro (0–160 meters below surface, mbs), dunite (160–310 mbs), and harzburgites (310–405 mbs), whereas CM2B contains dunite (20–120 mbs) and harzburgites (120–300 mbs). The drillholes provided an unprecedented opportunity to study the behavior of metals in the MTZ, where arriving primitive MORB melts  extensively  react  with  the  mantle.  Here,  melts, typically  enriched  with  sulfur and  chalcophile  elements,  are supposed to enrich the mantle and lower crust with sulfides (Gonzalez-Jimenez et al., 2020 – Ore Geol. Rev.; Ciążela et al., 2018 - GCA).          

            Modal sulfide content increases downwards the gabbro sequence from ~0.004 vol.‰ to ~1.0 vol.‰ but decreases again from 0.8 vol.‰ to 0.01 vol.‰ in the lower part of the MTZ and in the harzburgite of the upper mantle. This is reflected in the S concentration increasing from 341 ± 17 ppm, 2sd (standard deviation = σ) to  832  ±  37  ppm,  2sd,  in  the  gabbro  section  and  decreasing  downwards  from  the middle part of  Moho into harzburgites from 475 ± 21, 2sd ppm to 63 ± 3 ppm, 2σ. The sulfides in olivine gabbro from MTZ are mostly (56–87% of all sulfides) pyrrhotite-pentlandite-chalcopyrite assemblages indicating the magmatic origin. Sulfides in layered gabbro sequence are consisted of similar magmatic assemblages (36-100%) with minor chalcopyrite, bornite, heazlewoodite, chalcocite, millerite, siegenite and sphalerite with secondary origin. In dunite and harzburgite sequences sulfides are exclusively hydrothermal.

Based on EMPA and LA-ICPMS measurements, Zn, Co and Cu seem to reach their maximum concentrations in magmatic sulfides from the MTZ. Although, no significant differences are observed between the Fe isotope signatures in magmatic pyrrhotites from the lower crust (–0.73 to –0.24, 2sd [‰] of δ⁵⁶Fe) and the MTZ (–0.73 to –0.53, [‰] of δ⁵⁶Fe), we found different δ⁵⁶Fe for pyrrhotite (–0.24‰) and chalcopyrite +0.36‰ within the same sulfide grain. The bulk signature of δ⁵⁶Fe for this grain is –0,12‰ being in accordance with the mass balance calculated δ⁵⁶Fe 0.025‰ ± 0.025‰ of the mantle (Craddock et al., 2013 – Earth Planet. Sci. Lett).

            The  enrichment in sulfides and selected metals (Zn, Co, Cu) towards the  MTZ  might  result  from  melt-mantle  reaction  as  we  proposed previously for the slow-spread oceanic lithosphere based on the Kane Megamullion Ocean Core Complex (Ciążela et al., 2018 - GCA).  In the CM1A/2B ultramafic rocks: dunites and harzburgites, most sulfides are, however, secondary, formed by the same secondary fluids which caused the pervasive serpentinization. To verify whether these sulfides replaced the primary magmatic sulfides or were brought from late-stage seawater-derived fluids, we plan to measure sulfur in whole-rocks and in situ and more iron isotopes in sulfides in situ. Preliminary δ⁵⁶Fe signature isotope data give us evidence for magmatic origin of the sulfides from upper part of the MTZ section.

How to cite: Marciniak, D., Jakub, C., Ana, J., Bartosz, P., Jürgen, K., Harald, S., Marina, L., Ingo, H., Ewa, S., Marta, P., and Konrad, B.: Metal migration and ore minerals across the crust-mantle transition zone (Oman DP ICDP holes CM1A, CM2B), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-517, https://doi.org/10.5194/egusphere-egu22-517, 2022.

In the Alpine orogen of the north Aegean region, the eastern Rhodope Zone consists of widespread high-grade metamorphic basement exposed in Bulgaria and Greece. In this high-grade basement, the lithologically variegated upper unit contains meta-ultramafic bodies, which are considered as dismembered Precambrian meta-ophiolite association (Kozhoukharova 1984). In the same unit, the voluminously predominant amphibolites, having mafic igneous precursors of boninitic-tholeiitic affinity, are in turn considered of Precambrian-Paleozoic island arc origin (Haydoutov et al. 2004), or part of the amphibolites of Ordovician age have back-arc origin (Bonev et al. 2013). The upper unit, together with the overlying Circum-Rhodope belt Jurassic ophiolite, constitutes the hanging wall of the Eocene extensional system consisting of meta-granitoids with Carboniferous protoliths in the footwall. Here, we report on the geochemistry of the amphibolites from the upper unit in Bulgaria and Greece, and discuss their composition and tectonic setting, which might shed a light on the mid-late Paleozoic-early Mesozoic tectonic architecture of the region.

The amphibolites occur intercalated with para- and ortho-metamorphic lithologies within the upper unit. Texturally, they are represented mainly by massive or banded amphibolite and garnet-bearing amphibolite. The bulk mineral assemblage contains amphibole and plagioclase ± quartz ± garnet ± epidote-clinozoisite ± chlorite ± sphene ± rutile, which resulted from the main metamorphic overprint in amphibolite-facies and variable retrogression to greenschist-facies. The meta-mafic rocks cover the range of basalt to andesite composition, with elevated MgO, variable alkali and low-K contents, having mainly tholeiitic to weak calc-alkaline affinity. The range of TiO₂ defines two groups of high-Ti (>1%) and low-Ti (<1%) meta-mafic rocks. Mostly flat to slightly LREE-depleted chondrite-normalized patterns characterize the high-Ti group, which overlaps N-MORB and E-MORB compositions. The low-Ti group exhibits pronounced LREE-depleted and fractionated REE patterns, rarely U-shaped boninitic-like pattern. N-MORB-normalized trace element profiles define high LILE/HFSE ratios, moderate to strong HFSE and HREE depletion of the low-Ti group, and close to N-MORB to slightly enriched HFSE-HREE trend of the high-Ti group. A negative Nb anomaly characterizes part of the low-Ti group, whereas other samples from both groups show no Nb anomalies and have contents higher than N-MORB. On various trace element discrimination diagrams the majority of high-Ti group meta-mafic rocks display clear MORB affinity and few samples plot in the WPB field of oceanic island tholeiites, whereas low-Ti meta-mafic rocks show island arc tholeiite (IAT) affinity or have transitional MORB/IAT signature. 

The compositional diversity of the meta-mafic rocks from the upper unit with MORB, transitional MORB/IAT and IAT affinity, in turn call for the origin of the protoliths in a paired ocean ridge-island arc environment, and thus could hints their supra-subduction zone origin in an island arc/back-arc setting.

References

Bonev, N., Ovtcharova-Schaltegger, M., Moritz, R., Marchev, P., Ulianov, A. 2013. Geod Acta 26, 3-4, 207-229.

Haydoutov, I., Kolcheva, K., Daieva, L., Savov, I., Carrigan, Ch.  2004. Ofioliti, 29, 2, 145-157.

Kozhoukharova, E. 1984. Geologica Balc., 14, 4, 9-36.

Acknowledgements: The study was supported by the NSF Bulgaria KP-06-N54/5 contract.

How to cite: Bonev, N., Dotseva, Z., and Filipov, P.: Geochemistry and tectonic significance of meta-ophiolitic mafic rocks in the high-grade metamorphic basement of the eastern Rhodope Zone, Bulgaria-Greece, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1863, https://doi.org/10.5194/egusphere-egu22-1863, 2022.

The Wum maar is located in the Oku Volcanic group, part of continental sector of the Cameroon Volcanic Line (CVL) in west Africa, which consists of volcanoes active from Eocene to recent. The continental part of the CVL is located on the metamorphic-igneous basement of the Neoproterozoic Central African Orogenic Belt (CAOB), which originated during Gondwana assembly. Some of the CVL lavas contain spinel-facies peridotite and pyroxenite xenoliths giving insight into the mantle lithosphere underlying the CAOB.

We studied xenolith suite (19 xenoliths) from the Wum maar, comprising 14 lherzolites and 5 websterites. The half of lherzolites (7) consist of minerals with fertile composition (olivine Fo₈₉, orthopyroxene Al 0.16-0.19 atoms per formula unit, clinopyroxene Al 0.28-0.31 a pfu, spinel Cr# 0.08-0.13). Clinopyroxene is REE-depleted and has ⁸⁷Sr/⁸⁶Sr ratios of 0.7017-0.7021. A reconnaissance study of crystal preferred orientation (CPO) by EBSD shows that at least in part of the rocks the clinopyroxene fabric is very weak, suggesting that its crystallization post-dates the primary deformation event recorded by the olivine-orthopyroxene framework. A smaller part of lherzolites (5) contains clinopyroxene the CPO of which fits that of the olivine-orthopyroxene framework, is LREE-enriched and has ⁸⁷Sr/⁸⁶Sr ratios of 0.7027-0.7028. One of these lherzolites contains amphibole (pargasite), which forms aggregates and schlieren and texturally is later than olivine-pyroxene host. CPO of amphibole, ortho- and clinopyroxene is decoupled from that of olivine in that rock. Two lherzolites have slightly depleted mineral compositions (olivine Fo_90-91, orthopyroxene Al 0.15 apfu, clinopyroxene Al 0.25 a pfu, spinel Cr# 0.18).

Websterites are dominated by orthopyroxene (Al 0.20-0.21 a pfu) whereas clinopyroxene (Al 0.30-0.31) is subordinate, and is characterized by LREE-depletion and ⁸⁷Sr/⁸⁶Sr ratios of 0.7019-0.7020. Spinel occurring in websterites is aluminous (Cr# 0.04-0.06), in some samples subordinate olivine (Fo₉₀) occurs. One of the xenoliths consists of millimetric monomineral layers of pyroxenes and olivine chemically identical to those occurring in websterites.  

The mineral chemical data coupled with mineral fabrics suggest that lherzolites with LREE-depleted clinopyroxene could have originated by late crystallization caused by melt metasomatism. The metasomatic agent is probably best represented by websterites, which contain LREE-depleted clinopyroxene with similar, depleted ⁸⁷Sr/⁸⁶Sr of 0.7019-0.7020 (compare to DM value of 0.7026, Workman and Hart 2005), confirming earlier findings of refertilization of the regional lithospheric mantle by highly depleted melts (Tedonkenfack et al. 2021). The addition of amphibole was connected with recrystallization of ortho- and clinopyroxene and with significant change of its ⁸⁷Sr/⁸⁶Sr signature to more radiogenic values.

Funding. This study originated thanks to the project of Polish National Centre of Research NCN 2017/27/B/ST10/00365 to JP. The bilateral Austrian-Polish project WTZ PL 08/2018 enabled extensive microprobe work.

References:

Tedonkenfack SST, Puziewicz J, Aulbach S, Ntaflos T., Kaczmarek M-A, Matusiak-Małek M, Kukuła A, Ziobro M: Lithospheric mantle refertilization by DMM-derived melts beneath the Cameroon Volcanic Line – a case study of the Befang xenolith suite (Oku Volcanic Group, Cameroon). Contributions to Mineralogy and Petrology 176: 37.

Workman RK, Hart SR (2005) Major and trace element composition of the depleted MORB mantle (DMM). Earth and Planetary Science Letters 231: 53-72.

How to cite: Puziewicz, J., Aulbach, S., Kaczmarek, M.-A., Kukuła, A., Ntaflos, T., Matusiak-Małek, M., Tedonkenfack, S. S. T., and Ziobro-Mikrut, M.: Preliminary data on mantle xenoliths from the Wum maar, Oku Volcanic Group, Cameroon Volcanic Line (West Africa), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1865, https://doi.org/10.5194/egusphere-egu22-1865, 2022.

Sulfides hosted by peridotites from Befang (Oku Volcanic Group, Cameroon) xenolith suite can play an important role in tracking migration of strategic metals such as Au, Ag, or Cu through the subcontinental lithospheric mantle (SCLM) beneath the Central African Orogenic Belt. Most peridotites are lherzolites, which are subdivided into two main groups differing by crystallographic preferred orientation (CPO) and rare-earth element (REE) composition of clinopyroxene. Group I is characterized by light REE (LREE)-depleted clinopyroxene (re-)crystallized during percolation of metasomatic melt. Group II contains LREE-enriched clinopyroxene with the CPO representing deformation before percolation of the melt (Tedonkenfack et al., 2021). Lherzolites of group I  are interpreted to be metasomatized by MORB-like melts coming from  Depleted MORB Mantle (DMM). Peridotites of  group II are interpreted to be a protolith for the group I ones.

The sulfides form oval to slightly elongated grains enclosed usually in orthopyroxene, or rarely in clinopyroxene and olivine. They are composed of pyrrhotite (Po), pentlandite (Pn), and chalcopyrite (Ccp). Pyrrhotite is mostly predominant, whereas Pn forms exsolution lamellae in Po or massive crystals separating Po from Ccp. Chalcopyrite is present on the rims of grain or penetrates through the entire grain, occasionally containing cubanite exsolutions. The Group I lherzolites contain more sulfides (up to 0.031 vol.‰), with larger grains (range: 14−250 µm, 57 µm on average) compared to the Group II sulfides (up to 0.002 vol.‰, range: 12−45 µm, 27 µm on average respectively). Sulfides from Group I are richer in Po, and especially Ccp (Po₇₇Pn₁₂Ccp₁₁ on average) compared to Group II (Po₇₂Pn₂₃Ccp₄ on average). Ni/(Ni+Fe) in pyrrhotite from Group I (0.14–0.43) is more heterogeneous compared to group II (0.20–0.37).

Enrichment in Po and Ccp in the Befang Group I xenoliths suggests a significant role of melts in transporting sulfur and metals. Observed refertilization by DMM-derived melts may affect the chalcophile and highly siderophile metal budget of the SCLM. The degree of refertilizaton seems to depend on temperature and therefore is moderate in Befang (up to 0.031 vol.‰) with moderate temperatures of orthopyroxene-clinopyroxene equilibration (938–997°C; Tedonkenfack et al, 2021). In lower temperatures of Opx-Cpx equilibration (810–970°C), we observe higher sulfide abundances (up to 0.062 vol.‰), whereas in higher temperatures (1010–1120°C) lower sulfide abundances (up to 0.00048 vol.‰; Mazurek et al., 2021).

This study was supported by the Diamond Grant project 093/DIA/2020/49.

References

Mazurek, H., Ciazela, J., Matusiak-Małek, M., Pieterek, B., Puziewicz, J., Lazarov, M., Horn, I., Ntaflos, T.: Metal enrichment as a result of SCLM metasomatism? Insight from ultramafic xenoliths from SW Poland., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15992, https://doi.org/10.5194/egusphere-egu21-15992, 2021

Tedonkenfack SST., Puziewicz J., Aulbach S., Ntaflos T., Kaczmarek M-A., Matusiak-Małek M., Kukuła A., Ziobro M.: Lithospheric mantle refertilization by DMM-derived melts beneath the Cameroon Volcanic Line – a case study of the Befang xenolith suite (Oku Volcanic Group, Cameroon). Contributions to Mineralogy and Petrology, 176: 37.

How to cite: Mazurek, H., Matusiak-Małek, M., Ciazela, J., Pieterek, B., Puziewicz, J., and Tedonkenfack, S. S. T.: Metal enrichment in refertilized subcontinental lithospheric mantle: insight from the ultramafic xenoliths from the volcanic rocks of the Oku Volcanic Group (Cameroon), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2217, https://doi.org/10.5194/egusphere-egu22-2217, 2022.

In the upper mantle, volatiles control its composition, partial melting conditions, as well as the ascent rate of the formed melts. As consequence, volatile composition of the mantle is, in turn, recorded in the melts and, therefore, in the erupted basaltic rocks. Despite their importance, origin, budget, and fluxes of the volatiles in the upper mantle are poorly constrained. It is well known that the main input of mantle volatiles, such as carbon (C) and sulphur (S), represents components released from the subducting slab, e.g., oceanic rocks and sediments, whose have characteristic isotopic signatures. In this view, studies of isotopic ratios of volatiles of subduction-related magmatic rocks could be used to identify the chemical components released by the subducting slab metasomatizing the upper mantle. To confirm this hypothesis, we investigated the major and trace element composition, as well as the C and S elemental contents and isotopic ratios of subvolcanic and volcanic rocks of the Vardar ophiolites of North Macedonia, which represent remnants of the Mesozoic Tethyan oceanic lithosphere formed in supra-subduction zone tectonic settings.

The ophiolites were sampled at Lipkovo and Demir Kapija localities, in the northern and southern part of North Macedonia, respectively. Based on whole-rock major and trace element composition, two main groups of rocks can be distinguished: i) Group 1 rocks, which are subalkaline basalts with backarc affinity and ii) Group 2 rocks, which are calc-alkaline basalts with arc affinity. The petrogenetic modelling based on trace and Rare Earth Elements, indicates that Group 1 mantle sources were affected by limited metasomatic processes by slab-released components, in particular aqueous fluids and sediment melts, whereas the Group 2 mantle sources were strongly metasomatized by sediment melts and adakitic melts. Accordingly, the Group 1 rocks exhibit C-enriched and S-depleted isotopic signature, indicating a minor involvement of melts from the subducting sediments. On the other hand, the C-depleted and S-enriched isotopic signatures of the Group 2 rocks suggest a major involvement of melts derived from the subducting sediments rich in organic matter and sulphate phases Therefore, both geochemical and isotopic data of the subvolcanic and volcanic samples of the North Macedonia ophiolites show that the sub-arc mantle sources are more affected by slab-released fluids than those of the backarc basin, which are more distal from the trench. Thus, combining the geochemical and isotopic data of subvolcanic and volcanic samples of complex geological framework can contribute to reconstruct the geodynamic scenarios, such as that of the Vardar ophiolites in the Dinaric-Hellenic belt. In addition, this approach may be useful to better understand the global geodynamic cycles of volatiles reconstructing their origin, budget, and isotopic composition, and understand the impacts on climate and environment from local to global scale.

How to cite: Brombin, V., Barbero, E., Saccani, E., Precisvalle, N., Lepitkova, S., Milevski, I., Ristovski, I., Milcov, I., Dimov, G., Bonadiman, C., and Bianchini, G.: Basaltic rocks from the Vardar ophiolite (North Macedonia): new insights on the metasomatism of sub-arc upper mantle using geochemical and stable isotope data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3733, https://doi.org/10.5194/egusphere-egu22-3733, 2022.

Well-developed corona structures are observed and described in detail in the cumulate troctolites from Chainigund village, Kargil. The gabbro-troctolite unit is situated 5 km NW of Kargil city and consists of gabbros, troctolites, and anorthosites with doleritic dykes cross-cutting the unit at places. The host gabbros are fresh and display both fine and coarse-grained varieties. Troctolites occur as pods and veins within the gabbro and are composed of plagioclase (77-80 vol%), olivine (10-16 vol%), pleonaste spinel (6-8 vol%), amphiboles (2 -3 vol%) and opaques (0.5-2vol %). Both olivines and plagioclases are unzoned with spectacular coronas around the olivines (Fo 74.9-76.7) at the contact with plagioclase feldspar (An90.6-95.2). From center outwards, the discontinuous reaction series consists of the following members: Olivine, enstatitic orthopyroxene, magnesio-hornblende (Amph1) enclosed by a symplectitic rim of pargasite (Amph2) and pleonaste spinel and concludes at the plagioclase interface i.e. Ol-Opx-Amph1-Amph2-Spl-Plg. The mineral textures of the corona structure indicate formation in the presence of an interstitial fluid trapped between cumulus olivine and plagioclase. The reaction of this fluid with the olivine resulted in a rim of peritectic orthopyroxene around olivine which was subsequently replaced to form Amph 1 between the orthopyroxene and plagioclase. This is evident by the horse-shoe shaped outline and intermingling boundary shared by orthopyroxene and Amph 1. The formation of outer Amph 2 and spinel symplectite layers could be attributed to the replacement of precursor clinopyroxene and plagioclase at high temperatures (1050-1150° C ± 40° C). The Amph-Spl symplectites, presence of oxidizing conditions (magnetite and ilmenite), discontinuous reactions and local or short-range diffusion phenomena thus indicate that the corona structures are a result of metasomatic interaction of cooling magma with the previously formed minerals.

Keywords: Corona structures; troctolite gabbro; olivine- plagioclase contact; Kargil; Ladakh; India.

How to cite: Harshe, S., Jonnalagadda, M., Duraiswami, R., Benoit, M., Grégoire, M., and Karmalkar, N.: Formation of corona structures from the troctolitic gabbros of Chainigund, Kargil, Ladakh, NW Himalayas, India: Petrological implications, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3865, https://doi.org/10.5194/egusphere-egu22-3865, 2022.

The 3.5-0.5 Ma Devès volcanic field consists mainly of nepheline basanite rocks. The underlying Variscan basement is a part of the western Moldanubian Zone (an allochton of the European Variscan orogen, probably the Gondwana margin). The Devès volcanic field is located in the “southern” mantle domain of Massif Central (MC), which consists of fertile lithospheric mantle (LM) little affected by partial melting [1]. These characteristics probably resulted from intense metasomatism by melts coming from the upwelling asthenosphere [2].

Despite the rich literature dealing with the LM beneath the Devès volcanic field, some textural and geochemical details remain obscure. We studied a large xenolith population (n – 21) from Mt.Briançon (NW of the Devès volcanic field) with extensive use of EMPA and LA-ICP-MS in order to obtain a comprehensive and representative data set, and here present the preliminary findings.

The Mt.Briançon xenoliths are typically oval in shape and vary in size from 4 to 13 cm. The host rocks are tuff and scoria deposits. The xenoliths are mostly anhydrous spinel lherzolites rich in clinopyroxene (cpx, modal content up to 28%) and scarce harzburgites. One xenolith consists of olivine clinopyroxenite in contact with peridotite. The peridotites exhibit serial texture or different stages of porphyroclastic texture. In some xenoliths elongated spinel is arranged in streaks.

Most of the three major phases in the peridotites are homogenous at the grain and xenolith scale. Olivine Fo is typically 88.5-90.4% in the whole suite, and NiO content is 0.35-0.43 wt.%. Orthopyroxene (opx) has Mg# 0.89-0.91 and 0.128-0.217 atoms of Al per formula unit (apfu). Cpx has Mg# 0.88-0.91 and Al content of 0.208-0.316 apfu and spinel Cr# is highly variable in the whole suite (0.09-0.28). In contrast, one harzburgite (sample 4025) has olivine with higher Fo (~91.2%), opx with higher Mg# (~0.92) and lower Al content (0.111-0.116 apfu), cpx with Mg# ~0.92 and Al content of ~0.145 apfu, and spinel Cr# of ~0.43 and Mg# of ~0.75.

The main observed REE pattern in peridotite cpx is relatively flat Lu-Eu and slightly, but variably depleted in lighter REE. In several xenoliths cpx exhibits various REE patterns, transitioning from LREE-depleted to relatively flat or slightly LREE-enriched, while a few samples contain cpx with REE abundances moderately increasing Lu-Sm and steeply increasing towards La. The majority of peridotite opx REE patterns are moderately decreasing in Lu-Sm and more steeply decreasing towards La, whereas a less common opx pattern is similar to the previous one in Lu-Nd, but much less depleted in lighter REE. This opx coexists with LREE-rich cpx.

This study confirms that the LM beneath Mt.Briançon is mostly lherzolitic and quite fertile in terms of major elements. Ongoing work, utilizing the diversity of lithologies and pyroxene REE patterns, combined with detailed major-element and REE thermometry and with textural observations, will provide detailed insights into the microstructural, thermal and metasomatic history of the LM beneath the MC.

This study was funded by Polish National Science Centre to MZM (UMO-2018/29/N/ST10/00259).

References

[1] Uenver-Thiele L. et al. (2017). JPetrol 58, 395–422.

[2] Puziewicz J. et al. (2020). Lithos 362–363, 105467.

How to cite: Ziobro-Mikrut, M., Puziewicz, J., Aulbach, S., Ntaflos, T., and Matusiak-Małek, M.: Preliminary characteristics of mantle xenoliths from Mt. Briançon (Massif Central, France) - missing information about the lithospheric mantle beneath Devès volcanic field, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4351, https://doi.org/10.5194/egusphere-egu22-4351, 2022.

The Bakony-Balaton Highland Volcanic Field (BBHVF), where Neogene alkali basalts and their pyroclasts host a great number of upper mantle xenoliths, is situated in the western part of the Pannonian Basin. One of the barely investigated xenolith localities of the BBHVF is Mindszentkálla. In the BBHVF, most of the xenoliths have lherzolitic modal composition, however, the Mindszentkálla locality is dominated by harzburgites. In addition to the homogeneous coarse-grained harzburgite xenoliths, we collected composite and multiple composite (with more than two different domains) xenoliths that represent small-scale heterogeneities. Harzburgite, interpreted as the host rock, is crosscut by dunitic, orthopyroxenitic, apatite-bearing websteritic, and amphibole-phlogopite-bearing veins.

To understand the evolution of the conspicuously complex mantle beneath Mindszentkálla, in situ major and trace element analyses were carried out on all rock-forming minerals. The major element chemistry of silicate minerals in the harzburgite wall rock and dunite veins show lower basaltic element (Fe, Mn, Ti, Na) contents with respect to the orthopyroxenitic and websteritic veins. The rare earth elements display flat or spoon-shaped patterns in the harzburgitic clinopyroxenes, whereas the websteritic clinopyroxenes and the amphiboles of the amphibole-phlogopite vein are enriched in light rare earth elements.

The observed textural and geochemical features indicate that the Mindszentkálla xenoliths could have gone through significant mineralogical and compositional modifications in at least two events. During the first event, the lherzolitic mantle was metasomatized most likely by a silica-rich melt, which could have resulted in orthopyroxene-rich peridotitic lithology. The metasomatizing Si-rich melt is likely related to a former subduction event.

The second metasomatic event led to the formation of dunite, orthopyroxenite, apatite-bearing websterite, and amphibole-phlogopite-bearing veins. These lithologies are likely the products of interactions between volatile-enriched, asthenosphere-derived basaltic melts and the peridotite wall rock, or they represent the high-pressure crystallization of such melts. The ascent of these mafic melts may have happened shortly before the xenolith entrapment during the Neogene basaltic volcanism.

How to cite: Patkó, L., Kovács, Z., Liptai, N., Aradi, L. E., Berkesi, M., Ciazela, J., Hidas, K., Garrido, C. J., and Kovács, I. J.: Deciphering multiple metasomatism beneath Mindszentkálla (Bakony-Balaton Highland Volcanic Field, western Pannonian Basin) revealed by upper mantle peridotite xenoliths, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4679, https://doi.org/10.5194/egusphere-egu22-4679, 2022.

Keywords: magma-poor rifted margin, refertilization, partial melting, mantle-melt interaction

Although magmatic processes are of primary importance for the understanding of lithospheric breakup, many first order questions remain, such as: how, when, where and how much magma is produced during final rifting; what are the conditions and controlling processes of magma production; how does magma percolate and interact with the lithospheric mantle; and how and when does magma focus, how is it extracted and how does it interact with the extensional processes during final rifting and breakup? Answering to these questions is a prerequisite to understand lithospheric breakup and formation of a new plate boundary, which is among the least understood plate tectonic processes at present.

In this study we present preliminary petrological results from mantle rocks dredged from the SW Australia ocean-continent transition (OCT, Diamantina zone). We analyzed pyroxene and spinel compositions from these peridotites to identify mantle domains and mantle-melt reactions during rifting and breakup. The chemical composition of clinopyroxenes shows two distinct populations: a first generation characterized by low (Sm/Yb)_N ratios and no Eu anomalies, while a second generation shows interstitial textures and flat HREE patterns with a deep negative Eu anomaly. These two populations of clinopyroxenes suggest that the peridotites from the Diamantina zone record two distinct events: a first cooling event that is followed by magma infiltration. This is further supported by equilibrium temperatures calculated on the two clinopyroxene generations showing that the first population equilibrated at lower temperatures (900°C ± 30°C) corresponding to a subcontinental geotherm, while the second generation equilibrated at higher temperatures (1100°C ± 100°C), and was likely liked to the entrapment of MORB-type melts in the plagioclase stability field at low pressure (~5kbar) during magma infiltration.  

The exhumation path of the Diamantina peridotites determined in our study is similar to those of refertilized peridotites from the present-day Iberia and fossil Alpine Tethys OCTs, suggesting that refertilisation processes occurring at magma-poor rifted margins during final rifting and breakup are not dependent from the inherited nature of the subcontinental mantle.

How to cite: Ballay, M., Ulrich, M., and Manatschal, G.: Magmatic processes at rifted margins: Preliminary results from peridotites of the Diamantina zone (SW Australia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5414, https://doi.org/10.5194/egusphere-egu22-5414, 2022.

In Nd-Hf isotopic space the great majority of the global abyssal peridotites plot in the field defined by global MORBs. However, Hf isotope ratios by far exceeding those in ridge basalts, are locally observed in abyssal peridotites showing that the Earth’s mantle is more heterogeneous that inferred from ridge basalts [1]. Mantle peridotites exposed at the Doldrums Fracture Zone at the Mid Atlantic Ridge (7-8° N) reveal that such heterogeneity coexists on a kilometre-scale. Abyssal peridotites from the northern part of the Doldrums FZ domain can be grouped into residual peridotites and melt-modified (refertilized) samples [2]. New Nd-Hf isotopic data show that the refertilized peridotites preserve highly radiogenic Hf values (εHf up to 101) associated with MORB-like Nd isotopes (εNd up to 12), reflecting partial resetting of ancient highly depleted mantle by recent melt-rock interaction. On the other hand, despite a very depleted incompatible element compositions, the residual peridotites have Nd-Hf isotope ratios similar to the local MORB (εNd = 7-12 and εHf =12-19). They most likely reflect highly depleted mantle that has been entirely reset by reaction with extracted or retained melts, and hence developed with only modest incompatible element depletion until recent melting at the Mid Atlantic ridge axis, which led the strong incompatible element depleted of these peridotites. The kilometre-scale association of such isotopically heterogeneous domains suggests that the upper mantle exposed in this portion of Atlantic formed by a combination of ancient melting and melt-rock reaction processes, preceding its emplacement below the present-day Mid Atlantic ridge axis.

 [1] Stracke, A., et al., 2011. Abyssal peridotite Hf isotopes identify extreme mantle depletion. Earth and Planetary Science Letters, 308(3-4), pp.359-368. [2] Sani, C., et al., 2020. Ultra-depleted melt refertilization of mantle peridotites in a large intra-transform domain (Doldrums Fracture Zone; 7–8° N, Mid Atlantic Ridge). Lithos, 374, p.105698.

How to cite: Sani, C., Sanfilippo, A., Payve, A. A., Genske, F., and Stracke, A.: Kilometre-scale isotopic heterogeneity in abyssal peridotites from the Doldrums Fracture Zone (Mid Atlantic Ridge, 7-8ºN)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5617, https://doi.org/10.5194/egusphere-egu22-5617, 2022.

Cu-rich sulfide deposits of economic importance in ophiolites such as Troodos in Cyprus or Semail in Oman often occur along the crust-mantle transition zones (e.g. Begemann et al., 2010). Although secondary sulfides formed during serpentiniztion now prevail, the relicts of primary magmatic sulfides indicate the igneous nature of enrichment in sulfides at the oceanic Moho level. Crust-mantle transition zones in situ in the oceans are suggested to be enriched in sulfides and many chalcophile (e.g. Cu, Zn, Pb, Se, Te) metals via melt-mantle reaction (Ciazela et al., 2017; 2018). The enrichment in sulfides seems to be ubiquitous along the crust-mantle transition zone (Ciazela et al., 2018) and might be expected even at the continental Moho. This is possible as sulfides precipitate during melt-mantle reaction independently on pressure. The process seems to work at low pressures of the oceanic crust-mantle transition zone (0.1–0.2 GPa) (Marciniak et al., this session; Ciazela et al., 2018), medium pressures of the continental crust-mantle transition zone (~1.0 GPa) (Pieterek et al., this session), and in high pressures related to various melt-metasomatized mantle xenoliths (up to 2.5 GPa) (Mazurek et al., this session; Patkó et al., 2021). Metal refertilization due to variable melt-peridotite reactions at the crust-mantle transition zone and along melt channels in the upper mantle may affect the local, regional, and even global metal mass balance of the oceanic and continental lithosphere. The distribution of mantle sulfides is heterogeneous. The zones of enrichment in metals occur mostly at the crust-mantle transition or in melt-modified mantle rocks along melt channels in the upper mantle. These zones are important for subsequent ore formation in secondary processes. In the oceans, especially along slow-spreading ridges, shallow magmatic sulfide horizons are penetrated by hydrothermal fluids operating along faults to form massive sulfides on the seafloor. On land, the re-mobilization of the mantle sulfides horizons by sulfide-undersaturated melts or by buoyant CO₂ bubbles can contribute to the formation of porphyry and related epithermal mineral deposits.

Begemann F., Hauptmann A., Schmitt-Strecker S. and Weisgerber G. (2010) Lead isotope and chemical signature of copper from Oman and its occurrence in Mesopotamia and sites on the Arabian Gulf coast. Arab. Archaeol. Epigr. 21, 135–169.

Ciazela J., Dick H. J. B., Koepke J., Pieterek B., Muszynski A., Botcharnikov R. and Kuhn T. (2017) Thin crust and exposed mantle control sulfide differentiation in slow-spreading ridge magmas. Geology 45, 935–938.

Ciazela J., Koepke J., Dick H. J. B., Botcharnikov R., Muszynski A., Lazarov M., Schuth S., Pieterek B. and Kuhn T. (2018) Sulfide enrichment at an oceanic crust-mantle transition zone: Kane Megamullion (23°N, MAR). Geochim. Cosmochim. Acta 230, 155–189.

Patkó L., Ciazela J., Aradi L. E., Liptai N., Pieterek B., Berkesi M., Lazarov M., Kovács I. J., Holtz F. and Szabó C. (2021) Iron isotope and trace metal variations during mantle metasomatism: In situ study on sulfide minerals from peridotite xenoliths from Nógrád-Gömör Volcanic Field (Northern Pannonian Basin). Lithos 396–397, 106238.

How to cite: Ciazela, J., Pieterek, B., Marciniak, D., Mazurek, H., Patko, L., and Slaby, E.: Melt metasomatism and enrichment in metals in the uppermost Earth’s mantle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6901, https://doi.org/10.5194/egusphere-egu22-6901, 2022.

Uncommon Ba-Cl-rich phases including Ba-Cl micas and Cl-phosphates have been found in garnet pyroxenites as a part of the matrix or in polyphase inclusions in garnets. Polyphase inclusions are rich in carbonates (dolomite, magnesite, norshetite), phosphates (Cl-apatite, goryainovite (Ca₂PO₄Cl), monazite) and other silicates (spinel, amphibole, orthopyroxene, clinopyroxene, margarite, aspidolite, scapolite, cordierite). The inclusions appear as chains crosscutting garnet crystals and their presence is not linked with any chemical zoning in the host garnet.

The Ba-Cl-rich mica has composition ranging from Ba-rich phlogopite to chloroferrokinoshitalite and to oxykinoshitalite. The mica present in the matrix correspond to Ba-rich phlogopite with low Cl contents and occur together with celsian and low-Cl hydroxyl apatite. The mica in the polyphase inclusions ranges to almost pure chloroferrokinoshitalite and oxykinoshitalite endmembers and coexists either with Cl-apatite (Cl = 1.2 apfu) or rarely goryainovite containing up to 2.5 wt% of SrO. This is second world occurrence of goryainovite and first evidence that Ca can be partially replaced by Sr in this mineral.

Special attention was paid to the composition trends of the Ba-Cl-rich micas. These are mainly related to the XFe ratio, which correlates positively with Cl, Ba, and Al and negatively with Si and Na. Positive correlation of Cl with Ba and XFe leads to the formation of mica with composition Ba_0.95K_0.03Fe_2.69Mg_0.37Al_1.91Si_2.02Cl_1.98, XFe_0.88, which is the most Cl-rich mica so far described from natural samples (10.98 wt% Cl) and is very close to the theoretical formula of chloroferrokinoshitalite BaFe₃Al₂Si₂O₁₀Cl₂. The positive correlation of Ba with Al and their negative correlation with Si and K is corresponding to the coupled substitution Ba₁Al₁K_-1Si_-1 linking the composition of phlogopite and kinoshitalite. Composition trend related with the Ti-content shows that Ti correlates positively with Ba but negatively with Cl, XFe, and with the sum of Mg and Fe. It implies that Ti is incorporated into mica in coordination with O (Ti₁O₂(Mg,Fe²⁺)_-1(OH)_-2) and it leads to the formation of oxykinoshitalite (BaMg₂TiSi₂Al₂O₁₂). Since the incorporation of either Cl or Ti + O correlates with XFe content of mica, XFe ratio can be the crucial factor controlling the ability of mica to incorporate Cl into its crystal lattice. In some cases, two micas with contrasting composition corresponding closer to chloroferrokinoshitalite or oxykinoshitalite coexist in one polyphase inclusion, demonstrated by distinct content of XFe, Ti and Cl (for example: XFe_0.20:0.77, Ba_0.48:0.63, Ti_0.35:0.02, Cl_0.27:1.45). This could imply the existence of an immiscibility between the composition trends of chloroferrokinoshitalite and oxykinoshitalite .

Such Ba, Cl and K-rich phases are atypical for garnet pyroxenite. Their presence may be caused by the injection of fluid/melt of crustal source during subduction and subsequent exhumation processes or may be related to earlier mantle metasomatism. The presence of Cl-rich phases together with carbonates indicates extremely high activity of Cl and CO₂ in the metasomatizing fluid/melt that interacted with garnet pyroxenites.

How to cite: Zelinková, T., Racek, M., and Abart, R.: Compositions of Ba-Cl-rich micas and other uncommon phases related to metasomatism of garnet pyroxenite (Gföhl unit of the Moldanubian Domain, Bohemian Massif), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7935, https://doi.org/10.5194/egusphere-egu22-7935, 2022.

Peridotite xenoliths are of great interest for research, since their composition is closest to the simulated compositions of the upper mantle, and they also make it possible not only to determine the conditions for the formation of these rocks, but also the degree of metasomatic processing of the diamondiferous keel, as well as the thickness and distribution area of diamondiferous rocks in the lithospheric mantle.

The Middle Paleozoic (D3-C1) diamondiferous kimberlite pipe Komsomolskaya-Magnaya was chosen as the object of research. This is one of the diamondiferous pipes of the Siberian platform, which contains many unchanged xenoliths of peridotite rocks.

We studied a collection of 180 peridotite xenoliths of the Komsomolskaya-Magnitnaya pipe, of which 104 belong to dunite-harzburgite paragenesis, 74 to lherzolite and 4 websterites. Also, we studied a large number of minerals from the concentrate material of the Komsomolskaya-Magnitnaya kimberlite pipe.

A high proportion (~ 30%) of peridotites with high magnesian olivines (Mg #> 93 mol%) indicates the presence of a block of highly depleted rocks in the lithospheric mantle.

We noted a high proportion of garnets with S-shaped REE distribution spectra (~ 60%), as well as garnets belonging to the harzburgite-dunite paragenesis in accordance with the CaO-Cr₂O₃ diagram. It indicates a moderate role of metasomatic changes associated with silicate melts, as well as interaction with carbonatite melts enriched in LREE.

In addition, kimberlite indicator minerals (KIM) (garnets, chrome spinels, ilmenites) were studied, sampled directly from 7 geophysical anomalies, 6 new kimberlite bodies, and kimberlite pipes Interkosmos, Kosmos-2, 325 years of Yakutia, belonging to the Upper Muna field. These data provide more information on the composition of the lithospheric mantle within the entire Upper Muna field.

For several kimberlite bodies, a high proportion of KIM of the diamond association is noted, however, for most kimberlite bodies, signs of a high degree of secondary metasomatic processes are noted, which negatively affect the preservation of diamond in the lithospheric mantle.

Cr-spinels from various kimberlite bodies of the Upper Muna field attract special attention. In addition to the typical peridotite Cr-spinels, there are Cr-spinels that follow the magmatic trend (Sobolev, 1974) and have extremely low contents of aluminum and titanium. The genetic identity of these Cr-spinels is still unknown.

Was done precise pressure (P)-temperature (T) estimation using single-clinopyroxene thermobarometry (Nimis, Ta). Was obtained mantle paleogeotherm.  Data was received about surface heat flux ~34–35mW/m2, 225–230 km lithospheric thickness, and 110–120 thick “diamond window” for the Upper Muna field (Dymshits et al, 2020).

• Dymshits A. M., Sharygin I. S., Malkovets V. G., Yakovlev I. V., Gibsher A. A., Alifirova T. A., Vorobei S. S., Potapov S. V., Garanin V. K. Thermal state, thickness, and composition of the lithospheric mantle beneath the Upper Muna kimberlite field (Siberian Craton) constrained by clinopyroxene xenocrysts and comparison with Daldyn and Mirny fields // Minerals. 2020. V. 10. P. 549.
• Sobolev N.V., Deep inclusions in kimberlites and the problem of the composition of the upper mantle // Novosibirsk: Nauka, 1974.

How to cite: Iakovlev, I., Malkovets, V., and Gibsher, A.: Features of the composition and structure of the lithospheric mantle of the Upper Muna field., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9103, https://doi.org/10.5194/egusphere-egu22-9103, 2022.

Nea Roda and Gomati ultramafic bodies (east Chalkidiki, north Greece) consist of both Cr- and Al- podiform chromitites, which are highly altered. Their PGE geochemistry and subsequently PGE-mineralogy (PGM) demonstrate abnormal element concentrations with an enrichment in PPGE (Pd, Pt), leading to high Pd/Ir ratios. Secondary PGM and base metal assemblages are dominated by Sb and As, whereas primary phases form sulphides. At a more mature stage, desulphurization of the aforementioned phases led to formation of native metals. Diopside hosted within diopsidite and chromitite show both an alkaline melt- and a fluid- rock interaction, depicted by LREE enrichment. The temperature of the metasomatic fluids was lower than 600^oC, as recorded by chlorite and garnet geothermometry. A raise in fluid mobile elements (FME: B, Sb, Li, As, Cs, Pb, U, Ba and Sr) is noted in the whole rock and clinopyroxene analysis. All these characteristics along with the distinctive spinel textures (porous, zoned grains) point to a metasomatic event during subduction that led to the post-magmatic modification of the chromitites and the mantle section causing a LREE, Pb, As, Sb, Pd and Pt enrichment. 

How to cite: Koutsovitis, P., Sideridis, A., Tsitsanis, P., Zaccarini, F., Tsikouras, B., Hauzenberger, C., Grammatikopoulos, T., Bindi, L., Garuti, G., and Hatzipanagiotou, K.: Mantle metasomatism recorded upon bimodal chromitites (E. Chalkidiki, Greece): a tool to unravel metasomatic processes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9331, https://doi.org/10.5194/egusphere-egu22-9331, 2022.

Southern Sweden (Scania region) is located in the peripherical parts of the East European Craton (EEC). In the Mesozoic, up to three pulses of volcanic activity took place between 191 and 110 Ma (Bergelin et al., 2006, IJES; Tappe et al., 2016, GCA). Some of the alkali basaltoids carry ultramafic, mafic and felsic xenoliths (Rehfeldt et al, 2007, IJES). In this study, we focused on the evolution of the lithospheric mantle sampled by anhydrous, spinel-facies lherzolites, harzburgites, and subordinate dunites.

Based on the Fo content in olivine, the peridotites were classified into three groups. Group X peridotites are characterized by Ca-rich olivine (890-1470 ppm) with Fo=91.1-91.7.  Enstatite has Mg#=91.5-91.9 and Al=0.16-0.22 atoms per formula unit (apfu), while the Cr-augite has Mg#= 90.8-91.2 and Al=0.21-0.28 apfu. Clinopyroxene is chemically homogenous in terms of trace elements and is LREE-enriched with positive Eu-anomaly. The Nd and Sr isotopic ratios in clinopyroxene are ¹⁴³Nd/¹⁴⁴Nd=0.512548 (εNd=2.63) and  ⁸⁷Sr/⁸⁶Sr=0.704237, respectively. Olivine in group Y peridotites is Ca-poor (<951 ppm) and has Fo=89.5-91.1, enstatite has Mg#=89.7-91.7, and Al content of 0.084-0.169 apfu. The Cr-diopside has Mg#=90.8-93.5 and Al=0.118-0.232 apfu. Trace element patterns in clinopyroxene allow subdivision of this group into two subgroups: subgroup Y1 – with heterogeneous LREE-enriched clinopyroxene, and subgroup Y2 – with homogenous LREE-enriched clinopyroxene; both groups are characterized by a positive Eu anomaly, but in subgroup Y1 it is significantly more pronounced. The Nd and Sr isotopic ratios in clinopyroxene from subgroup Y1 are ¹⁴³Nd/¹⁴⁴Nd=0.512624–0.512644 (εNd=4.13-4.52) and ⁸⁷Sr/⁸⁶Sr=0.703027–0.703100, therefore significantly more depleted than group X. In group Z peridotite the Fo content in olivine is 88.1-89.1, the Mg# in enstatite is 89.1-89.5 and its Al content is 0.19-0.20 apfu. The Mg# of Cr-diopside is 88.5-89.4 and the Al content is 0.24-0.25 apfu. The trace elements contents in clinopyroxene is homogenous and the REE pattern is flat at values double that in the primitive mantle.         

 The highest equilibration temperatures were estimated for the group X xenoliths, where T_WES=1101-1110 °C (Witt-Eickschen and Seck, 1991, CMP) and T_BK=1214-1241 °C (Brey and Köhler, 1990, JoP).  The temperatures calculated for group Y xenoliths are T_WES=875-1033 °C and T_BK=872-1027 °C and do not significantly differ between subgroups. Temperatures recorded by the group Z sample are T_WES=1040-1056 °C and T_BK=1065-1081 °C.

The composition of group X peridotites suggests their metasomatism by a high-temperature mafic melt resembling the basaltoids from Scania. Alternatively, they may represent high-pressure cumulates, as suggested by their coarse-grained texture. The group Y peridotites record cryptic metasomatism of a significantly depleted peridotite (melt extraction ranging typically between 25 and 30%) by a carbonatitic melt. The carbonatitic metasomatic agent was fractionating chromatographically from REE-, Th- and U-rich in subgroup Y2 to -poor in those elements in subgroup Y2. The group Z peridotite possibly represents depleted peridotite which was further metasomatized by a mafic melt. The lithospheric mantle beneath the marginal part of EEC has a complex composition, which is however different from a typical cratonic mantle.

Founded by Polish National Science Centre grant no. UMO-2016/23/B/ST10/01905 and WTZ PL 08/2018.

How to cite: Matusiak-Małek, M., Mikrut, J., Puziewicz, J., Kukuła, A., Ntaflos, T., Aulbach, S., Johansson, L., and Grégoire, M.: Composition of lithospheric mantle beneath southern margin of East European Craton evidenced by peridotitic xenoliths from Scania, S Sweden., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9457, https://doi.org/10.5194/egusphere-egu22-9457, 2022.

The Mirdita Ophiolite in northern Albania forms a ~240 km long and ~40 km wide zone within Dinaric-Hellenic belt. It marks suture after Neo-Tethyan Ocean closure. The chemical diversity of volcanic crustal rocks led to its division into two zones: the eastern one is interpreted to have Supra-Subduction Zone (SSZ) origin, whereas the western zone exhibits Mid-Ocean Ridge (MOR) affinity. More than a dozen of ultramafic massifs occur along the entire length of the ophiolite.

In this study we focus on chemical diversity of peridotites from two adjacent massifs, Kukes and Puka, which have SSZ and MOR affinities, respectively. The Kukes Massif is composed of a sequence from harzburgites at its base to clinopyroxene-poor dunites at the top, followed by pyroxenitic and peridotitic cumulates at the mantle/crust transition zone. The Puka massif is a mantle dome, composed of harzburgites and plagioclase/amphibole lherzolites (locally mylonitzed) and it is interpreted as a former oceanic core complex (OCC; Nicolas et al. 2017). Both massifs are pervasively penetrated by pyroxenitic and gabbroic veins and are serpentinised to variable degree.

Chemical composition of minerals varies between samples and lithologies, as well as between massifs. Olivine from the Kukes harzburgites has higher Fo values and NiO contents than that from dunites (Fo_89.5-92 and NiO 0.31-0.52 wt.% vs. Fo_88.1-91.2 and NiO 0.15-0.30 wt.%, respectively). Clinopyroxene has Mg#_92.5-95.1 and Al=0.03-0.08 apfu in harzburgite, while interstitial dunite clinopyroxene has Mg#_94-98 and Al below 0.03 apfu. Harzburgite orthopyroxene has Mg#_90.1-91.8 and Al=0.03-0.08 apfu. Chromian-spinel has Cr#_0.55-0.72 and Mg#_0.46-0.56 in harzburgites and Cr#_0.63-0.86 and Mg#_0.25-0.48 in dunites, moreover in dunites it often exhibits chemical zonation with Cr# increasing to core. Chemical composition of minerals changes gradually in the scale of single outcrop, with Fe content increasing toward veins.

The Puka peridotites have more enriched composition. Olivine has Fo_87.8-90.8 and NiO=0.25-0.43 wt. %, clinopyroxene has Mg#_90.1-93.3 and Al=0.05-0.15 apfu, orthopyroxene has Mg#_88.5-91.0 and Al=0.03-0.1 apfu, while spinel has Cr#_0.38-0.55 and Mg#_0.42-0.57, with single sample of Cr#_0.60-0.75 and Mg#_0.33-0.52. Plagioclase is Ca-rich (77-95 An), amphibole – occurring in some lherzolites – has composition of pargasite-tremolite.

Differences in lithological and chemical composition are visible between peridotites from both massifs, which correspond with diversity of crustal rocks and suggest that also mantle sections of the ophiolite record different origin. Peridotites from Kukes are harzburgites and dunites pointing to their refractory nature. The depleted peridotites were further affected by intensive magmatic veining. Infiltration of the melt triggered gradual enrichment in Fe of the silicates and chemical zonation of spinel. This process is well visible in dunites, where changes of Fe contents can be followed on distances of few meters. As metasomatic modification has a limited range, most of chemical differences have to be related with different protolith, but further studies are required to reconstruct rocks evolution.

Protolith of Puka peridotites is more fertile compared with Kukes, but reaction between veins and host lherzolite was not observed, and mylonitization led to Al depletion in pyroxenes.

This study was financed from scientific funds for years 2018-2022 as a project within program “Diamond Grant” (DI024748).

How to cite: Mikrut, J., Matusiak-Małek, M., and Puziewicz, J.: Preliminary insights into lithological and chemical diversity in Mirdita Ophiolite peridotite massifs – Kukes and Puka case studies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9560, https://doi.org/10.5194/egusphere-egu22-9560, 2022.

Many aspects of structure and thermal state of >200 km thick cratonic lithospheric mantle (CLM) remain unclear because of insufficient sampling and uncertainties of pressure (P) and temperature (T) estimates. An exceptionally detailed record of equilibration temperature and composition for the central Siberian craton in the 60–230 km depth range was obtained using new and published petrographic and in-situ chemical data for ~200 garnet peridotite xenoliths from the Udachnaya kimberlite. The thermal profile is complex with samples between 35 and 40 mW/m² model conductive geotherms as well as hotter layers in the middle and at the base (190–230 km) of the CLM. A previously unknown mid-lithospheric zone includes rocks up to 150° hotter than ambient geotherm, with high modal garnet and cpx, low-Mg# and melt-equilibrated REE patterns. We posit that hot domains with enriched compositions may form at depths where ascending melts stall (e.g., due to loss of volatiles and/or redox change) and react with wall-rock harzburgites. By contrast, we find no rocks rich in volatile-rich metasomatic amphibole, mica or carbonate, nor layers composed of peridotites with distinct melt-extraction degrees. The CLM base contains both coarse and variably deformed rocks heated and re-worked (Mg#_Ol down to 0.86) by localized interaction with asthenospheric melts.

How to cite: Ionov, D., Liu, Z., Nimis, P., Xu, Y., and Golowin, A. V.: Xenolith-based thermal and compositional lithospheric mantle profile of the central Siberian craton, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13175, https://doi.org/10.5194/egusphere-egu22-13175, 2022.

Dyke swarms intruding the mantle–continental crust transition of the Adria plate as documented by the Ivrea-Verbano Zone (IVZ, Southern Alps) represent a unique opportunity to investigate the evolution of mantle melts from Late Paleozoic to Mesozoic in the post-collisional Variscan realm. Thus, we present new petrological and geochemical data of dyke swarms cropping out in the Finero Phlogopite Peridotite mantle unit. Dykes are from a few cm to >1 m thick and cut at a high angle the mantle foliation.

The dyke swarms are composed of cumulus phlogopite-bearing amphibole peridotite, hornblendite, diorite and anorthosite. Many dykes are composite, showing variable proportions of melanocratic and leucocratic layers. Volatiles overpressure during the late magmatic stage is testified by plastic flow and development of a porphyroclastic structure by deformation of early cumulates and by the widespread segregation of a fine-grained mica matrix. The dyke swarms show mineralogical and geochemical features varying between two end-member series.

A dyke series is characterized by Al-rich pargasite (Al₂O₃ up to 18 wt.%) and phlogopite, associated with apatite, calcite, sulphides and sometimes sapphirine. The amphiboles show i) large LILE and LREE contents, ii) negative Nb, Ta, Zr and Hf anomaly and iii) isotopic oxygen composition heavier than the mantle interval, which support the occurrence of recycled continental crust components in the parent melts and impart an overall “orogenic” affinity.

The second series mainly consists of Al-poorer pargasite, phlogopite and albite (An 8-10), associated with apatite, monazite, ilmenite, zircon, Nb-rich oxides and carbonates. Mineral compositions and assemblages indicate that the parent melts were strongly enriched in Fe, Na, H₂O, P and C. Amphiboles are still enriched in LILE and LREE, but show extreme enrichments in Nb, Ta, Zr and Hf. As a whole, the petrochemical features point to an “anorogenic” alkaline affinity. Zircons from the “anorogenic” dykes are mostly anhedral, with homogenous internal structure or sector zoning. The strongly positive εHf_t (average of +10) of zircons and the Sr isotopic composition of amphiboles (0.7042) point to a derivation of such “anorogenic” melts from mildly enriched mantle sources. Concordant ²⁰⁶Pb/²³⁸U zircon ages for “anorogenic” dykes vary from 221 ± 9 Ma to 192 ± 8 Ma. Some dykes show both “orogenic” and “anorogenic” affinities, thus recording different pulses of mantle melts and metasomatic overprinting. As a whole, the dyke swarms show a transition from “orogenic” to “anorogenic” affinity indicating re-opening of dykes’ conduits for the melt ascending, pointing to a progressive change of the mantle sources of the Mesozoic magmatism of the Southern Alps.

How to cite: Ogunyele, A. C., Giovanardi, T., Bonazzi, M., Mazzuccheli, M., De Carlis, A., Cipriani, A., and Zanetti, A.: Transition from “orogenic-like” to “anorogenic” geochemical affinity in Mesozoic post-collisional magmatism: evidence from alkali-rich dykes from Ivrea-Verbano Zone (Southern Alps), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13428, https://doi.org/10.5194/egusphere-egu22-13428, 2022.

Dehydrated fluids expelled from serpentinized mantle in the subducted slab are gradually recognised as a vital role in generating arc magmatism and element cycling in the Earth. However, it remains not clear about their recycling at various depth in subduction zones and if slab serpentinite-derived fluids contribute to the genesis of lavas from the back-arc basins. Here, we study the magnesium (Mg) isotopic compositions of lavas from the Okinawa Trough (OT) and Lau basin (LB) as Mg isotopes have shown great potential to trace dehydration of slab serpentinites in recent years. Overall, lavas from the OT and LB have averagely heavier Mg isotopic compositions relative to the mid-ocean ridge basalt (MORB) mantle, which could be attributed to the involvement of slab serpentinite-derived fluids rather than crustal assimilation or input of subducted sediments as indicated by the isotopic modelling results. The δ²⁶Mg values of the southern OT (SOT) and southern LB (SLB) are generally higher than the middle OT (MOT) and northern LB (NLB), respectively, with an average of -0.11 ± 0.06‰ (2SD, n=5) for the SOT, -0.20 ‰ ± 0.04 (2SD, n=5) for the MOT, -0.13 ‰ ± -0.08 for the SLB (2SD, n=6) and -0.19 ‰ ± 0.06 (2SD, n=10) for the NLB. The binary modelling results have shown that various amounts of serpentinite-derived fluids could explain the variations in Mg isotopic compositions observed in the OT and LB. Combined published δ²⁶Mg values in subduction zones with our data, the thermal structure of inter-subduction zone may play a first control on the signal of Mg-rich serpentinite-derived fluids. By contrast, the contributions of these fluids to different segments in a specific subduction zone may depend on the slab depth beneath magmatic activity sites.

How to cite: Ding, Y., Jin, X., Li, X., Li, Z., Liu, J., Wang, H., Zhu, J., Zhu, Z., and Chu, F.: Magnesium isotopic composition of back-arc basin lavas and its implication for the recycling of serpentinite-derived fluids, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-877, https://doi.org/10.5194/egusphere-egu22-877, 2022.

It is generally accepted that subduction zones are important sites for element recycling into the Earth’s mantle. This does in particular also include carbon, which is transported in the form of organic carbon and carbonates. While organic carbon is expected to effectively fix carbon in the slab, carbonates are often entitled as an important CO₂ source for arc magmatism. The exact composition of the total subducted carbon load, in terms of oxidised and reduced carbon material, changes between different slabs and consequently the total released carbon varies significantly among suduction zones. An important mechanism for carbon release is the dissolution of carbonates in aqueous fluids. Ophicarbonates, containing both serpentine and carbonate minerals, are thus of special interest: The fluid released through serpentine dehydration reactions interacts with carbonates and causes the release of carbon. However, to better constrain the carbon release it is essential to understand the release of fluid in carbonated systems.

In this study we present a detailed experimental analysis on the effect of carbonates on the fluid release from serpentinites. We performed multi-anvil experiments on model ophicarbonates. Our starting material was a mixture between natural antigorite and Ca-carbonate and/or graphite. We also conducted thermodynamic calculations on various serpentinite-carbonate systems. Our experimental results show that serpentine dehydrates at temperatures <600 °C at 2.5 GPa, which is lower with respect to uncarbonated serpentinites. For a serpentinite with 20 wt% CaCO₃ the dehydration of serpentine thus takes place at 50 - 60 km depth. In the absence of CaCO₃ the fluid is released at 60 - 70 km depth. In cold subduction zones this shift in dehydration depth is even more extreme: In a carbonated system the serpentine was found to dehydrate at 80 - 110 km depth, in comparison to 110 - 130 km depth in the uncarbonated system. We found that this shift is mainly due to Ca-Mg exchange reactions between the carbonate and silicate fraction. The experimental run products show distinct dehydration mineralogy, forming Ca-silicates and Mg-bearing carbonates. In combination with mass balance calculations we show that the total carbonate-fraction does not decrease over the whole experimental temperature range. In conclusion, serpentinites with a high Ca-carbonate content are expected to dehydrate earlier in the subduction zones, whereas the carbon remains in the slab. The presence of Ca-carbonate thus has the potential to prevent subduction of water into deeper levels of the Earth’s mantle.

How to cite: Eberhard, L., Plümper, O., and Frost, D. J.: Experimental constraints on low temperature dehydration induced by mineral reactions in calcite-bearing ophicarbonates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1215, https://doi.org/10.5194/egusphere-egu22-1215, 2022.

Subduction zones are principal pathways for the cycling of volatiles such as  hydrogen and carbonfrom the Earth’s surface to the mantle and back to the atmosphere. This cycling has significant long-term effects on Earth’s climate. However, the processes that lead to volatile release during subduction and total volatile fluxes are poorly understood. In our study, we will quantify and characterize the network architecture of dehydration pathways exhibited as mineralized olivine-bearing metamorphic veins in the exhumed meta-serpentinites from the Erro-Tobbio unit, Italy [1]. Applying network analytical methods and graph theory both macroscopically and microscopically can provide the mode of propagation and describe the controlling factors affecting the evolution of these dehydration networks. Furthermore, multiscale observations can confirm the scalability of the vein network and if quantitative results such as permeability or volatile flux can be extrapolated to larger scales.

Along with 2-D network analysis, these vein networks will be analyzed in 3-dimensions using X-ray tomography and sophisticated machine-learning methods, such as generative adversarial networks. The results of both will be compared, which can then assure whether current machine-learning methods can effectively create statistically equivalent copies of these networks. Lastly, the synthesis of 2-D and 3-D multiscale results should provide meaningful parameters for accurate calculations of volatile flux during the dehydration of subducting slabs. 

[1] Plümper et al. (2017) Nature Geoscience 10(2), 150-156.

How to cite: Arias, A., Beinlich, A., Eberhard, L., Scambelluri, M., and Plümper, O.: Multidimensional Analysis of Serpentinite Dehydration Networks and Implications for Volatile Flux in Subduction Zones, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2584, https://doi.org/10.5194/egusphere-egu22-2584, 2022.

Rutile, titanite and ilmenite are the most common Ti-bearing minerals found in metamorphic rocks of variable grades. Rutile and titanite, in particular, are extremely useful minerals as they can be dated using U-Pb, and Zr concentrations are calibrated as geothermometers for both minerals, making them valuable petrochronometers. Previous experimental studies on MORB composition [1] established that titanite is more stable at LT-LP, rutile at HP (> 12 kbar), while ilmenite at HT-LP metamorphic conditions. Despite these phase stabilities, the natural occurrence of rutile at LP (< 12 kbar) and titanite at HP (> 20 kbar) and ilmenite at both HP and LP indicates strong uncertainties on our current understanding about their stabilities. [2] demonstrated a non-trivial compositional effect mainly driven by CaO content, on the titanite-out reaction for granitoid compositions (2-4 kbar). For MORB compositions, experimental constraints are currently lacking in the 400-600 ºC temperature range.

Here we present the results of a set of experiments run in a piston-cylinder apparatus using a gold capsule with a NNO oxygen fugacity buffer. We tested multiple starting materials, with different Ti/Ca values, including: 1) a pulverised eclogite (MORB composition) powder with titanite and rutile as well as a few initial eclogitic silicate mineral seeds, promoting nuclei for mineral overgrowth, 2) the same eclogite, glassed and pulverised in the lab, with fewer product seeds, and some of these with added Ti powder; 3) a different MORB powder with crushed titanite and kaersutite seeds. More than 30 experiments were conducted, with pressure ranging between 12 and 23 kbar, and temperature between 400 and 750 ºC in water-saturated conditions and using a cold pressure-seal capsule technique. Due to the challenging LT experiments, equilibrium is not attained, but dissolution and precipitation features are often observable. Epidote is one of the first minerals to nucleate and grow when the initial water content is > 10 wt%, and crystallisation is followed by amphibole. We show that when Ti/Ca is high, rutile is stable even at lower pressures, and when Ti/Ca is low, titanite seeds appear metastable even at higher pressures (19 kbar) and low temperatures. This is in agreement with petrological observations (i.e. peak titanite reported in blueschist rocks). At lower water saturation conditions (10 wt%), reactions are more sluggish, but successful experimental assemblies show that at 600 ºC and 14 kbar titanite seeds become unstable and start reacting with the basalt bulk rock powder to form ilmenite. We found that H₂O content, as well as Ti/Ca ratios appear to influence the stability of these Ti-phases in a mafic system. These results can be used to constrain the stabilities of rutile, titanite and ilmenite, which in turn elucidate the P-T-X conditions that these accessory minerals are able to record.

[1] Liou, et al. (1998). Schweiz. Mineral. Petrog. Mitt., 78, 317-335. [2] Angiboust, S., & Harlov, D. (2017). Am. Min., 102, 1696-1708.

How to cite: Pereira, I., Koga, K., and Bruand, E.: New rutile and titanite phase stability constraints at subsolidus conditions in a mafic system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3092, https://doi.org/10.5194/egusphere-egu22-3092, 2022.

Metasomatic rocks in orogenic mélanges bear critical information about fluid-rock interactions and element mobilities during subduction processes. The Yuli belt contains a few mélange units that crop out high-pressure blocks of metaigneous rocks and serpentinites enclosed in metasedimentary rocks. Metasomatic rocks are found along contacts between the serpentinites and metasedimentary rocks. However, the protolith and formation of those metasomatic rocks are largely unknown. Meter-scale metasomatic zones occur at the contact between pelitic schists (PS) and serpentinites (SP) in the Tsunkuanshan area. Five zones from PS to SP are newly identified: (I) chlorite-albite schist, (II) amphibole-albite rock, (III) albite-chlorite schist, (IV) epidote-chlorite schist, and (V) chlorite-talc schist. Minor garnet and amphibole (glaucophane core - barroisite mantle - actinolite rim) are present in the zone I and II, respectively. Field and petrographic observations combined with whole-rock major elements data suggest that this rock association likely was formed by chemical exchanges between the SP and PS. However, the zone II shows enrichment of Si, Na, and Ca, but Al depletion relative to the other metasomatic rocks. This anomaly might be due to infiltration of external fluids. Rare earth element patterns of the PS, zone I, II, III, and IV are similar, indicating a similar protolith origin. Hence, the original boundary between the PS and SP is likely between the zone IV and V. We estimate the chemical mass balance from the PS to the metasomatic rocks (zone I, II, III, and IV) using the sparse isocon method (Kuwatani et al., 2020). The result shows that the chemical components in zone I, III, and IV are gained relative to the PS, whereas those in zone II are of loss. We interpret that the zone I, III, IV, and V were produced by diffusive exchanges of components between the PS and SP, whereas formation of the zone II was likely created by Na-Ca rich fluid infiltrations. The newly-found occurrence of glaucophane within the zone II indicates fluid-rock interactions during subduction metamorphism.

Keywords: Chemical mass balance, sparse isocon method, Na-Ca rich fluids, Yuli belt.

How to cite: Dewangga, D. D., Tsai, C.-H., Lee, H.-Y., Iizuka, Y., Lo, W.-H., and Lee, C.-Y.: Metasomatism between serpentinite and pelitic schist in the Yuli belt, eastern Taiwan: fluid-rock interactions during subduction metamorphism, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3423, https://doi.org/10.5194/egusphere-egu22-3423, 2022.

Earth’s carbon cycle is strongly influenced by subduction of sedimentary material into the mantle. The composition of the sedimentary subduction flux has changed considerably over Earth’s history, but the impact of these changes on the mantle carbon cycle is unclear. Here we show that the carbon isotopes of kimberlite magmas record a fundamental change in their deep-mantle source compositions during the Phanerozoic Eon. The ¹³C/¹²C of kimberlites prior to ~250 Myr preserves typical mantle values, whereas younger kimberlites exhibit lower and more variable ratios – a switch coincident with a recognised surge in kimberlite magmatism. We attribute these changes to increased deep subduction of organic carbon with low ¹³C/¹²C following the Cambrian Explosion when organic carbon deposition in marine sediments increased significantly. These observations demonstrate that biogeochemical processes at Earth’s surface have a profound influence on the deep mantle, revealing an integral link between the deep and shallow carbon cycles.

How to cite: Giuliani, A., Drysdale, R. N., Woodhead, J. D., Planavsky, N. J., Phillips, D., Hergt, J., Griffin, W. L., Oesch, S., Dalton, H., and Davies, G. R.: Perturbation of the deep-Earth carbon cycle in response to the Cambrian Explosion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3611, https://doi.org/10.5194/egusphere-egu22-3611, 2022.

The formation of carbonated serpentinites (serpentine, Mg-Ca carbonates) and listvenites (quartz, Mg-carbonate) by reactions between exhumed mantle peridotites and percolating CO₂-bearing fluids is a major sink for carbon from spreading ridges to ophiolites and orogenic suture zones. During ICDP Oman Drilling Project, the transition from the base of the Semail Ophiolite to its metamorphic sole was drilled at Hole BT1B (Wadi Mansah), allowing to recover ~200 m of variously carbonated serpentinites and listvenites, and underlying metabasalts. Mineralogical and geochemical investigations indicate that carbonation at the expense of the Wadi Mansah peridotites was triggered by the migration of multiple fluid batches along the basal thrust at shallow depths and low temperatures (50-250 °C). To better constrain the impacts of fluid source(s) and protolith compositions on reaction pathways and oxidation state during carbonation, we carried out iron and zinc isotopes study of 19 variously carbonated peridotites (13 listvenites, 5 carbonated serpentinites, one serpentinized harzburgite) and of 6 underlying metamorphic samples from Wadi Mansah area (including 3 BT1B samples).

The partially serpentinized harzburgite and carbonated serpentinites have δ56Fe and δ66Zn compositions ranging between -0.05 – +0.06 ‰ and -0.11 – +0.15, respectively, overlapping that of previously analysed abyssal (δ56Fe: -0.15 – +0.11 ‰; δ66Zn: +0.12 – +0.62 ‰), ophiolitic (δ56Fe: -0.27 – +0.14 ‰; δ66Zn: -0.56 – +0.38 ‰), orogenic (δ56Fe: -0.06 – +0.12 ‰; δ66Zn: +0.03 – +0.55 ‰), and fore-arc (δ56Fe: -0.26 – +0.09 ‰) peridotites. In contrast, listvenites display highly variable δ56Fe and δ66Zn values, between -0.33 – +0.2 ‰ and -0.46 – +0.64 ‰ respectively. Iron isotopes compositions show a positive correlation with bulk iron contents. Zinc isotope compositions are positively correlated to δ13C_TC values, suggesting a high mobility of Zn in carbonate-bearing fluids. The lightest δ66Zn values were measured in listvenites with minor amounts of fuchsite (Cr-mica), that often display evidences for breakdown of Cr-spinel. Metamorphic sole samples display isotopic compositions typical of mafic rocks (δ56Fe: +0.01 – +0.24 ‰; δ66Zn: +0.24 – +0.47 ‰), in agreement with an oceanic crust-derived protolith (MORB, δ56Fe: +0.06 – +0.18; δ66Zn: +0.27 – +0.30 ‰).

Our results suggest an important control of the protolith chemistry and complexation with dissolved carbon in reactive fluids on the Fe and Zn isotopes compositions.

How to cite: Decrausaz, T., Godard, M., Debret, B., and Martinez, I.: Carbonation of peridotites along the basal thrust of the Semail Ophiolite (OmanDP Hole BT1B): insights from Fe and Zn isotopes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3929, https://doi.org/10.5194/egusphere-egu22-3929, 2022.

The role of subduction zones has been considered critical to understand carbon fluxes among the Earth’s reservoirs. At plate margins, most of the carbon is stored in carbonate sediments. Nevertheless, the past decade saw an increasing focus also on reduced carbon - kerogen and graphite – to understand its role in the deep carbon cycle. Most of reduced carbon derive from seafloor organic-rich sediments, even if, a little portion can form by decarbonation during metamorphism.

In the Palaeoproterozoic supracrustal rocks of the Lewisian Complex, graphitic marbles were found in a mixed succession of metasediments at Gott Bay, Island of Tiree (Scotland). Such marbles show bedding-parallel slip surfaces associated with chlorite that are absent in other marbles on the island that are devoid of graphite. Marbles and schists-hosted graphite were analysed showing marked differences in carbon isotopic composition and structural ordering measured by means of Raman spectroscopy.

Petrographic and chemical evidence support the hypothesis of an abiotic origin of the marble-hosted graphite and the mechanisms that led to its formation could explain the heavy isotopic composition of many Proterozoic marbles in the world.

How to cite: Schito, A., Parnell, J., Muirhead, D., and Boyce, A.: Evidence of abiotic graphite formation in Proterozoic marbles of the Lewisian Complex: mechanisms and consequences for the deep carbon cycle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5014, https://doi.org/10.5194/egusphere-egu22-5014, 2022.

The garnet in the ultra-high pressure (UHP) eclogites of the Erzgebirge (Bohemian Massif, Germany) trapped primary inclusions of metasomatic melt originated by the partial melting of the continental crust. The study of these inclusions alow us to estimate the contribution of the subducted continental crust to mantle metasomatism and deep carbon fluxes. The inclusions are randomly distributed in the inner part of the garnet, they are micrometric and occur as both polycrystalline, i.e. nanogranitoids, and glassy, often with a shrinkage bubble. Nanogranitoids consist of kumdykolite, quartz, kokchetavite, biotite, white mica, calcite and rare graphite. The inclusions share their microstructural position in the garnet with inclusions of polycrystalline quartz interpreted as quartz pseudomorph after coesite that indicate the entrapment at UHP conditions. The melt composition, measured on glassy inclusions and rehomogenized nanogranitoids, is granitic. The melt is also hydrous, slightly peraluminous and the trace element enrichments observed are consistent with an origin from the continental crust, testified by the high amount of incompatible elements such as Cs, Pb, Th, U, Li and B. Similar signatures were also reported elsewhere in the Bohemian Massif, e.g. in other metasomatic melts hosted in HP mantle eclogites, in metasomatized mantle rocks and in post-collisional ultrapotassic magmatic rocks, suggesting that mantle metasomatism from melts originated in the continental crust is widespread in the orogen.

The melt H₂O and CO₂ contents were measured with the NanoSIMS. The CO₂ values in particular were corrected reintegrating the vapor contained in the shrinkage bubble and are in average 19552 ± 772 ppm, the highest content of CO₂ measured so far in crustal melt inclusions. The modelled endogenic carbon flux associated with the subduction of the continental crust of the Variscan Orogenic Cycle is 22 ± 8 Mt C yr^-1. This flux within error is similar to the endogenic carbon fluxes in the serpentinized mantle (~ 14 Mt C yr^-1) and to the exogenic fluxes in mid-oceanic ridges (~ 16 Mt C yr^-1) and arc volcanoes (~ 24 Mt C yr^-1). Hence, in collisional settings, deeply subducted continental crust carried a large amount of volatiles to the mantle and the lower crust. Due to the absence of post collisional arc volcanism, most of these volatiles remained trapped in the root of mountain belts. This long-term storage of the carbon in the orogen roots prevents ultimately the closure of the carbon cycle.

How to cite: Borghini, A., Nicoli, G., Ferrero, S., O'Brien, P. J., Laurent, O., Remusat, L., Borghini, G., and Milani, S.: Deep subduction of continental crust contributes to mantle metasomatism and deep carbon cycle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5782, https://doi.org/10.5194/egusphere-egu22-5782, 2022.

The Paleoproterozoic Ketilidian orogen in South Greenland (1.85-1.73 Ga) is interpreted to be the result of northwards-dipping oblique subduction of an oceanic plate beneath the Archaean continental crust of the North Atlantic Craton. The Ketilidian orogen was part of the subducted-related magmatism and accretionary orogenic belt named the Great Paleoproterozoic Accretionary Orogen that existed along an active margin stretching through Laurentia (North America and South Greenland) to Baltica (Northeast Europe), which formed the supercontinent Columbia/Nuna. Thus, the orogeny represents part of an important episode of crustal growth and preservation in Earth’s history. The Central Domain of the orogeny is dominated by the plutonic remnants of a magmatic arc (the Julianehåb Igneous Complex (JIC), ca. 1.85-1.80 Ga), which eventually grew sufficiently large and stable to subsequently uplift and unroof, to produce rocks interpreted to represent erosional fore-arc deposits that are preserved to the south in the Southern Domain. Between ca. 1.80 Ga and 1.76 Ga, the fore-arc was subjected to metamorphism of amphibolite to granulite facies, and was subsequently intruded by post-tectonic granites (including rapakivi variants) of the Ilua Suite (1.75-1.73 Ga). We present new zircon U-Pb SIMS ages for granitic and metasedimentary rocks sampled at a regional scale in a traverse stretching NW to SW through the Central and Southern Domains of the Ketilidian Orogen in South Greenland. Previous studies have distinguished two pulses of magmatism in the JIC, an early event at ca. 1.85-1.83 Ga and a later phase at ca. 1.80-1.78 Ga. Our JIC samples are dominated by the late stage (<1.83 Ga) with most ages concentrated at 1.8 Ga, suggesting that the main volume of crust in the western portion of the arc was generated over a relatively short period. Ages for the Ilua Suite agree well with previous studies. Zircon age distributions in the metasedimentary rocks of the Southern Domain are consist with detritus dominantly sourced from the JIC, however the presence of small populations of older zircons (up to 2.8 Ga) not observed as inherited zircons in the JIC, indicates that older crustal components also eroded into the fore-arc. These U-Pb zircon results are part of an ongoing larger investigation combining O-Hf isotope compositions in zircon, coupled with whole rock geochemical and isotope data. This research will provide the first thorough geochemical and petrogenetic investigation of the timing, across arc variations, and source components involved in the formation and evolution of South Greenland as well as its contribution in one of the worldwide peaks of continental crustal growth.

How to cite: Vestergaard, R., Waight, T., Petersson, A., Jeon, H., and Whitehouse, M.: New zircon U-Pb geochronology from the Ketilidian orogen of South Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6180, https://doi.org/10.5194/egusphere-egu22-6180, 2022.

Subduction of carbon-bearing phases throughout Earth’s history may be an important mechanism of sourcing carbon to the Earth’s lower mantle. As carbon has very low solubility in mantle silicates, it is primarily present in accessory phases such as carbonates, diamond, or metal carbides. Previous studies indicate that more than half of the carbonate contained in the oceanic crust may survive metamorphism and dehydration in the sub-arc and reach the lower mantle, even though the oxygen fugacity in the deep mantle may not favour their stability [1]. Indeed, the presence of carbonate in ultra-deep diamond inclusions provides evidence for carbonate subduction at least down to the transition zone [2].

The carbonate phases present in the lower mantle depend on their bulk composition, the oxygen fugacity, and on their stability at a given pressure and temperature. Results from high-pressure experiments show that magnesite (MgCO₃) can be stable up to deep lower mantle conditions (∼80 GPa and 2500 K) [3]. Accordingly, magnesite may be considered the most probable carbonate phase present in the deep Earth. Experimental studies on magnesite decarbonation in presence of SiO₂ at lower mantle conditions suggest that magnesite is stable along a cold subducted slab geotherm [4, 5]. However, our understanding of magnesite’s stability in contact with bridgmanite [(Mg,Fe)SiO₃],  the most abundant mineral in the lower mantle, remains incomplete.

Hence, to investigate sub-solidus reactions, melting, decarbonation, and diamond formation in the system MgCO₃-(Mg,Fe)SiO₃, we conducted a combination of high-pressure experiments using multi-anvil press and laser-heated diamond anvil cells (LH-DAC) at conditions ranging from 25 to 70 GPa and 1300 to 2100 K.

Multi-anvil experiments at 25 GPa and temperatures below the mantle geotherm (1700 K) show the formation of carbonate-silicate melt associated with stishovite crystallization, indicating incongruent melting of bridgmanite to stishovite, in accordance with the recent finding of Litasov and Shatskiy [4]. LH-DAC data from in situ X-ray diffraction show crystallization of bridgmanite and stishovite. Diamond crystallization is detected using Raman spectroscopy. A melt phase could not be detected in situ at high temperatures.

Our results suggest a two-step process that starts with melting at temperatures below the mantle geotherm, followed by crystallization of diamond from the melt produced.  Therefore, we propose that subducted carbonate-bearing silicate rocks will not remain stable in the lower mantle and will instead melt at upper-most lower mantle conditions, fostering diamond formation. Our study also provides additional evidence that diamond production is related to carbonated melt. Consequently, the melting of recycled crust and chemical transfer to the surrounding mantle will hinder the transport of carbon deeper into the lower mantle.

[1] Stagno et al. (2015) Contrib. Mineral. Petrol. 169(2), 16.
[2] Brenker et al. (2007) EPSL 260(1-2), 1-9.
[3] Binck, et al. (2020) Physical Review Materials, 4(5),1-9.
[4] Litasov & Shatskiy (2019) Geochemistry International, 57(9), 1024-1033.
[5] Drewitt, et al. (2019). EPSL, 511, 213-222.

How to cite: Libon, L., Spiekermann, G., Sieber, M., Kaa, J., Dominijanni, S., Elbers, M., Blanchard, I., Albers, C., Bierdermann, N., Morgenroth, W., Appel, K., McCammon, C., Schreiber, A., Roddatis, V., Glazyrin, K., Husband, R., Hennet, L., and Wilke, M.: Subducted Carbon in the Earth’s lower mantle: The fate of magnesite, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9318, https://doi.org/10.5194/egusphere-egu22-9318, 2022.

Mechanisms such as crystallization differentiation, subduction erosion, delamination, or relamination that are responsible for the formation and modification of modern crust with an on average andesitic composition are actively debated (Hacker et al. 2015). Isotope fractionation associated with igneous processes is documented for many non-traditional stable isotope systems, making them promising tools to advance our understanding of modern arc crust formation. Titanium isotopes are especially promising, as volcanic and plutonic arc rocks show a trend from light to heavy isotope values with increasing SiO₂ concentration due to the fractionation of minerals with light Ti isotopes.

We present new Ti isotope data on medium K calc-alkaline to shoshonitic magmatic differentiation suites from the Adamello Batholith (N-Italy), Kos (Agean arc), Torres del Paine (Patagonia) and the Dolomites (N-Italy) in addition to crust-derived mafic cumulates. The Ti isotopic composition of dacites and granites range between δ⁴⁹Ti_OL-Ti ≈ 0.3 to 1.1‰, with heavier values for more alkaline granitic melts in agreement with published data (Hoare et al. 2020). Mafic cumulates from related and additional localities are overall isotopically lighter than (their) granitic counterparts ranging between δ⁴⁹Ti_OL-Ti ≈ -0.15 and +0.08‰. Cumulates of studied crustal sections enriched in Fe-Ti oxides (>5 modal %) show δ⁴⁹Ti values lighter than the depleted MORB mantle (DMM, δ⁴⁹Ti_OL-Ti ≈ +0.002 ± 0.007‰) and counterbalance the isotopically heavy composition of felsic rocks. The occurrence of cumulates heavier than DMM may have several reasons: (i) “heavy” cumulates may represent late-stage relicts of progressive magma differentiation containing trapped intercumulus melt or (ii) they experienced overprinting, e.g., by mafic rejuvenation.

We therefore find that the Ti isotopic composition of cumulate rocks and likely also the magmatic lower continental crust is influenced by their mineralogical composition. How this impacts the Ti isotopic composition of the bulk continental crust in the light of delamination and relamination processes needs further work.

REFERENCES

Hacker, B. R., Kelemen, P. B., & Behn, M. D. (2015). Continental lower crust. Annual Review of Earth and Planetary Sciences, 43, 167-205.

Hoare, L., Klaver, M., Saji, N. S., Gillies, J., Parkinson, I. J., Lissenberg, C. J., & Millet, M. A. (2020). Melt chemistry and redox conditions control titanium isotope fractionation during magmatic differentiation. Geochimica et Cosmochimica Acta, 282, 38-54.

How to cite: Storck, J.-C., Greber, N. D., Müller, A., Pettke, T., and Müntener, O.: Titanium isotopic fractionation of arc derived melts and cumulates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9783, https://doi.org/10.5194/egusphere-egu22-9783, 2022.

In subduction zones, serpentinite-hosted ophicarbonates and their main dehydration and decarbonation reactions linked to prograde metamorphism are relatively well understood. On the contrary, the geological conditions and processes leading to the carbonation of subduction-zone metaserpentinites by fluid–rock interactions remain poorly constrained. At different arc depths, the reaction of decarbonation fluids derived from marble and carbonate‐bearing sediment with slab and mantle wedge serpentinites, as well as tectonic mixing and deformation along subduction zone interface, may produce magnesite-bearing rocks with a bulk composition similar to that of ophicarbonates. Subsequently, these hybrid metasomatic lithologies will undergo decarbonation reactions at prograde or retrograde conditions which may influence the cycling of C and other volatiles from the slab to the mantle wedge and the global estimates of C fluxes at convergent margins. This can be evaluated through the study of exposed paleo-subduction metamorphic suites.

Here we investigate the tectonic, textural and mineralogical evolution of marble layers and magnesite-rich lenses hosted in chlorite harzburgite (Chl-harzburgite) in the Cerro Blanco ultramafic massif (Nevado-Filábride Complex, Betic Cordillera, S. Spain), which records high-pressure alpine subduction metamorphism as evidenced by the transition from antigorite serpentinite (top of the body) to Chl-harzburgite (bottom) due to high-pressure deserpentinization. Chl-harzburgite is separated from a gneiss and mica schist crustal sequence by a footwall of strongly heterogenous mylonite (around 20 m thick) encompassing: transposed, foliated and brecciated marble layers, foliated Chl-harzburgite lenses (in some cases completely transformed to retrograde serpentinite), centimetre to several decimetre thick boudins of idiomorphic coarse to very coarse magnesite aggregates, associated to chlorite and magnetite and enveloped by the mylonitic foliation, and, finally, abundant almost monomineralic amphibole aggregates. We interpret this mylonite zone as a detachment leading to the exhumation of the Cerro Blanco massif after reaching peak subduction metamorphic conditions that formed the Chl-harzburgite assemblage.

Combined field, EDS-SEM, and EPMA data obtained from a detailed cross-section sampling of this mylonite zone reveal that, locally, metamorphic equilibrium was reached between Chl-harzburgite and the transformation products of the magnesite boudins during the mylonite foliation development. Thermodynamic modelling of these assemblages allows inferring the relationship between deformation and metamorphic conditions during exhumation, including possible decarbonation reactions.

We thank the Universidad de Jaen 1263042 FEDER-UJA grant, funded by the European Social Fund and the European Regional Development Fund.

How to cite: López Sánchez-Vizcaíno, V., Padrón-Navarta, J. A., Laborda-López, C., Gómez-Pugnaire, M. T., Menzel, M. D., and Garrido, C. J.: Metaserpentinite carbonation and decarbonation reactions during subduction metamorphism and subsequent tectonic exhumation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9996, https://doi.org/10.5194/egusphere-egu22-9996, 2022.

Eclogite-hosted metamorphic veins mark former fluid migration pathways during a subduction-exhumation cycle, and allow to trace fluid-mediated element transfer across lithologies, to ultimately metasomatize the mantle wedge. Fluids can be generated by dehydration reactions at different P-T conditions in various lithologies, all influencing how different chemical constituents are dissolved and re-precipitated. Here we present a study of eclogite-hosted quartz-rich metamorphic veins in the Variscan Münchberg Massif. The eclogites probably represent subducted continental crust that was variably hydrated and subjected to amphibolite facies conditions before reaching eclogite facies peak conditions of ca. 3 GPa and 700°C.

Isolated, mm-sized quartz pockets with euhedral high-pressure minerals are common in the Münchberg eclogites, but continuous veins that may have allowed focused fluid flow beyond specimen scale are rare. Nevertheless, where such veins occur, they can contain high-pressure minerals such as garnet and omphacite, but also rutile, zircon, and allanite, indicating high field strength-element (HFSE) mobility at least on the specimen scale. Garnet- and omphacite-bearing veins are typically 1-10 mm thick with average crystal sizes of 1 mm and less. A different vein type is mostly similar in thickness, but consists of quartz + phenocrysts (sometimes >1 cm long) of kyanite, phengite, and/or rutile. Symplectite-rich selvages surrounded by mostly fresh host eclogite are common.

Oxygen isotope thermometry of quartz-garnet, quartz-phengite, and quartz-kyanite pairs yield temperatures around 700°C, interpreted to represent vein crystallization. δ¹⁸O values of vein quartz (+6.1 to +10.5‰) from all vein types are identical to δ¹⁸O values of host rock quartz (the latter were predicted from mass balance modelling at 700°C based on host rock δ¹⁸O values from +4.0 to +7.9‰). While it is evident that the garnet- and omphacite-bearing veins were formed under eclogite facies conditions, pressures are uncertain for the quartz-rutile, quartz-phengite, and quartz-kyanite veins. Still, vein formation at relatively high pressures seems probable, as solubilities of chemical components tend to increase with pressure, facilitating HFSE mobilization from the source rock. We propose that internal fluids were generated by dehydration of phengite and/or zoisite and/or amphibole from the eclogites. Isolated quartz-rich pockets formed in eclogites that may have released only small amounts of fluid, whereas continuous metamorphic veins were formed in eclogites that produced more fluid, probably reflecting a more intense hydration before eclogite facies metamorphism. The internal origin of the fluids supported by oxygen isotope evidence argues against fluid transport over large distances. The fluids may have largely remained in place before being consumed for symplectite formation upon retrogression to amphibolite facies conditions.

How to cite: Pohlner, J., El Korh, A., Klemd, R., Pettke, T., and Grobéty, B.: Eclogite-hosted metamorphic veins in the Münchberg Massif (Germany), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11108, https://doi.org/10.5194/egusphere-egu22-11108, 2022.

It has been recently proposed that high-pressure genesis of abiotic hydrocarbon can lead to strain localization in subducted carbonate rocks¹. However, the mechanical effects of the migration of these hydrocarbon-bearing fluids on the infiltrated rocks still need to be constrained.

In this study, we investigate omphacitite (i.e. omphacite-rich rock) adjacent to an high-pressure methane source from the Western Italian Alps (Italy) using a multiscale and analytical approach including petrographic, microstructural, X-ray compositional mapping and electron backscatter diffraction analyses (EBSD). In the field, omphacitite bands are 1-5 metres thick and tens of metres long and are adjacent to carbonate rocks affected by high-pressure reduction and methane production.

Hand specimens and thin sections display a brecciated structure, with omphacitite fragments ranging in size from a few microns to several centimetres, surrounded by a matrix of jadeite, omphacite, grossular, titanite, and graphite. X-ray compositional maps and cathodoluminescence images highlight oscillatory zoning and skeletal (jackstraw) textures in jadeite, omphacite and garnet in the matrix, suggesting a fast matrix precipitation under plausible disequilibrium conditions. CH₄ and H₂ are found in fluid inclusions in the jadeite grains. This feature suggests a potential link between the genesis of CH₄ in the adjacent carbonate rocks and the brecciation event.

EBSD analysis was performed on omphacitite clasts close to their borders, where omphacite grain size varies between a few microns and a maximum of 100 microns. Those omphacite grains display no crystallographic preferred orientation, abundant low angle boundaries and low (< 5°) internal lattice distortion. We interpret these textures as formed by pervasive and diffuse micro-fracturing related to the brecciation occurring at high pore fluid pressure, reaching sub-lithostatic values. This study suggests that at high-pressure conditions in subduction zones, the genesis and migration of hydrocarbon-bearing fluids can trigger fracturing in adjacent lithotypes.

¹Giuntoli, F., Vitale Brovarone, A. & Menegon, L. Feedback between high-pressure genesis of abiotic methane and strain localization in subducted carbonate rocks. Sci. Rep. 10, 9848 (2020).

This work is part of project that has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 864045).

How to cite: Giuntoli, F., Vitale Brovarone, A., and Menegon, L.: Hydrocarbon-bearing fluid migration produces brecciation at high pressure condition in subduction, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11350, https://doi.org/10.5194/egusphere-egu22-11350, 2022.

Sulfur is a key element in the subduction zone-volcanic arc system; however, the mechanism(s) that recycle sulfur from the slab into the overlying volcanic arc are debated. Here we summarize recent advances in quantifying this component of the deep sulfur cycle. First, primary metamorphic or inherited sulfides in oceanic-type eclogites are only rarely observed as inclusions and are typically absent from the rock matrix. Additionally, sulfides are relatively common in rocks metasomatized at the slab-mantle interface by slab-derived fluids during exhumation. Combined, these two observations suggest that sulfur loss from subducted mafic crust is relatively efficient. Thermodynamic modeling in Perple_X using the Holland and Powell (2011) database combined with the Deep Earth Water model suggests that the efficiency and speciation of sulfur loss varies depending on the degree of seafloor alteration prior to subduction and the geothermal gradient of the slab. In relatively cold subduction zones, such as Honshu, slab-fluids derived from subducted mafic crust are predicted to exhibit elevated concentrations of HSO₄^-, SO₄^2-, HSO₃^-, and CaSO_4(aq), whereas hot subduction zones, such as Cascadia, are predicted to produce slab fluids enriched in HS^- and H₂S at lower pressures. The oxidation of sulfur expelled from subducted pyrite is balanced by the reduction of Fe³⁺ to Fe²⁺, consistent with the low Fe³⁺/SFe of exhumed eclogites relative to blueschists and altered oceanic crust. Where oxidized S-bearing fluids are produced, they are anticipated to interact with more reduced rocks at the slab-mantle interface and within the mantle wedge, resulting in sulfide precipitation and significant isotopic fractionation. The δ³⁴S values of slab fluids are estimated to fall between -11 and +8 ‰. Rayleigh fractionation during progressive fluid-rock interaction results in fractionations of tens of per mil as oxidized species are depleted and sulfides are precipitated, resulting in δ³⁴S values of sulfides that easily span the -21.7 to +13.9 ‰ range observed in metasomatic sulfides in exhumed high-pressure rocks. However, in subduction zones where reduced species prevail, the S isotopic signature of slab fluids is expected to reflect their source and will exhibit a narrower range in δ³⁴S values. As a result, the δ³⁴S values measured in arc magmas may not always be a reliable indicator of the contribution of different components of the slab, such as sediments vs. AOC. Additionally, the impact of S recycling on the oxygen fugacity of arc magmas is expected to vary both spatially and temporally throughout Earth history.

How to cite: Walters, J., Cruz-Uribe, A., and Marschall, H.: Sulfur in the slab: A sulfur-isotopes and thermodynamic-modeling perspective from exhumed terranes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11697, https://doi.org/10.5194/egusphere-egu22-11697, 2022.

High-pressure COH fluids have a fundamental role in a variety of geological processes. Their composition in terms of volatile species can control the solidus temperature, carbonation/decarbonation reactions, and influences the amount of solutes generated during fluid-rock interaction at depth. Over the last decades, several systems have been experimentally investigated to unravel the effect of COH fluids at upper mantle conditions. However, fluid composition is rarely tackled as a quantitative issue, and rather infrequently fluids are analyzed in the same way as the associated solid phases in the experimental assemblage. A comprehensive characterization of carbon-bearing aqueous fluids in terms of composition is hampered by experimental difficulties in synthetizing and analyzing high-pressure fluids, without altering their composition upon quench.

Recently, improved ex situ techniques have been proposed for the analyses of experimental COH fluids, leading to significant advancement in synthetic fluids characterization. The development of customized techniques in order to investigate these fluids, in terms of volatile speciation and dissolved solute load, allowed to elucidate some of the processes involving carbon at high-pressure conditions and to assess its influence in the mantle wedge.

Some of the recently developed techniques employed for ex situ quantitative analyses of carbon-saturated COH fluids will be presented, such as the capsule piercing QMS technique (Tiraboschi et al., 2016) and the cryogenic LA-ICP-MS technique (Kessel et al., 2004; Tiraboschi et al., 2018). The capsule piercing QMS technique allow to measure the main uncharged volatile species in the COH system (i.e., H₂O, CO₂, CH₄, H₂, O₂, CO), while the cryogenic LA-ICP-MS technique permits to measure the amount solutes generated by mineral dissolution in COH fluids, in terms of mol/kg.

The results obtained by employing these analytical strategies indicate that a quantitative approach to COH fluid analyses is a fundamental step to understand the effect of carbon-bearing fluids at upper mantle conditions and to ultimately unravel the deep cycling of carbon.

Kessel, R., Ulmer, P., Pettke, T., Schmidt, M. W. and Thompson, A. B. (2004) A novel approach to determine high-pressure high-temperature fluid and melt compositions using diamond-trap experiments, Am. Mineral., 89(7), 1078–1086.

Tiraboschi, C., Tumiati, S., Recchia, S., Miozzi, F. and Poli, S. (2016) Quantitative analysis of COH fluids synthesized at HP–HT conditions: an optimized methodology to measure volatiles in experimental capsules, Geofluids, 16(5), 841–855.

Tiraboschi, C., Tumiati, S., Sverjensky, D., Pettke, T., Ulmer, P. and Poli, S. (2018) Experimental determination of magnesia and silica solubilities in graphite-saturated and redox-buffered high-pressure COH fluids in equilibrium with forsterite + enstatite and magnesite + enstatite, Contrib. to Mineral. Petrol., 173(1), 1–17.

How to cite: Tiraboschi, C.: Carbon-saturated COH fluids in the upper mantle: what ex situ experiments tell us about carbon at high-pressure and high-temperature conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11725, https://doi.org/10.5194/egusphere-egu22-11725, 2022.

The objective of this work is to study the fluid rock-interactions at low metamorphic grade in subduction zones. We focused in particular on the evolution of metapelites from the base of the seismogenic zone (⁓250℃) to the down-dip transition to the aseismic domain (⁓330℃). In the three examples examined here (Kodiak Complex in Alaska, Shimanto Belt in Japan, the French Alps), we followed the variations in mineralogy, trace element budget, as well as fluid inclusion elemental and isotopic (δ⁷Li) composition.

In the Kodiak and Shimanto belt, the mineralogy remains constant with temperature increase, with the dominance of phyllosilicates (white mica and chlorite), quartz and plagioclase. In more deformed zones of higher-T samples (330 ± 16℃ and 3 ± 0.4 kbar for Kodiak and 320 ± 14℃ and 3.9 ± 0.4 kbar for Shimanto belt) quartz and plagioclase are completely dissolved, while large white mica and chlorite grains crystallized. Also, the chlorite/white mica ratio is higher with temperature increase.

White mica is a main host for B, LILE and to smaller extent for Li. Plagioclase hosts the same elements but in lower concentrations. Chlorite is a main host for Li ± B and quartz hosts Li to smaller extent than chlorite and mica. Bulk rock analysis revealed partial loss in B, Rb, Sr and Cs with temperature increase, in contrast to the retention of Li and Ba. Mass balance based on trace element concentrations of individual phases and their proportion point to a reorganization of elements released during quartz and plagioclase dissolvement and phyllosilicate recrystallization: Rb, Cs and Ba released from plagioclase are incorporated in higher grade mica, Li released from mica and quartz is incorporated into chlorite. In the lack of newly formed phase as a host, B and Sr are probably released into a fluid.

The salinity at 250°C is around 2wt.% NaCl eq., i.e. lower than original pore-filling seawater. The freshening can be accounted for by smectite dehydration and transformation into illite. From 250 to 330°C, a salinity increase is observed, up to 3.5wt.%, possibly related to the chlorite crystallization requiring higher amount of water. The fluid is highly enriched in fluid-mobile elements in comparison with seawater. δ⁷Li values of fluid inclusion leachates are distinct for each locality: +8.1 to +17.07‰, in the Kodiak, +2.53 to +10.39‰ in the Shimanto belt and -1.54 to +9.54 ‰ in the western Alps. δ⁷Li of fluids is independent of other parameters, such as temperature or Li concentration.

Mineral reactions and fluid-mobile elements concentration in phases point to overall a local redistribution of fluid-mobile elements between phases, except for minor release of B and Sr. Lithium isotopes, which show that δ⁷Li of fluid is possibly buffered by host rock, confirm the fact that the rocks behaved to a large extent as a closed system during burial and subsequent exhumation.

How to cite: Rajic, K., Raimbourg, H., Richard, A., Lerouge, C., Millot, R., and Herviou, C.: Elemental and lithium isotopic signature of fluids in metapelites from ancient subduction zones, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11784, https://doi.org/10.5194/egusphere-egu22-11784, 2022.

Aqueous and saline fluids have a fundamental role in subduction zones and represent a major vector of mass transfer from the slab to the mantle wedge. In this setting, assessing the mobility of redox sensitive elements, such as iron, in aqueous fluids and melts is essential to provide insights on the oxygen fugacity conditions of slab-derived fluids and the oxidation state of arc magmas.

We experimentally investigate the solubility of magnetite and hematite in water-saturated haplogranitic melts, which represent the felsic melt produced by subducted eclogites. Experiments were conducted at 1–2 GPa and temperature ranging from 700 to 950 °C employing an endloaded piston cylinder apparatus. Single gold capsules were loaded with natural hematite, magnetite and synthetic haplogranite glass. Two sets of experiments were conducted: a first set with pure H₂O and a second set with a 1.5 m H₂O-NaCl solution. After quench, the presence of H₂O in the haplogranite glass was verified by Raman spectroscopy, while iron and major element contents were determined by electron microprobe analysis.

Results show that a significant amount of FeO is released from magnetite and hematite equilibrated with hydrous melts, up to 1.96 ± 0.04 wt% at 1 GPa and 950 °C. In the presence of NaCl, we observed an increase in the amount of iron in the haplogranite glass, e.g. from 1.04 ± 0.12 wt% to 1.50 ± 0.31 wt% of FeO_tot at 800 °C. These concentrations are substantially higher than the iron solubility in aqueous and saline fluids predicted by thermodynamic modelling (DEW model, Sverjensky et al., 2014), likely due to formation of Fe- and Si-bearing complex in the haplogranite-bearing fluid at run conditions. Our results suggest that hydrous melts can effectively mobilize iron from Fe-oxides even at relatively low-pressure conditions. Slab-derived hydrous melts can thus represent a valid agent for mobilizing iron from the subducting slab to the mantle wedge, and can strongly influence the geochemical cycles of Fe and the redox conditions of subduction zone fluids.

Sverjensky, D. A., Harrison, B. and Azzolini, D. (2014) Water in the deep Earth: The dielectric constant and the solubilities of quartz and corundum to 60kb and 1200°C, Geochim. Cosmochim. Acta, 129, 125–145

How to cite: Tiraboschi, C., Arno, R., Stephan, K., Jasper, B., and Carmen, S.-V.: Iron mobility in slab-derived hydrous silicate melts at sub-arc conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11854, https://doi.org/10.5194/egusphere-egu22-11854, 2022.

The slab-mantle interface is one of the most active sites of fluid-rock interaction, which affects the mass transfer and mechanical properties along subduction zone megathrust. However, the effects of CO₂ fluids and carbonation/decarbonation reactions on seismic activity are still poorly understood. In addition, although mantle peridotite is known as a large sink of CO₂, the nature of carbonation at mantle wedge condition remains unconstrained. In this study, we show the characteristics of carbonation of serpentinite body from the Sanbagawa metamorphic belt, Kanto Mountain, Japan [1]. The Higuchi serpentinite body (8 x15 m) is mainly composed of antigorite, and has not relics of olivine and pyroxenes. Massive antigorite parts are segmented by talc + carbonates (magnesite, dolomite and calcite) veins. At the boundary between serpentinite body and pelitic schists, actinolite-chlorite schist and chlorite rocks were formed. The location, depleted composition of Cr-rich spinel in the Higuchi body and temperature of ~400 ˚C of carbonation suggest that this body was originated from the leading edge of the mantle wedge. The carbon and oxygen stable isotope compositions of carbonates within the Higuchi body reveal that carbonic fluid was derived from carboniferous materials in sediments. Carbonation of serpentinite body is characterized by gains of CO₂, silica and Ca, and losses of H₂O and Mg. The thermodynamic calculations on mineral-fluid equilibria reveal that (1) the carbonic fluid produced under the oxidizing conditions (QFM +0.3) explains the systematic mineralogical variations within the Higuchi body, and that (2) carbonation of serpentinite proceeded with solid volume contraction, high fluid pressure and high mobility of Mg, which is largely consistent with the experimental carbonation at the mantle wedge condition [2]. This is consistent with the tree-like patterns of carbonate veins within the Higuchi body. Brittle failure to form carbonate veins was followed by a viscos flow of carbonate and talc. We infer that episodic infiltration of oxidizing fluids causes self-promoting carbonation of mantle wedge with solid volume change, which could affect the mechanical properties of slab-mantle interface.

[1] Okamoto, A, et al., 2021. Com Env Earth, 58, 4831-4839. doi.org/10.1038/s43247-021-00224-5

[2] Sieber et al. 2020. J. Petrol., 1-24. doi: 10.1093/petrology/egaa035

How to cite: Okamoto, A., Oyanagi, R., Yoshida, K., Uno, M., Shimizu, H., and Satish-Kumar, M.: Rupture of serpentinized mantle wedge by self-promoting carbonation: insights from Sanbagawa metamorphic belt, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13148, https://doi.org/10.5194/egusphere-egu22-13148, 2022.

The long-term global sea level depends on the balance of H₂O exchanges between the Earth's mantle and the surface through both volcanism (mantle degassing) and subduction of hydrous minerals (mantle regassing). The estimates of H₂O fluxes by the current thermopetrological subduction models predict that regassing exceeds degassing by 60%, which may lead to a sea-level drop of at least a hundred meters in the last 540 Ma [Parai & Mukhopadhyay, 2012, Earth Planet. Sc. Lett., 317, 396-406. https://doi.org/10.1016/j.epsl.2011.11.024. These models further imply a moderate ( Tg/Myr) global input of H₂O at the subduction trenches. In contrast, geological constraints suggest a near-steady state of long-term sea level while geophysical observations advocate for a larger global H₂O input, especially given the large amounts of hydrated lithospheric mantle that are inferred at present-day subduction trenches. To address this paradox, we revise the subduction-H₂O flux calculations using recently published experimental data on natural hydrated peridotites at high-pressure conditions, which suggest that all hydrated phases destabilize below 800˚C for pressures higher than 8 GPa [Maurice et al., 2018, Contrib. Mineral. Petrol, 173(10), 86. https://doi.org/10.1007/s00410-018-1507-9 ]. Our reassessed thermopetrological models show that a prominent global H₂O input ( Tg/Myr), mainly conveyed by the layer of subducted serpentinized mantle, is compatible with a limited global H₂O retention in subducted slabs at mid-upper mantle depths ( Tg/Myr), including in models that consider some worldwide variability of the input serpentine. We also show that the global H₂O retention at mid-upper mantle depths is only driven by the hydrated mantle of coldest subducting plates. Overall, our models show that the present-day global water retention in subducting plates beyond mid-upper mantle depths barely exceeds the estimations of mantle degassing, and thus quantitatively support the stable-sea level scenario over geological times.

How to cite: Arcay, D., Cerpa, N., and Padrón-Navarta, J. A.: Reconciling extensive mantle hydration at subduction trenches and limited deep H2O fluxes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13287, https://doi.org/10.5194/egusphere-egu22-13287, 2022.

Fluids are the primary agents for mass transfer in subduction zones. These fluids can be captured as primary inclusions within minerals crystallizing during subduction processes. Some of these inclusions, referred to as multiphase solid inclusions (MSI), are characterized by the high proportion and variety of minerals, hence by a high concentration of solute in the trapped fluid. Kotková et al. (2021) have described primary MSI in garnets of subduction-related ultra-high pressure (UHP) peridotites (P-T of 1030-1150 ºC/3.6-4.8 GPa) of the Bohemian Massif. MSI range in size between ≈5-40 µm and are mostly composed of hornblende, the barian mica kinoshitalite, dolomite and magnesite. MSI have been interpreted as trapped residual liquids produced after partial UHP crystallization of carbonate-silicate melts that now form garnet pyroxenite veins in the peridotites. Experimental re-melting of MSI is the best procedure to investigate the precise nature of trapped fluids. We have conducted re-melting experiments of MSI present in garnets of a lherzolite, taking the inclusions to P-T around their entrapment conditions at or close to host rock peak P-T, 4-4.5 GPa and 1000-1225 ºC. The inclusions (re-)crystallized into a garnet fringe at the boundary between inclusions and host garnet, barian mica and carbonatite melt towards the center of the inclusion, and a large irregular and empty space in between the garnet fringe and the central silicate-carbonate component. Microstructures and mass balance indicate that the empty space was occupied by a Na-K-Cl-F-rich saline aqueous fluid (brine). Hence experiments did not produce a single melt at any experimental conditions, but systematically show the stability and coexistence of barian mica + carbonatite melt + brine at the entrapment conditions, and a garnet fringe indicating reaction between trapped fluids and host garnet. This suggest that growing garnet trapped a carbonatite melt and a saline aqueous fluid coexisting in the matrix, together with solid crystals of barian mica likely produced by metasomatism of the percolating fluids through the host peridotite. It is intriguing, however, that neither single mica crystals nor separate former carbonate melt and brine have been found included in garnets. Mass balance shows that carbonate melt is the main host for incompatible elements such as Ba. This presentation will discuss the bearings of the experimental results on the nature and origin of these MSI, potential links to diamond formation and their implication on mass transfer processes in subduction zones.

Kotkova et al. (2021) Lithos 398-399, 106309

How to cite: Acosta Vigil, A., Kotková, J., Copjaková, R., Wirth, R., and Hermann, J.: Experimental constraints on the nature of multiphase solid inclusions and their bearing on mantle wedge metasomatism, Bohemian Massif, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13297, https://doi.org/10.5194/egusphere-egu22-13297, 2022.

The correlation of subducted plate parameters with generated volcanism was studied along the Kamchatka arc. Increased slab age controls dip angle (25-45^o) and length of the seismic zone (200-700 km slab depth)  from the north (~53⁰N) to the south (~49⁰N) of the Kamchatka arc. All listed above parameters generate various aged volcanic belts with different parameters of volcanism. The natural boundary between various aged slabs is on ~53⁰N, on the extension Avachinsky transform fault. It divides the Kamchatka arc on Southern Kamchatka with slab age ~ 103-105 Ma and Eastern volcanic belt, Central Kamchatkan Depression with slab age ~ 87-92 Ma. Complicated evolution and various ages of the slab control magmatism along the Kamchatka arc. Basic-intermediate magma compositions dominantly characterized Quaternary-Pliocene volcanoes in Central Kamchatkan Depression. In contrast, Neogene-Quaternary volcanism on Southern Kamchatka represents by strong explosions of acidic magmas (Gordeev, Bergal-Kuvikas, 2022).

Monogenetic volcanism marked a Malko-Petropavlovsk zone of transverse dislocations (MPZ), which is located on the extension Avachinsky transform fault. Monogenetic cinder cones in MPZ are randomly distributed along to these long-lived rupture zones. Here I present new geochemical and isotopic results of monogenetic volcanism in MPZ. Based on whole rock and trace element geochemistry, Pb-Sr-Nd isotopic ratios of monogenetic cinder cones magmas were shown to tap the enriched mantle source (low ¹⁴³Nd/¹⁴⁴Nd isotopic ratios (0.512959-0.512999), as variated ⁸⁷Sr/⁸⁶Sr (0.703356-0.703451) and ²⁰⁶Pb/²⁰⁴Pb (18.30-18.45), ²⁰⁸Pb/²⁰⁷Pb (38.00-38.12) isotopic ratios).  High Nb/Yb and La/Yb ratios, without significant inputs of the slab`s components (the lowest Ba, Th contents), indicate decompression melting predominately (Bergal-Kuvikas et al., 202X). Therefore, a combination of geophysical and geochemical methods enable us to conclude that monogenetic volcanism in MPZ   mark a natural boundary between various aged slab on Avachinsky transform fault. Various aged slabs under Southern Kamchatka and the Eastern volcanic belt generate volcanism with different magma compositions and ages of volcanoes.

This research was supported by Russian Science Foundation (grant number 21-17-00049,https://rscf.ru/project/21-17-00049/).

References

Bergal-Kuvikas O.V., Bindeman I.N., Chugaev A.V., Larionova Yu. O., Perepelov A.V., Khubaeva O.R. Pleistocene-Holocene monogenetic volcanism at Malko-Petropavlovsk zone of transverse dislocations on Kamchatka: geochemical features and genesis // Pure and Applied Geophysics. Special Issue: Geophysical Studies of Geodynamics and Natural Hazards in the Northwestern Pacific Region (in review)

Gordeev, E.I., Bergal-Kuvikas O.V. (2022). Structure of subduction zone and volcanism on Kamchatka. Doklady of the Earth Sciences. 2. 502. P. 26-30. 10.31857/S2686739722020086

How to cite: Bergal-Kuvikas, O.: Correlation slab heterogeneity and volcanism in Kamchatka arc, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-382, https://doi.org/10.5194/egusphere-egu22-382, 2022.

The subduction channel is located directly above a downgoing oceanic plate and forms by dehydration of this plate. The ascending water-rich fluids react with the mantle to hydrous minerals such as chlorite and amphibole. This process rheologically weakens the mantle and reduces its density so that an upwards-directed mass flow is continuously generated as long as the oceanic plate is subducted. However at great depth, the fluids ascending from the subducting plate do not produce hydrous minerals anymore due to too high pressure-temperature (P-T) conditions. Thus, the question arises how high can these conditions become in order to still generate such hydrous minerals in the mantle. To answer this question, thermodynamic modelling was undertaken with PERPLE_X using different data sets of Holland and Powell (1998, 2011), corresponding solid-solution models for relevant minerals, and the bulk-rock composition of a common lherzolite + 2.5 wt% H₂O. In addition, results of experiments at high pressure on the P-T stability of hydrous minerals such as chlorite were considered.

Under the assumption of a relatively steeply and fast dipping oceanic plate, the geothermal gradient at the interface between this plate and the overlying mantle wedge should be below 7.5 °C/km (100 km = 3.2 GPa). At such low gradients, that are common in modern subduction zones, chlorite is the only (nominally) hydrous mineral in the lherzolite considered because amphibole shows an upper pressure limit, for example 2.3 GPa using model cAmph(G), in the calculation results. Calculations with the data set of Holland and Powell (1998) lead to results at pressures >3 GPa, which are, due to the used equation-of-state for minerals, incompatible with experimental results, whereas the results produced with the more recent data set (Holland and Powell, 2011) are compatible. Along gradients of 7.5, 5, and 3.5 °C/km, chlorite decomposes to form garnet in lherzolite at about 740 (3.15 GPa), 660 (4.3 GPa), and 570 °C (5.3 GPa), respectively. These temperatures are 60-80 °C lower than calculated for the reaction of chlorite + enstatite = forsterite + pyrope + H₂O in the system MgO-Al₂O₃-SiO₂-H₂O.

The aforementioned P-T conditions limit the subduction channel towards great depths, which should be less than 160 km (5.2 GPa) even at very low thermal gradients, and are compatible with peak P-T conditions of many eclogites exhumed in the subduction channel from the surface of the downgoing oceanic plate. A few exceptions were reported which suggest exhumation of eclogite from depths > 200 km (e.g., Ye et al., 2000). The reason for these greater depths could be another exhumation mechanism. However, a misinterpretation of so-called exsolution lamellae in eclogitic minerals, taken as evidence for unusual mineral compositions and, thus, depths > 200 km, is more likely (see Liu and Massonne, 2022).

Holland, T.J.B., Powell, R., 1998. J. Metamorph. Geol. 16, 309-343.

Holland, T.J.B., Powell, R., 2011. J. Metamorph. Geol. 29, 333–383.

Liu, P., Massonne, H.-J., 2022. J. Metamorph. Geol., doi: 10.1111/jmg.12649

Ye, K., et al., 2000. Nature 407, 734–736.

How to cite: Massonne, H.-J.: The maximum depth of the subduction channel in modern subduction zones, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1293, https://doi.org/10.5194/egusphere-egu22-1293, 2022.

Subducting oceanic plates experience intense normal faulting during bending that accommodates the transition from horizontal to downward motion at the outer rise at subduction trenches. We investigated numerically the consequences of the plate bending on the mechanical properties of subducting slabs using 2D subduction models in which both brittle and ductile deformation, as well as grain size evolution, are tracked and coupled self-consistently. Numerical results suggest that pervasive brittle-ductile slab damage and segmentation can occur at the outer rise region and under the forearc that strongly affects subsequent evolution of subducting slabs in the mantle. This slab-damage phenomenon explains the subduction dichotomy of strong plates and weak slabs, the development of large-offset normal faults near trenches and the occurrence of segmented seismic velocity anomalies and interfaces imaged within subducted slabs. Furthermore, brittle-viscously damaged slabs show a strong tendency for slab breakoff at elevated mantle temperatures that may have destabilized continued oceanic subduction and plate tectonics in the Precambrian (Gerya et al., 2021).

Gerya, T.V., Bercovici, D., Becker, T.W. (2021) Dynamic slab segmentation due to brittle-ductile damage in the outer rise. Nature, 599, 245-250.

How to cite: Gerya, T., Bercovici, D., and Becker, T.: Segmentation of subducting oceanic plates by brittle-ductile damage, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2400, https://doi.org/10.5194/egusphere-egu22-2400, 2022.

Plate kinematics in the vicinity of subduction zones, as well as seismic tomography provide insights into the deep dynamics of subducting slabs. Velocities at which subducting plates are consumed at the trench (the subduction velocities) typically exceed 3–4 cm/yr at present-day. Absolute trench velocities (relative to a lower-mantle reference frame) are lower, between -2 and 2 cm/yr [Heuret and Lallemand, 2005]. This implies that the “accommodation space” created by the slab rollback associated with lateral trench migration is not nearly sufficient for accommodating the length of incoming slab in the horizontal dimension. In the vertical dimension, even the fastest estimates for slab sinking rates over long time scales amount to only a fraction of 3–4 cm/yr [Butterworth et al. 2014, van der Meer et al. 2010, Sigloch & Mihalynuk 2013]. Hence the rates at which the lithosphere typically subducts cannot be accommodated by fast vertical sinking either. Seismic tomography confirms the “traffic jam” conditions for slabs in the mantle that are implied by these numbers, with slab thickening imaged in and beneath the mantle transition zone (MTZ). These highly visible, thickened, slabs have been interpreted as the result of folding [Ribe et al., 2007], and their relative localization (massive,  near-vertical “slab walls”) supports the notion of near-stationary trenches over long time scales [Sigloch and Mihalynuk, 2013]. 

Buoyancy-driven analog and numerical models of subduction have commonly produced subduction and trench velocities that differ from the first-order observations above. Their subduction velocities typically drop below 1-2 cm/yr once the modelled slab enters the high-viscosity lower mantle, and their trench migration velocities remain almost equal to subduction velocities, thus accommodating the slab mainly in the horizontal direction. In addition, these models tend to produce trench retreat and slab “rollback” , unless the latter is very weak and/or the overriding plate is very strong [Goes et al., 2017]. These modelling results have led to the conclusion that near-vertical slab sinking and folding at the MTZ is an end-member regime restricted to very specific subduction set-ups. 

We have added a weak asthenospheric layer to typical 2-D thermo-mechanical models of subduction zones with a complex rheology [e. g., Garel et al., 2014], which partly reconciles the models and the observations. A weak asthenosphere appears as an intuitive candidate for increasing subduction velocity because a reduced mantle drag at the base of the subducting plate lowers the mantle’s resistance to the plate’s trench-ward motion. We further found that the models with a weak asthenospheric layer lessens the trench motion and thus tend to produce prominent vertical folding of slabs at the MTZ. Subduction velocities remain higher than trench velocities long after the slab reaches the MTZ, so that 300-to-400-km wide “slab walls” are continuously produced in the lower mantle over a relatively wide range of model parameters. The presence of a weak asthenosphere has often been speculated to explain seismic properties beneath oceanic plates, but seldom modelled. This study contributes to a quantification of its potential effects on subduction dynamics. 

How to cite: Cerpa, N., Sigloch, K., Garel, F., Davies, R., and Heuret, A.: Subduction dynamics through the mantle transition zone in the presence of a weak asthenospheric layer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3822, https://doi.org/10.5194/egusphere-egu22-3822, 2022.

Double seismic zones (DSZs), parallel planes of intermediate-depth earthquakes inside oceanic slabs, have been observed in a number of subduction zones and may well be a ubiquitous feature of downgoing oceanic plates. Early focal mechanism observations from Japan and Alaska have shown downdip compressive events in the upper and downdip extensive events in the lower plane of the DSZ, which was interpreted as a signature of plate unbending at these depths. Such a pattern of compressive over extensive events has become a hallmark of DSZ seismicity, and some models of DSZ seismogenesis explicitely rely on an unbending-dominated intraslab stress field as a mechanism for deep slab hydration.

In this study, we show that the intraslab stress field in the depth range of DSZs is much more variable than previously thought. Compiling DSZ locations and mechanisms from literature, we observe that the “classical” pattern of compressive over extensive events, as in NE Japan, is only observed at about half of the DSZ locations around the globe. The occurrence of extensive mechanisms across both planes accounts for most other regions, whereas a “bending signature” of extensive over compressive events is not widely observed at all. To obtain an independent estimate of the (un)bending state of slabs at intermediate depths, we compute (un)bending estimates from slab geometries taken from the slab2 compilation of slab surface depths. We find no clear prevalence of slab unbending at intermediate depths, and the occurrence of DSZ seismicity does not appear to be limited to regions of slab unbending. Taking high-resolution focal mechanism information from the Northern Chile subduction zone as an example, we conclude that the intraslab stress field in subduction zones is primarily a superposition of (un)bending stresses and downdip extensive in-plane stresses. Depending on the sign (bending or unbending) and the relative contributions of these two principal stresses, an unbending signature as in NE Japan or a purely extensive pattern of focal mechanisms as in Northern Chile can emerge. We also consider possible additional contributing stresses that may further modify the intraslab stress field, such as friction along the plate interface and volume loss due to metamorphic phase changes.

How to cite: Sippl, C., John, T., Schmalholz, S., and Dielforder, A.: Global compilation of double seismic zones and their dependence on the intraslab stress field, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4233, https://doi.org/10.5194/egusphere-egu22-4233, 2022.

Conversion of a passive margin, which is the transition between oceanic and continental lithosphere formed by sedimentation above an ancient rift, into an active converging plate boundary is still ambiguous. According to the Wilson Cycle (Wilson, 1966), which describes the repeated opening and closing of the oceans, the collapse of a passive margin is a key factor in the closing phase of the Wilson Cycle. However, the lack of any Cenozoic examples of conversion of passive margins into subduction zones and the existence of old oceanic plates along Atlantic passive margins indicate the difficulty of subduction initiation at passive margins. Due to lack of observational evidence, modeling studies play a key role in understanding the kinematics and dynamics of transforming a passive into active margin. During the last decades, they proposed several facilitating mechanisms to collapse a passive margin such as sediment loading (Cloetingh et al., 1982), water weakening (Regenauer-Lieb et al., 2001), STEP faults (Subduction-Transform-Edge-Propagator; Govers and Wortel, 2005) near passive margins (Baes et al., 2011), mantle suction forces derived from detached slabs and/or neighboring subduction zones (Baes and Sobolev, 2017), convergence forces induced from neighboring plates (Zhong and Li, 2019) and propagation of subduction along passive margins (Baes and Sobolev, 2017; Zhou et al., 2020).

 In this study, we extend the work of  Baes and Sobolev (2017) by using 3D models. As breaking a 3D lithosphere is more difficult than a 2D plate, 3D numerical models may lead to different conclusions than those of 2d ones. To study the effect of mantle suction flow on the destabilisation of passive margins, we set up 3D models, using the ASPECT finite element code (Kronbichler et al., 2012). We investigate the effect of different parameters such as the magnitude, spatial size and location of suction flow, the age of oceanic lithosphere and the existence of a STEP (Subduction-Transform-Edge-Propagator; Govers and Wortel, 2005) fault near margin. Our preliminary results show over-thrusting of continental crust from the earliest stage of deformation. This continued over-thrusting along with suction force, which imposes shear stresses below the lithosphere, causes breaking of the oceanic plate and its sinking into the mantle and eventually subduction initiation at the passive margin. The time of subduction initiation, which depends on several factors such as magnitude and location of the suction force, is more than 30 Myr indicating difficulty in the converting passive margins into converging plate boundaries. We believe that subduction initiation at some Atlantic passive margins such as those in the north of the South Sandwich subduction zone, southwest of the Iberia and north of the Caribbean region, where considerable suction forces induced by sinking slabs or neighboring subduction zones are available, will occur in a few tens of million years.

References:

Baes et al., 2011. Geophys. J. Int.

Baes, and Sobolev, 2017. Geochem. Geophys. Geosyst.

Cloetingh et al., 1982. Nature.

Govers and Wortel, 2005, Earth Planet. Sci. Lett.

Kronbichler et al., 2012, Geophys. J. Int.

Regenauer-Lieb et al., 2001. Sci.

Wilson, 1966, Nature

Zhou et al., 2020. Sci. Adv.

Zhong and Li, 2019. Geophys. Res. Lett.

How to cite: Baes, M., Sobolev, S., Hampel, A., and Glerum, A.: 3D numerical modeling of suction-induced subduction initiation at passive margins, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4261, https://doi.org/10.5194/egusphere-egu22-4261, 2022.

Volatiles play a pivotal role in subduction zones dynamics, associated geological hazards and mineralization, yet their pathways remain partially understood. The Lesser Antilles subduction zone can yield insights to volatile recycling as a global end-member, where old oceanic lithosphere formed by slow spreading slowly subducts. Here we use seismograms from local earthquakes recorded by a temporary deployment of ocean-bottom seismometers in the fore- and back-arc during the VoiLA (Volatile Recycling in the Lesser Antilles) experiment to characterize the 3-D properties of the slab, back-arc and mantle wedge in the north-central Lesser Antilles subduction zone. Along the top of the slab, defined by the underlying Wadati-Benioff seismicity, we find low P-wave velocity extending to 130–150 km depth, deeper than expected for magmatic oceanic crust. The deep low velocities together with high Vp/Vs at 60–80 km and 120–150 km depth are consistent with a significantly tectonised and serpentinised slab top, as expected for lithosphere formed by slow spreading. The most prominent high Vp/Vs anomalies in the slab correlates with two projected fracture zones and the obliquely subducting boundary between Proto-Caribbean and Equatorial Atlantic lithosphere, indicating these structures enhance hydration of the oceanic lithosphere and subsequent dehydration when subducted. Deep dehydration of slab mantle serpentinite is evidenced by high Vp/Vs anomalies in the back-arc offshore Guadeloupe and Dominica. Right above the slab, the asthenospheric mantle wedge is imaged beneath the back-arc as high Vp/Vs and moderate Vp feature, indicative for fluids rising from the slab through the overlaying cold boundary layer. The fluids might be dragged down with the subducting slab before rising upwards to induce melting further to the west. The variation in seismic properties along the subducting slab and in the back-arc mantle wedge shows that the changes in hydration of the incoming plate govern the dehydration processes at depth. The highest Vp/Vs anomaly in the back-arc west of Dominica at depth greater than 120 km, together with the anomaly at 60–80 km depth on the slab east of the island, appear to track the source and path of excess volatiles that may explain the relatively high magmatic output observed on the north-central islands of the Lesser Antilles arc.

How to cite: Bie, L., Hicks, S., Rietbrock, A., Goes, S., Collier, J., Rychert, C., Harmon, N., and Maunder, B. and the VoiLA Consortium: Fluid migration, deep dehydration, and melt generation in the Lesser Antilles subduction zone, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4399, https://doi.org/10.5194/egusphere-egu22-4399, 2022.

Intermediate-depth earthquakes in many subduction zones occur in two distinct layers, forming an upper and a lower seismic zone separated vertically by an aseismic or weakly seismic region. These Double Seismic Zones (DSZs) have been related to dehydration reactions in the downgoing crust and mantle lithosphere. Notably, intermediate-depth seismicity in Northern Chile shows a pattern of intraslab seismicity which is quite different from a conventional DSZ. Here, two parallel seismicity planes are present in the updip part of the slab, but at a depth of ∼80–90 km, there is a sharp transition to a highly seismogenic volume of 25–30 km thickness, which corresponds to a closing of the gap between the two seismicity planes.

While such an observation is unique to Northern Chile, understanding the processes behind the formation of this feature should provide important constraints on the mineral processes that govern seismicity in DSZs as well as the role and involvement of fluids. As seismic velocities contain important information about mineralogy and fluid content, we aim at a high-resolution characterization of the seismic wavespeeds of the Northern Chile subduction zone, mainly focusing on the downgoing Nazca slab. We use the seismicity catalog of Sippl et al. (2018) that contains >100,000 earthquakes and 1,200,404 P- and 688,904 S-phase picks for the years 2007 to 2014 to perform local earthquake tomography using the FMTOMO algorithm (Rawlinson et. al., 2006). Data from the seismic stations of the permanent IPOC (Integrated Plate boundary Observatory Chile) deployment in the Northern Chile forearc form the backbone of the dataset, but are complemented by several temporary deployments that span shorter time sequences.

We will present first 3D models of P- and S-wavespeeds from the Northern Chile forearc between about 19°S and 23°S, using a subset of the earthquake catalog mentioned above, as well as images of ray coverage, relocated seismicity and synthetic resolution tests.

The presented seismic velocity distribution will eventually be compared with theoretical wavespeeds that are forward calculated assuming different mineralogical compositions in order to narrow the range of possible reactions that may be occurring at depth.

How to cite: Hassan, N. and Sippl, C.: Towards imaging dehydration reactions in the downgoing Nazca plate with local earthquake tomography, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4461, https://doi.org/10.5194/egusphere-egu22-4461, 2022.

Subduction invasion has been referred to as the process by which subduction zones from a subducting ocean invade or trigger subduction initiation in a contiguous ocean. This can, in principle, happen in different ways that can vary from a direct migration by rollback along an oceanic corridor connecting the two oceans (e.g., the Gibraltar Arc into the Atlantic) or by polarity reversal across a narrow continental land bridge, potentially involving the collision of an ocean plateau with the pre-existent trench (the Scotia and the Caribbean arcs). This process is important because new subduction zones are difficult to start in the present plate tectonics context and most known examples of initiation seem to be forced by pre-existent subduction zones. The problem is that in internal Atlantic-type oceans there are no pre-existent subduction zones, and therefore, they must be introduced from the outside. Luckily, the Atlantic seems to be just passing through a phase of invasion, as evidenced by the three referred examples. But while the Caribbean and the Scotia arcs are already two fully formed Atlantic-subduction systems, the Gibraltar Arc is currently in the process of migrating between oceanic basins. In the future, the Arc can evolve according to two different scenarios. In the first, the Gibraltar Arc is stuck between Africa and Iberia and the subduction is waning. In the other scenario, after a period of quiescence, the arc manages to go through and invade the Atlantic. In order to understand which is more feasible, we have developed 3D numerical models using the code LaMEM to gain some insights into how this system may evolve. We have simulated the development of the Mediterranean arc-back-arc system, with rollback and the retreat of the subduction zones in a fully dynamic framework (no active kinematic boundaries). Our model shows that under the studied parameters, the Gibraltar subduction zone manages to invade the Atlantic, even in the cases of a very narrow oceanic corridor. However, this led to a very significant decrease in the subduction velocity, suggesting that in the natural prototype, a period of quiescence is expected before the Mediterranean subduction zone manages to go through and invade the Atlantic.

J.C. Duarte and F.M. Rosas acknowledge financial support by FCT through the project UIDB/50019/2020 – Instituto Dom Luiz (IDL)

How to cite: Duarte, J. C., Riel, N., Kaus, B. J. P., and Rosas, F. M.: Subduction invasion of the Atlantic by Mediterranean subduction zones, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4774, https://doi.org/10.5194/egusphere-egu22-4774, 2022.

The structure of oceanic back-arc basins reflects the dynamics of the subduction zone they are associated with. Often, the basement of these basins is not only composed of oceanic crust, but also of exhumed mantle, fragments of continental crust, intrusive magmatic bodies, and a complex mid-ocean ridge system characterised by distinct relocations of the spreading centre. These features are a direct consequence of the transient nature of subduction zones. Here, we show results from different types of numerical models that aim at understanding how back-arc basins are shaped by subduction dynamics.

We present 3D numerical models of back-arc spreading centre jumps evolving naturally in a homogeneous subduction system surrounded by continents without a trigger event (Schliffke et al., 2022). We find that jumps to a new spreading centre occur when the resistance on the boundary transform faults enabling relative motion of back-arc and neighbouring plates is larger than the resistance to break the overriding plate closer to trench. Time and distance of spreading centres jumps are, thus, controlled by the ratio between the transform fault and overriding plate strengths. We also present results from 2D numerical models of lithospheric extension with asymmetric and time-dependent boundary conditions that simulate multiple phases of extension due to episodic trench retreat (Magni et al., 2021). We show that multiphase extension can result in asymmetric margins, mantle exhumation and continental fragment formations. We find that the duration of the first extensional phase controls the final architecture of the basin. Finally, we show that our models can explain many features observed in present-day and extinct back-arc basins.

Magni, V., Naliboff, J., Prada, M., & Gaina, C. (2021). Ridge Jumps and Mantle Exhumation in Back-Arc Basins. Geosciences, 11(11), 475.

Schliffke, N., van Hunen, J., Gueydan, F., Magni, V., & Allen, M (2022). Episodic back-arc spreading centre jumps controlled by transform fault to overriding plate strength ratio. Accepted for publication in Nature Communications.

How to cite: Magni, V., Schliffke, N., van Hunen, J., Gueydan, F., Allen, M., Naliboff, J., Prada, M., and Gaina, C.: Modelling ridge jumps in back-arc basins at different scales, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4810, https://doi.org/10.5194/egusphere-egu22-4810, 2022.

Although many different mechanisms for subduction initiation have been proposed, few of them are viable in terms of agreement with observations and reproducibility in numerical experiments. In particular, it has recently been demonstrated that intra-oceanic subduction triggered by an upwelling mantle plume could contribute greatly to the onset and functioning of plate tectonics in the early Earth and, to a lesser extent, in the modern Earth. In contrast, the onset of intracontinental subduction is still underestimated. Here we review 1) observations demonstrating the upwelling of hot mantle material flanked by sinking proto-slabs of the continental mantle lithosphere, and 2) previously published and new numerical models of plume-induced subduction initiation. Numerical modelling shows that under the condition of a sufficiently thick (> 100 km) continental plate, incipient down thrusting at the level of the lowermost lithospheric mantle can be triggered by plume anomalies with moderate temperatures and without significant strain and/or melt-induced weakening of the overlying rocks. This finding is in contrast to the requirements for plume-induced subduction initiation in oceanic or thin continental lithosphere. Consequently, plume-lithosphere interactions in the continental interior of Paleozoic-Proterozoic (Archean) platforms are the least demanding (and therefore potentially very common) mechanism for triggering subduction-like foundering in Phanerozoic Earth. Our findings are supported by a growing body of new geophysical data collected in a variety of intracontinental settings. A better understanding of the role of intracontinental mantle downthrusting and foundering in global plate tectonics and, in particular, in triggering "classic" oceanic-continental subduction will benefit from further detailed follow-up studies.

How to cite: Cloetingh, S., Koptev, A., Kovacs, I., Gerya, T., Beniest, A., Willingshofer, E., Ehlers, T., Andric-Tomasevic, N., Botsyun, S., Eizenhofer, P., Francois, T., and Beekman, F.: Plume-induced sinking of the intracontinental lithosphereas a fundamentally new mechanism of subduction initiation., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4976, https://doi.org/10.5194/egusphere-egu22-4976, 2022.

The 660-km seismic discontinuity (D660) is the boundary between the Earth’s lower mantle and transition zone and is commonly interpreted as the dissociation of (Mg,Fe)₂SiO₄ ringwoodite to (Mg,Fe)SiO₃ bridgmanite plus (Mg,Fe)O ferropericlase (post-spinel transition). Prominent features of D660 are significant depressions to 750 km and multiplicity beneath cold subduction zones. Previous high-pressure experiments provided negative but gentle Clapeyron slopes (−1.3 to −0.5 MPa/K) of the post-spinel transition. Thus, the post-spinel transition cannot interpret the D660 depression. Therefore, another phase transition with a steep negative slope is required, and the akimotoite−bridgmanite transition in (Mg,Fe)SiO₃ is one candidate.

In the current study, we determined the boundaries of the post-spinel (RBP) and akimotoite−bridgmanite (AB) phase transitions in the MgO-SiO₂ system over a temperature range of 1250–2085 K using advanced multi-anvil techniques with in situ X-ray diffraction. We judged a stable phase assemblage by observing relative increase/decrease in the ratio of coexisting high- and low-pressure assemblages at spontaneously and gradually decreasing pressure and a constant temperature from diffraction intensities. Since this strategy is strictly based on the principle of phase equilibrium, it excludes problems in determining phase stability caused by sluggish kinetics and surface energy.

We found that the RBP boundary has a slightly concave curve, whereas the AB boundary has a steep convex curve. The RBP boundary is located at pressures of 23.2–23.7 GPa in the temperature range of 1250–2040 K. Its slope varies from −0.1 MPa/K at temperatures less than 1700 K to −0.9 MPa/K at 2000 K with an averaged value of −0.5 MPa/K. The slope of the AB boundary gradually changes from −8.1 MPa/K at low temperatures up to 1300 K to −3.2 MPa/K above 1600 K. Based on these findings, we predict that, beneath cold subduction zones, ringwoodite should first dissociate into akimotoite plus periclase, and then akimotoite transforms to bridgmanite with increasing depth; these successive transitions cause the multiple D660. Moreover, the steep negative boundary of the AB transition should result in cold-slab stagnation due to significant upward buoyancy. Our predictions are supported by the seismological observations beneath cold (e.g., Tonga, Izu-Bonin) subduction zones.

How to cite: Chanyshev, A., Ishii, T., Bondar, D., Bhat, S., Kim, E. J., Farla, R., Nishida, K., Liu, Z., Wang, L., Nakajima, A., Yan, B., Tang, H., Chen, Z., Higo, Y., Tange, Y., and Katsura, T.: Depressed 660-km seismic discontinuity beneath cold subduction zones caused by akimotoite-bridgmanite phase transition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5045, https://doi.org/10.5194/egusphere-egu22-5045, 2022.

Subduction zones provide a key link between the surficial biogenic, atmospheric and hydrospheric geochemical cycles with the Earth’s internal reservoirs. Sediment compaction and dehydration of variably altered oceanic lithosphere during subduction release volatile species (containing e.g., S, H, C, N) to the overlying mantle wedge. In particular, sulfur plays a key role in the formation of porphyry ore deposits and has a major control on redox processes in subduction zones, given it occurs in variable oxidation states from oxidized sulfate (S⁶⁺) to reduced sulfide (S^2-). Here we studied samples from a contact between serpentinite and partly metasomatized eclogitic metagabbros in the Voltri Massif (Italy). We determined the bulk rock and in situ sulfur isotope composition of pyrite grains and combined this with detailed mineralogic and petrologic investigations. Along the serpentinite-metagabbro contact, the metagabbros are metasomatized to actinolite-chlorite schists and metagabbros rich in epidote and Na- and Na-Ca amphiboles. The serpentinites as well as the actinolite-chlorite schists along the serpentinite-metagabbro contact have very low sulfide contents and provide evidence for the oxidation of sulfides, including formation of Fe-oxides. Sulfur input from the serpentinite-metagabbro contact towards the less metasomatized eclogitic metagabbros is observed. This sulfur input is reflected by bulk rock δ³⁴S values that increase from initially around +1.5‰ in samples distant from the contact to +7.3 to +12.5‰ in samples near the contact. This trend correlates with a general increase in the in situ δ³⁴S values from core to rim of individual pyrite grains. Distinct Co and Ni growth zones in pyrite and variations in the in situ δ³⁴S values indicate multiple phases of pyrite growth during subduction and exhumation of these rocks, with the last stage of pyrite growth clearly related to Mg-metasomatism along the serpentinite-metagabbro contact. Thus, this study provides new insight into processes of sulfur migration during metasomatism of gabbroic rocks within the subducting slab and at the slab–mantle interface.

How to cite: Schwarzenbach, E., Streicher, L., Dragovic, B., Scicchitano, M. R., Wiechert, U., Codillo, E., Klein, F., Marschall, H., and Scambelluri, M.: Sulfur transfer along a metasomatized serpentinite-metagabbro contact in the Voltri Massif, Italy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5283, https://doi.org/10.5194/egusphere-egu22-5283, 2022.

The nature of the shortening of the Central Andes has been a matter of debate. The South American plate is advancing westwards forcing the subducting Nazca plate to roll back and the trench to retreat. But as the trench slowed its retreat the Andean mountain belt formed. This decrease of trench velocity has been attributed to the anchoring of the slab, but this process cannot explain the observed pulsatile behaviour of the shortening rate. Indeed, whereas the formation of the Central Andes started ~50 Ma ago, most of the shortening and elevation growth, including the formation of the Altiplano-Puna plateau, took place in two pulsatile steps at 15 Ma and 7 Ma as recognized from geological data. Thus we hypothesize that the deformation of the Central Andes is controlled by the subduction dynamics and a complex interaction between the overriding and subducting plates.

We used the FEM geodynamic code ASPECT to develop a self-consistent subduction E-W-oriented 2D high-resolution geodynamic model along the Altiplano-Puna plateau (21°S). This model incorporates the flat slab subduction episode at 35 Ma and follows the evolution of the lithospheric deformation. Our model results reproduced the observed spatial and temporal variations of tectonic shortening in Central Andes.

Three main conditions related to the plate interaction are of key importance to explain the observed shortening rate evolution in Central Andes. Firstly, the subduction dynamics affects the trench migration: each episode of slab steepening is followed by the blocking of the trench. The steepening occurs after the flat slab and at the end of two slab-buckling instabilities at 15 Ma and at 7 Ma. The second relevant process is the weakening of the overriding plate. This is ensured by the partial removal of a part of the lithospheric mantle after the re-steepening of the flat slab at 35 Ma and by weakening of the sediments in the Subandean Ranges after 10 Ma. Thirdly, a relatively high interplate friction coefficient (~0.05) is needed to ensure the stress transfer from the slab to the overriding plate, which is further enhanced by the delaminated mantle lithosphere eventually blocking the subduction corner flow.

The pulses of shortening rate occur at the end of each slab-buckling cycle when the trench is blocked. The deformation of the overriding plate is intensified by the eclogitization of the lower crust and the subsequent delamination of the sublithospheric mantle. Finally, at ~10 Ma, the deformation switches from pure-shear to simple-shear shortening, after the underthrusting of the Brazilian craton in presence of weak foreland sediments. 

How to cite: Pons, M., Sobolev, S., Liu, S., and Neuharth, D.: Variability of the shortening rate in Central Andes controlled by subduction dynamics and interaction between slab and overriding plate., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5284, https://doi.org/10.5194/egusphere-egu22-5284, 2022.

Subduction is the main driver of tectonic activity on Earth. Termination of subduction is followed by diverse and unexpected tectonic activity, such as anomalous magmatism, exhumation, subsidence and subsequent rapid uplift. What fundamentally drives these processes remain enigmatic. A prime example of subduction termination can be found in northern Borneo (Malaysia), where subduction ceased in the late Miocene and was followed by puzzling tectonic activity, as reconstructed from geological and petrological evidence. Our current understanding of the subduction cycle cannot be reconciled with evidence of post-subduction tectonics in both the near-surface geology and mantle of northern Borneo.

We use new passive-seismic data to image at unprecedent detail a sub-vertical lithospheric drip that developed as a Rayleigh-Taylor gravitational instability from the root of a volcanic arc, which formed above a subducting plate. We use thermo-mechanical simulations to reconcile these images with time-dependent dynamical processes within the crust and underlying mantle, following subduction termination. Our model predictions illustrate how significant extension from a downwelling lithospheric drip can thin the crust in an adjacent orogenic belt, causing lower crustal melting and possible exhumation of subcontinental material, which can explain core-complex formations seen in other areas of recent subduction termination.

How to cite: Pilia, S., Davies, R., Hall, R., Bacon, C., Gilligan, A., Greenfield, T., Tongkul, F., and Rawlinson, N.: Effects of subduction termination processes on continental lithosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5344, https://doi.org/10.5194/egusphere-egu22-5344, 2022.

Slab detachment causes a reorganization of the forces acting on orogenic systems and can have a distinctive signature in the geological record that may be identified through the structural,  metamorphic and topographic evolution of the orogen. However, this signature is hidden within other signals relating to the general complexity of the mountain building processes. In addition, slab detachment (or slab tearing in 3D) is a complex process that occurs on different timescales as a function of the inherent rheological properties of the lithosphere and the weakening mechanism occurring within the slab (viscous, plastic or thermal weakening).

How these properties affect the slab detachment process and to which extent these controls are reflected in the topograhic evolution of the orogenetic system is not yet fully understood. As slab detachment may occur at different depths and rates, it has different effects on the overall pull force acting on the orogen and on its post-detachment response.

Here, we employ 2D numerical experiments to systematically explore first order controls on slab detachment (slab rheology, geometry and weakening mechanisms) and the corresponding topographic evolution. Apart from the effect of lithosphere rheology and weakening mechanisms, we put particular focus on the effects of plate coupling and breakoff depth.

How to cite: Piccolo, A. and Thielmann, M.: Controls on slab detachment and subsequent topography evolution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7483, https://doi.org/10.5194/egusphere-egu22-7483, 2022.

The subduction of seamounts and its accompanying crustal deformation of the overriding plate is thought to have a large effect on the occurrence of megathrust earthquakes. Subducted seamounts can generally only be observed using seismic-reflection studies, which have shown that seamounts can subduct intact down to 30-40 km depth. On the other hand, there is evidence for accreted seamounts in e.g. the Costa Rica and Makran subduction zones. Because such observations only provide snapshots in space and time, little is still known about the exact evolution of seamount subduction and its effect on overriding-plate deformation and subduction zone seismicity through time. We investigate the different styles of seamount subduction and how these influence seismicity and overriding plate deformation. We use seismo-thermo-mechanical (STM) models with a visco-elasto-plastic rheology simulating seamount subduction over millions of years in a 2D realistic subduction setting. The momentum, mass and energy equations are solved and a strongly slip rate dependent friction allows for the spontaneous development of faults. The use of a realistic rheology allows us to evaluate faulting patterns and the state of stress in the overriding plate caused by seamount subduction. We find three scenarios for seamount subduction by varying the rock properties cohesion (C) and pore fluid pressure ratio (λ): (1) cutting off of the seamount at the trench leading to frontal accretion; (2) intact subduction through the trench, followed by flattening and stretching of the seamount; and (3) intact subduction of the seamount until seismogenic depths. Scenario’s 1 and 2 are most common, while scenario 3 only occurs under a limited range of material parameters. Particularly, a cohesion of the seamount and upper oceanic crust larger than 20 MPa is required for intact seamount subduction. Decreasing λ on locations with ample amounts of fluids increases the strength of the sediments, upper oceanic crust and seamount, but does not lead to intact seamount subduction. Subduction scenario’s 2 and 3 show more crustal deformation and seismicity within the fore-arc than subduction of a smooth interface (scenario 1 and models without a seamount). Seismicity patterns are also affected by λ and C. A low λ results in shorter and shallower megathrust ruptures and higher cohesions decrease the recurrence interval. Furthermore, the seamount itself introduces more frequent nucleation of smaller events at its edge.

How to cite: Fonteijn, M., van Rijsingen, E., and van Dinther, Y.: Styles of seamount subduction and overriding plate deformation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8243, https://doi.org/10.5194/egusphere-egu22-8243, 2022.

The role of subducted fluids on the generation of deep earthquakes (300 – 700 km) has been a topic of much research and debate for decades. While fluids are commonly believed to play a role in the genesis of intermediate depth earthquakes (70 – 300 km), it is often argued that fluids (i.e., water- or carbonate-bearing) cannot be transported to sufficient depth to play a role in the triggering or propagation of deep earthquakes. However, recent investigations show evidence of up to ~1.5 wt% water in a ringwoodite inclusion in a diamond from the mantle transition zone [1]. Additionally, heavy iron (δ⁵⁶Fe = 0.79–0.90‰) and unradiogenic osmium (187Os/188Os = 0.111) isotopic compositions of metallic inclusions in sublithospheric diamonds trace the pathway of serpentinized slabs from the trench to the top of the lower mantle [2]. Given this evidence for slab derived fluids at transition zone depths, we investigate the ability of fluids to reach these depths in subducted slabs by compiling a) new subduction zone thermal models, b) slab earthquake locations within these modeled subduction zones, and c) phase relations of hydrated or carbonated mantle peridotite and basaltic crust. Our results show a distinctive pattern that is consistent with the necessity of fluids in the generation of deep seismicity [3]. Specifically, those slabs capable of transporting water to the bottom of the transition zone (via dense hydrous magnesium silicates (DHMS)) produce earthquakes at transition zone depths. Conversely, virtually all slabs that do not transport water to these depths do not generate deep earthquakes. We also note that the depths of deep earthquakes coincide with the P/T conditions at which oceanic crust is predicted to intersect the carbonate-bearing basalt solidus to produce carbonatitic melts. We suggest that hydrous and/or carbonated fluids released from subducted slabs at these depths lead to fluid-triggered seismicity, fluid migration, diamond precipitation, and inclusion crystallization. Deep focus earthquake hypocenters would then track the general region of deep fluid release and migration in the mantle transition zone [3].

[1] Pearson, D. G., Brenker, F. E., Nestola, F., Mcneill, J., Nasdala, L., Hutchison, M. T., et al. (2014). Hydrous mantle transition zone indicated by ringwoodite included within diamond. Nature, 507, 221–224. https://doi.org/10.1038/nature13080 [2] Smith EM, Ni P, Shirey SB, Richardson SH, Wang W, and Shahar, A (2021) Heavy iron in large gem diamonds traces deep subduction of serpentinized ocean floor. Science Advances 7: eabe9773 https://doi.org/10.1126/sciadv.abe9773 [3] Shirey SB,  Wagner LS, Walter MJ, Pearson DG, and van Keken PE (2021) Slab Transport of Fluids to Deep Focus Earthquake Depths – Thermal Modeling Constraints and Evidence From Diamonds. AGU Advances: 2, e2020AV000304.    https://doi.org/10.1029/2020AV000304

How to cite: Wagner, L., Shirey, S., Walter, M., Pearson, D. G., and van Keken, P.: The role of subducted fluids on the genesis of deep earthquakes: evidence from deep diamonds and subduction zone thermal modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8968, https://doi.org/10.5194/egusphere-egu22-8968, 2022.

Significant Mo mobility and isotope (δ^98/95Mo) fractionation is induced during prograde metamorphism at present-day subduction zones. Depending on the redox conditions during early subduction and accompanied slab dehydration, isotopically heavy Mo is released towards the overlying mantle wedge, leaving behind a depleted, and isotopically light subducted slab. This isotopically light Mo signature has been detected in slab-melt influenced volcanic rocks and potentially will be traceable in ocean-island basalts, if their geochemical signatures are affected by previously subducted lithologies (i.e. slab and overlying sediments). Thus, the isotope composition of mantle plume-influenced volcanic rocks might reveal the nature of subducted and re-incorporated lithologies and possibly redox conditions during subduction.

In this study, we present new Mo isotope data for South-Mid Atlantic Ridge basalts that partly interacted with the enriched Discovery and Shona mantle plumes. Isotopically heavier Mo isotope ratios (δ^98/95Mo > ambient depleted mantle) are observed in samples tapping a more enriched mantle source. Furthermore, δ^98/95Mo correlates with radiogenic isotopes (Sr, Nd, Hf) indicating recycling of a Proterozoic sedimentary components with a Mo isotopic composition that was not modified during and before subduction by Mo mobility under oxidising conditions. Rather, the new Mo isotope data supports and expands on previous stable Se and S isotope evidence that suggests the incorporation of subducted anoxic Proterozoic deep-sea sediments into the mantle of the South-Mid Atlantic Ridge basalts.

How to cite: Ahmad, Q., Wille, M., Rosca, C., Labidi, J., Schmid, T., Mezger, K., and König, S.: Modern hotspot-influenced MORBs reveal anoxic conditions during deposition and subduction of recycled Proterozoic sediments in their source, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11903, https://doi.org/10.5194/egusphere-egu22-11903, 2022.

The absence of a forearc is a recurrent simplification in numerical subduction models. This because, to our knowledge, there are no previous studies that have systematically investigate the role of this structure on subduction systems. Despite its short length (166 ± 60 km), the forearc has a significant impact in the maintenance of a stable subduction. It has already been proposed that the serpentinization of this region, by percolating fluids from the sinking slab, reduces the effective mechanical strength of the plate coupling zone interface, allowing the one-sided asymmetric subduction observable in nature. Moreover, the forearc could be the key stabilization mechanism in intra-oceanic subduction settings. In this scenarios, the oceanic overriding plate (OP) could be in a thermal state such that would also be negative buoyant. The ubiquitous presence of forearcs in all-active intra-oceanic subductions suggests that a weak interface alone could not be enough to prevent the OP to sink. Adding a positive buoyant forearc  to the tip of the OP could provide the counterforce required to prevent the OP to sink, and eventually, double-sided subduction setting. There are studies that already implement a forearc structure in their numerical models. However, since its dynamic influence has not been study yet, we can not predict its impact and/or ascribe a specific dynamic behaviour of the system to it. 

In this work we investigate the role of the forearc and its contribution to emergent features in subduction zones. We present a series of fully dynamic, buoyancy driven, thermo-mechanical numerical modelling experiments with a free surface carried out to gain insight on the dynamic role of the forearc.  We use the Underwolrd numerical code to perform a parametrization to geometric and rheologic parameters of this structure, namely the thickness (age of the OP), length and density. We consider a forearc that encompasses the arc (25 to 250 km wide) as well. We kept all physical properties of the subducting plate  constant throughout all models. Therefore, we are able to ascribe all dynamic changes solely to variations of the forearc properties. We test different forearc compositions based on its density, ranging between 2700 and 3300  kg.m⁻³, for 200  kg.m⁻³ intervals, mimicking a full granitic continental and an basaltic oceanic forearc, respectively. For all densities, we also test several possible lengths, for 130 km and for 200 to 470 km, for intervals of 90 km. Additionally, we test all possible density-length combinations for five different OPs, in terms of age, ranging between 20 and 100 Myr, for 20 Myr intervals. 

We expect a higher accommodation of strain in the tip of the OP in models where the forearc is implemented. The presence of this structure could favor slab roll-forward before this reaches the 660 km discontinuity, enhance subduction velocities and generate a more pronounced orogenic topography. This features would be enhanced with the decrease of density and thickness and  the increase of length of the forearc.

How to cite: Bolrão, F., Almeida, J., C. Duarte, J., and M. Rosas, F.: Numerical modeling of subduction zones: thermo-mechanical stabilization as a function of overriding plate rheology and thickness, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12659, https://doi.org/10.5194/egusphere-egu22-12659, 2022.

The ‘channel flow’ concept is generally associated with the collisional mountain belts (such as the Himalaya) to explain the exhumation of deeper crustal materials. According to the concept, the top part of the subducting plate gets ‘molten’ and tries to return to the surface following the ‘pipe flow’ mechanism via a combination of Poiseuille- and Couette Flows. In this study, we employed these concepts to address a long-standing debate related to the existence and cryptic nature (normal/ reverse) of an orogen parallel discontinuity, named the Jhala Normal Fault (JNF) present in the Bhagirathi River section of the Garhwal Higher Himalaya. More importantly, while a group of researchers consider the JNF to be the northern boundary of the Higher Himalayan channel (i.e., the South Tibetan Detachment System), another group put the JNF well inside the channel. In this scenario, understanding the mechanism of deformation at the JNF will not only solve this local issue but will also provide us with new insights into the geodynamic evolution of an orogeny. Based on fresh field observations and SHRIMP geochronological data (zircon and monazite), a model is being proposed in the current study to explain the origin and evolution of the JNF. The presence of amphibolite-grade rocks across the JNF, along with the lack of well-developed extensional markers, confirm that the fault is located within the Higher Himalayan channel, and not at the channel boundary. The U-Pb zircon rim ages of 33.8 ± 0.8 Ma and 30.7 ± 0.5 Ma obtained from the JNF hanging wall (northern block) and footwall (southern block), respectively, are considered as the ages of peak metamorphism. The hanging wall, which was present at the slow-moving marginal part of the channel during Eocene, eventually lagged behind the relatively faster and warmer central part. As a result, the footwall (southern) block experienced a faster exhumation, resulting in normal-sense movement along the JNF, as documented by sparse extension markers. At 21.4 ± 2.3 Ma (monazite U-Pb age), tourmaline-bearing leucogranite intruded in the JNF hanging wall, rupturing the host. This indicates the passive uplift of the JNF hanging wall (in a brittle domain) as a part of the Higher Himalaya. Hence the JNF originated as an intra-channel discontinuity, and our proposed model predicts the origin of a ‘normal fault’ during crustal channel flow.

How to cite: Bose, N., Imayama, T., Kawabata, R., Gupta, S., and Yi, K.: Channel-flow induced ‘normal faulting’ in the Himalaya: a case study from the Jhala Normal Fault, Garhwal Higher Himalaya, NW India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13213, https://doi.org/10.5194/egusphere-egu22-13213, 2022.

The NE striking Longmen Shan (LMS) mountains are located at the eastern margin of the Tibetan plateau, and towers nearly 5000m above the Sichuan basin, which is considered to be the greatest relief than anywhere else around the plateau. From west to east, three major sub-parallel faults straddle the Longmen Shan: Wenchuan-Maoxian fault (WMF), Yingxiu-Beichuan fault and Guanxian-Anxian fault. Several models have been proposed to explain the Cenozoic uplift of the Longmen Shan. The major two models are lower crustal channel flow and upper crustal shortening, which imply different movement sense on the Wenchuan-Maoxian fault. The former suggests that the LMS were uplifted above a lower crustal flow expulsed from below the Tibetan plateau and would require a normal sense movement on the MWF. The latter implies that a series of upper crustal thrusts controlled the uplift of the LMS, and the WMF should have a reverse sense. Here we present field observations, fault gouge structural analysis and authigenic illite K-Ar geochronology data of fault gouge in the Wenchuan-Maoxian fault, showing that the Maoxian-Wenchuan fault was dextral with a reverse component at ~7Ma. Reconstruction of offsets of river valleys along the Wenchuan-Maoxian fault suggests that the corresponding total horizontal dextral offset is ~25km. Analysis of the thermochronology data acquired on both side of the fault suggest that dextral-reverse faulting started at ~13 Ma and possibly lasted until today. Our conclusions support the upper crustal shortening model and suggest the channel model maybe not applicable to Longmen Shan uplifting in the Miocene.

How to cite: Ge, C., Leloup, P. H., Zheng, Y., and Li, H.: No channel flow in the Longmen Shan: evidence from the Maoxian-Wenchuan fault Cenozoic kinematics (SE Tibet), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13458, https://doi.org/10.5194/egusphere-egu22-13458, 2022.

First ⁴⁰Ar/³⁹Ar isotopic age data for gold hydrothermal veinlet-vein mineralization of the late Mesozoic Ketkap-Yuna igneous province (KYuIP) of the Aldan shield (AS) confirm the geological relation of this type of mineralization with the early Cretaceous sub-alkali magmatism. The combination of geological characteristics and U-Pb dating of magmatites indirectly enabled us to determine the age and highly productive bi-metasomatic «massif-skarn» type of mineralization associated with sub-alkali magmatogenic formations of the province.

Isotopic datings of magmatites and gold mineralization of the KYuIP and other late Mesozoic igneous provinces of the Aldan shield show age conformity of ore-bearing magmatites and ores accompanying them (fig. 1, 2). A relative, in comparison to provinces of the tectonic-magmatic activation (TMA) of the Western and Central Aldan, delay in time of occurrences of the KYuIP late Mesozoic magmatism and gold mineralization related to it, and the difference in volume ratios of formational types of magmatic formations in different provinces can be explained by the characteristics of tectonic structure of the region.

We have distinguished two large areas of the late Mesozoic TMA of the AS differing in the timing of polyformational magmatism and concomitant mineralization of different types, and in dominating formational type of magmatites: Western–Central-Aldan on the one hand, and Eastern-Aldan on the other (fig. 1-3). The first is characterized by a long-term development of magmatic activity from the Berriasian to the early Albian (≈ 30 Ma), and prevalence of leucitite–alkali(foid)-syenite formation; the second is characterized by occurrences of magmatism in a period twice as smaller (≈ 15 Ma), and domination of subalkaline diorite-granodiorite-granite formation.

The termination of the late Mesozoic magmatism in both areas was sub synchronous. The “set” of magmatogenic formations within them is also similar: leucitite–alkali(foid)-syenite with alkali granites, monzonite(subalkaline shonkinite)-syenite and subalkaline diorite-granodiorite-granite. A typical feature of the Eastern-Aldan area of the TMA consists in Coniacian-Santonian burst of alkali volcanoplutonism, which manifested in the KYuIP after a long (about 30 Ma) period of amagmatism.

How to cite: Polin, V., Zvereva, N., Travin, A., and Ponomarchuk, A.: Ketkap-Yuna igneous province gold mineralization age, ore-bearing complexes formational types, and different occurrence time of the late Mesozoic magmatism in different parts of the Aldan shield, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-163, https://doi.org/10.5194/egusphere-egu22-163, 2022.

The results of studying the granulite belts of the Earth show the presence of two types of granulite metamorphism in them: high-pressure and high-temperature ones.

     High-pressure granulites are characterized by P-T trends in the form of clockwise curves. According to widespread opinion,  the granulite metamorphism with such trends characterizes the areas that were formed as a result of the tectonic thickening of the crust due to continent-continent collisions that correspond to the model of the Himalayan type.

     High-temperature granulites are characterized by counterclockwise trends. For the formation of such granulites, researchers involve the mechanism of mantle underplating or the introduction of large volumes of intrusions under stretching. This model requires a mantle plume, which transports hot mantle material to the base of the crust.

  Thus, granulites with contrasting P-T trends, "orogenic" and "anorogenic" may be present inside the same belt. High-temperature granulites are superimposed on the dominant high-pressure ones. The time interval between these discrete events is not clearly defined and can be estimated in several tens of millions of years.

      Let's consider these two types of metamorphism against the background of the events of the supercontinental cycle (SC). Its structure consists of two stages: proper-continental (one continent-one ocean) and intercontinental (several continents-several oceans). In turn, the stages divide into phases. The first agglomeration phase of the proper-continental stage is characterized by compaction of already collected continental fragments. After the supercontinental culmination, the next, destruction phase begins, which precedes and prepares the break-up of the supercontinent. Its main content is continental rifting and the formation of the basic intrusions. The content of the first phase of the second stage consists of the break-up of the supercontinent, the formation of spreading zones and passive margins of young oceans. The next convergent phase of this stage is the assembly of the new supercontinent, the formation of subduction zones and the closure of young oceans as a result of numerous collisions.

     Based on the collision model of high-pressure granulite metamorphism, it is obvious that its formation will occur in this convergent phase of the SC, when, as a result of continent-continent collisions, a new supercontinent is assembled.

     Conditions for high-temperature granulite metamorphism in a tension environment arise in the phases of destruction and break-up of this supercontinent when plume processes are actively manifested as a result of the heat blanket effect.

      The analysis of the modern world factual material on supercontinental cyclicity for 3 billion years of the Earth history, conducted by the author, generally confirms the above correlation of the evolution of metamorphism during the development of granulite belts with events of SC.

Thus, these two types of granulite metamorphism, which fit into the structure of the super continental cycle, are indicators of geodynamic conditions of the corresponding stages and phases of the SC and show a complex interaction in the course of their manifestation of two geodynamic styles - the tectonics of lithospheric plates and mantle plumes.

How to cite: Bozhko, N.: On the manifestation of two types of granulite metamorphism during supercontinental cyclicity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-362, https://doi.org/10.5194/egusphere-egu22-362, 2022.

We have carefully studied an unusual sulfide-bearing garnet megacryst from the ever-surprising Cenozoic Shavaryn-Tsaram basaltic cone (Tariat Platou, Mongolia). Similar sulfide inclusions in minerals constituting mantle xenoliths and clinopyroxene megacrysts related to alkali basalts were already known (Peterson and Francis, 1977, Chaussidon et al, 1989, Ionov et al, 1992) but they have never been found in garnet megacrysts. Since these garnets are believed to be mantle-derived material, their sulfide inclusions provide information on the deep sulfur cycle.

The sulfide-rich garnet megacryst from Shavaryn Tsaram pyroclastic strata is a chip of a large (up to 3 cm) cracked and partly quenched glassy crystal (fig. 1A, fig.1B) with melt pockets (Aseeva et al, 2021) inside (fig. 1C).

Sulfide inclusions are primary, isometric, elongated, and orientated towards crystal growth with a distinctive arrangement (3D X-ray images, Skyscane, fig. 2A). Swarms of inclusions contour the growth planes typical for the deltoidal icositetrahedron (fig. 2B).

Sulfide inclusions mainly consist of Ni-bearing pyrrhotite (1.66-2), scarce chalcopyrite (fig.3A and B), and rarely of pentlandite. Incompletely crystallized droplets of MSS (monosulfide solid solution) occur periodically as thin crystal pyrrhotite and pentlandite intergrowths (fig. 3C). These MSS inclusions are thought to be a product of the sulfide melt exsolution caused by undercooling (Chaudison et all, 1989).

The multi-isotope sulfur composition of these sulfide inclusions has been studied to define whether the sulfur source is crustal or mantle-derived. Thus, their δ³⁴S values account for 0.2-0.4‰, δ³³S for 0.1-0.2‰, and Δ³³S for 0.00-0.03‰, which is characteristic of mantle, meteoric, MORB, and volcanic settings. As for the host garnet, its oxygen isotope composition (Δ¹⁸О 5.4 to 5.8‰) also suggests the volcanic origin of these sulfides.

Submicron surface analysis (Bruker Dimension Icon and Solver NT-MDT) reveals the linear-globular structure of garnet (fig. 4A). Being probable nuclei, nearly 1 μm globules compose layers of garnet. We assume that garnet crystal formed via epitaxial growth from the gas phase. Garnet megacryst linear structures consisting of globules differ significantly from the metamorphic garnet crystal lattice (fig. 4B). Sulfur redundancy causes sulfide droplets, immiscible with silicate material (fig. 4C), to gather and form bulbs on top of a growing crystal due to surface tension (fig. 4C). 

The following conclusions may be drawn: 1. Sulfide inclusions in alkali basalt-associated garnet megacrysts are primary. 2. Sulfides hosted in garnet are mantle-derived according to isotopic data. 3. Garnet megacryst formation was caused by epitaxial growth.

How to cite: Aseeva, A., Ignatyev, A., Karabtsov, A., Ruslan, A., Sinev, A., Velivetskaya, T., Vysotskiy, S., and Ushkova, M.: Sulfide inclusions in alkali basalt-associated garnet megacrysts shed light on the mysterious megacryst nature, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-379, https://doi.org/10.5194/egusphere-egu22-379, 2022.

Eastern Anatolia (Eastern Turkey) resides in the Alpine-Himalayan orogenic belt and hosts the Eastern Anatolian Volcanic Province (EAVP), one of the volumetrically most important volcanic provinces within the circum-Mediterranean region. Previous studies have revealed that the predominant portion of EAVP is composed of the products of the sub-continental lithospheric mantle (SCLM) metasomatized during subduction of the Neo-Tethyan slab. The wide distribution of the lithospheric signatures in EAVP lavas has led to the availability of a large number of geochemical information regarding the regional SCLM in eastern Anatolia. In contrast, the nature of the asthenospheric mantle of eastern Anatolia remains poorly constrained due to scarcity of the asthenosphere-derived melts and lack of detailed information on the source components it comprises. Hence, this study aims primarily to put constraints on the chemical nature of asthenosphere beneath eastern Anatolia by a detailed characterization of its end-members.  

In this study, we provide new trace element and Sr-Nd-Hf-Pb isotope data from Quaternary Elazığ volcanism. This volcanism, entirely represented by mafic alkaline basaltic rocks, is one of the most recent members of EAVP, and its chemistry provides compelling evidence for a predominate asthenosphere origin. Modellings suggest that these mafic volcanics are largely free of crustal assimilation; their geochemical signatures, hence, closely reflect their source regions. Their trace element and Sr-Nd-Hf-Pb isotope systematics are consistent with derivation from an asthenospheric mantle source domain containing approximately 70% recycled oceanic lithologies with the characteristics of the C-like mantle component. However, minor contributions from depleted component (DM; ca. 20%) and an enriched component representing metasomatically modified SCLM (ca. 10%) are also needed to explain their total range of isotope data. With these findings, we propose that the C-like material is dispersed within the asthenosphere, and has mixed with the depleted mantle matrix beneath eastern Anatolia. The SCLM domains, on the other hand, occur as detached pods, following the lithospheric delamination in the region. Having triggered by the extensional dynamics during Quaternary, upwelling of the hot asthenosphere resulted in the melting of the C-DM and SCLM domains. Subsequently, the C-DM melts interacted with the SCLM-type melts, eventually generating the Elazığ volcanism.

How to cite: Aktağ, A., Sayit, K., Peters, B. J., Furman, T., and Rickli, J.: A relatively pristine C-like component in the eastern Anatolian asthenosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-516, https://doi.org/10.5194/egusphere-egu22-516, 2022.

Most researchers believe that large igneous provinces (LIPs) are formed by adiabatic melting of heads of ascending mantle plumes. Because the LIPs have existed throughout the geological history of the Earth (Ernst, 2014), their rocks can be used to probe the plume composition and to decipher the evolution of deep-seated processes in the Earth’s interior.

The early stages of the LIPs evolution are discussed by the example of the eastern Fennoscandian Shield, where three major LIP types successively changed each other during the early Precambrian: (1) Archean LIP composed mainly of komatiite-basaltic series, (2) Early Paleoproterozoic LIP made up mainly of siliceous high-Mg series, and (3) Mid-Paleoproterozoic LIP composed of picrites and basalts similar to the Phanerozoic LIPs (Sharkov, Bogina, 2009). The two former types of LIPs derived from high-Mg depleted ultramafic material practically were extinct after the Mid-Paleoproterozoic, whereas the third type is survived till now without essential change. The magmas of this LIP sharply differed in composition. Like in Phanerozoic LIPs, they were close to E-MORB and OIB and characterized by the elevated and high contents of Fe, Ti, P, alkalis, LREE, and other incompatible elements (Zr, Ba, Nb, Ta, etc.), which are typical of geochemically enriched plume sources.

According to modern paradigm (Maruyama, 1994; Dobretsov, 2010; French, Romanowiсz, 2015, etc.), formation of such LIPs is related to the ascending thermochemical mantle plumes, generated at the mantle-liquid core boundary due to the percolation of the core’s fluids into overlying mantle. Thus, these plumes contain two types of material, which provide two-stage melting of the plume’s heads: adiabatic and fluid-assisted incongruent melting of peridotites of upper cooled margins (Sharkov et al., 2017).

These data indicate that the modern setting in the Earth’s interior has existed since the Mid Paleoproterozoic (~2.3 Ga) and was sharply different at the early stages of the Earth’s evolution. What was happened in the Mid Paleoproterozoic? Why thermochemical plumes appeared only at the middle stages of the Earth’s evolution? It is not clear yet. We suggest that this could be caused by the involvement of primordial core material in the terrestrial tectonomagmatic processes.  This core survived from the Earth’s heterogeneous accretion owing to its gradual centripetal warming accompanied by cooling of outer shells (Sharkov, Bogatikov, 2010).

References

Dobretsov, N.L. (2008). Geological implications of the thermochemical plume model. Russian Geology and Geophysics, 49 (7), 441-454.

Ernst, R.E. (2014). Large Igneous Provinces. Cambridge Univ. Press, Cambridge, 653 p.

French, S.W., Romanowicz, B. (2015). Broad plumes rooted at the base of the Earth’s mantle beneath major hotspots. Nature, 525, 95-99.

Maruyama, S. (1994). Plume tectonics. Journal of Geological Society of Japan, 100, 24-49.

Sharkov, E.V., Bogina, M.M. (2009). Mafic-ultramafic magmatism of the Early Precambrian (from the Archean to Paleoproterozoic). Stratigraphy and Geological Correlation, 17, 117-136.

Sharkov, E.V., Bogatikov, O.A. (2010). Tectonomagmatic evolution of the Earth and Moon // Geotectonics 44(2), 83-101.

Sharkov, E., Bogina, M., Chistyakov, A. (2017). Magmatic systems of large continental igneous provinces. Geoscience Frontiers 8(4), 621-640

How to cite: Sharkov, E.: The Late Cenozoic global activation of tectonomagmatic processes as a result of physico-chemical processes in the solidifying Earth’s core?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-968, https://doi.org/10.5194/egusphere-egu22-968, 2022.

More than 200 metasomatised peridotite xenoliths containing phlogopite, amphibole and ilmenite from the Komsomolskaya pipe are garnet and spinel harzburgites or dunites, and clinopyroxene-enriched lherzolites with garnets (up to 12.5 wt.% Cr₂O₃) and clinopyroxenes (up to 5 wt.% Na₂O). Low-Cr varieties are Fe-enriched pyroxenites, phlogopite metasomatic veins and type A, B eclogites. Minerals were studied by electron microprobe and LA-ICP-MS which revealed their geochemical groupings and their distribution in the mantle section.

     Results indicate that the lithospheric mantle beneath the Komsomolskaya pipe is layered and relatively heated. Heated peridotites at the lithosphere base (7-6 GPa) are enriched in Fe and are porphyroclastic, deformed types and rare polymict breccias. The cold group at 6.0-5.5 GPa (34 mW/m²) are depleted peridotites with sub-Ca garnets. Cpx-fertilized varieties belong to the middle part of the mantle section. Amphiboles range from Cr-hornblendes to edenites (2-6 GPa), showing K-Ti enrichment. Picroilmenites yield two pressure intervals from 6.5 to 5.0 GPa and from 5.0 to 4.0 GPa, forming two differentiation branches. Eclogites are mainly related to the lower part of the section with a peak at pressures of 4-6 GPa.

Trace elements of melts that formed harburgitic garnets-pyroxenes rever to oceanic MORB like melt interaction with peridotites. The subcalcic S-type garnets are similar to subduction-related melts (S-type REE) with troughs in HFSE. Adakite-like hybrid metasomatism formed Na, Al-rich pyroxenes with peaks in Sr and HFSE. K-bearing pyroxenes and amphiboles refer to shoshonitic metasomatism.

Trace elements for Cpx of re-fertilized mantle peridotites have high LREE, Nb-Ta troughs and peaks in Zr, Th, Sr, U and are related to carbonatite –alkaline melts. Protokimberlite (essentially carbonatitic) interaction produced HFSE-enrichment. Type B eclogites show more subduction-related features with HFSE troughs while type A eclogites are closer to hybrid and peridotitic signatures. We suggest six types of major metasomatic agents.  The ⁴⁰Ar/³⁹Ar ages of phlogopites are in the 440-690 Ma range, with some at 1.6 Ga, suggesting multistage metasomatism.  Supported by  RFBR grant 19-05-00788

How to cite: Ashchepkov, I., Ntaflos, T., Medvedev, N., Yudin, D., Makovchuk, I., and Salikhov, R.: The multistage metasomatized mantle beneath Alakit: evidence from mantle xenoliths from Komsomolskaya kimberlite pipe, Yakutia, stages of mantle evolution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1176, https://doi.org/10.5194/egusphere-egu22-1176, 2022.

A study of chrome-spinels and PGE mineralization (PGM) from the podiform chromitites has been carried out on the area of four locations of the Ospa-Kitoy ophiolite massif (northern and southern branches East Sayan ophiolite). It has been established that different PGM assemblages formed at different stages of formation of the Ospa-Kitoy ophiolite massif, at various temperature and fluid regimes, are present at four sites. The chromite pods show both disseminated and massive structures. There are veins of massive chromitites, 0.01-0.5 m thick and 1-10 m long, rarely disseminated, schlieren, and rhythmically banded ores, which are discordant to the host ultramafic rocks. (Os-Ir-Ru) alloys occur as inclusions in the Cr-spinel or intergrowth with them (fig 3a). In addition, FePt3 alloys are found in the PGM assemblage. In such grains, decomposition structures of solid solutions represented by osmium lamellas can be observed. Polyphase PGM assemblage: (Os, Ir, Ru), (Ni, Fe, Ir),  (Ir, Ru, Pt)AsS, CuIr2S4, (Os, Ru)As2, Rh-Sb,  PtCu, and Pd5Sb2 are localized in serpentine, in close association with sulfides, sulfoarsenides, arsenides of nickel.

Figure 1. Chromitite bodies and PGE mineralization in Ospa-Kitoy ophiolite massif: 1 – Harh mountain (north branch of the ophiolites); 2 –  lake Sekretnoye (apically Zun-Ospa river); 3 – stream Zmeevikovyi (south branch of the ophiolites); 4 – Harh-Ilchir site (south flank Harh mountain).

Figure 2. Composition of  Os-Ir-Ru alloys: 1 – Harh mountain, 2 – lake Sekretnoye site, 3 – stream Zmeevikovyi.

Based on chemical and microtextural features of the PGM´s and assemblage with magmatic and hydrothermal minerals in the chromitites, it is established that each studied location of chromitites at different stages of PGM formation are exhibited. High-temperature magmatic Os-Ir-Ru alloys are widely exhibited in the Harh and Zmeevikovyichromitites. In the Harh-Ilchir site, there is no magmatic PGM and are established sulfoarsenides and arsenides Ru, Ir, which are formed from the residual fluid phase in the late magmatic stage. Chromitites in the lake Sekretnoye MPG are contained high-temperature magmatic (Os-Ir-Ru) alloys, and there are signs of PGE remobilization with Os⁰ , Ru⁰ , (Ir-Ru) alloys. Remobilization processes during serpentinization and fluid interaction of peridotites and chromitites.

In addition, it should note that the PGM assemblage of the Zmeevikovyi and Harh-Ilchir locations has been undergone by influence metamorphogenic fluids with increased activity of O₂, As, Sb. and these minerals can be formed directly in hypergenic environments. PGM҆'s such as (Ru, Rh, Pt)Sb, Rh-Sb were created at this stage.

Figure 3. BSE images of primary and secondary PGM: Harh location: а) individual grain of magmatic (Os-Ir-Ru) with microinclusion native Os; b) remobilized polyphase aggregate native Os, (Ir-Ru) (CuIr₂S₄); location Sekretnoye lake: с) inclusion magmatic (Os-Ir-Ru) in the chromite grain; d) remobilized polyphased aggregate (Ir-Ru), (Rh-Sb); location stream Zmeevikovyi: e) idiomorphic magmatic grain (Os-Ir) replaced by (Ir,Ru)AsS, with separation remobilized (Os,Ir);  Harh-Ilchir site: f) inclusion of Pd₅Sb₂ in the heazlewoodite (Hzl).

Analytics  made in Analytical Centre SB RAS. Supported by RFBR  19-05-00764а and  Russian Ministry of Education and Science.

How to cite: Kiseleva, O., Ayriants, E., Belyanin, D., and Zhmodik, S.: Manifestation of various stages PGE mineralization in the different locations Ospa-Kitoy ophiolite massif (East Sayan, Russia)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1260, https://doi.org/10.5194/egusphere-egu22-1260, 2022.

We designed the mantle transects using the PTXFO2 diagrams  (Ashchepkov et al., 2010; 2013; 2017) constructed (Fig. 1) for mantle columns beneath kimberlites of  Kaapvaal and the Congo-Kasai cratons.

The PTXFO2 diagrams (Ashchepkov et al., 2013) in South Africa were constructed using mainly analyses of garnets, eclogitic minerals and inclusions in diamonds in open publications. The sub-calcic type garnets mainly refer to the ancient low-temperature geotherms (35 mv/m2) and higher-temperature inclusions of eclogite-pyroxenite type, giving convective geotherms crossing conductive ones, which reflects the migration process of apparently hybrid melts. 

Roberts Victor is a Mesozoic pipe 95Ma  famous due to the abundance of various eclogite xenoliths. Many eclogites in the SCLM show P-Fe# trends that are typical of ascending and differentiating magmas. Such “basaltic eclogites” may show typical features of their magmatic origin (Fig.1A). They may create channels within the peridotitic lithosphere starting from the deep subduction stages.  These irregularities formed during subduction stages and due to later plumes could explain the irregular distribution of eclogites in kimberlite pipes and abundance in  Roberts Victor (Jacob et al., 2005; Huang et al., 2014) and practical absence in others.

 In the mantle of Luaxe and Cuilo pipes (Fig.1 B, C) the minerals give highly variable conditions representing the multistage metasomatic processes. The oxygen conditions are good for diamonds  The mantle column reveals a long ilmenite trend and the presence of abundant eclogites (Zinchenko et al., 2021; Nikitina et al., 2014; Ashchepkov et al., 2012).

In the sub-meridional mantle transect through the South Kaapvaal and Zimbabwe cratons, mainly dunitic at the basement ancient cores of cratons like in Lesotho and Central part of  Zimbabwe mantle is relatively depleted and low temperature.   In the marginal parts like near Premier pipe, Venetia in Limpopo and Orapa in Magondi belt the amount of the pyroxenitic and eclogitic materials drastically rises and the temperature regimes and oxidation state rise because these zones are more transparent for the melts. These zones are often highly diamondiferous and the largest diamonds are occurring in these regions and pipes (Fig. 2).

In the mantle section through the pipes of the so-called diamond-bearing corridor of the Lucapa within the northeastern part of the Congo craton (Fig. 3), the immersion of the least oxidized and more productive horizon represented mainly by depleted peridotite material and much less oxidized is gradually thinking and in the to the southwest is recorded in the lower part. The temperatures in the lower part are also decreasing. This determines the sharp increase in the diamond grades of kimberlite pipes in this direction. But commonly this transect represents a relatively smooth homogeneous structure, the lithosphere of the craton's mantle distinguishes outflow clusters corresponding to thickenings of pips and kimberlite clusters that have arisen within the limits of separately permeable zones that occur at the intersection of deep faults.

RFBR grant 19-05-00788.  Supported by Ministry of Science and Higher Education.

How to cite: Ashchepkov, I., Zinchenko, V., Ivanov, A., and Logvinova, A.: Mantle transects in South and Central Africa according to data of mantle xenocrysts and diamond inclusions.  , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1306, https://doi.org/10.5194/egusphere-egu22-1306, 2022.

The system CaCO₃-MgCO₃ has been used since the '60s for reconstructing the petrogenesis of carbonated lithologies, notably of carbonatite magmas possibly generated in the Earth's mantle. Yet, experimental results at high temperatures and pressures remain contradictory, and a thermodynamic model for the carbonate liquid in this binary is still lacking.

We experimentally investigated the melting of aragonite and magnesite to pressures of 12 GPa, and of calcite-magnesite mixtures at 3 and 4.5 GPa, and at variable Mg/(Mg+Ca) (X_Mg). Results show that the melting of aragonite, and of magnesite have similar slopes, magnesite melting ≈ 30 °C higher than aragonite. The minimum on the liquidus surface is at X_Mg ≈ 0.35-0.40, 1200 °C at 3 GPa, and 1275 °C at 4.5 GPa, which, when combined with data from Byrnes and Wyllie (1981) and Müller et al. (2017), imply that minimum liquid composition remains approximately constant with pressure increase. We present the first thermodynamic model for CaCO₃-MgCO₃ liquids, retrieved from the experimental data available. Although carbonate liquids should be relatively simple molten salts, they display large non-ideality and a three-component (including a dolomite component), pressure dependent, asymmetric solution model is required to model the liquidus surface. Attempts to use an end-member two-component model fail, invariably generating a very wide magnesite-liquid loop, contrary to the experimental evidence.

The liquid model is used to evaluate results of experimentally determined phase relationships for carbonated peridotites modelled in CaO-MgO-SiO₂-CO₂ (CMS-CO₂), and CaO-MgO-Al₂O₃-SiO₂-CO₂ (CMAS- CO₂). Computations highlight that the liquid composition in the CMS-CO₂ and CMAS-CO₂ and in more complex systems do not represent "minimum melts" but are significantly more magnesian at high pressure, and that the pressure-temperature position of the solidus, as well as its dP/dT slope, depend on the bulk composition selected, unless truly invariant assemblages occur. Calculated phase relationships are somewhat dependent on the model selected for clinopyroxene, and to a lesser extent of garnet.

Byrnes A.P. and Wyllie P.J. (1981) Subsolidus and melting relations for the join CaCO₃-MgCO₃ at 10 kbar. Geochim. Cosmochim. Acta 45, 321-328

Müller I.A., Müller M. K., Rhede D., Wilke F.D.H. and Wirth R. (2017) Melting relations in the system CaCO₃-MgCO₃ at 6 GPa. Am. Mineral. 102, 2440-2449.

How to cite: Poli, S., Zhao, S., and Schmidt, M. W.: An experimental determination of the liquidus in the system CaCO3-MgCO3 and a thermodynamic analysis of the melting of carbonated mantle melting, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1531, https://doi.org/10.5194/egusphere-egu22-1531, 2022.

Mantle xenoliths provide a clear evidence of interaction with low-degree mantle melts, however, this evidence is mostly geochemical, manifested by incompatible element enrichment, or mineralogical, manifested by already crystallised phases (e.g. amphibole, phlogopite) as a result of this interaction.

Despite decades of research, the composition of low-degree melts generated in lithospheric mantle are still not very well-known. In situ characterisation of such melts is hampered due to their modification during the ascent as well as rapid alteration and weathering at the surface, while experiments are hampered by difficulties to produce and analyse very low-degrees (<2-3%) melts.

In this study we report a rare sample of well-preserved low-degree melts within a peridotite xenolith GGU473178 from Majuagaa kimberlite in West Greenland. We report alkali-carbonatitic-chloride melt pools and veins that may represent primary low-degree partial melts and products of their in situ crystallisation.

Melt pools are largely composed of carbonate (predominantly dolomite) and contain spinel, apatite, phlogopite as well as minor amounts of Fe-Ni sulphides, barite and halite.

Euhedral crystals of spinel present in these melt pools contain large usually round aggregates of mineral inclusions, which we explain as former melt pools captures by spinel. Mineral assemblage found in these spinel inclusions is consistently composed of ferropericlase, dolomite, alkali-rich carbonate and apatite, which is indicative of a strongly silicate-undersaturated alkali-carbonatitic melt that contains chlorine and phosphorous. Due to the almost complete absence of SiO₂, ferropericlase (instead of olivine) crystallises in equilibrium with dolomite and alkali-rich carbonate, implying incredibly low degrees of melting, when essentially only carbonated component is melted, or carbonate-silicate liquid immiscibility, previously reported for spinel lherzolite and garnet wehrlite xenoliths (Frezzotti et al., 2002; Soltys et al., 2016).

References

Frezzotti, M. L., Touret, J. L. R., and Neumann, E. R., 2002, Ephemeral carbonate melts in the upper mantle: carbonate-silicate immiscibility in microveins and inclusions within spinel peridotite xenoliths, La Gomera, Canary Islands: European Journal of Mineralogy, v. 14, no. 5, p. 891-904.

Soltys, A., Giuliani, A., Phillips, D., Kamenetsky, V. S., Maas, R., Woodhead, J., and Rodemann, T., 2016, In-situ assimilation of mantle minerals by kimberlitic magmas — Direct evidence from a garnet wehrlite xenolith entrained in the Bultfontein kimberlite (Kimberley, South Africa): Lithos, v. 256-257, p. 182-196.

How to cite: Kiseeva, E. S., Kamenetsky, V. S., and Nielsen, T. F. D.: In situ low-degree melts in peridotite xenolith from Majuagaa kimberlite, West Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1932, https://doi.org/10.5194/egusphere-egu22-1932, 2022.

Plateaus and isochronous and integral ages of ³⁹Ar/⁴⁰Ar xenocrysts and phlogopite grains from kimberlite xenoliths can be used to determine the ages of mantle processes (Hopp et al., 2008) and decipher the genesis of diamond-forming processes. Dating of deep xenoliths of kimberlites of the Siberian craton reveals a significant spread (Pokhilenko et al., 2012; Ashchepkov et al., 2015) from the Archean to the time close to the age of the host kimberlites, mainly Devonian. The most ancient ages for Udachnaya Daldyn fields for phlogopites from xenoliths of spinel harzburgites of the highest level belong to the late Archean (2.6-2.0) - early Proterozoic 1.7 -1.5 Ga. In the Alakite field, all ages are younger from 1,87 – 1,05- 0,928 - 0,87 Ga and belong to the metasomatic history of the Rodinia continent mantle. Close dates are set for xenoliths from the Obnazhennaya pipe (Kalashnikova et al. 2017).

Fig.1 PT  Udachnaya pipe. Symbols: Op: ToC(Brey, Kohler, 1990)-P(GPa)(McGregor, 1974). Cpx: 2.ToC-P(GPa)(Nimis, Taylor, 2000); 3.ToC (Nimis, Taylor, 2000 with ed. author)–P(GPa)(Ashchepkov et al., 2011); 4. eclogites ; 5. inclusions in diamond; Gar: 6.ToC (O'Neill, Wood, 1979) -P(GPa) (Ashchepkov et al., 2010Gar), 7. For eclogite garnets Chromite: 8,  inclusions in diamond; 9. chromite ToC (O'Neill, Well, 1987)-P(GPa) (Ashchepkov et al., 2010Gar), 7. For eclogite garnets Chromite: 8, inclusions in diamond; 9. chromite ToC (O'Neill, Well, 1987)-P(GPa) (Ashchepkov et al ., 2010Chr); 10 the same for inclusions in diamond; 11. Film Tom (Taylor et al., 1998)- P(GPa) (Ashchepkov et al., 2010 ilm)

Our data on micas by the ³⁹Ar/⁴⁰Ar method often reveal complex configurations of spectra. The micas of the xenocrysts of the Alakite field give several peaks, ranging from the most high-temperature and ancient, which corresponded to the upper Proterozoic - Vendian and Paleozoic, and only the lowest temperature peaks with a high Ca/K ratio corresponded to the ages of kimberlite introduction. Some peaks may be associated with the thermal effects of the Vilyusky plume (Kuzmin et al., 2012). The lowest temperature peaks, which are close in age to the time of kimberlite formation, which is confirmed by the high ³⁸Ar/³⁹Ar ratios of the gas released at the low-temperature stage, can be used very approximately for dating kimberlites, however, the release of other gases at low-temperature stages significantly increases the measurement error. All of them correspond to the interval 440 -320 Ma. The pipes Mir, Internationalnaya, Ukrainianskaya - 420, Yubileynaya -342, Botuobinskaya -352 Ma). Some definitions practically coincide with Rb/Sr ages (Griffin et al., 1999, Agashev et al., 2005, Kostrovitsky et al., 2008; Zaitsev, Smelov, 2010) and probably represent mixing lines. For many xenocrysts (Feinsteinovskaya, Ukrainskaya, Yubileynaya, Krasnopresnenskaya tr.), the interval from 600 to 500 Ma is manifested, which corresponds to the stage of the Laurasia supercontinent breakdown. The presence of relatively low-temperature plateaus with ancient ages, and high-temperature young ones implies that some stages can be correlated with the mantle history of the mineral.  RFBR grant 19-05-00788.  Supported by Ministry of Science and Higher Education.

Fig.2 PT  Sytykanskaya pipe

How to cite: Iudin, D., Ashchepkov, I., and Travin, A.: Ages of micas from xenoliths and xenocrysts of kimberlites of the Siberian Craton determined by 39Ar/40Ar method, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2177, https://doi.org/10.5194/egusphere-egu22-2177, 2022.

The nickel content in pyropes interested researchers due to the possibility to create an algorithm for calculating the temperature boundaries of its joint crystallization with diamonds. Griffin proposed such a calculation algorithm, which was named the diamond-bearing corridor with his name [1]. Determination of nickel content in pyropes on microanalysts is difficult for several reasons. The first reason is the limit of detection of nickel in pyropes, which is very high for the determination of this element on electron microscopes (at least 15 ppm). And then, such an analysis is possible at a quantitative level with a probe beam current of 300nA and an analysis time of 3 minutes. The study of the correlation ratios of nickel with other elements in pyropes allowed us to determine two elements that have a significant correlation with the nickel content in pyropes - these are titanium and manganese and their content in pyropes is acceptable for quantitative determination. On the ion microanalyzer, more than two hundred analyses were performed for pyropes from the kimberlite pipes Botuobinskaya and Nyurbinskaya, the remaining determinations were made from kimberlites tr. Jubilee and tr. Victory with the use of a new technique for the determination of nickel in pyropes in the microanalyzer JXA-8230. In total, 443 definitions of nickel in pyropes were performed at the quantitative level. Such definitions made it possible to calculate the functional dependence of nickel contents on titanium and manganese contents. The STATISTICS program is used for such calculations (Fig. 1).

Fig. 1. Map of level lines (nickel manganese titanium for 443 definitions) with the calculation of functional dependence

The calculation of nickel contents in pyropes makes it possible to fully use the Griffin geothermometer to determine the number of pyrope grains from the diamond-bearing corridor area.

• Griffin W.L., Ryan C.G. Trace elements in indicator minerals: Area selection and target evaluation in diamond exploration. J. Geochem. Explor., 1995. Vol. 53., pp, 311-357

How to cite: Ivanov, A.: Precise calculations of Nickel content in pyropes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3014, https://doi.org/10.5194/egusphere-egu22-3014, 2022.

Most of earthquakes occur below 10-km depth in the Korean Peninsula. For example, the focal depth of the Mw 5.5 Gyeongju Earthquake in 2016, the largest instrumental earthquake in South Korea since scientific earthquake monitoring started in 1978, is about 14 km with hypocentral basement rocks of granitoid and temperature of 370°C (thus, brittle-plastic transition condition). A study on ancient granitoid shear zones with the similar temperature condition will aid in understanding the seismogenesis in the brittle- plastic transition regime. The Yecheon shear zone is an NE- to NNE-striking right-lateral shear zone cross-cutting Mesozoic granitoid belt in South Korea. The deformation temperature of the main shear zone was estimated to be about 350 ℃. In the southeastern margin of the shear zone, protomylonites change gradually into mylonites and then abruptly into ultramylonites toward southeast. Quartz and feldspar grains both of protomylonite and mylonite deform by dislocation creep and brittle fracturing, respectively. Greenish ultramylonite consists of quartz-, feldspar-, muscovite- and epidote-rich layers within matrix of quartz, muscovite and epidote. The protomylonite commonly displays a composite S-C foliation. The deflecting S-foliation of mylonite toward ultramylonite is sharply truncated by the boundary between mylonite and ultramylonite. Thin (several mm to several cm) greenish layers occur in protomylonite subparallel to mylonitic foliation or cross-cutting the foliation at a low angle. They also show injection structure with flow banding and cataclastic deformation along the protomylonite boundary. The greenish layer consists of fragments of protomylonite and matrix of very fine-grained quartz, feldspar, muscovite and epidote. Epidote grains of ultramylonite and greenish layers replace phengitic mica, biotite and plagioclase and show graphic texture. Together with epidote formation, chloritization of biotite and albitization of K-feldspar are prominent in the greenish layers. The growth of hydrothermal minerals including epidote and chlorite within the greenish layers and shear band along the C-foliation indicates fluid circulation in the layers. We interpret the greenish layers were generated during seismic events in fluid-rich conditions and thus seismic event may be caused by pore pressure build up. Once the greenish layers develop, deformation was localized along the layers due to much reduced grain size in interseismic periods, and the greenish layers became ultramylonite with further grain-size reduction.

How to cite: Kim, J. H. and Ree, J.-H.: Seismogenesis in granite under brittle-plastic transition condition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3284, https://doi.org/10.5194/egusphere-egu22-3284, 2022.

The deep structure of orogenic belts and cratons has become an important part to track evolution and innovation of tectonics. The extremely thick crust and overlying deposition bring obstacles to the deep structure of the orogenic belt and ancient block. Deep seismic reflection profile is globally regarded as an advanced technology to perspective the fine structure of the crust and the top of the upper mantle, especially using large-size dynamite shots. In the 1990s, international scholars used deep seismic reflection profiles to find inclined reflections penetrating from the lower crust to the upper mantle (Calvert et al., 1995; Cook et al., 1999). They believe that these reflections are related to ancient subduction events(or fossil subduction). At the beginning of this century, Chinese scholars began to carry out similar experiments in the Tibet Plateau, Sichuan Basin and Songliao basin. Using big-size dynamite shots, they also found the Moho under the extremely thick crust of the Tibet Plateau and the mantle reflection under the ancient block (Gao et al., 2013, 2016; Zhang et al., 2015). In 2016, with the support of China Geological Survey Project,we arranged a seismic reflection profile around the Scientific Deep Drilling SK-2 Well in the middle of Songliao basin. According to the data processing results of all five big-size dynamite shots and four medium-size dynamite shots of the profile, we obtained a 127.3km long single-fold reflection profile, revealing the reflection characteristics of the lower crust, Moho and its upper mantle in the study area. The Moho structure distributed nearly horizontally at a depth of 33km (estimated by the average crustal velocity of 6km/s) is clearly obtained, and the mantle reflection extending obliquely from Moho to 80km-depth is found. We believe that this dipping mantle reflection represents an ancient subduction relic under the Songnen block.

Calvert, A. J., Sawyer, E. W., Davis, W. J., & Ludden, J. N.  Archaean subduction inferred from seismic images of a mantle suture in the Superior Province. Nature,1995, 375(6533), 670–674.

Cook,F. A., van der Velden, A. J., Hall, K. W., Roberts, B. J.Frozen subduction in Canada’s Northwest Territories: lithoprobe deep lithospheric reflection profiling of the western Canadian Shield. Tectonics 1999,18, 1–24.

Gao R, Chen C, Lu Z W, et al.New constraints on crustal structure an d Moho topography in Central Tibet revealed by SinoProbe deep seismic reflection profiling. Tectonophysics, 2013, 606:160 - 170.

Gao, R., Chen, C., Wang, H. Y., Lu, Z. W., et al.Sinoprobe deep reflection profile reveals a neo-Proterozoic subduction zone be neath Sichuan basin. Earth & Planetary Science Letters, 2016,454(18):86-91

Zhang, X. Z.,Zheng, Z.,Gao, R., et al. Deep reflection seismic section evidence of subduction collision between Jiamusi block and Songnen block. Journal of Geophysics, 2015,58 (12): 4415-4424

How to cite: Li, M., Gao, R., Zhou, J., Wilde, S. A., Hou, H., Tan, X., and Zhu, Y.: Deep seismic reflection profile with big-size dynamite shots reveals Moho and mantle reflection: tracking continental evolution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3326, https://doi.org/10.5194/egusphere-egu22-3326, 2022.

The NE of the Siberian platform in Udzha and Anabar river locate the richest alluvial placers of diamonds Since the discovery of placers > 700 were found, but no industrial bodies. A study of kimberlite magmatism has established that there are kimberlites of three ages on the territory of the North-East of the Siberian platform – middle Paleozoic (single), lower Triassic (few) and Jurassic-Cretaceous (prevailing). The latter are almost non-diamond-bearing.

The nearest kimberlite fields of Kuranakh and Tomtor are poor in diamonds. Some placers in the basin of the Udzha river, the right tributary of the Anabar, contain Cr-rich (≤14 wt.% Cr2O3) sub-calcic pyrope garnet associated with diamond. Comparison of kimberlite indicator minerals (KIMs) from the basins of Udzha and Chemara (its right tributary) shows similarity and a large diversity of pyropes, mostly of lherzolitic type. Cr- diopsides found in the Devonian collector suggest a close kimberlite source.

Mainly eclogitic placer diamonds are abundant in the upper reaches of the Chimara river in the northeastern part of the region. They occur in Permian, Jurassic, and Neogene rocks and in Quaternary alluvium where they coexist with pyrope and ilmenite. The diamonds in this region have mostly eclogitic features (Shatsky et al., 2015).

Reconstructions using monomineral thermobarometry (Ashchepkov et al., 2010) for the sources of pyrope and diamond show that the areas of the Anabar and Udzha placers share the similarity in the structure of mantle roots since 7.5 GPa, with a convective branch at the base.

The P-Fe trend for the Jurassic is slightly inclined, which is typical of the Kuranakh field. For the Devonian kimberlites, non-inclined trends are typical. The subcontinental lithospheric mantle (SCLM) beneath the Udzha basin is rich in pyroxenitic garnets as typical for the Anabar region.

There are 3 intermediate collectors of pyropes and associated diamonds: Permian, Jurassic and Neogenic and alluvium.  A study of the chemistry and thermobarometry of the kimberlite indicator minerals show some variations which possibly indicate different kimberlite sources ( Fig.1).

The detailed trace element geochemistry of the KIM from Udzha and Chemyra rivers show high variations and systematic differences.

Fig.1. PTX diagrams for kimberlite indicator minerals (KIM) from three correctors in the Udzha basin.

Fig.2 TRE distributions for KIM from Udzha alluvium

Fig.3 TRE distributions for KIM from Udzha alluvium

Supported by  RBRF grant 19-05-00788.

How to cite: Vavilov, M., Afanasiev, V., Ashchepkov, I., Baranov, L., and Vera, E.: Possible sources of the alluvial diamonds Udzha basin, northern Anabar region near kimberlite Tomtor field, Yakutia., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3368, https://doi.org/10.5194/egusphere-egu22-3368, 2022.

For the first time, such an indicator as the Ti content in garnets was used as a criterion for the study of heterogeneity of the lithospheric mantle (LM) beneath the Yakutian kimberlite province (YaKP). Comparison of the compositions of garnet from pipes of most fields (18 out of 21) of YaKP was carried out. The study was based on representative collections of garnets from kimberlite concentrates, as well as literature and own data on the composition of garnets from mantle xenoliths from the Upper Muna pipes and northern fields adjacent to the Anabar shield, as well as from the Udachnaya, Dal’nyaya and Obnajennaya pipes. Three groups of YaKP fields with different Ti content (Fig. 1) and Mg# values ​​in garnets have been identified - 1) southern diamondiferous fields - high TiO₂ content (0.26-0.50 wt%) and high Mg# value (80.6-82.6%); an exception is the Mirninsky field (0.13 wt.% TiO₂); 2) the dominant number of northern fields (10 in total) is a low TiO₂ content (0.06-0.26 wt%) (Fig. 2) and a relatively high value of Mg# (78.8-81.7%, middle - 80.2%); 3) three northern fields (Chomurdakh, Ogoner-Yuryakh and Toluopka) - high TiO₂ content (0.53-0.78 wt.%) (Fig. 3) and low Mg# (76.9-78.3%). The trace element composition of garnets from the third group testifies to their mainly equilibrium magmatic crystallization (Fig. 4). It is assumed that the garnet-bearing rocks, due to the relatively low lithospheric mantle (LM) thickness in the marginal part of the Siberian Craton, were subjected to almost complete metasomatic processing by melt-fluids of the asthenospheric mantle. The obtained data on the composition of garnets allowed the authors to clarify the reason for the different compositions of kimberlites in the southern and northern fields of YaKP. The authors believe that the predominantly high-Ti composition of the kimberlites of the northern fields, despite the low-Ti composition of the LM rocks, reflects the primary composition of the kimberlite melt-fluid of asthenospheric origin. The relatively small thickness of the LM beneath the northern fields limited the degree of assimilation by kimberlite melt of high-Mg rocks of LM and initiated an increase in asthenosphere activity, which led to the formation of high-Ti kimberlites, high-Ti alkaline basalts, and alkaline-carbonatite massifs here. Supported by RBRF grant 19-05-00788

How to cite: Kostrovitsky, S., Yakovlev, D., Ashchepkov, I., and Tappe, S.: Inhomogeneity of the composition of lithospheric mantle beneath the Yakutian kimberlite province, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3753, https://doi.org/10.5194/egusphere-egu22-3753, 2022.

Xenoliths in kimberlites and other volcanic rocks are our best window into the subcranotic lithospheric mantle. Chemical overprinting associated with melt-rock interactions is almost ubiquitous in these mantle xenoliths [1]. Such local changes in chemistry may be recorded by the formation of compositional zoning in minerals. Studies of major and trace element zoning provide important information about the nature and time scales of metasomatic processes and thermal events in the upper mantle.

Usually, garnets from peridotite xenoliths have pronounced zoning, whereas olivine and pyroxenes are homogeneous. Currently, only zoning in garnets of sheared and coarse peridotite xenoliths from kimberlites of the Kaapvaal craton (southern Africa) and the minette neck The Thumb (North American craton) has been studied in detail (e.g., [2,3]). There is no detailed study on major-, minor- and trace-element zoning in garnets of peridotite xenoliths from kimberlites of the Siberian craton.

In our study, we provide a detailed description of complex major- and trace-element zoning patterns in garnets of two unique fresh sheared peridotites from the Udachnaya kimberlite pipe (Siberian craton). The mantle residence pressure and temperature of the peridotites UV-3/05 (lherzolite) and UV-33/04 (harzburgite) are 6.4 GPa and 1350°C [4] and 6.0 GPa and 1320°C [5], respectively.

The profiles of minor and major elements are complex and symmetric. The profiles change their slope signs (positive/negative) several times. It should be noted that the Ni content increases from the cores to the rims. The chondrite-normalized REE patterns show a continuous change from the cores to the rims. The cores display sinusoidal patterns (LREE enrichment peaking at Sm), whereas patterns of the rims are ‘normal’ (with HREE enriched by 15–19× chondrite abundances for Gd through Lu).

The profiles are consistent with the formation of garnet overgrowths and increasing temperature, followed by diffusive equilibration between the rims and cores over hundreds or thousands of years. Using melt-garnet distribution coefficients of trace elements, we showed that the metasomatic melt, which caused the formation of the garnet overgrowths, had a genetic link to the kimberlite magmatism that formed the Udachnaya pipe. The profile lengths of Zr, Ce, Sm, Eu, Gd, and Hf are longer than the profile lengths of Tb, Dy, Ho, Er, Tm, Yb, and Lu. This indicates that the composition of the melt changed (from composition in equilibrium with upper mantle peridotite to kimberlitic composition) during its percolation through the mantle, as predicted by the theory proposed by Navon and Stolper (1987).

This study was supported by the Russian Science Foundation (grant No 18-77-10062).

References: [1] Pearson, D.G. and Wittig, N., 2014, Treatise on Geochemistry, 255-292. [2] Griffin et al., 1989, Geochim. Cosmochim. Acta, 53(2), 561-567. [3] Smith et al., 1991, Contrib. Mineral. Petrol., 107(1), 60-79. [4] Golovin et al., 2018, Chem. Geol., 261-274. [5] Agashev et al., 2013, Lithos, 160, 201-215. [6] Navon, O. and Stolper, E., 1987, J. Geol., 95(3), 285-307.

How to cite: Solovev, K., Sharygin, I., and Golovin, A.: Zonation in garnets from the Udachnaya pipe: heating and melt infiltration in the lithospheric mantle of the Siberian craton, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3997, https://doi.org/10.5194/egusphere-egu22-3997, 2022.

Basalts from high flux intra-plate volcanism (Iceland, Hawaii, Samoa) are characterised by ³He/⁴He that are significantly higher than those from the upper mantle sampled at mid-ocean ridges.  The prevailing paradigm requires that a largely undegassed deep Earth is enriched in primordial noble gases (³He, ²⁰Ne) relative to degassed convecting upper mantle.  However, the He concentration and ³He/²⁰Ne ratio of high ³He/⁴He oceanic basalts are generally lower than mid-ocean ridge basalts (MORB). This so called ‘He paradox’ has gained infamy and is used to argue against the conventional model of Earth structure and the existence of mantle plumes.  While the paradox can be resolved by disequilibrium degassing of magmas it highlights the difficulty in reconstructing the primordial volatile inventory of the deep Earth from partially degassed oceanic basalts.

Basalts from 26 to 11°N on the Red Sea spreading axis reveals a systematic southward increase in ³He/⁴He that tops out at 15 Ra in the Gulf of Tadjoura (GoT). The GoT ³He/⁴He overlaps the highest values of sub-aerial basalts from Afar and Main Ethiopian Rift and is arguably located over modern Afar plume.  The along-rift ³He/⁴He variation is mirrored by a systematic change in incompatible trace element (ITE) ratios that appear to define two-component mixing between E-MORB and HIMU.  Despite some complexity, hyperbolic mixing relationships are apparent in ³He/⁴He-K/Th-Rb/La space.  Using established trace element concentrations in these mantle components we can calculate the concentration of He in the Afar plume mantle.  Surprisingly it appears that the upwelling plume mantle has 5-20 times less He than the convecting asthenospheric mantle despite the high ³He/⁴He (and primordial Ne isotope composition). This contradicts the prevailing orthodoxy but can simply be explained if the Afar mantle plume is itself a mixture of primordial He-rich, high ³He/⁴He (55 Ra) deep mantle with a proportionally dominant mass of He-poor low ³He/⁴He HIMU mantle. This is consistent with the narrow range of Sr-Nd-Os isotopes and ITE ratios of the highest ³He/⁴He Afar plume basalts, and is in marked contrast to high ³He/⁴He plumes (e.g. Iceland) that do not have unique geochemical composition. The HIMU signature of the Afar plume basalts implies origin in recycled altered oceanic crust (RAOC). Assuming that no He is recycled and using established RAOC U and Th concentrations, the low He concentration (< 5 x 10¹³ atoms/g He) of the He-poor mantle implies that the slab was subducted no earlier than 70 Ma and reached no more than 700 km before being incorporated into the upwelling Afar plume. We suggest that the Afar plume acquired its chemical and isotopic fingerprint during large scale mixing at the 670 km transition zone with the Tethyan slab, not at the core-mantle boundary.

This study implies that large domains of essentially He-poor mantle exist within the deep Earth, likely associated with the HIMU mantle compositions. Further, it implies that moderately high-³He/⁴He (< 30 Ra) mantle plumes (e.g. Reunion) need not contain a significant contribution of deep mantle, thus cannot be used a priori to define primitive Earth composition.

How to cite: Balci, U., Stuart, F. M., Barrat, J.-A., and van der Zwan, F. M.: Low He content of the high 3He/4He Afar mantle plume: Origin and implications of the He-poor mantle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4994, https://doi.org/10.5194/egusphere-egu22-4994, 2022.

[1] Boven et al., 1998, J. Afr. Earth Sci., 26, 463-476.

[2] Holmes and Harwood, 1932, Quarterly J. Geol. Soc., 88, 370-442.

[3] Le Maitre, 2002, Cambridge University Press.

[4] Rosenthal et al., 2009, Earth Planet. Sci. Lett., 284, 236-248.

[5] Link et al., 2008, 9^th Int. Kimb. Conf., 1-3.

[6] Foley, 1992, Lithos, 28, 435-453.

[7] Agostini et al., 2021, Sci. Rep., https://doi.org/10.1038/s41598-021-90275-7.

How to cite: Innocenzi, F., Ronca, S., Foley, S. F., Agostini, S., and Lustrino, M.: Exotic magmatism from the western branch of the East African Rift: insights on the lithospheric mantle source., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5450, https://doi.org/10.5194/egusphere-egu22-5450, 2022.

Spinel peridotite xenoliths have been found in Cenozoic basalts from the Nuomin and Keluo areas in the northern Daxinganling. The Mg content of olivine in the mantleperidotite indicates that the upper mantle in the study area is partially refractory. According to the olivine content and Fo diagram, a part of peridotite xenoliths fell in the Archean and Proterozoic mantle regions, which reveals that there are remnants of ancient lithospheric mantle in the lithospheric mantle of the study area. In the study area, harzburgite and lherzolite show high oxygen fugacity values (FMQ + 1.95-3.15), which is in sharp contrast to the low oxygen fugacity values of the relatively reduced ancient lithospheric mantle. It is possible that the Paleozoic paleo Asian Ocean and Mesozoic paleo Pacific subducted successively under the Xingmeng orogenic belt, resulting in the oxidation of the lithospheric mantle at that time. K ₂O (1% ～ 6%) is found in the reaction edge of mantle xenoliths. It is considered that the mantle in the study area has experienced multiple periods of K-rich meltactivity, and the source of K-rich melt may be related to the crust source material recycled by subduction.

How to cite: Liu, J. and Li, H.: Oxygen fugacity characteristics of lithospheric mantle peridotite in northern Xingmeng orogenic belt, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5941, https://doi.org/10.5194/egusphere-egu22-5941, 2022.

The Tuva-Mongolian microcontinent and Khamardaban terrane are known as major tectonic units accreted to the Siberian paleocontinent. We report ²⁰⁷Pb/²⁰⁶Pb ages of 2.44–2.22 Ga for sources of Late Cenozoic volcanic rocks from the Tunka volcanic zone and of 1.63–1.31 Ga for those from the Khamardaban zone. The new ages are consistent with Precambrian geological events that are characteristic of the area and contradict the existing opinion about the Early Paleozoic collisional connection between these tectonic units inferred from dating of syn-collisional granites.

On the one hand, we constrain ore-forming processes in the Gargan block of the Tuva-Mongolian microcontinent and in the south of the Siberian paleocontinent between 2.45 and 1.4 Ga and between 1.3 and 0.25 Ga, respectively [Rasskazov et al., 2010]. The latest Pb-separating event in the Gargan block was followed by the generation of restite ultrabasic Ilchir belt that bounds the block from the south [Kiseleva et al., 2020]. So, we trace the boundary between the Gargan block and Ilchir belt to magma sources of the Tunka and Khamardaban zones that reasonably denote the root part of the Khamardaban terrane, accreted to the Tuva-Mongolian microcontinent and Siberian paleocontinent 1.63–1.31 Ga ago (Figure). On the other hand, we emphasize the importance of ore-forming events in the Gargan block, launched about 2.45 Ga, simultaneously with source generation in the Tunka zone. Basalts of this zone include xenoliths of fassaitic clinopyroxenites that show wide variations in the oxidation–reduction state. We suggest that fassaite (diopside) mineralization was due to interaction between orthopyroxene and calcite: (Mg, Fe)₂Si₂O₆ + CaCO₃ → (Mg, Ca)₂Si₂O₆ + CO₂ + FeO. Orthopyroxene of high-Mg spinel harzburgite xenoliths from Khobok River lavas (Tunka basin) shows SiO₂ content as high as 58.7 wt. %, while fassaite from pyroxenite xenoliths has SiO₂ content as low as 49 wt. %. Fassaitization of orthopyroxenites and harzburgites, obviously, releases both iron and silica. These components are found as amorphous Fe–Si phases in metasomatite xenoliths with low Mg/Si and Al/Si ratios [Ailow et al., 2021]. From data obtained, we speculate that fassaitization was an effective crust-mantle process of 2.4–2.2 Ga that could provide both the deep-seated Fe–Si mineralization and the generation of ferruginous quartzites displayed in the Great Oxidation Event.

Ailow Y. et al. // Lithosphere. 2021. V. 21, No. 4. P. 517–545.

Kiseleva O.N. et al. // Minerals. 2020. V. 10. P. 1077.

Rasskazov S.V. Brandt S.B., Brandt I.S. Radiogenic isotopes in geologic processes. Springer, 2010. 306 p.

How to cite: Rasskazov, S., Chuvashova, I., Saranina, E., Yasnygina, T., and Ailow, Y.: Crustal versus mantle events of 2.44–2.22 and 1.63–1.31 Ga at the junction between Khamardaban terrane, Tuva-Mongolian microcontinent, and Siberian paleocontinent: Petrogenetic consequences, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6686, https://doi.org/10.5194/egusphere-egu22-6686, 2022.

The persistence of Archaean cratons for >2.5Ga was aided by thick, mechanically strong, and cool lithospheric mantle keels up to 250km deep. It is widely accepted that the cratonic mantle, dominated by depleted harzburgite, lherzolite and dunite, was formed by extensive melt extraction from originally fertile mantle peridotite. Models seeking to explain the formation of deep cratonic mantle in the garnet and diamond stability fields, initially sought to answer how such rocks could form in-situ at high temperatures and pressures and envisaged large-scale thermochemical plume upwellings. More recently, mineralogical and geochemical observations, namely the high Cr content of garnet and low whole rock HREE concentrations in cratonic harzburgites, have led to the conclusion that the deep cratonic mantle couldn’t have originally melted in the garnet stability field.  Mechanical stacking of shallowly depleted oceanic lithosphere was therefore proposed to have thickened the depleted lithosphere cratonic roots. In this process, the spinel facies minerals are envisaged to transform into the garnet stability field.

Here we present the first results of combined thermodynamic and geochemical modelling at temperatures high enough to reconcile the very refractory residues. We found that the requirement for initially shallow melting is no longer supported. Deep (150-250km), ultra-hot (>1800°C), incremental melting can produce the mineralogical and geochemical signatures of depleted cratonic harzburgites. The modelling also implies a link between areas of extreme depletion in the deep lithospheric mantle and the genesis of Earth’s hottest lavas (Al-enriched komatiite) by re-melting depleted harzburgite. Diamond inclusion minerals have a well-documented skew to the most refractory compositions found in cratonic peridotite. We propose that these ultra-depleted, highly reducing regions of the lithospheric root possess the highest diamond formation and preservation potential.

How to cite: Walsh, C., Kamber, B., and Tomlinson, E.: Deep ultra-hot melting in cratonic mantle roots, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6723, https://doi.org/10.5194/egusphere-egu22-6723, 2022.

In terms of Pb isotope ratios, melting anomalies of Central and East Asia show no high μ (HIMU, high ²³⁸U/²⁰⁴Pb) signature that was generated on the Earth about 2 Ga ago and was caused by sulfide sequestration of Pb from the mantle to the core [Hart and Gaetany, 2006]. In such particular environment, we use Pb isotope data on Late Phanerozoic volcanic rocks to develop general systematics of their sources through definition of initial viscous protomantle reservoirs with low μ and elevated μ signatures (LOMUVIPMAR and ELMUVIPMAR, respectively) that imply a solidification time of the mantle in the Hadean magma ocean between 4.54 and 4.44 Ga ago. We suggest that the protomantle reservoirs retained specific Pb isotope signatures in the early, middle, and late epochs of the Earth's evolution (4.54–3.6, 2.9–1.8, and  <0.7 Ga ago, respectively) [Rasskazov et al., 2020]. In this presentation, we report the first representative Pb isotope data on the ELMU signature of Late Cenozoic rocks from the Dariganga volcanic field, Southeast Mongolia. Pb isotope secondary-isochron patterns of volcanic rocks show protomantle material that was not differentiated between 4.474 and 4.444 Ga (i.e. directly ascended from a deep mantle reservoir in the Cenozoic). In addition, the material was also differentiated in the deep mantle at about 3.69, 2.16, and 1.74 Ga. Pb isotope data on volcanic fields of North China are indicative for lateral change from the ELMU to LOMU signature (Figure). We infer that sources of volcanic rocks from Southeast Mongolia and North China display the primary inhomogeneity of the deep mantle that was generated in the Hadean magma ocean from its initial solidification as early as 4.54 Ga to its final respond of 4.44 Ga.   

Hart, S.R. &  Gaetani, G.A. (2006). Mantle paradoxes: the sulfide solution. Contrib. Mineral. Petrol., 152, 295–308.

Rasskazov, S., Chuvashova, I., Yasnygina, T., & Saranina, E. (2020). Mantle evolution of Asia inferred from Pb isotopic signatures of sources for Late Phanerozoic volcanic rocks. Minerals, 10 (9), 739. 

How to cite: Chuvashova, I., Rasskazov, S., Sun, Y., Yasnygina, T., and Saranina, E.: Lateral change of  ELMU–LOMU sources for Cenozoic volcanic rocks from Southeast Mongolia and North China: Tracing zonation of solidified Hadean magma ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6724, https://doi.org/10.5194/egusphere-egu22-6724, 2022.

The method of cluster (R and G methods) analysis of the allocation of the cluster (CG) and chemical-generic (CGG) groups of average values of the compositions of diamond indicator minerals (DIM) (Ivanov, 2017) was used, supplemented with data on the frequency of occurrence (FO) of habitus forms, twins and clusters of diamond crystals of three kimberlite pipes of Angola – Catoca, Luele and Txiuzo (Ganga et al., 2021). Clustering of MSDS by their chemical composition was carried out on the basis of chemical-genetic classifications of Dowson J. and Soboleva N.V. for garnets (Dowson et al., 1975; Sobolev, 1973) and Garanin V. K. for Cr-diopsides, of ilmenite and chromite (Garanin et al., 1991).

It is found that FO CG/СGG of МSD are indirect and inverse significant correlation with FO habitus forms, twins and adhesion of diamond crystals of these kimberlite pipes. This is demonstrated by histograms of the joint distribution of CG DIM and habitus forms, twins and splices of diamond crystals from geological samples of kimberlites at their deposits (Fig. 1).

The fractions of octahedra (O) and transition habit crystals (OD) decrease in parallel with a decrease in the proportions of CG G9, G10 pyropes and an increase in G1 and G2a, an increase in the proportions of CGG 2b and 4b picroilmenites. The shares of rhombododecahedron, including dodecahedrons (RD), grow with the growth of the shares of CG pyropes G1a, G2a, as well as CGG picroilmenites 2b and CGG Cr-diopsides S2 and S5. The shares of twins (Tw), splices (Agr) and polycrystalline bead (PC) decrease in the studied tubes with a decrease in the shares of CG pyropes G10, G10a and an increase in the shares of CGG picroilmenites 2b and 4b and CGG Cr-diopsides S2 and S5 (Fig. 1). The presence of Ti and Fe compounds, which are part of DIM in elevated concentrations, in the process/medium of diamond crystal formation contributes to the formation of habitus forms OD and RD (D - dodecahedrons) during dissolution associated with low-chromium pyropes CG G1 and G2. Medium-high chromium pyropes CG G10 and G10a are associated with octahedral habitus (O) diamond crystals and their spinel counterparts (TwSp), whose shares they control.

Petrogenetic affiliation of CG/CGG MSD to various associations of deep mantle rocks allows us to identify the most favourable conditions and environments for the origin and growth of diamonds (high FO of O+TwSp+Tw) and environments (conditions) of their dissolution (high FO of OD+RD+Th+C). Interesting that the diamond grade calculated diamond deposits (Ct /T) is positively correlated with FO (Ar g+Tw), SGG S6 picroilmenites and SG G10 garnets, but the FO (RD+OD) has a negative effect on diamond grade, which allows determining the degree of the fertility of the mantle sources by DIM diamond.

How to cite: Zinchenko, V. and Ivanov, A.: Correlation of habitus forms, twins and aggregates of diamond crystals with the composition of its indicator minerals from kimberlite pipes of Angola, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6809, https://doi.org/10.5194/egusphere-egu22-6809, 2022.

Information about the compositions of primitive kimberlite melts is important for understanding the petrogenesis of kimberlites. Reconstruction of the composition of these melts is very difficult because the melts greatly changed their compositions via assimilation of mantle and crust xenogenic materials and degassing during ascent.

To reconstruct the composition of the kimberlite melt of the Bultfontein pipe (Kaapvaal craton, South Africa), the mineral assemblage of secondary melt inclusions in olivines of mantle peridotite xenoliths from the pipe has been studied. The depths of equilibrium of the studied peridotites range from 120 to 150 km.

The inclusions occur along the healed cracks in the olivine grains. Twenty-five daughter minerals were found in the inclusions by Raman spectroscopy and scanning electron microscopy. Liquids and gases were not detected. The inclusions are mainly made up of carbonates (calcite CaCO₃, magnesite MgCO₃, dolomite CaMg(CO₃)₂, eitelite Na₂Mg(CO₃)₂, nyerereite Na₂Ca(CO₃)₂, gregoryite (Na,K,Ca)₂CO₃, K-Na-Ca-carbonate (K,Na)₂Ca(CO₃)₂, shortite Na₂Ca₂(CO₃)₃) or carbonates with additional anions (nahcolite NaHCO₃, bradleyite Na₃Mg(PO₄)(CO₃), northupite Na₃Mg(CO₃)₂Cl, burkeite Na₆CO₃(SO₄)₂, tychite Na₆Mg₂(CO₃)₄(SO₄)). Halides (halite NaCl, sylvite KCl), sulfates (glauberite Na₂Ca(SO₄)₂, thenardite Na₂SO₄, aphthitalite K₃Na(SO₄)₂), phosphate (apatite Ca₅(PO₄)₃(F,Cl,OH)), oxides (rutile TiO₂, magnetite FeFe₂O₄), sulfide (heazlewoodite Ni₃S₂) and silicates (phlogopite KMg₃AlSi₃O₁₀(F,Cl,OH), tetraferriphlogopite KMg₃FeSi₃O₁₀(F,Cl,OH), richterite Na₂Ca(Mg,Fe,Mn,Al)₅[Si₄O₁₁](OH,F)₂) are also present in the inclusions.

These inclusions are considered to be relics of a near‐primary or primitive kimberlitic melt that later formed the Bultfontein pipe. The observed mineral assemblage indicates that the captured melt had an alkali-carbonatitic composition and was rich in Cl and S.

This work was supported by the Russian Foundation for Basic Research (grant No. 20-35-70058).

How to cite: Tarasov, A., Golovin, A., and Sharygin, I.: Reconstruction of the composition of the kimberlite melt of the Bultfontein pipe, Kaapvaal craton, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6844, https://doi.org/10.5194/egusphere-egu22-6844, 2022.

The article considers the geological position of the Zhidoy massif and its age. The scheme of magmatism of the massif has been developed. The graphs of paired correlations of petrogenic elements in massif rocks which had a consistent trend in composition are given for validation purposes. The present article provides graphs of REE spectra and the spider diagram of rare elements concentration in the massif rocks. Pyroxenites are the early rocks of the massif, which are the ores for titanium. Titanium is concentrated in three minerals: titanium magnetite, ilmenite and perovskite. The main type of titanium ores, perovskite, is known only in the Zhidoy massif. A conclusion about the mantle sources of the primary magma of the massif
is drawn based on the geochemistry of the isotopes Sr and Nd.

Fig. 1 Spectra of rare-earth elements in rocks of the Zhidoy massif (chondrite-normalized).
Symbols: 1−pyroxenite, 2−ijolite, 3−syenite, 4−phenite

Fig. 2 Spider-diagram of the Zhidoy massif rocks

Conclusions
1. Three varieties of ore pyroxenites have been defined−titanium-magnetite, ilmenite and perovskite ore.
2. The petrochemical diagrams show a common trend in the composition of rock- forming elements, indicating the homomorphism of the rocks and their crystallization from a single primary magma.
3. Geochemical data also confirm the genetic relation of the Zhidoy massif.
4. Mantle source, the depurated mantle for the primary magma of the Zhidoy massif, has been determined on the basis of isotope data.

How to cite: Sotnikova, I., Vladykin, N., and Alymova, N.: Zhidoy Alkali-Ultramafic Rock and Carbonatite Massif: GeochemicalFeatures, Its Sources And Ore-Bearing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7771, https://doi.org/10.5194/egusphere-egu22-7771, 2022.

International Ocean Discovery Program (IODP) Expedition 357 drilled 17 shallow sites spanning ~10 km in the spreading direction (from west to east) across the Atlantis Massif oceanic core complex (OCC, Mid-Atlantic Ridge, 30°N). Exposed mantle in the footwall of the Atlantis Massif OCC is predominantly nearly wholly serpentinized harzburgite and subordinate dunite. Altered peridotites are subdivided into: (I) serpentinites, (II) melt-impregnated serpentinites, and (III) metasomatized serpentinites. Type I serpentinites show no evidence of melt-impregnation or metasomatism apart from serpentinization and local oxidation. Type II serpentinites have been intruded by gabbroic melts and are distinguishable in some cases based on macroscopic and microscopic observations, e.g., mm-cm scale mafic-melt veinlets, rare plagioclase (˂0.5 modal % in one sample) or by the local presence of secondary (replacive) olivine after orthopyroxene; in other cases, ‘cryptic’ melt-impregnation is inferred on the basis of incompatible element enrichment. Type III serpentinites are characterized by silica metasomatism manifest by alteration of orthopyroxene to talc and amphibole, anomalously high anhydrous SiO₂, and low MgO/SiO₂. Two fundamental features of the mantle serpentinites are identified: (1) A pattern of increasing melt-impregnation from west to east; and (2) a link between melt-impregnation and metamorphism. In regard to (1), whereas a dominant fluid- rock alteration (mostly serpentinization) is distinguished in the western serpentinites, a dominant mechanism of melt-impregnation is recognized in the central and eastern serpentinites. Melt-impregnation in the central and eastern sites is characterized by enrichment of incompatilble elements, Cr-spinel with anomalously high TiO₂ (up to 0.7 wt.%) and olivine forsterite (Fo) compositions that range to a minimum of Fo_86.5.  With respect to (2), in contrast to unmetamorphosed Cr-spinel of western site Type I serpentinized peridotites, spinel of the melt-dominated central and eastern peridotites record metamorphism, which ranges from sub-greenschist (<500°C) to lower amphibolite (>600°C) facies. Low grade, sub-greenschist facies metamorphism resulted in Mg and Fe²⁺ exchange between Cr-spinel and olivine resulting in Cr-spinel with anomalously low Mg# (cationic Mg/(Mg+Fe²⁺)). Higher grade amphibolite facies metamorphism resulted in Al-Cr exchange and the production of Fe-chromite and Cr-magnetite. Heat associated with magma injection and subsequent melt-impregnation resulted in localized contact metamorphism. High degrees of melt extraction are evident in low whole-rock Al₂O₃/SiO₂ and low concentrations of Al₂O₃, CaO, and incompatible elements. Estimates of the degree of melt extraction based on Cr# (cationic Cr/Cr+Al, up to ~0.4) of unaltered Cr-spinel and modeled whole rock REE patterns, suggest a maximum of ~18-20% non-modal fractional melting. As some serpentinite samples are ex-situ rubble, the magmatic histories at each site are consistent with derivation from a local source (the fault zone) rather than rafted rubble that would be expected to show more heterogeneity and no spatial pattern. In this case, the studied sites may provide a record of enhanced melt-rock interactions with time, consistent with proposed geological models for OCC formation.  

How to cite: Whattam, S. A.: Spatial patterns of fluid- and melt-rock processes and link between melt-impregnation and metamorphism of Atlantis Massif peridotites (IODP Expedition 357), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9186, https://doi.org/10.5194/egusphere-egu22-9186, 2022.

Unravelling the processes taking place during the genesis of kimberlites, their ascent through the sub-cratonic mantle and their emplacement in the crust is challenging, as kimberlites are mixtures of mantle-derived and magmatic components, rarely preserving pristine evidence of their original nature. Furthermore, their intense state of alteration makes it difficult to access the textural-compositional record of information engraved in the phase constituents. In this study, fresh samples of kimberlites and related mantle-derived xenocrysts-xenoliths from the Udachnaya pipe (Siberia) were investigated to reconstruct the pressure-temperature-time-composition (P-T-t-X) framework of the sub-cratonic lithosphere at the time of kimberlite emplacement. Routine and high-precision electron microprobe analyses of olivine, phlogopite and spinel from different facies of the Udachnaya pipe (intrusive coherent, hypabyssal and pyroclastic, sensu Scott Smith et al., 2013) showed that specific phase assemblages are associated with each evolutionary stage of the kimberlite. Olivine composition, in particular, is extremely variable, ranging from high-Fo and high-Ni (Fo93; NiO = 0.45 wt%) to low-Fo and low-Ni (Fo85; NiO = 0.10 wt%), but also to high-Fo and low-Ni (Fo>93; NiO <0.05 wt%) terms, often encompassing the whole compositional spectrum in a single sample and/or showing marked zoning within the individual crystals. 
A comparison between the main constituents of the Udachnaya kimberlite and those of the mantle xenoliths sampled during ascent, complemented by detailed major-trace element profiles on olivine crystals, was put forward to: (i) discriminate between the mantle-derived xenocryst cargo and the magmatic assemblage; (ii) model the P-T-fO2 path of kimberlites; (iii) speculate about their ascent rate; (iv) model the interactions between kimberlite-related fluid/melts and the Siberian sub-cratonic lithosphere.

REFERENCES
Scott Smith, B.H., Nowicki, T.E., Russell, J.K., Webb, K.J., Mitchell, R.H., Hetman, C.M., ... & Robey, J.A. (2013). Kimberlite terminology and classification. In Proceedings of 10th international kimberlite conference (pp. 1-17). Springer, New Delhi.

How to cite: Casetta, F., Abart, R., Ntaflos, T., Ashchepkov, I., and Coltorti, M.: Mantle-derived cargo vs. magmatic growth: ascent path, dynamics of the Udachnaya kimberlite and interactions with the Siberian sub-cratonic lithosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9214, https://doi.org/10.5194/egusphere-egu22-9214, 2022.

Large Igneous Provinces (LIPs) represent exceptionally brief (<1 Ma) voluminous magmatic events that punctuate Earth history, frequently leading to continental break-up, global climate changes and, eventually, mass extinctions. Most LIPs emplaced in continental settings are located near cratons, begging the question of a potential control of thick lithosphere on mantle melting dynamics. In this study we discuss the case of the Central Atlantic Magmatic Province (CAMP), emplaced in the vicinity of the thick lithospheric keels of the Precambrian cratons forming the central portion of Pangea prior to the opening of the Central Atlantic Ocean. In particular, we focus on CAMP magmas of the Prevalent group, ubiquitous all over the province, and of the Tiourjdal and High-Ti groups, emplaced (respectively) at the edges of the Reguibat and Leo-Man shields in north-western Africa, and the Amazonian and São Luis cratons in South America. As imaged by recent tomographic studies, there is a strong spatial correlation between most CAMP outcrops at surface and the edges of the thick cratonic keels. Geochemical modelling of trace element and isotopic compositions of CAMP basalts suggests a derivation by partial melting of a Depleted MORB Mantle (DMM) source enriched by recycled continental crust (1-4%) beneath a lithosphere of ca. 80 km. Melting under a significantly thicker lithosphere (>110 km) cannot produce magmas with chemical compositions similar to those of CAMP basalts. Therefore, our results suggest that CAMP magmatism was produced by asthenospheric upwelling along the deep cratonic keels and subsequent decompression-induced partial melting in correspondence with thinner lithosphere. Afterwards, lateral transport of magma along dykes or sills led to the formation of shallow intrusions and lava flows at considerable distances from the source region, possibly straddling the edges of the cratonic lithosphere at depth. Overall, the variations of the lithospheric thickness (i.e., the presence of stable thick cratonic keels juxtaposed to relatively thinner lithosphere) appear to play a primary role for localizing mantle upwelling and partial melting during large-scale magmatic events like the CAMP.

How to cite: Boscaini, A., Marzoli, A., Bertrand, H., Chiaradia, M., Jourdan, F., Faccenda, M., Meyzen, C., Callegaro, S., and Serrano Durán, L.: The architecture of the lithospheric mantle controlled the emplacement of the Central Atlantic Magmatic Province, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9813, https://doi.org/10.5194/egusphere-egu22-9813, 2022.

The Kamthai carbonatites form part of the Sarnu-Dandali alkaline complex (SDAC) of Rajasthan, western India. The SDAC is one of several alkaline intrusive complexes emplaced prior to the Deccan continental flood basalt eruptions. Considered as one of the earliest Deccan-Reunion plume related magmatic activities, the rocks of the complex hold clues to many tectonomagmatic processes such as plume-lithosphere interaction, mantle melting prior to flood basalt volcanism, and carbonatite-plume relationship, apart from the outstanding questions pertaining to the origin of carbonatites themselves, and their association with alkaline silicate rocks. To understand some of these processes vis-à-vis the evolution of the complex, we have carried out a detailed field, petrographic, geochronological (⁴⁰Ar/³⁹Ar), geochemical, and Sr-Nd-Pb-C-O isotopic investigation. Phlogopites from carbonatites yield an age of 68.6 Ma, identical to the ages determined for the three associated phonolite dykes. Interestingly, an earlier study reports the presence of older (89-86 Ma) subvolcanic and volcanic bodies in the complex, thus suggesting recurrent alkaline magmatism. Carbonatites of Kamthai occur as veins, dykes, and small plugs, along with dykes/plugs of ijolite, nephelinite, syenite and phonolite etc. The SDAC intrudes into the basement made up of Malani Rhyolites. The stable C-O isotopic compositions of unaltered carbonatites (δ¹³C_PDB= -6.6 to -4.6 ‰; δ¹⁸O_SMOW=5.5 to 9.5 ‰), which are predominantly calcite carbonatites, not only confirm the magmatic nature of the rocks but also show evidence of fractional crystallization. The chondrite-normalized rare-earth element patterns of the carbonatites and alkaline silicate rocks show LREE enriched patterns, with the former possessing abnormally high contents of LREE. The average (⁸⁷Sr/⁸⁶Sr)_i and ε_Nd(t=68.5 Ma) for carbonatites are 0.7043±0.0001 and 2.4±0.2, respectively, which are indistinguishable from those for the alkaline silicate rocks (⁸⁷Sr/⁸⁶Sr)_i= 0.7045±0.0003; ε_Nd(t)=2.4±0.4), which suggests common parentage. All these data point towards a petrogenetic link between the 68.6 Ma carbonatites and alkaline silicate rocks of the SDAC, either through liquid immiscibility or fractional crystallization of a common parental magma. Overlapping initial Sr-Nd isotopic ratios of these rocks with those of the least contaminated Deccan lava flows and the Reunion island rocks suggest a possible genetic link between the SDAC and the Deccan-Reunion plume. 

How to cite: Mahala, M. K. and Ray, J. S.: Age and geochemistry of the Kamthai carbonatites, Rajasthan, western India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10951, https://doi.org/10.5194/egusphere-egu22-10951, 2022.

Reconstruction of kimberlite melt composition is especially important to understand the processes of mantle-derived magmatism and the Earth’s mantle evolution. This task seems to be very complicated because mantle melts during ascent and emplacement changed their initial characteristics due to degassing and contamination by both mantle and crustal xenogenic materials. Moreover, mantle magmatic rocks are often subjected to secondary alteration. Melt inclusions in minerals of mantle xenoliths can preserve information about the initial characteristics of mantle melts.

Here, we present the results of a study on secondary crystallized melt inclusions in olivines in two partially serpentinized xenoliths of sheared peridotites (AKM-42n and AKM-56) from the Komsomolskaya-Magnitnaya pipe (Upper Muna field, Siberian craton). The mantle residence P–T conditions of AKM-42n and AKM-56 are 6.4 GPa and 1380°C, and 6.7 GPa and 1395°C, respectively.

We identified twenty-one daughter minerals in the melt inclusions using confocal Raman spectroscopy and scanning electron microscopy coupled with energy-dispersive X-ray microanalysis. The minerals within the inclusions are presented by chlorides (sylvite KCl and halite NaCl), silicates (tetraferriphlogopite KMg₃Fe³⁺Si₃O₁₀(OH,F)₂, phlogopite KMg₃AlSi₃O₁₀(OH,F)₂, olivine (Mg,Fe)₂SiO₄, clinopyroxene (Ca,Mg,Fe)₂Si₂O₆, and monticellite Ca(Mg,Fe)SiO₄), carbonates (nyerereite (Na,K)₂Ca(CO₃)₂, shortite Na₂Ca₂(CO₃)₃, eitelite Na₂Mg(CO₃)₂, dolomite CaMg(CO₃)₂, calcite CaCO₃, and magnesite MgCO₃), carbonates with additional anions (burkeite Na₆CO₃(SO₄)₂ and tychite Na₆Mg₂(CO₃)₄(SO₄)), sulphates (aphthitalite K₃Na(SO₄)₂ and thenardite Na₂SO₄), fluorapatite Ca₅(PO₄)₃F, sulfides (pyrrhotite Fe_1-xS and djerfisherite K₆(Fe,Ni,Cu)₂₅S₂₆Cl) and magnetite FeFe₂O₄.

The studied melt inclusions are considered to be relics of a near‐primary or primitive kimberlite melt that formed the Komsomolskaya-Magnitnaya pipe. The assemblage of the daughter minerals indicates that the melt had an alkali-carbonatitic composition and was enriched in Cl and S.

This work was supported by the Russian Foundation for Basic Research (grant No. 20-35-70058) and the Russian Science Foundation (grant No 18-77-10062).

How to cite: Kalugina, A., Sharygin, I., Solovev, K., Golovin, A., and Dymshits, A.: Composition of the kimberlite melt of the Komsomolskaya-Magnitnaya pipe (Upper Muna field, Siberian craton), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10980, https://doi.org/10.5194/egusphere-egu22-10980, 2022.

The problem of the lithospheric mantle structure under ancient cratons and their evolution attracts researchers in connection with the question of the diamond genesis. The petrological way is based on the mineral composition studying in xenoliths from the mantle depths. The Mirny kimberlite field belongs to the diamond-bearing kimberlite fields in the center of the Siberian craton. The authors studied a collection of mantle xenoliths from the Mir pipe (57 samples). The samples were classified as peridotites (Grt lherzolites) and pyroxenites (Grt websterites, Grt clinopyroxenites and eclogites).

Lherzolites from the Mir pipe are characterized by a high degree of alteration; olivine and orthopyroxene are replaced by serpentine in many samples (up to 50–70%). Websterite rocks are different by the presence of orthopyroxene and clinopyroxene, while clinopyroxene may contain lamellae of exsollution structures. Garnet websterites are distinguished by orange-reddish color of garnet, dark green color of pyroxene and dominanting medium-large-grained hypidiomorphic-granular textures; porphyroblastic and granoblastic textures (up to mosaic) are also observed. In garnet clinopyroxenites rutile is usually present in the form of thin (5–20 µm) needles in garnet and clinopyroxene. Eclogites are characterized by orangish or pinkish garnet color and granoblastic structure.

Garnets from lherzolites and websterites are also characterized by a relatively high Mg# content (75–83) and low TiO₂ contents (up to 0.2 wt %). It belongs to the lherzolite paragenesis by content CaO (3.68 - 5.35 wt.%) and Cr₂O₃ (0.07-3.7 wt.%). Eclogites are characterized by high-calcium (3.78 - 9.46 wt.%) and high-iron (7.77 - 17.20 wt.%) composition of garnet getting into the ​​wehrlite paragenesis area. None of the garnet studied compositions belongs to the high-chromium dunite - harzburgite paragenesis. Also garnets from the lithospheric mantle under the Mirny kimberlite field are characterized by a low-Ti garnet composition (up to 0.7 wt.%). Thus, the lithospheric mantle under the Mirny kimberlite field differs from the lithospheric mantle under other diamondiferous fields (for example, Udachnaya kimberlite pipe). The Mirny mantle xenoliths are characterized by the pyroxenites widespread development (up to 50%), the low-Ti composition and deformed lherzolites absence. These features indicate the minimal silicate metasomatic alteration in the lithospheric mantle under the Mirny field (in contrast to the center of the Siberian craton). The isotopic oxygen composition in garnet and clinopyroxene was also determined. The δ¹⁸O value varies in Cpx from 5.7-5.8‰ in clinopyroxenites and 6.1-6.1‰ in eclogites. On the whole, minerals from pyroxenites demonstrate δ¹⁸O values exceeding mantle values, which suggests a wide development of melting processes in the lithospheric mantle in the south of the Siberian craton Craton and the formation of megacrystalline pyroxene cumulates. In some cases, metamorphic recrystallization leads to oxygen isotope equilibrium between garnet and clinopyroxene. For minerals from eclogites higher values ​​of δ¹⁸O are noted, which may indicate the origin of eclogites from subducted oceanic crust, the presence of a subduction component in the process of formation of the lithospheric mantle.

The research was supported by Russian Science Foundation grant №20-77-00074.

How to cite: Kalashnikova, T., Kostrovitsky, S., Solovieva, L., Sinitsyn, K., and Yudintseva, E.: Garnets from xenolith in Mir kimberlite pipe: chemical composition and genesis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11936, https://doi.org/10.5194/egusphere-egu22-11936, 2022.

Orogenic garnet peridotites exhumed in ultrahigh-pressure-ultrahigh-temperature terranes represent windows into material transfer in deep subduction zones. Multiphase solid inclusions (MSI) trapped in garnet proved to be important tracers of metasomatism by crustal-derived fluids. Our study of the MSI from the Saxothuringian basement in the Bohemian Massif, European Variscan Belt, allowed identifying the source and evolution of the liquids metasomatized the mantle rocks. As the MSI could not be re-homogenized due to a high content of volatiles, their bulk composition was estimated considering the proportions, phase densities and chemical composition of the constituent minerals.

The MSI occur in an annulus at garnet rim of garnet lherzolite and harzburgite, and throughout garnet in garnet pyroxenite. The major phases of the MSI include amphibole, barian mica and carbonate (dolomite, magnesite). Minor phases are clinopyroxene, orthopyroxene, garnet II, spinel, apatite, monazite, thorianite, graphite, pentlandite, scheelite and sulphides. The proportion of hornblende systematically decreases from pyroxenite and close harzburgite and lherzolite to more distal mantle rocks, where clinopyroxene and garnet II occur instead. By contrast, the amount of barium-bearing phases (barian mica, Ba-Mg carbonate norsethite, barian feldspar) and carbonates increases in the same direction.

Major element composition of garnet pyroxenite, including enrichment in alkalies and barium, approaches carbonate-silicate melts similar to kimberlites.  Trace element signatures indicate that it is a rare example of low-degree supercritical liquid derived from a mixed crust-mantle source frozen in the mantle. The MSI hosted by garnet in pyroxenite represent a residual solute-rich liquid after high-pressure fractional crystallization of the parental melt, enriched in alkalies (Na, K), highly incompatible elements (LILE – Ba, Sr; Th, U), LREE, Ti, W and volatiles (CO₂, Cl, F, P). The MSI in peridotites allow tracing the changes of this metasomatizing liquid during its reactive infiltration into peridotite through silicate crystallization as well as interaction with mantle minerals distinct in lherzolite and harzburgite (garnet±clinopyroxene). The liquid evolved from more silicic, solute-rich to more diluted carbonate-rich, with gradual enrichment in LILE (K, Ba) and volatiles (CO₂, Cl) and LREE fractionation, similar to evolution of kimberlitic to carbonatitic melts through differentiation by fractional crystallization.  

Here we demonstrate that the MSI trapped in garnet can be used as a unique tool for tracing chemical evolution of the liquids metasomatizing the mantle wedge. Importantly, these results are valid even in the case of the interaction of the trapped material (MSI) with the host garnet, as this potential contamination mainly concerns Al, Si and Cr while majority of the other elements used for petrogenetic implications remained unaffected

How to cite: Kotkova, J., Čopjaková, R., and Škoda, R.: Source and evolution of metasomatizing liquids in orogenic peridotites: evidence from multiphase solid inclusions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13248, https://doi.org/10.5194/egusphere-egu22-13248, 2022.

Singhbhum Craton, eastern India, exposes an array of Paleoarchean granitoids (e.g., TTGs and diorites, transitional TTG, and K-rich granite) ranging in age from ~3.53─3.25 Ga, thus making it a suitable archive for understanding crustal architecture and dynamics during that era. Granitoids cover the core of the craton as a composite dome and are fenced by keels of contemporaneous iron ore bearing greenstone belts from east, west, and south giving rise to a dome-and-keel architecture.  Change in granitoid chemistry and isotope signature over time and space can provide a window into the change of crustal evolution mechanism as well as geodynamics of the crust formation if put into a robust tectonic framework. Most of such earlier studies addressed the secular evolution of granitoid chemistry and isotopic changes as an expression of a shift in tectonic paradigms. This tectonic shift is explained broadly as a response to a progressively cooling earth. However, the timing of the transition (advent of a new tectonic setting) varies globally; hence, each craton needs to be studied separately and without any prior bias.

Spatial variation represented by contour diagrams from the cratonic core show two distinct areas exposing dominantly 3.35–3.25 Ga high-silica, low-magnesiam, high K₂O/Na₂O (K/Na>0.60) granitoids of shallow crustal origin, indicated by their low pressure-sensitive ratios (eg. Eu/Eu*, Sr/Y, Gd/Er, La/Yb). These two areas are surrounded by older intermediate granitoids (>3.35 Ga TTGs). Based on the spatial distribution, it is being suggested that these spatial arrangement of granitoids are related to “partial convective overturn (PCO)” process where the >3.35 Ga TTG basements were subjected to greenstone load while they were soft. As a result some part of the newly formed softer >3.35 Ga TTG crust melted as these overburdens helped in bringing the TTGs to a potential melting depth. The greenstones then sank into the partially molten TTGs along steep-dipping sinistral shear zones by forming synformal keels. The moderate- to- low-pressure TTG-derived partial melts then rose to the shallower level and formed the 3.35–3.25 Ga high-silica, low-Mg# potassic granitoids.

Preserved rock record in the Singhbhum Craton indicates that the granitoid magmatism started at ~3.47 Ga with emplacement of high-silica, low alumina tonalite, characterized by low Sr/Y, (Gd/Er)_N, (La/Yb)_N, Eu/Eu* and Sr. The 3.47 to 3.32 Ga TTG record from the Singhbhum Craton show a progressive increase in Al₂O₃, Sr/Y, (Gd/Er)_N, (La/Yb)_N, Eu/Eu* and Sr and decrease in Na₂O. The increase in the pressure-sensitive ratios reached peak during 3.32 Ga and then started decreasing until ~3.28 Ga followed by another increase during ~3.28 to ~3.25 Ga before ceasing of Paleoarcehan magmatism in the Singhbhum Craton. Such variation in geochemical tracers is explained in terms of episodic crustal thickening by periodic mantle upwelling and associated delamination along with time-progressive changes in bulk chemical composition of the continental crust from mafic to felsic.

How to cite: Mitra, A. and Dey, S.: Time-space evolution of an ancient continent, a window to crustal evolution: Insight from granitoids of Singhbhum Craton, eastern India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-594, https://doi.org/10.5194/egusphere-egu22-594, 2022.

Biogenicity and taphonomy of the early life fossil records are debated as most of the previous studies focussed mainly on isotopes geochemistry. The non-metamorphosed Paleoproterozoic (~2.1 Ga) sedimentary succession of the Francevillian Basin (Gabon) contains the oldest complex multicellular organisms embedded in black shale facies. Several studies have confirmed the biogenicity of these soft-bodied organisms. Here, we used multi-proxy techniques to show that the preservation of these macro-organisms happened in a close system that limits interaction with their host rocks, which leads to their good preservations. The macro-organisms are present in different shapes and sizes: lobate (L), elongate (E), tubular (T), segmented (S), and circular (C), and are often associated with bacterial mats. Except for the C form, most of the other specimens are pyritized. Sulfur isotopes data confirms that pyritization occurred by bacterial sulfato-reduction during early diagenesis. We compare the clay mineral assemblages between the pyritized specimens and the late-diagenetically formed pure pyritized concretions in the sediments because the early pyritization process could not explain the taphonomic preservation alone. Our clay mineralogical data show that the specimens are dominated mainly by randomly mixed layer Illite-smectite (IS MLMs), illite, and chlorite relative to the host rocks. The abundance of IS MLMs indicates incomplete illitization of smectite, potassium deficiency, and limited mineral reactions in a semi-close local chemical system within the fossils.  In addition, the authigenic chlorites are more iron-rich and show vermicular habitus. By contrast, the pyritized concretions mainly consist of well-crystallized illite and less iron-rich chlorite, while the smectite phases are absent. These results confirmed that the diagenetic reaction is controlled by interaction with an open late diagenetic system. We concluded that taphonomic preservation of the ancient fossil record resulted from the early diagenetic growth of pyrite crystals during bacterial sulfato reduction in the fossils, which creates a semi-closed system that drastically reduced fluid-rock interactions with the host sediments.

How to cite: Ngwal Ghoubou Ikouanga, J. A., Fontaine, C., M. Bankole, O., Laforest, C., Riboulleau, A., Trentesaux, A., Boissard, C., Somogyi, A., Meunier, A., and El Albani, A.: Taphonomy of early life: Role of organic and mineral interactions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-955, https://doi.org/10.5194/egusphere-egu22-955, 2022.

The Precambrian comprises the vast majority of Earth’s history. Preserved archives contain essential information about the first few billion years for planetary evolution of our planet. Despite covering a large part of the history of our planet, these outcrops are not so abundant due to erosion and frequently occur in disparate areas. In order to relate them and to establish a timeline of geological events in a world lacking biochronology, we rely on accurate radio-isotopic age determinations. These are, however, rather scarce and still leave several hundreds of million years long time intervals undated. In this study, we present U-Pb age determinations from volcanic and sedimentary units of the Paleoproterozoic Transvaal Supergroup, South Africa. The Transvaal Supergroup is an exceptionally well preserved sequence and therefore accounts for a very large amount of geochemical data. Due to its capacity to produce large data sets the preferred technique in U-Pb zircon geochronology for ancient sediments is LA-ICP-MS. It allows the aqcuisition of maximum depositional ages (MDA) in a fast way and at a relatively low cost. However, the large analytical uncertainty preclude the temporal resolution to distinguish between different processes in such old rocks. Moreover, the standard dating procedure rarely includes zircon treatment via chemical abrasion to mitigate common problems such as open system behavior due to radioactive decay damage related Pb loss. In consequence, interpreted ages might be severely disturbed and may yield MDA’s that are tens to hundreds of million years too young. As an alternative, the much more work-intensive CA-ID-TIMS technique allows the obtention of more accurate and more precise ages, preferably using zircon grains that have previously been screened for their LA-ICP-MS U-Pb age.

 Our new combined LA-ICP-MS and CA-ID-TIMS data indicates that the glaciogenic Makganyene Formation has a MDA of ~2.42 Ga. Younger age clusters at around ~2.2 Ga from LA-ICP-MS dating disappear with chemical abrasion and have to be interpreted as artifacts of radiation-damage related Pb loss. These new results have important implications for both environmental evolution during the Neoarchean/Paleoproterozoic, as well as for the regional geology. The Makganyene diamictites are thought to represent the oldest Paleoproterozoic glaciation in South Africa. The data also corroborate the hypothesis that the directly overlying-to-locally-interfingered mafic volcanic Ongeluk Formation is ~200 Ma older than the volcanic rocks ~2250 Ma Hekpoort Formation in the East Transvaal basin. We therefore reject the long-standing correlation between both units, as previously published.

We demonstrate that LA-ICP-MS is not capable to provide a robust and reliable MDA’s in ancient clastic sediments. CA-ID-TIMS analysis provides dates of significantly higher accuracy, because the chemical abrasion is minimizing Pb-loss in the crystal. Therefore, for studies relying on U-Pb zircon geochronology, we encourage the application of CA-ID-TIMS in the youngest populations previously identified with the LA-ICP-MS. This is particularly important for establishing reliable maximum depositional ages in sedimentary rocks.

How to cite: Senger, M. H., Davies, J., Ovtcharova, M., Beukes, N., Gumsley, A., Gaynor, S. P., Ulyanov, A., and Schaltegger, U.: U-Pb zircon geochronology combining both in-situ and bulk-grain techniques in the Transvaal Supergroup, South Africa., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1666, https://doi.org/10.5194/egusphere-egu22-1666, 2022.