EGU General Assembly 2023  

For more than 30,000 years, humans have been able to characterise materials, so they could choose the best for making tools, jewellery, shelter and clothing. For more than 300 years, scientists and craftsmen have known enough about fluids to characterise them and use them, even if they never succeeded in precipitating gold from solutions of lead. However, it has only been the last 30 years that we have been able to characterise the composition and structure of the mineral-fluid interface with techniques that can "see" at the nanometre scale and to simulate interactions from first principals. Once one can understand the mechanisms that control the solid-fluid interface, one can control the material’s properties and its behaviour. This is the key to designer materials and solving challenges in nature.

My journey into the nanometre scale world of interfaces began with demonstrating that the surface of a calcite crystal is not simply a termination of the bulk structure. Instead, it is a defect, where the atoms at the interface are restructured. In response to fracture in a vacuum or in contact with gas, water or organic compounds, the atoms of the mineral surface rearrange and the molecules in the fluid in contact organise themselves to delocalise charge differences between each other and with the surface. This plays a role in the behaviour of adsorbates. In turn, ion and organic compound adsorbates can modify surface properties, dramatically changing behaviour, even at tiny fractions of a monolayer. Understanding mineral-fluid-organic compound interactions gives us a powerful tool, the ability to predict behaviour and to control reactions.

Work in my group shows that the character of simple organic compounds, i.e. their functional group(s), size and branching, determine their adsorption energy on calcite. Density functional theory simulations match very well with adsorption energy determined with X-ray photoelectron spectroscopy. If we can define such relationships for other mineral systems, it could lead to a whole new conceptual framework for describing and predicting mineral-water-organic compound reactivity.

How to cite: Stipp, S.: Mineral-fluid reactivity: The action is at the interface, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17120, https://doi.org/10.5194/egusphere-egu23-17120, 2023.

Metamorphic rocks are composed of minerals formed within a wide range of pressure-temperature (P-T) conditions. These minerals possess distinct physical properties with respect to their thermo-elasticity, viscosity and plasticity etc. When far-field nonhydrostatic stress was present during tectonic deformation or the P-T conditions were changed during burial or exhumation processes, grain-scale stress variation can be developed to maintain mechanical equilibrium. The induced stress variations can also be released over geological time. The magnitude, effect and geological implications of the preserved stress variations have been investigated and better understood in recent years, but a lot remains to be explored. It is important because it may as well open an opportunity to decipher the overseen information stored in the rock that is difficult to be detected or achieved with conventional methods.

The geological implication of grain-scale stress variation is directly manifested by a simple mineral inclusion-host system, such as quartz or zircon inclusion in garnet. The different thermal-elastic response between the inclusion and host upon P-T changes will result in a residual stress stored in an entrapped mineral inclusion. The inclusion stress (strain) can be directly measured with e.g. Raman spectroscopy. Combined with an elastic model, it is possible to obtain constraints on the entrapment P-T conditions. This elastic thermobarometry technique has been applied in many recent petrological studies because no global or local chemical equilibrium assumption is needed. However, it relies on the inclusion-host system being elastic and neglects the non-elastic behavior of minerals. As an example, I will present an integrated observational, experimental and numerical modelling work that highlights the importance of considering non-elastic behaviour of the mineral. The heating experiment shows that under conditions at which free fluid is present, a garnet host will be drastically weakened and partially release the inclusion pressure. This is further correlated with a nappe-scale study in the Adula nappe, Alps. A smooth T gradient is found increasing from the north (500-550 ^oC) to the south (700 ^oC) using the Zr-in-rutile thermometer. However, the entrapment P calculated with the quartz inclusion in garnet barometer demonstrate a GPa level steep drop in the middle-south, where the rocks have been hydrated during retrograde metamorphism and abundant micro-hydrous inclusions (e.g. chlorite, amphibole) are found in the garnet. It is interpreted that a combined effect of temperature and water fugacity will drastically speed up the inclusion pressure relaxation on a regional metamorphic scale. In the end, it is highlighted that mechanics with non-elastic stress-strain (rate) relationships are potentially needed when dealing with the generation and dissipation of the stress variations in metamorphic rocks that underwent retrograde hydration or very high T conditions to better extract geological information.

How to cite: Zhong, X.: The generation, dissipation and geological implication of grain-scale stress variation in metamorphic rock, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9133, https://doi.org/10.5194/egusphere-egu23-9133, 2023.

The erosion of mountain landscapes is the greatest source of terrestrial sediment to global ocean basins and a critical part of the global carbon cycle regulating Earth’s climate over geologically relevant timescales. In particular, the expansion of mountain glaciers may accelerate bedrock erosion and rapidly increase the flux of terrestrial sediment from source areas. However, the mechanisms by which glaciation augments sediment flux are complex, and understanding them requires further research. Our research adopts a novel approach to determine the source of sediment in rivers exiting a glaciated landscape, combining detrital zircon fission-track “tracer” thermochronology and Raman spectroscopy of carbonaceous material (RSCM). Our research focuses on the Southern Alps of New Zealand as a model landscape with well-constrained lithology and a predictable exhumation gradient. In 5 west-draining transverse river catchments, we test the hypothesis that modern sediment is preferentially derived from glaciated, high-elevation areas of the catchment. Our 5 rivers span a range of glacial coverage, allowing us to further test the hypothesis that glacially-sourced sediment increases with the degree of glaciation in the catchment. Our preliminary results suggest that sediment is not exclusively derived from glaciated areas of the catchment, but may instead reflect additional deglaciated source areas affected by landsliding, possibly induced by seismicity along the Alpine Fault. Our research demonstrates a powerful and novel approach to tracing sediment sources within an individual catchment area and highlights complex interrelationships between mountain glaciation and changes in the magnitude and sources of sediment fluxes.

How to cite: Harris, D.-A., Lang, K., Roda Boluda, D., and Kurth, M.: Tracing sediment source within a glaciated landscape: new observations from detrital thermochronology and Raman spectroscopy in the Southern Alps of New Zealand, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-581, https://doi.org/10.5194/egusphere-egu23-581, 2023.

Constraining precise ages for impact events is crucial in establishing Earth’s history, and several geochronometers have been developed to date impacts. We present electron backscatter diffraction (EBSD), sensitive high-resolution ion microprobe (SHRIMP) and atom probe tomography (APT) data from shocked xenotime [(Y,HREE)PO₄] collected from two impact sites to investigate the potential of xenotime as an impact geochronometer. A detrital xenotime grain from the Vredefort dome (South Africa) contains planar fractures, planar deformation bands and {112} twinning, the latter of which are diagnostic shock microstructures. However, APT analysis from the twin domains and also from the host yielded no evidence of Pb mobility at the nanometer scale during the impact. SHRIMP analysis (n=24) on the grain yielded a discordia with an upper intercept of 3136 ± 110 Ma and an imprecise lower intercept of 1793 ± 280 Ma. These correspond, respectively, to the bedrock age and a post-impact, cryptic terrane-wide fluid infiltration event. Three neoblastic grains from the Araguainha dome (Brazil) experienced partial to complete recrystallisation. The least recrystallised grain yields the oldest ²³⁸U/²⁰⁶Pb age of 479 ± 26 Ma, whereas a completely recrystallised neoblastic grain gave an age of 257 ± 11 Ma.  APT analysis on the latter grain showed different nanoscale features that shed light on Pb mobility during shock deformation and recrystallisation.  Based on observations of nanoscale Pb mobility and the correlation between recrystallisation and isotopic resetting, and prior published ages, we interpret 257 ± 11 Ma to date the impact event. These data confirm that recrystallised neoblastic xenotime is a useful impact geochronometer. 

How to cite: Joseph, C., Fougerouse, D., J. Cavosie, A., K. H. Olierook, H., M. Reddy, S., R. Quintero, R., Kennedy, A., W. Saxey, D., and D.A. Rickard, W.: Shocker: xenotime can date impacts, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1082, https://doi.org/10.5194/egusphere-egu23-1082, 2023.

Determining the crystallization of S-type granitic material can be challenging due to a lack of neoblastic zircon growth (e.g. thin overgrowths) and the potential of large inherited zircon cargos. Coupled apatite–zircon geochronology can help address such complexities and also clarify post-magmatic thermal history, given the disparate Pb closure temperatures in these minerals. Here we present a case study on the Johnston Complex, a rare outcrop of the Precambrian basement in southern Britain, representing a window into the tectonic regime of Avalonia. Zircon and apatite yield identical U-Pb ages, within uncertainty, of 569 ± 2 Ma and 576 ± 11 Ma, respectively. A minor antecrystic zircon core component is identified at 615 ± 11 Ma. Given the previously reported zircon U-Pb age of 643 Ma, these results demonstrate that the Complex represents a composite suite of plutons along its ca. 20 km length. Zircon Lu-Hf data imply a broadly chondritic source, with model ages consistent with crustal extraction during Rodinia formation. Zircon trace elements are consistent with a calc-alkaline continental magmatic arc setting. Whilst, apatite trace elements demonstrate a sedimentary component within the melt. Combined, these results support arc granite production within the peri-Gondwanan realm during amalgamation of Eastern Avalonia and associates the Johnston Complex to the Cymru subterrane. Importantly, congruent zircon–apatite ages imply rapid cooling after crystallisation, and that subsequent thermal heating did not exceed the apatite Pb closure temperature.

How to cite: Clarke, A., Kirkland, C., and Glorie, S.: A detective duo; an apatite–zircon case study of the Johnston Complex, Wales, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1147, https://doi.org/10.5194/egusphere-egu23-1147, 2023.

Qinling Orogenic Belt with its Meso-Cenozoic intracontinental orogeny and uplift, is a key physiographic element that characterized the differential evolution of the geology, geography and climate in continental China (Dong et al., 2022). However, numerous thermochronological dates of the Qinling bedrocks (Dong et al., 2011; Yang et al., 2017) show that there is a wide cooling gap between Triassic and Early Cretaceous. In this study, we studied this gap by multiple geochronology and geochemistry on Lower Cretaceous molasse granitic gravel samples, with the aim to recover the hidden Mesozoic exhumation history. We report the first detailed zircon U-Pb ages, whole-rock major and trace elements and Sr-Nd-Pb isotopic data, which suggest that these clasts derive from Late Triassic I-type granites which were emplaced in a syn-collisional setting during a subduction phase. Their provenances were also determined by comparison with the geochemical fingerprint of Qinling granitic bedrocks. New zircon and apatite U-Pb, (U-Th)/He and fission-track data, as well as biotite ⁴⁰Ar-³⁹Ar, were performed on the granitic gravels dated between ca. 222 Ma to 110 Ma. Thermal history modeling, based on the multiple geochronological data, shows rapid cooling from ca. 700 °C to 200 °C during Late Triassic-Early Jurassic, then followed by a period of slow cooling from Middle Jurassic to Early Cretaceous.

As a whole, our new multiple geochronological and geochemical data and the related thermal history modeling results provide new insights on the prolonged pre-Cenozoic cooling history as well as the intracontinental deformation of the Qinling, which were mostly related to Paleo-Tethyan subduction and Late Triassic North China-South China Block collision.

Reference:

Dong, Y., Genser, J., Neubauer, F., Zhang, G., Liu, X., Yang, Z. and Heberer, B., 2011. U-Pb and 40Ar/39Ar geochronological constraints on the exhumation history of the North Qinling terrane, China. Gondwana Research, 19(4): 881-893.

Dong, Y., Sun, S., Santosh, M., Hui, B., Sun, J., Zhang, F., Cheng, B., Yang, Z., Shi, X., He, D., Yang, L., Cheng, C., Liu, X., Zhou, X., Wang, W. and Qi, N., 2022. Cross Orogenic Belts in Central China: Implications for the tectonic and paleogeographic evolution of the East Asian continental collage. Gondwana Research, 109: 18-88.

Yang, Z., Shen, C., Ratschbacher, L., Enkelmann, E., Jonckheere, R., Wauschkuhn, B. and Dong, Y., 2017. Sichuan Basin and beyond: Eastward foreland growth of the Tibetan Plateau from an integration of Late Cretaceous-Cenozoic fission track and (U-Th)/He ages of the eastern Tibetan Plateau, Qinling, and Daba Shan. Journal of Geophysical Research: Solid Earth, 122(6): 4712-4740.

How to cite: Peng, H., Wang, J., Liu, C., Li, J., Jiao, X., Zhang, L., and Zattin, M.: Revealing the hidden Mesozoic exhumation history of the Qinling orogenic belt, Central China: insights from multiple geochronological and geochemical data of the molasse granitic gravels, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1262, https://doi.org/10.5194/egusphere-egu23-1262, 2023.

Active graben systems in south Tibet and the Himalaya are the expression of ongoing E-W extension, however, the cause and spatio-temporal evolution of normal faulting remain debated. We reconstruct the history of normal faulting at the southern Tangra Yumco graben by using new thermochronological data and thermo-kinematic modelling (Wolff et al., 2022). The Miocene cooling history of the footwall of the main graben-bounding fault is constrained by zircon (U-Th)/He ages between 16.7±1.0 and 13.3±0.6 Ma, apatite fission track ages (15.9±2.1 to 13.0±2.1 Ma), and apatite (U-Th)/He ages (7.9±0.4 to 5.3±0.3 Ma). Thermo-kinematic modelling of the data indicates that normal faulting began 19.0±1.1 Ma ago at a rate of ~0.2 km/Myr and accelerated to ~0.4 km/Myr at ~5 Ma. In the northern Tangra Yumco rift, re-modelling of published thermochronological data (Wolff et al., 2019) shows that faulting started ~5 Ma later at 13.9±0.8 Ma. The age difference and the distance of 130 km between the two sites indicates that rifting and normal faulting propagated northward at an average rate of ~25 km/Myr. As this rate is similar to the Miocene convergence rate between India and south Tibet, we argue that the under-thrusting of India beneath Tibet has exerted an important control on the propagation of rifts in south Tibet.

References

Wolff, R., Hetzel, R., Hölzer, K., Dunkl, I., Xu, Q., Anczkiewicz, A.A., Li, Z. (2022). Rift propagation in south Tibet controlled by underthrusting of India: A case study at the Tangra Yumco graben (south Tibet). J. Geol. Soc. Lond., https://doi.org/10.1144/jgs2022-090.

Wolff, R., Hetzel, R., Dunkl, I., Xu, Q., Bröcker, M. & Anczkiewicz, A.A. (2019). High-angle normal faulting at the Tangra Yumco graben (southern Tibet) since ~15 Ma. J. Geology, 127, 15–36, http://doi.org/10.1086/700406.

How to cite: Hetzel, R., Wolff, R., Hölzer, K., Dunkl, I., Xu, Q., Anczkiewicz, A., and Li, Z.: Rift propagation in south Tibet controlled by under-thrusting of India: A case study at the Tangra Yumco graben (south Tibet), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1407, https://doi.org/10.5194/egusphere-egu23-1407, 2023.

Silicic magma flare-up episodes are characterized by the addition of large volumes of evolved magma (>65 wt% SiO₂) to the continental crust in geologically short time intervals (10⁶-10⁷ years). Flare-up events are often associated with (trans-)extensional tectonics and contribute to crustal differentiation and critical metal mineralization. Related volcanic aerosol dispersion in the atmosphere can also trigger global environmental changes. During flare-up episodes, long-lived caldera complexes are thought to be primary eruptive sources at the Earth’s surface. However, a substantial proportion of the overall mobile magma can be trapped in extra-caldera dikes, fissures and monogenetic edifices controlled by the extensional stress regime.

In the Southern Alps of Northern Italy, a post-Variscan magmatic flare-up is recorded in a ca. 400 km long array of largely undeformed magmatic bodies of Early Permian age (285-275 Ma; [1]), then located along the northern margin of Gondwana. In the Southern Alps this flare-up produced more than 5*10⁴ km³ of rhyolitic volcanic and cogenetic intrusive rocks. Two major caldera complexes (Sesia Caldera; Ora Caldera) were capable of ejecting volumes >10³ km³ of magma during individual catastrophic eruptive events. However, magmatic activity also resulted in numerous scattered volcanic centers with relatively small eruptions (0.1 – 1 km³ each) and punctuated by quiescent intervals.

In this study we focus on two Early Permian fault-bounded basins, ca. 40 km apart, in the central Southern Alps: the Orobic Basin (Bergamo) and the Collio Basin (Brescia). The stratigraphic records of both basins preserve proximal and distal volcanic products and both successions terminate with erosional unconformities of Middle- to Late Permian age. New zircon LA-ICP-MS U-Pb ages indicate that the onset of explosive, rhyolitic magmatism was essentially coeval at ~284 Ma. The Collio Basin contains just a few ignimbrite sheets dispersed in an essentially (fluvio)-lacustrine sedimentary fill and recording a pulsated volcanic activity of nearly 5 Myr (youngest ignimbrite ~280 Ma). After an initial phase (1-2 Myr) of a similar pulsed nature, the Orobic Basin became the locus of extrusion of much larger volumes of rhyolitic magma (probably in excess of 100 km³) in less than 1 Myr (283-282 Ma). This was followed by a depositional style similar to the Collio but with a scarcer pyroclastic contribution.

The contrasting volcanic record in these two basins, which share size and tectonic environment but not magmatic evolution, provides a striking example of magmatic architecture diversity in the midst of a silicic flare-up event. Further investigation into the timing (CA-ID-TIMS U-Pb geochronology) and compositional evolution (e.g., zircon d¹⁸O, e_Hf) of volcanic products in the Collio and Orobic basins is expected to provide a much better resolved comparison and open a window into the combined tectono-magmatic processes that ultimately regulate the size and frequency of catastrophic, caldera-forming eruptions in silicic flare-up provinces.

[1] Schaltegger, U., & Brack, P. (2007). International Journal of Earth Sciences, 96(6), 1131-1151.

How to cite: Tavazzani, L., Szymanowski, D., Forni, F., Cadel, G., and Brack, P.: Magmatic architecture and basin evolution in the midst of a silicic flare-up: U-Pb zircon geochronology of volcanic deposits from two Early Permian, Collio-type basins of Southern Alps (Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1426, https://doi.org/10.5194/egusphere-egu23-1426, 2023.

The rate of cooling of metamorphic rocks provides a first-order constraint on the tectonic processes controlling heat flow and exhumation. For example, for small crustal terranes that were subducted to ultrahigh pressure conditions during the early stages of collisional orogenesis, exhumation is generally fast with rates similar to plate velocities, such that cooling is also rapid. Similarly, rates of cooling are commonly fast (generally ~20–30°C/Myr) during exhumation of metamorphic core complexes or due to transpression. By contrast, cooling in some granulite terranes can be slow and close-to-isobaric, leading to time-integrated cooling rates of <5°C/Myr. The implication of such slow rates of cooling is that these granulite terranes were close to isostatic equilibrium as a result of sustained high mantle heat flow that limited exhumation by erosion. However, constraining initial cooling rates in granulite terranes can be difficult, particularly where the rocks reached ultrahigh temperatures (>900 °C) that exceed the closure temperature of many geochronometers. In order to overcome this difficulty, we combine U–Pb zircon geochronology with Ti-in-zircon thermometry to investigate the thermal history of metapelitic rocks from the Eastern Ghats Province of eastern India. For the combined dataset of metamorphic zircon from the samples, concordant dates decrease continuously within 2σ uncertainty from around 950 Ma to 800 Ma, consistent with c. 150 Ma of zircon crystallization. Ti-in-zircon temperatures for each dated spot during this period decrease with age, corresponding to linear cooling rates ranging from 0.26 to 0.90°C/Myr. We propose that retention of heat producing elements in the lower crust of the Eastern Ghats Province and a low net erosion rate were responsible for c. 150 Myr of ultra-slow cooling. The location of the Eastern Ghats Province on the margin of the supercontinent Rodinia may have been a contributing factor enabling the region to remain relatively undisturbed until it was exhumed during the formation of Gondwana.

How to cite: Clark, C., Brown, M., Johnson, T., Mitchell, R., and Gupta, S.: Ultra-slow cooling of ultra-hot orogens, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1931, https://doi.org/10.5194/egusphere-egu23-1931, 2023.

Trace elements in zircon are a promising proxy to quantitatively study long-term Earth’s lithospheric processes and its geodynamic regimes. The zircon Eu anomaly reflects the crystallization environment of its felsic or intermediate parental magma. It specifically provides insight into the water content, magmatic redox conditions, and the extent of pla­gioclase fractionation in the source rock or its occurrence as a cogenetic crystallizing phase from the magma. We performed a statistical analysis of Eu anomaly from a global compilation of detrital zircons and display it as a timeseries and found a major decrease in Eu anomaly ca. 2.5 Ga and an important increase ca. 0.9 Ga. Combining these trends with thermodynamic modelling, we suggest that these variations could be due to long-term change in the chemical system of the mafic source from which the intermediate to felsic melt and derived zircons are produced. The 2.5 Ga drop was likely associated with an enrichment in incompatible elements in the mafic source, which extended the pressure-temperature field of plagioclase stability as a cogenetic melt phase. We interpret the 0.9 Ga rise to record increasing hydration of magmagenetic sites due to the general development of cold subduction systems, which would delay and/or suppress the saturation of plagioclase in hydrous magmagenetic sites.

How to cite: Triantafyllou, A., Ducea, M., Jepson, G., Bisch, A., and Ganne, J.: Statistical analysis of Europium anomalies in detrital zircons record major transitions in Earth geodynamics at 2.5 Ga and 0.9 Ga, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1954, https://doi.org/10.5194/egusphere-egu23-1954, 2023.

In situ analysis of the Rb–Sr isotopic composition of biotite via triple quadropole LA–ICPMS is an increasingly popular method for constraining the time through the Sr closure temperature in rocks. Although interpreting the radiogenic product can be complicated by various factors that can affect diffusion of Rb and Sr, the role of the different minerals that may be in contact with biotite in regard to local diffusion gradients is poorly understood. In this study, we show the importance of analysing Rb–Sr isotopic data in the context of detailed petrographic observations, which reveals that the ratios obtained are affected by various diffusion pathways between like material and minerals that preferentially incorporate Sr. The studied samples are metapelites from the Fraser Zone (Western Australia) that have peak metamorphic conditions of about 850 °C and 9 kbar and a history of cryptic biotite Ar-Ar ages of ~1205 Ma, which on face value could imply exhumation rates that are some of the fastest recorded in Earth’s history. However, new biotite data from in-situ Rb-Sr analysis highlights differences in Sr retentivity. While calculated isochrons may at first yield large errors, sorting based on the location of the grains in terms of surrounding minerals yields a possible solution for varying Sr values skewing the ages in the sample. This results in an average age of 1205 Ma for biotite and sillimanite surrounded grains and 1107 Ma, from biotite and sillimanite surrounded grains and quartz and K-feldspar surrounded grains. This shows that the diffusive properties of Sr between biotite and the surrounding minerals creating variable re-equilibration between the different domains surrounding biotite. The complexities of Sr diffusion within between the various phases are still unknown, but the apparent effect between the surrounding material on the biotite and the measured initial Sr values does play a key factor in the final calculated ages and the interpretations they represent.

How to cite: Rohrer, R., Clark, C., Kirkland, C., and Johnson, T.: Multiple dates in millimetres; diffusion as an explanation for Rb-Sr age discrepancies in biotite, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2154, https://doi.org/10.5194/egusphere-egu23-2154, 2023.

The Austroalpine nappes in the Eastern European Alps have preserved the record of two orogenic phases in the Cretaceous and Tertiary but their cooling and exhumation history remains poorly constrained. Here we use new low-temperature thermochronological data and thermokinematic modeling to unravel the exhumation history of the Austroalpine nappes in the Nock Mountains east of the Tauern Window (Wölfler et al., submitted). Our data show that the central Nock Mountains (Ötztal-Bundschuh and Drauzug-Gurktal nappes) cooled through the zircon fission track closure temperature (~240 °C) already in the Late Cretaceous. Apatite fission track ages cluster around 35-30 Ma, indicating that the rocks have been at depths of ≤5-6 km since the Eocene-Oligocene boundary. In contrast, the Radenthein and Millstatt Complexes, which are located south of the Hochstuhl Fault, cooled below 240 °C during the Eocene and show apatite fission track ages of ~15 Ma. Thermokinematic modeling of an age-elevation profile in the central Nock Mountains (near Innerkrems) revealed a phase of enhanced exhumation (~0.62 km/Ma) between ~100 and ~85 Ma, which we relate to syn- to late-orogenic Late Cretaceous extension. After a period of slow exhumation (~0.03 km/Ma), the exhumation rate increased to ~0.16 km/Ma at ~32 Ma. In contrast, thermokinematic modeling of an age-elevation profile near Millstatt shows that rocks of the Radenthein and Millstatt Complexes were rapidly exhumed (~0.78 km/Ma) from ~44 Ma to ~38 Ma during the initial Europe-Adria collision. After a phase of slow exhumation (~0.07 km/Ma) between ~38 and ~19 Ma, the exhumation rate increased to ~0.3 km/Ma with the onset of Miocene lateral extrusion in the Eastern Alps. Altogether, ~16 km of rock have been removed since ~100 Ma in the Innerkrems region, whereas ~11 km of rock have been removed in the last ~44 Ma in the Millstatt area. These findings are consistent with pressure-temperature estimates for the Ötztal-Bundschuh nappe and the Radenthein/Millstatt Complexes, respectively (Koroknai et al., 1999; Schuster, 2003; Krenn et al., 2003, 2011). The distinct differences in the cooling histories north and south of the Hochstuhl Fault further suggest that this fault, which has hitherto been considered as a dextral strike-slip fault during Miocene lateral extrusion (Polinski & Eisbacher, 1992; Linzer et al., 2002), also accommodated a considerable amount of thrust movement. The difference between the amount of exhumation north and south of the Hochstuhl Fault indicates ca. 5 km of vertical offset between ~44 and ~38 Ma.

How to cite: Wölfler, A., Hampel, A., Wolff, R., Hetzel, R., and Dunkl, I.: Phases of enhanced exhumation during the Cretaceous and Tertiary orogenies in the Eastern European Alps: new insights from thermochronological data and thermokinematic modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2925, https://doi.org/10.5194/egusphere-egu23-2925, 2023.

In low temperature thermochronology, reliable interpretation of (U-Th)/He data is controlled by our understanding of helium diffusion in a crystal. The diffusion kinetics can be simulated through the classic Arrhenius-type equation, with parameters frequency factor Do and activation energy Ea (Farley, 2000). For apatite, it has been demonstrated that accumulated radiation damage perturbed the Arrhenius-type equation and exerts a strong control on He diffusion. Two models have been developed to parameterise the evolution of diffusion kinetics in apatite in terms of accumulated radiation damage: one based on the physical phenomenon (Gautheron et al., 2009) and the other calibrated on empirical observations (Flowers et al., 2009). As the amount of radiation damage depends on both time (U and Th decay producing damage) and temperature (annealing of radiation damage), both of these models are routinely used to interpret apatite (U-Th)/He data in terms of thermal histories. However, results obtained from inverse thermal history modelling with these two models can differ and be inconsistent with other low thermochronological data (e.g., apatite fission tracks). In this contribution we present a new radiation damage-based diffusion model that combines the approaches of both the Gautheron et al. and Flowers et al. models.

Our new model is based on the theoretical diffusion model proposed by Gerin et al. (2017) but incorporates a new calibration from the available He diffusion experiment results. The Gerin et al. model is built on a theoretical understanding of the fundamental physical processes and predicts diffusion parameters for different levels of crystal lattice damage, using quantum calculus. We recalibrated this model through an empirical law based on real crystal mesh damage calculated from available experimental data. To test the reliability of the revised model and to compare it to the existing models, it was implemented in the modelling software, QTQt (Gallagher, 2012). Here we present results of both forward and inverse modelling to highlight the benefits of the new model. The results are assessed in terms of the impact for “deep time” (>500 Ma) thermochronology, in which accumulated radiation damage can have a significant control on the inferred thermal history models.

Farley, K.A., 2000. Helium diffusion from apatite: General behavior as illustrated by Durango fluorapatite. J. Geophys. Res. 105, 2903–2914. https://doi.org/10.1029/1999JB900348

Flowers, R.M., Ketcham, R.A., Shuster, D.L., Farley, K.A., 2009. Apatite (U–Th)/He thermochronometry using a radiation damage accumulation and annealing model. Geochimica et Cosmochimica Acta 73, 2347–2365. https://doi.org/10.1016/j.gca.2009.01.015

Gallagher, K., 2012. Transdimensional inverse thermal history modeling for quantitative thermochronology. Journal of Geophysical Research: Solid Earth 117, n/a-n/a. https://doi.org/10.1029/2011JB008825

Gautheron, C., Tassan-Got, L., Barbarand, J., Pagel, M., 2009. Effect of alpha-damage annealing on apatite (U–Th)/He thermochronology. Chemical Geology 266, 157–170. https://doi.org/10.1016/j.chemgeo.2009.06.001

Gerin, C., Gautheron, C., Oliviero, E., Bachelet, C., Mbongo Djimbi, D., Seydoux-Guillaume, A.-M., Tassan-Got, L., Sarda, P., Roques, J., Garrido, F., 2017. Influence of vacancy damage on He diffusion in apatite, investigated at atomic to mineralogical scales. Geochimica et Cosmochimica Acta 197, 87–103. https://doi.org/10.1016/j.gca.2016.10.018

How to cite: Derycke, A., Gallagher, K., and Gautheron, C.: A new calibration of radiation damage control on He diffusivity in apatite: implications for (U-Th)/He thermochronology, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3132, https://doi.org/10.5194/egusphere-egu23-3132, 2023.

The Periadriatic Fault System (PAF) is among the largest and most important post-collisional structures of the Alps; it accommodated between 150-300 km of right-lateral strike-slip motion between the European and Adriatic plates from about 35 until 15 Ma. Recent GPS data suggest that Adria-Europe convergence is still being accommodated in the Eastern Alps. However, according to instrumental and historical seismicity records, seismotectonic deformation is mostly concentrated in the adjacent Southern Alps. In this contribution, we present our first results for dating earthquakes along the PAF during the Quaternary by applying two trapped charge dating methods. Both Electron Spin Resonance (ESR) and Optically Stimulated Luminescence (OSL) are especially useful as ultra-low temperature thermochronometers due to their dating range (a few decades to ~1 Ma) and low closing temperature (below 100°C). We aim to show which segments of the PAF system accommodated seismotectonic deformation by directly dating quartz and feldspar from fault gouges. For ESR, we measure the signals from the Al center in quartz following the single aliquot additive (SAAD) and single aliquot regenerative (SAR) protocols, focusing on the 100-150 µm grain size fraction. For OSL, we measure the IRSL signal at 50°C (IR₅₀) and the post-IR IRSL signal at 225°C (pIRIR₂₂₅) on potassium feldspar aliquots of the 100-150 µm grain size fraction. Our ESR results indicate the PAF system accommodated seismotectonic deformation during the last 1 Ma, while the OSL signals for all samples were in saturation. The minimum ages obtained from OSL suggest that the events are likely not younger than 0.4 Ma. We also studied a segment of the nearby Lavanttal Fault, for which our ESR results suggest that the last earthquakes strong enough to produce sufficient shear heating to produce a partial reset on the geochronometer probably happened before 4 Ma.

How to cite: Prince, E., Sumiko, T., Christoph, G., Marko, V., and Kamil, U.: Finding Quaternary Seismogenic Activity Along the Eastern Periadriatic Fault System: Dating of Fault Gouges via Trapped Charge Methods, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3705, https://doi.org/10.5194/egusphere-egu23-3705, 2023.

The Paricutin-Tancítaro region (PTR), located in the SW sector of the Michoacán-Guanajuato monogenetic field, in central Mexico, is characterized by a high spatial density of monogenetic scoria cones around Tancítaro, a stratovolcano active in the middle Pleistocene. The PTR area has been active for around one million years, and the latest eruption, beginning in 1943, formed the Paricutin volcano. We use the Average Erosion Index (AEI) to estimate the relative ages of 170 PTR scoria cones located within latitudes 19°N and 20°N and longitudes -102.0° E and -102.7° E. The AEI quantifies the erosional state of scoria cones from a morphological analysis of their level contours extracted from a high-resolution DEM (the 12-m TanDEM-X in this case). The analysis provides a metric for the undulations along the level contour curves at different altitudes, reflecting the width and amplitude of erosional rills and gullies on the cone’s surface. We compute a functional relationship between AEI and age by correlating 10 published radiometric ages with the measured AEIs of those cones. Then, using that function, we assign an age to each of the 170 cones, assuming that all the monogenetic volcanoes in the analysis have been exposed to similar erosive conditions. Finally, we tessellate the study area with a 0.1° x 0.1° grid and identify the number of events per grid module to compute the probability of at least one eruption occurring in the module in a specific time, using a Poisson process distribution obtained from the count of the number of events per 20 ky time intervals. Our results suggest that the dispersed volcanic activity in the PTR started to increase after the last eruption of Tancitaro (~237 ka), with a further activity increase during the Holocene, mainly concentrated on the NE sector of Tancítaro, where Paricutin is located. Holocene vents align to the NE, parallel to the Tepalcatepec-Tangancícuaro normal fault system. Furthermore, our results suggest a spatial coincidence between the regions with a higher probability of an eruption, based on the obtained eruption history, and the location of the recent seismic swarms in the PTR, the last two in 2020-2021, suggesting an increase in volcanic and seismic hazards in that area. To what extent? It is the subject of our forthcoming research.

How to cite: De la Cruz-Reyna, S.: Temporal and Spatial distribution of scoria cones in the Paricutin-Tancítaro volcanic region, Mexico: A morpho-chronometric approach to monogenetic hazard evaluation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4567, https://doi.org/10.5194/egusphere-egu23-4567, 2023.

⁴⁰Ar/³⁹Ar dating has been a valuable and widely used method for dating orogenic processes such as prograde and retrograde metamorphism and brittle and ductile deformation, through the analysis of K-bearing rock-forming minerals such as white mica. The in situ ⁴⁰Ar/³⁹Ar method, in which a short wavelength laser is used to ablate an analyte and deliver the liberated Ar to a noble gas spectrometer, is particularly valuable as an approach to dating deformation or metamorphism because it allows for targeting of specific chemical and structural domains, and the mapping of intragrain age distributions. Rb-Sr dating can also be applied to K-bearing minerals because of Rb’s propensity to substitute for K. The Rb-Sr method has been under-used in recent decades because the isobaric interference between parent ⁸⁷Rb and daughter ⁸⁷Sr has necessitated the chemical separation of Rb from Sr via ion exchange chromatography prior to mass spectrometric analysis, and hence bulk sampling of the target analyte. New tandem mass spectrometers, in which two quadrupoles are separated by an intervening reaction chamber into which a reactive gas can be introduced, have opened up the opportunity of applying laser-based in situ sampling approaches to beta decay geochronometers, including Rb-Sr (Zack and Hogmalm, 2016).

We have collected new in situ Rb/Sr data for white mica from three different tectono-metamorphic settings previously dated using the in situ ⁴⁰Ar/³⁹Ar method: recrystallization of white mica in a Paleozoic low-temperature ductile shear zone; development of multiple cleavage domains in low-temperature metamorphic rocks deformed in the Paleozoic, and; slow cooling of rocks following regional amphibolite-facies metamorphism in a Paleoproterozoic orogeny. , This allows a direct comparison between these two approaches, with the goal of exploring the functionality and utility of in situ Rb-Sr data, and testing geological interpretations based upon the in situ ⁴⁰Ar/³⁹Ar method. Our results show that the in situ Rb-Sr method is a highly complementary approach to the ⁴⁰Ar/³⁹Ar method for white mica, particularly in cases for which the target mica population has a large internal spread in Rb/Sr. allowing for the rigorous testing of assumptions and hypotheses about timing and conditions of rock cooling, deformation, and fluid events developed using ⁴⁰Ar/³⁹Ar datasets.

Zack, T. and Hogmalm, K.J., 2016. Laser ablation Rb/Sr dating by online chemical separation of Rb and Sr in an oxygen-filled reaction cell. Chemical Geology, 437, pp.120-133.

How to cite: Kellett, D., Larson, K., and Skipton, D.: Integration of in situ Rb-Sr and in situ 40Ar/39Ar dates under diverse tectono-metamorphic scenarios, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5290, https://doi.org/10.5194/egusphere-egu23-5290, 2023.

Step-heating experiments constitute a key technique to study the release of volatile elements from geological materials as a function of temperature. In the case of noble gases (He, Ne, Ar, Kr, and Xe), step-heating is particularly useful to determine diffusion kinetics, structural defects, or spatial homogeneity within the material. These parameters are critical in the application of diffusion-based thermochronology such as the apatite (U-Th)/He system, where mapping out the spatial distribution of natural ⁴He provides crucial information on the thermal history of apatite crystals. Characterizing the diffusion and distribution of ⁴He via step-heating additionally has the potential to detect anomalously behaved grains and to directly constrain grain-to-grain variability in diffusivities within samples with significant radiation damage-induced age dispersion.

Within the ERC-funded COOLER project, we aim to further the development of high-resolution, ultra-low temperature ⁴He/³He thermochronology. To this end, we developed a new technique for precise step-heating experiments coupled with a diode laser including an inline single-wavelength pyrometer. The new protocol uses an all-alumina ceramic crucible fitted with a K-thermocouple ~0.1 mm below the center of the crucible pit. The head of the thermocouple is located directly below the sample within the ceramic matrix, allowing precise temperature measurements of the sample. The crucible is mounted on an alumina rod connected to a noble-gas preparation line. Gas released from the sample is purified and analyzed by a Thermo Scientific Helix SFT™ multi-collector mass spectrometer. The sample is wrapped in Pt foil and indirectly illuminated with a diode laser. Laser and PID temperature controls are carried out by a custom LabVIEW program. Temperature calibration is performed by comparing measured and theoretical melting points of well-known materials loaded in the alumina crucible pit.

Our initial results show very short response times for the thermocouple (a few seconds) and excellent agreement with the melting point of Indium (T_melt = 157°C). Although the current design is limited to hold only a single sample, it enables precise calibration of the emissivity value for a specific capsule assembly, which is a key parameter for pyrometer control of the temperature. Consequently, by calibrating the Pt capsule emissivity prior to the step-heating experiment, they can then be mounted in a multiple laser sample holder (up to 36 samples per chamber). The single-wavelength pyrometer of our system enables temperature measurements for large sample batches. Temperature is also cross-calibrated between the pyrometer and the thermocouple to ensure its correct reading.  This new 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., Bernard, M., and Wapenhans, I.: New high-resolution step heating experiments using a coupled Diode laser and thermocouple for thermochronology applications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6766, https://doi.org/10.5194/egusphere-egu23-6766, 2023.

Movement of a large volume of granitic melt is an important factor in the compositional differentiation of the continental crust and the presence of melt in rocks profoundly influences their rheology. Different mechanisms controlling melt migration through crust were proposed. We suggest that pervasive melt flow, analogous to reactive porous melt flow in mantle, could be possibly one of them. It is generally accepted that migration of felsic melts in continental crust starts with short distance pervasive microscopic flow into segregation veins which extract melt. However, we show that pervasive melt flow may be a regional mode of melt migration in continental crust. In such scenario, melt driven by deformation passes pervasively along grain boundaries through the whole rock volume. And the term pervasive melt flow is used for grain-scale, diffuse, porous and reactive flow of felsic silicate melt through rocks. This is effectively an open-system process that thoroughly reworks the resident rock mass. Through-flow of melt destroys pre-existing fabrics and the original chemical and isotopic nature of the protolith. Melt segregation is inefficient and protolith become isotropic granite-like, with partly preserved relics of the original, without ever containing more than a few melt percent at any time. The fabric and geochemical nature of these granites encapsulates the complex history of hybridization.

In order to decipher duration of pervasive melt migration we used precise U-Pb monazite ID-TIMS (isotope dilution thermal ionization mass spectrometry) and U-Pb monazite Laser Ablation Split Stream (LASS) geochronology in combination with monazite chemistry as well as U-Pb zircon SHRIMP geochronology. Monazite reveal continuous chemical equilibration with passing melt. They are getting progressively enriched in HREE and depleted in Eu. Monazites in the least affected rock preserve original magmatic zoning in Th and U, in contrast to more with melt equilibrated rock types, where this zoning is lost. Data for each migmatite type reveal  similar date spread for both cores and the Y-rich well defined rims of single monazite grains, indicating a disconnect between U-Pb dates and chemical zoning. There is also no correlation between U-Pb ages and Yb/Gd ratio. This suggest perturbance of the isotopic system. We interpret these random distribution within-grain date variations as a result of dissolution-reprecipitation reactions between monazite grains and melt. During the coupled dissolution-reprecipitation radiogenic Pb was redistributed within the grain. This is supported by dissolution of apatite into silicate melts that stabilizes monazite during migmatitization, preventing their dissolution but not reaction with passing melt. Redistribution of radiogenic Pb resulted in meaningless individual ages from different migmatite types, but gave overall duration of the thermal event – pervasive melt flow. Duration of pervasive melt flow was dated 8-10myr. This suggest that porous flow of silicate melts in continental crust is a process which can operate over a long time and impacts on the rheology of the crust during orogeny.

How to cite: Hasalová, P., Schulmann, K., Schaltegger, U., Štípská, P., Kylander-Clark, A., Holder, R., Weinberg, R., and Maierová, P.: Timescale of pervasive melt migration in the continental crust, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6959, https://doi.org/10.5194/egusphere-egu23-6959, 2023.

Pseudotachylytes are solidified frictional melts produced by seismic fault slip. Being melts that solidified in seconds or minutes after the seismic slip event, they have always been considered a very favourable tool to date brittle deformation. However, since all pseudotachylytes are composed of inherited clasts, melt-derived matrix and (quite often) also alteration products, it is necessary to discriminate the Ar contribution of these three reservoirs to obtain meaningful ages. This can be done by analyzing Ca/K and Cl/K signatures provided by Ar systematics. Furthermore, microstructural analysis and microCT allow quantifying the clast-to-pseudotachylyte matrix ratios for each sample, and XRPD allows detecting potential alteration phases. Here we present the results of step-heating ⁴⁰Ar/³⁹Ar analyses performed on pseudotachylytes of the Trois Villes Fault and the Quart Fault, which crop out in a region of the Western Alps (Aosta Valley) affected by three different post-metamorphic brittle deformation phases: D1 characterized by NW-SW extension, D2 with NE-SW extension, and D3 showing N-S extension. The relative chronology of these deformation phases is based on consistent cross-cutting relationships. D1 ages of 29–32 Ma have been inferred from syn-kinematic magmatic dikes and hydrothermal veins. However, no absolute ages were so far available for D2 and D3, as direct radiometric dating of fault rocks has never been performed before in the area. Our results are consistent with the relative chronology and greatly improve our understanding of the tectonics of this area.

How to cite: Lugoboni, Z. G., Arienti, G., Barberini, V., Bistacchi, A., Cannella, C., Caprarulo, S., and Villa, I. M.: 40Ar/39Ar dating of pseudotachylytes: a case study on post-metamorphic brittle fault in the NW Alps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7367, https://doi.org/10.5194/egusphere-egu23-7367, 2023.

Tin-tungsten magmatic-hydrothermal deposits are sources of critical raw materials (Sn, W, Nb, Ta, Li), key to the development of technologies involved in the green transition. However, the current and projected supply of many of these mineral commodities is often dominated by entities whose practices or geopolitical setting may raise issues from a social, political, or environmental standpoint. To meet a steadily increasing demand, new responsible mineral extraction projects must therefore be developed. Successful exploration and economic appraisal of newly identified mineral deposits require (1) an understanding of the ore-forming processes to build an exploration model, and (2) an early estimate of the deposit size to facilitate well-targeted investments. One key parameter that helps to achieve both goals is the knowledge of absolute timing and duration of the mineralisation process.

We present new analytical developments in U-Pb dating of strategic Sn-W ore minerals (cassiterite, wolframite, scheelite) using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). We used a suite of Sn-W mineral specimens to characterise U/Pb downhole fractionation behaviour and polyatomic interference patterns for these three matrices, allowing the optimisation of ablation and ICP-MS settings. In parallel with technical developments, we compiled a large library of potential primary and secondary cassiterite, wolframite, and scheelite reference materials (RMs) which we characterised for major and trace elements. To further our understanding of geochemistry of Sn-W phases, we also performed high-resolution compositional mapping of key trace elements (e.g. U, Pb, REE) with an ultra-fast washout laser ablation system.

Promising RM candidates will be developed into primary RMs with a careful characterisation of compositional homogeneity and precise age determination by isotope dilution-thermal ionisation mass spectrometry (ID-TIMS). Thus characterised RMs and a set of analytical best practices will be made available to laboratories wishing to test and further develop such methods. The ultimate goal of this effort is to build a set of community shared materials and techniques that will allow precise and accurate temporal characterisation of Sn-W mineralisation.

How to cite: Szymanowski, D., Tavazzani, L., Buret, Y., Guillong, M., Cortes Calderon, A., and Chelle-Michou, C.: Developing techniques and reference materials for LA-ICP-MS U-Pb geochronology of Sn-W minerals, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7959, https://doi.org/10.5194/egusphere-egu23-7959, 2023.

The affiliation of the Ennstal Phyllite Zone (EPZ) to either the micaschist units of the Koralpe-Wölz nappe system (KW-NS) to its south or to nappes of the “Greywacke Zone” to its north and east is still debated. Due to similarities with phyllites of the “Greywacke Zone” in the north and phyllonitic micaschists in the south, no clear lithological boundary between these units is observable. Petrographic observations suggest a continuous eoalpine metamorphic gradient with no metamorphic gap between the KW-NS and the EPZ. In order to clear this debate and further constrain the tectonic and temporal evolution of these units, we present new LA-MC-ICP-MS U/Pb age dating results for metapelite samples from the EPZ as well as for the adjacent units of the KW-NS.

Two samples (EA09 and SP02) from the central EPZ and one sample (SP62) from the northernmost part of the Wölz-Complex of the KW-NS were selected for detrital zircon age dating. The distribution of approximately 150 dates per sample reveals major peaks at the Ediacaran-Cryogenian boundary (624 – 646 Ma), a smaller peak at the Neoproterozoic-Mesoproterozoic boundary (~1000 Ma) followed by a hiatus and a smaller peak in the mid-Paleoproterozoic (~2000 Ma). All samples show similar mid-Paleoproterozoic and Neoproterozoic-Mesoproterozoic peaks. Sample SP62 contains one grain of Cambrian age (523 Ma) and one grain of mid-Ordovician age (460 Ma) whereas the youngest zircons from the EPZ samples yield Ediacaran ages of 629 Ma and 625 Ma. The lack of zircons of Ordovician age in samples EA09 and SP02 indicate an affiliation of the EPZ with the basal units of the “Greywacke Zone”.

We also dated metamorphic allanite and REE-bearing epidote rims which are interpreted to form at low pressure and temperature conditions in metapelites. Allanites from the EPZ yield metamorphic ages of 105 ± 3.5 Ma in the northern part of the unit and 279 ± 6 Ma in the southern part. Allanite cores from two micaschist samples from the northern and central Wölz-Complex yield ages of 316 ± 21 Ma and 286 ± 11 Ma. Their respective epidote rims yield eoalpine ages of 98 ± 2 Ma and 96 ± 2 Ma. One micaschist sample from the Rappold-Complex yields ages of 326 ± 9 Ma for the allanite cores and 101 ± 1 Ma for the epidote rims. These ages are interpreted as prograde crystallization of allanite and epidote and give us petrochronological information about three distinct metamorphic events: Variscan, Permian and Eoalpine. By gathering three distinct eoalpine ages within the EPZ and the KW-NS, we can further constrain the metamorphic evolution of the eoalpine lower plate.

How to cite: Stumpf, S., Skrzypek, E., Stüwe, K., and Iglseder, C.: From sedimentation to multiple tectono-thermal events: U/Pb zircon and allanite dating in the Eastern Alps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8495, https://doi.org/10.5194/egusphere-egu23-8495, 2023.

Interpreting cooling ages from multiple thermochronometric systems and/or from steep elevation transects with the help of a thermal model can provide unique insights into the spatial and temporal patterns of rock exhumation. Several well-established thermal models allow for a detailed exploration of how cooling or exhumation rates evolved in a limited area or along a transect. However, integrating large, regional datasets in such models remains challenging due to the difficulty of extracting exhumation rates from ages that are affected by variable effective cooling temperatures, sampling elevations, and surface temperatures. Here we present a thermal model that can be used to rapidly provide a synoptic overview of exhumation rates from thermochronologic data spread over wide regions. The model incorporates surface temperature based on a defined lapse rate and sample elevation relative to a mean relief value that is dependent on the thermochronometric system of interest. Other inputs include sample age, thermochronometric system, and an initial (unperturbed) geothermal gradient. The model is simplified in that it assumes steady, vertical rock-uplift when calculating exhumation rates. For this reason, it does not replace more powerful and versatile thermal-kinematic models like PECUBE, but it has the advantage of simple implementation and rapidly calculated results. In our example dataset, we show the results of exhumation rates calculated from 1785 thermochronologic ages from the Himalaya associated with five different thermochronometric systems; results were calculated in under a second on a standard laptop. Despite the synoptic nature of the results, we show how they illustrate several fundamental features of the mountain belt, including strong regional differences that reflect known segmentation patterns and changing exhumation rates in areas of newly developed ramp structures. The results can also be correlated with geomorphic metrics to probe potential controls on surface morphology.

How to cite: van der Beek, P. and Schildgen, T.: Age2exhume: A Matlab/Python script to calculate steady-state vertical exhumation rates from thermochronologic ages in regional datasets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8741, https://doi.org/10.5194/egusphere-egu23-8741, 2023.

Allanite-group minerals are known to incorporate not only U and Th but also initial, non-radiogenic Pb. Allanite can therefore be analyzed in order to assess its crystallization age as well as the ambient Pb composition at the time of crystallization. Whereas allanite age dating has been the focus of many studies, constraining its initial Pb composition has received much less attention. We collected a series of Phanerozoic, allanite-bearing magmatic rock samples (volcanic, plutonic, pegmatite) and measured both the age and initial Pb composition of allanite by laser ablation-multi collector-inductively coupled plasma-mass spectrometry. We show that allanite data can be corrected for mass bias and fractionation using zircon (for U/Pb and Th/Pb ratios) and glass (for Pb/Pb ratios) as reference material as long as allanite is not metamict. A lower intercept age and y-axis intercept Pb composition can be determined by linearly regressing U-Pb data in a Tera-Wasserburg diagram, and a ²³⁰Th disequilibrium correction is highly recommended. We find a good agreement between our allanite U-Pb dates and published U-Pb zircon ages for the same localities. Our initial Pb compositions are validated by a fair agreement with Pb isotopic data measured on co-genetic feldspars from the same samples. The initial Pb composition of samples ranging from ca. 530 to 18 Ma reveals fluctuations in initial ²⁰⁷Pb/²⁰⁶Pb ratio, which points to different degrees of crustal (elevated μ=²³⁸U/²⁰⁴Pb) contribution. These variations could be due to post-magmatic deformation, weathering or metamorphism, but we believe that they rather reflect differences in initial magma composition. We thus emphasize the usefulness of allanite initial Pb compositions to discuss the source of igneous rocks.

How to cite: Skrzypek, E., Gallhofer, D., Hauzenberger, C., and Haas, I.: How useful is the initial Pb composition of magmatic allanite ?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8976, https://doi.org/10.5194/egusphere-egu23-8976, 2023.

In this work we have been investigating the luminescence properties of plant opal phytoliths to assess their suitability for determination of age and/or thermometric information from soil and sediment sequences. Opal phytoliths, or bio-opal, form when monosilicic acid from soil-waters is taken up by plants and chemically altered to silica, producing intra- or extra- cellular structures that give grasses and stems their strength. Opal phytoliths are usually considered to be non-crystalline and referred to as silica mineraloid structures, with ~4-9% water, <5% other elements, and specific gravity ranging from ~1.5-2.3. They are known to be resistant to degradation and hence preserved in soil or sediment even after decomposition of organic matter. Our earlier work examined a <2.37 g/cm³ density fraction in parallel with quartz grains from samples collected from fluvial terraces and soil pits on Konza Prairie Biological Station native tall grass prairie a few km from Kansas State University. We observed generally similar luminescence characteristics from the phytolith fractions to quartz, with bright blue optically stimulated luminescence (OSL) signals and good single-aliquot regenerative-dose characteristics. In two hours the OSL signal is ~90% bleached by white light, whereas red fluorescence lab lighting has a negligible effect over the same exposure time. Thermoluminescence (TL) data suggested the presence of feldspatic-like minerals or perhaps thermal degradation of the phytoliths during TL measurement; the phytolith fractions were also stimulated by low-temperature infrared stimulated luminescence (IRSL₅₀) perhaps also indicating presence of contaminant minerals. Initial SEM analyses identify what appear to be weathered silica grains, but also highly weathered, pitted concretions with silicate-like structures according to element mapping but actual mineral identification is presently unclear.

Most recently we have begun analyzing samples collected from a suite of stratified paleosols from the mid-continent stream type-site of Claussen, Mill Creek, Wabaunsee County, Kansas. This site has documented phytolith examples and a radiocarbon framework. We are continuing luminescence characterization studies, incorporating screening of prepared fractions with SEM and IRSL₅₀ evaluation, and pulsed time domain analysis measurements are being explored.

We think luminescence from opal phytoliths shows great promise as an alternative target to quartz or feldspar, but moreover as a sensitive recorder of climatic change or fire exposure on plant communities. This presentation will review our earlier work on phytoliths and discuss most recent findings from the Claussen site.

How to cite: Spencer, J. and Sanderson, D.: Luminescence chronology and thermometry studies of plant opal phytoliths, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9864, https://doi.org/10.5194/egusphere-egu23-9864, 2023.

This study tests the application of combined detrital apatite fission track (AFT) and U-Pb dating to infer both glacial erosion spatial patterns and long-term rock cooling histories in Alpine mountainous settings. We have dated 716 detrital apatite grains from glacial sediments collected in the Maurienne and Arve valleys (Western European Alps, France) from moraine deposits corresponding to different stages of glacial retreat since the Last Glacial Maximum (LGM, ca. 24-21 ka).
The Maurienne valley crosses the internal and external Alps, which exhibit contrasting in-situ AFT and U-Pb ages. Here, we present the measured distribution of both detrital AFT and U-Pb ages at 6 locations along the valley, with catchment elevations ranging from 390 to 1740 m. We show that during glacial retreat, erosion is mainly concentrated in the downstream part of the glacier, near the sampled moraine deposits. This inference suggests that during glacial retreat, glacial erosion is more effective below the ELA (Equilibrium Line Altitude) and specifically close to the glacier front, in areas where ice flow velocity is high and subglacial water is abundant, as predicted by ice-dynamics reconstructions in the European Alps over the last 20 ka.
In the Arve valley, previous studies showed that in situ AFT ages are systematically younger than 7 Ma for the Mont-Blanc massif. We compare the thermal history obtained from these literature bedrock-derived data to that derived from the new detrital AFT data collected in the Little Ice Age (LIA) moraine, just at the front of the Bossons glacier (~1300 m elevation). We also compare our results with 5 other samples down the valley at catchment elevations between 460 and 1050 m to evaluate potential changes in the detrital AFT signal as well as the consistency in the retrieved long-term cooling history.
Based on these first results, we plan to extend our study to other areas (e.g., Patagonia) to investigate both (1) spatial patterns of glacial erosion for older glacial periods (pre-LGM), and (2) long-term rock cooling histories from moraine deposits where modern bedrock is inaccessible (e.g. under modern glaciers or ice fields).

How to cite: Guillaume, B., Cogné, N., Gallagher, K., Valla, P. G., and Crouzet, C.: Using detrital thermochronology on moraine deposits to infer glacial erosion patterns and rock thermal history : insights from the Arve and Maurienne valleys (Western European Alps), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11638, https://doi.org/10.5194/egusphere-egu23-11638, 2023.

How to cite: Whipp, D. M. and Kellett, D. A.: Exploring the relationships between low-temperature thermochronometers, temperature-time histories, and geological processes using Tc1D, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12472, https://doi.org/10.5194/egusphere-egu23-12472, 2023.

Applications of tracer thermochronology exploit a known or assumed surface thermochronometric age map (based on either interpolated observed or modelled bedrock ages) to determine the provenance of detrital grains within fluvial or glacial catchments. The goal is to interpret the erosion pattern and processes within the sampled catchment. So far, most studies focused on modern sediments and glacial deposits.

We extend this approach to several time slices (between 28 and 12 Ma) of well-dated stratigraphic sections of pro- and retro-foreland basins of the European Alps. Foreland basin deposits represent a rich archive of erosional processes that were controlled by tectonics, climate, and lithology. However, importantly, before we reconstruct and interpret past erosion patterns and exhumation from detrital zircon fission-track (ZFT) age distributions and modelled bedrock ZFT ages back in time, we produce a frame of reference of today's situation. We do this by investigating signals from modern river samples and the present-day erosion pattern and mineral fertility in the Alps.

Here, we focus on 26 modern river samples (21 previous samples from the Western and Central Alps, and 5 new samples from the Eastern Alps) and discuss observed and predicted (based on possible erosion scenarios) ZFT age distributions, as well as potential pitfalls of the method (such as poor bedrock control in some areas of the Alps). We also show preliminary results from stratigraphic sections.

How to cite: Glotzbach, C. and Falkowski, S.: Erosion patterns in the European Alps from zircon fission-track tracer thermochronology, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12637, https://doi.org/10.5194/egusphere-egu23-12637, 2023.

Zircon megacrysts are unusually large crystals (> 5 mm) that are commonly associated with mantle-derived kimberlites, carbonatites, alkali basalts and syenitic pegmatites (e.g., Hoskin and Schaltegger 2003). Such zircons form during relatively short timespans and therefore, are often used as reference material for U-Pb geochronology. Here, we determine the geochemical and isotopic (U-Pb, Hf, O) characteristics of a little-known occurrence of zircon megacrysts at Kawisigamuwa, Sri Lanka.

The dark brown megacrysts are euhedral, commonly elongate crystals with double pyramidal terminations and have faintly corroded crystal surfaces. The zircons consist of oscillatory zoned and nearly featureless cathodoluminescence-bright patches, some of which appear to follow sealed cracks. All zircon domains show a low to moderate FWHM of the ν₃ (SiO₄) Raman band (2.5 to 7.3 cm^-1), have a low to moderate radiation damage (total α-dose mainly <0.5 x 10¹⁸ events/g) and therefore are intermediate to well crystalline. Contents of most trace element (U, Th, REE, P) are elevated in the oscillatory zoned domains, while Hf content is elevated in the CL-bright domains and seems to be grain-dependant. The oscillatory zoned domains yielded a TIMS weighted mean ²⁰⁶Pb/²³⁸U age of 532.39 ± 0.66 Ma (2sd). The²⁰⁶Pb/²³⁸U dates within the CL-bright domains are partially reset by a single event of recrystallisation at ~518 Ma. The mean Hafnium isotopic compositions of the tested grains show a narrow range of ¹⁷⁶Hf/¹⁷⁷Hf from 0.281969 to 0.282003. Oxygen isotopes determined on two oscillatory zoned zircon megacrysts are homogeneous (mean δ¹⁸O of 12.1 and 12.2).    

While some of the trace and major element characteristics (Th/U, Zr/Hf, Hf content) of the Kawisigamuwa megacrysts resemble those of carbonatite zircons, their hafnium and oxygen isotope ratios are clearly different from mantle values. The isotopic values indicate that a significant amount of a crustal component must be involved in the formation of the zircons. Recently, several studies have found evidence for melting of carbonate rocks under high grade metamorphic conditions in Sri Lanka (e.g., Wang et al. 2021). It might be feasible that zircons grow from interaction of crustal derived carbonate melts and silicate melts or wall rocks under high grade metamorphic conditions.

Hoskin P.W.O. and Schaltegger U. (2003). The Composition of Zircon and Igneous and Metamorphic Petrogenesis. Reviews in Mineralogy and Geochemistry, 53 (1), 27–62.

Wang J., Su B.-X., Chen C., Ferrero S., Malaviarachchi S.P.K., Sakyi P.A., Yang Y.-H. and Dharmapriya P.L. (2021). Crustal derivation of the ca. 475-Ma Eppawala carbonatites in Sri Lanka. Journal of Petrology, 62 (11), 1-18.

How to cite: Gallhofer, D., Skrzypek, E., Hauzenberger, C., Möller, A., Andrew, J., Parra-Avila, L. A., Martin, L., Kemp, A., Fernando, R., and Dengfeng, H.: Characterization of zircon megacrysts from an atypical occurrence of carbonatite at Kawisigamuwa, Sri Lanka, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12969, https://doi.org/10.5194/egusphere-egu23-12969, 2023.

Porphyry Copper Systems (PCS) represent a significant source of metals, and will continue to play a key role in future with the development of green technology. Despite being one the most studied mineral systems, the primary controls on the ore tonnage of deposits (that varies up to 5 orders of magnitude in nature) remain poorly constrained. The Eocene Chuquicamata Intrusive Complex (CIC) in northern Chile hosts one of the world’s largest porphyry copper deposits and represent a perfect natural laboratory to explore the influence of timescales in controlling the formation and size of PCS.

Here we investigate the tempo of multiple magmatic-hydrothermal events in the CIC applying molybdenite geochronology (Re-Os ID-NTIMS) and high precision zircon petrochronology (U-Pb CA-ID-TIMS geochronology in tandem with LA-ICPMS trace element composition). Preliminary geochronological results may suggest a partial decoupling of the magmatic and hydrothermal events. Zircon U-Pb geochronology results point to a multi-million-year protracted magmatic history with at least two discrete pulses separated by 500 kyrs. The hydrothermal event appears slightly younger than the youngest magmatic pulse and lasted for ca. 1 Myrs.

The extensive duration of the mineralization scales with the behemothian size of the Chuquicamata deposit (more than 110 Mt of contained copper) and corresponds to predictions from numerical modelling of magma degassing. Interestingly, the apparent temporal decoupling between magmatism and hydrothermal activity at Chuquicamata suggests that syn-mineralization ore-forming magmas might not always intrude as dyke or stock at mineralization depth and can remain hidden at upper to mid-crustal depth. In the absence of high-precision geochronological data, this may bear consequences when assuming a direct genetic link between spatially associated porphyritic rocks and the mineralization.

How to cite: Virmond, A., Selby, D., Wotzlaw, J.-F., and Chelle-Michou, C.: Partially decoupled magmatic and hydrothermal events in porphyry copper systems?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13440, https://doi.org/10.5194/egusphere-egu23-13440, 2023.

Two end-member competing models have been proposed to describe the kinematics of the central Nepal Himalayas in the last few Myr. They differ in their interpretations of which surface breaking faults accommodate current shortening and the kinematics responsible for driving rapid exhumation in the topographic transition zone around the Main Central Thrust (MCT). These locally higher uplift and erosion rates in the High Himalaya could reflect (1) thrusting over a midcrustal ramp with the growth of a Lesser Himalaya duplex at midcrustal depth causing underplating along the Main Himalayan Thrust ramp, or (2) out‐of-sequence thrusting along the front of the High Himalaya, possibly driven by climatically controlled localized exhumation.

To decipher between the two tectonic models, we compare existing low and medium-temperature thermochronometric data (⁴⁰Ar/³⁹Ar on muscovite, apatite (U-Th)/He - AHe, zircon (U-Th)/He - ZHe, apatite fission track - AFT, and zircon fission track - ZFT), extracted from the world thermochronometric data file of Herman et al. (2013), to luminescence thermochronometry data from 61 newly collected rock samples along transhimalayan rivers between the Kali Gandaki and the Trisuli. The luminescence thermochronometry data provide a new perspective on Late Pleistocene exhumation rates (timescales of 10⁴ to 10⁵ years) of the Nepalese Himalayas, by offering quantitative high-resolution constraints of rock cooling histories within the upper kilometres of the Earth’s crust.

All of the thermochronometric data show younger ages and higher exhumation rates around the topographic transition and the MCT zone through central Nepal. For the higher temperature thermochronometers, there is a continuous trend towards younger ages from the Lesser Himalaya through the topographic transition and the MCT zone. These data suggest that the in-sequence model, with exhumation rates linked to increased erosion and the formation of a duplex below the Higher Himalayas, coincident with the MCT location in some areas, is the model that best describes the thermochronometric ages of this study area on Myr timescales. However, the luminescence thermochronometry data reveal a spatial and temporal variability of the higher exhumation rates at different timescales, suggesting an intermittency of exhumation signal due to geomorphological processes. The luminescence thermochronometry data also highlight a systematic sharp transition at the MCT, pointing to out-of-sequence activity at this tectonic boundary on 100-kyr timescales. Whether this difference in tectonic model between the two timescales is due to low resolution of the higher temperature thermochronometers, shallow isotherms deflected by fluid circulation and hot spring activity near the MCT, or to a change in tectonic regime during the last 200 kyr, out-of-sequence activity of the MCT needs to be considered in seismic hazard models as it could put the local population at risk.

How to cite: Bouscary, C., King, G., Lavé, J., Grujic, D., Hetényi, G., Almeida, R., Gajurel, A., and Herman, F.: Out-of-sequence fault activity in the High Himalaya revealed by luminescence thermochronometry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14643, https://doi.org/10.5194/egusphere-egu23-14643, 2023.

Due to the complex geodynamic framework and the excellent state of preservation of the stratigraphic relationships towards the host metamorphic and sedimentary rocks, the Permo-Triassic magmatic sequences of the Southern Alps (Italy) are intensely studied. Throughout the Southalpine domain, the main peaks of the volcano-plutonic activity are both pre- and post-dated by the emplacement of small volume of magmas with variable chemical affinity. These magmas, preserved as dykes and veins intruded into the plutonic bodies and/or the overlying volcanites, are powerful tools for tracing the evolution of the magma source and reconstructing the temporal evolution of the magmatic episode. Here, we present a detailed geochemical and geochronological study of phonolitic dykes (SiO₂ from 56.8 to 57.8 wt.%; Na₂O + K₂O from 11.1 to 15.3 wt.%) cropping out near Predazzo (Southern Alps; Italy) and intruded into the basaltic to trachyandesitic Middle Triassic lavas. The phonolites are mostly aphyric with a porphyricity index <10%. The main mineral phases are concentric-zoned clinopyroxene, ranging in composition from diopside-hedenbergite, to aegirine (Wo_13-51; En_2-29; Fs_20-85), K-feldspar and rare sodalite. Accessory phases are titanite, apatite and magnetite embedded in a aphyric matrix. Titanite has a highly variable U-Th concentration (U from 24 to 478 ppm and Th from 170 to 4328 ppm) and is characterized by a chondrite-normalized REE pattern with a convex-upward shape (La/Yb_N from 18.9 to 41.5) with enrichment in LREE and depletion in HREE. Thermometry through Zr-in-Titanite calculations (Hayden et al., 2008) indicate crystallisation temperatures between 860.3 and 942.8 ± 57 °C. In-situ, U-Pb dating on titanite phenocrysts performed by laser ablation-inductively coupled-mass spectrometry (LA-ICP-MS) shows that the age of phonolite dykes is comprised between 240.4 ± 3.2 Ma and 242.0 ± 3.6 Ma, partially overlapping with the emplacement of the Middle-Triassic plutonic bodies of the Dolomites (238.190 ± 0.050 - 238.075 ± 0.087; Storck et al. 2019).

These results provide new insights into the timing of the Middle Triassic magmatic event in the Southern Alps, fostering the debates about the temporal and chemical evolution of the magmatism in between the Variscan orogeny and the opening of the Alpine Tethys.

References:

Hayden, L. A., Watson, E. B., & Wark, D. A. (2008). A thermobarometer for sphene (titanite). Contributions to Mineralogy and Petrology, 155(4), 529-540.

Storck, J. C., Brack, P., Wotzlaw, J. F., & Ulmer, P. (2019). Timing and evolution of Middle Triassic magmatism in the Southern Alps (northern Italy). Journal of the Geological Society, 176(2), 253-268.

How to cite: Coltorti, M., Nardini, N., Casetta, F., Tavazzani, L., Peres, S., Ntaflos, T., and Dellantonio, E.: In-situ, U-Pb dating of titanite in phonolitic dykes from the Dolomites area (Southern Alps, Italy): new insights on the timing of the Middle Triassic magmatism, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16555, https://doi.org/10.5194/egusphere-egu23-16555, 2023.

Great Holocene civilizations on Pacific islands were created by Homo sapiens. However, most of the construction histories remain uncertain due to the lack of developed writing system and the limitation of dating techniques. Nan Madol (0.7 km in width and 1.5 km in length), an abandoned city called the “Venice of the Pacific” with over 100 artificial islets, is located on the southeastern coast of island Pohnpei in Micronesia. This world-unique ruin, inscribed onto UNESCO’s World Heritage List in 2016, was built with basalt megaliths and scleractinian coral cobbles. Oral histories and previous charcoal ¹⁴C ages suggested that the main construction of Nan Madol of Pohnpei could begin in the 13th or 14th century and ceased at the 16th or 17th century, associated with the rise and fall of the Saudeleur Dynasty. However, after 150 years or more of studies, the timing of construction and the dynasty, and the probable influence of environmental factors, remain unresolved. High-precision U-Th dating techniques, developed at the High-Precision Mass Spectrometry and Environment Change Laboratory (HISPEC), Department of Geosciences, National Taiwan University, were used to date the selected pristine coral infills and reveal the construction time of the two ruins. With over 150 coral ages determined, results show a peak of construction activity during the middle 11th century could be related to the rise of the Saudeleur Dynasty. In the early 15th century, construction activities ceased, associated with the dynasty’s downfall. Our study shows that Nan Madol construction and the rise and fall of the dynasty occurred 2-3 centuries earlier than previously estimated. Moreover, the entire development was dominated by El Niño-Southern Oscillation variability and tectonic-related sea level rise.

How to cite: Shen, C.-C. (., Beardsley, F., Gong, S.-Y., Kataoka, O., Yoneda, M., Yokoyama, Y., Jiang, L., Lin, A. Y.-M., Fox, J., Barnabas, J., Kohler, G., Richards, Z. T., and Hobbs, J.-P. A.: Dating a world-unique Pacific ruin: Nan Madol, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-123, https://doi.org/10.5194/egusphere-egu23-123, 2023.

The application of U-Pb dating method performed on calcite has exponentially increased over the last years, since constraining the age of the crystallization for such syn-kinematic minerals, would provide a specific timing of faults movement. The potential gain of this approach is evident but the robustness of the U-Pb method performed on calcites has been not yet systematically tested.  Here, we firstly demonstrated that a mineral/fluid interaction indeed affects the regression of the ²³⁸U/²⁰⁶Pb and ²⁰⁷Pb/²⁰⁶Pb data-points and therefore the age; and secondly, we propose an innovative application of U-Pb dating method and a new strategy to identify and reject analytically robust isochrons.

We explore 36 samples, combining U-Pb dating performed with different methods along with carbon and oxygen stable isotopes compositions measured on the same fibres of calcite. The extremely high precision ²⁰⁷Pb/²⁰⁶Pb measured by Thermal Ionisation Mass Spectrometry  revealed that every sample experienced a certain degree of fluid interaction. We find no correlation between ²³⁸U/²⁰⁶Pb and the spread in δ¹⁸O. The higher spread in δ¹⁸O is instead coupled with a remarkable scattered data-points that yield U-Pb ages calculated with the different methods on the same samples with a large variability. In conclusion, our study demonstrates that great care must be taken when considering radiometric ages made on calcite since LA-ICP-MS large uncertainties might obscure the isotopic reorganization.

How to cite: Lanari, R., Buzenchi, A., Bragagni, A., Dhuime, B., Brilli, M., Del Ventisette, C., Mattei, M., Conticelli, S., and Avanzinelli, R.: Mineral/Fluid interaction as a potential bias in calcite U-Pb dating, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-265, https://doi.org/10.5194/egusphere-egu23-265, 2023.

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb geochronology of calcite has been an emerging research direction in recent years that has been widely applied to various disciplines, such as dating of brittle deformation, biological biomineralization, oceanic crust alteration, and hydrocarbon migration. The method has the advantage of quickly locating regions of relatively high uranium content and radiogenic lead that avoids the time-consuming procedures traditionally required for isotope dilution methods. Herein, we show how this method is successfully applied to dating of diagenesis and hydrothermal activity in Precambrian-Phanerozoic sedimentary rocks, but with a note of caution that the susceptibility of the calcite U-Pb isotope system to fluid activities means interpretation of calcite U-Pb data and selection of calcite standard should be cautioned. We demonstrate the following case studies: LA-ICP-MS calcite U-Pb geochronology has aided in defining the Mesoproterozoic-Neoproterozoic boundary (ca. 1010 Ma) in North China Craton. It also constrains the timing of calcite infillings in the Ediacaran cap carbonate to be ca. 636 Ma, indicating an early diagenetic origin and thus confirming a methane seepage hypothesis. Two episodes of hydrothermal activity (ca. 290 Ma and ca. 250 Ma) have been recognized from the Cambrian carbonate in the Tarim region, which was induced by the Permian Tarim Large Igneous Province (LIP) and Indosinian orogeny, respectively.

How to cite: Lan, Z., M W Roberts, N., Wu, S., Wang, F., Wang, H., Cao, R., Li, Z., Zhou, Y., Shi, K., and Liu, B.: Application of carbonate U-Pb geochronology in dating of diagenesis and hydrothermal activity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4234, https://doi.org/10.5194/egusphere-egu23-4234, 2023.

The global-scale glacial events recorded by diamictite and cap carbonate couplets occurred in the late Neoproterozoic and has been recognized on at least 15 paleo-continents. Diamictite and cap carbonate couplets play a pivotal role in establishing regional stratigraphic correlations and understanding the extreme climatic conditions and glacial-interglacial cycles of the Neoproterozoic glaciation. Here we report newly discovered Neoproterozoic glaciogenic diamictite and cap carbonate couplet in the Longshoushan area at the southwestern margin of the Alxa Block, NW China. Based on detailed stratigraphic and sedimentologic studies, we identified massive and stratified diamictites at the bottom of the Hanmushan Group, both with poorly sorted and rounded gravels. The presence of glacial striations and ice-rafted dropstones in stratified diamictites supports a glaciogenic origin. The upward transition from massive diamictites to stratified diamictites indicates the process of glacier retreat. The occurrence of thin-bedded phyllites in the stratified diamictites suggests a short-term deglaciation during the glaciation. The 2- to 2.6-m-thick cap carbonates cover the stratified diamictites and consist of thinly laminated microcrystalline dolomites. The basal cap carbonates contain closely linked sheet cracks, cemented breccias, tepee-like structures and cavities. The cap carbonates show high-resolution ¹³C_PDB chemostratigraphy and negative δ¹³C values (ca. −2.9 to −4.1‰), typical of the Marinoan cap carbonates. Regional sedimentary characteristics and the C-O isotope values suggest that the diamictites and cap carbonate couplet in the Alxa Block likely correspond to the Marinoan glaciation and subsequent deglaciation (ca. 635 Ma), not the previously assumed Ediacaran glaciation. Thus, the diamictite and cap carbonate sequence marks the Cryogenian-Ediacaran boundary in the Alxa Block and provides evidence for further stratigraphic correlation and investigation. This work was financially supported by NSFC projects (grants 42072264, 41730213, 41902229, 41972237) and Hong Kong RGC GRF (17307918).

How to cite: Shao, D., Han, Y., Li, M., Lu, L., Cao, X., and Ju, P.: Discovery of Neoproterozoic glaciogenic diamictites and cap carbonate couplet in the Alxa Block, NW China: Evidence from stratigraphic, sedimentologic and geochemical studies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4758, https://doi.org/10.5194/egusphere-egu23-4758, 2023.

There has been considerable debate as to whether the Korean peninsula has evolved as part of the Sino-Korean Craton since Neoarchean or whether it is a product of the amalgamation of several continental fragments in the early Mesozoic Era. The relationship between the Neoproterozoic Okcheon Metamorphic Belt (OMB) and the Early Paleozoic Tabaeksan Basin (TB) in the central region of the Korean Peninsula has the potential to provide an answer to this question. Various carbonate rocks appear in OMB, showing unique carbon isotope values ​​according to their geologic age.

The Hyangsanni Dolomite is distributed around the Gyemyeongsan Formation with metavolcanics of about 860 Ma. The Hyangsanni Dolomite has δ¹³C values between +2.9 ‰ and +6.2 ‰, markedly higher than the Cambro-Ordovician values, and are consistent with the Neoproterozoic values. Considering the low values ​​of 86Sr/87Sr, the deposition period of the Hyangsanni Dolomite is judged to be Tonian before the Sturtian Glaciation.

The Geumgang Limestone has a maximum thickness of several tens of meters adjacent to the diamictite layer proposed as a glacial deposit but shows a very extensible distribution. The δ¹³C values ​​of the Geumgang Limestone range from -12.25 to -7.88 ‰, suggesting that they may be cap carbonates. However, whether their deposition was related to the Sturtian Glaciation or the Marinoan Glaciation is not yet known.

Between the Cryogenian Seochangri Formation of OMB and the Cambrian Jangsan Formation of TB are carbonate rocks previously considered Ordovician. However, carbon and oxygen isotope values analyzed in this study require different interpretations. Zones with δ¹³C values ​​ranging from -3.4 to +1.3 ‰ agree with Ordovician seawater values. However, over a larger area, δ¹³C values ​​show mostly positive values ​​from +1.9 to +7.8 ‰. Also, a significant negative excursion of δ¹³C values ​​down to -6.9 ‰ occurs near the highest values ​​measured. These values correlate with Ediacaran or Early Cambrian carbonates better than Ordovician seawater. It is the first to discover the possible carbonate rocks of Ediacaran or Early Cambrian in South Korea, supporting that the Neoproterozoic OMB and Early Paleozoic TB have a tectonic evolutionary history of continuous deposition rather than an assembly of different continental fragments.

How to cite: Park, K.-H. and Ha, Y.: Carbon Isotopic Composition of Carbonates of the Okcheon Metamorphic Belt in South Korea from Neoproterozoic to Early Cambrian Potential: Geological and Tectonic Significance, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5196, https://doi.org/10.5194/egusphere-egu23-5196, 2023.

U-Pb geochronology of calcite using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is an emerging method, with potential applications to a vast array of geological issues. Accurate LA-ICP-MS calcite U-Pb dating requires matrix-matched RMs for the correction of instrumental mass bias of Pb/U ratios. Several materials are currently being used as RMs, including WC-1, Duff Brown Tank, ASH-15, JT, and AHX-1A. In this study, we will give a brief introduction of LA-ICP-MS lab at IGGCAS for carbonate U-Pb dating. Meanwhile we further characterized two calcite reference materials for micro-beam U-Pb geochronology and and C, O isotope ratio measurements. LA-ICP-MS multiple spot analyses (> 400) at different regions of materials reveal that calcite TLM and LSJ07 are homogeneous for the U-Pb age with 220.72 +/-0.98 Ma and 26.54+/-0.41 Ma respectively. SIMS multiple spot analyses (> 100) reveals calcite TLM is homogeneous for the O isotope ratio at mm special resolution. MAT 253 gives a bulk result of δ¹⁸O =-14.20 ‰. LA-MC-ICP-MS multiple spot analyses (> 200) reveals calcite TLM and LSJ07 are homogeneous for the C and O isotope ratio at mm special resolution. MAT 253 gives bulk results of δ¹³C =-1.53 ‰ andδ¹³C =-0.33 ‰ for TLM and LSJ07 respectively. These two materials represent a useful addition to the currently distributed WC-1, Duff Brown Tank, ASH-15, JT, and AHX-1A for micro-analytical techniques of U-Pb geochronology and C, O isotope ratio measurements.

How to cite: Wu, S., Yang, Y., Romer, R., Roberts, N. M. W., and Lan, Z.: Calcite TLM and LSJ07: two natural reference materials for micro-beam U-Pb geochronology and C, O isotope ratio measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5345, https://doi.org/10.5194/egusphere-egu23-5345, 2023.

Large gas fields are hosted in Upper Permian reef-dolostone bodies in Sichuan Basin, southwest China, among which the Puguang gasfield is the largest marine-carbonate gas system in China. The reservoir rocks are mainly composed of intensively dolomitized sponge-reefs constructed within platform margin reef facies in northern Sichuan Basin. Although major reservoir spaces consist of intercrystal pores, dissolved pores and vugs, the knowledge regarding the evolution of porosities is still limited. Using multiple methods, this study focuses on characterising different phases of carbonates (calcite and dolomite) to understand the dolomitization model and porosity evolution of the Upper Permian Panlongdong reef cropped out in northeastern Sichuan Basin. Two-dimensional high-resolution visualization of element contents in reef dolostones was provided by synchrotron-radiation Micro X-ray fluorescence elemental mapping. O and Sr isotope analysis was carried out to trace the nature of fluids during dolomitization. Laser ablation ICP-MS U-Pb dating was performed on dolomite minerals and secondary calcite cements. Our results suggest that: (1) dolomitization of the reef occurred in the early Middle Triassic (~245 Ma) due to the downward reflux of hypersaline seawater rich in Mg²⁺, accompanied by a significant increase in porosity because of the selective dissolution of low-Mg calcites; (2) in the Late Triassic, continental collision between South and North China plates induced uplifting and formation of a large quantity of (micro)fractures in northern South China, followed by Sr-depleted freshwater passing through the reef, leading to precipitation of secondary calcite cements (~206 Ma).

How to cite: Zheng, B., Zhou, R., Mou, C., Zhao, J., and Howard, D.: Dating and characterizing carbonate rocks in Upper Permian reef-dolostone reservoir systems in Sichuan Basin, southwest China: implications for porosity evolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5865, https://doi.org/10.5194/egusphere-egu23-5865, 2023.

The presence of magnesite (MgCO₃) in the Earth’s mantle plays a fundamental role in reducing the melting point of the mantle [1] and forming carbonate‑rich melts such as kimberlites and carbonatites [2]. The melting curve of (dry) magnesite is well constrained [3, 4], but melting of magnesite in the presence of H₂O, providing the basis for more complex (natural) systems, is poorly understood from some quenched experiments [5]. Also, the distribution of trace elements such as Li, Sr, Pb, and rare earth elements during melting of magnesite is poorly considered in models that evaluate the trace element budget of carbonate‑rich melts parental to kimberlites [6].

Here we report, first, the H₂O‑present melting curve of magnesite between 2 and 12 GPa. The melting curve of magnesite mixed with 16 wt% brucite was established by in ‑ situ X‑ray diffraction measurements using the large volume press at P61B at PETRA III (DESY). Second, we report trace element partitioning data for congruent melting of calcite and incongruent melting of magnesite producing carbonate melt and periclase between 6 and 9 GPa. Those results were obtained from quenched experiments using a rocking multi‑anvil press at the GFZ overcoming equilibrium and quenching problems in previous studies [7].

1          Dasgupta and Hirschmann, The deep carbon cycle and melting in Earth's interior. Earth and Planetary Science Letters, 2010. 298(1-2): p. 1-13.

2          Jones, Genge, and Carmody, Carbonate Melts and Carbonatites. Reviews in Mineralogy and Geochemistry, 2013. 75(1): p. 289-322.

3          Solopova, Dubrovinsky, Spivak, Litvin, and Dubrovinskaia, Melting and decomposition of MgCO3 at pressures up to 84 GPa. Physics and Chemistry of Minerals, 2014. 42(1): p. 73-81.

4          Müller, Koch-Müller, Rhede, Wilke, and Wirth, Melting relations in the system CaCO3-MgCO3 at 6 GPa. American Mineralogist, 2017. 102(12): p. 2440-2449.

5          Ellis and Wyllie, Carbonation, hydration, and melting relations in the system MgO-H2O-CO2 at pressures up to 100 kbar. American Mineralogist, 1979. 64(1-2): p. 32-40.

6          Girnis, Bulatov, Brey, Gerdes, and Höfer, Trace element partitioning between mantle minerals and silico-carbonate melts at 6–12GPa and applications to mantle metasomatism and kimberlite genesis. Lithos, 2013. 160-161: p. 183-200.

7          Buob, Experiments on CaCO3-MgCO3 solid solutions at high pressure and temperature. American Mineralogist, 2006. 91(2-3): p. 435-440.

How to cite: Sieber, M. J., Reichmann, H., Farla, R., Appelt, O., Oelze, M., Lathe, C., and Koch-Müller, M.: H2O-present melting curve of magnesite and trace element distribution during melting of (dry) magnesite and calcite in the upper mantle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7797, https://doi.org/10.5194/egusphere-egu23-7797, 2023.

Isotopic analysis using high resolution Isotope Ratio Laser Spectroscopy (IRLS) has been shown to be advantageous to multiple geochemical applications during the last decade.  These advances include isotopic analysis of the bulk isotopic compositions of water, carbon dioxide, methane and nitrous oxide.  More recently, laser spectroscopy has been used by several groups to examine the isotopic compositions of methane, carbon dioxide and nitrous oxide when carrying two rare isotopes (so called clumped isotopes).   Our recent work using Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS) has demonstrated highly accurate (~0.01 ‰) measurements of the clumped (¹⁶O¹³C¹⁸O or 638 in HITRAN isotope notation) isotopic composition of carbon dioxide derived from carbonate samples with spectroscopic measurement times of ~30 minutes using a dual laser spectrometer.  That spectrometer is optimized for the measurement of the four isotopologues required to calculate Δ₆₃₈ (or Δ₄₇).  We present here our parallel project to develop a novel dual laser isotope analyzer capable of measuring multiple carbon dioxide isotopic signatures simultaneously.   Specifically, we simultaneously measure the isotopic abundances of the three most abundant clumped isotopologues (Δ₆₃₈, Δ₆₃₇ and Δ₈₂₈) as well as ¹⁷O oxygen excess or Δ¹⁷O.  Δ₆₃₈ and Δ₈₂₈ correspond to the quantities Δ₄₇ and Δ₄₈ when measured by isotope ratio mass spectroscopy (IRMS).   Δ¹⁷O is very difficult to measure with IRMS and Δ₆₃₇ has not been previously measured with any technique to the best of our knowledge.  The new instrument utilizes carefully chosen spectral windows, operates at low sample pressure and exploits automated laser frequency hopping.  This prototype instrument simultaneously measures seven isotopologues of carbon dioxide: 626, 636, 628, 627, 638, 637 and 828.  Our preliminary results for Δ₈₂₈ (or Δ₄₈) are displayed as an Allan-Werle plot which shows that the precision in the measurement of Δ₈₂₈ is ~0.09‰ for a single 3 minute sample measurement referenced to a working reference gas.  The plot shows that instrumental drift is very small over periods of several hours and that the precision can be improved to 0.03‰ by processing 10 sub-samples or to 0.01‰ by processing 100 sub-samples.  These measurements are preliminary and somewhat idealized but show promise for this new technique.

How to cite: Nelson, D., Herndon, S., Wang, Z., Quade, J., and Dettman, D.: TILDAS measurement of multiple clumped isotope ratios in carbonates: progress and new horizons, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9499, https://doi.org/10.5194/egusphere-egu23-9499, 2023.

For fundamental thermodynamic reasons, ¹³C-¹⁸O bonds in carbonate minerals formed under isotopic equilibrium conditions are more abundant than predicted for a random distribution of isotopes, yielding positive Δ₄₇ clumped-isotope signatures which decrease as a function of formation temperature [1]. Although most Earth-surface carbonates are unlikely to achieve complete isotopic equilibrium, Δ₄₇ values of many biogenic and abiotic calcites formed under very different crystallization conditions (and with irreconcilable water-calcite oxygen-18 fractionation laws) appear to follow indistinguishable temperature calibrations, as independently documented by various groups over the years [e.g., 2-4]. That is not to say that all groups agree on a single calibration linking Δ₄₇ and temperature, and a recent comparison of 14 reprocessed calibration studies still found evidence for statistically significant inter-laboratory discrepancies [3]. Rigorous statistical tests aiming to prove or disprove consistency between Δ₄₇ calibrations are particularly challenging because of potentially large and non-independent analytical errors associated with standardization procedures [5], and even in some cases by large correlations in the uncertainties of estimated formation temperatures, making classical least-squares regression approaches ill suited to model these calibration data sets.

Here I propose a new formulation for least-squares regression of data with an arbitrarily complex covariance structure linking all predictor and response observations, generally applicable to all sorts of geochemical data. I use this “Omnivariant Generalized Least-Squares” (OGLS) approach to compare 7 published Δ₄₇ calibration data sets which have been (re)processed according to the newly established InterCarb Carbon Dioxide Equilibrium Scale (I-CDES), supposedly allowing robust comparisons between Δ₄₇ measurements across laboratories [6]. None of these reprocessed calibration data sets are found to deviate significantly from a single, unified regression line, with an overall reduced chi-squared statistic (adjusted for data covariance according to OGLS) of 0.8 consistent with slightly overestimated uncertainties on temperature constraints. This finding marks another milestone in the 17-year-long progress of Δ₄₇ thermometry, which has now solved most of the methodological challenges standing in the way of its widespread application to many scientific issues. In short: carbonate clumped-isotope thermometry is all grown up now.

[1] Schauble et al. (2006) 10.1016/j.gca.2006.02.011
[2] Kele et al. (2015) 10.1016/j.gca.2015.06.032
[3] Petersen et al. (2019) 10.1029/2018GC008127
[4] Anderson et al. (2021) 10.1029/2020GL092069
[5] Daëron (2021) 10.1029/2020GC009592
[6] Bernasconi et al. (2021) 10.1029/2020GC009588

How to cite: Daëron, M.: Making the Case for Reconciled Δ47 Calibrations Using Omnivariant Generalized Least-Squares Regression, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10066, https://doi.org/10.5194/egusphere-egu23-10066, 2023.

This study investigates carbonate veins in five drill cores archived at Geological Survey of Queensland from NW Queensland, ~100 km south of Mt Isa, with geochemical and geochronologic approaches in order to characterise origins of fluids and their mineralisation potentials. Carbonate veins are mostly hosted in Proterozoic age (approximately 1800-1650 Ma) supra-crustal rocks, which are inferred from geophysics to be covered by 350 to 2,000 m of younger sedimentary rocks of the Eromanga and Georgina basins. Data regarding the nature of fluid activities is important for comparison between the undercover southern Mt Isa and outcropped Mt Isa mineral district, which is a world-class mineral province.

Multiple-phase carbonate veins (mostly calcite and dolomite) are identified, including late formed brittle veins, pyrite/chalcopyrite mineralisation-bearing carbonate veins, and calcite hosted in crackle breccias. Samples are prepared into one-inch polished mounts and studied with SEM-EDS, and in situ laser ablation ICP-MS for geochemical and U-Pb geochronological studies. Relatively pure calcite phases are also prepared with microdrill for stable isotope C and O analysis. Trace element datasets suggest enrichments in rare earth elements and ytterbium (REE+Y) with distinct negative Eu anomalies. Stable isotopes range ~-5 to – 15 (δ13C_VPDB‰) and ~10 to 25 (δ18O_VSMOW‰). Trace element data, Yb/La and Yb/Ca ratios, and stable isotope signatures imply that these carbonate veins have hydrothermal origins. ²⁰⁶Pb/²³⁸U geochronology data has indicated multi-phase calcite formation ranging from the late Neoproterozoic to Cretaceous. Our results provide a novel dataset to demonstrate the use of carbonate veins in revealing fluid activities in a mineral district and help the future exploration of critical mineral deposits in undercover southern Mt Isa when interpreted against regional structural data and well-documented mineralisation events in the northern Mt Isa district.

How to cite: Chen, X., Zhou, R., Wood, D., Stirling, D., Jhala, K., Friedman, I., Valetich, M., and Philippa, L.: Geochemical and geochronologic investigations into carbonate veins from historical drill cores in undercover Mt Isa, NW Queensland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10706, https://doi.org/10.5194/egusphere-egu23-10706, 2023.

Oxygen-17 excess (Δ17O) in carbonate minerals can provide valuable insights into past continental and marine environments, long-term trends in the temperature and oxygen-isotope composition of ancient oceans, isotopic disequilibrium effects in biogenic and abiotic carbonates, and cryptic diagenesis. Triple oxygen isotope analyses of carbonates and/or CO2 using isotope-ratio mass spectrometers (IRMS) remain challenging, however, because of isobaric interference between 16O13C16O and 16O12C17O. Using spectroscopic methods, the abundance of each CO2 isotopologue may be directly quantified, potentially providing simple, non-destructive measurements of δ13C, δ18O and Δ17O on small samples of CO2.

Here we report new data characterizing the application of VCOF-CRDS (V-shaped Cavity Optical Feedback - Cavity Ring Down Spectroscopy [1]) to the analysis of small samples (<40 μmol) of pure CO2, as typically produced by phosphoric acid digestion of carbonate minerals.

Instrumental drifts from various sources are observed to bias apparent isotopic abundances by a few tens of ppm, but these drifts are slow enough that they may be precisely monitored and corrected for by repeated analyses of a working gas interspersed between other analyses, requiring only ~8 mn per aliquot and 30 mn between consecutive “unkown” analyses. This approach was tested by analyzing repeated aliquots of another CO2 tank with a different isotopic composition, yielding instrumental repeatabilities of 12 ppm, 13 ppm and 7.4 ppm for δ13C, δ18O and Δ17O, respectively (95 % CL, Nf = 66).

The accuracy of our measurements was tested over a wide range of Δ17O values spanning 130 ppm, by analyzing CO2 equilibrated at 25 °C with different waters whose triple oxygen compositions were independently constrained in the SMOW-SLAP scale by IRMS measurements and by simple nonlinear mixing predictions. We find that our Δ17O measurements are well within analytical uncertainties of predicted values (RMSE = 1.2 ppm), with analytical repeatabilities (including isotopic equilibration and gas manipulation) of 8.6 ppm (95 % CL, Nf = 27).

We will also report the results of our ongoing investigation regarding the isotopic fractionation and analytical noise associated with different acid digestion protocols at different reaction temperatures, and the triple oxygen composition of various international reference materials already used for δ13C, δ18O, and clumped-isotope measurements.

Based on these results, we conclude that VCOF-CRDS offers excellent accuracy, along with state-of-the-art levels of analytical precision/linearity, for straightforward analyses of 17O excess in CO2, water, and carbonate minerals.

[1] Stoltmann et al. (2017) 10.1021/acs.analchem.7b02853

How to cite: Chaillot, J., Daeron, M., Casado, M., Landais, A., Pesnin, M., and Kassi, S.: Triple oxygen isotope analyses of carbon dioxide, water and carbonates by VCOF-CRDS technique, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12216, https://doi.org/10.5194/egusphere-egu23-12216, 2023.

The final stage of the Proterozoic, the Ediacaran, shields fascinating insights on the development and dispersal of complex metazoans related to dramatic compositional changes in the atmosphere and hydrosphere.  Alternating sequences of siliciclastic and carbonate rocks of the Namibian Nama basin record the final stage of the Ediacaran and contain a vast amount of soft-bodied fauna, as well as some of the first biocalcifying organisms. However, the sparsity of ash beds at the base of the Nama group, preclude accurate and precise constraints on the onset of the Ediacaran biota in Nama group and correlation with chemo stratigraphic records worldwide.  

Due to the scarcity of ash layers, we apply U-Pb dating to carbonate rocks especially from the lower stratigraphic sections of the Nama Group combining the spatial resolution of LA-ICP-MS and the high-precision ID-TIMS U-Pb dating. The combination with mineralogical and geochemical techniques (d¹³C, d¹⁸O, XRD, SEM, EPMA, CL imaging, LA trace element transects, Raman spectroscopy, clumped isotope thermometry, QEMSCAN, SIMS) enables us to better understand the nature of the analyzed carbonates to distinguish between more pristine and diagenetic phases.

This study elaborates on the potential and limitations of carbonate U-Pb dating for improved stratigraphic correlation on these ancient pre-Cambrian marine carbonates from the Nama Group.

How to cite: Müller, I. A., Messori, F., Guillong, M., Peyrotti, G., Schirra, M., Samankassou, E., Linnemann, U., Hofmann, M., Zieger, J., Martignier, A., Bouvier, A.-S., Venneman, T., Kouzmanov, K., and Ovtcharova, M.: The onset of the Ediacaran Nama Group sedimentation in Namibia?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12645, https://doi.org/10.5194/egusphere-egu23-12645, 2023.

Carbonate veins are ubiquitous in many ore deposits and are often interpreted as a late stage or cross cutting fluid flow events in the ore deposit history. Faults accommodate rock displacement and the resulting zones of weakness act as conduits for magma and localised magmatic-hydrothermal fluid flow, leading to the formation of ore deposits. Dating of both low temperature veins and brittle fault material has been notoriously difficult because of a lack of ‘datable’ material. Using innovative techniques, it is now possible to date carbonate with the U-Pb isotopic system.

Here we use in-situ U-Pb carbonate geochronology to date a variety of fault material and mineralised and unmineralised veins within a major fault-controlled Cu-Au-Mo porphyry system in the central Yukon, Canadian Cordillera. Over 50 samples have been dated, revealing a long history of faulting and fluid flow in the deposit spreading over 10s of millions of years between ~75 Ma and <20 Ma. We combine petrography, U-Pb carbonate geochronology, trace element geochemistry, and clumped isotope analysis to interpret the full temperature-time evolution of the fluids within the deposit. Our results show the carbonate veins crystallised during the main ore-forming event at ~75 Ma. Subsequently, there was a prolonged period of fault-controlled fluid pulsing that likely concentrated metallic minerals in the deposit. The findings show that carbonate veins are not always late features within ore deposits and are an underutilised resource for understanding the full temporal and fluid evolution of a system. Carbonate U-Pb geochronology is therefore potentially incredibly useful for telling the previously untold and long history of fluid flow in a variety of deposit types.

How to cite: Mottram, C., Kellett, D., Dennis, P., and Clog, M.: Longevity of fault-controlled fluid flow within a Cu-Au-Mo porphyry (Yukon, Canada) revealed by coupled U-Pb carbonate geochronology and clumped isotope analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13236, https://doi.org/10.5194/egusphere-egu23-13236, 2023.

This work deals recently with the carbon (δ¹³C) and oxygen (δ¹⁸O) isotopic variations in the calcite associated with the hydrothermal mineralization to comprehend the nature of the ore fluid and its source and the evolution of the Yolindi Fe-Cu skarn deposit at North of Biga peninsula (NW Turkiye). The Yolindi area is made up of Torasan Formation (marble, hornfels, phyllite, and schist) which was intruded by Oligocene Hallaçlar volcanic rocks and later early Miocene Şaroluk plutonic rocks. The Yolindi Fe-Cu skarn deposit has been formed along the eastern contact of Şaroluk pluton with the Torasan Formation having widespread prograde and/or retrograde skarn, silicic, and carbonate (calcite) alteration. The prograde skarn is less observed and characterized by formation of garnet with subordinate magnetite. While, the retrograde skarn is highly extensive having epidote, actinolite, chlorite, and carbonate including pyrite, magnetite, chalcopyrite, and specular hematite with subordinate sphalerite and galena. Malachite, azurite, goethite, hemimorphite, and cerussite represent the supergene minerals which locally replaced Fe-oxide and Fe-Cu±Zn±Pb sulfide minerals. At the Yolindi Fe-Cu skarn deposit, carbon and oxygen isotope ratios of calcite minerals from the exoskarn zone are -15.5 to -2.0 ‰ relative to PDB and 0.9 to 17.9 ‰relative to V-SMOW, respectively. Furthermore, it was inferred from the calculated carbon isotopic composition of an ore-forming fluid (δ¹³C_CO2 = -12.7 to +0.8 ‰) that the carbon in the fluid is identical to the reduced carbon in sedimentary and metamorphic rocks. However, the calculated fluid's δ¹⁸O_H2O values—which vary from 0.9 to 17.2 ‰_VSMOW—indicate a mixture of metamorphic and magmatic origins for the hydrothermal fluid. This fluid mixing which has high range of C-O isotopic compositions has been due to a temperature effect along with either CO₂ outgassing or fluid/rock interactions. Additionally, the mineralizing fluid is most likely derived from the metamorphic dehydration of carbonate rocks in the Torrasan Formation during Yolindi skarn formation.

Keywords: carbon (δ¹³C) and oxygen (δ¹⁸O) isotope; Fe-Cu Yolindi skarn deposit; Biga peninsula; NW Turkiye

How to cite: Kaya, M., Kumral, M., Abdelnasser, A., Yalçın, C., Öztürk, S., Bayram, H. N., and Tanç-Kaya, B.: Evolution of the hydrothermal fluids of the Yolindi Fe-Cu skarn deposit, Biga peninsula, NW Turkiye: Evidence from carbon-oxygen isotopic variations of calcite minerals, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13798, https://doi.org/10.5194/egusphere-egu23-13798, 2023.

Uranium concentrations and ²³⁴U/²³⁸U activity ratios (δ²³⁴U) of Earth’s surface waters can provide independent and complementary information on changes in weathering regime and hydroclimate. The response of δ²³⁴U variation in surface waters in US Great Basin to climate change however remains unclear, which brings ambiguities in interpreting δ²³⁴U in aquatic carbonate deposits. Here, we analysed U concentration and δ²³⁴U in a suite of surface waters (creeks, springs and lake) as well as tufa deposits from the last glacial lake highstands in the Mono Basin, California, USA to assess the modern uranium budget in the lake water and the controlling factors on its δ²³⁴U. We find that U concentrations in groundwater springs are about one order of magnitude higher than those of creek waters. Hence, even though springs only deliver about 15% of annual inflow to the lake, they contribute 70% of U in the lake water. The residence time of U in lake water is calculated to be approximately 15,000 years, on the same order as those of Li, Na, and Cl, but significantly longer than those of alkaline earth elements. The δ²³⁴U in Mono Lake water is 180‰, same as in modern-day tufa deposits. The δ²³⁴U in lake highstand tufas is ~ 220‰, suggesting much more enhanced physical weathering associated with mountain glacial activities in the basin, even though chemical weathering was also stronger due to increased precipitation. On the other hand, the higher δ²³⁴U values (~ 250‰) in modern creeks and springs is consistent with the overall dry environment and stronger physical weathering in the basin. The 40‰ decrease in δ²³⁴U of lake water however cannot be explained by radiative decay. We hypothesis that lake water was more frequently stratified in the past, during the last glacial in particular, and the resulted anoxic environment in deep lake water has probably facilitated precipitations more enriched in ²³⁴U. 

How to cite: Lin, K., Hemming, S. R., Ali, G., Lin, I.-T., Su, C.-C., Stine, S. W., Hemming, N. G., and Wang, X.: Variability of (234U/238U) in surface water and tufa deposits: A study in the Mono Basin, California, USA, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15731, https://doi.org/10.5194/egusphere-egu23-15731, 2023.

The Ediacaran Period (635-538 Ma) was marked by considerable tectonic activity, including the end of the Pan-African episode – a long interval of mountain building, rifting, and reorganization spanning most of the Neoproterozoic Era. In Saudi Arabia, the Ediacaran outcrops were developed and preserved in several isolated half-grabens linked to the Ediacaran to early Cambrian Najd strike-slip fault system. This fault system manifested, particularly in the study area, as intensive fractures with a distinctive crack-seal veins morphology. Understanding the mechanism and origin of such fractures could provide unique insights into the structural evolution and paleo fluid flow throughout the history of the Arabian Plate. However, no studies have focused on different structural-controlled diagenetic processes in the Neoproterozoic sequences across the Arabian Plate. Here, we examined precipitated veins along a well-exposed 300 m thick Ediacaran host rock exposure by integrating high-resolution geochemical analyses, carbonate clumped isotopes, fluid inclusions, advanced petrography analysis of Cathodoluminescence microscopy to unravel the structural diagenesis of these Ediacaran strata. The δ¹⁸O and δ¹³C of the carbonate host rocks vary from -11.79 to -7.83‰, and -0.58‰ to 1.1‰, respectively. The estimated paleotemperature of the host rock derived from the clumped isotope is 47-60°C. Furthermore, the current results show that the calcite veins appear in different stages, orientations, geometries, and mineralogy. The δ¹⁸O and δ¹³C of the crack-seal veins vary between -11.2 to -7.8 ‰ and -2.9 to 1.9‰, respectively. The estimated clumped-derived paleotemperature of this vein is 95°C, even higher up to 136°C by utilizing the fluid inclusions. On the other hand, the Mn-rich later phase veins, which cross-cut the crack-seal veins, indicate an isotopic composition of -10.9 to -10.6‰ for δ¹⁸O and -18.2 to -15‰ for δ¹³C, with the estimated paleotemperature of 74-84°C. Hence, we argue that the structural diagenesis history in the study area comprises several distinct tectonic events and fluid circulation members along the fractures associated with different stages of basin evolution. Our findings, for the first time, offer a new understanding of paleo fluid circulation and also highlight the multi-proxy’s potential for investigating the structural diagenesis of calcite veins in the Ediacaran host rock in Arabia.

How to cite: Herlambang, A., Koeshidayatullah, A., Lu, C., Amao, A., Bello, A., Al-Ghamdi, F., Malik, M., and Al-Ramadan, K.: Crack-seal veins: records of 600-million-year complex tectonic and fluid flow evolution in Saudi Arabia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15952, https://doi.org/10.5194/egusphere-egu23-15952, 2023.

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb geochronology for carbonate minerals, calcite in particular, is rapidly gaining popularity as an absolute dating method. In this study, we review the latest technical progress in LA-ICP-MS carbonate geochronology, including the pre-screening strategies (on-line spot selection with a threshold, image-guided approach, and image-based approach), preferred instrumentation (Q-ICP-MS, SF-ICP-MS and MC-ICP-MS), calibration methods, common Pb corrections and the development of reference materials, with the aim of further improving the precision and accuracy of this technique. We emphasized the characterization of two calcite reference materials (TLM and LSJ07) for micro-beam U-Pb geochronology and C, O isotope ratio measurements. The latest geological applications of LA-ICP-MS U-Pb carbonate geochronology in dating of diagenesis and hydrothermal activity were reviewed.

How to cite: Wu, S., Roberts, N., and Lan, Z.: LA-ICP-MS U-Pb carbonate geochronology and its geological applications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15974, https://doi.org/10.5194/egusphere-egu23-15974, 2023.

With the introduction of climate action plans by many countries globally, the development of green technologies like electric vehicles and renewable infrastructure is expected to increase. These technologies are resource intensive, meaning we will require increased production of metals to meet the growing demands of society. However, discovery and exploration rates are not increasing at the same rate as demand. Improving understanding of ore system formation and evolution is a crucial step in aiding future exploration, to help supply these critical resources.

In hydrothermal systems, carbonate minerals (e.g., calcite and dolomite) are often associated with all stages of ore formation, with fluid inclusion thermometry and carbon-oxygen (C-O) isotope ratios traditionally used to study fluid temperature and composition. However, there are several challenges still remaining with these techniques, with fluid inclusions often too small, ruptured or deformed for adequate study. In carbonate minerals, the rare, heavy isotopes ¹³C and ¹⁸O bond or clump more frequently at lower temperatures, with the magnitude of clumping inversely temperature-dependent. Measurement of clumped C-O isotope ratios, using gas source isotope spectrometry, simultaneously yields carbonate δ¹³C and δ¹⁸O values and generates mineral precipitation temperatures, allowing fluid δ¹⁸O to be directly calculated. While traditionally applied to low temperate environments, recent applications have included hydrothermal ore systems to study fluid temperature and mixing. When combined with other techniques, such as strontium isotopes, new understanding of the sources, movement and compositional evolution of fluids can be deciphered.

Recent clumped C-O and strontium isotope analyses of ore-related carbonates from the Lisheen and Galmoy deposits, southern Irish Zn-Pb ore field, have facilitated the study of fluid sources, temperatures, mixing, and modification. Lisheen and Galmoy are  hosted in a belt of regionally dolomitized Lower Carboniferous (Mississippian) marine limestones, cut by a series of NE-SW-trending ramp-relay normal faults. Study of these deposits reveals that early dolomitizing and later hydrothermal fluids are part of a complex multistage continuum, with phases of fluid mixing, compositional buffering due to dissolution, and isotope resetting. Consequently, studies of carbonates in other deposits may yield new insights into ore formation, ultimately helping exploration for crucial resources.  

How to cite: Doran, A., Hollis, S., Menuge, J., Marca, A., Dennis, P., and van Acken, D.: Interpreting hydrothermal clumped isotope temperatures in the Irish Zn-Pb ore field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16279, https://doi.org/10.5194/egusphere-egu23-16279, 2023.

Coastal Fars is the main gas-bearing region in Iran, where the reservoir units are dedicated to the Paleozoic hydrocarbon system. Geochemical explorations in this region indicate that natural gas is commonly associated with elevated non-hydrocarbon components, especially hydrogen sulfide and carbon dioxide. Previously it was shown that the Thermochemical Sulfate Reduction (TSR) is the most probable mechanism, accounting for H₂S occurrence in Permo-Triassic reservoirs in this region; however, its effect on the accumulated gas’s chemistry transformation has not been studied thoroughly. In this study, the molecular and isotopic composition of 12 gas samples in addition to the previously-published results of integrated analyses on rock and condensate, were utilized to trace potential alterations caused by the given phenomenon exhaustively. A slight increase in aromatic to saturate hydrocarbon components ratio with the extent of TSR and the presence of reported sulfur-rich pyrobitumen (Saberi, et al., 2014) indicate liquid hydrocarbon involvement in the primary stage of the sulfate reduction process. Further, the differential increase of δ¹³C of gas components, decrease of δ¹³C (methane) - δ¹³C (ethane) (from -4.3 to -13.1‰), and increase in carbon-dioxide concentration with the increase of hydrogen sulfide along with gas dryness (from 91 to 96%) show the dominancy of C₂-C₄ hydrocarbon gas components in the second stage of TSR. Comparative low reservoir temperature (~90°C) does not correspond to the contribution of methane into the given phenomenon; however, a noticeable increase in δ¹³C (methane) (from -41.7 to -34.7‰) with the increase of hydrogen sulfide was seen. Thermochemical Sulfate Reduction impact on studied parameters is analogous to thermal maturation, but the process from heavy-hydrocarbon-dominated TSR to methane-dominated TSR presents different trends of δ¹³C (methane) - δ¹³C (ethane), ln(C₁/C₂) from those of maturation (Hao, et al., 2008). Simultaneous carbon-dioxide content increase and decrease in its isotopic composition with the extent of TSR indicate its presence relevancy to the given phenomenon; however, carbon isotope values of CO₂ (from -5.92 to -13.93‰) are too heavy to verify this idea. According to Dai et.al (Dai, et al., 1996) it can be concluded that carbonate's dissolution has contributed to carbon-dioxide gas. Hence, a series of TSR corresponding to condensate, wet gas, and dry gas stages, respectively, has led to higher aromatic/saturate ratios, heavier hydrocarbon components, lighter carbon dioxide molecules, and relative gas dryness in the studied fields.

 Bibliography

• Dai, J. X., Song, Y., Dai, C. S. & Wang, D. R., 1996. Geochemistry and Accumulation of Carbon Dioxide Gases in China. AAPG Bulletin, 80(10), pp. 1615-1626.
• Hao, F. et al., 2008. Evidence for multiple stages of oil cracking and thermochemical sulfate reduction in the Puguang gas field, Sichuan Basin, China. AAPG Bulletin, 92(5), pp. 611-637.
• Saberi, M. H., Rabbani, A. & Ahmadabadi, K. A., 2014. The Age and Facies Characteristics of Persian Gulf Source Rocks. Petroleum Science and Technology, Volume 32, pp. 371-378.

How to cite: Gholizadeh, H., Krasnova, E., and Rabbani, A.: Assessment of natural gas chemistry alteration by extent of H2S production and evidences for multiple stages of TSR in two gas fields in Gavbandi-High, Iran, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-782, https://doi.org/10.5194/egusphere-egu23-782, 2023.

A key task in the analysis of exploration geochemical data is the selection and application of efficient classification models to discriminate mineralization-related signals from other processes affecting variation in element concentrations. Similarly in environmental or urban geochemistry one objective is to separate geochemical patterns associated with anthropogenic contamination from geogenic processes. To classify geochemical maps into background or anomalous samples or regions, a variety of mathematical and statistical models have been developed. In this study various fractal modelling has been applied to centered logratio transformed Cu, Ba, Mn, Pb, Zn, In, As, Au, and Ag contents of soil samples from the Geochemical Atlas of Cyprus. Areas with contamination have previously been shown not to display normal fractal behavior for values exceeding lithology-dependent background populations. Therefore, two new fractal methods – concentration-concentration (C-C) and concentration-distance from centroid-points (C-DC) – were applied to discriminate anthropogenic from geogenic anomalies. One of the strongest indicators of proximity to major Cu mineralization is In. The C-C model displays broad similarity between the Cu-In pairing and the raw Cu, and between its reverse in the In-Cu pairing and raw In. Of the five populations that emerge from the Cu-In fractal model, the first two (regional background and weakly anomalous) are largely restricted to the Circum-Troodos Sedimentary Succession units. The moderately anomalous population extends across all the basalts and north from the Troodos Ophiolite (TO) across the fanglomerates and more recent alluvium-colluvium that contains material shedding north off the TO. It is noted that the strongest anomalies are at the boundary between the sheeted dyke complex and basalts and on one of the major NE-trending structures that cut across the TO, but where there are only a small number of minor Cu mineralization occurrences. In the C-DC model, the centroids used to model the spatial variation of the soil geochemistry were the known mineral deposits. The Cu C-DC model delivers just two populations that are lithologically-controlled. The first spans the ultramafic TO core and the Pakhna Formation carbonates (the two extremes in the raw data geochemical compositions), and all other units, including the TO mafics, Mamonia Terrain, and the fanglomerates and alluvium-colluvium areas in the second population. The In C-DC model is somewhat similar to the In-Cu C-C model, but the second major population is more restricted to the sections of the basalts containing known Cu mineralization as well as a restricted zone in the sheeted dykes in western TO. Applying the C-DC model to the transformed scores, there are three main populations evident. The highest one contains all the known Cu mines and mineral deposits, as well as a number of NE-trending zones that cut across the sheeted dykes on the western and the eastern sides of the TO, and which also appear to follow the major sinistral faults that transect the TO.

How to cite: Sadeghi, B. and Cohen, D.: Discrimination of anthropogenic contamination and the effects of mineralization in soils from background patterns using multifractal modelling: Cyprus case study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1585, https://doi.org/10.5194/egusphere-egu23-1585, 2023.

Mineralogical analysis is critical for understanding the origins and properties of various rock types. Recent advancements in artificial intelligence technologies, particularly supervised deep learning, have transformed qualitative and quantitative mineral analysis. However, current deep-learning approaches require high-quality annotated datasets to acquire and identify different mineralogical characteristics and properties. This is exacerbated by the time-consuming and error-prone labeling processes for the datasets. With self-supervised architectures matching supervised approaches in many computer vision tasks, it is timely to investigate the potential of Self-Supervised Learning (SSL) models in the geosciences. As a result, we use a self-supervised semantic segmentation model to identify and characterize minerals in thin sections, with the model attempting to obtain categories of interest from images without the need for human intervention in annotating the minerals. In this study, we adopted a Self-Supervised Transformer architecture and proposed SelfMin to automatically segment out pyrite minerals from other background gangue minerals in the thin section. Our proposed method achieved 80% in the mean Intersection over Union (mIoU) metric, indicating the model's ability to accurately segment minerals that were not labeled during the annotation process. This work describes the first use of self-supervised deep learning in mineralogical analysis. Further application of this proposed method would allow a robust and efficient advanced qualitative and quantitative mineralogical analysis. It also demonstrates how this technique can be implemented to avoid the need for a large volume of high-quality labeled datasets in other image-based deep learning geosciences analyses.

How to cite: Koeshidayatullah, A. and Ferreira, I.: SelfMin: Self-Supervised Deep Learning for Advanced Mineralogical Analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2189, https://doi.org/10.5194/egusphere-egu23-2189, 2023.

Soil parameters are relevant and valuable for various applications such as agriculture production, scientific research, and policy making. Since acquiring such physical or chemical information could be cost-consuming by traditional methods, remote sensing and data analysis have become exciting research fields for soil parameter prediction tasks.   Many papers show that minerals and chemical materials correlate with the corresponding spectral reflectance. Based on this characteristic, there are many works using different data analysis methods such as machine learning and deep learning to predict soil properties, especially from multi- and hyper-spectral images. However, limited by the small data size, many models suffer from the overfitting problem and could not extrapolate to unseen data. Moreover, the currently existing methods only generate predictions with no consideration of the correlation among different target parameters. In this work, we propose and implement a deep learning based multitask method to predict multiple chemical properties simultaneously from hyperspectral images. To initialize the model, we use the pre-trained weights from ImageNet. To make better use of the correlation among different parameters, our model consists of shared layers and task-specific branches where each customized branch generates the prediction for one target property. Our method is implemented on the dataset from the Hyperview challenge organized by KP Labs and ESA. In this dataset, 1732 hyperspectral patches are available now and each patch has 4 soil parameters including K, P205, Mg, and pH. After comprehensive experiments, our method achieves the highest score of 0.87, which shows superior performance in this regression task.

How to cite: Zhao, X., Xiong, Z., and Zhu, X.: Soil Parameters Prediction from Hyperspectral Images via Multitask Learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2439, https://doi.org/10.5194/egusphere-egu23-2439, 2023.

An Application Programming Interface (API) is a secured, documented and accessible web service and an entry point to any database—both relational and non-relational. As a rule, it exposes the data in different formats and allows filtering of the data by utilizing the query parameters. Accordingly, it allows the developers and data scientists to retrieve and query data through HTTP or WebSocket protocols using command-line HTTP clients or language-specific ones (e.g., axios, requests). The most complicated and essential aspects of developing an API are choosing the stack, structuring the codebase and optimizing the application's performance. 

A general rule of thumb is to develop an API to be (1) platform-independent and (2) support the versioning and evolution of the service by adding new functionalities while supporting the previous versions. Other features of a robust and reliable API are documentation according to OpenAPI Specification (OAS), scalability, caching, development and production environments portability, concurrency and more.

mineralogy.rocks API for mineralogical and related data is currently a work in progress with open-source code. It follows RESTful architectural concepts, best practices of clean codebase development and the twelve-factor methodology. The application is developed in Django—a Python web framework and utilizes PostgreSQL 13 database under the hood. The APIs' design is organized around the resources, e.g. the endpoints' naming conventions are predictable, standard and follow the same patterns. 

The codebase structure deviates from the standard out-of-the-box structure provided by the Django framework to isolate database-, server- and application-specific utilities. The local environment of the application is set up using Docker and docker-compose containerization technology for the efficiency of the development. 

The CI/CD integration has zero downtime—it is organized around GitHub Actions that allow for building the application, deploying the isolated container to a cloud, and updating the Kubernetes cluster application accordingly. 

The mineralogy.rocks API supports open science and promotes the innovation, quality, and public impact of mineralogy. Our open science activities are implemented to make the results produced and used in research publicly available and their metadata quickly and widely available for reuse.

This project, No. 3007/01/01, has received funding from the European Union’s Horizon 2020 research and innovation Programme based on a grant agreement under the Marie Skłodowska-Curie scheme No. 945478 and was supported by the Slovak Research and Development Agency (contract APVV-19-0065).

How to cite: Gavryliv, L., Ponomar, V., and Putiš, M.: Designing an API for a mineralogical database, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3925, https://doi.org/10.5194/egusphere-egu23-3925, 2023.

Reconstructing the emergence of the modern continental crust is crucial to understand the evolution of the crust, the onset of plate tectonics, elemental cycling, and long-term climate. However, it remains highly contentious about when and how the major subaerial continental crust emerged over time. Here, we used a machine learning (ML) model (XGBoost) to reveal the exposed history of continental crust over the last 3.8 billion years ago (Ga). First, we compiled ~10,000 modern subaerial or submarine basalts with major and trace elements to train the ML model. Then, the trained ML model (with resampling) was utilized to predict and calculate the mean proportions of subaerially erupted continental basaltic rocks since 3.8 Ga. The result suggested that the subaerial proportion only reached about 50% at ~2.5 Ga, indicating the exposure of the continental crust was far from the present-day level at the end of the Archean era. On the other hand, since ~1.8 Ga, the subaerial proportion of the continental crust exhibited a dynamic balance between ~60% and 80%, reaching the present-day level.

How to cite: Liu, C., Keller, C. B., Liu, X., and Zhang, Z.: The emergence of Continental Crust Revealed by Machine Learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4648, https://doi.org/10.5194/egusphere-egu23-4648, 2023.

The diverse suite of trace elements incorporated into apatite in ore-forming systems has important applications in petrogenesis studies of mineral deposits. Trace element variations in apatite can be used to distinguish between different types of rocks as well as discriminating between deposit types, and thus have potential as mineral exploration tools. Such classification approaches commonly employ two-variable scatterplots of apatite trace element compositional data. While such diagrams offer easy and convenient visualization of compositional trends, they often struggle to effectively distinguish deposit types because they do not employ all the high-dimensional (i.e. multi-element) information accessible from high-quality apatite trace element analysis. To address this issue, we employ, for the first time, a supervised machine learning-based approach (eXtreme Gradient Boosting, XGBoost) to correlate apatite compositions with ore deposit type, utilizing high-dimensional information. We evaluated 8629 apatite trace element data from five deposit types (porphyry, skarn, orogenic Au, iron oxide copper gold, and iron oxide-apatite) along with unmineralized apatite to discriminate between apatite in mineralized vs unmineralized systems. We could show that the XGBoost classifier efficiently and accurately classifies high-dimensional apatite trace element data according to the ore deposit type (overall accuracy: 94% and F1 score: 89%). Interpretation of the model using the SHAPley Additive exPlanations tool (SHAP) shows that Th, U, Eu and Nd are the most indicative elements for classifying deposit types using apatite trace element chemistry. Our approach has broad implications for the understanding of the sources, chemistry and evolution of melts and hydrothermal fluids resulting in ore deposit formation.

Keywords: Machine learning; apatite; Trace elements; Ore deposit type; XGBoost

How to cite: Zhou, T., Qiu, K., and Wang, Y.: From Trace Elements to Petrogenesis: A Machine Learning Approach to Determine Ore Deposit Type from Trace Elements Analysis of Apatite, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4857, https://doi.org/10.5194/egusphere-egu23-4857, 2023.

Analysis of optical microscopic image data is crucial for identifications of mineral phases, and thus directly relevant to the subsequent methodology selections of the further detailed petrological exploration. So far, large-dimensional image analyses are dominantly based on digital image datasets, and the automatic identification of the optical microscopic data is still poorly examined. Here, by testing the Swin Transformer, a deep learning algorithm on different metal mineral phases, we proposed a well-behaved mineral recognizer with high accuracy of 92.8% and strong global ability. In addition, we apply Class Activation Mapping (CAM) is introduced for the first time in mineral identification tasks and reveals the interpretability of the models, allowing us to more intuitively observe that mineral edges are the most effective model identification features. The results demonstrated that optical microscope data can not only rely on pixel information, and machine learning can accurately extract all available attributes, which reveals the potential to assist in data exploration and provides an opportunity to carry out spatial quantization at a large scale (cm-mm).

Keywords: Metal mineral; Microscope images; Deep learning; Swin Transformer; Class Activation Mapping

How to cite: Cai, Y., Qiu, K., and Hou, Z.: Metal mineral classification under microscope images using deep learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5095, https://doi.org/10.5194/egusphere-egu23-5095, 2023.

The standard absolute entropies of many minerals and mineral-based inorganic materials are unknown, thereby precluding a complete insight into their thermodynamic stability. This includes many apatites. The Apatite supergroup is one of the largest groups of minerals. Consequently, they are an incomparable testing ground for finding regularities in the variation of their thermodynamic function of state, e.g., standard entropy (S°). In the early 2000’s Jenkins and Glasser [1] showed that the formula unit volume alone, V_m, can be used to estimate the standard entropy for any inorganic compound.

It was recently indicated that in terms of their thermodynamic properties, the apatite supergroup splits into distinct subgroups (populations) [2]. These subgroups are formed by Me₁₀(AO₄)₆X₂ with the same Me²⁺ cations (e.g., Pb²⁺, Cd²⁺, Ca²⁺, Ba²⁺, Sr²⁺) and tetrahedral AO₄^3- anions (e.g., A=P, As, V), but with different anions at the X position (e.g., F^-, Cl^-, Br^-, I^-, OH^-). We found strong linear relationships between S° of apatites and their V_m observed within these subgroups. A system of linear relationships (calibrated with existing experimental data) indicating high positive correlations within selected subgroups of apatites is presented in Fig. 1.

Fig. 1 Standard entropy (S°) vs. formula unit volume (V_m)for selected apatite subgroups. Errors bars are within the marker.

Table 1. Selected estimated standard entropies (S°) and calculated formation entropies (ΔS°_{f, el})of iodine apatites.

Using the new estimated with high accuracy S° values, it is possible to calculate the Gibbs energy of formation and plot stability fields for apatites for which this has not been possible so far. Financial support for the research was provided to B.P. by the Polish National Science Centre (NCN) grant No. 2017/27/N/ST10/00776.

References:

[1] Jenkins, H. D. B., & Glasser, L. (2003). Standard absolute entropy, values from volume or density. 1. inorganic materials. Inorganic Chemistry, 42(26), 8702-8708.

[2] Puzio, B., & Manecki, M. (2022). The prediction method for standard enthalpies of apatites using the molar volume, lattice energy, and linear correlations from existing experimental data. Contributions to Mineralogy and Petrology, 177(11), 1-34.

[3] Wang, J. (2015). Incorporation of iodine into apatite structure: a crystal chemistry approach using Artificial Neural Network. Frontiers in Earth Science, 3, 20.

How to cite: Puzio, B. and Manecki, M.: Estimation of missing third-law standard entropy of apatites using the optimized Volume-based Thermodynamics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5863, https://doi.org/10.5194/egusphere-egu23-5863, 2023.

Zircon, a stable paragenetic mineral in various geological environments, has been recognized as a great tool to study the ages of primary rocks. Trace elements of zircons thus can record the geological evolution processes. Zircon-associated trace elements have been long studied for zircon classification and formation traditionally using binary diagram technique, classical examples including Th-U and La_N-(Sm/La)_N diagrams. However, with the massive increase of zircon research, the traditional binary diagrams currently cannot precisely classify zircon types because the binary plot cannot demonstrate the higher dimensional information. It therefore significantly restricts a clear understanding of zircon formation. To address the research gap, we performed the machine-learning-based approaches on 3498 zircon trace-element data of different zircon genetic types, producing high-dimensional zircon-classification diagram plots. We applied and tested four machine learning methods (random forest, support vector machine, artificial neural network, and k-nearest neighbor) and proposed that support vector machine can best contribute to zircon genetic classification study, with an 86.8% accuracy in the prediction of zircon type and formation. In addition to the high-dimensional zircon classification diagram, this work massively improves the accuracy of zircon formation analyses by trace elements, which benefit future studies in zircons. Using the machine learning approach on zircon trace element big data is an effective multidisciplinary exploration of the modern data science technique in the geochemistry study.

How to cite: Zhu, Z., Qiu, K., Zhou, F., Wang, Y., and Zhou, T.: Machine learning based approach for zircon classification and origin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6284, https://doi.org/10.5194/egusphere-egu23-6284, 2023.

Characterizing the types of crystalline structures that form in different environments helps us to better interpret the geologic record and deepens our understanding of mineral stability. To this end, the Dolivo – Dobrovol’sky symmetry index provides a convenient way to quantify the statistical trends in the symmetry of minerals over time (Bermanec et al. 2022). Behavior of the Dolivo - Dobrovol’sky symmetry index was investigated for different paragenetic modes of minerals (Hazen and Morrison 2022). Two datasets were used and compared (code and datasets are available on https://github.com/NoaVidovic/pgm-mineral-pairs-pg). The first one used only minerals, and each mineral was considered just once. In contrast, in the mineral–paragenetic mode pair dataset, minerals were counted once for each of the paragenetic modes in which they occurred.

The paragenetic mode dataset incorporates a number of properties associated with each of more than 60 modes of formation, including relative age and order of that mode’s first appearance, estimated minimum and maximum temperature and pressure of formation, and duration. Paragenetic mode order does not substantially affect the symmetry index of minerals. However, some trends are evident when inspecting the properties of given paragenetic modes. The symmetry indices show a strong correlation with the maximum temperature, maximum pressure, and minimum pressure of paragenetic modes they belong to (Hazen et al. 2022) with correlation coefficients of 69%, 84% and 95%, respectively when using the mineral dataset. These trends show that minerals formed at higher temperature display higher overall symmetry. Trends for pressure are enigmatic: correlations show that minerals formed at higher minimum pressure tend to favor lower symmetry, whereas minerals formed at higher maximum pressure tend to favor higher symmetry.

When using the mineral–paragenetic mode dataset, the correlation coefficients are significantly lower at 42%, 30% and 89% for maximum temperature, maximum pressure, and minimum pressure, respectively. The lower correlation coefficients obtained using the mineral–paragenetic mode pairs might indicate that the paragenetic mode is not as important in terms of trends in symmetry as initially thought. On the other hand, considering a much higher correlation coefficient for the mineral dataset, perhaps there is a more dominant effect where certain P-T conditions tend to favor certain types of symmetry at equilibrium.

How to cite: Bermanec, M., Vidović, N., Gavryliv, L., M. Hazen, R., R. Hummer, D., M. Morrison, S., Prabhu, A., and R. Williams, J.: Symmetry statistics of mineral – paragenetic mode pairs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8924, https://doi.org/10.5194/egusphere-egu23-8924, 2023.

Machine learning has been shown to be a highly effective method for classifying geochemistry data, such as mineral forming environments and rock tectonics. However, it can be difficult to understand the decision-making processes of these models. To address this issue, we propose the use of Decision Boundary Maps (DBMs) as a visualization tool for interpreting machine learning models. These maps project high-dimensional geochemistry data onto a 2D plane and depict the decision boundaries in the projected space, providing a visual representation of the algorithm's decision-making processes. In addition, DBMs can reveal trends, correlations, and outliers in the data, helping to interpret the results obtained from machine learning-based geochemistry data classification. Seeing the positions of data points, rather than just class labels, is especially valuable because samples in geological categories often follow a sequence, such as a magmatic to hydrothermal transition. Observing the positions of data points allows for the identification of trends from one class to an adjacent class.

How to cite: Wang, Y., Qiu, K., Telea, A., Hou, Z., and Yu, H.: Interpreting Machine Learning Models for Geochemistry Data Classification using Decision Boundary Maps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10228, https://doi.org/10.5194/egusphere-egu23-10228, 2023.

In the last decades, the use of Raman spectroscopy on dispersed carbonaceous material in rocks has become a promising tool for geothermometry and thermal maturity assessment. In diagenesis the main problem is linked to organofacies composition and the need of time-consuming optical classification (Henry et al., 2019, Sanders et al., 2022). In this work, three different methods of clustering analysis on Raman spectra were tested as a potential approach to recognize the three main organofacies (amorphous organic matter, translucid and opaque phytoclasts) that characterize a set of 27 organic-rich samples from the Lower Toarcian source rock interval (Schistes Carton) of the Paris Basin (France).

Raman analyses were performed on concentrated organic matter obtained by acid attacks, with around 60 counts for each sample. Principal Component Analysis (PCA) was applied to reduce the dimensionality of each dataset on a 2-D score-plot. Unsupervised clustering was then performed by using three different clustering algorithms: k-means, Gaussian Mixture Models (GMM), and Density-Based Spatial Clustering for Applications with Noise (DBSCAN). The main task of these algorithms is to correctly assign the number of clusters, their size, orientation, and distribution in the score-plot that related to the heterogeneities in organofacies composition.

Results show the best performances are achieved through the application of GMM clustering that can successfully determine cluster’s geometry and optimal numbers with an accuracy mostly higher than 80% for the translucid phytoclasts group, that is the target for thermal maturity assessment.  This is a preliminary attempt showing promising application for unsupervised learning techniques coupled with Raman spectroscopy that could be applied in industrial routinely organic matter characterization or in the analysis of big dataset in both Earth and planetary sciences.

Henry, D. G., Jarvis, I., Gillmore, G., & Stephenson, M., 2019. Raman spectroscopy as a tool to determine the thermal maturity of organic matter: Application to sedimentary, metamorphic and structural geology. Earth-Science Reviews 198, 102936.

Sanders, M. M., Jubb, A. M., Hackley, P. C., & Peters, K. E., 2022. Molecular mechanisms of solid bitumen and vitrinite reflectance suppression explored using hydrous pyrolysis of artificial source rock. Organic Geochemistry 165, 104371.

How to cite: Schito, A., Vergara Sassarini, N. A., Gasparrini, M., Michel, P., and Corrado, S.: Unsupervised Clustering applied on Raman spectra of dispersed carbonaceous material: a case history from the Paris Basin (France), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14683, https://doi.org/10.5194/egusphere-egu23-14683, 2023.

Many macroscopic transport properties and physical processes, such as the flow of fluids through a porous medium, are directly controlled by its microstructure, specifically the presence and connectivity of individual pore spaces at micron and submicron scales. Reconstructing and evaluating the material properties of porous media plays a key role across many engineering disciplines from subsurface storage (e.g., CO2 and hydrogen) to geothermal energy and reservoir characterization. As such, the rapid and reliable characterization, evaluation, and simulation of complex pore microstructures is required not only to enhance our understanding of the fundamental processes occurring at the pore scale, but to also better estimate their material behavior on a larger scale.

These material behaviors are inherently volumetric and therefore cannot be accurately modelled using two-dimensional (2D) data alone. As a result, the accuracy of reconstruction techniques used to extract these morphological properties and spatial distributions is in part determined by the quality of available three-dimensional (3D) microstructural datasets. However, in comparison to their 3D counterparts, 2D imaging techniques are typically more cost efficient, easier to collect, and higher resolution. Our goal of generating statistically accurate 3D reconstructions of complex pore microstructural distributions based on high resolution 2D datasets is essential to bridging this dimensionality gap.

Newly explored 2D-to-3D reconstruction techniques based on deep-learning (DL) algorithms offer an alternative means of generating robust and statistically representative digital 3D rock reconstructions by measuring some spatial morphological properties and statistical microstructural descriptors (SMDs) of porous media samples from high-resolution 2D datasets. These DL models are highly flexible and capable of capturing a variety of complex microstructural features given representative 2D training datasets. In this paper, we implement a newly developed deep Generative Adversarial Network (GAN), known as SliceGAN, to synthesize novel binary digital 3D reconstructions using high-resolution 2D back-scattered electron (BSE) images obtained from thin-sections oriented in the x-, y- & z-direction.

Our trained model is capable of accurately reconstructing complex 3D microstructural features of porous media through capturing the underlying (micro-)structural and morphological properties contained in the original sample (2D) thin-sections. To demonstrate the effectiveness of our trained model, we conducted a comparative analysis between the generated 3D reconstructions and real sample datasets by evaluating morphological properties (volume fraction, surface area, equivalent diameter, pore orientations, etc.) as well as the widely popular SMD the two-point correlation function (S₂ (r) ). The resulting reconstructions are virtually indistinguishable, both visually and statistically, from the real sample. Our research paves the way for quickly and accurately describing complex heterogenous media for the prediction of transport processes, for example, carbon and hydrogen storage and extraction.

How to cite: Vogel, H., Amiri, H., Arias, A., Plümper, O., and Ohl, M.: 3-D Reconstructions of Porous Media from 2-D input via Generative Adversarial Networks (GANs), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15241, https://doi.org/10.5194/egusphere-egu23-15241, 2023.

Recent technological advances allow geoscientists to generate high-resolution (HR) imagery using a variety of different beam-forming mechanisms (e.g. visible light, X-Rays, or charged particles such as electrons and ions). One of the main limitations in producing HR data is the required acquisition time at high magnifications. For example, back-scattered electron (BSE) mapping of a standard petrographic thin section at a resolution of 50nm/pixel takes approximately 60 days and is associated with a storage requirement in the order of 700 GB. Deep-learning methods have proven effective for resolution enhancement in regular photographic images, and in this work we present an integrated image registration and upscaling workflow to enhance image resolution, using real-world BSE datasets.

The proposed workflow requires the acquisition of one, or multiple, HR regions within a region that is imaged at low-resolution (LR). Next, close to pixel-accurate image registration is performed by using the successive implementation of two concepts: i) first the precise location of the HR region within the LR region is determined by using a Fast Fourier Transform algorithm (Lewis, 2005), and ii) final image registration is achieved by iteratively calculating a deformation matrix that, using Newton’s method of optimization, is aiming to minimize an error function describing the differences between both images (Tudisco et al., 2017).

Subsequently, matching HR and LR image pairs are fed into a Generative Adversarial Network (GAN) that learns to produce HR images from the LR counterparts. A GAN consists of two neural networks, a generator and a discriminator. The generator produces synthetic HR data based on LR input, and the discriminator attempts to classify the data as either real HR or synthetic HR. The two networks are trained together in an adversarial process, with the goal of the generator producing synthetic data that the discriminator cannot distinguish from real data.

We demonstrate our method on a variety of large real-world datasets and show that it effectively increases the resolution of full-size BSE maps up to a factor of four, while being able to resolve important features. The upscaling of BSE data, with a factor of four, is associated with a 90% reduction in beamtime and a factor 16 reduction in storage requirements. Image registration, preprocessing, and model training on a high-performance workstation takes 12-24 hours. Having a trained model, inference can be done using a regular laptop.

[1] Lewis, J. P. "Fast normalized cross-correlation, Industrial Light and Magic." unpublished (2005).

[2] Tudisco, Erika, et al. "An extension of digital volume correlation for multimodality image registration." Measurement Science and Technology 28.9 (2017): 095401

How to cite: van Melick, H. and Plümper, O.: Resolution enhancement using deep learning methods: an integrated workflow applied to real-world Back-Scattered Electron (BSE) data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15285, https://doi.org/10.5194/egusphere-egu23-15285, 2023.

As geochemical data enable understanding of the Earth system and help to address critical societal issues the organisation thereof is important. Questions asked about processes affecting our environment and geological past become more complex and interdisciplinary in nature as well as multidimensional. To help answer these questions within the geochemistry research capabilities and data compilations are required to be comprehensive and both human and machine readable. Various international organisations are building infrastructure to capture and distribute geochemical data in a consistent manner adhering to the FAIR principles. 

Since May 2021 the OneGeochemistry initiative has officially started efforts towards aligning these organisations’ data frameworks in order to standardise how geochemical data is reported around the globe. In November 2022 the OneGeochemistry initiative applied and was granted to become the OneGeochemistry CODATA Working Group as part of the International Science Councils Committee on Data. The initiative has now also been endorsed by the Geochemical Society, the European Association of Geochemistry and the Working Group has been endorsed by the IUGS Commission on Global Geochemical Baselines. Coordination of the OneGeochemistry initiative is funded through the WorldFAIR project where it is one of the work packages in the larger ‘WorldFAIR: Global cooperation on FAIR data policy and practice’ project. A FAIR Implementation Profile analyses of the geochemistry communities of Australia (AusGeochem), USA (EarthChem, AstroMat) and Europe (GEOROC-DIGIS, EPOS-MSL, NFDI4EARTH) resulted in recognition of the need for common vocabularies for geochemistry data reporting as one of the most important actions to undertake towards international geochemistry data interoperability. A task adopted by EarthChem-DIGIS(GEOROC)-GFZ(DataSystems) collaboration and Research Vocabularies Australia.

Here we will present an overview of the current OneGeochemistry initiative and its preliminary outcomes with regards to FAIR Implementation Profiles and processes that will help enable geochemical data interoperability between various stakeholders.

How to cite: Prent, A., Wyborn, L., Klöcking, M., Lehnert, K., Elger, K., Hezel, D., Profeta, L., ter Maat, G., Farrington, R., and Rawling, T.: The OneGeochemistry initiative as a CODATA Working Group; bringing together international geochemical data systems for easy data discovery, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16338, https://doi.org/10.5194/egusphere-egu23-16338, 2023.

Global geochemical datasets are increasingly valuable for solving research questions in geochemistry, volcanology and beyond. To support new research, open sharing and access of geochemical data needs to be easy for researchers so they can take full advantage of the rapidly growing volume of data generated in laboratories across the globe, and to comply with the principles of Open Science. Instead, the fragmented landscape of geochemical data systems makes it difficult for researchers to find, access, and contribute their data: Geochemical data are curated and published in a range of thematic, institutional, and programmatic data systems that differ in architecture, metadata schemas, terminology, and data output formats. Researchers have to figure out where to obtain the data they need; learn to use different search applications; retrieve data from multiple databases and painstakingly reformat the datasets they obtained from different systems to integrate them. They need to select an appropriate repository for their data, and potentially work with different submission systems and templates. Collaboration among geochemical data systems is a critical step to overcome this fragmentation and facilitate geochemical data management and access for the research community by coordinating, aligning, and integrating their systems. Through collaboration, data repositories and databases can also leverage each other’s expertise and resources to operate their services more effectively and efficiently.

We here report about new collaborative efforts among four geochemical data systems that aim to harmonize and integrate their data holdings and software ecosystem for the benefit of the research community and to improve their sustainability: EarthChem (https://earthchem.org/), GEOROC (https://georoc.eu/), MetBase (https://metbase.org/), and the Astromaterials Data System (https://www.astromat.org/).  Building on the long-term collaboration between EarthChem and GEOROC, this collaboration leverages the new development of the Astromaterials Data System with modern technology and two new projects funded to overhaul the infrastructure of the GEOROC and MetBase databases as an opportunity to jointly develop a more resilient, sustainable platform for data exchange. Results of the collaboration so far include: a) alignment of the Astronaut and MetBase data models b) migration of the MetBase data holdings into the Astromat synthesis database; c) alignment of the EarthChem and GEOROC data models; d) new automated synchronization process of GEOROC data to the ECP; e) harmonized vocabularies for chemical variables, analytical methods (Others are in development in alignment with emerging efforts of the OneGeochemstry initiative); f) design of the future shared architecture of EarthChem and GEOROC that includes plans for a joint data entry tool for curators and a single data submission platform for researchers to contribute their data to the affiliated domain repositories. 

The ultimate goal of this harmonization between EarthChem, Astromat, GEOROC and MetBase is to make it easier for researchers to access and contribute data. We hope to integrate further systems in the future, building on ongoing collaborations with the Australian Geochemistry Network, the US Geological Survey, SAMIS (Sample Analysis Microinformation System), the GFZ Data Services, and the Sparrow software.

How to cite: Lehnert, K., Klöcking, M., Hezel, D., Profeta, L., Ji, P., and Sturm, A.: Overcoming Fragmentation of Geochemical Data Resources: Collaboration between EarthChem, Astromat, GEOROC, and MetBase, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16683, https://doi.org/10.5194/egusphere-egu23-16683, 2023.

Symplectitic intergrowth of orthopyroxene (host) with magnetite and minor ilmenite (lamellae) are recorded from Atlantis Bank, an Oceanic Core Complex on Southwest Indian Ridge. The texture is typically developed in oxide-rich gabbros recovered from the lower crustal section in this region and formed at the expense of olivine. Usually, the intergrowth primarily occurs where the olivine is in contact with magmatic magnetite and/or ilmenite. The maximum length and width of the lamellae in thin section go up to 350 µm and 20 µm respectively. The vermicular lamellae commonly maintain orthogonal relationship to the olivine grain boundary. A significant characteristic feature of this symplectitic intergrowth is the presence of domain structure, where each domain is characterized by the different orientation of vermicular lamellae. Locally, occurrences of amphibole rim abutting the intergrowth are noted. Development of orthopyroxene + Fe-Ti oxide symplectite is linked to the olivine oxidation endorsed by the interstitial Fe-Ti oxides during the progressive evolution of the lower oceanic crust at Atlantis Bank. Consequently, the occurrence of this texture dominantly from the oxide-rich lithologies bears significance. A phase equilibria modelling adopted to better comprehend the relationship between the state of oxidation and symplectite formation at Atlantis Bank indicates that this texture can be developed at relatively lower oxidation state at lower temperature for the observed range in olivine compositions. The formation temperature of the oxy-symplectites estimated from ilmenite-magnetite pairs ranges from ~730° to 450°C over an oxygen fugacity range of -0.86 to +3.83 (FMQ buffer). We suggest that, the development of this intergrowth took place under the influence of late-stage Fe-Ti oxides at subsolidus condition, which fostered the olivine oxidation. Temperature and oxygen fugacity ranges estimated from majority of the discrete ilmenite and magnetite pairs away from the symplectites however suggest relatively higher temperature and lower oxidation state (temperature ranges from 720° to 550°C, and oxygen fugacity ranges from -1.91 to +2.77 (FMQ buffer)). Higher oxygen fugacity values recorded from the symplectites further validate the effect of oxidation.

How to cite: Dhar, A., Ghosh, B., Bandyopadhyay, D., Morishita, T., Tamura, A., Koley, M., and Roy, S.: Development of oxy-symplectites in the oceanic lower crust at Atlantis Bank Oceanic Core Complex, Southwest Indian Ridge- manifestation of fluctuating oxidation state, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-440, https://doi.org/10.5194/egusphere-egu23-440, 2023.

In the course of a typical geoscientific research project, observational and analytical data from different scales and sources, of many different types and formats, are collected, and interpreted. While the number of observational and analytical methods and sizes of resultant datasets have dramatically increased in recent times, only a few tools exist to collect, process, store, share and compare various data in simple ways.  

QGis – an open-source geographic information system, originally developed to handle data from Earth’s surface – offers a wide range of tools that can also be employed at the microscale in studies of petrology and/or deformation history. 

We herein present a case study based on a gabbroic sample from the Central Cordillera in western Colombia, showing four generations of fractures, around and within which alteration assemblages attest to fluid inflow and metamorphism. We integrate data from scans of polished surfaces, polarized light microscopy, backscattered, forescattered, and scanning electron microscope images (BSE, FSE, SE), electron probe (EPMA) spot and map microanalyses, and electron backscatter diffraction (EBSD). The use of QGis allowed us to easily relate data from these different sources and consider them in the context of petrological computations made with XMapTools software (Lanari et al., 2014).

In the future, we hope to automatically integrate collected electron microscopic data into QGis and external control via Python interfaces, as is currently permitted by some manufacturers of SEMs. We also plan to integrate computational petrology via plugins. 

We think that this software tool is one of the most multi-functional currently available for harmonized, integrated data collection, processing, storing and sharing, and would like to share our experience with our colleagues so they can also employ it in thorough analysis of samples, and thus also acquire datasets that can be used for comparative studies by collaborating researchers.

How to cite: Albrecht, T.-J., Hawemann, F., and Toy, V.: Collection, processing, storage and sharing of petrological and microstructural data using QGis as a database., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1895, https://doi.org/10.5194/egusphere-egu23-1895, 2023.

As the planetary science community sets its sights on the Moon, the existence of an open-source, up-to-date, and user-friendly modeling tool for lunar rocks is critical to maximizing the scientific return of ongoing and upcoming lunar missions (e.g., Artemis, PRISM, CLPS). While the creation of new code from the ground up is an important aspect of modern computational petrology, here we advocate for the modernization of legacy code, the results of which dominate the literature and shape our current understanding of geologic processes across multiple scales. Modernization of legacy code is critical as it enables the community to put new model results in the context of modern consensus gentium. Here we discuss how modern best practices for code development, publishing, and maintenance should be applied to upgrading legacy code, using lunar petrologic models as an example. We highlight critical gaps in our ability to model lunar processes that could be filled simply with updated modeling tools (i.e., where underlying experimental and analytical data already exist but are not incorporated into existing modeling tools).

Current modeling tools developed specifically for lunar compositions are sparse and can contain outdated parameterizations. One critical knowledge gap is our ability to model silicic lunar magmas, which are evidenced in nature by felsic fragments in returned Apollo samples and silica-rich volcanic domes identified on the borders of lunar mare by remote sensing. The most popular tool for modeling lunar magmas is MAGPOX, born from a series of FORTRAN scripts and ported to MATLAB, which is underpinned by an exclusively basaltic database. MAGPOX requires the crystallization of olivine on the liquidus, and thus has limited application to the full compositional diversity of lunar magmas. rhyolite-MELTS has been used to model silicic magmatism on the Moon, but its use typically requires additional experimental work given that the MELTS database is biased towards terrestrial rocks with lower FeO, higher alkalis, and higher fO₂ than lunar rocks. Notably, the MELTS database includes the same published basaltic lunar rocks used in MAGPOX regressions and so should be trustworthy for silica-poor lunar magmas. Still, the adoption of MELTS by the lunar community requires extensive testing against MAGPOX, PERPLE_X, and large lunar experimental databases.

Before we can even begin to update the parameterizations underpinning MAGPOX or efficiently compare MAGPOX to other models, a modern code library is required to perform adequate testing and benchmarking. In this talk we will explore the state of lunar petrologic modeling, what can be done now, and how we can best bring it into the 21^st century.

How to cite: Iacovino, K. and Prissel, K.: Modeling lunar magmas in the Artemis Era, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2383, https://doi.org/10.5194/egusphere-egu23-2383, 2023.

The chemistry of erupted minerals and melts are commonly used to determine the pressures, temperatures and H₂O contents of magma storage regions beneath volcanic centres. In turn, these estimates are vital for hazard assessment, to understand the formation of critical metal deposits, and to inform models of continental crust formation. In the last few decades, more than 100 empirical and thermodynamic expressions have been calibrated using measurements of phases in experimental studies where these intensive parameters are known. By collating these different models into a computationally-efficient, open-source Python3 package, Thermobar, we can critically assess the performance of thermobarometers in igneous systems, and propagate analytical errors. When we apply published models for different mineral equilibrium to a new experimental dataset not used in model calibration, we find that stated errors vastly underestimate the true uncertainty when these workflows are applied to natural systems.

Specifically, we find that realistic calculation workflows involving Clinopyroxene (Cpx) equilibrium (e.g., iterating pressure and temperature) have uncertainties spanning the entire crust in most tectonic settings. Using Thermobar functions to propagate analytical error using Monte Carlo simulations, we suggest that these large errors result from imprecise analyses of minor elements such as Na in experimental (and natural) Cpx. Common analytical conditions used for Cpx yield highly correlated pressure-temperature arrays spanning the entire crust, which have been incorrectly interpreted as trancrustal storage in natural systems. Insuffucient analyses of each phase in experimental products means that this analytical error is not sufficiently mediated by averaging, so reported mineral compositions deviate from the true phase composition. This impacts thermobarometer calibration, as well as assessment of these methods using test experimental datasets.

Overall, we demonstrate that the development of Python3 infrastructure for common quantitative workflows in volcanology is vital to allow rigorous error assessment and model intercomparison; such assessments simply aren’t feasible using traditional tools (e.g., Excel workbooks). Specific changes to analytical, experimental and model calibration workflows (e.g., higher beam currents and count times in Na) will be essential to produce a more robust dataset to calibrate and test the next generation of more precise and accurate Cpx-based barometers. In turn, this will enable more rigorous investigation of magma storage geometries in a variety of tectonic settings (e.g., distinguishing true transcrustal storage vs. storage in discrete reservoirs).

How to cite: Wieser, P., Kent, A., Till, C., Petrelli, M., Wieser, E., Lubbers, J., Neave, D., Ozaydin, S., Donovan, J., Blatter, D., and Krawczynski, M.: Open-source Python3 tools for Thermobarometry: Revealing the good, the bad and the ugly of determining P-T-X conditions in igneous systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3926, https://doi.org/10.5194/egusphere-egu23-3926, 2023.

Here we introduce the AusGeochem platform enabling geoscientists to manage and publish sample based geoscience data in a consistent and FAIR way. 

The AusGeochem data platform has been built by the AuScope Geochemistry Network (AGN) and Lithodat Pty Ltd as part of a national digital infrastructure project to facilitate the sharing of data produced by geochemistry laboratories across Australia. 

In order to improve national geochemical facility data management, the AusGeochem platform uses detailed structured and standardized method specific data models for collating, preserving, and disseminating geochronology and isotopic data. 

AusGeochem provides researchers with a solution to record and utilize all of this information, while streamlining their workflow from collection to publication. Here we will give an overview of a typical sample workflow. 

The demonstrated workflow contains the following steps: Storing all sample details on-the-fly during sample collection with the field app. Managing the data by logging into the AusGeochem website. Adding subsequent geochemical analyses to the sample. Visualizing the data using analytic dashboards and graphs. Sharing the data with a team of collaborators. And finally, making the data referenceable by minting DOIs and IGSNs.

Manifold data is produced and captured along this process of collecting, analyzing and publishing. This is not confined to just the analytical results, but also a lot of meta information, such as involved people, instruments, funding sources, grant numbers, laboratories and institutions. Being rich in such metadata opens up the path to interesting new functionality, e.g. in the space of structured quantification and quality assessment of research projects.

The AusGeochem platform is of great help for a single researcher or a team of researchers by providing them with the means and tools to make their work more efficient and productive. However, the real benefit comes by having an access control layer, so data from multiple institutions can be  stored on one single platform. Since the data is now all stored in one detailed model, it gives researchers the possibility to apply analysis across data from all contributing institutions on the fly.  This means, no downloading of data from multiple sources required. And most importantly, no difficult and often impossible data preprocessing required.

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.

How to cite: Theile, M., Noble, W., Beucher, R., Bedoya-Mejia, A., Boone, S., and Kohlmann, F.: From Fieldwork to Publication with AusGeochem: An Open end-to-end Solution for managing FAIR Sample Based Geoscience Data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4954, https://doi.org/10.5194/egusphere-egu23-4954, 2023.

The phrase “automated mineralogy” has been synonymous with electron microscopy in the geosciences for decades. The use of energy dispersive spectroscopy (EDS) to rapidly map samples and identify phases of interest has gradually seen a shift out of its original industry applications and into the academic research environment. A major issue for academics wishing to take advantage of this powerful tool is the original platforms are rigid in terms of their industry designed outputs, and there has been a lack of development in both the software and hardware capable of providing automated outputs.

However, rather than just looking backwards at what automated mineralogy was originally designed for, there is a more forward looking and important conversation as geoscience projects increase in scope. To think about geoscience in the context of topics such as big data, statistical relevance, and the use of increasingly prevalent machine learning techniques, we need to think about how we collect and store data. This naturally requires a greater integration of the problems geoscientists are trying to address with the solutions that microscopy and microanalysis equipment suppliers provide. Greater access to the data acquired on scientific equipment not only provides greater research flexibility but opens much smarter routes towards a future of correlated datasets with minimal user input.

Using quantitative chemistry as the basis for automated mineralogy provides unique capabilities for large area analysis such as thin sections. Quantitative textural information can be extracted from the sample such as grain sizes, shapes, and mineral associations, alongside quantitative geochemical data providing mineral classification, including mineral and whole rock/sample compositions. This provides a wealth of information for the petrologist to understand their sample and a one-stop-shop for many geoscience workflows. This is a ready made mechanism to generate large datasets across multiple samples in a consistent fashion – the key to big data.

Here we show one example of greater integration of data acquisition with user generated computational software showing the power of large area quantitative EDS mapping with geoscience-oriented functions of XMapTools. By importing calibrated, quantitative EDS maps XMapTools can be used to rapidly perform a variety of petrological calculations without the need for a separate, long-winded calibration step using microprobe data. Here we use quantitative EDS from high grade metamorphic rocks to obtain mineral and bulk compositions alongside textural information such as modal abundances. These mapped data are imported directly into XMapTools and can be used to generate oxide values, cation per formula unit (cpfu), end member proportions, and perform thermodynamic calculations.

How to cite: Taylor, R.: Reimagining automated mineralogy for the 21st century, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7485, https://doi.org/10.5194/egusphere-egu23-7485, 2023.

In contrast to thermodynamic models for metamorphic mineral solutions, which often concern quartz-saturated assemblages, the phase equilibria of feldspars, feldspathoids and melilite in the K₂O-Na₂O-CaO-Al₂O₃-SiO₂-H₂O space are much less established. They provide basis for classification and interpretation of alkaline silica-undersaturated rocks and essential constraints for developing normative calculation and classification algorithms. The existing normative schemes (CIPW, Müller, Le Bas, Rittmann and Curie norms) do not provide satisfactory treatment of nepheline, leucite, clinopyroxene and melilite stabilities and equilibria. In many conventional schemes (1) anorthite persists to very low silica activities despite of its instability and incompatibility with melilite; (2) normative larnite is a principal indicator of melilite presence but provides a poor chemical proxy; (3) compatibilities between alkali feldspar, leucite and nepheline solid solutions are incorrectly predicted (e.g., leucite-albite, feldspar-melilite); (4) desilication steps do not uniquely follow decreasing activity of silica. As a consequence, the norms applied to alkaline silica-undersaturated igneous rocks do not provide unique or correct view of mineral assemblages and their chemographic relations. In this contribution we explore phase equilibria and compatibility relations in the system SiO₂-CaAl₂O₄-NaAlSiO₄-KAlSiO₄-H₂O. We have adopted the thermodynamic models for nepheline, leucite and kalsilite solutions (Sack & Ghiorso 1998). The order-disorder models have been converted to the relevant sets of linearly independent end-members including ordered or anti-ordered intermediate members with macroscopic Margules parameters. These models were designed as transferable between Berman, Holland-Powell or other end-member datasets. In the composition space SiO₂-NaAlSiO₄-KAlSiO₄ at P = 1 bar and T = 1000 ^oC, alkali feldspar is compatible with nepheline or leucite, separated by an invariant composition Or₅₁Ab₄₉. Consequently, sodic rocks, with molar Na/(Na+K) > 0.75, contain the anorthoclase + nepheline assemblage, whereas with increasingly potassic character, the rocks contain leucite + nepheline, leucite + tetrakalsilite or leucite + kalsilite; the SiO₂-richer assemblages consist of leucite + sanidine. With decreasing temperature, tetrakalsilite becomes unstable and is replaced by K-bearing nepheline + kalsilite. Furthermore, the invariant feldspar composition separating the nepheline vs. leucite assemblages rapidly migrates towards sanidine (Or₉₀Ab₁₀ at 800 ^oC and 1 bar). As a consequence, decreasing crystallization temperature favors the assemblage of alkali feldspar and nepheline (over leucite) for a wide range of bulk Na/(Na+K) ratios. This explains the rarity of sodic feldspar + leucite assemblages in nature. At feldspar subsolvus temperatures, both albite and orthoclase coexist with nepheline, and leucite becomes Na-poor and eventually breaks down to kalsilite and orthoclase. This is consistent with frequent replacement in nature of leucite by secondary products, in particular analcime. The compatibility relations in the SiO₂-NaAlSiO₄-KAlSiO₄ system are conveniently delineated by several intermediate members, e.g., Or₇₅Ab₂₅ or Ne₆₀Ks₄₀, which are used in a new algorithm for normative classification and interpretation of alkaline undersaturated rocks.

References

Sack R.O., Ghiorso M.S., 1998. Contrib. Mineral. Petrol. 130, 256-274.

How to cite: Dolejš, D.: Magmatic equilibria between feldspathoids and feldspars: Implementation of thermodynamic models and implications for norm calculation and petrographic interpretation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9700, https://doi.org/10.5194/egusphere-egu23-9700, 2023.

Fluid-rock interactions are one of the most important processes on Earth and play an important role in many metamorphic systems, especially during fluid migration. Research during the past three decades have provided many new software and thermodynamic databases for both mineral and fluids. Yet, in the metamorphic community, the fluid phase is usually modelled using molecular fluids such as pure H₂O or  H₂O-CO₂ mixtures. This may be a limiting factor since aqueous fluids containing dissolved ionic species are involved leading to metasomatic reactions. The Deep Earth Water (DEW) model allows modeling complex fluid-rock interactions involving ionic species at pressure and temperature conditions up to 6 GPa and 1200 °C ¹. However, its use through software packages such as EQ3/6 ² may be time-consuming.

ThermotopesC_DEW is a Python application with a user-friendly graphical user interface (GUI) that allows automation of thermodynamic computations with the EQ3/6-DEW software package. The application uses the capability of the EQ3 and EQ6 to compute the chemical speciation of a fluid in equilibrium with a user-defined mineral assemblage, and the reaction of this fluid with a new rock, respectively. ThermotopesC_DEW allows the user to compute batches of EQ6 calculations with different fluid-rock ratios set by the user, or to batch process EQ6 computations with different proportions for 3 minerals within a ternary diagram, for a given fluid-rock ratio. The application then allows the user to create customized plots of the computation results in 2D and 3D, for each option and for each variable.

In this contribution, we explore the capabilities of ThermotopesC_DEW to investigate fluid-peridotite interactions at subduction zone pressure and temperature conditions, for over 30 000 individual EQ6 runs. Different fluid compositions, reacting assemblages, and fluid-rock ratios were considered.

Over the wide range of conditions of these runs, modes of hydrous phases, relative proportions of the different phases, pH and log f_O2 vary widely, highlighting the complexity of fluid-rock interaction processes in the subduction zone and warrant the use of simple fluid formulation to model such processes. We believe that user-friendly applications such as the one presented here will allow more petrologists to introduce fluid speciation into their metamorphic projects.

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

2. Wolery, T. J. EQ3/6, a software package for geochemical modeling of aqueous systems: Package overview and installation guide (Version 7.0). doi:10.2172/138894.

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: Siron, G., Vitale-Brovarone, A., and Matthews, S.: ThermotopesC_DEW, a Python GUI application to automate thermodynamic computations for fluid-rock interactions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12522, https://doi.org/10.5194/egusphere-egu23-12522, 2023.

Stream sediment geochemistry is a useful tool to derive geochemical insights into local geological units within stream sediment source areas. This has significant applicability within the field of mineral exploration where understanding regional geochemistry is fundamental to successful prospection and can facilitate the identification of critical metal deposits. This can help diversify the supply chain of critical metals, as well as tackle the deficit, especially for cobalt (Co). Cobalt is a growing component in many industrial processes but is mostly required for powering Li-Co batteries in Plug-in Hybrid Electric Vehicles (PHEV)¹. Demand for Co is growing exponentially in order to meet future carbon-neutral technological demand as part of joint UK-European initiatives towards a more environmentally sustainable society. 

The UK Geochemical Baseline Survey of the Environment (G-BASE) dataset is used to demonstrate that this technique provides a useful tool for isolating potential ‘Critical Minerals’² in host rocks across the UK Lake District, with priority targeting towards Co-bearing ores. We reduced the dimensionality of the G-BASE stream sediment data to create geochemical maps that identify a combination of volcanic, sedimentary, and plutonic lithologies lining up geological boundaries from established 50k scale geological maps of the area. This was conducted through a combined statistical and mapping approach within QGIS and ioGAS. The resultant lithogeochemical map of the region highlights the average geochemistry for each major lithological group with varying degrees of resolution.

This technique also allows for the identification of average ore metal concentrations (Ag, As, Bi, Co, Cu, Mo, Ni, Sn, Zn) for the Skiddaw Group and the Borrowdale Volcanic Group, two established host groups for As-Co-Cu-Ni mineralisation. Average concentrations of Co in the Skiddaw have been modelled to be 63.26 ppm, and in the Borrowdale volcanics to be 26.86 ppm. These values, combined with As, Cu, and Ni modelled concentrations, and other publicly available exploration-related data (structural maps, underlying batholith topography, mining history, mineral occurrences etc.) allowed us to identify 10 prospective areas of interest for possible As-Co-Cu-Ni mineralisation across these two lithological groups. Fieldwork was then undertaken to investigate several of these identified areas in order to establish the success of the model targeting tools. Ore metal-bearing minerals, mostly Cu-Fe-As phases, were identified both disseminated in local shales and andesites, and in hydrothermal quartz-chlorite veins at six sites investigated thus far. Characterisation of these minerals and host rocks is still in progress, making use of SEM-EDS and XRF analytics.

We demonstrate this workflow has strong applicability within critical metal exploration and should be applied in other, more prospective regions across the globe. The only pre-requisite to the mapping is the availability of stream sediment databases with sufficient resolution across target areas.

¹ Dehaine et al. 2021. BATCircle Project Report 04.
² Resilience for the Future: The UK’s critical minerals strategy, policy paper, 22^nd July 2022.

How to cite: Eskdale, A., Gough, A., and Johnson, S.: The applicability of stream sediment geochemistry as a combined geological mapping, and prospective exploration tool for As-Co-Cu-Ni mineralisation., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13447, https://doi.org/10.5194/egusphere-egu23-13447, 2023.

Explorations of mineral compositions aiming to reveal complex magmatic processes in melts have proliferated with the growing accessibility of geochemical datasets through databases including PetDB, LEPR/TraceDs, and GEOROC and of computational methods. The generation and continuous quality assurance of mineral data in these databases requires significant human intervention and individual post-processing. One major problem is that minerals may be misclassified (i.e., a compiled dataset of clinopyroxenes may contain some amphiboles), and compilations may contain poor-quality electron microprobe (EPMA) analyses (with low totals, low cation sums, or poor correspondence to the theoretical stoichiometry of a mineral phase). At the moment, individual studies compiling geochemical datasets for specific tectonic settings [1] or calibrating thermobarometers based on mineral-melt equilibrium [2] tend to apply their own filters. With a push for a more consistent approach, we create a new open-source Python package called MIN-ML (MINeral classification using Machine Learning) for classifying common igneous minerals based on oxide data collected by EPMA, with functions for calculating stoichiometries and crystallographic sites based on this classification. Utilizing this package allows for the identification of misclassified mineral phases and poor-quality data. We streamline data processing and cleaning to allow for the rapid transition to usable data, improving the utility of data curated in these databases and furthering computing and modeling capabilities. 

While mineral identification and classification are obviously critical to the success of computational methodologies and machine learning (ML) applied to these large datasets, the question of how to best classify minerals from EPMA analyses comes to the fore. We approach this question by exploring and developing ML workflows, both supervised (classification algorithms) and unsupervised (dimensionality reduction and clustering). Unsupervised methods including autoencoders, a type of artificial neural network, present the opportunity to classify minerals with little a priori information. Autoencoders pair two neural networks with an encoder, compressing input data to a dimensionality-reduced latent representation, and a decoder, expanding latent representations to reconstruct the input and minimize loss. We present a novel autoencoder model aimed at meaningfully representing EPMA analyses of minerals in latent space, investigating the relationships between mineral phases, and performing classifications of these minerals. The model is trained with newly compiled datasets of twelve igneous mineral phases on thousands to tens of thousands of analyses per phase – across tectonic settings to train these ML models. The autoencoder is applied to datasets of mineral analyses from PetDB, LEPR, and GEOROC to evaluate model performance and show significant improvements in mineral phase segregation and classification, critical to rigorous dataset quality control and future integration into data processing routines. 

[1] Gale, A., et al., The mean composition of ocean ridge basalts. Geochemistry, Geophysics, Geosystems 14, 489-518 (2013).

[2] Petrelli, M., et al., Machine learning thermobarometry: Application to clinopyroxene-bearing magmas. JGR: Solid Earth 125, e2020JB020130 (2020).

[3] Lehnert, K. A., et al., 2022, IEDA2: Evolving EarthChem, LEPR/TraceDs, and SESAR into a Next Generation Data Infrastructure for Data-Driven Research Paradigms in Geochemistry, Petrology, and Volcanology, in 2022 Goldschmidt Conference.

How to cite: Shi, S., Wieser, P., Lehnert, K., and Profeta, L.: MIN-ML: A Machine Learning Framework for Exploring Mineral Relations and Classifying Common Igneous Minerals, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13612, https://doi.org/10.5194/egusphere-egu23-13612, 2023.

Despite the outstanding progress in computer technology and experimental facilities, understanding melting processes and solid-melt phase equilibria at planetary conditions is still an open challenge. In this work a modern computational approach to predict melting phase relations at HP-HT by a combination of first principles DFT and MD calculations, polymer chemistry and equilibrium thermodynamics is presented and discussed. The adopted theoretical framework is physically-consistent and allows to compute multi-component phase diagrams relevant to planetary interiors in a broad range of P-T conditions by a convex-hull algorithm based on the simplex method for Gibbs free energy minimisation. The calculated phase diagrams are in turn used as a source of information to gain new insights on both present-day and early Earth melting processes. Some examples of application of the above method to the CaO-MgO-Al₂O₃-SiO₂ system (CMAS) and relevant ternary and binary subsystems highlights as pressure effects are not only able to change the nature of melting of some minerals (like olivine and pyroxene) from eutectic to peritectic (and vice versa), but also simplify melting relations by drastically reducing the number of phases with a primary phase field at HP-HT conditions. Since the volume-pressure integral contribution to Gibbs free energy become relevant at planetary interior conditions, special attention must be paid to the choice of the P-V-T EoS formalism in order to avoid physical unsoundness or spurious effects in thermodynamic properties (e.g. negative thermal expansion). Ab initio-assisted computational thermodynamics is thus outlined as the main route towards the future development of physically-consistent (besides internally-consistent) thermodynamic databases for global-scale planetary investigations.

Financial support by the Italian Ministry of University and Research (MIUR PRIN 2017, Project 2017KY5ZX8 and MIUR PRIN 2020, Project 202037YPCZ) is warmly acknowledged.   

How to cite: Belmonte, D., La Fortezza, M., and Menescardi, F.: Ab initio-assisted computational thermodynamics: a modern approach to phase diagram calculation at planetary conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14346, https://doi.org/10.5194/egusphere-egu23-14346, 2023.

Fluid release from hydrated oceanic lithosphere in subduction zones is a key process in the deep earth water cycle. During prograde metamorphism a channelized vein network forms in the dehydrating rock that allows efficient fluid release from the slab into the mantle wedge. The formation of such a vein network is a multiscale process that occurs over a wide range of time and length scales. Previous studies as well as field observations of exhumed meta-serpentinites suggest that the processes governing rock dehydration shift from chemical to mechanical processes going from small to large scales.

To investigate the behavior of a dehydrating slab over this wide range of scales we present a multiscale dataset that includes field-based observations from m to sub-µm scale of a representative serpentinite from the Mirdita ophiolite (Albania). This ophiolite has experienced seafloor alteration, but has not been metamorphosed at conditions that would cause any dehydration. We use these data as input for thermodynamic equilibrium calculations to investigate the effect of chemical heterogeneities in the bulk rock composition while the PT-conditions will be increased following a typical subduction zone geothermal gradient.

For upscaling we perform the calculations at various effective thermodynamic domain sizes (20-100 µm), showing that anisotropic chemical heterogeneities lead to heterogeneous porosity formation on all scales. Bloch et al. (2018) found that for vein-like porosity structures the percolation threshold of an effective bulk media may be reached at a porosity as low as 10^-3. Therefore, the anisotropic porosity structure formed by chemical heterogeneities leads to a high connectivity even at low porosities and thus allows efficient fluid flow. Accordingly, going to even larger scales we can use these findings to describe the lithologies found in the field as effective bulk media with an effective fluid flow. This allows us to investigate fluid release from the dehydrating slab on the km-scale by reactive porosity waves using a numerical model.

Bloch, W., John, T., Kummerow, J., Salazar, P., Krüger, O. S., & Shapiro, S. A. (2018). Watching Dehydration: Seismic Indication for Transient Fluid Pathways in the Oceanic Mantle of the Subducting Nazca Slab. Geochemistry, Geophysics, Geosystems, 19(9), 3189–3207. https://doi.org/10.1029/2018GC007703

How to cite: Huber, K., Vrijmoed, J. C., and John, T.: Serpentinite dehydration as a multiscale process, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14500, https://doi.org/10.5194/egusphere-egu23-14500, 2023.

Understanding earth materials is essential for the creation of 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. 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. Besides society-relevant topics, the properties of earth materials determine how the Earth works on the most fundamental level.
To overcome this challenge, 15 European institutes joined forces to establish EXCITE, providing free-of-charge access to 24 state-of-the art microscopy and x-ray tomography facilities in Europe. EXCITE can help you gain insight into the processes governing the behavior of the Earth crust through microchemical analyses and 2D- to 4D imaging, and down to nanometer resolution. 
In particular, the EXCITE strategy integrates joint research programs with networking, training, and trans-national access activities, thereby enabling both academia and industry to answer critical questions in earth-materials science and technology. 
EXCITE is building 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.

EXCITE is building 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.

Access to EXCITE can be requested by applying to our bi-annual call. Interested? Have a look on the EXCITE website (https://excite-network.eu) – and apply!

How to cite: ter Maat, G., Walter, S., Cnudde, V., Wessels, R., and Plümper, O.: Access to EXCITE: A European infrastructure to promote electron and X-ray microscopy of earth materials, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15470, https://doi.org/10.5194/egusphere-egu23-15470, 2023.

The texture and morphology of igneous zircon indicates magmatic conditions during zircon crystallisation and can be used to constrain provenance. Zircons from porphyry copper deposits are typically prismatic, euhedral and strongly oscillatory zoned which may differentiate them from zircons associated with unmineralised igneous systems. Here, cathodoluminesence images of zircons from the Quellaveco porphyry copper district, Southern Peru, were collected to compare zircon textures between the unmineralised Yarabamba Batholith and the Quellaveco porphyry copper deposit. Quellaveco porphyry zircons are prismatic, euhedral and strongly oscillatory zoned, whereas the batholith zircons contain more variable morphologies and zoning patterns. We adopt a deep convolutional neural networks (CNNs) approach to demonstrate that a machine can classify porphyry zircons with a high success rate. We trial several existing CNN architectures to classify zircon images: LeNet-5, AlexNet and VGG, including a transfer learning approach where we used the weights of a VGG model pre-trained on the ImageNet dataset. The VGG model with transfer learning is the most effective approach, with accuracy and ROC-AUC scores of 0.86 and 0.93, indicating that a Quellaveco porphyry zircon CL image can be ranked higher than a batholith zircon with 93% probability. Visualising model layer outputs demonstrates that the CNN models can recognise crystal edges, zoning and mineral inclusions. We trial implementing trained CNN models as unsupervised feature extractors, which can empirically quantify crystal textures and morphology. Therefore, deep learning provides a powerful tool for the extraction of petrographic information from minerals which can be applied to constrain provenance in detrital studies.

How to cite: Nathwani, C., Wilkinson, J., Brownscombe, W., and John, C.: Mineral texture classification using deep convolutional neural networks: an application to zircons from porphyry copper deposits, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16579, https://doi.org/10.5194/egusphere-egu23-16579, 2023.

The Altaids, or the Central Asian Orogenic Belts, is generally considered to be the largest Phanerozoic accretionary orogen on Earth, but it is unclear if it was associated with extensive continental crustal growth and whether there is a link between the crustal growth and ore mineralization. This study, based on 5507 whole-rock Nd and 39514 (2443 samples) zircon Hf isotope data of felsic-intermediate-mafic igneous rocks as well as associated 1830 ore deposit data for the Altaids, presents Nd + Hf isotopic contour maps for this region. The maps highlight the three-dimensional (3D) lithospheric compositional architecture of the Altaids and make it possible to quantitatively evaluate the crustal growth and its relationship to ore deposits. The Altaids hosts ~4,107,350 km² and ~184,830,750 km³ (assuming a crustal thickness of 40-50 km) juvenile crust (ε_Nd(t) > 0), accounting for 58% by isotope-mapped area (~7,010,375 km²) of almost all outcrops of the Altaids (~8,745,000 km²) and formed during 1000–150 Ma (mainly 600–150 Ma). Therefore, the Altaids can be viewed as the largest storage area and most typical "fossils" of the juvenile crust in orogens worldwide. Our results are applicable to other types of orogens, particularly to the final continental collision and its control on mineralization. The juvenile crustal, slightly juvenile-reworked crustal, and slightly reworked crustal provinces controlled the Cu-Au, the Pb-Zn-Ag, and the Li-Be, Nb-Ta, and W-Sn ore deposits. According to the crustal architecture and background of deep compositions, we propose that the ore deposits can be grouped into three types: juvenile crust-related, mixed source (or slightly juvenile crust)-related, and reworked crust-related. This highlights the close relationship between accretion, continental growth, and mineralization and will facilitate exploration for specific ore deposit types in the Altaids.

How to cite: Wang, T., Huang, H., Zhang, J., Wang, C., Cao, G., Xiao, W., Yuan, L., Tong, Y., and Guo, L.: Nd-Hf isotopic mapping based on a large archive of age data reveals voluminous continental growth of the Altaids and its control on metallogeny, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17556, https://doi.org/10.5194/egusphere-egu23-17556, 2023.

Geomorphological mapping is one of the primary research methods used to collect data on glacial landforms and reconstruct glaciological processes. The most common approach is a combination of field-based and remote mapping using data obtained from various sensors. However, one of the crucial methodical problems is collecting remote sensing data in the appropriate spatial resolution for the analyzed landform, which directly affects the data collection time and costs. This study aims to find the optimal resolution of digital elevation models (DEMs) to map subtle glacial landforms: kame terraces, eskers, flutes, and push moraine. Such landforms contain valuable information about the glacial process–form relationships, however, are often too subtle to be recognized on satellite data, and therefore more detailed data (e.g., UAV-based) are required. By “optimal”, we mean the resolution high enough to enable recognition of the landforms mentioned above, and at the same time, as low as possible to minimize the time spent on data collection during the fieldwork.

To find out the optimal resolution, we used detailed (0.02 – 0.04 m ground sampling distance [GSD]) DEMs of the glacier forelands in Iceland (Kvíárjökull, Fjallsjökull and Svinafellsjökull), created based high-resolution images from an unmanned aerial vehicle (UAV). The DEMs were resampled to 0.05, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 1.00 and 2.00 m GSD and selected glacial landforms were mapped independently by two operators and cross-checked. The results indicate that 2.0 m resolution is insufficient to properly recognize landforms such as pushed moraines or flutes; however, it can be sufficient to detect kame terraces and major glacifluvial channels. For general mapping of locations of forms such as annual pushed moraines or fluting, the 0.5 m resolution is required. However, to obtain geomorphometric characteristics of the landforms (e.g., height, width, volume) resolution between 0.1 and 0.2 m is necessary. Finer resolution (better than 0.05 m GSD) does not increase the ability to detect landforms or better characterize their geometric properties; however, in some cases might be useful to obtain information about clast characteristics. The experiment proved that decimeter-scale spatial resolution is sufficient for mapping of some geomorphological forms (annual pushed moraines, flutes), which allows for planning UAV missions at a higher elevation above the ground and, therefore, minmizing the duration of field surveys. Moreover, some of the more prominent landforms (e.g., kame terraces, larger moraines) can be successfully detected from aerial or satellite-based DEMs (e.g. freely available ArcticDEM) with a resolution of 2.00 m, the use of which reduces the costs of field research to a minimum.

This research was funded by the National Science Centre, Poland, Grant Number 2019/35/B/ST10/03928.

How to cite: Śledź, S. and Ewertowski, M.: Optimal resolution of UAV-based digital elevation models (DEMs) for mapping of selected subtle glacial landforms, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-151, https://doi.org/10.5194/egusphere-egu23-151, 2023.

Anomalous CO₂ degassing of volcanic origin was observed by the end of November 2021 in the neighborhoods of La Bombilla and Puerto Naos, located in the western flank of La Palma, about 5 km distance southwestern of the 2021 Tajogaite eruption vents (Hernández et al., 2021). In this study zone, continuous monitoring of CO₂ concentration in the outdoors ambient air at 200 cm from the surface has reached a daily average of maximum and mean values about 28,000 and 10,000 ppm, respectively. We started recently to perform CO₂ concentration and stable isotope surveys in the outdoors ambient air of Puerto Naos at 140 cm from the surface by means of a Delta Ray analyzer installed in an electrical car which was driving through the streets of Puerto Naos. This instrument is a high performance, mid-infrared laser-based, isotope ratio infrared spectrometer (IRIS) which offers the possibility of performing simultaneous determination of δ¹³C and δ¹⁸O in CO₂ at ambient concentrations with a precision as low as 0.05‰. One major advantage of IRIS techniques with respect to more traditional ones (e.g., isotopic ratio mass spectrometry -IRMS-) is the possibility to perform (semi)continuous measurements at high temporal resolution. Since October 2022, seven surveys have been performed at Puerto Naos making up a total of about 600 measurements. The observed CO₂ concentrations and the δ¹³C-CO₂ values in the outdoors ambient air ranged from 420 to 3,500 ppm and from -9.0 to -3.2 ‰ vs. VPDB, respectively. Survey data analysis showed a good spatial correlation between relatively high CO₂ concentrations with δ¹³C-CO₂ values less ¹³C-depleted (i.e., volcanic CO₂). These observations highlight that stable isotope surveys allow to evaluate the impact of volcanic degassing on the air CO₂ concentration and provide valuable results to identify the volcanic CO₂ gas hazard zones.

Hernández, P. A., Padrón, E., Melián, G. V., Pérez, N. M., Padilla, G., Asensio-Ramos, M., Di Nardo, D., Barrancos, J., Pacheco, J. M., and Smit, M.: Gas hazard assessment at Puerto Naos and La Bombilla inhabited areas, Cumbre Vieja volcano, La Palma, Canary Islands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7705, https://doi.org/10.5194/egusphere-egu22-7705, 2022.

How to cite: Pérez, N. M., Asensio-Ramos, M., Barrancos, J., Padrón, E., Melián, G. V., Rodríguez, F., Padilla, G. D., Albertos, V. T., Hernández, P. A., Álvarez Díaz, A. J., de los Ríos Díaz, H., Afonso Falcón, D., and Cutillas, J.: CO2 concentration and stable isotope surveys in the ambient air of populated areas of La Palma (Canary Islands) by means of mobile Delta Ray measurements using an electrical car, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3292, https://doi.org/10.5194/egusphere-egu23-3292, 2023.

Throughout the 85 days that lasted the Tajogaite eruption at Cumbre Vieja volcano (La Palma, Canary Islands, Spain), observations of SO₂ emissions were made using ground-based instruments, in transverse mode, static scanners and on-board drones, as well as by numerous satellite instruments. The initial estimates of the total SO₂ emission from the eruption were 2.4 Mt from TROPOMI and 1.2 Mt from the traverse data. These measurements formed part of the official monitoring effort, providing insights into the eruption’s evolution and informing the civil defence response throughout the eruption (Hayer C. et al., 2022; Albertos V. T. et al., 2022). Once the Tajogaite eruption was over, we continued performing a SO₂ monitoring release to the atmosphere by the Tajogaite volcanic vent since the low ambient concentrations of SO₂ make it an ideal volcanic gas monitoring candidate even during the post-eruptive phase. SO₂ measurements had been carried out a using a car-mounted and UAV-mounted ground-based miniDOAS measurements throughout this post-eruptive phase. About 80 measurements of SO₂ emission rates were performed from December 15, 2021 to December 17, 2022. The standard deviation of the estimated values obtained daily was ~ 20%. The range of estimated SO₂ emission values has been from 670 to 17 tons per day, observing a clear decreasing trend of SO₂ emissions during the post-eruptive phase. During the first month of the post-eruptive phase, it was observed that the average value of the estimated SO₂ emission was about 219 tons/day, while it dropped to 107 tons/day during the second and third month after the end of the Tajogaite eruption. This average value continued decreasing during the fourth month of the post-eruptive phase, about 67 tons/day, and recently measurements provide an average SO₂ emission value of 13 tons/day. These relatively low observed SO₂ emissions during the post eruptive of the Tajogaite eruption phase seems to be clearly related to shallow magma cooling processes within the Tajogaite volcanic edificie.

Hayer, C., Barrancos, J., Burton, M., Rodríguez, F., Esse, B., Hernández, P., Melián, G., Padrón, E., Asensio-Ramos, M., and Pérez, N.: From up above to down below: Comparison of satellite- and ground-based observations of SO₂ emissions from the 2021 eruption of Cumbre Vieja, La Palma, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12201, https://doi.org/10.5194/egusphere-egu22-12201, 2022.

Albertos, V. T., Recio, G., Alonso, M., Amonte, C., Rodríguez, F., Rodríguez, C., Pitti, L., Leal, V., Cervigón, G., González, J., Przeor, M., Santana-León, J. M., Barrancos, J., Hernández, P. A., Padilla, G. D., Melián, G. V., Padrón, E., Asensio-Ramos, M., and Pérez, N. M.: Sulphur dioxide (SO₂) emissions by means of miniDOAS measurements during the 2021 eruption of Cumbre Vieja volcano, La Palma, Canary Islands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5603, https://doi.org/10.5194/egusphere-egu22-5603, 2022.

How to cite: Rodríguez, O., Barrancos, J., Cutillas, J., Ortega, V., Hernández, P. A., Cabrera, I., and Pérez, N. M.: SO2 emissions during the post-eruptive phase of the Tajogaite eruption (La Palma, Canary Islands) by means of ground-based miniDOAS measurements in transverse mode using a car and UAV, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3620, https://doi.org/10.5194/egusphere-egu23-3620, 2023.

Carbon dioxide (CO₂) is a colourless and odourless gas. It is non-flammable, chemically non-reactive and 1.5 times as heavy as air; therefore, may accumulate at low elevations. CO₂ is a toxic gas at high concentration, as well as an asphyxiant gas (due to reduction in oxygen). Irritation of the eyes, nose and throat occurs only at high concentrations. Since the Tajogaite eruption ended on December 13, 2021, high concentrations of CO₂ up to 20% (200.000 ppmv) have been observed inside of buildings of the neighborhoods of La Bombilla and Puerto Naos (La Palma, Canary Islands), which are located about 5 km distance from the Tajogaite eruption vent. Anomalous concentrations of CO₂ are manily detected in the ground-floor and basement of the buildings in Puerto Naos, and the distribution of relatively high CO₂ concentrations  is not homogeneous or uniform throughout the Puerto Naos area (Hernández P.A. et al, 2022).

The purpose of this study was to use the Tunable Laser Diode (TDL) absorption spectroscopy method to monitor the indoor CO₂ concentration of the ground-floor of one of the buildings of Puerto Naos. A CO₂-TDL was installed on 9 January 2022 and continues measuring the CO₂ concentration along an optical path of about 6 meters. During the period January-March 2022, daily averages of CO₂ concentrations from fifteen-minute data ranged from 5000 to 25000 ppmv reaching values up to 40000 ppmv (4%). Over time, a clear decreasing trend of the indoor CO₂ concentration has been observed at this observation site and the daily CO₂ averages from fifteen-minute data during the last 3 months (October-December 2022) ranged from 1000 to 2500 ppmv. This clear decreasing trend over time has not been observed at other observation sites where the concentration of CO₂ inside buildings is being monitored. This observation indicates the complexity of the problem and the need to install a dense network of sensors to monitor CO₂ for civil protection purposes.

Hernández, P. A., Padrón, E., Melián, G. V., Pérez, N. M., Padilla, G., Asensio-Ramos, M., Di Nardo, D., Barrancos, J., Pacheco, J. M., and Smit, M.: Gas hazard assessment at Puerto Naos and La Bombilla inhabited areas, Cumbre Vieja volcano, La Palma, Canary Islands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7705, https://doi.org/10.5194/egusphere-egu22-7705, 2022.

How to cite: Barrancos, J., Padilla, G. D., Melián, G. V., Rodríguez, F., Asensio-Ramos, M., Padrón, E., Hernández, P. A., Vilches Sarasate, J., and Pérez, N. M.: Using tunable diode laser (TDL) system in urban environments to measure anomalous CO2 concentrations: the case of Puerto Naos, La Palma, Canary Islands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3819, https://doi.org/10.5194/egusphere-egu23-3819, 2023.

The 2021 Tajogaite eruption in Cumbre Vieja volcano (La Palma, Canary Islands), which started on Sep. 19, 2021, and lasted 85 days, caused extensive damages because of the lava flows and ash fall. However, since the middle of Nov. 2021, some areas located about 5 km SW of the eruptive center started to be affected by intense diffuse CO₂ emission. Among them are the urban centers of La Bombilla and Puerto Naos (Hernández et al., 2022). These emissions prevented the population of these two centers from returning to their houses because of high  concentrations of CO₂ in indoor and outdoor environments.

In this work, we model the CO₂ dispersion process in Puerto Naos to obtain hazard maps with the maximum CO₂ concentrations which can be reached in the town in the outdoor environment. To achieve these results, we combined field observations with numerical modelling. Field surveys were realized in low wind conditions, measuring the CO₂ concentration with portable sensors  at 15 and 150 cm from the ground at measurement points spaced approximately 10 m from each other along the streets of Puerto Naos.

We realized numerical modelling using the software TWODEE-2, a code for modeling the dispersion of heavy gases based on the solution of shallow water equations (Folch et al., 2009). For this purpose, we used a detailed digital topographic model, including the edifices of Puerto Naos. Using a trial-and-error approach, we determined the gas emission rates from a set of discrete source points in no-wind conditions. Subsequently, we repeated the numerical modelling, keeping the same sources and simulating all the realistic wind conditions in terms of direction and intensity. For each simulation, we determined the maximum CO₂ concentration at different elevations from the ground. This allowed obtaining a hazard map with the maximum CO₂ outdoor concentrations for each part of the town

The main results highlight that the outdoor environment is affected by a dense layer of CO₂, whose flow is strongly conditioned by the urban infrastructures. Furthermore, we evidenced how even light winds can change the gas concentration pattern radically in a few minutes, evidencing the possibility of sudden changes in the CO₂ concentration outdoors with no warning.

Folch A., Costa A., Hankin R.K.S., 2009. TWODEE-2: A shallow layer model for dense gas dispersion on complex topography, Comput. Geosci., doi:10.1016/j.cageo.2007.12.017

Hernández, P. A., Padrón, E., Melián, G. V., Pérez, N. M., Padilla, G., Asensio-Ramos, M., Di Nardo, D., Barrancos, J., Pacheco, J. M., and Smit, M.: Gas hazard assessment at Puerto Naos and La Bombilla inhabited areas, Cumbre Vieja volcano, La Palma, Canary Islands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7705, https://doi.org/10.5194/egusphere-egu22-7705, 2022.

How to cite: D Auria, L., Santos, A., Hernández, P. A., Melián, G. V., Álvarez Díaz, A. J., Asensio-Ramos, M., González Pérez, A. M., and Pérez, N. M.: Modeling outdoor dispersion of CO2 at Puerto Naos (La Palma, Canary Islands), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3834, https://doi.org/10.5194/egusphere-egu23-3834, 2023.

The novel observing system „Modular Observation Solutions for Earth Systems (MOSES)“, is an initiative of the Helmholtz Association of German Research Centers that aims at investigating the interactions of short-term events and long-term trends across environmental systems. MOSES is a mobile and modular infrastructure and its component measuring systems are managed by the participating research centers. By quantifying energy, water, nutrient and greenhouse gas states and fluxes during events such as heat waves, droughts, heavy precipitation, floods, rapid thaw of permafrost or of ocean eddies, and subsequently along the related event chains, the system delivers data to examine potential long-term impacts of these events and to gain a better understanding of extreme events that are expected to increase in frequency and intensity in a changing climate. In order to obtain comprehensive data sets, a cross-system approach is followed, covering the atmosphere, land surface and hydrosphere. These event-related data sets complement long-term and/or large scale data sets of established national and international monitoring programs and satellite data such as TERENO, ICOS, eLTER, SENTINEL, etc. After a 5-year setup period, MOSES was successfully put into operation in 2022 (Weber et al., 2022, https://doi.org/10.1175/BAMS-D-20-0158.1).

While long-term trends are typically assessed with stationary observation networks and platforms specifically designed for long-term monitoring, proven event-oriented observation systems and strategies are still missing. Event-oriented observation campaigns require a combination of a) measuring systems that can be rapidly deployed at “hot spots” and in “hot moments”, b) mobile equipment to monitor spatial dynamics in high-resolution, c) in situ measuring systems to record temporal dynamics in high-resolution, and d) interoperable measuring systems to monitor the interactions between atmosphere, land surface and hydrosphere. We will present the observation system and the observing strategy on examples from two past test campaigns: 1) The “Swabian MOSES campaign” of 2021 that captured the formation and evolution of supercells, hail and heavy precipitation and the resulting local flash floods (Kunz et al., 2022, https://doi.org/10.3389/feart.2022.999593). 2) The MOSES campaign of 2019 that captured the historical low flow situation along the Elbe River and into the German Bight (e.g., Kamjunke et al., 2021, https://doi.org/10.1002/lno.11778). As an outlook, upcoming national and international campaigns and potential future deployments will be presented.

How to cite: Weber, U. and Schuetze, C. and the MOSES-Team: Event-oriented observation across scales and environmental systems: MOSES started operation., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5223, https://doi.org/10.5194/egusphere-egu23-5223, 2023.

The Tsagaan-uul area of the Khatanbulag ancient massif in the Central Asian Orogenic Belt is located in the southern part of Mongolia, which belongs to the Gobi Desert. It has a low vegetation cover, and because of this, remotely sensed data can be used without difficulty for geological investigations. Factors such as sparse population and underdeveloped infrastructure in the region further create a need for combining traditional geological mapping with remote sensing technologies. In existing geology maps of the area, the formations are lithologically very diverse and their boundaries were mapped variously, so a need for a more precise lithology-based map arouse.

This study investigated combinations of fieldwork, multispectral data, and petrography for the rock type classification. A random forest classification method using multispectral Sentinel-2A data was employed in order to distinguish different rocks within Proterozoic Khulstai (NP₁hl) metamorphic complex, which is dominated by gneiss, andesite, sandstone, limestone, amphibolite, as well as the Silurian terrigenous-carbonate Khukh morit (S₁hm) formation, Tsagaan-uul area. Based on the ground samples collected from field surveys, ten kinds of rock units plus Quaternary sediments were chosen as training areas. In addition, morphometric parameters derived from SRTM data and band ratios used for iron-bearing minerals from Sentinel 2 bands are selected as variables in the accuracy of classification. The result showed that gneisses were recognized with the highest accuracy in the Khulstai complex, and limestones and Quaternary sediments were also well predicted. Moreover, the tectonic pattern was also well recognized from the results and compared to the existing maps provided a more detailed geological image of the area. This study emphasized the need for samples as baseline data to improve the machine learning methods, and the method provides an appropriate basis for fieldwork.

How to cite: Badrakh, M., Tserendash, N., Choindonjamts, E., and Albert, G.: Random Forest Classification of Proterozoic and Paleozoic rock types of Tsagaan-uul area, Mongolia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5684, https://doi.org/10.5194/egusphere-egu23-5684, 2023.

Following drastic changes in geoenvironmental components by coseismic landslides in mountainous watersheds, more gradual changes can be observed in the elements, including bare-land surface conditions, sediment connectivity, and vegetation recovery on sloping terrains. Such geoenvironmental changes may continue for years to decades, with complex interrelationships among various geomorphological and ecological factors. Their assessments are also crucial for local to regional environmental management. After the occurrence of numerous coseismic landslides triggered by the 2018 Hokkaido Eastern Iburi Earthquake in northern Japan, geomorphological and geoecological changes were explored using optical and laser sensors on uncrewed aerial systems. Morphological characteristics of the landslide-affected slopes in the watersheds were assessed with structure-from-motion multi-view stereo photogrammetry and light detection and ranging topographic datasets, while vegetation recovery on the slopes was examined with visible-light and near-infrared images. Although spatial relationships among morphological developments, sediment mobility, and vegetation recovery were not clearly observed, their general temporal trends may be correspondent. Dominant processes affecting the morphological developments are supposed to be frost heave in the cold climate and non-frequent high-intensity rainfalls, and these can be conditioning vegetation growth. Such local changes will be further examined on a wider, regional scale. 

How to cite: Hayakawa, Y. S., Lo, T., Zulhilmi, A., Yu, X., and Wang, X.: Post-earthquake geoenvironmental changes in landslide-affected watersheds in Atsuma, Hokkaido (Japan), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5689, https://doi.org/10.5194/egusphere-egu23-5689, 2023.

Understanding the fault dynamics in volcanic areas is not a simple task, mainly due to both the heterogeneity of volcanic structures and the local stress distribution. The presence of high temperature-high pressure geothermal fluids and relative high strain rates, and the occurrence of viscous processes in the deeper part of the volcano further contribute to generate complex patterns of strain load and release, possibly with aseismic creep and differential movements along the faults.

We present the case of an active fault located Casamicciola Terme town – in northern area of the volcanic caldera of Ischia Island (Southern Italy) – where repeated destructive earthquakes occurred at least since 1769, even causing thousands of victims in a single event, with the last one striking in 2017. To assess a possible mechanism leading to the activation of the Ischia main seismogenic fault, its cyclic nature and the related hazard, we performed a joined analysis of the ground vertical movements, obtained from cGPS (2001-present), DInSAR (2015-2018) time-series, and levelling data of the island (1987-2010). The geodetic data indicate that Casamicciola seismogenic fault is characterized by a complex dynamic, with some pre- and post-seismic aseismic dislocation, along sectors that move differentially, in response to the long-term subsidence of the island. Based on the ground deformation rate and on the distribution of degassing areas, we speculate that fluid pressure variations may have a major role in modulating the apparent non-stationarity of the Ischia stronger earthquakes. Furthermore, we suggest that a punctual monitoring of the distribution in space and time of the aseismic creep could provide clues on the state of strain of the seismogenic fault.

How to cite: Carlino, S., Pino, N. A., Beccaro, L., and De Martino, P.: Aseismic creep and coseismic dislocation at an active fault in volcanic area: the case of Ischia Island, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5750, https://doi.org/10.5194/egusphere-egu23-5750, 2023.

Karstification is a ubiquitous feature in carbonate rocks. The origins can be hypogenic or epigenic based on the source of the reacting fluids. The presence of karstified lithologies and their spatial heterogeneity poses a major risk in subsurface energy utilization goals (hydrocarbons, geothermal etc). Such dissolution features tend to organize as spatial networks, with their evolution controlled by a complex interplay of several factors, including natural mineralogical variations in host rocks, effects of pre-existing structures, directional history of palaeo-flow paths, and competition between convective transport and dissolution. Accurate quantification of the spatial distribution of karst is difficult owing to resolution issues in 3D data such as seismic and ground penetrating radar. Recent advances in Simultaneous Location and Mapping (SLAM) Lidar technology have made possible to acquire karst cave passage geometries at very high-resolution with relative ease compared to conventional terrestrial lidar. In this contribution, we present a unique dataset of more than 80 caves, scanned using SLAM lidar, in Jurassic carbonates from northern Bavaria, Germany. We introduce a methodology for robustly deriving morphometrics of karstic caves using Minkowski tensors and spatial graph theory. The method is based on a combination representation of cave passage skeletons as spatial graphs and 2D passage cross-sections using Minkowski functionals. The enriched topological representation enables detailed analysis of internal spatial variation within a single cave and also comparison with cave geometries from other caves. We derive a typology of cave systems based on the degree of structural control on karstification using the database.

How to cite: Prabhakaran, R., Smith, R., Koehn, D., Bruna, P.-O., and Bertotti, G.: Quantifying karstic geomorphologies using Minkowski tensors and graph theory: Applications to SLAM Lidar data from carbonate caves in Northern Bavaria (Germany), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6832, https://doi.org/10.5194/egusphere-egu23-6832, 2023.

Ground based remote sensing devices increasingly incorporate low cost single board computers such as a Raspberry Pi to capture and analyze images and data from the environment. Useful and cheap as these devices are, they are not designed for use in extreme conditions and as a consequence often suffer from early failure. Here we describe a system that incorporates a commercially available rugged Edge Computer running embedded Linux that is designed to operate in remote and extreme environments. The AVERT system  (Anticipating Volcanic Eruptions in  Real Time) developed at Columbia University in New York and funded by the Moore Foundation uses solar and wind powered Sensor nodes configured in a spoke and hub architecture currently operating on two volcanoes overseen by the Alaska Volcano Observatory in the Aleutian Islands, Alaska. Multiple Nodes distributed around the volcanoes are each controlled by an Edge Computer which manages and monitors local sensors, processes and parses their data via radio link to a central Hub and schedules system components to wake and sleep to conserve power. The Hub Edge Computer collects and assembles data from multiple Nodes and passes it via satellite, cellular modem or radio links to servers located elsewhere in the world or cloud for near real-time analysis. The local computer enables us to minimize local power demand to just a few watts in part due to the extremely low power sleep modes that are incorporated into these devices. For instance, a Node incorporating a webcam, IRCam, weather station, Edge Computer, network switch, communications radio and power management relays draws only 4.5W on average. In addition, this level of local computing power and a mature Linux operating environment enables us to run AI algorithms at source that process image and other data to flag precursory indicators of an impending eruption. This also helps to reduce data volume passed across the network at times of low network connectivity. We can also remotely interrogate any part of the system and implement new data schemes to best monitor and react to ongoing events. Future work on the AI algorithm development will incorporate local multisensor data analytics to enhance our anticipatory capability.

How to cite: Frearson, N., Plank, T., Lev, E., Dong, L., and Bacon, C.: Low Power, Rugged Edge Computing provides a low cost, powerful solution for on the ground remote sensing in extreme environments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7265, https://doi.org/10.5194/egusphere-egu23-7265, 2023.

Radon, ²²²Rn, is a radioactive constituent of the surface layer of the atmosphere. The analysis of the temporal and spatial variations in the flux of radon across the soil–air interface is a promising tool to study geo-dynamical processes. However, many of these variations are induced by external variables, such as temperature, barometric pressure, rainfall, or the location of the instrumentation, among others.

Anomalous CO₂ degassing has been observed since the end of November 2021 in the neighborhoods of La Bombilla and Puerto Naos, located in the western flank of La Palma, about 5 km distance southwestern of the 2021 Tajogaite eruption vents (Hernández et al. 2022). In order to complement these observations with other independent parameters, a set of radon monitoring stations have been deployed in that area. In an attempt to filter out non-endogenous variations in the radon signal, we have implemented time-series numerical filtering techniques based on multi-variate and frequency domain analysis. A background level for radon emissions at various locations could therefore be defined, by which correlations between radon concentration, gaseous emissions and dynamical processes could be carried out. Some preliminary results corresponding to the first 3 months of data (october-december 2022) are presented.

Hernández, P. A., Padrón, E., Melián, G. V., Pérez, N. M., Padilla, G., Asensio-Ramos, M., Di Nardo, D., Barrancos, J., Pacheco, J. M., and Smit, M.: Gas hazard assessment at Puerto Naos and La Bombilla inhabited areas, Cumbre Vieja volcano, La Palma, Canary Islands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7705, https://doi.org/10.5194/egusphere-egu22-7705, 2022.

How to cite: Eff-Darwich, A., Padilla, G. D., Barrancos, J., Rodríguez-Losada, J. A., Hernández, P. A., Pérez, N. M., Álvarez Díaz, A. J., González Pérez, A. M., García, J., Santana, J. M., and Padrón, E.: Are they radon or random signals? Analysis of time series of 222Rn activity concentrations in populated areas of La Palma (Canary Islands, Spain), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8673, https://doi.org/10.5194/egusphere-egu23-8673, 2023.

The time scale of ground displacement at volcanoes varies between short, sub second seismic events, to days, months or even years. This study is focused on data from seismic and GNSS stations located around Mount Etna. The GNSS and seismic stations operate at different time scales. Data from these different time scales is extracted and combined in order to better understand the subsurface dynamics. The overall aim of this research is to improve volcanic forecasting and monitoring. It does this in a novel way by applying signal processing and machine learning techniques to the rich dataset.

Mount Etna offers an interesting case study as it is a widely monitored volcano with a variety of sensors and with a rich pool of data to analyse. Additionally the volcanic dynamics at Mount Etna are complex. This is a volcano where there is a variety of different sub-surface dynamics due to the movement of both deep and shallow magma. This allows for rich insights to be drawn through the combination of different signal types.

This study looks at combining the information obtained from the seismic array at Mount Etna, with the information obtained from various GNSS stations on the volcano. The seismic array has been able to capture ground velocity data in the frequency range 0.025 Hz to 50 Hz from a range of stations at different locations across the volcano. The GNSS stations measure ground displacement with a sampling frequency of 1 Hz, and they allow for longer term ground dynamic analysis.

We analyse different seismic events, and relate the type and number of the seismic events to the long term ground deformation that we see in the recorded GNSS data. Where links between the two signal types have been identified, research is ongoing to establish a direct connection with known volcanic activity on Mount Etna. This will help establish what the relationship that we are seeing signifies. This integration of data from different types of sensors is a significant step into bridging the gap between seismic and quasi-static ground displacement at active volcanoes and should open the path toward more in depth volcanic monitoring and forecasting.

How to cite: Carthy, J., Vásquez Castillo, A., Titos, M., Zuccarello, L., Cannavò, F., and Benitez, M. C.: Integration of Seismic and Quasi-Static Signals for Improved Volcanic Monitoring, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8795, https://doi.org/10.5194/egusphere-egu23-8795, 2023.

We are showing an application of the 3D self-constrained depth weighted inversion of the inhomogeneous gravity field (Vitale and Fedi, 2020) of the Vredefort impact site.

This method is based on two steps, the first being the search in the 3D domain of the homogenous degree of the field, and the second being the inversion of the data using a power-law weighting function with a 3D variable exponent. It does not involve directly data at different altitudes, but it is heavily conditioned by a multiscale search of the homogeneity degree.

The main difference between this inversion approach and the one proposed by Li and Oldenburg algorithm (1996) and Cella and Fedi (2012) is therefore about the depth weighting function, whose exponent is a constant through the whole space in the original Li and Oldenburg and Cella and Fedi approaches, while it is a 3D function in the method which we will discuss here.

The model volume of the area reaches 20 km in depth, while along x and y its extension is respectively 41 by 63 km. The trend at low and middle altitudes of the estimated β related to the main structures is fitting the expectations because the results relate to two main structures, which are geometrically different: the core is like a spheroid body (β ≈ 3) and the distal rings are like horizontal pipes or dykes (1 < β < 2).

With a homogeneous depth weighting function, we recover a smooth solution and both the main sources, the main core and the rings of the impact, are still visible at the bottom of the model (20 km). This is not in agreement with the result by Henkel and Reimold (1996, 1998), which, based on gravity and magnetic inversion supported by seismic data, proposed a model where the bottom of the rings is around 10 km and the density contrast effect due to the core structure loses its effectiveness around 15 km.

Instead, using an inhomogeneous depth weighting function (figure 28) we can retrieve information regarding the position at depth of both core and distal ring structures that better fits the above model. In fact, the bottom of the distal ring structure, that should be around 10 km according to Henkel and Reimold (1996, 1998), is recovered very well using an inhomogeneous depth weighting function, while in the homogeneous case we saw that the interpreted structure was still visible at large depths.

In addition, also the core structure is shallower compared to the homogeneous approach and seems more reliable if we compare it with the model of Henkel and Reimold (1996, 1998).

Instead, the inhomogeneous approach presented in this paper leads naturally us to a better solution because it takes into account during the same inversion process of the inhomogeneous nature of the structural index within the entire domain.

How to cite: Vitale, A. and Fedi, M.: Vredefort impact site modelling through inhomogeneous depth weighted inversion., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10069, https://doi.org/10.5194/egusphere-egu23-10069, 2023.

The local studies and reports indicate that the temperature of Panama has increased by approximately 1°C since the 1970s. More evidence shows a constantly rising sea level in the Guna Yala archipelago, coral bleaching on both coasts, and increasingly more frequent and extreme precipitation events throughout Panama. This study includes an analysis of over 400 scientific publications made by researchers from multiple centres and more than 20 Panamanian official reports due to Panama's mandate and duties under the international climate accords. To summarise the results, the studies were gathered according to the climate change effects by Panamanian locations and analysed posteriorly using Rstudio and ArcMAP. The results indicate a significant increase in climate change research beginning in 2007.

This study identified and examined the essential findings per hydroclimatic region, showing the trends, limitations, collaborations, and international contributions. Climate change research in Panama includes some of the longest-term meteorological, hydrological, oceanographic, and biological studies in the neotropics. The most significant number of identified climate change-related studies were conducted, at least in part, in the Barro Colorado Natural Monument located in central Panama. Other frequently used sites include Metropolitan Natural Park, Soberania Park, the Panama Canal Watershed and the Caribbean coast of Colón and Bocas del Toro, primarily due to research conducted by Smithsonian Tropical Research-affiliated investigators. The tropical forests of Panama are some of the bests studied in the world; however, research has been concentrated in a relatively small number of locations and should be expanded to include additional areas to achieve a more complete and comprehensive understanding of climate change will impact Panama in the future.

How to cite: Cárdenas-Castillero, G., Paton, S., Noriega, R., and Calderón, A.: The Dynamics of Climate Change Science and Policy in Panama: A Review, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11065, https://doi.org/10.5194/egusphere-egu23-11065, 2023.

The city of St. Gallen is located in the Molasse Basin of northeast Switzerland. Mesozoic units of the substratum are affected by a fault system hosting a hydrothermal reservoir. In 2013 a deep geothermal drilling project started in an area close to the city. During a phase of reservoir stimulation, a sequence of more than 340 earthquakes was induced with a maximum magnitude M_L 3.5. Stress inversion of seismological datasets became an essential tool to retrieve the stress field of active tectonics areas. With this aim, a dataset of the best constrained Fault Plane Solutions (FPSs) was processed in order to qualitatively retrieve stress-fields active in the investigated volume. FPSs were obtained by jointly inverting the long-period spectral-level P/S ratios and the P-wave polarities following a Bayesian approach (BISTROP). Data were preliminarily processed by the Multiple Inverse Method to evaluate the possible dataset heterogeneity and separate homogeneous FPS populations. The resulting dataset was then processed using the Bayesian Right Trihedra Method (BRTM). Considering that hypocentral depths range between 4.1 and 4.6 km b.s.l., in order to emphasize depth-related stresses, we performed a first step of raw stress inversion procedure splitting the data into five subsets, grouping events located inside 100-m depth ranges. Once the presence of stress variations with depth has been excluded, the second step of fine stress inversion procedure was performed on the entire dataset. The stress-inversion procedure highlights an active stress field dominated by a well-constrained NE low-plunging σ₃ and a corresponding NW low-plunging σ₁. The corresponding Bishop ratio confirms the stability of the retrieved attitudes. Results are in good accordance with the regional stress field derived from regional natural seismicity. Additionally, the retrieved, dominant, stress field is coherent with the regional tectonic setting.

This research has been supported by PRIN-2017 MATISSE project (No. 20177EPPN2).

How to cite: Massa, B., Adinolfi, G. M., Convertito, V., and De Matteis, R.: Stress field analysis from induced earthquakes caused by deep fluid injection: the 2013 St. Gallen (Switzerland) seismic sequence., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12050, https://doi.org/10.5194/egusphere-egu23-12050, 2023.

The presence of potentially toxic elements (PTEs) derived from anthropogenic sources in soil represents a serious issue for animal and human health. These elements can easily move from the geological compartment to the biological compartment through to the food chain. (Jarup, 2003).

The geochemical knowledge of a territory allows to assess the degree of contamination of the environment, to locate the sources of environmental hazard and, possibly, to manage the anomalous concentrations of the PTEs in environmental matrices with the purpose of eliminating or minimizing their negative impact on the health of living beings. (Reimann et al. 2005).

Several studies have been already carried out to determine the distribution patterns of PTEs in the soil of Campania region (Southern Italy) (De Vivo et al., 2022) but little is known about the transfer processes of contaminants from soils to agricultural products.

In light of above, we present the results of a new study whose purpose was to determine the Transfer Factors (TFs) of PTEs from soil to a series of agricultural products commonly grown in Campania.

Considering the complex geological and geomorphological settings of the region and the diffuse presence of an historical anthropization related to the industry, agriculture, and urbanization, TFs were calculated for a relevant number of fruit and vegetable samples (3731 specimens). They were collected across the whole regional territory to detect differences between analysed species and to highlight the spatial changes in TFs occurring for individual species.

The TFs were calculated starting from the quasi-total (based on Aqua Regia leaching) and bioavailable (based on Ammonium Nitrate leaching) concentrations of PTEs in 7000 and 1500 soil samples, respectively.

Preliminary results show that TFs determined for the various agricultural species vary in space and in amount independently from the original elemental concentrations in soils. High values of TFs are found in areas where PTE concentrations in soil are low and vice versa, thus suggesting that multiple regression and multivariate analyses could be performed to investigate if some additional chemical and physical characteristics of soil (pH, grainsize, OM, etc.) could have a relevant weight on the transfer processes of contaminant from the soil to the plant life.

References

Järup L. 2003. Hazards of heavy metal contamination. Br. Med. Bull. 68, 167–182.

Reimann C., de Caritat P. 2005. Distinguishing between natural and anthropogenic sources for elements in the environment: regional geochemical surveys versus enrichment factors. Science of The Total Environment, Volume 337, Issues 1–3, pages 91-107.

De Vivo B. et al. 2022. Monitoraggio geochimico-ambientale dei suoli e dell'aria della Regione Campania. Piano Campania trasparente. Volume 4. Aracne Editore, Genzano di Roma.

How to cite: Pacifico, L. R., Guarino, A., Brambilla, G., Pizzolante, A., and Albanese, S.: Assessing the transfer factors (TFs) of contaminants from soil to plants: the case study of Campania region (Southern Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13693, https://doi.org/10.5194/egusphere-egu23-13693, 2023.

Geodetic modelling is a significant procedure for detecting and characterizing unrest and eruption episodes and it represents a valuable tool to infer volume and geometry of volcanic source system.

In this study, we analyse the 2009–2013 and the ongoing 2019-2022 uplift phenomena at Campi Flegrei (CF) caldera in terms of spatial and temporal variations of the stress/strain field. In particular, we investigate the characteristics of the inflating sources responsible of these main deformation unrests occurred in the last twenty years. We separately perform for the two considered periods a 3D stationary Finite Element (FE) modelling of geodetic datasets to retrieve the geometry and location of the deformation sources. The geometry of FE domain takes into account both the topography and the bathymetry of the whole caldera. For what concern the definition of domain elastic parameters, we take into account the Vp/Vs distribution from seismic tomography. In order to optimize the nine model parameters (center coordinates, sferoid axes, dip, strike and over-pressure), we use the statistical random sampling Monte Carlo method by exploiting both geodetic datasets: the DInSAR measurements obtained from the processing of COSMO-SkyMed and Sentinel-1 satellite images. The modelling results for the two analysed period are compared revealing that the best-fit source is a three-axis oblate spheroid ~3.5 km deep, similar to a sill-like body. Furthermore, in order to verify the reliability of the geometry model results, we calculate the Total Horizontal Derivative (THD) of the vertical velocity component and compare it with those performed directly on the two DInSAR dataset.

Finally, we compare the modelled shear stress with the natural seismicity recorded during the 2000-2022 period, highlighting high values of modelled shear stress at depths of about 3.5 km, where high-magnitude earthquakes nucleate.

How to cite: Castaldo, R., Barone, A., Vincenzo, D. N., Antonio, P., Susi, P., Giuseppe, S., Pietro, T., and Anna, T.: Analysis and Modelling of 2009-2013 vs. 2019-2022 Unrest Episodes at Campi Flegrei Caldera, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13853, https://doi.org/10.5194/egusphere-egu23-13853, 2023.

We present a multiscale analysis of magnetic data in the archaeological site of San Pietro in Crapolla (Massa Lubrense, near Naples, Italy). The site consists of the ruins of an ancient abbey. We computed the Wavelet Transform of the Gradiometric measurements and decomposed the data at different scales and positions by a multiresolution analysis, allowing an effective extraction of local anomalies. Modelling of the filtered anomalies was performed by multiscale methods known as “Multiridge analysis” and “DEpth from eXtreme Points (DEXP)”.  The first method analyses a multiscale dataset at the zeroes of the first horizontal and vertical derivatives besides the potential field data themselves (ridges).  The Wavelet Transform Modulus Maxima  lines converged to buried remains. The field, scaled by a power law of the altitude (DEXP transformation) allowed estimates of source depths at its extreme points. The depth estimations for the buried structures obtained from the two methods are very close each other and fairly agree with those from the modelling of GPR anomalies. On the basis of these results, an archaeological excavation followed our indications and brought to light ancient walls.

How to cite: Bianco, L., Fedi, M., and La Manna, M.: Multiscale magnetic modelling in the ancient abbey of San Pietro in Crapolla, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15127, https://doi.org/10.5194/egusphere-egu23-15127, 2023.

This work presents an overview of some applications of synthetic aperture radar (SAR) interferometry technology for the detection and analysis of large ground displacements occurring in volcanic areas, with the aim to retrieve the three-dimensional (3-D) ground displacement field (up-down, east-west, north-south). Specifically, the work summarizes and investigates the potential of Bursted Overlapped Interferometry (BOI) that properly combined can allow the retrieval, at different scales of resolution and accuracies, of the north-south components of the ground deformations, which are usually not available considering conventional SAR interferometry techniques. In this context, the almost global coverage and the weekly revisit times of the European Copernicus Sentinel-1 SAR sensors permit nowadays to perform extensive analyses with the aim to assess the accuracy of the BOI techniques. More recently, Spectral Diversity (SD) methods have been exploited for the fine co-registration of SAR data acquired with the Terrain Observation with Progressive Scans (TOPS) mode. In this case, considering that TOPS acquires images in a burst mode, there is an overlap region between consecutive bursts where the Doppler frequency variations is large enough to allow estimating and compensating for, with great accuracy, potential bursts co-registration errors. Additionally, and more importantly, in the case of non-stationary scenarios, it allows detecting the ground displacements occurring along the azimuthal directions (almost aligned along north-south) with centimeter accuracy. This is done by computing the difference between the right and left interferograms, i.e., the burst overlapped interferogram, and relating it to the ongoing deformation signals.

This work aims to apply the BOI technique in selected volcanic and seismic areas to evaluate the impact of this novel technology for the analysis of quantifying, over small, covered regions, the accumulated ground displacements in volcanic areas. In such regions, the interest is on quantifying the accuracy of integrated BOI systems for the retrieval of 3-D displacements. To this aim, we selected as a test site the Galapagos Island and we analyze with BOI the north-south ground displacements. At the next EGU symposium, the results of the BOI analyses will be presented, thus also providing comparative analyses with the results obtained from the use of potential field method applied on the ground displacements in volcanic areas. More specifically, by adopting this technique, we are able to estimate independently the north-south components of the ground displacement by exploiting the harmonic properties of the elasticity field.

How to cite: Pepe, A., Barone, A., Mastro, P., Tizzani, P., and Castaldo, R.: Synthetic aperture radar burst overlapped interferometry for the analysis of large ground instabilities: Experiments in volcanic regions., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15190, https://doi.org/10.5194/egusphere-egu23-15190, 2023.

The central‐eastern sector of the Phlegraean Fields caldera, southern Italy, is one of the most intensely studied and monitored volcanic active area of the word. This area reveals typical characters of a high‐ enthalpy geothermal systems. However, recently the presence of two different geothermal reservoirs has been outlined: one located in the central sector dominated by highly active vapours generated by episodic arrival of CO₂‐rich magmatic fluids and the other one located in the eastern sector (Agnano zone) characterized by a shallow (400-500 m b.s.l.) still hot reservoir, heated by the upward circulation of deep no magmatic hot vapor.

In this study we present preliminary results deriving from the integration of different geophysical surveys carried out in the Agnano plain area, in the frame of the GEOGRID research project. We acquired high-resolution gravity data along two parallel profiles and we investigated the depth, shape and density contrast of the subsurface structures by the CompactDEXP (CDEXP) method, a multiscale iterative imaging technique based on the DEXP method. The resulting density models, together with DC resistivity and stratigraphic data, outlines the presence of a complex morphology of the Agnano subsoil characterized by a horst-graben structure. The importance of the structural lines identified by geophysical data, is also confirmed by the alignment of correlate outcropping thermal waters.

How to cite: Milano, M., Cavuoto, G., Corniello, A., Di Fiore, V., Fedi, M., Massarotti, N., Pelosi, N., Punzo, M., Tarallo, D., Donnarumma, G. P., and Iorio, M.: Multiscale imaging of low-enthalpy geothermal reservoir of the Phlegraean Fields caldera from gravity and resistivity data., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16132, https://doi.org/10.5194/egusphere-egu23-16132, 2023.

Birnessite occurs as a major manganese oxide in sediments. It is characterized by a high adsorption capacity for trace elements, including arsenic. However, the effects of birnessite on arsenic cycling were less intensively investigated than that of goethite, a commonly recognized arsenic host. Therefore, this study utilizes arsenic-bearing solutions containing 0.1–50 ppm arsenic to synthesize birnessite and uses arsenic sequential extraction procedure (SEP) analysis to quantify its arsenic co-precipitation and adsorption capacity.
    SEPs showed that adsorbed/structural arsenic ratio grew from 0:100 to 60:40, with arsenic concentration increasing from 0.1–50 ppm, implying saturation of structural arsenic. SEPs quantify the adsorbed and structural As of birnessite being 0.831 and 1.308 mg/g, respectively. However, the low arsenic concentrations of < 1% in residual solutions indicate nonattainment of the maximum adsorption capacity. Subsequent adsorption experiments using higher initial arsenic concentrations reaching 250 ppm determined the maximum arsenic adsorption capacity to be 19.81 mg/g at pH 7, comparable to the values of 15.3–22.5 mg/g at pH 6.5 (Manning et al., 2002; Singh et al., 2010) and that of 3.79–15.73 mg/g for goethite. It then appears that birnessite adsorption/desorption is more effective than precipitation/dissolution in controlling arsenic cycling. However, the consideration based on the maximum adsorption capacity might overrate the controls of adsorption/desorption relative to precipitation/dissolution because the natural water generally contains less arsenic than that used for the adsorption experiments. Therefore, we conducted adsorption experiments with low arsenic concentrations of 0.5 ppm and a solid/liquid ratio of 0.01 to 0.001. The results showed that adsorption capacity rose abruptly to 1.416 mg/g in two weeks and then slowly increased to 1.523 mg/g after three months. This feature indicated incomplete filling of the adsorption sites on the surface of birnessite at low As concentration despite its large specific surface area. Another controlling factor was the abundance of birnessite in sediments. If 10% of MnO (0.05–0.15%) in the Chianan sediments in southern Taiwan occurred as birnessite, the adsorbed arsenic was calculated to be 0.0005–0.022 mg, corresponding to < 2 % of adsorbed arsenic in 1 g sediments, based on the SEP data of Yang et al. (2016). In the extreme case that all the Mn occurred as birnessite, birnessite could account for up to 25% of the adsorbed arsenic. Apparently, birnessite is not a major contributor to surface arsenic cycling. However, this inference must be evaluated by considering the adsorption and co-precipitation data from goethite and goethite proportions in sediments.

How to cite: Huang, H. W., Yang, H.-J., Huang, L.-Y., and Chieh, C.-J.: Experiments of arsenic (V) adsorption on birnessite: implications on arsenic cycling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1225, https://doi.org/10.5194/egusphere-egu23-1225, 2023.

For the past decades, scientists have endeavored to develop efficient and suitable approaches to monitor heavy-metal pollution through technological development. Conventional monitoring methods for heavy metals are still complicated, relatively expensive, and time-consuming. This research aims to develop an innovative heavy-metal monitor, the novel approach of ion-exchange resin sachets combined with X-ray fluorescence core scanner (XRF-CS), to achieve an efficient way to effectively monitor vast areas for contamination. The resin sachets, which have a large capacity to quickly take up heavy metals, were deployed in the river weekly to capture heavy metals and then analyzed using the non-destructive, fast, and cost-efficient Itrax XRF core scanner. Two four-week sampling sessions, performed during the dry and wet periods, respectively, were conducted in northeastern Taiwan, where the environment was contaminated by a copper smelter and coal mine activities in the late twentieth century. The results suggest that ion-exchange resins are useful as long-term monitors of heavy metals in a low pollution-level settings (metal concentration <1 mg/L), and that XRF core scanner data truly reflect metal pollution concentrations as measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). This approach allows us to pinpoint pollution sources along the studied river. Especially, Zn, Ni, Mn, Fe, Cu, Ca, and Sr could be detected near pollution sources, where cps values were 1.8 to 3430.6 times higher than in unpolluted areas. Zn shows the largest difference between polluted and non-polluted areas, with the cps values of the samples in polluted areas 3528 times higher than their non-polluted counterparts. Ni, Mn, Fe, Cu, Ca, and Sr’s cps values were 1.8, 29.2, 46.1, 2.4, 6.2, and 5.9 times higher, respectively, than the corresponding counts measured in non-polluted areas. In addition, our results demonstrate that the intensity of precipitation influences the amount of metal adsorption in the resins; resins showed less adsorption in the dry period, and cps values slightly dropped to 81 to 84 percent of the wet period. In summary, ion-exchange resins are a sensitive tool that can be applied in pollution monitoring at various pollution levels due to their high performance in adsorbing heavy metals. Consequently, ion-exchange resin sachets in combination with XRF core scanner analysis is a cost-effective way to monitor large areas of potentially polluted aquatic systems quickly.

How to cite: Jian, Y.-C., Löwemark, L., and Liao, A. C.-Y.: Application of ion-exchange resin sachets and XRF-CS in heavy metal pollution sources monitoring, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4067, https://doi.org/10.5194/egusphere-egu23-4067, 2023.

Determining the background values of chemical components in environmental matrices is a difficult task. This is particularly true in regions where the human impact due to industrial, mining, agricultural and urban activities coexists with a geological (geogenic) anomaly, which influences the concentration of certain elements in soils, waters and air. In these cases, the term geochemical baseline (GB) is preferable, since it considers the actual content of that element in the superficial environment at a given point in time, including both geogenic and anthropogenic contribution. In this study, a total of 102 top- and sub-soil (collected at 10-50 cm and 50-154 cm depth, respectively) samples and seven rocks, onto which the soils developed, were collected for the determination of GBs for selected chalcophile (As, Cu, Hg and Sb) and siderophile (Co, Cr, Ni, and V) elements in 25.6 km² around the former mining area of Abbadia San Salvatore (Mt. Amiata, Southern Tuscany, Italy). For about one century, cinnabar (HgS) ore deposits have been exploited to produce liquid mercury from the Mt. Amiata volcanic system and its surroundings, which represents a world-class mercury district. The < 2 mm (as required by the national regulamentation) fraction of the samples was pulverized and analysed by ICP-MS (As, Hg and Sb) and ICP-AES (Co, Cr, Ni, and V) after aqua regia digestion. The compositional data analysis of multivariate compositional vectors, based on the log-ratio approach was used to assess the nature of the geochemical . According to our findings, the centred log-ratio (clr) opposed to that of raw/log transformation, enhances the spatial mapping. This also allowed to obtain better-separated variables in the robust Principal Component Analysis (rPCA). Log-ratio geographical maps evidenced that the underlying bedrock geology (parent lithologies), rather than anthropogenic causes, controls the distribution of the  great majority of the elements in the top- and sub-soils. The resulting clr-PCA approach, associated with the geological features, indicates that the geochemical pattern of Hg-As is to be related to the volcanic rocks and ore-deposits, although an anthropogenic influence due to the past mining activity in the topsoils cannot be ruled out. Sb, Co, Cr, Ni, and V distribution patterns are in most cases attributed to calcareous and clay lithologies. The anomalous content of Sb found within the volcanic rocks was likely due to the presence of previously undetected old mining dump. The two data populations (volcanic and calcareus-clay lithologis) were separated into two different databases and the outliers were removed when necessary. By processing the two datasets, the US-EPA’s ProUCL software was used for calculating the GBs for the selected suite of elements. The obtained values are paramount for establishing specific guidelines and quality standards in environmental legislation and policy-making to be applied by the Municipality of Abbadia San Salvatore

How to cite: Meloni, F., Nisi, B., Gozzi, C., Cabassi, J., Montegrossi, G., Rimondi, V., Rappuoli, D., and Vaselli, O.: Geochemical baseline values of chalcophile and siderophile elements in soils around the former mining area of Abbadia San Salvatore (Mt. Amiata, Southern Tuscany, Italy)., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6351, https://doi.org/10.5194/egusphere-egu23-6351, 2023.

The Almadén district has been the World’s largest producer of mercury (Hg), for more than 2000 years. The mining activity in the district ceased some 10 years ago; however, the generalized pollution of soils and stream sediments, as well as the atmospheric emissions from these and other sources, still represent possibilities to toxify the human food chain. The Valdeazogues river crosses completely the district, with some 150 km2 extension, and including a huge mine, three mines of median importance, and up to 60 points where cinnabar (HgS) has been recognized.

Largemouth bass (Micropterus salmoides) is a carnivorous freshwater gamefish, very common along the Valdeazogues river. For years it was fished to complement the diet of the local inhabitants, although nowadays is not so common to consume it. We obtained 28 specimens, with sizes between 69 and 335 mm and weight between 11 and 552 gr, in a transect from the El Entredicho open pit to downstream the district (some 36,3 km). The specimens were analyzed using atomic absorption spectrometry with Zeeman effect.

Results show important variations throughout the transect; the largest fish in terms of weight and length had the highest Hg concentration (5246 ng/g), much higher than the fish with the lowest concentration (473.2 ng/g), which was not the specimen with the lowest size. Besides, as we go downstream the Valdeazogues River, moving away from the Entredicho Mine (considered to be the main source of contamination), Hg concentrations drops considerably until stabilizing at approximately 1200 - 1500 ng/g.

How to cite: Barquero, J. I., Higueras, P., Hidalgo, J. J., Esbri, J. M., Lorenzo, S., and Garcia-Ordiales, E.: A transect of mercury concentrations in fish (Black bass, Micropterus salmoides) from the Valdeazogues river, Almadén Hg mining district, South Central Spain., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7980, https://doi.org/10.5194/egusphere-egu23-7980, 2023.

In the last decades, intentional illegal burnings increased in the numbers and became a problem of a global interest. As a consequence, human beings can be exposed to potentially toxic elements (PTEs) released during the combustion, dispersed by the wind, and accumulated in the fire’s ashes (Dimitrios, 2020).

Several studies highlighted that PTEs content in the deposited ashes can modify the chemical and the physical characteristics of the soil and, therefore, it can influence the development and growth of local microorganisms and vegetation (Raison, 1979). The geochemical characteristics of ashes depend on the nature of burned material (Dermibas et al. 2003) and on many other variables such as the intensity of combustion, the composition of the underlying soil, the bedrock type, etc.

The aim of the study was to verify at two different sites the environmental impact related with the on-set of two fire events occurred in Campania region (Southern Italy) during the 2017 summer season. One of the fires involved a forest (on the slopes of Mt. Somma-Vesuvius) and one affected a waste disposal site, known as Ilside (close to the city of Caserta). The variation occurred to concentration of PTEs in topsoil was used for the purpose.

Specifically, at both locations, 30 topsoil samples were collected before and right after the fire events. In total 60 samples were collected at the surroundings of Mt. Somma-Vesuvius slopes and 60 at the surroundings of Ilside. The post-fire samples were collected in correspondence of pre-existing sampling sites along the main wind directions recorded at the time of the fires.

To explore the potential elemental contamination occurred in soils due to the fire events, the Enrichment Factor (EFs) of a selection of PTEs was determined and mapped for individual samples. A predominant enrichment of Hg was identified for both areas.

Further, a combined application of multivariate statistics and geospatial analysis was also performed on the calculated EFs.

For the Ilside site (where special waste and e-waste were involved in burning) the association of Hg, Tl, Cu and Co was identified as the main responsible of data variability; for the Vesuvian area, the association of Hg, Cu and Cr was found to be quite strong and possibly associated with forest biomass burning.

This study highlighted how different can be the chemical evidence left by fires occurring in the environment depending on the nature of the burnt materials. At same time, result showed that even the burning of biomasses proceeding from a natural area can input in the environment PTEs which can potentially generate an increase of the pre-existing degree of environmental hazard.

References

Dermibas, A., 2003. Toxic Air Emissions from Biomass Combustion, Energy Sources, 25:5, 419-427.

Dimitrios E. A., 2020. Suburban areas in flames: Dispersion of potentially toxic elements from burned vegetation and buildings. Estimation of the associated ecological and human health risk. Environmental Research, Volume 183, ISSN 0013-9351.

Raison, R.J., 1979. Modification of the soil environment by vegetation fires, with particular reference to nitrogen transformations: a review. Plant Soil 51, 73–108.

How to cite: Pacifico, L. R., Guarino, A., Pizzolante, A., and Albanese, S.: Assessing the impact of both a forest and a waste fire on the soil chemistry of two areas in Campania region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8217, https://doi.org/10.5194/egusphere-egu23-8217, 2023.

Detecting and quantifying geochemical transport through the critical zone at the continental to regional scale requires reliable  statistical procedures that can be uniquely interpreted. We present methods that provide different views on the same data sets and  formulate rules for their application and interpretation. The statistical analysis of cumulative distribution functions (CDFs) uses cumulative probability (CP) plots for spatially representative multi-element and multi-media data sets, preferably containing >1000 sites.
Mathematical models demonstrate how contamination can influence elemental CDFs of different  sample media. For example large-scale diffuse soil contamination leads to a distinctive shift of the low-concentration end of the distribution of the studied element in its top-soil CP plot, whereas high local contamination influences the high-concentration end. But also bio-geochemical processes can generate recognizable changes in elemental CDFs.
A related and partly unsolved problem is the correct interpretation of compositional data in terms of their transport through  the critical zone. 

How to cite: Fabian, K., Reimann, C., and Flem, B.: Geochemical transport through the critical zone: Statistics and reconstruction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8374, https://doi.org/10.5194/egusphere-egu23-8374, 2023.

In 2015, an environmental monitoring plan (http://www.campaniatrasparente.it) was launched with the aim of assessing the conditions of all environmental compartments (air, water, top and bottom soils, vegetables, biological samples) of the Campania region. A total of 5,333 topsoil samples were collected and analysed to determine the concentration of 52 chemical elements by means of Aqua Regia followed by ICP-MS. The main aim of prospecting campaign was to establish the ranges of the natural geochemical background for a few potentially toxic elements (PTEs) to be used as reference to define the degree of contamination of anthropized areas.

In the study area (about 13,600 km²) four volcanic areas are present and their pyroclastic products are spread across the regional territory due to a common (Plinian) explosive behaviour.

Due to the natural enrichment in some PTEs of soil developed on pyroclastic products, to discriminate the anthropic signals from the natural ones using geochemical data it is not a simple task when dealing with Campania soils. Therefore, as a preparatory work, to precisely identify regional areas mantled by “volcanic” soils we trained five machine learning algorithms (MLAs) to recognize when soil geochemistry is linked with the presence of volcanic products. All MLAs were implemented on centered log-ratio transformed data to reduce the closure and scaling effect commonly affecting geochemical data. In total, 1277 volcanic soils (VS) and 353 non-volcanic soils (NVS), respectively, were selected for the training phase. Data related with VS were selected based on the proximity of the samples with the volcanic centres, excluding highly anthropized areas. Data related with NVS were selected by consulting available detailed geological maps of those areas located faraway from volcanic areas where pyroclastic covers are completely absent. During the training phase, a cross-validation procedure was applied for parameters optimization. In the test phase all the MLAs showed an accuracy greater than 98% and the Random Forest algorithm proved to be the most accurate for the prediction of the remaining 3903 unlabelled soils. Therefore, a total of 1739 samples were classified as NVS and 2164 as VS. A subsequent comparison of the results with the existing distribution models of volcanic products has shown that samples classified as VS mainly fall in areas characterized by a high thickness of the pyroclastic fall deposits normally related to i) eruptions occurred in the last 10 Ky; ii) Campanian Ignimbrite eruption (ca. 39 ky BP); iii) Codola eruption (ca. 25 ky BP).

The MLAs results suggested that the most important chemical variables for the specific classification purpose were Ni, Cs, Ca, Co, Rb, Sc, Mn, U, Na. It is also evident that a first classification could be made by using few of these elements, as well. Our findings could be used as a valuable tool to better discriminate soil nature and geochemical characteristic aiming at a more effective assessment of natural background ranges for those elements sourced by both natural processes and human activities.

How to cite: Ambrosino, M., Albanese, S., Lucadamo, A., and Cicchella, D.: Combining compositional data analysis and machine learning to recognize where soil geochemistry is influenced by the presence of pyroclastic covers in Campania region (Southern Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8484, https://doi.org/10.5194/egusphere-egu23-8484, 2023.

The contamination of groundwater by geogenic sources is a major problem in many nations, especially those in the developing world. Fluoride (F) is one of the most pervasive and well-documented geogenic contaminants because of the severe health risks it poses due to its toxicity. F contamination in groundwater in India has been the subject of intense research over the past many decades. In this article, we describe the underlying geochemical process liable for F contamination as well as the factors controlling its spatiotemporal distribution in the Sedimentary Alluvial Plain (SAP) of Bankura District, West Bengal, India. To achieve the desired objective, representative groundwater samples were collected from tube wells and hand pumps at different locations of the study region during pre- and post-monsoon seasons. Collected samples were subjected to F and other hydrochemical analysis following standard test methods. Analysis shows that 37% of all groundwater samples collected during the pre-monsoon period have fluoride levels over 1.5 ppm (the limit specified by the World Health Organization, Geneva, 2004); however, the contamination level dropped to 30% during the post-monsoon period. The investigation of groundwater level changes indicates that, as water levels rise during the post-monsoon, F concentrations decrease due to the dilution effect. Piper trilinear diagram suggested Na-Ca-HCO₃ type of groundwater for both seasons. According to Gibbs diagrams, rock-water interactions (mineral dissolution) are responsible for major ion chemistry in groundwater samples. Factor analysis (FA) of hydrochemical parameters revealed that the occurrence of F in groundwater was due to the weathering and dissolution of fluoride-containing minerals. X-ray diffraction (XRD) analysis of SAP sediments further confirmed the presence of fluoride-bearing minerals (muscovite and fluorite) in the subsurface lithology of the region. A substantial positive loading (> 0.75) of F with pH and bicarbonate for FA demonstrates that F is being leached from the host material by an alkaline-dominated environment. To account for the spatial variability and seasonality to the spatial change of F concentration in groundwater of the SAP, geographical information systems tools and inverse distance weighting interpolation method were used. The results revealed that significant spatiotemporal variability of F contamination was mainly influenced by the recharging rainwater and the average recharge altitude of groundwater in the area under study. The contamination level is significant in the elevated region where replenishing rainwater is more likely to come into contact with fluoride-bearing minerals when it infiltrates and percolates through the vadose zone. This phenomenon increases the F leaching through chemical weathering along groundwater flow pathways. The findings of this study can serve as a scientific foundation for the efficient management of F-contaminated groundwater in the SAP.

How to cite: Ghosh, A., Gogoi, N., Kartha, S. A., and Mondal, S.: Geochemical Evaluation and Spatiotemporal Distribution of Fluoride in Groundwater of the Sedimentary Alluvial Plain of Bankura District, West Bengal, India, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9327, https://doi.org/10.5194/egusphere-egu23-9327, 2023.

Dichlorodiphenyltrichloroethane (DDT) and its metabolites are highly toxic and pose chronic effects to the biosphere. As a natural storage pool, forests have great potential to capture them from the atmosphere and migrate them to the forest soil, which, in turn, influences the safety of the forest ecological environment. In this study, a systematical survey of DDT and its metabolites has been carried out to measure their spatial variations in Chinese forest soils. The main objectives of this study were to (1) investigate the levels, distribution and sources of DDT and its metabolites, and further estimate their mass inventories in Chinese forest soils, (2) explore the impact of soil properties on their distribution, and (III) assess the ecological and health risks of DDT and its metabolites. The research results were as follows. The average concentration of ΣDDTs reached up to 9.75 ng/g, and p,p’-DDT is the main component. Significant difference in the concentration of ΣDDTs was observed between the southeast and northwest regions (p<0.01), which may be related to multiple factors such as pesticide use, rainfall and altitude. The forest soil quality inventory is about 0.58×103 tons, which is lighter than that of domestic farmland soil. 56.1% of soil samples were less than the low value of risk assessment (ERL). The concentration of ΣDDTs in the East and middle is higher than that in the West, and the high value is mainly distributed in the coastal areas. DDTs were mainly from the input of the mixed source composed of industrial DDT and dicofol, of which at least 97% came from industrial DDT and up to 4% from dicofol. ΣDDTs was only positively correlated with precipitation and population density (p<0.05). The degradation of DDT in soil occured from primary stage to high stage. The possible degradation pathways involved in DDTs entering forest soil were preliminarily deduced. Firstly, the surrounding pollution sources volatilize DDTs from soils to the atmosphere through secondary emission. In this process, DDT was continuously transformed into DDE through photodecomposition. The atmosphere rich in DDTs were transported to the forest area and then into the forest surface soil through atmospheric dry and wet deposition. Then, DDT transported continuously accumulated and degraded in forest soil. In the alternation of anaerobic and aerobic process, the main degradation pathways are DDT→DDD→DDMU, DDT→dicofol+DBP, DDT→DDE→DDMU, DDMU→DDNU.

How to cite: Qu, C., Wang, R., and Sun, W.: The occurrence of dichlorodiphenyltrichloroethanes (DDT) and its metabolites in Chinese forest soils: Implications for sources and environmental processes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13317, https://doi.org/10.5194/egusphere-egu23-13317, 2023.

Sediments act as a sink and a secondary source of contaminants, accounting for a central part of coastal and marine biogeochemical cycles. Phosphorus (P) is a macronutrient that governs primary productivity and phytoplankton growth, but excess P influx results in algae bloom and deteriorates aquatic ecosystems. This study assesses seasonal fluctuations, spatial distribution and fractions of P in the sediments of the southern Caspian Sea. In this study, at eight sampling points, composite samples of the surface (from 0 to 10 cm) seabed sediments were collected at 10 and 30 m water depths. The sampling campaigns were carried out in the four seasons and a total of 64 sediment samples were obtained. Total organic matter (TOM), total P (TP) concentration and particle size distribution were determined. Then, P was fractionated using a four-step sequential procedure to quantify the loosely bound P (LP), the reductant soluble P (FeP), the metallic oxide-bound P (AlP) and the calcium carbonate (CaCO₃) bound P (CaP). The inorganic P (IP) pool refers to the sum of LP, FeP, AlP and CaP, while the organic P (OP) was calculated by subtracting IP from TP.

The results show that seasonal fluctuations of mean TP were statistically insignificant (p-value > 0.05). Still, the highest levels were recorded in autumn (1555 mg kg^-1), followed by winter (1405 mg kg^-1), spring (1378 mg kg^-1) and summer (1130 mg kg^-1). These minor temporal variations in P levels are associated with the seasonal differences in the amount of runoff and the intensity of rivers discharging into the Caspian Sea, and thereby their sediment load and the physicochemical characteristics. The large riverine influx resulted in TP contamination hotspots in the river deltas of Anzali wetland, Babolrood and Sefidrud (northern Iran), where high loadings of suspended particles are discharged into the sea. The spatial TP distribution is thus site-specific and uneven. The main P fraction was CaP, reflecting the phosphate (PO₄^3-) strong affinity for, and association with, calcium-bearing minerals. Only a minor fraction of P was determined as LP. The fraction of the mud-size particles was the main explanatory factor for the spatial distribution of overall low levels of non-residual (or bioavailable) P forms (i.e., LP, FeP and AlP) during spring and summer, while the sand fraction had the greatest explanatory value for the distribution of residual (non-bioavailable) P form (CaP) during autumn and winter. This study demonstrates that P bioavailability in sediments is mostly controlled by the physicochemical characteristics of the sediment material, which again is steered by seawater chemistry. A low content of bioavailable P fractions could therefore be related to the relatively low content of fine-grained (i.e. below 63 µm) particles in sediments of the southern Caspian Sea.

How to cite: Ebrahimi, P., Nematollahi, M. J., Nasrollahzadeh Saravi, H., Vogt, R. D., Vahedi, F., and Baloei, M.: Spatio-temporal variations of phosphorus (P) fractions in surface sediments of the southern Caspian Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15671, https://doi.org/10.5194/egusphere-egu23-15671, 2023.

This study reports on the unique results of the recently concluded Sediment-quality Information, Monitoring and Assessment System to Support Transnational Cooperation for Joint Danube Basin Water Management (SIMONA) project, the largest of its kind in Europe, which was carried out in 2018-2022 as a project of the EU DTP aiming at delivering a ready-to-deploy sediment-quality monitoring system for the effective and comparable measurements and assessment of sediment quality in surface waters in the Danube River Basin in accordance with the EU Water Framework Directive (WFD). The project has developed, tested, demonstrated an innovative environmental geochemical monitoring platform of fluvial (suspended, river bottom and floodplain) sediments using state-of-the-art automated and passive sampling technology for the contamination risk assessment according to the EU WFD in the Danube Basin. Time series analysis and signal processing of one year multi-variate and multi-matrice monitoring data could be used to identify the geochemical background, temporal trends, periodicities and contamination events in the studied EU-defined Hazardous Substances. Since the applied technology, methods and data interpretation is fully consistent with EU legislation risk assessment, results may provide a ‘best solution’ for the spatial and temporal discrimination of contamination. Results of biological contamination assessment of sediments using microbial tests are also presented.

Keywords: data analysis, geochemistry, mobility, speciation, enrichment, time series analysis

How to cite: Kovács, Z., Jordán, G., Szabó, P., and Bálint, M. and the SIMONA Project Team: Development, data modelling of environmental geochemical monitoring of fluvial (suspended, river bottom, floodplain) sediments using unique automated and passive sampling for the contamination risk assessment according to the EU WFD in the Danube Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15997, https://doi.org/10.5194/egusphere-egu23-15997, 2023.

How to cite: Guarino, A., Pacifico, L. R., Iannone, A., Gramazio, A., and Albanese, S.: Assessing the soil baseline values of a geologically complex territory: the case study of Basilicata region., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16075, https://doi.org/10.5194/egusphere-egu23-16075, 2023.

The line of research on potentially toxic elements (PTEs) is of growing interest to the scientific community for protecting society against adverse health issues. The Campi Flegrei caldera in southern Italy is an active volcanic area where above two million people live, making it an ideal study area for investigating PTEs of natural and anthropogenic origin through the latest advances in geochemical data analysis. Therefore, a total of 394 topsoil samples (0 to 15 cm) were collected for determining the “pseudo-total” concentrations of elements in the <2 mm fraction using a combination of inductively coupled plasma-atomic emission spectrometry (ICP-AES) and inductively coupled plasma-mass spectrometry (ICP-MS), following aqua regia digestion.

The median values show that concentrations of Zn, Cu, Pb, V and As are greater (>10 mg/kg) than Cr, Co, Ni, Tl, Sb, Se, Cd and Hg. The geochemical maps generated by the Empirical Bayesian Kriging interpolation technique indicate that the higher concentrations of Pb, Zn, Cd, Cr, Hg, Ni and Sb are related to the greater population density (>6500 persons per Km²) in the urban area, but the elevated levels of As, Tl, Co, Cu, Se and V are observed in the other parts. In the context of compositional data analysis, the correlation diagram and robust principal component analysis detected: (1) the Pb–Zn–Hg–Cd–Sb–Cr–Ni association that likely shows anthropogenic activities such as heavy traffic load and fossil fuel combustion in the urban area; (2) the Al–Fe–Mn–Ti–Tl–V–Co–As–U–Th association that mostly represents the contribution of pyroclastic deposits; and (3) the Na–K–B association that probably reveals the weathering degree.

To choose the PTEs with potential health risks for the local inhabitants, the PTE quantities in soil are compared with the corresponding contamination thresholds established by the Italian legislation for residential land use. The Tl, Pb and Zn contents exceed the threshold in more than 15% of the collected samples, but Tl which derives from a natural source (e.g., leucite) is culled before evaluation. Then, children (0-6 years old) are considered for health risk assessment because: (1) Pb has significant adverse health effects in children; and (2) the more frequent hand-to-mouth behavior in children under 6 years old is linked to the higher chance of exposure. The probabilistic health risk modeling for the children <6 years old highlights negligible (hazard quotient below 1) Pb and Zn non-carcinogenic risk and unexpected (cancer risk ≤1E-06) Pb carcinogenic risk for exposure through soil ingestion. However, for the inhalation pathway, the children aged <1 year old have the highest chance (90%) of acceptable (i.e. from 1E-6 to 1E-4) Pb carcinogenic health risk. This should not be overlooked because Naples is under high environmental pressure and previous studies reported increased Pb and Zn quantities in soil between 1974 and 1999. Overall, the results of geostatistical interpolation, compositional data analysis and probabilistic health risk modeling potentially uncover the link between soil geochemistry and human health in densely populated active volcanic areas.

How to cite: Albanese, S., Ebrahimi, P., Aruta, A., Cicchella, D., Matano, F., De Vivo, B., and Lima, A.: Potentially toxic elements (PTEs) in the soils of a densely populated active volcanic area: the Campi Flegrei case study in Italy., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16151, https://doi.org/10.5194/egusphere-egu23-16151, 2023.

In the last few years Sr isotope geochemistry has contributed substantially to environmental and food traceability research. This is achievable because soils, plants and waters all have a peculiar Sr isotopic signature (⁸⁷Sr/⁸⁶Sr) inherited from the local geological substratum and affected by geological processes as well as the age and initial rubidium concentration of the rocks. Strontium ions released from the bedrock by weathering processes deriving by the interaction of circulating fluids with rocks, enter the environment and accumulates in water and soils. This reservoir of bioavailable Sr may represent a reliable tracer useful to determine the geographical origin of wines as it is known that strontium is taken first by plant roots, then by grapes, and lastly by wine, with no isotope fractionation when compared to the original ⁸⁷Sr/⁸⁶Sr ratio in the soil and rocks. As a result, the study of the Sr isotope ratio in the final product (wine) links directly to its geological origin thus representing a specific geofingerprint for any selected wine. Based on these premises this work aims at confirming the strong link between the product (wine) and its territory, with the final purpose to make it recognizable and distinguishable from similar products and protecting it from possible fraud and adulteration. In this work the ⁸⁷Sr/⁸⁶Sr systematics has been used to analyze a total of 39 samples (37 soil samples and 2 wine samples) from Campania (Italy). For a better understanding, both total Sr fraction and bioavailable Sr fraction were analyzed in soil samples (rhizospheric soils, bulk soils and samples collected from different horizons) in order to better investigate the environmental processes involved during the wine production cycle.

How to cite: Tranfa, P., Mercurio, M., D'Antonio, M., Di Renzo, V., Guarino, C., Sciarrillo, R., Zuzolo, D., Izzo, F., Langella, A., and Cappelletti, P.: 87Sr/86Sr as an efficient tool to investigate environmental processes in winemaking: a Campania (Italy) case study., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16341, https://doi.org/10.5194/egusphere-egu23-16341, 2023.

Life evolution has been shaped by marine and continental environmental dichotomy. Particularly, the ecological history of vertebrates is divided into several aquatic and terrestrial phases. Even today, some species spend time in both marine and continental environments during their lifetime. Nevertheless, the timing and location of past ecological transitions, as well as the monitoring of current migration, are still challenging to trace.

To reconstruct the aquatic environments of vertebrates (i.e. seawater vs freshwater), stable (δ¹³C, δ¹⁸O, δ³⁴S) and radiogenic (⁸⁷Sr/⁸⁶Sr) isotope systems applied to mineralized tissues have been commonly used in the past decades^1–6. Nevertheless, these methods hold some limitations as they cannot be applied universally.

Here, we measured the lithium stable isotope composition of mineralized tissues (δ⁷Li) from extant vertebrates living in various aquatic environments (seawater, freshwater/terrestrial, and "transitional environments”). We highlight the potential of δ⁷Li to decipher vertebrates that live in these different environments, in contrast to δ³⁴S and δ¹⁸O that cannot distinguish – in some cases – species living in intermediate waters from those living in seawater. Furthermore, we measured the δ⁷Li values of fossil apatites from extinct vertebrates and obtained values that fall within the range of aquatic environment of their extant relatives⁷. This new proxy may therefore profit studies in ecology, archaeology and palaeontology.

¹ M. T. Clementz, A. Goswami, P. D. Gingerich and P. L. Koch, Journal of Vertebrate Paleontology, 2006, 26, 355–370.

²  J. Fischer, S. Voigt, M. Franz, J. W. Schneider, M. M. Joachimski, M. Tichomirowa, J. Götze and H. Furrer, Palaeogeography, Palaeoclimatology, Palaeoecology, 2012, 353–355, 60–72.

³ J. Goedert, C. Lécuyer, R. Amiot, F. Arnaud-Godet, X. Wang, L. Cui, G. Cuny, G. Douay, F. Fourel, G. Panczer, L. Simon, J.-S. Steyer and M. Zhu, Nature, 2018, 558, 68–72.

⁴ J. Goedert, R. Amiot, D. Berthet, F. Fourel, L. Simon and C. Lécuyer, Sci Nat, 2020, 107, 10.

⁵ L. Kocsis, A. Ősi, T. Vennemann, C. N. Trueman and M. R. Palmer, Palaeogeography, Palaeoclimatology, Palaeoecology, 2009, 280, 532–542.

⁶ B. Schmitz, S. L. Ingram, D. T. Dockery and G. Åberg, Chemical Geology, 1997, 140, 275–287.

⁷ F. Thibon, J. Goedert, N. Séon, L. Weppe, J. E. Martin, R. Amiot, S. Adnet, O. Lambert, P. Bustamante, C. Lécuyer and N. Vigier, Earth and Planetary Science Letters, 2022, 599, 117840.

How to cite: Thibon, F., Goedert, J., Séon, N., Weppe, L., Martin, J. E., Amiot, R., Adnet, S., Lambert, O., Bustamante, P., Telouk, P., Lécuyer, C., and Vigier, N.: Lithium isotopes potential in (paleo)ecology, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1093, https://doi.org/10.5194/egusphere-egu23-1093, 2023.

Silver isotopic fractionation(s) during metallurgical processes (or other high-T processes) and its fate in mining- and smelter-affected environments, Ag-contaminated soils/sediments remain entirely unknown. Regarding the Ag-ore processing (roasting/smelting technologies), it can be assumed that, similarly to other isotopic systems (e.g., Tl and Cu), the isotopically lighter Ag (enriched in ¹⁰⁷Ag) enters the smelter emissions (fly ash), and isotopically heavier Ag (enriched in ¹⁰⁹Ag) remains in the residual metal phase. Our preliminary data from the Ag-contaminated soils around a former primary Ag-smelter at Příbram (Czech Rep.) indicate an apparent variability of ε¹⁰⁹Ag within soil profiles. The identified ε¹⁰⁹Ag values presented for the forest soil profile (Fig. 1) recorded ~0 in the organic horizon (O), ~0-+1 in the organo-mineral horizons (A1 and A2), and up to +7 in the mineral horizon (B). This finding suggests both the isotopically-lighter Ag fraction present in the topsoil (Fig. 1), as well as enhanced ¹⁰⁷Ag release during high-T smelting operations, i.e., relative to geogenic Ag (local ore). However, the question that clearly remains to date is to which degree the alteration/chemical processes in soil could have produced the Ag isotopic fractionation and which type of mechanisms (e.g. Ag(I)→Ag⁰) could represent the key geochemical controls.

Fig. 1 An example of vertical evolution of Ag isotopic signatures (ε¹⁰⁹Ag, relative to the NIST SRM 978a Ag standard) and Ag concentrations in a forest soil profile, ~1 km away from a former primary Ag-smelter (Příbram, Czech Rep.). The Ag isotopic data are assigned an estimated error of ±0.7 ε¹⁰⁹Ag (2sigma), which is based on our long-term reproducibility of multiple separate analyses (n = 6) of NIST SRM 2782 (Industrial Sludge) (Vaněk et al., unpublished data).

How to cite: Vaněk, A., Vaňková, M., Mihaljevič, M., and Ettler, V.: Silver stable isotopic ratios determined in contaminated soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2055, https://doi.org/10.5194/egusphere-egu23-2055, 2023.

Anammox plays a pivotal role in both natural and engineered systems as a process that simultaneously converts fixed nitrogen to N₂ and regenerates NO₃^–. In aquatic and terrestrial ecosystems, isotopic measurements, especially of the NO₃^– pool, provide an essential constraint on the processes that regulate the supply and elimination of fixed nitrogen, but the isotope effects of anammox remain poorly constrained.

We present measurements of the δ¹⁵N and δ¹⁸O of NO₃^–, NO₂^–, and NH₄⁺ as processed by anammox in a mixed microbial community enriched for N removal from wastewater. We find that oxygen isotope effects expressed in NO₂^– include a substantial contribution from equilibration reactions with water superimposed on kinetic isotope effects. Equilibrium between water and NO₂^– during processing by anammoxis greatly accelerated above rates observed under abiotic conditions even during growth phases when NO₂^– is rapidly being consumed. In turn, δ¹⁸O of NO₃^– nearly completely reflects the incorporation of O atoms derived from water with little additional isotopic fractionation. The δ¹⁵N values of NO₃^– and NO₂^– also show evidence for an equilibrium isotope exchange reaction between these molecules, which raises the possibility that nitrite oxidation is partially reversible, while introducing a high degree of variability into the δ¹⁵N of NO₃^– generated by anammox. Finally, variation observed in the δ¹⁵N of NH₄⁺ consumed by anammox can be connected to physiological limitations within the anammox cell.

Despite this complexity, we were able to use NO₂^– and NO₃^– isotope measurements to diagnose changes in the activity of anammox and related processes within the wastewater treatment system during a low-temperature perturbation experiment. These results provide new constraints for interpreting the variability in δ¹⁵N and δ¹⁸O of NO₃^–in natural systems, with implications for estimating relative rates of fixed N turnover processes.

How to cite: Magyar, P., Hausherr, D., Niederdorfer, R., Huang, K., Mohn, J., Bürgmann, H., Joss, A., and Lehmann, M.: Equilibrium and kinetic controls contribute to nitrogen and oxygen isotope effects during anammox in a wastewater treatment system, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4677, https://doi.org/10.5194/egusphere-egu23-4677, 2023.

The isotopic composition of nitrous oxide (N₂O) reveals valuable information on the biological production sources that contribute to N₂O accumulation in the atmosphere, i.e. denitrification, nitrifier-denitrification and nitrification¹. Isotopic fingerprints for each of these microbial pathways have been identified in past work, however, overlapping signatures of co-occurring N₂O production processes², and limitations in the robustness of associated fractionation factors under varying growth/environmental conditions³ still pose significant challenges.

We will present data from the initial phase of our project, where we study N₂O production and associated N and O isotopic fractionation by the denitrifier Pseudomonas aureofaciens, grown in the laboratory under different growth conditions and thus different reaction kinetics. N₂O production was quantified on-line by Fourier-Transformation IR-spectroscopy (FTIR), and the isotopic composition of produced N₂O was determined by quantum cascade-laser-absorption spectroscopy (QCLAS). The combination of N₂O production and isotope data (continuously measured) allowed us to elucidate changes in N and O isotope fractionation in response to changing reaction kinetics.

In a later phase of the project, we will expand our isotope-analytical capability by including also the doubly-substituted molecules of N₂O, ¹⁵N¹⁵N¹⁶O (556), ¹⁴N¹⁵N¹⁸O (458) and ¹⁵N¹⁴N¹⁸O (548). More specifically, we will interrogate the symmetry of N – N bond formation, verify combinatorial effects during N₂O production, and we will test whether Δ556, Δ458, and Δ548 (and the preference for ¹⁵N substitution in the central/terminal N-position) can be applied as proxies for reaction kinetics^{4, 5}.  

¹ Yu, L., Harris, E., Lewicka Szczebak, D., Barthel, M., Blomberg, M.R., Harris, S.J., Johnson, M.S., Lehmann, M.F., Liisberg, J., Müller, C. and Ostrom, N.E., 2020. What can we learn from N₂O isotope data?–Analytics, processes and modelling. Rapid Communications in Mass Spectrometry, 34(20), p.e8858.

² Kantnerová, K., Tuzson, B., Emmenegger, L., Bernasconi, S.M. and Mohn, J., 2019. Quantifying isotopic signatures of N₂O using quantum cascade laser absorption spectroscopy. Chimia, 73(4), pp.232-232.

³ Haslun, J.A., Ostrom, N.E., Hegg, E.L. and Ostrom, P.H., 2018. Estimation of isotope variation of N₂O during denitrification by Pseudomonas aureofaciens and Pseudomonas chlororaphis: implications for N₂O source apportionment. Biogeosciences, 15(12), pp.3873-3882.

⁴ Yeung, L.Y., 2016. Combinatorial effects on clumped isotopes and their significance in biogeochemistry. Geochimica et Cosmochimica Acta, 172, pp.22-38.

⁵ Kantnerová, K., Hattori, S., Toyoda, S., Yoshida, N., Emmenegger, L., Bernasconi, S.M. and Mohn, J., 2022. Clumped isotope signatures of nitrous oxide formed by bacterial denitrification. Geochimica et Cosmochimica Acta, 328, pp.120-129.

How to cite: Chénier, N., Magyar, P. M., Emmenegger, L., Lehmann, M. F., and Mohn, J.: Fractionation of nitrogen and oxygen isotopic composition in N2O produced by bacterial denitrification, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5210, https://doi.org/10.5194/egusphere-egu23-5210, 2023.

Microbially mediated iron (Fe) reduction is suggested to be one of the earliest metabolic pathways on Earth and Fe(III)-reducing microorganisms might be key inhabitants of the deep and hot biosphere [1, 2]. Since microbial Fe cycling is typically accompanied by Fe isotope fractionation, stable Fe isotopes (δ⁵⁶Fe) are used as tracer for microbial processes in modern and ancient marine sediments [3, 4]. Here we present Fe isotope data for dissolved and sequentially extracted sedimentary Fe pools from subseafloor sediments that were recovered during International Ocean Discovery Program Expedition 370 from a 1,180 m deep hole drilled in the Nankai Trough off Japan where temperatures of up to 120°C are reached at the sediment-basement interface. The expedition aimed at exploring the temperature limit of microbial life and identifying geochemical and microbial signatures that differentiate the biotic and abiotic realms [5, 6]. Dissolved Fe (Fe(II)_aq) is isotopically light throughout the ferruginous sediment interval but some samples have exceptionally light δ⁵⁶Fe values. Such light δ⁵⁶Fe values have never been reported in natural marine environments and cannot be solely attributed to microbially mediated Fe(III) reduction. We show that the light δ⁵⁶Fe values are best explained by a Rayleigh distillation model where Fe(II)_aq is continuously removed from the pore water by diffusion and adsorption onto Fe (oxyhydr)oxide surfaces. While the microbially mediated Fe(II)_aq release has ceased due to an increase in temperature beyond the threshold of mesophilic microorganisms, the abiotic diffusional and adsorptive Fe(II)_aq removal continued, leading to uniquely light δ⁵⁶Fe values. These findings have important implications for the interpretation of Fe isotope records especially in deep subseafloor sediments.

References:

[1] Vargas, M. et al., 1998. Nature 395: 65-67.

[2] Kashefi, K. and Lovley, D.R., 2003. Science 301: 934-934.

[3] Beard, B.L. et al., 1999. Science 285: 1889-1892.

[4] Anbar, A.D. and Rouxel, O., 2007. Annu. Rev. Earth Planet. Sci. 35: 717-746.

[5] Heuer, V.B. et al., 2017. In Proc. IODP Volume 370.

[6] Heuer, V.B. et al., 2020. Science 370: 1230-1234.

How to cite: Köster, M., Staubwasser, M., Meixner, A., Kasemann, S. A., Manners, H. R., Morono, Y., Inagaki, F., Heuer, V. B., Kasten, S., and Henkel, S.: Uniquely low stable iron isotopic signatures in deep marine sediments caused by Rayleigh distillation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6603, https://doi.org/10.5194/egusphere-egu23-6603, 2023.

Optimized slurry management targeted to increase nitrogen use efficiency (NUE) can be fundamental for limiting fertilizer N losses from agricultural grasslands causing eutrophication of ground- and surface water as well as air pollution. However, a holistic assessment of both agronomic and environmental impacts including key soil functions is still missing. This study aims to provide such information by assessing the impacts of traditional vs. modern slurry application techniques on NUE, hydrological and gaseous N losses, productivity and fodder quality, soil organic nitrogen formation and total N balances.  In a plot-scale grassland experiment ¹⁵N enriched slurry was applied after the first cut in early summer. The application treatments included: (1) traditional slurry broadcast spreading under dry weather; (2) application like (1) followed by a heavy rainfall event to increase slurry infiltration into soil; (3) broadcast spreading of slurry diluted with water; (4) injection of slurry into soil via shallow slits; and (5) injection of slurry into soil via deep slits. Variant (4) and (5) represent modern trailing shoe injections requiring extensive machinery. Fates of fertilizer N such as plant uptake, immobilization in soil and microbial biomass as well as NO₃ leaching were investigated by ¹⁵N tracing approaches in order to create full N balances. For this, biomass harvest and soil sampling were conducted after a growth period of 2 months. Here, we will present first results of our work that are expected to provide highly relevant decision support for grassland management. 

How to cite: Floßmann, S., Lei, K., van Grinsven, S., Völkel, J., Kögel-Knabner, I., and Dannenmann, M.: Effects of different slurry application techniques on Nitrogen Use Efficiency (NUE) in an extensive grassland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7883, https://doi.org/10.5194/egusphere-egu23-7883, 2023.

Measuring soil dinitrogen (N₂) emissions is notoriously challenging under field conditions. Hence, N₂ emissions represent a significant uncertainty in the nitrogen mass balance of terrestrial ecosystems. The ¹⁵N gas flux (¹⁵NGF) method is the only method currently available for directly quantifying N₂ emissions in situ. However, this method has rarely undergone independent validation under field conditions. In this study, our objectives were to: (1) Quantify N₂ emissions and their role in the fertilizer N mass balance of a wheat rotation using the ¹⁵NGF method (2) Verify the obtained quantities of N₂ emissions using a mass balance approach and (3) Verify the temporal N₂ emission dynamics at the soil-atmosphere interface using vertical soil profiles of ¹⁵N₂ enrichment.

To achieve these objectives, we grew winter wheat in lysimeters and applied ¹⁵N enriched mineral fertilizers via fertigation in three doses (sum 170 kg N ha^-1). We then analyzed gaseous (NH₃, N₂O, N₂) and hydrological N losses, as well as fertilizer N fates in plant and soil, and ¹⁵N₂ enrichment in soil air.

Our results showed that N₂ emissions directly measured using the ¹⁵NGF method amounted to 30 ± 4 kg N ha^-1, which was equivalent to 18 ± 3 % of the applied fertilizer N. These measurements agreed with unrecovered fertilizer N obtained from the ¹⁵N fertilizer mass balance, although the latter had large inherent uncertainty (21 ± 21 kg N ha^-1). N₂O emissions, however, were negligible (0.14 ± 0.02 kg N ha^-1). The temporal variability of measured N₂ emissions after fertilizer additions was generally well explained by ¹⁵N₂ enrichment in soil gas.

Overall, we provide independent validation of the ¹⁵NGF method in measuring N₂ emissions in the field and highlight the significant role of these emissions in the nitrogen balance of crop systems. Our data also suggest that soil gas measurements in combination with diffusion modeling could serve as an alternative method for quantifying N₂ emissions. These results should encourage a wider application of the ¹⁵NGF method in order to improve our understanding of N₂ emissions and reduce the current uncertainties in estimates of these emissions.

How to cite: Yankelzon, I., Schilling, L., Wrage-Moennig, N., Tenspolde, A., Ostler, U., Butterbach-Bahl, K., Hartl, L., Gasche, R., Matson, A., Well, R., Scheer, C., and Dannenmann, M.: Lysimeter-based full N balance as a tool to test field N2 flux measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8103, https://doi.org/10.5194/egusphere-egu23-8103, 2023.

How to cite: Barker, S., Preece, C., Berstan, R., and Seed, M.: Analysis of dissolved nitrate stable isotopes using the one-step Ti (III) reduction method and Elementar EnvirovisION System  , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8338, https://doi.org/10.5194/egusphere-egu23-8338, 2023.

The flow path of a river draining a lowland in the southern Baltic Sea, the Warnow River, was investigated to evaluate its freshwater composition as a source of dissolved substances to regional coastal waters. A spatial study was carried out once to follow the variations from the source to the estuary. A temporal study in the composition as a function of the season, during 6 years (2017-2022), was carried out at a site just before the river reaches the estuary. Surface water was sampled to analyze major and tracer elements, stable (H, C, O, S), and unstable (Ra) isotopes. The results show that the composition of the Warnow River along the flow path is controlled by a complex interplay between in-situ processes, exchange with the atmosphere, diffuse groundwater, and surface water inlets. On a temporal scale, pH, nutrient, and redox sensitive trace element concentrations are strongly impacted by pelagic primary production in spring. During summer and autumn, influences occurred by benthic microbial activity, associated diffusive release from soils/sediments, and surface water inlets. Throughout the investigation period, the Warnow River was a source of isotopically light CO2 to the atmosphere and DIC to the estuarine waters. The delivered DIC concentrations seem to vary with the season due to changes in biological pelagic and benthic activity. DOC was derived from a mixture of C3 organic sources and fertilizers. From concentration-discharge relationships, examples of dilution, mobilization, and chemostasis trends were found. Discharge-controlled seasonal trends are superimposed by system-internal processes and the hydrological consequences of river and drainage management. Our analysis thus provides new insights into the controls on the variations of water and solutes in a managed river at the land-sea interface as part of the regional hydrological cycle of a lowland catchment coastal water system.

The study was supported by the DFG research training group BALTIC TRANSCOAST, DAAD ,  and the BMBF project CARBOSTORE/COOLSTYLE

How to cite: Böttcher, M. E., Ehlert von Ahn, C. M., Malik, C., Westphal, J., Rach, B., Nantke, C., Jenner, A.-K., Saban, R., Winde, V., and Schmiedinger, I.: Temporal and spatial variations in the isotope hydrobiogeochemistry (H, C, O, S, Ra) of a managed river draining a lowland towards the Baltic Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9366, https://doi.org/10.5194/egusphere-egu23-9366, 2023.

How to cite: Jones, D., Groff, D., and Beilman, D.: The influence of high evaporative conditions on peat-forming mosses in the Antarctic Peninsula, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10139, https://doi.org/10.5194/egusphere-egu23-10139, 2023.

The sulfur (S) cycle is directly linked to the global carbon and iron cycles. Sulfur plays an important role in the preservation of organic matter (OM) over geological time scales. Assimilatory and dissimilatory sulfate reductions (ASR and DSR, respectively) are the main processes shaping the sulfur cycle and carry different sulfur isotopic fractionation (-1 to -3 ‰, and -20 to -75 ‰, respectively). The reduced S species produced by DSR react during early diagenesis with OM (sulfurization) to form organic-S, and/or with iron (Fe) to form pyrite. Although in most cases organic- and pyritic-S have a common origin (i.e., DSR), organic-S in marine sediments is typically ³⁴S enriched relative to its co-existing pyrite by up to 40 ‰ (global average is ~10‰). This isotopic difference is assumed to depend on specific paleo-environmental conditions and different sulfurization pathways (open-closed system for sulfate, Fe availability, redox state, OM type, etc.). Different sulfurization pathways may affect the type and distribution of S-bonds in sedimentary OM and thus can strongly affect the structure and character of sedimentary OM.

Recently, new instrumentations and methods were developed for the rapid determination of organic- and pyritic-S concentrations and δ³⁴S values using a Rock-Eval analyzer (RE) coupled to a MC-ICPMS. A new parameter, Tmax-S (the temperature at maximum peak of organic-S generation), was suggested to represent the organic-S thermal stability in pyrolysis conditions. Applying this parameter to thirteen organically rich and thermally immature samples of various geological settings and paleo-environmental origins revealed several interesting empirical correlations. The Tmax-S value was found to differ among the rocks and to linearly correlate (R²=0.98) with the percentage of pyrolyzed organic-S out of the total organic-S in the rock. Moreover, Tmax-S was strongly correlated with the distribution of sulfidic and thiophene compounds in the rock (R²=0.87). This suggests that Tmax-S may be used as a tool to evaluate the distribution of different S-bonds in the organic molecule, and, as a proxy, their sulfurization and paleoenvironmental conditions.

The rock samples' Tmax-S values also correlate with their isotopic difference between organic- and pyritic-S (Δ³⁴S_{organic-pyrite}; R²=0.76). The Δ³⁴S_{organic-pyrite} values of the rocks extended between 1 to 40‰ where marine samples characterized by low Tmax-S values (~400-450 °C) and large Δ³⁴S_{organic-pyrite} values (~20-40‰) and lacustrine samples by high Tmax-S values (~450-480 °C) and small Δ³⁴S_{organic-pyrite} values (~1-5‰). This correlation further supports the link between paleo-environmental conditions, specific sulfurization pathways, and the organic-S structures (represented by Tmax-S). It may shed light on some fundamental questions regarding the role of S isotopic distribution between pyrite and OM during deposition and diagenesis.

How to cite: Cohen-Sadon, H., Rosenberg, Y. O., Feinstein, S., and Amrani, A.: Development of new proxies for sulfurization and paleo-environmental conditions using a Rock-Eval coupled to MC-ICPMS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11001, https://doi.org/10.5194/egusphere-egu23-11001, 2023.

For decades, the search for terrestrial abiotic CH₄ has been a central quest in geology and astrobiology. Most of this research has focused on crustal fluid samples collected at surface seeps, hydrothermal vents, and wells. Nonetheless, in such open systems processes like mixing with shallow biotic CH₄, oxidation, and diffusion can lead to large uncertainties in the initial composition of deeply originated CH₄¹. Extracting natural CH₄ from fluid inclusions entrapped in minerals could overcome the effects of shallow contamination occurring in natural open systems and shed light on the origin of deep CH₄ in a wide variety of geodynamic settings^2,3.  

In this abstract, we present a novel approach for bulk off-line fluid inclusion extraction for the analysis of δ¹³C-CH₄ using a Cavity Ring-Down Spectroscopy (CRDS) analyzer (Picarro G2201-i). Two fluid extraction techniques were compared: ball milling in ZrO₂ jars and sample crushing in a stainless-steel sealed tube under a piston. The accuracy and precision of the different protocols was evaluated with blanks, CH₄ isotopic labelling and interlaboratory comparisons.   

Blanks and isotopically labelled tests with the ball milling technique suggested that milling speed, and duration, and sample mass and type may strongly affect the CH₄ concentrations and isotopic compositions measured by the CRDS analyser. These effects are mainly ruled by the blank production of CH₄ –demonstrated by gas chromatography analyses– and potentially other molecules induced by frictional heating. The blank gases may cause interference effects on the absorption bands detected by the CRDS analyser. This effect was marked by a large offset in the δ¹³C-CH₄ measured in the high-range analytical modes of the Picarro G2201-i. The magnitude of the interference was inversely correlated to the CH₄ concentration.Other processes such as CH₄ diffusion and adsorption may play a role in the observed changes in CH₄ concentrations and isotopic compositions. Experimental conditions involving high CH₄ concentrations and sample mass could well reproduce CH₄ isotopic composition. 

Crushing in a sealed stainless-steel tube produces lower blank levels compared to ball milling, nevertheless the crushing efficiency and CH₄ release is lower due to smaller rock sample size.   

The presented ball milling protocol provides a simple and fast way to extract and accurately analyse CH₄ hosted in fluid inclusions even if great care should be considered for samples with low CH₄ concentrations where contamination and interferences can potentially alter the CH₄ isotopic signature of natural samples.   

References 

• 1 - Young et al. (2017). 10.1016/j.gca.2016.12.041 
• 2 - Klein et al. (2019). 10.1073/pnas.1907871116 
• 3 - Grozeva et al. (2020). 10.1098/rsta.2018.0431 

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: Olivieri, O. S., Brovarone, A. V., Fiebig, J., Ressico, F., Marassi, V., Casolari, S., and Sissmann, O.: Exploring new protocols for bulk off-line fluid inclusion extraction for the analysis of δ13C-CH4 using a Cavity Ring-Down Spectroscopy (CRDS) analyzer., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12808, https://doi.org/10.5194/egusphere-egu23-12808, 2023.

Marine and lacustrine benthic habitats represent hotspots of nitrogen (N) turnover, with many N transformation processes occurring simultaneously, and at high rates. More specifically, sedimentary microbial reduction of nitrate to dinitrogen (N₂), and other modes of N₂ production (e.g., anammox), are the most important sinks of fixed N in aquatic environments. Natural abundance stable isotope ratio measurements can be employed to help disentangling N-loss mechanisms, given that the isotope effects (e) associated with each process are well studied.

In our study, we surveyed an array of lacustrine and marine benthic environments and assessed the isotopic composition (d¹⁵N and d¹⁸O) of porewater ammonium (NH₄⁺) and nitrate (NO₃^-) – the key substrates driving the various N transformation pathways, such as denitrification, anammox, nitrification and dissimilatory nitrate reduction to ammonium (DNRA). We further examined how benthic N isotope dynamics vary in different sedimentary regimes, with distinct organic matter (OM) mineralization rates. We expect the relative importance of the various N pathways to affect the NH₄⁺ and/or NO₃^- isotope pools differentially.

Our preliminary porewater d¹⁵N-NH₄⁺ results suggest a diverse pattern with regard to the isotope enrichments between oligotrophic lakes, characterized by relatively strong depth gradients, and eutrophic lakes, where no significant depth gradient was observed. We hypothesize that this distinction could be attributed to different organic N availability and/or anammox contributions in the surveyed environments. Furthermore, we compared rate measurements (based on ¹⁵N addition experiments) to the N and O nitrate isotopic signatures to quantify processes, such as denitrification and DNRA. To investigate N isotope fractionation within the narrow nitracline, we employed the whole-core squeeze method, which provided a high-resolution porewater NO₃^-profile. Using this method, we found that the calculated community nitrate consumption e values at the nitracline (e_{elim_porewater}) showed strong variability among the surveyed settings. We attribute such variation to shifts in the relative importance of denitrification versus DNRA and anammox between lakes of different trophic states. Overall, e_{elim_porewater} wasconsiderably below 25‰ – the value generally reported for the biological isotope effect of denitrification (e_denit).

How to cite: Mazzoli, A., Callbeck, C. M., Paulus, T. J., Frey, C., Zopfi, J., Katsev, S., Canfield, D. E., and Lehmann, M. F.: New insights into benthic nitrogen cycling using natural-abundance stable isotopes measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13490, https://doi.org/10.5194/egusphere-egu23-13490, 2023.

Migratory insects serve an important role to ecosystems and economies as they participate in the long-distance transfer of nutrients, pollen, and biomass. However, migratory insects are understudied, especially compared to birds and mammals, partially because traditional tracking techniques (e.g. mark-recapture, biologgers) are often ineffective for insects because insects are small, short-lived, and numerous. Thus, isotope geolocation has become an effective tool for studying dispersing insects. The painted lady butterfly (Vanessa cardui (L.)) is a virtually cosmopolitan species that was recently found to make regular, annual multi-generational migrations across the Sahara Desert. Previous work geolocating painted ladies with hydrogen isotopes has shown early spring migratory movements of painted ladies from sub-Saharan Africa to Mediterranean Europe and autumn movements to the sub-Sahara from Europe. However, these previous works using hydrogen isotopes were unable to offer refined estimates of natal origin due to the inherent limitations of the technique. Here, we update previous hydrogen isotope-based geographic assignment by (1) using an updated model of hydrogen isotope variations across the landscape (i.e., isoscape), (2) combining with strontium isotope-based geographic assignment, and (3) expanding the number of geolocated butterflies to include capture locations on both sides of the Sahara Desert across different years. Using this method, we spatially refine previous estimates of the natal origins of successful trans-Saharan migrants and estimate the distances that successful migrants travelled. Overall, this study demonstrates the advantages of combining hydrogen and strontium isotopes for the geographic assignment of migratory butterflies and further advances our understanding of long-distance insect migration.

How to cite: Reich, M., Ghouri, S., Zabudsky, S., Talavera, G., and Bataille, C.: There and back again: Combining hydrogen and strontium isotopes refines the trans-Saharan migratory patterns of the butterfly Vanessa cardui, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13891, https://doi.org/10.5194/egusphere-egu23-13891, 2023.

Silicate mineral weathering and the resulting formation of clay minerals are key processes at the Earth’s surface. Reverse weathering reactions regulate the evolution of ocean pH and chemistry, atmospheric carbon dioxide budget, soil formation and associated nutrient and element transfer within local and global biogeochemical cycles. A key element released during weathering processes is silicon (Si), that enters the biogeochemical cycle as dissolved silicic acid (Si(OH)₄ or DSi). During the transport of DSi through the hydro-, bio-, pedo- and lithosphere towards the ocean, DSi is involved in the formation of new silicate minerals (i.e., clay minerals) in particular in the critical zone (CZ). Here, DSi is frequently precipitating as gel-like, amorphous phases such as short range ordered hydroxyaluminosilicate phases (HAS: e.g., allophane) or as hydrous ferric silicates (HFS: e.g., hisingerite). These highly reactive minerals are known precursors to the formation of important soil clay minerals e.g., within the smectite group.

The individual reaction pathways and the environmental controls underlying HAS and HFS formation within the CZ are not yet well constrained. Si isotope fractionation throughout HAS and HFS formation is a key tool to decode and assess such enigmatic reaction mechanisms. Therefore, a series of allophane-hisingerite precipitation experiments has been performed to investigate Si isotope fractionation to potentially resolve mechanisms and conditions underlying the formation of HAS and HFS phases. Kinetic and equilibrium Si isotope fractionation between reactive fluid and solid phases are studied at high temporal resolution. Isotope exchange mechanisms are investigated using the three-isotope method, which is a novel proxy to trace the direction and the progress of low-temperature water-mineral/rock interactions.

How to cite: Stamm, F. M., Baldermann, A., Frick, D. A., Hippler, D., and Dietzel, M.: Unravelling the formation paths of amorphous hydroxyaluminosilicates and hydrous ferric silicates: Evidence from silicon isotopes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14655, https://doi.org/10.5194/egusphere-egu23-14655, 2023.

Plants in semi-arid environments have adapted to scarce nitrogen (N) resources by becoming more efficient at using and taking it up, or by relying on symbiotic organisms. Common mycelial/mycorrhizal networks (CMNs) may help plants access and assist to a spatio-temporal redistribution of resources in soil. While CMNs have been extensively investigated in temperate forests and grasslands, their importance in semi-arid environments is still uncertain. This study evaluates the existence and importance of CMNs in N translocation in semiarid environments, using Helianthemmum almeriense as the host plant mycorrhized with Terfezia claveryi. We hypothesize that the presence of CMNs is a response mechanism to N scarcity due to soil heterogeneity. Through this mechanism, host plants and mycorrhizal fungi provide redistribution of N, playing a determinant role at all spatial scales, from the facilitation of seedling establishment to the persistence and coexistence of different plant communities. To test our hypothesis, we designed a mesocosm that allowed only hyphae to cross into an adjacent compartment. Three different tests were used to assess the existence and directionality of CMN. In the first test (T1), an adult plant was labeled with ¹⁵N and on the other side, only unlabeled soil was present. In this way, we could check if the mycorrhizal fungus tends to homogenously distribute the ¹⁵N to places where there is no other plant. In the second test (T2) we had an adult plant and in the adjacent compartment, four-week-old seedlings that were already mycorrhized with mycelium coming from the compartment with the adult plant. In this case, the ¹⁵N marker was applied where the adult plant was located, and we checked whether there was a transfer of ¹⁵N to the seedlings. In T3, we used a set of mesocosms equal to T2, but this time ¹⁵N was applied on the side where the seedlings were located. The idea was to determine whether the distribution of the ¹⁵N was proportional to the size of the plant that could receive it. The three types of mesocosms were sampled before labeling (day 0), 7 and 14 days after labeling. Our results reveal that ¹⁵N translocation to adjacent compartments occurred in all three tests, but in significantly different amounts. The translocation of ¹⁵N was significantly higher in those tests where there was a plant in the adjacent compartment (Tests 2 and 3) compared to T1. We also found that the contribution (%) of ¹⁵N to the total plant N pool was significantly higher for one-month-old seedlings in both T2 and T3, compared to adult plants. Under controlled greenhouse conditions, we have shown that the mycelium seems to act as an effective hub for N translocation, but we have not found the amounts transferred under our experimental conditions to be nutritionally remarkable. Our results should be further evaluated under natural conditions, to verify whether this N transfer has a greater nutritional significance than that found under controlled conditions, and also whether this CMN may play a more important role in signaling between plants adapted to semi-arid regions.

How to cite: Andrino, A., Morte, A., Arenas, F., Figueiredo, A., Sauheitl, L., Navarro, A., Guarnizo, Á. L., Guggenberger, G., and Boy, J.: Determining the relevance of common mycelial networks in the nitrogen nutrition of plants adapted to semi-arid ecosystems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15191, https://doi.org/10.5194/egusphere-egu23-15191, 2023.

Water plays a key role in the colonization and ecology of microorganisms in natural subterranean environments since it controls their metabolic activity and the microbe-mineral interactions. In turn, microbial activity leaves its signature in groundwater. For instance, the aerial hyphae of Actinobacteria colonizing cave-rock surfaces and sediments act as vapour condensation nuclei and facilitate the retention of interstitial water in the porous system of rocks, sediments and speleothems.

Here, we present the results of exhaustive monitoring of cave waters from Pindal Cave (northern Spain), a shallow and well-ventilated cave on the coastline, with extensive microbial colonization on the sediments and walls surfaces. This study sheds light on the detection of biosignatures based on stables isotopes of cave waters and controlled by underground-dwelling microorganisms. The isotopic composition (d¹⁸O and dD) of seepage waters (fast drips, soda straws and gours) and condensation droplets were determined by cavity ring-down spectroscopy (CRDS). An analytical set-up based on a CRDS analyser coupled to an Induction Module enabled the step-heating of moonmilk deposits and other substrates with distinct degrees of microbial colonization, and the selective release of their interstitial water for isotope analyses.

The δ¹⁸O and δD values of the in-cave waters correlate linearly (δD=7.71·δ¹⁸O+12.28; R²=0.97), like the Local Meteoric Water Line (δD=7.00·δ¹⁸O+6.77; R²=0.92, based on the of isotopes composition of regional rain). The offset of d-excess between the cave waters and the LMWL would indicate a significant recharge by occult precipitation linked to local coastal fogs. The isotopic composition of dripping water,  -5.7‰ [-6.7 to -4.8 ‰] for  d¹⁸O and -31.3‰ [-39.0 to -22.7 ‰] for dD, agree with the water samples from the gours located far from the cave entrance, with some slight deviations indicating evaporation processes or sudden contributions of meteoric water due to flash-flood events.

The δ¹⁸O and δD values of condensation water collected from non-colonized surfaces are -5.4‰ [-5.9 to -4.5 ‰] and –28.4‰ [-32.9 to -21.3 ‰], respectively. This isotope composition is similar to the contemporary infiltration water, which suggests that condensation mostly comes from autochthonous vapour generated from in-cave waters. The Actinobacteria mats quickly absorb the condensation water and it is then retained during long periods on the rock surface. Thus, in the case of microbial induced deposits like moonmilk, condensate water becomes a reservoir of interstitial water exposed to isotopes fractionation linked to the microbial metabolism processes. Indeed, the δ¹⁸O and δD values of this interstitial water correlate linearly with the rest of the in-cave waters but show a distinctive composition with higher δ¹⁸O and δD values compared to the infiltration water and condensation droplets; -3.6‰ [-4.4 to -2.0 ‰] and –18.9‰ [-27.2 to -10.8 ‰], respectively. These findings lead to exploring the potential use of water isotopes as a tool for indirectly assessing microbial activity and its role in the water balances in underground ecosystems.

Research funded by PID2019-110603RB-I00 – SUBSYST and PID2020-114978GB-I00 projects

How to cite: Fernandez-Cortes, A., Martin-Pozas, T., Cuezva, S., Gazquez, F., Benavente, D., Cañaveras, J. C., Saiz-Jimenez, C., and Sanchez-Moral, S.: Isotopic tracking of condensation, infiltration and interstitial water to detect microbial activity in caves, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16065, https://doi.org/10.5194/egusphere-egu23-16065, 2023.

Soils from a coastal peatland (Drammendorf,  southern Baltic Sea) were investigated for the biogeochemical impact of flooding with brackish seawater. The peatland was rewetted in late 2019 through the partial removal of a dyke and brackish water with high sulfate concentration from a lagoon (Kubitzer Bodden) allowed to intrude into the peatland. Soil cores were retrieved about 2 and 3 years after the initial rewetting event. Pore waters were extracted from soil cores using rhizons and samples were analyzed besides physical parameters for major ions, nutrients, water stable isotopes, dissolved inorganic carbon (DIC) concentrations, and stable isotopes in C and S species. Solid phase samples were analyzed for contents of CNS and acid-extractable metal and nutrient species, and the stable isotope composition of acid-volatile sulfide (AVS), chromium-reducible sulfide (CRS, pyrite).Results from the post-event campaigns are compared with pre-flooding conditions. Poree water generally showed a trend towards freshening with depth as remains from the pre-flooding conditions. . Different sites are furthermore characterized by different amounts of diagenetically released dissolved inorganic carbon (DIC). A mixing evaluation of ẟ¹³C-DIC signatures together with major ion concentrations reveals potential DIC sources, like organic matter/methane oxidation, carbonate dissolution and mixing with seawater-derived DIC. DIC from the dissolution of minor soil carbonates may lead to a relative enrichment of ¹³C in DIC. Brackish water intrusion and cation exchange are reflected by the downward gradients in pore water compositions, with Na and Mg decreasing and Ca increasing with depth. Soil organic carbon is dominating with inorganic carbon being a minor fraction in most parts. Dissolved pore water sulfate and high total sulfur in the top soils with decrease downward trends further reflect the importance of post-event enhanced sulfur cycling leading to characteristic sulfur isotope signatures. AVS is depleted in the top soils with highest contents at about 5 cmbsf. Pyrite sulfur dominates and show different enrichment zones with the sediment columns. Contents in CRS contents covary with TOC, indicating that the benthic diagenetic system is controlled by organic matter availability, as in normal marine sediments.  The study demonstrates the role of electron acceptor availability for benthic carbon cycling, and the kinetics of biogeochemical interactions upon oxidation of reduced carbon, mineral authigenesis/dissolution, and ion exchange processes. The results of implications for coastal processes in the humid climate zone during times of increasing seawater level rise.

How to cite: Saban, R., Boettcher, M. E., Jenner, A. K., Anthony, S. E., Juransinski, G., Ehlert von Ahn, C., Roeser, P., and Schmiedinger, I.: Isotope biogeochemistry of the carbon-iron-sulfur cycle in a temperate coastal peatland after flooding by brackish seawater, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16235, https://doi.org/10.5194/egusphere-egu23-16235, 2023.

Estuaries are important biogeochemical reactors that can remove dissolved inorganic nitrogen (DIN, mostly nitrate) from the water column, but can also generate nitrate via remineralization and subsequent nitrification of organic matter in the water column. To assess this regeneration of nitrate, an important nutrient source for phytoplankton that contributes to eutrophication, various isotope-based laboratory methods are in use.

In this study, we compare two commonly used stable-isotope-based techniques to measure nitrification in estuarine water, the isotope dilution method and the addition of 15N-ammonium. Both measure the isotope enrichment in nitrate but have drastically different incubation times. We apply both methods in the estuary of the Elbe River and evaluate the drawbacks and advantages of each method to develop application recommendations.

Our results indicate that nitrification measurements using isotope dilution are less variable between stations, but suggest that rates are overestimated at high phytoplankton activity. On the counter side, the addition of 15N-ammonium as a tracer apparently overestimates nitrification in heterotrophic settings, probably because substrate addition stimulates nitrification. The adequate measurement technique must this be carefully chosen depending on the selected study site.

Funding information  - This study has been carried out and was financially supported by the BMBF “Blue-Estuaries” project (grant no. 03F0864C)

How to cite: Russnak, V., Kache, S., Voss, M., and Dähnke, K.: Comparison of two isotope-based methods to quantify nitrification rates in estuaries, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16361, https://doi.org/10.5194/egusphere-egu23-16361, 2023.

Aquatic sediments play a critical role in moderating the availability of fixed nitrogen (N) in the biosphere. Microbial N cycling processes, such as denitrification and anammox, contribute to fixed‑N removal as N₂ gas from lakes and the ocean. N‑isotopic measurements of dissolved inorganic N (e.g., nitrate (NO₃^-)) can provide insights into the different sources, sinks, and pathways of N, if the associated N isotope signatures/effects are constrained. While substantial work has been done to resolve N‑loss using microbial metagenomic‑based approaches and rate measurements, how nitrogen‑loss processes imprint natural‑abundance isotopes of ¹⁵N and ¹⁸O of NO₃^- remains largely understudied in freshwater lake sediments. Current marine evidence suggests that water column denitrification involves high NO₃^- isotope effects (>20‰). In contrast, the marine NO₃^- isotope effect of sedimentary denitrification is suppressed at the level of the sediment‑water interface (apparent N/O isotope effect, ε_app <5‰). How anammox affects ε_app in either marine or freshwater systems, is completely unknown. This study aims to achieve a deeper understanding of NO₃^- N and O isotope fractionation during benthic N transformation and sedimentary N‑loss (including anammox), and its ultimate expression in the water column of freshwater lakes. We also investigate how ε_app values may vary with environmental conditions (e.g., trophic state) that affect the reactivity and amount of organic matter in the sediments, as well as the balance between benthic N‑cycle reactions.

The two study sites Lake Baldegg (eutrophic) and Sarnen (oligotrophic), were chosen because of their contrasting trophic states. We conducted a suite of experiments with sediment cores collected at different times of the year to assess the sedimentary ε_app in these two lakes. More specifically, we carried out whole‑core incubations under oxic/anoxic conditions and examined the change ¹⁵N/¹⁴N and ¹⁸O/¹⁶O of NO₃^- with net NO₃^- depletion in the overlying water. We integrated natural‑abundance N and O isotope measurements with ¹⁵N‑label based N transformation‑rate measurements, to understand how the phenology and differential combination of the different N transformation pathways may modulate ε_app. We demonstrate that nitrification, DNRA, denitrification, anammox and organic matter remineralization overlap spatially in the sediments of Lake Sarnen. In contrast, these processes are, in parts, spatially decoupled in Lake Baldegg. Moreover, the relative importance of anammox versus denitrification is significantly greater in Lake Baldegg. In both lakes the net N isotope effect of sedimentary NO₃^- consumption is strongly underexpressed at the ecosystem level, with NO₃^-‑N ε_app values systematically below 4‰. In Lake Sarnen the NO₃^- N‑vs.‑O isotope signature followed a 1:1 trend, whereas in Lake Baldegg a systematically higher ratio was observed. This suggests that, while in Lake Sarnen, the NO₃^- N and O isotope signatures are dominated by NO₃^- reduction, NO₃^- regeneration (e.g., by nitrification or anammox) overprints the NO₃^- isotopic signature of net denitrification under the more eutrophic conditions in Lake Baldegg.

How to cite: Paulus, T. J., Mazzoli, A., Frey, C., Zopfi, J., Callbeck, C., and Lehmann, M. F.: The isotope effect of benthic N removal in two Swiss lakes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16727, https://doi.org/10.5194/egusphere-egu23-16727, 2023.

The Ivrea-Verbano Zone (IVZ) is the westernmost sector of the Southern Alps. It is constituted by granulite-to-amphibolite-facies continental crust representing the basement of the Adria plate. The IVZ contains many orogenic mantle peridotites. The largest mantle bodies are aligned along the Insubric Line at the lowest stratigraphic units, in contact with mafic-ultramafic crustal intrusives. Mantle bodies in the central and southern sectors of IVZ are spinel lherzolites with spinel dunites and variable amount of clinopyroxenite, websterite and subordinate anhydrous/hydrous gabbroic bodies (e.g. the Baldissero, Balmuccia, Premosello peridotites). Conversely, modally-metasomatised spinel harzburgites with large dunite bodies and phlogopite-and-amphibole-bearing websterites (e.g. the Finero peridotite) crop out in the northern IVZ.

The constant association of the IVZ mantle peridotites with High-T shear zones suggests that none of them was emplaced into the crust by mantle diapirism. Alternative hypotheses involve emplacement at the crustal level at the onset of the Mesozoic extensional regime or tectonic addition to accretionary wedges of Paleozoic subduction zones. Recent gravimetric and seismic data converge in indicating that high-density rocks are very close to the surface near the Insubric Line, thus supporting the possibility that the largest mantle peridotites may be a direct expression of the underlying subcontinental mantle.

This contribution focuses on new field, petrographic, geochemical and geochronological data, to address some relevant issues, such as the nature of the spinel lherzolite (refractory residue vs. refertilised mantle), the origin of pyroxenites and gabbros, the relationships with the associated crustal intrusives and the record of Mesozoic tectono-magmatic events.

The final goal is to provide new insights into the geodynamic evolution of the mantle bodies and the mantle-crust systems at the Laurasia-Gondwana margin, defining in particular how the mantle heterogeneity acquired during Paleozoic may have governed the rifting process of the Adria margin in Jurassic times.

How to cite: Ogunyele, A. C., Bonazzi, M., Sanfilippo, A., Decarlis, A., and Zanetti, A.: Reappraisal of the geodynamic evolution of the mantle massifs of the Ivrea-Verbano Zone based on new field, petrochemical and geochronological data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-243, https://doi.org/10.5194/egusphere-egu23-243, 2023.

Even though the southern Indian Dharwar craton hosts several kimberlites, lamproite, and lamprophyre fields of the Mesoproterozoic age, mantle-derived peridotitic xenoliths are very rare and are often highly altered and poorly preserved. Due to these constraints, xenolith-based direct mantle investigations have been limited beneath the Indian cratons. In this study, we report extensive geochemical analyses on peridotite xenoliths from the P3 kimberlite pipe of the Wajrakarur kimberlite field from the Eastern Dharwar craton (EDC). With the help of major and trace element compositions of the garnets and clinopyroxenes, this study aims to characterize the mantle below EDC and to comment on its evolution.

During this study, 57 peridotite xenoliths were identified. P-T estimates were carried out using garnet compositions. Based on the vertical distribution of garnets on a projected depth, it is observed that the upper part of the lithosphere is composed mostly of lherzolites(G9) with few harzburgites (G10), whereas the base of the lithosphere is dominated by Ti-Metasomatized garnets(G11).

Garnet compositions show an anomaly in the TiO₂ content, which is marked by a sudden increase in TiO₂ at ~160 km of depth. This depth coincides with an increased concentration of G11 garnets. Zr/Hf vs Ti/Eu plot for garnets shows that carbonatitic and kimberlitic fluids are involved in metasomatizing the SCLM. The Mg# and Cr# values suggest that the lithosphere gets more depleted with increasing depth. Clinopyroxene compositions show the presence of two types. Type 1 is enriched in LREE than the Type 2 clinopyroxenes showing the metasomatic enrichment.

The depth range of the studied peridotite xenoliths indicates sampling of the mantle from ~170 to 190 km of depth, indicating a 190 km thick LAB at 1.1 Ga. However, geophysical studies show a present-day estimate of a ~110 to 120 km thick lithosphere. This further indicates about 70-80 km of delamination of the lithospheric keel in post-Mesoproterozoic times. Such large-scale delamination of the lithosphere might be possible due to the increased frequency of mantle plumes, convective erosion, and the heavily metasomatized nature of the SCLM.

How to cite: Daimi, Z. and Dongre, A.: Evolution of the lithospheric mantle beneath Eastern Dharwar craton of Southern India: constraints from peridotite xenoliths from P3 kimberlite pipe of the Wajrakarur, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-293, https://doi.org/10.5194/egusphere-egu23-293, 2023.

The ability of xenoliths to preserve water lithospheric signatures remains an unsolved question for many years. We report water content in olivine and pyroxenes of peridotite xenoliths from Peylenc and Ray Pic volcanoes (French Massif central, FMC). On each site xenoliths were sampled from products of an explosive eruption (volcanic breccia and pyroclastic deposit) and an effusive eruption (frozen magma chamber and a lava flow).

In Peylenc, the xenoliths from the breccia have systematically more water than the xenoliths from the basalt quarry: ol 1-9, opx 60-95 and cpx 250-380 wt. ppm H₂O versus ol <0.2, opx 20-55 and cpx 110-240 wt. ppm H₂O.

In Ray Pic, water content in xenoliths from the lava flow is independent of its location in the lava: ol < 1, opx 190-270 and cpx 430-640 wt. ppm H₂O. Results suggest that the cooling and solidification of the lava had no impact on water content.

The xenoliths from the pyroclastic deposit have systematically more water: ol 3-12, opx 330-460 and cpx 810-890 wt. ppm H₂O. These values are either comparable with or lower than the values reported previously from the same locality¹.

The study shows that xenoliths recovered from explosive eruptions have higher water content than the ones from effusive eruptions, but also that water content can be different from one explosive event to another.

Conclusion is that water content can rapidly be reset during magma degassing prior to eruption. Degassing controls water content of xenoliths.

Among the xenoliths studied, several have spectral signatures different from others. This different spectral signature has also been reported from other volcanoes^{2, 3}. The coexisting of different spectral signatures, which have not been erased during degassing, are probably the only OH signatures fully preserved from depth.

¹ Azevedo-Vannson S.,et al. Chemical Geology 575 120257 (2021)

² Denis C.M.M. et al. Lithos 226 256-274 (2015)

³ Patkó L. et al. Chemical Geology 507 23-41 (2019)

How to cite: Ingrin, J., Thomaidis, K., and Drouka, M.: Preservation of the water concentration in mantle xenoliths. The cases of Peylenc & Ray Pic volcanoes (FMC), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2720, https://doi.org/10.5194/egusphere-egu23-2720, 2023.

The Khrami crystalline massif is located in the northern part of the Lesser Caucasus, in the Black Sea - Transcaucasian terrane. The massif outcrops Middle Paleozoic metabasites, which crosscut the Precambrian gneiss-migmatite complex and, in turn, are cut by Late Variscan granites. These metabasites have not experienced Precambrian prograde HT/LP (720-770°C, P<1.5 kbar) regional metamorphism, although retrograde LT/LP (T≈430-510⁰C, P≈0.6-1 kbar) metamorphism, associated with the Sudetian orogeny has been recorded. According to the presented geological data, the age of metabasites is within the Cambrian and Upper Paleozoic. Considering the analogy between the metabasites spread in the Dzirula crystalline massif, which is exposed in the same terrane, and the metabasites of the Khrami massif, the age of the latter is most likely Middle Paleozoic (Shengelia et al., 2022). The metabasites of the Khrami massif are represented by veins (1-60 m) and stock-shaped bodies (80-800 m) of fine-grained ophitic gabbro, gabbro-diabases and diabases of various thicknesses. They are cut by numerous granite veins and penetrated by thin quartz-feldspar injections. The paragenesis of the high-temperature magmatic stage - Cpx+Pl_78-84 has been preserved in metabasites in some places; Further, under the conditions of greenschist facies, the paragenesis Ab+Act(Tr)+Chl+Ep±Qz develops. According to the petrogenic diagrams Na₂O+K₂O – SiO₂, the metabasites of the Khrami massif belong to the formations of the subalkaline series (Irvine and Baragar, 1971), correspond to basalts and andesite-basalts (Le bas et al., 1986) and basalts and picrites (Cox et al., 1979). This is confirmed by the data of diagrams Zr/Ti-Nb/Y (Pearce, 1996) and Zr/TiO₂ – Yb/Y (Winchester, Floyd, 1977). According to the Na₂O+K₂O–FeO*-MgO (Irvine and Baragar, 1971), a great part of the metabasites is of tholeiitic composition, and only a small part is of calc-alkaline composition. On the diagram Fe*-SiO₂ (Frost et al., 2008) the dots denoting metabasites are completely disposed in the magnesian field. According to the TiO₂ - Zr/(P₂O₅*10⁴) diagram (Winchester, Floyd, 1976), the metabasites correspond to tholeiite basalts. According to the diagram V-Ti/1000 (Shervias, 1982), the metabasites belong to the MORB genetic formation, and according to the diagram Cr-Y (Pearce, 1982), they belong mainly to the VAB, and also to the MORB. According to the ratio MnO-TiO₂/10-P₂O₅ (Mullen, 1983), dots of mafic rocks are located in the island-arc tholeiitic field. Thus, the Middle Paleozoic metabasites of the Khrami crystalline massif are represented by shallow subvolcanic magmatites predominantly of andesite-basalt and tholeiite-basalt groups of the tholeiitic series. They correspond to the MORB and VAB genetic groups.

How to cite: Shengelia, D., Tsutsunava, T., Beridze, G., and Javakhishvili, I.: Geology, geochemical typification and petrogenic model of formation of Middle Paleozoic metabasites of the Khrami crystalline massif (Georgia), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2760, https://doi.org/10.5194/egusphere-egu23-2760, 2023.

The Hessian Depression in Germany represents the northern continuation of the Upper Rhine Graben and is known for Cenozoic alkaline basaltic lavas. Many of these carry peridotite xenoliths of mantle origin, which were studied mainly in the  80-ies of the XX century (Hartmann & Wedepohl 1990 and references therein). These studies documented mantle lithosphere melting followed by metasomatism. Here we describe the xenoliths from the Stöpfling quarry near Homberg upon Efze. The quarry has been recultivated and sampling is not possible now, our samples come from the archival collection of the Department of Geochemistry of the University of Göttingen. In this abstract, we give an overview of newly collected major- and trace-element mineral-chemical data from 11 xenoliths.

The xenoliths from Stöpfling are spinel-facies lherzolites and harzburgites. They consist of aggregates of few coarse (typically 4-6 mm across) grains of olivine and orthopyroxene embedded in fine-grained matrix of olivine, ortho- and clinopyroxene and spinel. Coarse-grained aggregates represent fragments of protogranular texture and are volumetrically prevailing. Spinel is commonly interstitial and has amaeboidal morphology. Locally, centimetre-thick layers of websterites cross-cut the peridotites. Hartmann & Wedepohl (1990) report traces  (<1 vol. %) of phlogopite in 2 of 12 lherzolites they studied.

The major element composition of olivine is strikingly homogeneous in all studied rocks (91±0.5 % forsterite and 0.40 wt. %. NiO), Ca content is < 500 ppm. Orthopyroxene is mildly aluminous (0.10-0.17 atoms of Al per formula unit, [pfu]) as is clinopyroxene (0.12-0.25 atoms Al pfu). Spinel Cr# [= Cr/(Cr+Al)] varies from 0.18 to 0.46. Clinopyroxene coexisting with spinel of low Cr# is Al-rich and contains 1600-2200 ppm Ti, whereas that coexisting with spinel of higher Cr# is less aluminous and contains 600-1200 ppm Ti. Clinopyroxene coexisting with spinel of Cr# 0.46 is extremely impoverished in Ti (50 ppm). The REE patterns of clinopyroxene in most samples are above the primitive-mantle (PM) level, are LREE-enriched and flat at MREE-HREE. Those extremely depleted in Ti show a decrease from HREE towards MREE, the contents of which are below PM level, and are strongly LREE-enriched.

Peridotites from Stöpfling consist of olivine which chemical homogeneity  across the xenolith suite supposedly records melt depletion. The variable content of Al in orthopyroxene from different samples probably is due to subsequent refertilization event(s) involving silicate melt, whereas the REE characteristics of clinopyroxene suggests that it was additionally cryptically  metasomatized. The unaffected olivine composition indicates low ratio of metasomatic agent to protolith.

Acknowledgements. JP is grateful to G. Wörner for enabling access to the xenoliths from Stöpfling that were originally collected by H. Wedepohl and are now archived at the Geochemistry and Isotope Geology Division of the Geoscience Center at University Göttingen (GZG).

Funding. This study originated thanks to the project of Polish National Centre of Research 2021/41/B/ST10/00900 to JP.

References:

Hartmann G., Wedepohl. K.H. (1990): Metasomatically altered peridotite xenoliths from the Hessian Depression (Nortwest Germany). Geochim. Cosmochim. Acta 54: 71-86.

How to cite: Puziewicz, J., Aulbach, S., Matusiak-Małek, M., Ntaflos, T., and Ziobro-Mikrut, M.: Peridotite xenoliths from Stöpfling in Hessian Depression (Germany) revisited, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2878, https://doi.org/10.5194/egusphere-egu23-2878, 2023.

Triassic volcanism in Greece is mainly associated with the rift phase of the Neotethys that resulted in the formation of E-MORB and OIB alkali basalts, which are widespread throughout the Hellenic mainland[1]. In most of the outcrop localities (e.g. Pindos, Koziakas, Othris, Argolis) these basalts are closely related in the field with other more differentiated volcanics that display a clear subduction signature [1,2]. In the Northern Peloponnese and specifically from the localities of Drakovouni, Palaiohouni and Perachora, three types of lavas were identified: basaltic andesites, andesites and rhyodakites, which are fine to medium grained and displaying either porphyritic or even equigranular textures in the more felsic varieties. These lavas were classified based on their Si, Na and K contents, as well as their Nb/Y vs. Zr/Ti ratios, which were subjected to rather restricted metasomatic processes (LOI:1.1-3.7, partial albitization and uratilization). Based on their potassium contents, as well as upon the AFM geochemical ternary plot and their FeO/MgO ratios, they are geochemically classified as calc-alkaline volcanics, clearly being affected by subduction-related processes. The latter is confirmed by: presence of magmatic magnesiohornblende in all types of lavas at variable amounts, enhanced Th/Yb contents (2.4-4.1), LREE enrichments [(La/Yb)_CN=6.2-10.0], lower normalized values of Th and U compared to Nb and Ta, positive K and Pb anomalies, negative Ti anomalies in the PM-normalized diagrams, noticeable LILE enrichments (e.g. Cs, Rb, Ba).

Fractional crystallization played a significant role in the differentiation processes. This is confirmed by: presence of primary clinopyroxene and amphibole in the basaltic andesites whose modal composition significantly decreases in the andesites and rhyodakites (only accessory amphibole), relatively strong correlation between Sc/Y with CaO/Al₂O₃ (R² = 0.91), positive correlation between P₂O₅/TiO₂ and (La/Yb)_N (R² = 0.87), higher Cr and Ni contents in the least differentiated lavas, increase of Nb/Yb in the highly fractionated lavas, increasing Eu negative anomalies from the compositionally basic to the felsic varieties (basaltic andesites Eu_CN/Eu*= 0.73-0.80; andesites Eu_CN/Eu* = 0.63-0.74, rhyodakites Eu_CN/Eu* = 0.51-0.61). Apart from fractional crystallization, crustal assimilation (AFC processes) likely played an additional role during differentiation, shown by the strongly positive correlation between SiO₂ and Nb/Yb (R² = 0.92). The Sr-Nd isotopic data further confirm the effect of crustal contamination and AFC processes, with lower ¹⁴³Nd/¹⁴⁴Nd and higher ⁸⁷Sr/⁸⁶Sr ratios for the rhyodakites compared to the andesites and basaltic andesites.

References: [1]Koutsovitis, P., Magganas, A., Ntaflos, T., Koukouzas, N., Rassios, A.E., Soukis, K., 2020. Petrogenetic constraints on the origin and formation of the Hellenic Triassic rift-related lavas. Lithos 368-369, 105604, [2] Pe-Piper, G., Piper, D.J.W., 2002. The Igneous Rocks of Greece. Borntraeger, Stuttgart, pp. 1–645.

How to cite: Koutsovitis, P., Soukis, K., Kokkalas, S., Magganas, A., Ntaflos, T., Jang, Y., and Kwon, S.: Evidence for the effects of subduction in Triassic lavas from the Northern Peloponnese (Greece): A mineralogical, geochemical and isotopic (Sr-Nd) approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4252, https://doi.org/10.5194/egusphere-egu23-4252, 2023.

Mount Vulture is a stratovolcano (age 0.75-0.14 Myr) located in southern Italy, which despite being at the same latitude of Vesuvius and Phlegreian Fields, has several peculiarities about its setting and erupted magma composition. Indeed, if compared to other Italian Quaternary volcanoes, it is the only one located east of the Apennine Front, about 100 km off the axis of the Campanian Magmatic Province (Peccerillo et al., 2017). Furthermore, although being a quiescent volcano (last eruption dated 0.14 Myr), previous studies (e.g., Caracausi et al., 2015, Bragagni et al., 2022) have shown extremely high CO₂ emissions (4.85 × 108 mol yr^-1), which are likely related to the carbonatitic volcanism of its final phase of activity, as well as some petrological aspects in the erupted products pointing to a mantle source metasomatism.

Recently, investigations on Vulture mantle xenoliths (Carnervale et al., 2022) revealed CO₂-rich fluid inclusions (FIs) that indicate a primary depth of bubbles entrapment in olivine and pyroxene phenocrysts coinciding with the regional crust-mantle boundary (27-30km).

This research focuses for the first-time noble gases isotopes (He, Ne, Ar) in FIs from lherzolite enclaves from Mt. Vulture tephra. The He isotopic ratios (as R/Ra; R is the ³He/⁴He ratio of the sample and Ra the same ratio in air), are between 6.2 and 5.4 ± 0.08. These values are lower than the signatures of the MORB upper mantle (8 ± 1Ra) and overlap the values of the Sub Continental Lithospheric Mantle (SCLM, 6.1 ± 0.9Ra). The Ne isotopic signatures (²⁰Ne/²²Ne and ²¹Ne/²²Ne) are in the field of the MORB values.

The He-Ne-Ar systematics is consistent with a SCLM source feeding the magmatism of the Vulture volcano. However, considering the noble gases He-Ne-Ar, in Vulture xenolites this mantle source has affinities with that feeding the volcanic activities of Mt. Etna (Nakai et al., 1997; Correale et al., 2014). This inference bears some evidence about the similitudes of the mantle below these two volcanic systems that is affected by mantle metasomatism, which is likely also responsible for the large CO₂ fluxes and the carbonatitic magmatism (Bragagni et al., 2022). New measurements of the noble gases in free gases from the two volcanoes together with a detailed comparison between the geochemistry and petrography of the Vulture and Etna most primitive products will provide new constraints on the mantle typology below the two volcanoes and its relationship with the geodynamical evolution of the central Mediterranean.

References

Bragagni et al., 2021, Geology

Carnevale et al. (2022). Geophys. Res. Lett.

Caracausi et al. (2015). Earth Planet. Sci Lett.

Correale et al., 2014. Lithos

Nakai et al., (1997). Earth Planet. Sci Lett.

Peccerillo, A. (2017). Advances in Volcanology. Springer, Cham.

How to cite: Italiano, L., Caracausi, A., Carnevale, G., Paternoster, M., and Rotolo, S. G.: First noble gases measurements in lherzolites from Mt Vulture volcano: new constraints on the mantle below Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4404, https://doi.org/10.5194/egusphere-egu23-4404, 2023.

Peridotite xenoliths provide valuable insight into lithospheric mantle conditions, composition, and evolution. The origin of amphibole in the lithospheric mantle and whether amphibole melts to produce alkaline intraplate magmas is a highly debated topic. Large areas of the lithospheric mantle forming Earth’s youngest continent, Zealandia, have chemical compositions comparable to Archean mantle lithosphere but Re-Os isotope and bulk rock data indicate that lithosphere stabilisation occurred in the Mesozoic. Some areas of this refractory lithospheric mantle have been metasomatized, with one of the clearest occurrences being MARID-like veins in xenoliths in alkaline intraplate magmas in the Southern Alps of New Zealand. These xenoliths contain abundant veinlets composed of amphibole, phlogopite, clinopyroxene and apatite in rocks that have average olivine compositions exceeding Mg# 92 and spinel Cr# 70. The latter indicates that these peridotites have undergone >25% partial melting prior to metasomatism.

Using a combination of quantitative scanning electron beam methods, trace element and in-situ laser ablation inductively coupled mass spectrometry (LA-ICP-MS) analysis, and conventional ⁸⁷Sr/⁸⁶Sr isotope analysis by solution, we seek to establish the origin of hydrous phases in this mantle lithosphere. The benefit of inspecting formerly highly depleted peridotites is that the chemistry of the metasomatic agent, which is typically enriched in incompatible elements, is less diluted than in the cases where melts infiltrate fertile lithosphere. Although minor Fe-diffusion has occurred within the studied host rock, the bulk compositions of the veins are picro-basaltic. The mica separates, measured by solution chemistry, are today more radiogenic than the in-situ diopside and amphibole analyses, however, we find that the age-corrected ~25 Ma, ⁸⁷Sr/⁸⁶Sr initials fall in a tight cluster of very depleted mantle-like ratios from 0.7027 to 0.7056. Although the fluids appear to have sub-alkaline bulk compositions, the amphibole trace elements are enriched in HFSE and lack depleted Nb components.

The data suggests that these basaltic veins are not arc-related and do not derive from melting of subducted sediment, but also have no direct genetic link to the host alkaline melts. If this latter interpretation is correct, then the injection of hydrous veins was not part of a continuous process that resulted in alkaline magmatism, although they may have been subsequently melted to give rise to alkaline magmas with depleted mantle-like isotopic characters. 

How to cite: Cooper, N., Scott, J., Brenna, M., Palmer, M., Reid, M., Stirling, C., and le Roux, P.: The origin of hydrous amphibole in the subcontinental lithospheric mantle beneath the Southern Alps of New Zealand, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4569, https://doi.org/10.5194/egusphere-egu23-4569, 2023.

Earth’s mantle is highly heterogeneous, with mantle-derived rocks sampling depleted and enriched domains both in intraplate settings and along spreading ridges. The most notorious isotopic anomaly is the DUPAL anomaly, where an overall strong recycled isotopic signature occurs. Studies on Tethyan and Paleo-Tethyan ophiolites have shown the persistence of “DUPAL signature” in those oceans, which paleogeographic reconstructions place on approximately the same position as the present-day Indian Ocean and thus argue for a long-lived “DUPAL signature” in the mantle. The origin of the DUPAL anomaly is controversial, with many studies pointing to it being a primordial feature. More recently, however, it has been shown that plume products in the African Mantle Domain (AMD), of which the DUPAL anomaly region is a part of, generally bear a more enriched signal than plume-related rocks in the Pacific Mantle Domain. This observation has been hypothesized to be related to the formation of the Pangea supercontinent above the present-day AMD, and therefore offering a geodynamic scenario capable of explaining the origin of the enriched isotopic signature of the AMD. However, present-day ocean crust record is limited in time, extending to 200 Ma at maximum, younger than the formation of Pangea at ca. 320 Ma. To investigate the oceanic record of mantle enrichment further back in time and test the influence of supercontinent cycle on the composition of the AMD, it is necessary to utilise preserved oceanic terranes in orogenic belts. In this study we compiled isotopic data from preserved oceanic terranes related both to the formation of the AMD, starting from the assembly of Gondwana till the duration of Pangea, including that of the Mozambique, Adamastor, Goias-Pharusian, Iapetus, Rheic, Qilian-Shangdan, Paleo-Tethys, Meso-Tethys and Neo-Tethys paleo-oceans. Neodymium isotopic data is the most widely available for these ophiolites. The Nd isotopic data indicates a progressively more depleted signal before Gondwana formation until it reaches a maximum and stays relatively stable until shortly after Pangea break-up, where noticeable decrease in depletion occurs. Lead isotopic data is less readily available, existing data nevertheless allow to observe an increase in Th/U ratio during Gondwana formation. Taken together, these observations indicate an increase in recycled continental components in the mantle source of the AMD ophiolites. We envisage this to be evidence for mantle enrichment during the formation of Gondwana and Pangea within the AMD. New isotopic analyses are still needed to paint a clearer picture of the interplay between the supercontinent cycle and mantle geochemistry.

How to cite: Azevedo Berquo de Sampaio, P., Li, Z.-X., Doucet, L. S., and Gamaleldien, H.: Evolution of the African Mantle Domain and its enriched signal: perspective from pre-200 Ma ophiolites, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4686, https://doi.org/10.5194/egusphere-egu23-4686, 2023.

Permian mafic volcanic rocks occurring in southern terrains of Scotland (United Kingdom) are rich in peridotitic xenoliths providing insight into the composition of the Subcontinental Lithospheric Mantle (SCLM) beneath this area. Peridotites from the Ruddon’s Point (Fife) xenolith suite form four textural groups: (1) protogranular and (2) porphyroclastic lherzolites, (3) equigranular wehrlites and (4) lherzolites transitional between protogranular and equigranular peridotites. The SCLM beneath southern Scotland was affected by reaction with an alkaline melt resulting in clinopyroxene crystallization (wehrlitization) and decrease of Fo in olivine from primary (protogranular and porphyroclastic) lherzolites (Fo_88.5-90.0) through transitional to equigranular (Fo_80.0-85.0) peridotites (Matusiak-Małek et al., 2022).

The sulfides occurring in the peridotites form oval, elongated or irregular grains enclosed in pyroxenes and olivine, or interstitial between these phases. The abundance of sulfides  increases from the transitional lherzolites (mean = 0.009 vol.‰), through equigranular and porphyroclastic peridotites (0.026 and 0.029 vol.‰, respectively) to protogranular lherzolites (0.050 vol.‰). Sulfide minerals present in all textural groups are pentlandite (Pn) and chalcopyrite (Ccp). There is generally an absence of pyrrhotite (Po), but protogranular and “transitional” lherzolites contain minor amounts. Porphyroclastic lherzolites occasionally contain millerite (Mlr) and covellite (Cv). The sulfides from the equigranular and protogranular peridotites are more enriched in Cu-, and depleted in Ni-phases (Po₀Pn₇₁Ccp₂₉ and Po₄Pn₆₈Ccp₂₇, respectively) in comparison to sulfides from the porphyroclastic and transitional peridotites (Po₀Pn₈₀Ccp₂₀ and Po₆Pn₈₃Ccp₁₂, respectively). The Cu/(Cu+Fe) is homogenous in sulfides of all the textural types, whereas Ni/(Ni+Fe) in pentlandite is homogenous only in transitional and equigranular peridotites (0.64–0.65 and 0.55–0.59, respectively) in contrast to porphyroclastic and protogranular ones (0.54–0.68 and 0.52–0.64, respectively). The only significant difference in trace element composition of sulfides appears in the concentrations of Co and Zn which  are  4894 ppm and 2214 ppm, respectively, in the protogranular peridotites, compared to 30090 ppm and 1391 ppm, respectively, in the transitional peridotites.

The more primitive protogranular and porphyroclastic lherzolites  are characterized by the highest sulfide abundances in comparison to the sulfides from melt-metasomatized equigranular wehrlites, with no significant differences  in sulfide mineral and chemical (major and trace elements) composition between groups. Thus, activity of the alkaline silicate melts responsible for wehrlitization of the primary lherzolites seems not to influence the sulfide enrichment in the SCLM beneath S Scotland. The presence of Cv and Mlr in lherzolites suggests alteration by hydrothermal, post-volcanic activity, affecting the xenoliths after the exhumation to the surface by basaltic lavas.

Matusiak-Małek, M., Kukuła, A., Matczuk, P., Puziewicz, J., Upton, B.J.G., Ntaflos, T., Aulbach, S., Grégoire, M., Hughes H.S.R. (2022). Evolution of upper mantle and lower crust beneath Southern Uplands and Midland Valley Terranes (S Scotland) as recorded by peridotitic and pyroxenitic xenoliths in alkaline mafic lavas. 4th EMAW TOULOUSE 2021 Book of Abstracts.

How to cite: Mazurek, H., Matusiak-Małek, M., Hughes, H. S. R., and Upton, B. J. G.: The composition and origin of sulfides in peridotitic xenoliths from Ruddon’s Point (Fife, Scotland), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4995, https://doi.org/10.5194/egusphere-egu23-4995, 2023.

The sub-continental lithospheric mantle (SCLM) of Archean cratons represents the depleted and buoyant residue left behind after crust extraction. The history of the SCLM is notably complex in all cratons, often recording multiple episodes of melting and metasomatism. Garnet is a prime target for studying this history, as it provides thermobarometric constraints and hosts incompatible trace elements that can help identify melting and refertilization. Placing the rich geological record of mantle garnet in time is crucial for resolving cratonic evolution. Robust age constraints from garnet have nevertheless been difficult to obtain. Isolating enough analyte material for Lu-Hf or Sm-Nd chronometry is challenging for small xenoliths of highly depleted mantle rock. Age estimates are typically based on external or two-point isochrons with limited statistical robustness and geological interpretability. Moreover, chronometer systematics are principally not well constrained for the conditions and processes of the mantle. The question of which assemblages and chemical features of the Archean SCLM are actually of the Archean age is often left unanswered. To address this, we used ultralow-blank Lu-Hf chronometry, in concert with trace element analysis, on a targeted analysis of texturally and compositionally different mantle xenoliths from three Archean cratons (Slave, Kaapvaal, and Siberian Cratons).

The samples analyzed in this study represent a variety of garnet-bearing lithologies: clinopyroxene-rich fertile lherzolite, harzburgite (both granular and sheared), and orthopyroxenite with pyrope in exsolution lamellae. These samples were chosen, as they capture various stages of mantle evolution, from initial melting and subsolidus equilibration to shearing and metasomatic re-equilibration. We were able to obtain multi-point internal Lu-Hf isochrons for all lithologies, including those with extremely depleted compositions. The Lu-Hf ages span the history of the SCLM, from the Mesoarchean to the ages of kimberlite eruption. The oldest ages were obtained from lithologies depleted in Ca and clinopyroxene, i.e., exsolved orthopyroxenites and harzburgites from the Kaapvaal and Siberian Cratons. Lherzolites provided younger ages corresponding to metasomatic events, some of which could be linked to synchronous magmatic episodes in the overlying crust.

The data show that compositional and geochronological signatures in garnet can be retained on billion-year time scales. Static and dynamic recrystallization, and metasomatism – rather than temperature alone – control these signatures in garnet. The exsolution of pyrope in Ca-depleted Kaapvaal and Siberian orthopyroxenites is now confirmed to have occurred in the Archean. The geochemistry and petrology of these particular samples thus can constrain the P-T evolution that led to the development of the early continents.

How to cite: Musiyachenko, K., Smit, M., Kopylova, M., and Korsakov, A.: Unlocking the secrets of the Archean cratonic mantle through garnet Lu-Hf geochronology, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9276, https://doi.org/10.5194/egusphere-egu23-9276, 2023.

The Edessa ophiolite complex represents remnants of oceanic lithosphere which was thrust out of one or more ocean basins during Upper Jurassic to Lower Cretaceous time. Petrographic, geological and geochemical evidences indicate that this ophiolite complex consists of both mantle and crustal suites. It includes lherzolites, serpentinised harzburgites with high degree of serpentinisation, diorites, gabbros, diabase dolerites and basalts. We present here new data on mineral compositions and geochemistry in mafic rocks. The basalt displays N-MORB composition, having enhanced TiO₂ (1.9-2.4 wt.%) and flat REE patterns, whereas the gabbros show E-MORB affinities, having moderate to high Ti content (TiO₂ = 1.1-1.2 wt.%) with strong LREE-HREE fractionations. Such geochemical enrichment from N-MORB to E-MORB composition indicates mixing of melts derived from a depleted mantle and fertile mantle source at the spreading centre. On the other hand, diorites and partially diabase dolerites display SSZ-type composition with low Ti content (TiO₂ = 0.1-0.7 wt.%) and depleted LREE pattern with respect to HREE. They also display high Ba/Zr, Ba/Nb and Ba/Th ratios relative to primitive mantle, which strongly represents the melt composition generated by partial melting of depleted lithospheric mantle wedge influenced by hydrous fluids derived from subducting oceanic lithosphere in a forearc setting. Based on these geochemical evidence, we suggest that mid ocean ridge (MOR) type mafic rocks (basalts and gabbros) from the Edessa ophiolite represent the section of older oceanic crust which was generated during the opening of the Axios Ocean. Conversely, the diorites and diabase dolerites represent the younger oceanic crust which was formed at the forearc region by partial melting of the depleted mantle wedge modified by hydrous fluids released from the subducting oceanic slab.

How to cite: Rogkala, A., Petrounias, P., Koutsovitis, P., Giannakopoulou, P. P., Pomonis, P., and Hatzipanagiotou, K.: Geochemical characteristics of mafic rocks from the Edessa ophiolite (North Greece): Implications for their petrogenesis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10026, https://doi.org/10.5194/egusphere-egu23-10026, 2023.

Primitive mantle rocks usually contain rare earth elements (REE) in very low concentrations. Here we report an occurrence of monazite associated with REE-rich apatites in a carbonate-bearing wehrlite xenolith from Pleiku, central Vietnam. The sampled xenolith displays an equigranular matrix of rounded olivine grains. Texturally primary orthopyroxene, clinopyroxene and spinel are notably absent. Scattered within the olivine matrix two types of domains are present: domain-I contains numerous blocky clinopyroxene grains within a matrix of quenched silicate melt and is associated with a second generation of olivine, small euhedral spinel and rare grains of carbonates. Both apatite and monazite may be present. Domain-II typically contains abundant irregularly shaped patches of carbonate associated with quenched silicate melt, secondary olivine, spinel, and clinopyroxene. No phosphate phases are observed within type-II domains. Monazite occurs in different generations: monazite I is found as very small rounded to elongate grains included in primary olivine, partly crosscut by fine melt veinlets, monazite II as large grains up to 300 x 200 µm in size with embayed grain boundaries and monazite III as very small euhedral and needle-like crystals in silicate melt pools. For apatite two textural types occur: apatite I forms lath-shaped to rounded crystals up to 200 x 50 µm in size, apatite II is present within silicate melt pools of type-I domains where it forms euhedral needle-like to equant grains. Some of the apatite II crystals may have cores of monazite III. Monazites show compositional variation mainly with respect to ∑REE₂O₃ (63-69 wt%) and ThO₂ (1.1-5.3 wt%) and only minor variations in P₂O₅ (29-32 wt%) SiO₂ (<0.05-0.4 wt%) and CaO (0.2-0.4 wt%) Apatites are characterized by strongly variable and high REE₂O₃ and SiO₂ contents (4-27 wt% ∑REE₂O₃,0.6-6.8 wt% SiO₂) as well as with significant Na₂O (0.3-1.5 wt%), FeO (0.1-1.8 wt%), MgO (0.2-0.6 wt%) and SrO (0.2-0.9 wt%) contents. F and Cl contents are in the range 1.9-3.0 wt% and 0.2-0.8 wt%, respectively. Based on textural evidence and chemical composition of the metasomatized mineral phases an initial stage of metasomatism is proposed which was triggered by a P-REE-CO₂-rich agent with low a_H2O resulting in the co-precipitation of carbonates as patches and along micro-veins and of phosphates in a peridotite assemblage. A subsequent second stage is characterized by pervasive infiltration of an alkali-rich basaltic melt into the carbonate + phosphate-bearing assemblage. The presence of monazite prior to silicate melt infiltration is indicated by narrow melt veins crosscutting monazite I grains. Reactions of the silicate melt with the pre-existing phases led to the formation of domains-I and -II and changed the composition of the infiltrating melt towards phonolitic-trachytic composition. The second stage led to partial breakdown and recrystallization of monazite and apatite.

How to cite: Hauzenberger, C., Konzett, J., Joachim-Mrosko, B., and Nguyen, H.: A monazite- and REE-rich apatite-bearing mantle xenolith from Pleiku, central Vietnam, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10058, https://doi.org/10.5194/egusphere-egu23-10058, 2023.

Peridotite xenoliths from kimberlites are useful tools for exploring the architecture and composition of the thick sub-cratonic lithosphere, and thus understanding the long-term evolution of the Earth’s mantle. However, the continuous infiltration of kimberlite-related melts and fluids prior to - and during - the transport of mantle-derived fragments towards the surface makes it difficult to extract information about the original texture and chemistry of the mantle rocks and the deep-seated metasomatic processes.

In this study, fresh spinel- to garnet-bearing peridotite xenoliths from Udachnaya-East were studied to unveil the nature and composition of the lithospheric mantle beneath the Siberian craton. The studied samples have mostly harzburgitic to dunitic composition, even though lherzolites and rare wehrlites are also found. Occasionally, harzburgites are orthopyroxene-rich (up to 40 vol.%) or garnet-rich (up to 30 vol.%). The texture of the peridotites is extremely variable, ranging from protogranular to highly recrystallized and/or sheared. In spinel-bearing rocks, primary olivine is Mg- and Ni-rich (Fo_90-93; NiO = 0.34-0.46 wt%), orthopyroxene has Mg# of 92-94 and Al₂O₃ in the range of 0.3-3.0 wt%, while clinopyroxene is Mg-rich (Mg# 94-96), with Al₂O₃ comprised between 1.0 and 3.5 wt%. In garnet-bearing peridotites, olivine ranges from Mg- and Ni-rich (Fo₉₂; NiO = 0.45 wt%) to Fe-rich and Ni-poor (Fo₈₇; NiO = 0.25 wt%), while pyroxenes have Mg# from 93 to 87-88 and comparatively low Al₂O₃ contents (orthopyroxene: 0.5-1.1 wt%; clinopyroxene: 0.8-2.2 wt%). High-precision electron microprobe analyses complemented by thermo- and oxy-barometric models were used to reconstruct the thermo-chemical log of the Siberian sub-cratonic mantle, in comparison to what proposed by Liu et al. (2022). Textural-compositional studies of the reaction zones enabled to discriminate the secondary-formed minerals with composition ascribable to the liquid line of descent of kimberlite-related melts at Udachnaya (Casetta et al. 2023) from those formed during melt/fluid-rock reactions taking place in the mantle before xenoliths’ entrainment by the host kimberlites. Altogether, our results enable to trace the P-T-X evolution experienced by the Siberian mantle, opening a window onto the comprehension of the interactions between kimberlitic-related fluid/melts and the sub-cratonic lithosphere.

Casetta, F., Asenbaum, R., Ashchepkov, I., Abart, R., & Ntaflos, T. (2023). Mantle-Derived Cargo vs Liquid Line of Descent: Reconstructing the P–T–fO₂–X Path of the Udachnaya–East Kimberlite Melts during Ascent in the Siberian Sub-Cratonic Lithosphere. Journal of Petrology, 64(1), egac122.

 Liu, Z., Ionov, D. A., Nimis, P., Xu, Y., He, P., & Golovin, A. V. (2022). Thermal and compositional anomalies in a detailed xenolith-based lithospheric mantle profile of the Siberian craton and the origin of seismic midlithosphere discontinuities. Geology.

How to cite: Casetta, F., Ashchepkov, I., Faccincani, L., Abart, R., and Ntaflos, T.: Peridotite xenoliths from the Udachnaya-East kimberlite: windows onto the evolution of the Siberian sub-cratonic lithospheric mantle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12712, https://doi.org/10.5194/egusphere-egu23-12712, 2023.

The Mirdita Ophiolite (N Albania) consists of two meridional belts of different geochemical affinities: supra-subduction zone for the Eastern belt and mid-ocean ridge (MOR) for the western belt. Puke Massif described in this study is a mantle dome belonging to the MOR belt.

Structurally, the Puka Massif is interpreted as an Oceanic Core Complex formed of harzburgites cross-cut by dunitic channels grading to mylonitized plagioclase and amphibole bearing lherzolites with minor dunites and chromitites at the top of the section. The massif experienced an intense magmatic activity evidenced by gabbroic and pyroxenitic dykes. Field and petrographic evidences revealed that plagioclase, clinopyroxene and amphibole in lherzolitic mylonites crystallized from impregnating melts (Nicolas et al. 1999, 2017). Scientific question behind our study is whether this conclusion is confirmed by geochemical data.

Clinopyroxene from magmatic veins cross-cutting mylonites, has trace elements (TE) composition identical to that from the host peridotite. In general, 3 types of TE patterns can be identified in the veins and mylonites: 1. Strongly depleted (Yb=0.3-0.6x primitive mantle, PM, McDonough & Sun 1995); 2. Intermediate (Yb=1.1-4xPM); 3. Enriched (Yb=5-11xPM). The group 1 comprises only pyroxenites. Two relatively undeformed harzburgites occurring in the lowermost section of the mantle dome contain TE-poor clinopyroxene. One, which is amphibole-bearing, exhibits TE pattern resembling that in group 1, while the other one shows even more depleted signature, with Yb=0.8-1.3xPM and La <0.001xPM. Intrusive rocks from groups 2 and 3 are widespread in the whole massif while the occurrences of the depleted group are restricted to the lowermost sections. Rocks from different groups may occur within a single outcrop.

The TiO₂ content in clinopyroxene mimics the TE-based division of the rocks. Clinopyroxene in the group 1 and harzburgites has TiO₂<0.1 wt.%, whereas that from group 2 and 3 has 0.1<TiO₂<0.5 wt.% and TiO₂>0.5 wt.%, respectively. Similar relationships are observed in the composition of spinel, which has TiO₂<0.1 wt.% in group 1 rocks, 0.1 - 0.25 wt.% in group 2 and between 0.1 and 2.0 wt.% in the group 3 rocks.

As magmatic rocks and deformed peridotites share common clinopyroxene TE trends, as well as similar Ti variations in clinopyroxene and spinel, geochemical data support impregnating origin of mylonites. Impregnating melts, differing in enrichment level, were active within whole massif; only the most depleted seem to be restricted to some of its parts. Only internal or easternmost harzburgites could have escape magmatic impregnations; these samples are relatively undeformed and have depleted melting-like TE trends. These findings are in agreement with melt impregnation origin of mylonites. Presence of the depleted lithologies supports primarily harzburgitic origin of the massif, later followed by mylonitization of some of its part. 

This study was financed as a project within program “Diamond Grant” (DI 024748).

How to cite: Mikrut, J., Matusiak-Małek, M., Gregoire, M., Ceuleneer, G., Onuzi, K., and Puziewicz, J.: The impact of melt impregnation on the genesis of mantle peridotites from Puke Massif (Mirdita Ophiolite, Albania) revealed by geochemical data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13627, https://doi.org/10.5194/egusphere-egu23-13627, 2023.

The 3.5-0.5 Ma Devès volcanic field is located in the “southern” mantle domain of the French Massif Central (MC), which originated by partial melting, likely followed by refertilization by melts from the upwelling asthenosphere [1, 2]. However, the extent of melting versus degree of refertilization remains unclear. In order to obtain new insights into this fundamental question, we studied a large mantle xenolith population (n – 21) from a cinder cone in the NW of Devès, the Mt. Briançon nepheline basanite. Extensive use of EMPA and LA-ICP-MS allowed us to gather a comprehensive and representative dataset. Here, we present preliminary interpretations. Ongoing EBSD analyses will provide further data to confirm or correct our hypothesis.

The lithospheric mantle (LM) beneath the Devès is heterogeneous. It contains lherzolite with clinopyroxene (cpx) exhibiting REE patterns with relatively flat Lu-Eu and variable LREE-depletion. The coexisting spinel (spl) is highly aluminous (Cr# 0.09-0.15). By analogy with prior work [2], we suggest that cpx and spl were added to the rock by a MORB-type melt [2]. Those lherzolites probably represent refertilized LM similar to the Lherz massif [3], which obscures the original degree of depletion.

A distinct mantle region below the Devès is represented by harzburgites and cpx-poor lherzolites containing cpx with REE patterns that show moderately increasing Lu-Sm and steeply increasing towards La. The coexisting spl has medium to high Cr# (0.17-0.28). We suggest that this lithology was not refertilized by MORB-like melts, but records some other metasomatic event(s).

A single harzburgite xenolith contains LREE-enriched cpx similar to those described above, but of significantly lower element abundances. This harzburgite is the most magnesian in the entire suite, with olivine Fo ~91.2% and Mg# in pyroxenes ~0.92 (vs Fo 88.5-90.4% and Mg# 0.88-0.91 for other peridotites). Pyroxenes have the lowest Al, Fe, Ti, Na contents in the whole suite and spinel is the most chromian (Cr# ~0.43). This rock resembles harzburgites from the northern domain of the MC, interpreted as a relatively depleted residue of partial melting [4].

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

References:

[1] Lenoir et al. (2000). EPSL 181, 359-375.

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

[3] Le Roux et al. (2007). EPSL 259, 599–612.

[4] Downes et al. (2003). Chem Geol 200, 71–87.

How to cite: Ziobro-Mikrut, M., Puziewicz, J., Aulbach, S., and Ntaflos, T.: The lithospheric mantle beneath Devès volcanic field – case study of mantle xenoliths from Mt. Briançon (Massif Central, France), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14795, https://doi.org/10.5194/egusphere-egu23-14795, 2023.

Large, single crystals (> 1cm) are a familiar component of mantle xenolith suites of many kimberlites.  Confusion between different suites exists in the literature, however, which affects petrogenetic models, and some clarification is warranted.  Megacrysts of the Cr-poor suite[1] are most common.  Cr-poor silicates (garnet, clinopyroxene, orthopyroxene, olivine) are characterized by lower Mg/(Mg+Fe) and Cr₂O₃ and higher TiO₂ values than typical mantle peridotite minerals.  Strong geochemical trends in most occurrences of Cr-poor megacryst suites (e.g., concomitant decrease in Mg/(Mg+Fe) and Cr₂O₃) are interpreted by most authors as the result of fractional crystallization of a kimberlite, or kimberlite-like, magma.   

The Cr-rich megacryst suite, comprising garnet, clinopyroxene, orthopyroxene and olivine, but not ilmenite, was described from the Sloan/Nix kimberlites in northern Colorado[1].  Constituent minerals, all four of which are essential to the definition of the suite, are characterized, in part, by high and restricted values of Mg/(Mg+Fe) and wt% Cr₂O₃ (e.g., 0.791 to 0.837 and 6.1 to 13.0, respectively, in garnet [2]).  Elsewhere, large crystals with Mg/(Mg+Fe) and Cr₂O₃ values higher than Cr-poor suite minerals do occur, but none correspond to the Sloan-Nix Cr-rich suite in paragenesis, size and/or composition[2].  For example, almost no garnet megacrysts described as “Cr-rich” or “high-Cr” from other localities (e.g., refs 3-6) contain >6 wt% Cr₂O₃ and even garnets with <2 wt% Cr₂O₃ are termed “Cr-rich” or “high-Cr”.  Most, or all, of these so-called “Cr-rich garnet megacrysts” are simply xenocrysts from coarse-grained peridotite. 

The “Granny Smith” suite, first described from Kimberley and Jagersfontein [7], is dominated by Cr-clinopyroxene associated with phlogopite (and ilmenite at Kimberley), with uncommon olivine or rutile.  Garnet and orthopyroxene do not occur in this suite, which is neither equivalent to nor a subset of the Cr-rich megacryst suite.  Other suites dominated by Cr-clinopyroxene, also not shown to coexist with garnet and orthopyroxene, have been described from Orapa and Bobbejaan [6] and Grib [8], though analogies have been drawn with the Cr-rich megacryst suite despite compositional and paragenetic differences.  A similar megacrystalline assemblage (Cr-cpx, ilmenite, phlogopite, olivine) has been described from Attawapiskat [9] and at Balmoral megacrysts of Cr-cpx occur with ilmenite, Nb-Cr rutile and zircon [10].

All of these suites of Cr-cpx +/- ilmenite, rutile, phlogopite, olivine, zircon (lacking garnet/opx), though varied, have more in common with each other than with the Cr-rich megacryst suite.  All might be best termed “Granny Smith”, and may have common origins.  The only feature they share with the Sloan-Nix Cr-rich megacryst suite is the presence of large chromian clinopyroxene.  Use of such populations as equivalents of the Sloan-Nix Cr-rich megacryst suite in mantle petrogenetic schemes can lead to faulty conclusions. 

References:  1) Eggler et al. (1979) The Mantle Sample, 2) Schulze (2022) Goldschmidt Conf. Abstr., 3) Hunter and Taylor (1984) Am. Min., 4) Kopylova et al. (2009) Lithos, 5) Bussweiller et al. (2018) Min. Pet., 6) Nkere et al. (2021) Lithos, 7) Boyd et al. (1984) GCA, 8) Kargin et al. (2017) Lithos, 9) Hetman (1996) MSc., 10) Schulze, unpub. data. 

How to cite: Schulze, D.: Megacryst suites in kimberlite, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16528, https://doi.org/10.5194/egusphere-egu23-16528, 2023.

Integrating petrography and mineral chemistry data with the determination of volatiles concentration and isotopic fingerprint in fluid inclusions (FI) in ultramafic xenoliths is a novel approach which provides crucial information on the nature and evolution of the lithospheric mantle, together with important insight into how and where volatiles are stored and/or migrate through the lithosphere.

In this work, we investigated a new suite of ultramafic peridotite xenoliths from the Massif d’Ambre by integrating petrography, mineral and glass chemistry and the concentrations of volatiles [CO₂ and noble gases (He, Ne and Ar)] in fluid inclusions (FI) hosted in olivine (Ol), orthopyroxene (Opx) and clinopyroxene (Cpx). The Massif d’Ambre is a Cenozoic stratovolcano located in northern Madagascar originated upon intense volcanic activity from ~12 to ~0.85 Ma, and the area is characterized by the widespread occurrence of mantle xenoliths, mostly, but not restricted to, spinel lherzolites and subordinately pyroxenites, which are hosted in mafic volcanic rocks. The new suite comprises 18 lherzolites, 11 harzburgites, 2 dunites, 3 wehrlites and 1 Ol-clinopyroxenite. Based on their petrographic and textural features, the suite was divided into five distinct groups: group 1A (protogranular to porphyroclastic textures), group 1B (large and porphyroclastic olivines), group 2 (infiltrated dunites and wehrlites), group 3 (cumulate-textured wehrlites) and group 4 (Ol-clinopyroxenite). Xenoliths are modally and compositionally heterogeneous and a clear separation can be observed between groups 1A-1B and groups 2-3, as testified by the large forsterite range of olivine (Fo88.4 – 93.2 vs Fo78.7 – 89.1, respectively), the Mg# of orthopyroxene (89.5 – 93.2 vs 82.7 – 87.3, respectively) and clinopyroxene (90.9 – 95.2 vs 81.4 – 89.9, respectively). This systematics corroborates the distinct origin of the groups, with xenoliths belonging to 1A-1B having the most refractory character and reflecting high extents (up to 30%) of melt extraction, while groups 3-4 xenoliths reflecting less depleted or re-fertilized mantle portions. Based on glass analyses, we propose that a carbonatitic or carbonated alkaline agent may have interacted with some portion of the source mantle, in agreement with Coltorti et al. (2000). The noble gases in FI hosted in Ol, Opx and Cpx exhibit ³He/⁴He ratio corrected for air contamination (Rc/Ra values) ranging from 5.90 Ra to 7.05 Ra, which is below the typical MORB-like upper-mantle value (8 ± 1 Ra). Furthermore, the great majority of xenoliths exhibits ⁴He/⁴⁰Ar* ratios between ca. 0.2 to 0.8.

The major element distribution in mineral phases together with the systematic variations in FI composition will be used to place constraints on the origin and evolution (in terms of melting and metasomatism) of this portion of the mantle below the Massif d’Ambre and will be exploited to obtain a possible timeline for the petrological events that have characterized this lithospheric mantle portion.

Coltorti M., Beccaluva L., Bonadiman C., Salvini L. & Siena F. 2000. Glasses in mantle xenoliths as geochemical indicators of metasomatic agents. Earth Planet Sc. Lett., 183, 303–320.

Keywords: mantle xenoliths; lithospheric mantle; metasomatism; Massif d’Ambre

How to cite: Faccini, B., Faccincani, L., Rizzo, A. L., Casetta, F., and Coltorti, M.: Combining volatiles measurements in fluid inclusions with petrology of ultramafic xenoliths from the Massif d'Ambre: unravelling the nature and evolution of the northern Madagascar Sub-Continental Lithospheric Mantle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16798, https://doi.org/10.5194/egusphere-egu23-16798, 2023.

Melts with rhyolite compositions originate from partial melting of crustal rocks or extensive differentiation of basaltic melts, at temperatures in the range of 800 °C. Accordingly, they are confined to the shallow continental crust. Nevertheless, experimental studies have demonstrated that dacite-rhyolite melts can be generated at higher temperature (> 1000°c) and pressure (>2 GPa), by partial melting of continental crustal lithotypes, but direct evidence for their occurrence has never been found. This implies that rhyolite melts may be produced at mantle conditions either by subduction of sedimentary material or exhumation of subducted continental crust.

Ephemeral rhyolite melt inclusions were found preserved in peridotite xenoliths from Tallante (Betic Cordillera, southern Spain) that are remnants of a supra-subduction mantle wedge. Here, the interaction of silica-rich melts with peridotite generated hybrid mantle domains, characterized by the occurrence of millimetre-sizes felsic veins with crust-like Sr-Nd-Pb-O- isotope compositions. The “Tallante” composite xenoliths were found among a wide population of peridotitic xenoliths, and display extreme compositional and isotopic heterogeneities both within the ambient peridotite and within the felsic veins. The latter consist of orthopyroxene, plagioclase, and quartz, and they are separated from the surrounding peridotite by an orthopyroxene-rich reaction zone. In their mineral phases, rhyolite glass inclusions and interstitial films associated to quartz crystals were observed. Petrological evidence and thermodynamic modelling indicate that rhyolite melts were originated by partial melting of near an-hydrous garnet-bearing metapelites at temperatures above 1000 °C. Partial melting was likely triggered by near-isothermal decompression during rapid exhumation of previously subducted crustal slivers. The melts reacted with the ambient lithospheric mantle at lower temperature (900 °C) and produced orthopyroxene, followed by plagioclase, quartz, and phlogopite. On the basis of chemical characteristics, it is hypothesized that potassic (HK-calc-alkalic to shoshonitic) and  ultrapotassic magmas may originate from metasomatic mantle sources generated from the interaction of crustal rhyolitic melts with mantle peridotite.

How to cite: Dallai, L., Bianchini, G., Avanzinelli, R., Gaeta, M., Deloule, E., Natali, C., Cavallo, A., and Conticelli, S.: Crustal rhyolite melts at mantle depths, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17587, https://doi.org/10.5194/egusphere-egu23-17587, 2023.

Minerals from leucite lamproites of the Murunsky alkaline massif (Vladykin, 2000; 2005; Vladykin, 2009) were analyzed by electron microscopy in the sections of 700 grains of minerals (IGM SB RAS) and LA ICP MS (IIC SB RAS) - 40 grains. Pyroxenes, amphiboles, various micas including varieties of the Ba type, leucites and nephelines, Ba and K feldspars, eudialyte, barite, stroztianite, ilmenites, Cr- spinelides, Ti magnetites, apatites, tourmaline, and various carbonates and sulfides: pyrrhotite, petlandite, chalcopyrite, murunite, smithsonite, galena.

Pyroxenes are divided into 3 groups from diopsides to augites and aegirines, revealing a continuous series of compositions according to MgO (Fig. 1). Amphiboles K-richterites and arfversonites, and Ca-Fe ackermanites. Complete ranges from phlogopites to biotites have been established among micas. The proportion of Ba micas is significant. In the diagram  genetic digram (Minchell, 1995 )(Fig. 2) falls into the field of ailikites or orangeites,  and lamproites. Leucites and nephelines occurs  friquiently. Numerous apatites are characterized by Ca-Sr substitution and noticeable F contents (to 3%). K-type eudialytes and a mineral close to priderite were found.

In the TRE diagrams (Fig.3), pyroxenes are characterized by La-enriched ~200-250 weakly inclined spectra of La/Ybn (2-3) that spread out in the HREE wing. Amphiboles of the K-Na-Ca are characterized show inclined spectra with Ho-Tm depression,  LILE peaks elevated Zr, Hf, Y and Ta-Nb minima. The more alkaline amphiboles are characterized by reduced REE concentrations, more  elevated Zr-Hf. Ultra-alkaline amphiboles (richterite and arfvedsonite) have higher REE contentswith characteristic U-shaped spectra, very high LILE contents high peaks of Sr, Zr, Hf. Phlogopites have oblique U-shaped spectra with a sharp peak Eu interference Ti. Very high LILE with a peak at Va, Sr, Y, Pb are typical.

Low REE and especially LREE with a peak of Eu are characteristic of leucites. U, Sr, Pb peaks are also characteristic, and HFSE vary. The REE spectra of K-Ba feldspars are similar to those of phlogopite. High peaks of LILE, Sr, Pb, Y are expressed on spiderdiagrams

Judging by the peculiarities of mineral trends, lamproites are the result of low degrees melting  under the influence of plume melts of a mantle deeply metasomatized by subduction processes. Pyroxenes are end–to-end minerals, at an early stage their compositions were controlled by fractionation of olivine and then saturated SiO2 silicates. Further fractionation led to enrichment with rare elements P, Sr, F. In amphiboles, the growth of REE was accompanied by the accumulation of Zr, Hf, while Nb, Ta were removed during the deposition of T-magnetite. Grant RBRF 19-05-00788.

How to cite: Ashchepkov, I., Vladykin, N., Sotnikova, I., Medvedev, N., Karmanov, N., and Alymova, N.: Mineralogical and geochemical characteristics of lamproite minerals of the Murunsky massif., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3560, https://doi.org/10.5194/egusphere-egu23-3560, 2023.

Kimberlitic xenocrysts: garnets, pyroxenes, ilmenites, spinels from Anabar region were analyzed by EPMA and LAICPMS.

Reconstructed mantle sections of t Anabar region published (Ashchepkov et al., 2001; 2016; 2019; 2022 show in general, the relative rarity of sub-Ca pyropes  in lower part of the section and the frequency of wehrlite associations in the upper part. Pyroxenite -eclogite lens from 3 to 5 GPa is widely represented in most sections. Ilmenite trends are not long. In several pipes amphiboles from Cr-hornblendes to Cr-richterites were detected.

In the Anabar region (Khardakh and Staro-Rechensky fiedls) The REE patterns of  garnets are characterized by high variations in the spectra, with elevated LREE and HFSE minima, peaks of U, Pb, associated with subduction fluid flows. Pyroxenes are characterized by inclined REE spectra of La/Ybn ~15 to 20 and with varying HREE with subduction-related Ba, U, Pb peaks. But pyroxenes with plume related spectrums of with smooth spider diagrams (SD) are often found in pyroxenite lens.

Garnets from the Kuranakh field (Malokuonamskaya, Losi, Trudovaya, Universitetskaya etc) are divided into dunite-garburgite with low REE and LREE enrichment and wehrlite with convex REE maximum Gd, Eu and high concentrations of HREE often enriched in Th , U varying Ta-Nb and always low Zr-Hf.  Clinopyroxenes from the Malokuonamskaya pipe often have a local minimum of HREE and variations in the slope and enrichment of the REE spectra. On the CD, the peaks of Ba are varying, they show Ta, Nb enrichment and minima in Zr-Hf.

The garnets from the Universitetskaya pipe are mainly lherzolite-harzburgite with signs of subduction genesis (U peaks), and wide variations of HFSE sometime with Zr–Hf enrichment, due aqueous metasomatism. Clinopyroxenes are generally more diverse in REE spectra, Nb peaks with wide variations of Ba, Th-U and HFSE are common on CD

The Losi dike has a high content of perovskites, with highly enriched spectra with a slope with a decrease in highly charged and Pb and ilmenites with high and inclined REE spectra due to fractionation of proto-kimberlite (essentially carbonatite) melt. The eclogitic minerals with Eu anomalies and peaks of U, Ba and low HFSE are common.

In most mantle sections, ancient subduction sings are recorded in pyrope garnets, an partially adakite metasomatism in pyroxenes. Later they were modified by the action of plume carbonatite melts. The middle pyroxenite-eclogite lens originated as the boundary of the crust in ancient Archaic times. The upper wehrlitic part of the section arose during the melting of the pyroxene lens in the middle part and the migration of melts to the upper part. Protokimberlite metasomatism is not very pronounced. No signs of the supposed delamination of the lithosphere (Griffin et al, 2005) were found in the sections, which was also proved by Opx-Gar thermobarometry under the Duken field (Ashchepkov, 2003). The lower part of the section is depleted  so garnet and pyroxenes are rare and reflect low-temperature geotherm.

Grant RBRF 19-05-00788.

How to cite: Kostrovitsky, S., Ashchepkov, I., Medvedev, N., Karmanov, N., and Alymova, N.: Mineralogy and geochemistry of the kimberlite xenocrysts from the Anabar region, Yakutia, Russia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3860, https://doi.org/10.5194/egusphere-egu23-3860, 2023.

The fate of crust-derived melts at warm subduction zones and the transport mechanism of crustal components to the supra-subduction mantle is still matter of debate. Borgo outcrop of Monte Duria Area (Adula-Cima Lunga unit, Central Alps, Italy) is an excellent case study of melt-peridotite interaction occurred under a deformation regime at high pressure, that enabled the combination of porous and focused flow of eclogite-derived melts into garnet peridotites. Migmatised eclogites are in direct contact with retrogressed garnet peridotites and experienced a common high pressure (2.8 GPa - 750 °C) and post-peak (0.8–1.0 GPa - 850 °C) static equilibration. The contact is marked by a tremolitite layer, also occurring as boudins parallel to the garnet layering in the peridotites, derived from a garnet websterite precursor after the interaction between eclogitic melts and peridotites at high pressure. LREE concentrations of retrogressed websterites along a 120 m length profile starting from the eclogite-peridotite contact to the inner part of the peridotite, show a progressive enrichment coupled with a peculiar fractionation. Numerical modelling assuming the eclogitic leucosome as the starting percolating melt reproduces the REE enrichment and LREE-HREE fractionation observed in retrogressed websterites bulks within the first 30 m by two steps of melt-peridotite reaction: a high peridotite assimilation at eclogite-peridotite boundary, followed by reactive melt percolation within the peridotite assuming variable amounts of olivine assimilation and pyroxene + amphibole/phlogopite crystallisation. The numerical simulation aims to model the effect of interaction between crust-derived melts produced by partial melting of mafic slab component with suprasubduction mantle peridotites at sub-arc depths. The comparison between the REE composition of the retrogressed garnet websterites along the profile and the result of our model suggests that reactive melt infiltration at HP is a plausible mechanism to modify the REE budged of mantle peridotites that lie on top of the subducting crustal slab, which show peculiar LREE “spoon-like” fractionations. Moreover, the melt/peridotite interaction and the percolation of slab-derived melts into the overlying mantle may strongly modify the overall REE abundance and LREE/HREE fractionation (e.g., Ce_N/Yb_N) of the residual crustal melt within the first 30 m of slab/mantle interface.

How to cite: Malaspina, N., Borghini, G., Zanchetta, S., and Tumiati, S.: Geochemical interaction between slab-derived melts and mantle at high pressure in subduction zones, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6727, https://doi.org/10.5194/egusphere-egu23-6727, 2023.

The North China Craton (NCC) has been affected by the subduction and roll-back of the Paleo-Pacific Plate in the Mesozoic. To study the thinning of the lithosphere and the melting of the NCC, a three-dimensional (3-D) resistivity model of the lithosphere is obtained from a magnetotelluric sounding (MT) deployed in the NCC (Figure 1). In addition, the cause of the low resistivity of the upper mantle of the NCC can be solved by the Nernst-Einstein Equation and the Arrhenius Equation which is used to establish the relationship between the resistivity and temperature. Moreover, the Hashin-Shtrikman (HS) boundary conditions limit the range of electrical conductivity of mixed minerals (Figure 2). Based on the 3D resistivity structure, the temperature and melt fraction model, the lithospheric resistivity of the north of 37.5°N in the Ordos Block (OB), the southern Taihang Uplift (THU) and the Luxi Uplift (LXU) are as low as 1 Ωm which the upper mantle temperature is in the range of 1400 - 1550 °C, and the melt fraction is 1-10% in the high-temperature regions. According to the resistivity model and the thermal state, the westward subduction and roll-back of the Paleo-Pacific Plate provided conditions for upper mantle melting in the LXU and the Bohai Bay Basin (BBB). It also made the Tanlu Fault Zone (TLFZ) and THU channels for the upwelling, and the front of the Paleo-Pacific Plate stagnant slab is blowing the THU. With the remote tectonic stress of the Paleo-Pacific Plate and the Indian Plate, anticlockwise rotation of the OB induced the low resistivity of grabens and rifts around the OB (Figure 3). Moreover, upper mantle volatiles (H₂O and CO₂) and slight carbonatite melts significantly lower the mantle melting temperature.

* This work was supported by National Natural Science Foundation of China (Grants 41974112 and 40434010) and project SINOPROBE on sub-project SINOPROBE-01.

Reference:

Dong, S..T. Li. (2009). SinoProbe: the exploration of the deep interior beneath the Chinese continent. Acta Geologica Sinica, 83(7), 895-909.

Hirschmann, M. M. (2010). Partial melt in the oceanic low velocity zone. Physics of the Earth and Planetary Interiors, 179(1), 60-71.

Zhao, G..M. Zhai. (2013). Lithotectonic elements of Precambrian basement in the North China Craton: Review and tectonic implications. Gondwana Research, 23(4), 1207-1240.

Figure 1 Simplified s tectonic map of the North China Craton (modified from Zhao and Zhai (2013)); Map of MT profiles and sites, in which blue dots represent MT stations in this study, supported by the “SINOPROBE” project (Dong and Li, 2009). TNCO: Trans-North China Orogen 

Figure 2 Schematic diagram of dynamic changes of water and carbon dioxide during heating and melting of upper mantle minerals. NAMs means nominally anhydrous minerals; the “Calculate” in the dashed box is the calculation category of this study; the criterion for determining the interconnection of melts was proposed by Hirschmann (2010).

Figure 3 Schematic diagram of the possible formation mechanisms of the North China Craton inferred from the crustal and upper mantle 3-D resistivity model derived from this research.

How to cite: Li, B. and Ye*, G.: Three-dimensional Lithospheric Resistivity Structure and Thermal State of the North China Craton, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6901, https://doi.org/10.5194/egusphere-egu23-6901, 2023.

In the subcratonic lithospheric mantle (SCLM) beneath Leningrad pipe (West Ukukit field), Yakutia garnet thermobarometry allows us to identify seven horizons (paleo subduction slab). Microprobe data for Cr-bearing amphiboles >500 grains from mantle xenoliths and concentrates reveal a broad range of compositions changing from Cr- pargasitic hornblendes to pargasites, edinites, kataforites, К-richterites with increasing pressure determined with new amphibole thermobarometer.  The low pressure (LP) Cr-hornblendes and pargasites compiles the high-temperature branch (90-60 mw/m2) from 3.5 GPa to Moho traced by basaltic cumulates. In the middle part of SCLM edinites mark 35 to 40 mw/m2 geotherms. In the middle part of SCLM edinites mark 35 to 40 mw/m2 geotherms. At high pressures kataforites also vary in thermal conditions. Richterites near the lithosphere base trace both low –and high temperature convective branches.

 Age samples of aillikites estimated by 40Ar/39Ar age using the method described in detail by A. Travin et al. [40]. Quartz ampoules with samples were irradiated in the Cd-coated channel of a reactor (BBP-K type) at the Tomsk Polytechnic Institute. The gradient of the neutron flux did not exceed 0.5% of the sample size. Step-heating experiments were carried out in a quartz reactor with an external heater. The blank for 40Ar (10 min at 1200°C) was not higher than 5×10–10 cm3. Ar was purified using Ti and ZrAl SAES getters. The isotopic composition of Ar was measured on a Micromass Noble Gas 5400 mass spectrometer (analyst Yudin D.S.). The results of the dating of the phlogopite grains and amphiboles occurred in the intergroup with the Phl are shown the (Figure 1). The phlogopie from the spinel lherzolite 2665 Ma corresponding to the final stge of the craton formation. Similar age was determined for the Phl from Udachnaya. The age of the intergrowth of the Amph-Phl from the sample Ol-151 is splitting. The high temperature part with the age 1368Ma may be reffered to the global activization of the plume and accretion magmatism activity found in many World regions [42] including Siberia. The more yanger plateo is close to the 380-400 Ma which is just corresponds to the Devonian plume magmatism? And the small plateau ~210 Ma refer to Triassic The . As well in the sample Ol-112 the older one 370 Ma plateo just give Devonian age. And one of the younger 160 Ma corresponds to the Jurassic stage of kimberlite volcanism.

Presence of the Phl with the 2.6 Ga referring to the major event of the crust generaion corresponding to the beginning of mertasomatic H2O bearing metasomatic processes recorded in the mantle xenoliths in the World proves the common model of the appearance of water in the mantle  at the last stages of the continental growth, The other two peaks  400 -380 Ma and 160 Ma may be referred to the plume kimberlite magmatism and even to the protokimberlite stage (latest one). 

RBRF grant 19-05-00788

How to cite: Iudin, D., Ashchepkov, I., Babushkina, S., Oleinikov, O., and Medvedev, N.: Ancient mantle metasomatism in West Ykukite field Northern Yakutia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8651, https://doi.org/10.5194/egusphere-egu23-8651, 2023.

The small plutons of anorthosite and associated gabbronorite exposed near Barabar hills form a component of Chotanagpur granite gneiss complex (CGGC) in eastern India. Plagioclase (>90 vol %) make up the majority of anorthosite rock with minor mafic minerals (amphibole, mica), while orthopyroxene (>40 vol %), plagioclase (40-50 vol %) and clinopyroxene (>20 vol %) make up the associated gabbronorite. These are cumulate rocks with anorthosite and gabbronorite showing adcumulate and mesocumulate textures, respectively. Compositionally, plagioclase ranges from anorthite to labradorite (An_60-96) in anorthosite and from oligoclase to bytownite (An₅₀-₇₀) in gabbronorite. In gabbronorite, the clinopyroxene composition ranges from diopside to augite (En_36-43 Fs_12-15 Wo_43-47), and the orthopyroxenes are hypersthene (Wo_39-40 En_46-50 Fe_10–21).

Anorthosite show enrichment of LILE (Rb, Ba, Sr, Th, Pb) with respect to the HFSE (Zr, Ti, Nb and display enrichment in LREE ((La/Yb) _N = 2.78-15.29) with positive Eu anomaly (Eu/Eu* = 1.29-3.45) and variable MREE. A flat to depleted trend for HREE ((Sm/Yb) _N = 1.02-2.95) is observed for anorthosites. Associated gabbronorites show enrichment of LREE ((La/Yb) _N=1.99-4.93), depleted HREE ((Sm/Yb) _N = 0.88-3.24) with negative to positive Eu anomaly (Eu/Eu* = 0.78-2.95). Also, the gabbronorite shows enrichment of LILE (Rb, Ba, Sr, Th, Pb) compared to HFSE (Zr, Ti, Nb). Clinopyroxenes of gabbronorite have low REE abundances (53.29-60.29 ppm). Clinopyroxenes are depleted in light rare earth elements (LREEs) (La/Yb) _N = 0.75–0.80 and depleted in LILEs such as Ba, Sr. and also exhibit negative anomalies in Zr and Ti.

REE composition of gabbronorite clinopyroxene is constrained between TMF = 15-30% calculated using the equilibrium distribution method (EDM). This is substantiated by whole rock parental melt REE composition calculated using the concentration ratio approach (Nernst equation), the result of which is consistent with those made using EDM. In chondrite normalized plot, the estimated parental melt display (1) near-horizontal trend from Lu to Gd at rock/chondrite = ~100, (2) negative anomaly at Eu, (3) gradual rise from Sm to Ce and (4) slight dip from Ce to La.

How to cite: Negi, P., Belousov, I., Danyushevsky, L. V., Saikia, A., and Ahmad, M.: Anorthosite and associated gabbronorite plutons of Barabar hills in Chotanagpur granite gneiss complex (CGGC), eastern India: Estimation of parental melt for gabbronorite using equilibrium distribution method (EDM), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10859, https://doi.org/10.5194/egusphere-egu23-10859, 2023.

The suggested olivin thermometry for mantle peridotite and zenolith (Hoog et al., 2010, Bussweller et al., 2017) allow correct estimation of the temperatures using high precision data obtained by LA ICP MA or even EPMA inn hjigh resolution. IN this version we tried to obtain the pressure eestimates using the inversion of the Ol thermometer to barometer. And also we substituted the CaO by MnO withe essential correction. In this variant  I received the pair of the Ol thermometer and Mn - in - olivine barometer which allow to work not only with the high resolution data but with the routine analyses and obtain not bad estimates for the see of data for the Udachnaya, Zarnotsa, Aykhal and other pipes (Ashchepkov et al., 2010-2021) and even fo the diamond inclusions (Ashchepkov et al., 2021-2023). RBRF grant 19-05-007888

How to cite: Ashchepkov, I.: New formulation of the olivine thermobarometer for mantle xenoliths, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12275, https://doi.org/10.5194/egusphere-egu23-12275, 2023.

The study of mantle xenoliths from kimberlite pipes allows to establish the composition, evolution processes and thermal condition of the lithospheric mantle under ancient cratons. The Mirny kimberlite field belongs to the diamond-bearing kimberlite fields in the center of the Siberian craton. The collection of mantle xenoliths from the Mir pipe (57 samples) was investigated by authors. Four main petrographic groups were identified: peridotites (Grt lherzolites), Grt websterites, Grt clinopyroxenites and eclogites. The pyroxenite xenoliths attract the special attention.   

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 %). 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. 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.

In addition, websterites and lherzolites show a wide range of crystallization parameters (600 - 1200°C; 2 - 6 GPa) probably due to their gradual cooling after magmatic crystallization and the exsolution structures formation. Clinopyroxenites are characterized by narrow variations in the P-T crystallization parameters (812 - 960°C; 3-4 GPa) indicated their later crystallization from asthenospheric melts. Eclogites are characterized by relatively low calculated temperature parameters (720–840°C; 2.2–3.7 GPa) confirming their origin in subduction zones at shallow depths. The sporadic calculated values for websterites and clinopyroxenites are locating within the diamond stability area. The use of the Opx - thermobarometer (in samples founding Opx) revealed 2 trends in the crystallization of orthopyroxene. Crystallization of individual Opx grains in websterites occurred earlier than Cpx with higher P-T parameters - higher by ~100С and ~0.5 Ha. The second trend (pressure reduction with a slight decrease in temperature) notes the formation of Opx decay structures in an initially homogeneous crystal of monoclinic pyroxene. Minerals from pyroxenites demonstrate 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. The origin of eclogites is assumed from subducted oceanic crust marking the subduction component in the process of formation of the lithospheric mantle.

The research was supported by Russian Science Foundation grant № 22-77-10073.

How to cite: Kalashnikova, T. and Kostrovitsky, S.: The metasomatic processes and thermal condition of lithosphere mantle under the center of Siberian craton: evidences of pyroxenite xenoliths from Mir kimberlite pipe , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12888, https://doi.org/10.5194/egusphere-egu23-12888, 2023.

The Belo-Ziminsky alkaline-ultrabasic carbonatite massif contain dolomite, and calcite ankerite carbonatites essential part , syenites, melteigites and iolites cut by aillikite dikes of several generations (Ashchepkov et al., 2020; Doroshkevich et al., 2014-2021 etc). We analyzed  >4000 mineral grains by electron microscope in all types of rocks and >230 grains by  LA ICP MA  All rocks of the massif are derived from one type of mantle melt that was close to aillikite and formed at a level of >5 GPa in the mantle.

According to the nature of the PGE spectra –  and by serpentinized xenoliths in aillikites, this melt drained metasomatized enriched peorvskites and hydrogenated mantle and was initially very rich in HFSE. Above, at the level of the crust and the upper part of the mantle, the melt began to separate under liquation. In the lower and middle crust, several (3) magmatic chambers were probably formed sequentially, which separated various carbonate and silicate melts, and from dolomite to ankerite melts, judging by the slope, the number of grains in the source decreased, that is, the melts became less deep and more fractionated.

These trends are reflected both in the composition of pyroxenes from aillikites  and in the PTX diagram . All this led to significant variations in rocks and their rare-earth spectra of all rocks

How to cite: Zhmodik, S., Ashchepkov, I., Kiseleva, O., Belyanin, D., Sotnikova, I., Medvedev, N., and Karmanov, N.: Tracing of evolution of carbonatite and silicate melts of the Belo-Ziminsky alkaline-ultrabasic carbonatite massif by mineralogy and geochemistry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16857, https://doi.org/10.5194/egusphere-egu23-16857, 2023.

Shallowing of slabs during their descend into the upper ~200 km of the mantle, i.e. flat subduction, can be associated with extensive geochemical, structural, and dynamic modification of the continental lithosphere. Anomalously buoyant oceanic lithosphere, overthrusting, and interactions with cratonic keels have been suggested to explain flat slabs, but the dynamics of flat slab subduction remain to be fully understood. Here, we explore self-consistent flat-slab subduction using the finite element code ASPECT with adaptive mesh refinement and a free surface boundary condition. We focus on the role of the structure of the overriding continental plate including the role of keels. Results show that flat slabs arise when the subduction interface is weak and the overriding continental lithosphere is positively buoyant, leading to trench rollback. Substantiating previous work, we also observe that a strong continental keel further enhances flat slab formation. Our results also indicate that as the slab flattens, regions of pronounced subsidence and extension develop within the foreland region, on top of more typical, larges-scale subsidence recorded within the continental interior. Regional uplift and subsidence of the overriding plate are not only linked to flat slab emplacement and removal, but also affected by slab dynamics of the shallow upper mantle. Our work can contribute to a better understanding of continental deformation including sediment transport on continent-wide scales.

How to cite: Grima, A. G. and Becker, T.: Modeling the interactions between slab dynamics and continental overriding plate deformation during flat subduction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1322, https://doi.org/10.5194/egusphere-egu23-1322, 2023.

Slab break-off is usually referred to as an early collisional process driven primarily by the slowing of the subduction rate as negatively buoyant oceanic lithosphere detaches from positively buoyant continental lithosphere that is attempting to subduct. In this context, slab tearing (or slab break-off propagation) is traditionally attributed to continental corner dynamics, when the subducting plate first detaches in the area of continental collision and then the slab window opens toward the adjacent segment of the convergence boundary, where ocean-continent subduction continues. Another important process, previously thought to be independent of slab break-off and horizontal slab tearing, is a fragmentation of the subducting slab along vertical planes perpendicular to the convergence direction. Previous numerical studies have linked this vertical slab tearing to pre-existing weakness within the subducting plate and/or abruptly changing convergence rates along the trench.

In our study, we use a 3D thermo-mechanical numerical approach to study slab tearing in a non-collisional geodynamic context. The effects of subduction obliquity angle, age of oceanic slab, and partitioning of boundary velocities have been investigated. We show, for the first time, that horizontal and vertical slab tearing are different stages of the same process, which can develop in a self-sustained manner in a non-collisional environment of oblique ocean-continent subduction. Even with an initially absolutely homogeneous oceanic plate and laterally unchanging and temporally constant boundary velocities, the obliquity of the active margin appears to be a sufficient factor to trigger complex system evolution, which includes the transition from horizontal to vertical slab tearing along with additional processes such as retreat and rotation of the trench, decoupling of the overriding and downgoing plates by upwelling asthenosphere in the mantle wedge (also termed “delamination”), initiation of new subduction, and formation of a transform fault.

Our results show striking similarities with several features – such as trench curvature, subduction zone segmentation, magmatic production, lithospheric stress/deformation fields, and associated topographic changes – observed in many subduction zones (e.g., Marianas, New Hebrides, Mexico, Calabrian).

How to cite: Koptev, A., Andrić-Tomašević, N., Maiti, G., Gerya, T., and Ehlers, T.: Horizontal and vertical slab tearing as different stages of a self-sustaining process developing in a non-collisional setting with oblique subduction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1559, https://doi.org/10.5194/egusphere-egu23-1559, 2023.

Subduction of oceanic lithosphere has been proposed as the main driving mechanism for plate tectonics for decades and it represents a key process for the geochemical cycles on Earth. However, the physical processes and melting that occur as the subduction zone began foundering and evolved to reach a mature stage is still debated. The Izu-Bonin-Mariana (IBM) intra-oceanic subduction zone, that represents the boundary between the Pacific Plate and the Philippine Sea, is an ideal natural laboratory to study subduction zone processes from their inception to their stabilization. The rock record produced in IBM reveals a rapid compositional variability in slab-fluid tracers as well as in mantle depletion-enrichment over a short timescale (within 1 to 5 Ma of subduction inception). Despite this geochemical evolution, it is still highly debated whether IBM initiated as a forced or spontaneous subduction zone, i.e. induced by or in the absence of horizontal forcing, respectively.

Here, we conducted 2D high-resolution petrological-thermomechanical subduction models that include spontaneous deformation, erosion, sedimentation and slab dehydration processes, as well as melting, assuming a visco-plastic rheology using the i2VIS code. We aimed to model the initiation and the early stage of IBM with ultra-low horizontal forcing and inception triggered by transform collapse. Our new numerical model proposes a viable scenario for the transition from juvenile to mature subduction zone. This evolution includes initiation by gravitational collapse of the slab and the development of a near-trench spreading, the gradual build-up of a return flow of asthenospheric mantle and the progressive maturation of the volcanic arc. Our numerical results of mantle depletion within the mantle wedge and the overall subduction history of IBM are compared further with seismological and geochemical evidences.

How to cite: Ritter, S., Balázs, A., Ribeiro, J., and Gerya, T.: Magmatic Fingerprints of Subduction Initiation and Mature Subduction of the Izu-Bonin-Mariana Subduction Zone: Numerical Modelling and Observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2071, https://doi.org/10.5194/egusphere-egu23-2071, 2023.

Because Earth's tectonic plates are doubly curved shells, their mechanical behavior during subduction can differ significantly from that of flat plates. We use the boundary-element method (BEM) to study free (gravity-driven) subduction in axisymmetric and 3-D geometry, with a focus on determining the dimensionless parameters that control the dynamics. The axisymmetric model comprises a shell with thickness h and viscosity η₁ subducting in an isoviscous planet with radius R₀ and viscosity η₂. The angular radius of the trench is θ_t. Scaling analysis based on thin-shell theory reveals two key dimensionless parameters: a `flexural stiffness' St = (η<sub>1</sub>/η<sub>2</sub>)(h/l<sub>b</sub>)<sup>3</sup> that is also relevant for flat plates, and a new `dynamical sphericity number' Σ_D = (l_b/R₀)cotθ_t that is unique to spherical geometry. Here l_b is the `bending length', or the sum of the lengths of the slab and of the seaward flexural bulge. The definition of Σ<sub>D</sub> implies that the dynamical effect of sphericity is greater for small plates than for large ones; we call this the `sphericity paradox'. By contrast, the purely geometric effect of sphericity is opposite, i.e. greater for large plates than for small ones. The dynamical and geometrical effects together imply that sphericity significantly influences subduction at all length scales. We confirm the scaling analysis using BEM numerical solutions, which show that the influence of sphericity on the slab sinking speed (up to a few tens of percent) and on the hoop stress (up to a factor of 2-3) is largest for small plates such as the Juan de Fuca, Cocos and Philippine Sea plates. We next study a 3-D model comprising a plate bounded by a ridge and a semicircular trench subducting in a three-layer earth consisting of an upper mantle, a lower mantle and an inviscid core. We examine the linear stability of the shell to longitudinal perturbations corresponding to buckling, and determine a scaling law for the most unstable wavelength that we compare with the observed shapes of northern/western Pacific trenches. 

How to cite: Ribe, N., Chamolly, A., Gerardi, G., Chaillat, S., and Li, Z.: Scaling of Free Subduction on a Sphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2103, https://doi.org/10.5194/egusphere-egu23-2103, 2023.

The tectonic exhumation of mantle material is a well-known phenomenon and may occur during both rifting and subsequent (large-scale) basin inversion. However, the processes leading to the exhumation of dense and therefore negatively buoyant (sub-)lithospheric mantle material remain poorly understood. We therefore conducted a series of thermomechanical simulations using the geodynamics code ASPECT (coupled with FastScape for the inclusion of surface processes) testing the impact of various parameters on mantle exhumation in inverted rift systems.

We find that rift duration strongly impacts mantle exhumation, both during the rift phase, as well as during subsequent inversion. When only limited rifting is applied, the dense mantle material cannot reach the surface as the overlying crustal layers remain connected. Basin inversion then tends to create a symmetric pop-up structure by reactivating rift boundary faults, and the dense mantle material is forced down by the thickening of low-density crustal layers on top of it. Only after certain amount of extension, the crust is sufficiently thinned so that mantle material can be exhumed. This mantle material may then remain near the surface or be further exhumed during basin inversion. Such further mantle exhumation is favoured if asymmetric reactivation of the rift basin occurs, so that mantle material is thrust on top of the downgoing plate.

The establishment of such asymmetric orogenic systems allowing for efficient mantle exhumation is further promoted by having only short-lived tectonic quiescence between rifting and inversion, so that no thermal equilibration of the exhumed mantle domain can occur. As a result, the rift basin remains a weakness that is readily exploited during inversion. Longer periods of tectonic quiescence restore the strength of the lithosphere, so that delayed inversion generates more symmetric structures, with limited opportunities for mantle exhumation.

Within this tectonic context, erosion efficiency is another key factor. First, more efficient erosion during inversion removes crustal material so that the mantle can be exhumed (even in symmetric orogenic systems). Second, efficient erosion also leads to the development of asymmetric orogenic systems, thus doubly contributing to mantle exhumation. Somewhat similarly, high plate velocities during inversion introduce larger amounts of crustal material into the system, which erosion cannot remove in a timely manner, whereas slow plate velocities allow erosion more time to remove material. Hence, mantle exhumation is positively correlated to erosion efficiency, and is negatively correlated to plate velocities during inversion

Finally, serpentinization of mantle material can occur close to the Earth’s surface (i.e. in the uppermost kilometres) and strongly reduces the material’s density and brittle strength. Although our models so far only show a limited effect of serpentinization, the overall weakness of serpentinized mantle material at the rift basin floor seems to reduce localization of inversion-related deformation, thus generating more symmetric inversion systems with limited mantle exhumation.

How to cite: Zwaan, F., Brune, S., Glerum, A., Naliboff, J., and Vasey, D.: Numerical modelling of mantle exhumation in inverted rift systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2573, https://doi.org/10.5194/egusphere-egu23-2573, 2023.

The Mariana convergent margin provides the environment where a natural process brings materials from great depths directly to the surface. The Mariana forearc contains the only current active serpentine mud volcanism in a convergent margin setting. Here, serpentinite mud volcanoes are numerous, large (averaging 30 km diameter and 2 km high) and active. They are composed principally of unconsolidated flows of serpentine muds containing clasts of serpentinized mantle peridotite and several other lithologies, such as blueschist materials derived from the subducting slab.

IODP Expedition 366 recovered cores from three serpentinite mud volcanoes at increasing distances from the Mariana trench subduction zone along a south-to-north transect: Yinazao (Blue Moon), Fantangisña (Celestial), and Asùt Tesoru (Big Blue). These cores consist of serpentinite mud containing lithic clasts and minerals derived from the underlying forearc crust and mantle, as well as from the subducting Pacific Plate. Fluids upwell within these mud volcanoes at a rate that is in excess of the mud matrix. Such fluids originate from the downgoing plate but are highly altered, are reducing and have pH values in the range of 9 to 12.5.

For the purposes of this study ultramafic and mafic rock clasts from the flanks and summits of both Asùt Tesoru and Fantangisña Seamounts were analyzed in order to reconstruct processes of fore-arc mantle alteration, fluid activity and fluid-rock interaction. Additionally, several samples from Asùt Tesoru Seamount consisting of cryptocrystalline serpentine mud with commonly occurring lithic clasts (>2 mm) in different amounts and size were investigated.

In general the mineral paragenesis of the serpentinized peridotite clasts, including mainly lizardite and chrysotile serpentine group minerals, along with brucite as well as andradite, and the apparent absence of high-temperature phases such as antigorite and anthophyllite, tentatively constrains an upper temperature limit of 200 – 300 °C. However, the presence of fine-grained matrix antigorite associated with lizardite suggests metamorphic temperature of at least 340 °C.

Hydrogarnet is a common secondary, hydrothermal mineral phase in the studied samples and it defines a serpentinization temperature of c. 230 °C. Garnet crystals with subhedral habitus and almost pure andraditic composition are found within a carbonate matrix. However, also Cr-rich garnets are common within the serpentinite clasts. They are subhedral to anhedral and contain chromite inclusions with similar composition to the unaltered chromites in the same sample. These textural observations suggest a secondary origin for the Cr-rich garnets as well, most probably related to hydrothermal fluids that infiltrated the ultramafic protolith. The formation of Cr-rich garnet after Cr-rich spinel is usually associated with hydrothermal or metasomatic reactions, although the precise mechanism of formation remains unclear. Generaly Cr-rich hydrogarnets in serpentinites crystallize below 400 °C, which is in line with the obtained metamorphic conditions and indicate an overall evolution of a hydrothermal fluid from c. 350 °C (antigorite in serpentinites) to c. 100 °C and below.

How to cite: Kurz, W., Miladinova, I., Krenn, K., and Hilmbauer-Hofmacher, T.: Fore-arc mantle alteration, fluid activity and fluid-rock interaction revealed from Serpentinite Mud Seamounts at the Mariana Convergent Margin System (IODP Expedition 366), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2657, https://doi.org/10.5194/egusphere-egu23-2657, 2023.

Early Cretaceous Nidar Ophiolite Complex (NOC, eastern Ladakh) is associated with the north-dipping supra-subduction of the Neo-Tethyan Ocean along the Indus suture zone. The supra-subduction zone ophiolite formed in the forearc setting records the magmatic response to the subduction initiation, but the magmatic evolution in the NOC is poorly constrained. The low-Ti gabbros have low SiO₂ in whole-rock composition and high Mg# in clinopyroxene. They also record highly depleted magma In contrast, dolerites and basalts have relatively higher SiO₂ in whole-rock composition and lower Mg# in clinopyroxene, with flat REE patterns accompanied by fractional crystallization. Significant variation in Yb content relative to Tb/Yb ratio also supports fractional crystallization from gabbros to basalts. In Th/Yb-Nb/Yb diagram, all samples plot in the region from the MORB type to the island arc tholeiite. The Nd-Sr isotopes and high Ba/La ratio suggest that the NOC was originally derived from a single depleted mantle source similar to the MORB and was subsequently affected by hydrothermal alteration, resulting in greenschist- to lower amphibolite-facies overprint to form albite, actinolite, epidote and chlorite. Detrital zircon U-Pb ages from volcanic sediments associated with the NOC concentrated at ca. 136 Ma, representing the timing of the main magmatic phase in the NOC. Our data, combined with the geochronological and geochemical data in previous studies, suggest that the low-Ti, highly depleted magma in the NOC was firstly generated at extensional spreading in the upper plate during subduction initiation, and then changed to island arc tholeiite composition with the development of the subduction zone during Early Cretaceous.

How to cite: Imayama, T., Sato, A., Dutta, D., Kaneda, Y., Watanabe, S., Hasegawa, T., Minami, M., Wakasugi, Y., Wakaki, S., and Keewook, Y.: Magmatic response to the subduction initiation of Early Cretaceous Nidar Ophiolite Complex, eastern Ladakh, NW Himalaya, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2981, https://doi.org/10.5194/egusphere-egu23-2981, 2023.

How to cite: Arias, A., Beinlich, A., Eberhard, L., Scambelluri, M., John, T., Kotowski, A., and Plümper, O.: Micro to Macroscale: the three-dimensional network characteristics of serpentinite dehydration veins, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3130, https://doi.org/10.5194/egusphere-egu23-3130, 2023.

Intra-oceanic arc’s collision with an oceanic plateau plays a crucial role in the development of complex tectonic setting and induce subduction polarity reversal. Despite several studies and investigations, the origin and timing of subduction initiation in Solomon Island Arc (SIA) is still ambiguous. This study presents first robust zircon U-Pb ages and in-situ Hf isotope data from Choiseul, Santa Isabel (SI) and New Georgia Group (NGG), three major islands of SIA. Magmatic zircons and Hf isotope data from one gabbro sample, geochemically identical to N-MORB with Nb, Ta depletion in spidergram yielded 46 ± 1 Ma, which we decipher as the timing of Stage I magmatism by subduction of Pacific plate and subduction initiation in Choiseul. Six Choiseul andesites gave a mean age ²⁰⁶Pb/²³⁸U of 0.7 Ma, with ε_Hf(t) values from +9 to +15 which represents the youngest crystallization age of Stage II magmatism with typical island arc-like signatures and a depleted mantle source. Detrital zircons from two sand sample yielded a population of mean age ranging from 0.3-0.7 Ma, 10 Ma and 48-46 Ma with ε_Hf(t) values +9 to 15, +11 to +12 and +11 to +14 respectively and third sample has yielded a mean age ²⁰⁷Pb/²⁰⁶Pb 2.6 Ga and 500-1600 Ma with ε_Hf(t) values -8 to +9, probably associated with Australian-type source indicating presence of a continental fragment beneath SIA. 

Similar ages of ca. 2.6 Ma have been obtained from inherited zircons from three gabbroic dyke sample from Santa Isabel with ε_Hf(t) values +1 to +9 whereas one gabbroic dyke sample yields 110 ± 1 Ma, with ε_Hf(t) values +14 to + 16 which we interpret as the basement age of SI.

U-Pb dating of zircons from mafic to felsic rocks along NGG, covered mostly by Quaternary eruptive lavas. The youngest age population indicate Late Pliocene-Pleistocene ²⁰⁶Pb/²³⁸U ages, 2.5-1.5 Ma, interpreted as  zircon crystallization ages of Stage II arc magmatism resulting from subduction of the Solomon Sea plate, as those of Choiseul Andesite. The first U-Pb age from ca. 36.8±0.5 Ma granite on Ghizo Island in New Georgia Group, revealing Late Eocene-aged magmatic zircon. This age represents the magmatic emplacement as the basement of plutonic rock from NGG that has not been reported before.

We conclude that, (i) The Solomon Islands has a Cretaceous basement preserved in SI. (ii) The timing of subduction initiation and Stage I N-MORB type tholeiitic magmatism in SIA is 46 Ma followed by episodic eruptions from the early Eocene to late Eocene. (iii) Oligocene (30-20 Ma) magmatic hiatus, probably the time of subduction polarity reversal from subduction of Pacific plate to subduction of Solomon Sea plate. (iv) Stage II island arc magmatism initiated at 20-18 Ma in NGG to youngest emplacement age of Pliocene to Pleistocene in Choiseul as well as in NGG. (v)Abundant Archean zircons are present in samples from all three islands, indicate presence of micro-continent beneath Islands of Solomon. We are still working on the whole rock isotopic analysis to better constrain the tectonic and magmatic evolution of SIA.

How to cite: Battan, R., Nguyen, T. T., Chung, S.-L., Komiya, T., Maruyama, S., Lin, A. T.-S., Lee, H.-Y., and Izuka, Y.: From Subduction Initiation to Polarity Reversal: Zircon Age and Geochemical Constraints from Solomon Islands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4422, https://doi.org/10.5194/egusphere-egu23-4422, 2023.

Shifts in isotopic and trace element composition in magmatic zircon are commonly related to internal forcing independent of plate parameters (e.g., crustal thickness, delamination), or external factors that are governed by parameters of the down-going plate, particularly the slab dip. U-Pb geochronology, trace elements and Hf-O isotope analyses on detrital zircon from central Patagonia (45 °S – 48 °S) were used in this study as fingerprint for monitoring slab dip variations and related processes (e.g., arc migration, slab rollback) as well as upper-plate stress regime evolution. According to literature, main geodynamic events include: (i) two shallow slab episodes during late Triassic and late Early Cretaceous – early Paleogene times, the latter characterized by significant contraction; (ii) two phases of slab rollback during Jurassic – Early Cretaceous and late Paleogene, associated to a steep slab configuration, extensional processes and crustal thinning; (iii) a slab window episode during the Paleogene; and (iv) a Miocene contractional phase following an increase of plate convergence rates. Although slab dynamics seems structurally related with upper-plate architecture, it appears to exert little to null control on the magmatic arc reservoirs. Indeed, our results, integrated with published data from a larger area (40 °S – 52 °S), show long-lasting trends ( > 70 Ma) in the isotopic and trace elements record, that are mostly independent of these events. We thus consider that other processes, eventually coeval, controlled the enrichment of magmas and may overtake the influence of slab dip and upper-plate architecture on the isotopic and trace elements signature. These other processes include subduction erosion, ridge subduction, subduction of a younger slab, potential slab tearing, and/or change in convergence rates that affects mantle flow. 

How to cite: Genge, M., Witt, C., Zattin, M., Bosch, D., Bruguier, O., and Mazzoli, S.: Are the long-lasting isotope trends in central Patagonia independent from slab dynamics and upper-plate architecture?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4644, https://doi.org/10.5194/egusphere-egu23-4644, 2023.

It has long been recognised that the shape of subduction zones is influenced by Earth’s sphericity, but the effects of sphericity are regularly neglected in numerical and laboratory studies that examine the factors controlling subduction dynamics: most existing studies have been executed in a Cartesian domain, with the small number of simulations undertaken in a spherical shell incorporating plates with an oversimplified rheology, limiting their applicability. There are therefore many outstanding questions relating to the key controls on the dynamics of subduction. For example, do predictions from Cartesian subduction models hold true in a spherical geometry? When combined, how do subducting plate age and width influence the dynamics of subducting slabs, and associated trench shape? How do relic slabs in the mantle feedback on the dynamics of subduction? These questions are of great importance to understanding the evolution of Earth's subduction systems but remain under explored.

In this presentation, we will target these questions through a systematic geodynamic modelling effort, by examining simulations of multi-material free-subduction of a visco-plastic slab in a 3-D spherical shell domain. We will first highlight the limitation(s) of Cartesian models, due to two irreconcilable differences with the spherical domain: (i) the presence of sidewall boundaries in Cartesian models, which modify the flow regime; and (ii) the reduction of space with depth in spherical shells, alongside the radial gravity direction, the impact of which cannot be captured in Cartesian domains, especially for subduction zones exceeding 2400 km in width. We will then demonstrate how slab age (approximated by co-varying thickness and density) and slab width affect the evolution of subducting slabs, using spherical subduction simulations, showing that: (i) as subducting plate age increases, slabs retreat more and subduct at a shallower dip angle, due to increased bending resistance and sinking rates; (ii) wider slabs can develop along-strike variations in trench curvature due to toroidal flow at slab edges, trending toward a `W'-shaped trench with increasing slab width, and (iii) the width effect is strongly modulated by slab age, as age controls the slab's tendency to retreat. Finally, we will show the diverse range of ways in which remnant slabs in the mantle impact on subduction dynamics and the evolution of subduction systems.

How to cite: Davies, R., Chen, F., Goes, S., and Suchoy, L.: Controls on the Dynamics of Subducting Slabs in a 3-D Spherical Shell Domain, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4710, https://doi.org/10.5194/egusphere-egu23-4710, 2023.

Oceanic plates are far from homogeneous, and a large number of bathymetric discontinuities such as seamounts of different sizes are transported along by plate motion towards the mid ocean trenches and beyond. Seamounts currently colliding with plate margins show a major role in shaping the forearc morphology, and several studies even suggest that they might be related with seismicity. However, it is not clear what happens after seamounts are subducted, they can be accreted to the forearc, carried down into the subduction zone and recycled into the deep mantle, or a mix of the two scenarios. Using high-resolution two-dimensional thermomechanical numerical simulations, we investigate subduction processes of oceanic plates with a heterogeneous structure marked by a series of basaltic seamounts arranged in a chain like structure. We solve the 2D momentum, continuity and energy equations with the finite differences coupled with PIC (particle-in-cell) method. Our models also incorporate a depth-dependent, realistic non-Newtonian visco-elasto-plastic rheology, and plasticity is implemented using a yield criterion which limits the creep viscosity. Preliminary results show that initially seamounts preserve they structure when impacting with the trench. Their integrity is partially conserved until they subduct to a depth of about 25-30 km when they finally start to succumb to the great deformations and stresses along the slab interface. We observed that the lower part of the seamount continuously deforms and amalgamates along the slab interface. The upper part is detached and incorporated into the forearc structure. The subsequent seamounts that trail the first seamount, follow the same deformation pattern, and the top of them are maintained in the highly deformed forearc region. Our preliminary modeling results confirm that seamount subduction represent a key tectonic process that influences on a long-term time scale the structure and evolution of subduction zones.

How to cite: Manea, V. C., Manea, M., and Petrescu, L.: Subduction of bathymetric irregularities along active margins: insights from numerical modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5078, https://doi.org/10.5194/egusphere-egu23-5078, 2023.

The subduction zone interface is a shear zone of varying thickness that defines the boundary between the subducting slab and overriding plate. The rheology of this shear zone controls several important aspects of subduction dynamics, but accurately estimating its rheology can be complex due to the wide range of subduction materials and their varying rheological properties. Of particular importance is the relative strengths of metasedimentary and metabasic rocks at various temperature and pressure conditions. To better understand these rheological contrasts in naturally deformed rocks, we are conducting field and microstructural work in the Eclogite Zone in the Tauern Window, Austria. The eclogite zone preserves intercalated metamafic (metabasalt and metagabbro) and metasedimentary (quartzite, garnet mica schist, marble and calc-schist) rocks that were subducted and exhumed to the surface as a single structural unit. Using high resolution drone imaging, 2D structural mapping, and 3D structural modeling, we have documented map-scale relationships between metamafic and metasedimentary rocks in the Eissee region near Matrei. Our mapping demonstrates that the mafic eclogites consistently define slabs, lenses and boudins of up to 2 km in along-strike length and 0.2 km in thickness, embedded within the metasedimentary units, all of which are relatively uniformly deformed to very high strain. This suggests that eclogitized metamafic rocks persisted as rheological heterogeneities within the subduction channel through both the subduction and exhumation paths. Additionally, we are using microstructural observations to document the deformation mechanisms of individual rock units and to understand the weakening mechanisms that allowed some of the eclogites to break down from boudins to strongly foliated layers intercalated with the metasediments. At the interface between select metasedimentary and eclogite units there is a marked rheological change in eclogite rheology, likely due to fluids leached from the metasedimentary rocks, resulting in strain localization and increased foliation development within eclogite layers from meter to micron length scales. Integration of our mapping, outcrop, and microstructural observations will provide insights into the length scales of rheological heterogeneity on the deep interface and large-scale geodynamics of subduction through influencing the bulk viscosity of the interface.

How to cite: Tokle, L., Behr, W., Braden, Z., and Cisneros, M.: Persistence of initial lithological heterogeneity to deep subduction conditions: Implications for the rheology of the subduction zone interface, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5162, https://doi.org/10.5194/egusphere-egu23-5162, 2023.

How to cite: Brizzi, S., Becker, T., Faccenna, C., Behr, W., van Zelst, I., Dal Zilio, L., and van Dinther, Y.: The role of sediments on subduction dynamics and geometry: insights from numerical modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5221, https://doi.org/10.5194/egusphere-egu23-5221, 2023.