Pyrite, for example, is the most common sulphide in the Earth’s crust and occurs in many different types of rock. The mineral can be used to reconstruct a range of bio- and geological processes across a broad spectrum of scales. In the oceans, pyrite is the dominant sink for reduced sulphur and is intimately connected to biological pathways of sulphate reduction. On land, pyrite weathering can be a geologically relevant process leading to carbon release to the atmosphere. As a major gangue mineral phase in hydrothermal ore deposits, the formation and geochemistry of pyrite can be used to investigate and potentially detect ore forming processes.
Orals: Thu, 7 May, 14:00–15:45 | Room -2.43
Geochemical proxies are routinely interpreted as the outcome of abiotic fluid–rock interactions governed by pressure, temperature, and thermodynamic equilibrium. However, Earth’s subsurface hosts a vast and active biosphere up to several km depth that can alter the chemistry and isotopic composition of fluids and gases across a wide range of geological settings (Magnabosco et al. 2018; Giovannelli et al. 2022). Subsurface microorganisms are able to interact with volatiles such as H2, CH4, CO2, and H2S, and actively cycle key elements including C, S, N, Fe, and trace metals (Hay Mele et al. 2023), often inducing isotopic and compositional shifts that can overprint the signature of purely inorganic processes (Giovannelli et al. 2022; Barry et al. 2019). In this talk, I argue that subsurface microbiology represents a first-order control on many geochemical proxies used in resource exploration and management. I will review current knowledge on subsurface microbial communities and show how microbial metabolisms can reshape redox conditions, regulate gas accumulation and consumption, influence mineral precipitation and dissolution, and generate diagnostic, but frequently overlooked, geo(bio)chemical signatures. Using recent geomicrobiological data collected from diverse geological settings, I will demonstrate how biological activity can decouple classical geochemical tracers from their assumed abiotic origin. Finally, I will discuss emerging strategies to explicitly integrate microbiological processes into models and exploration workflows, to improve predictive frameworks and risk-assessment approaches for subsurface resources such as natural hydrogen, underground hydrogen storage, and carbon storage (Tyne et al., 2022; Cascone et al., 2025). Recognizing and quantifying the role of life in the subsurface is essential to correctly interpret geochemical data, reduce exploration uncertainty, and enable more robust and sustainable geological resource management.
Citations
Barry et al. 2019. Nature, 568: 487-492.
Cascone et al. 2025. EarthArXiv, 8350: 1-35.
Giovannelli et al. 2022. Front, in Microbiol., 13: 998133.
Hay Mele et al. 2023. Essays in Biochem., 67: 1-18.
Magnabosco et al. 2018. Nature Geosci., 11: 707-717.
Tyne et al. 2023. Environ. Sci. Technol., 57(26): 9459-9473.
How to cite: Giovannelli, D.: The Living Subsurface: Microbial overprinting of subsurface geological processes and implications for natural resource exploration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20886, 2026.
The sustainable exploration and management of unconventional resources, such as oil shale and low-maturity shale oil, require a predictive understanding of fluid-rock interactions under in-situ pressure-temperature conditions. This study integrates high-pressure hydrous pyrolysis with comprehensive geochemical and petrophysical analyses to unravel the coupled effects of thermal maturation, geological pressure, water, and rock composition on hydrocarbon generation, pore evolution, and the development of diagnostic geochemical tracers.
Sequential pyrolysis experiments (350–420 °C, up to ~600 bar) on immature lacustrine shales (Type I and II kerogen) simulated burial depths of 1.8–6.0 km. Results demonstrate that water and pressure are critical, non-passive factors. Water acts catalytically, significantly accelerating hydrocarbon generation, organic matter maturation, and nanopore development—the latter experiencing an additional 1.9–4.5-fold pore volume increase in wet gas stages compared to anhydrous systems. Pressure exerts a dual regulatory role, generally enhancing liquid yield and suppressing gasification, while also impeding expulsion efficiency, leading to viscous bitumen retention.
Crucially, biomarker systems evolve predictably under these simulated geo-conditions. Parameters such as C29 and C30 βα/αβ hopane ratios, C31-C32 22S/(22S+22R) homohopane ratios, and C29 ααα 20S/(20S+20R) sterane ratios show systematic progressions with maturity, providing robust, non-destructive proxies for monitoring thermal evolution. In contrast, Pr/Ph and Ts/(Ts+Tm) ratios are less reliable under these conditions. These geochemical signatures, alongside declining gas dryness indices, form a reliable tracer suite for assessing subsurface conversion progress.
Furthermore, pore network evolution is governed by a synergy of thermal maturity, kerogen type, and mineralogy (e.g., carbonate dissolution, clay stability), all mediated by the presence of water and internal pore pressure. This moves beyond maturity-centric models to a holistic shale-water-pressure framework.
Our findings establish that in-situ conversion (ISC) can be effective at temperatures (350–420 °C) lower than those used in ex-situ retorting, validating prolonged heating as a low-energy strategy. The integrated geochemical and petrophysical framework presented here provides essential constraints for optimizing ISC processes, enabling the use of advanced geo(bio)chemical tracers for real-time monitoring and contributing to the sustainable and efficient exploitation of deep unconventional resources.
How to cite: Bai, F., Uguna, C. N., Sun, C., Guo, W., Li, Q., Deng, S., and Zhu, C.: Geochemical and Biomarker Constraints from High-Pressure Hydrous Pyrolysis: Implications for Monitoring and Optimising In-Situ Conversion of Unconventional Resources, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1913, 2026.
Natural hydrogen here refers to H2 produced abiotically by water-rock reactions such as serpentinization and radiolysis at naturally occurring rates. Decades of research have focussed towards understanding the spectrum of hydrogen producing reactions, the role of hydrochemistry, mineralogy and rock types, and recently, mapping the accumulations of such natural hydrogen around the world – particularly in continental systems [1]. The Precambrian continents are of particular interest as they host the largest extent of ultramafic rocks on the planet – including the so-called “greenstone belts”. To date, this research into natural hydrogen has largely been done by geochemists, microbiologists, astrobiologists and planetary scientists focused on the search for life in the Earth’s subsurface biosphere, or on other planets and moons in the solar system. Under this lens, microbial ecosystems have been broadly identified in the subsurface, sustained by hydrogen producing water-rock interactions in the continental crust and at the deep ocean vents and seafloor. Only recently have human populations begun to consider competing with their microbial cousins for this subsurface resource on a global scale. As a result, detailed integration of geo(microbio)chemistry into quantitative evaluation of sources and sinks for natural hydrogen has arguably been neglected by many programs investigating the economic potential for this natural resource.
Based on ground-based and subsurface measurements, Sherwood Lollar et al. (2014) and subsequent papers [1,2] demonstrated that saline fracture waters in the Precambrian continental subsurface are as rich in hydrogen as hydrothermal vents and seafloor spreading centres, and similarly produce hydrogen by a combination of hydration of mafic and ultramafic minerals and by radiolysis [3-5]. Here we provide the long-term (>10 year) monitoring data of hydrogen concentrations, volumes, and discharge rates collected from a site located in a major regional industry hub, with this location representative of many additional potential sites in close proximity in a Precambrian continental setting where natural hydrogen may likewise be available. The analysis demonstrates the hydrogen related to an active mine such as previously described in Albania [6] is not a unique phenomenon and may be more widespread and more volumetrically significant than previously identified. This raises the possibility of readily available natural hydrogen being tapped for local use in regional industry hubs where other extraction activities are already underway, and energy supply remains a critical concern. Co-investigation of microbiological communities and sinks for hydrogen are an important component of this evaluation.
[1] Sherwood Lollar et al., 2014 Nature 516 (7531): 379-382
[2] Warr et al., 2019 Chemical Geology 530:11932
[3] Lin et al., 2005 GCA 69(4):893-903
[4] Li et al., 2016 Nature Communications 7:13252
[5] Sherwood Lollar et al., 2021 GCA 294:295-314
[6] Truche et al., 2024 Science 383:618-621
How to cite: Sherwood Lollar, B. and Warr, O.: Natural Hydrogen Opportunities: The role of geo(bio)chemistry in controlling source/sink constraints, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3182, 2026.
Convergent margins are gateways through which volatile species such as carbon, water, hydrogen, and sulfur are exchanged between Earth’s surface and its interior. In these subduction zone settings, carbon is fluxed from depth in two main forms: oxidized carbon as carbon dioxide and reduced carbon in the form of methane. While the former is quantitatively more important and its volcanic fluxes have been better constrained, the latter can serve as carbon and energy sources to microbiological communities and may contribute to greenhouse effects and climate stability. Constraining the geological and biological processes that govern the production, transformation, and fate of methane at convergent margins is therefore crucial for understanding the deep carbon cycle and the redox balance. Here, we present data from 47 deeply-sourced geothermal seeps spanning the Costa Rican and Panamanian convergent margins. By integrating the diversity of methane-cycling prokaryotes (5.2 % of the total community) with clumped methane isotope data (Δ13CH3D: -0.59 to 8.32), we provide an unprecedented view of the geobiological processes controlling methane cycling in these systems. Our results indicate that host rock lithology and geological setting strongly influence both the abundance and isotopic signature of the methane cycled to the surface. These findings suggest that different geological settings promote either methane production, methane oxidation, or biological overprinting. We therefore propose the geological setting as the principal control on how secondary geological and biological processes modify deep-sourced methane signals and ultimately affect the fate of methane within convergent margins.
How to cite: Selci, M., Cascone, M., Rogers, T. J., Tyne, R. L., Brovarone, A. V., Ramirez, C., Beaudry, P., Ono, S., Jessen, G., Schrenk, M. O., De Moor, J. M., Barry, P. H., Cordone, A., Lloyd, K. G., and Giovannelli, D.: Origin and fate of methane in the Central American convergent margin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20250, 2026.
The role of microorganisms in shaping Earth’s dynamics is becoming increasingly evident; therefore, understanding how they influence and control environmental processes is essential for deciphering the functioning of Earth’s systems and for the effective management of natural resources.
Hydrothermal systems offer natural laboratories for investigating the interplay between geological and microbial processes and in this context, Levante Bay on Vulcano Island (Aeolian Archipelago, Italy) represents an ideal setting to explore how these two components interact. This area is a typical hydrothermal system characterized by several CO2-dominated fluid manifestations of varying intensity and temperature. These manifestations exhibit a pronounced H2, CH4 and fluid temperature gradient along a south–north direction, as consistently confirmed by long-term geochemical observations. A distinctive feature of this site is the unusually heavy δ13C values of CH4 (up to -4.8‰ vs. V-PDB), which have led to the hypothesis of an abiotic origin for CH4.
In particular, the geochemical observations indicate that elevated fluid temperatures co-occur with higher H2 concentrations, whereas decreasing temperatures are accompanied by a marked increase in CH4 concentrations. This evidence is consistent with cytofluorimetric detection of F420+ autofluorescent cells, providing direct evidence for methanogenic archaea inhabiting the cooler points of the Bay. Our overarching hypothesis is that the observed CH4 gradient is linked not only to geological dynamics but also to microbial activity, particularly methanogenic metabolism.
To test this, we designed a microbial incubation experiment to assess whether, and to what extent, the microbial communities inhabiting five distinct points of the aquifer can influence gas and fluid chemistry, with a particular focus on elucidating their contribution to CH4 production. In particular we set three treatments for each hydrothermal fluid sample: (i) BIO_H2, unfiltered fluid incubated under an H2:CO2 (80:20) atmosphere to stimulate hydrogenotrophic methanogenesis; (ii) AB_H2, filtered fluid under H2:CO2 (80:20) conditions serving as abiotic controls; and (iii) BIO_N2, unfiltered fluid incubated under N2:CO2 (80:20) to maintain microbial communities while preventing H2-driven methanogenesis. During the incubation period, we monitored both hydrothermal fluid and headspace gas composition, with particular focus on H2 consumption, CH4 production and stable carbon isotope composition of CH4 (δ13C-CH4). Microbiological characterization was conducted through 16S rRNA gene sequencing and shotgun metagenomics to detect shifts in taxonomic composition and functional potential, with a particular focus on metabolic pathways underpinning methanogenesis and other hydrogenotrophic processes.
Preliminary results reveal that BIO_H2 incubations showed increasing alkalinity, pH, and H2S and CH4 production compared to the other treatments. Surprisingly, the AB_H2 condition also produced measurable CH4, occasionally approaching biotic levels, pointing to the need to elucidate this phenomenon. δ13CH4 signatures displayed strong site-specific variability, with high negative values under BIO_H2 treatment and comparatively less negative signatures under BIO_N2 conditions, indicating different CH4 sources or pathways. Overall, these results highlight the complexity of CH4 origin in Levante Bay and indicate that geological and biological controls on methane cycling remain insufficiently resolved.
How to cite: Iacuzzo, F., Cascone, M., Migliaccio, F., Di Iorio, L., Biagi, R., Randazzo, A., Amalfitano, S., Giovannelli, D., and Tassi, F.: Isotope of Methane and Combined Metagenomic Elucidates Microbial Overprint to Methane Emissions from the Shallow-Water Hydrothermal System of Vulcano Island (Aeolian Archipelago, Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7088, 2026.
Pyrite is the most widespread sulfide mineral in hydrothermal and geothermal systems. Its geochemistry records changes in fluid and precipitation conditions and therefore provides a valuable tool for investigating hydrothermal processes. Sulfide mineralization and sulfide trace element compositions are controlled by fluid composition, temperature, pressure, pH and redox state. Thus, pyrite compositions can provide constraints on fluid origin and geochemical trends in pyrite help identify geothermal processes such as boiling, mixing, and cooling. However, different processes can produce similar geochemical trends and may overprint one another, making it difficult to attribute specific trends to individual processes. Here, we combine geochemical numerical modelling with natural trace metal datasets of pyrite from hydrothermal systems along the Iceland rift to decipher hydrothermal processes leading to metal enrichment in pyrite.
Pyrite from boreholes, from seawater-fed and meteoric water-fed high-temperature geothermal systems located along the active Iceland rift, was sampled at regular depth intervals. Trace metal concentrations and δ³⁴S compositions were measured. The δ³⁴S values (+3.4 to +19.7 ‰) of pyrite from seawater-fed geothermal systems were systematically elevated compared to δ³⁴S values of pyrite from meteoric water fed systems (-13.1 to +2.4 ‰). Concentrations of Ni, Co, Te, Se, Ge, and Bi, along with Te/As, Co/Mo, and Se/Tl ratios in pyrite decreased with decreasing depth and temperature. Thallium, Sn, Mo, and In concentrations, along with Sb/Pb, Se/Te, and Tl/Pb ratios, increased toward the surface and cooler conditions.
Geochemical numerical modelling was used to evaluate trace metal behavior during pyrite formation under different hydrothermal processes, including progressive alteration, boiling, fluid mixing, and cooling. To achieve this, the thermodynamic databases implemented in PHREEQC were substantially expanded to include internally consistent thermodynamic data for a wide range of trace metal fluid species as well as numerous sulfide endmembers. The integration of modeling results with the observed trace metal systematics indicates that pyrite formation along the Iceland rift is dominantly associated with boiling of ascending hydrothermal fluids. Furthermore, the modelling suggests that direct magmatic contributions to either sulfur sources or trace metal budgets in pyrite are negligible, with host rock leaching and seawater (in coastal systems) representing the dominant sources of sulfur and metals.
How to cite: Müller, N. K., Kleine-Marshall, B. I., Whitehouse, M. J., Jeon, H., Marshall, E. W., Patten, C. G. C., Mortensen, A. K., and Stefánsson, A.: Linking Hydrothermal Processes to Trace Metal Variations in Pyrite from Geothermal Systems in Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9396, 2026.
The hydrothermal system serves as a critical conduit for heat transfer, typically evolving from low-temperature diffuse venting to high-temperature focused venting, or vice versa, which governs the enrichment of trace metals and their spatial distribution in pyrite. At the Xunmei hydrothermal field (26°S) on the South Mid-Atlantic Ridge, hosted in N-MORB, morphologically different pyrites provide a continuous record of the complete hydrothermal fluid evolution. This study utilized these varied pyrites to reveal the evolution of ore-forming fluids and the (re)distribution of metals driven by multi-stage episodic hydrothermal activities. Petrographic analysis identifies two mineralization stages, i.e., chimney growth dominated by high-temperature focused venting, and subsequent sulfide mound formation overprinted by late-stage diffuse venting fluids. Coupled in-situ analyses of trace elements and sulfur isotopic compositions of morphologically distinct pyrites indicate that chimney formation involved seawater mixing, magmatic degassing, and ascent of chlorine-rich magmatic fluid, with the magmatic fluid being the predominant ore-forming fluid. Thermodynamic conditions gradually stabilized, and the overgrowth of sulfides by amorphous silica suggests subsequent system cooling. Melt inclusions within plagioclase phenocrysts confirm magmatic degassing, while metallic minerals on inclusion bubble walls and residual metallic minerals in the melt phase demonstrate that ore-forming metals preferentially partition into the gas phase during magmatic immiscibility. Sulfide mound development resulted from chimney collapse, internal fluid recirculation, seawater infiltration, and overprinting by diffuse fluids. Metal enrichment in pyrites correlates with specific mineralization processes. Seawater mixing enriches Tl, V, and Mo. Magmatic degassing is associated with anomalous enrichment of Te, Au, and Cu. High-temperature magmatic influx elevates Se and Co concentrations, further enhanced by internal fluid circulation. Seawater-sulfide interaction induces a galvanic effect, leading to the removal of Zn, Ga, and Cd from the hydrothermal system. This study systematically elucidates the metallogenic mechanisms driven by multi-stage episodic fluid evolution at the Xunmei hydrothermal field, confirms the direct contribution of magmatic fluids to mineralization, and provides theoretical support for prospecting and resource evaluation of hydrothermal systems on slow-spreading mid-ocean ridges.
How to cite: Fan, L., Holzheid, A., Li, C., Zoheir, B., Wang, G., Frische, M., and Shi, X.: Pyrite Records of Episodic Venting and Metal Enrichment at the Xunmei Hydrothermal Field, South Mid-Atlantic Ridge , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9057, 2026.
Although pyrite (FeS₂) is highly reactive in oxygen-rich environments and is expected to be largely consumed through the weathering zone, observations from Taiwan indicate that pyrite grains can survive and be transported by fluvial systems. This rapidly uplifting island exhibits exceptionally high erosion rates driven by frequent earthquakes, typhoons, and pervasive landsliding.In this study, we examine the distribution and preservation of detrital pyrite in river sediments from southeastern Taiwan. Using petrographic, heavy-mineral, Raman spectroscopy and SEM-EDS data, we assessed pyrite abundance, grain morphology, and oxidation state across catchments spanning a range of erosion regimes. The results reveal that pyrite abundance and persistence scale with erosion rates: catchments eroding faster than 1 mm/yr export up to ~30% of the exhumed pyrite, accounting for more than 1% of the total sediment load, primarily as fresh fragments, whereas lower-relief catchments are dominated by oxidized pyrite grains. Fresh pyrite is particularly abundant in sands sourced from the Central Range, where erosion rates are highest and landsliding triggered by typhoons is widespread. These observations indicate that rapid erosion, rather than mineralogical resistance or external geochemical controls, is the primary factor governing pyrite survival in Taiwan’s river systems. Detrital pyrite can therefore bypass oxidative weathering in fast-eroding orogenic settings, with important implications for sulfur and carbon cycling and for the preservation of pyrite in the sedimentary record.
How to cite: Cruz Muñoz, E., Andò, S., Garzanti, E., Bufe, A., Gosetti, F., Ballabio, D., Resentini, A., and Hovius, N.: Persistence of pyrite in mountain river sediments sourced by landsliding in southeastern Taiwan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7497, 2026.
Chemical weathering plays a key role in regulating long-term atmospheric CO₂, yet the balance between CO₂-consuming and CO₂-releasing weathering pathways in Arctic catchments remains poorly constrained. Here, we present the first high-resolution, multi-decadal (1997–2022) assessment of net carbon fluxes from a heavily monitored small High Arctic river catchment in NE Greenland. Net CO₂ release is dominated by sulfuric acid weathering of carbonates driven by sulfide oxidation from pyrite minerals, as supported by δ34SSO4, δ18OSO4, and δ18OH2O isotopic tracers that together trace sulfide from other sulfur sources in river waters. River pH has increased by >1.5 units over the last 20+ years, consistent with progressive acid neutralisation by carbonate dissolution and coincident with progressive deepening of the active layer.
Our results reveal intensifying sulfuric acid-carbonate weathering in response to Arctic warming and a strengthening hydrological cycle, highlighting the sensitivity of Arctic carbon fluxes to deepening of active layers, evolving flowpaths, enhanced water-rock interactions, and geomorphic disturbance. Further, we show that extreme erosional events exert contrasting controls on catchment-scale carbon fluxes: glacial lake outburst floods reduce or temporarily reverse net CO₂ release. Erosion therefore does not exert a unidirectional control on weathering-driven carbon fluxes in Arctic systems.
These findings challenge the assumption that enhanced Arctic weathering will necessarily promote long-term CO₂ sequestration and underscore the need to account for lithology-specific and process-driven controls when assessing cryosphere–carbon feedbacks under future climate change.
How to cite: Stevenson, E., Murphy, M. J., Turchyn, A. V., Pogge von Strandmann, P. A. E., and Tipper, E. T.: Extreme hydrological events amplify weathering-derived inorganic carbon fluxes in the Arctic permafrost active layer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22517, 2026.
Pyrite oxidizes aerobically or anaerobically to generate dissolved sulfate (SO42-) and acidity (H+ ions) in rivers – the latter drives the chemical weathering of carbonate rocks. The isotopic composition of sulfate (δ34SSO4 and δ18OSO4) has been utilized to resolve the sources of riverine dissolved SO42- – pyrite oxidation and evaporite weathering. Furthermore, the triple oxygen isotopic composition (Δ’17O) of marine sulfate deposits is used as a proxy for reconstructing past atmospheric conditions (pO2/pCO2) and gross primary productivity—an approach that requires that terrestrial pyrite oxidation consumes atmospheric O2 without subsequent secondary modification. However, sulfate isotopes may not be conservative tracers of pyrite oxidation if microbial sulfate reduction (MSR) in anoxic environments, such as those in soils and aquifers, overprints the pyrite-derived sulfate isotopic composition. Hence, to derive fresh insights into pyrite oxidation and MSR in terrestrial environments, we analyze the δ34SSO4, δ18OSO4, δ18OH2O, major ions, and microbial marker gene abundances of dissimilatory sulfite reductase subunit B (dsrB) and the 16S rRNA gene in a suite of river samples across an elevational and erosional gradient in the headwaters of the Ganga in the Himalayas. We find that dissolved SO42- primarily derived from pyrite oxidation is extensively modified by MSR, which is maximized in low-erosion catchments with moderate mean annual precipitation (MAP) – a combination of factors that promotes longer fluid residence times in aquifers and in the vadose zone. By extending our framework to a global compilation of concomitant δ34SSO4, δ18OSO4, δ18OH2O, and major ions measurements, we find that MSR is as important as lithological variability in setting the isotopic composition of terrestrially derived SO42-. As such, we argue for explicit constraints on terrestrial MSR when inferring relative contributions of pyrite and evaporite weathering to riverine SO42- and when utilizing Δ’17O in marine sulfates to infer past atmospheric conditions.
How to cite: Pradhan, S., Somlyay, A., Haghipour, N., Bakker, L., Magnabosco, C., Sen, I. S., Bernasconi, S., and Hemingway, J. D.: Sulfate-isotope and marker-gene evidence for microbial overprinting of pyrite oxidation in terrestrial environments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-677, https://doi.org/10.5194/egusphere-egu26-677, 2026.
Posters on site: Thu, 7 May, 10:45–12:30 | Hall X4
Natural hydrogen (H2) produced by deep mantle and/or crustal processes has emerged as a promising source of carbon-free energy. Most current exploration methods rely on soil-gas sampling at one meter depth, where soil biological activity largely interact with H2 through both biological production and, predominantly, biological consumption. Assessing the magnitude of microbial consumption and its drivers is therefore crucial in the context of natural hydrogen exploration. In this study we developed a novel microcosm assay to discriminate the potential kinetics of aerobic H2 consumption, anaerobic H2 consumption and anaerobic H2 production in soils. In parallel, we characterized soil physical, chemical, and biological properties (granulometry, pH, redox state, soil respiration, and enzymatic activities) to identify the factors controlling biological H2 consumption and production. Experiments were conducted on soil sampled at 1 m depth in three sites exhibiting high soil H2 concentrations near the North Pyrenean Fault Thrust in the southwest of France. We found that net H2 production was consistently negligible confirming that biological H2 and accumulation in soil is unlikely under most conditions. However, we found that H2 consumption can reached up to 0.3 mmol g-1 d-1, indicating that microbial activity has the potential to deplete accumulated H2 soil within seconds under optimal lab conditions. Three main metabolic pathways were identified for H2 consumption: aerobic H2 oxidation, anaerobic acetogenesis and denitrification. H2 consumption rates were correlated with soil H2 concentration within a site, suggesting that H2 consumption directly influences our soil gas measurements. Our results demonstrate that biological consumption may be one of the major drivers of near-surface H2 concentration and call for additional data to constrain true consumption kinetics across depths and sites.
How to cite: Hoareau, G., Manon, R., Ranchou-Peyruse, A., Guignard, M., C. Gaucher, E., Portier, E., and Rigollet, C.: Microbial masking of deep hydrogen signals in soil-gas measurements , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21676, 2026.
In central Italy, the Apennine fold-and-thrust belt constitutes the boundary between the peri-Tyrrhenian extensional area and the Adriatic compressional-foredeep domain. The different tectonic settings of the two sides of the Apennine promote different geochemical features of the circulating fluids. While the western side is affected by thermal anomalies, geothermal areas and CO2 degassing sites, in the easternmost side, the presence of foredeep basins promote the presence of hydrocarbon reservoirs, mud volcanoes, and highly salty mineral waters. An extensive database of chemical-isotopic compositions of groundwater across the central Apennine has been recently compiled in the framework of the EMOTION INGV project which was devoted to the geochemical characterisation of geothermal manifestations in central-northern Italy. About 1000 groundwater analyses were retrieved from the available scientific literature and other data sources. Starting from these data, basing on thermal anomalies and other relevant geochemical-isotopic indicators, ~40 thermal/mineral springs and wells were selected and sampled for a wide-spectrum geochemical analyses including major ions, trace elements, dissolved gases and stable isotopes (H2O, C and He). The thermo-mineral waters of the western sector are generally slightly saline (TDS 1-9 g/L), with temperatures from 15 to 30°C, compositions spanning from Ca(Mg)-HCO3-SO4 to Na-Cl and affected by the input of deeply derived CO2. In addition to thermal waters, a slight temperature anomaly of large flow rate springs reveals geothermal heating of the waters corresponding to relevant heat flux. Moving from the “axial” to the easternmost sector, mineral waters show chemical compositions from Ca-SO4 to Na-Cl, the latter of which reaches very high salinities (TDS up to 183 g/L) and Br- and I- relevant contents. In these sectors, mineral waters don’t show significant thermal anomalies and show low to null input of deeply derived CO2, while showing a relative enrichment in dissolved CH4. The only exceptions are Triponzo and Acquasanta Terme systems with temperature of ~30 °C and higher CO2 contents. In this regional trends, local peculiarities are under further investigation. The produced dataset is also valuable for investigating natural resources. For instance, Li occurs at highly variable concentrations (0.01–3 mg/L) but remains of negligible economic significance, with no appreciable differences between the western and eastern sectors. In contrast, other elements of potential interest, such as B, Br, Sr, and Mn, are enriched in the high-salinity waters of the eastern sector, locally attaining potentially useful concentrations.
How to cite: Cardellini, C., Tieri, M., Taussi, M., Cinti, D., Chemeri, L., Procesi, M., Frondini, F., Chiodini, G., Caliro, S., Biagi, R., Zorzi, F., Brusca, L., and Longo, M.: West-East transect of fluids geochemistry across the Umbria-Marche Apennine (Italy): from thermal waters to highly saline fluids, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14099, 2026.
The sedimentary succession of the Laghi Gemelli Group (? Late Carboniferous-Early Permian) outcrops in the northern-central Southern Alpine domain (North Italy, Lombardy) and is composed of volcaniclastic, siliciclastic and subordinate carbonate sediments. The succession was deposited within a fault-bounded basin (Orobic Basin) formed under extensional-transtensional tectonics in the post-Variscan scenario. The stratigraphic succession that build up the Laghi Gemelli Group non-conformably overlies the Variscan Metamorphic Basement and consists of three lithostratigraphic units recording different basin filling phases: 1) alluvial systems dismantling metamorphic uplands (Conglomerato Basale), 2) caldera-centered acidic volcanic systems (Cabianca Volcanite Fm.), and 3) endorheic alluvial systems dismantling metamorphic and volcanic uplands (Pizzo del Diavolo Fm.). A prominent angular unconformity marks the top of the Laghi Gemelli Group, at whose top sits the? Middle-Late Permian Verrucano Lombardo alluvial system.
Excellent outcrop exposures in central Bergamasque Alps (Valgoglio, BG) have progressively fostered a substantial advancement in the understanding of the Lower Permian stratigraphy. However, their geochemical composition and variability – major and trace elements – have largely remained unexplored. Sediment chemistry can contribute to the identification of distinctive geochemical markers that can be employed for basin-scale correlations, a valuable approach in settings characterized by units with pronounced thickness and facies variations.
For the first time, 73 rock samples collected in the central sector of the Orobic Basin from outcrops of the Laghi Gemelli Group and lowermost Verrucano Lombardo have been analyzed at the University of Milan by using the LA-ICP-MS technique. Prior to the analysis, Pressed Powder Pellets (PPPs) were prepared. Although the data analysis didn’t reveal clear significant geochemical trends in both major and trace elements, several local changes are noteworthy. Where preserved below the unconformity with the Verrucano Lombardo, the upper part of the Pizzo del Diavolo Formation, displays an averagely low Na content and substantial increases in K, Li and Cs. No significant geochemical trend or variation has been detected across the unconformity into Verrucano Lombardo sediments. Future investigations may assess whether similar chemofacies occurs in other sectors of the Orobic Basin at a comparable stratigraphic position. Geochemical analysis has also revealed localized anomalies involving a narrow spectrum of elements. Four main patterns were identified: a) high U, Pb, Sb and Cu in altered tuffstones from the top of the Cabianca Volcanite; b) high Zn, Pb and Cd in lacustrine sediments of the lower Pizzo del Diavolo Formation; c) high B in volcaniclastics and mud-heterolithic deposits (Cabianca Volcanite and Pizzo del Diavolo Formation); d) As enrichment accompanied by increased Mo, In and Sb in mudstone facies of the lower Pizzo del Diavolo Formation.
Starting from these new geochemical analyses, future works can peer into the processes that led to such an anomalous concentration in volcano-sedimentary deposits that, except for uranium, have been poorly investigated in the past. Furthermore, broader sampling will reveal how and why some of these anomalies spread into the basin.
How to cite: Reguzzi, S., Chesi, C., Re, S., Moschetti, L., and Tiepolo, M.: Unveiling the Geochemical Signature of the Early Permian Orobic Basin (Laghi Gemelli Group; N Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2957, 2026.
The aviation industry is facing increasing pressure to reduce greenhouse gas emissions, accelerating the development of sustainable aviation fuel (SAF) as an alternative to fossil-based jet fuels. Conventional aviation fuels rely on finite fossil resources and are associated with long-term resource depletion and environmental burdens, whereas SAF has attracted growing attention as a viable option for mitigating emissions from a carbon-cycle perspective. Securing sustainable and reliable feedstocks therefore remains a key challenge for large-scale SAF deployment.
Microbial oils have emerged as promising SAF feedstocks due to their high productivity, ability to utilize diverse substrates, and potential for scalable cultivation. In this context, the exploration of novel feedstocks based on microbial biodiversity is gaining increasing importance, particularly for diversifying resource bases and improving feedstock resilience.
In this study, we screened and comparatively evaluated the oil production potential of microbial strains derived from Korean biological resources. A diverse set of microorganisms isolated from various natural environments in Korea was examined, including filamentous fungi (Mortierella sp., Umbelopsis sp., and Mucor sp.) and oleaginous yeasts (Yarrowia lipolytica and Rhodotorula sp.). All strains were cultivated under identical conditions, and their growth characteristics and intracellular lipid accumulation were systematically assessed. Several native strains exhibiting high microbial oil production capacity were successfully identified, underscoring the potential of Korean microbial biodiversity as a sustainable resource for energy applications.
Taken together, these results highlight microbial oils derived from indigenous microbial resources as viable alternative feedstocks for SAF production, with the potential to reduce dependence on fossil fuels and associated greenhouse gas emissions in the aviation sector. Beyond energy applications, the microbial oil production strategies presented here may also be extended to future uses in food and feed systems, providing foundational insights for sustainable energy transitions and the development of a circular bioeconomy.
Following are results of a study on the "Convergence and Open Sharing System "Project, supported by the Ministry of Education and National Research Foundation of Korea
How to cite: Park, S., Lee, D., Kim, Y., and Lee*, S.-M.: Lipid Profiling of Indigenous Korean Microbial Biodiversity for the Discovery of High-Potential Strains for Sustainable Aviation Fuel(SAF) Production, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15732, 2026.
Enrichment of coalbed methane is fundamentally governed by the formation and distribution of coal seams. In continental fault-depression basins, the mechanisms controlling peat accumulation are more complex than those in stable basins, extending beyond traditional sea-level control models. This study examines the synergistic control of provenance, climate, tectonics, and sedimentation on coal accumulation in such settings, focusing on Member 2 of the Lower Cretaceous Nantun Formation (K₁n²) in the Huhehu Depression, Hailar Basin—a typical continental fault-depression basin and its major source rock interval.By integrating multiple analytical techniques, including organic geochemistry (e.g., biomarkers, carbon isotopes), elemental geochemistry (major, trace, and rare earth elements), petrographic analysis, and seismic-log based sedimentary facies interpretation, this research systematically reconstructs the paleoenvironment during peat accumulation, delineates the spatial distribution of coal seams in detail, and quantitatively to semi-quantitatively evaluates the contributions of various controlling factors.
Key findings are as follows:
(1) Paleoenvironmental Reconstruction and Provenance Characteristics: Comprehensive geochemical indicators reveal that during the peat-forming period of K₁n², the study area experienced warm and humid paleoclimatic conditions with a freshwater environment. The provenance was dominated by intermediate-acidic igneous rocks, exhibiting a weakly neutral to acidic geochemical signature. This combination effectively suppressed large-scale terrigenous clastic input, providing a critical geochemical foundation for the development of low-ash, high-organic-content coal.
(2) Sedimentary-Tectonic Synergistic Control Mechanism and 3D Distribution Patterns: This study clearly identifies the littoral-shallow lacustrine facies as the only dominant peat-accumulating facies within this fault-depression lacustrine setting. Its spatial distribution is strictly constrained by the basin’s "eastern faulting, western overlapping" half-graben structural framework. Coal seams mainly developed in the transitional zone from the eastern steep slope belt to the central depression (sag), where the rate of accommodation space creation remained in long-term balance with the rate of peat accumulation. Seismic attribute analysis and isopach mapping clearly demonstrate an asymmetric distribution of cumulative coal seam thickness—thicker in the east and thinner in the west—trending along the fault zone and thickening significantly toward the east (downthrown block), with thicknesses ranging from 30.84 to 151.24 meters. This distribution forms the material basis for coalbed methane enrichment.
Based on these findings, this study innovatively establishes a comprehensive sedimentary model applicable to continental fault-depression basins: "Weakly Neutral-Acidic Provenance Supply – Warm-Humid Freshwater Environment – Littoral-Shallow Lacustrine Facies Dominance – Peat Accumulation in Steep Slope Belt to Depression Zone." This model systematically elucidates the dynamic coupling among provenance characteristics, paleoclimate, syn-sedimentary tectonic activity, and lake-level fluctuations. It represents an important supplement to and advancement of the classical sea-level-controlled coal accumulation paradigm, forming a novel theoretical framework for peat accumulation in continental fault-depression basins.This research deepens the understanding of the intrinsic mechanisms controlling coal measure formation in fault-depression basins.
How to cite: Tang, Y. and Wang, M.: Mechanism of Coal Accumulation in Fault-Depressed Basins and Exploration Insights: A Case Study of Member 2 of the Nantun Formation in the Huhehu Depression, Hailar Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8625, 2026.
In many water catchment areas, degredation processes in aquifers used for water management ensure a reduction in nitrate pollution. The reaction capacity of aquifers is mainly linked to organic carbon compounds and pyrite. The latter is particularly favoured for denitrification. However, pyrite is a finite resource that is depleted by continuous nitrate inputs. In principle, this leads to the advance of reaction fronts in the aquifer and potentially also to increasing concentrations in the managed groundwater. Model calculations are used to illustrate various dispersion mechanisms and the decisive role of pyrite in regard to the amount of nitrate in the groundwater.
How to cite: Hansen, C. and Kühn, M.: Reduced nitrate degradation in groundwater and its consequences – model-based assessment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22735, 2026.
Pyrite is ubiquitous in the Earth’s crust, redox-sensitive and prone to oxidation. This applies as well to clay rock formations targeted for the final disposal of radioactive waste. Those rocks are tested in experiments in regard to their suitability for the long-term containment of radionuclides (RN). In the laboratory, samples are often handled under atmospheric conditions, whereas the subsurface provides mainly reducing environments. This means that pyrite can potentially oxidise during experimental procedures, which in turn influences the conditions for the migration of redox-sensitive RN. Different modelling approaches exist to account for pyrite oxidation in geochemical simulations of experiments. The most simple form is the assumption of thermodynamic equilibrium. The application of kinetic rate laws is more complex and computationally intensive.
The electrochemical reaction of pyrite oxidation can be separated into the anodic and cathodic reaction part. They are linked to each other through electron transfer taking place at the interface between mineral surface and pore water. The reductant within the anodic reaction is pyrite itself. Oxidants for the cathodic reaction could be oxygen or ferrous iron. In addition, the direct reaction of other reactants with pyrite, such as oxidised RN, is in some cases thermodynamically feasible for experimental conditions with no or low iron and minor oxygen concentrations in the pore water.
Reactive transport simulations of RN migration in clay rock are compared against experimental data sets. RN occur in different oxidation states, if redox-sensitive. Their mobility and subsequent migration length is governed by the ratio between the most stable oxidised and reduced states under environmental conditions. This is controlled by the inherent redox conditions in the core samples as well as imposed by the introduced pore water chemistry. We test three approaches to model the underlying redox reactions coupled to diffusion and sorption. Firstly, pyrite oxidation in thermodynamic equilibrium. Secondly, different well known kinetic reaction rates for pyrite oxidation. Thirdly, reduction of RN triggered via an iron source associated with the clay minerals. Hence, pyrite oxidation is modelled thermodynamically, kinetically and not at all.
How to cite: Kühn, M. and Hennig, T.: Pyrite oxidation impacts radionuclide migration in clay rock - thermodynamically, kinetically or not at all?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19401, 2026.
Pyrite oxidation in internal lignite mine dumps is the primary source of acidity, sulfate, and iron in flooded open-pit lignite mines. While the associated geochemical reactions have been extensively studied through modeling, field observations, and laboratory experiments, uncertainties remain due to site-specific factors such as the heterogeneous distribution of sediments and pyrite within the dumps. In particular, these heterogeneities complicate predictions of the temporal contaminant release into surrounding aquifers.
This study investigates the development of reaction fronts in an internal mine dump, focusing on how sediment and pyrite distribution, defined by correlation lengths and mineral content, affects reactive transport processes. Geostatistical methods are combined with geochemical modelling to conduct 2D reactive transport simulations that incorporate pyrite oxidation kinetics.
Results show that heterogeneous scenarios reduce tracer breakthrough time by up to 15 % compared to a homogeneous setup. The total tracer outflux varies between 89 % and 139 % of that observed in the homogeneous reference case. Reaction fronts in heterogeneous configurations cover a larger area and extend deeper into the modelling domain than those in the homogeneous scenario. Simulations that exclude reaction kinetics require more computational time, but result in smoother reaction front edges and more detailed redox gradients compared to equilibrium-based approaches.
The findings indicate that preferential flow paths, that arise from structural heterogeneity, can accelerate flow-through times and enhance solute outflux quantities. The effect scales with oxygen availability for pyrite oxidation. However, while higher oxygen concentrations increase peak and average solute concentrations in the dump, the spatial and temporal patterns of outflux are primarily governed by heterogeneity. Accurate prediction of contaminant release from specific mine dumps remains challenging due to the difficulty of characterising internal structures in the field. However, simulating multiple plausible scenarios allows for estimating ranges of outflux timing and magnitude, supporting risk assessment and groundwater management. The impact of 3D heterogeneities on preferential flow path development in similar geochemical systems remains unexplored and should be addressed in future research.
Literature
Schnepper, T., Kühn, M. and Kempka, T. (2025a): Reaction Path Modeling of Water Pollution Implications of Pumped Hydropower Storage in Closed Open-pit Lignite Mines. Mine Water and the Environment, 44, 107-121. DOI: 10.1007/s10230-025-01039-y
Schnepper, T., Kapusta, K., Strugała-Wilczek, A., Roumpos, C., Louloudis, G., Mertiri, E., Pyrgaki, K., Darmosz, J., Orkisz, D., Najgebauer, D., Kowalczyk, D. and Kempka, T. (2025b): Potential hydrochemical impacts of pumped hydropower storage operation in two European coal regions in transition: the Szczerców-Bełchatów mining complex, Poland, and the Kardia Mine, Greece. Environmental Earth Sciences, 84, 9, 247. DOI: 10.1007/s12665-025-12198-0
Schnepper, T., Kühn, M. and Kempka, T. (2025c): Effects of Permeability and Pyrite Distribution Heterogeneity on Pyrite Oxidation in Flooded Lignite Mine Dumps. Water, 17, 21, 3157. DOI: 10.3390/w17213157
How to cite: Schnepper, T., Kühn, M., and Kempka, T.: Pyrite oxidation and its implications for flooding of heterogeneous lignite mine dumps: a reactive transport modelling study , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19159, 2026.
Pyrite is one of the most abundant sulfide minerals in the Earth’s crust and can host a wide range of transition metals. However, due to their higher electron counts and atomic sizes different from that of Fe, these substitutions often destabilize the lattice, and the mechanisms controlling their incorporation remain poorly understood. Here we use ab initio simulations to systematically investigate transition-metal substitution in pyrite, using Au-As coupling as a representative example within a broader set of transition-metal systems. We analyze defect formation energies, lattice distortions, and electronic structures for single and double substitutional configurations. Isolated substitutions are generally thermodynamically unfavorable, whereas joint substitutions are more likely to take place. In particular, anion-site dopants with fewer valence electrons than sulfur, such as arsenic, facilitate the incorporation of large-radius transition metals by promoting locally constrained coordination environments and alleviating lattice strain. Electronic structure analyses show that impurity stability is governed by band filling and Fermi-level positioning. Double substitution enables electronic compensation, eliminates mid-gap states, and lowers defect formation energies across multiple transition-metal systems. These results establish electronic compensation as a fundamental control on transition-metal enrichment in pyrite, with implications for pyrite-hosted ore deposits and trace-metal capture across the pyrite life cycle.
How to cite: Gao, Z.-Y., Qiu, K.-F., and Caracas, R.: Electronic controls on transition-metal incorporation in pyrite: insights from ab initio simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11853, 2026.
At the source of an orogenic gold deposit, Au and As are inferred to be mobilized during prograde metamorphic breakdown of diagenetic pyrite into pyrrhotite. However, the exact timing and mechanisms of Au and trace element release from diagenetic pyrite is still elusive. Here we investigate trace element chemistry (LA-ICP-MS) of sulfides (diagenetic pyrite, metamorphic pyrite and pyrrhotite) and bulk Au contents from middle greenschist to lower amphibolite facies metapelites (Neoproterozoic Mandhali Formation from NW Indian Lesser Himalayas). Our results show that more than 80% of Au and 65% of As are released from diagenetic pyrite during early metamorphic recrystallization in the middle greenschist facies. In the lower amphibolite facies, pyrite has been completely metamorphosed and has already lost 93% Au, 75% As and the bulk of Pb, Sb, Cu, Bi and most other trace elements prior to breakdown into pyrrhotite. Despite late and incomplete pyrite to pyrrhotite transition in the amphibolite facies, Au was also mobilized from the bulk rock (from 9.0 ppb to 1.1 ppb mean bulk Au) indicating: (1) even a partial pyrite to pyrrhotite transition can result in regional Au mobilization, and (2) Au mobilization occurs in a two-step process involving release from diagenetic pyrite into the rock matrix during metamorphic recrystallization followed by later mobilization in metamorphic fluids.
How to cite: Thathrampally, A. L., Chakravarti, R., Laflamme, C., Olin, P., Magnall, J., and Gleeson, S. A.: Two-step gold mobilization in metamorphic terranes: A refined metamorphic model for Orogenic Gold , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22726, 2026.
The Carlin-type gold (CTG) mineralization has been known in north-central Nevada since the early 1960s, but was until quite recently assumed to be a Nevadan phenomenon. The model to form the gold containing pyrite in these deposits requires an iron-rich carbonate host rock, which is thought to release its iron during dissolution by an acidic fluid carrying gold, arsenic, and sulfur (Muntean et al., 2011). The subsequent pyrite is thought to grows at the at the expense of the hydrogen-sulfide complex and therefore causes the precipitation of gold.
We will discuss the new model for gold incorporation into pyrite (Gopon et al., 2024), how it links to the occurrence of gold and arsenic containing pyrite from orogenic deposits in the Eastern Alps (Goebel, 2024; Hiller, 2024; Dunkel et al., 2025). These orogenic pyrites appear near identical to pyrite from CTG deposits, despite having none of the required components for gold-arsenic rich pyrite formation from the Muntean model. Do we therefore need to question this model, or are there multiple ways to generate identical pyrite microstructures/geochemistry?
Our works suggest that a more universal model for Au-As rich pyrite is needed, and one that can explain the observed trends in pyrite geochemistry and gold remobilization. In the orogenic deposits in the Alps, we see amble evidence for native gold associated with pyrite, suggesting a secondary remobilization of native gold which was previously hosted in pyrite. In these orogenic deposits, this process appears to lead to an enrichment along the mineralization, which forms the high-grade native gold containing quartz veins for which these districts are famous for.
References:
Dunkel, F. et al., 2025, Precious and critical metal potential of historic Cu-Au-As mine waste in Spielberg, Austria, in Proceesing of the Annual European Geosciences Union Meeting, Vienna.
Goebel, E., 2024, Sulfide Geochemistry of the Hohen Tauern Historic Gold Districts (Austria): Montanuniversitat Leoben.
Gopon, P., Sack, P., Pinet, N., Douglas, J.O., Jenkins, B.M., Johnson, B., Penny, E., Moody, M.P., and Robb, L., 2024, Revealing Yukon’s hidden treasure: an atomic-scale investigation of Carlin-type gold mineralization in the Nadaleen Trend, Canada: Mineralium Deposita, v. 60, p. 937–953
Hiller, J., 2024, A green future from a contentious past: Gold and critical metals in a historic arsenic mining district Straßegg (Styria) [Masters Thesis]: Montanuniversitat Leoben.
Muntean, J.L., Cline, J.S., Simon, A.C., and Longo, A.A., 2011, Magmatic–hydrothermal origin of Nevada’s Carlin-type gold deposits: Nature Geoscience, v. 4, p. 122–127
How to cite: Gopon, P., Dunkel, F., Göbel, E., and Hiller, J.: Carlin-like Pyrite in Orogenic Copper-Gold Deposits in the Eastern Alp, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9746, 2026.
Pyrite oxidation coupled with rock weathering occurs on the Barton Peninsula and is likely to be accelerated by progressive glacial melting, which exposes more bedrock to weathering. King George Island (KGI), with a surface area of 1250 km², is the largest of the South Shetland Islands (SSI) and is located about 120 km north of the Antarctic Peninsula. The study area, the Barton Peninsula, forms the southwestern part of KGI and is the second-largest ice-free area on the island, with an approximate surface area of 12 km². The Barton Peninsula is predominantly composed of volcanic and plutonic rocks; volcanic rocks make up most of the peninsula and the sampling area, with compositions ranging from basaltic andesite to andesite. In the northern part of the peninsula, strongly weathered paragneiss displays a distinct rusty coloration caused by pyrite oxidation and is enriched within many of the volcanic rocks (Balci and Gunes, 2024). A series of oxidation experiments using pyrite-bearing and non-pyrite-bearing rocks was conducted, and the results were integrated with water geochemistry as well as the mineralogical and elemental compositions of freshwater, sediments, and rocks to evaluate the influence of pyrite oxidation on surface waters of the peninsula. Acid-production potential analyses show that andesitic rocks exposed at the northern tip of the peninsula have the highest values, ranging from 51.25 to 78.1 kg H₂SO₄ per ton of rock. The pH of the experimental media remained acidic even after 240 days of andesite-water interaction. Consistently, the highest releases of Ca (average 1.2 ppm), Mg (1.34 ppm), Mn (0.056 ppm), K (0.074 ppm), and Fe (0.092 ppm) were observed from pyrite-bearing andesitic rocks, whereas the highest releases of P and N were associated with basaltic andesite. Oxidation of andesitic rocks also released elevated concentrations of Zn and Cu. In agreement with the experimental data, freshwaters with low pH (3.7–4.2), high sulfate (46–92 mg/L), and high Fe (0.8–16.5 mg/L) occur at the northern tip of the peninsula. In contrast to neutral waters, these acidic waters exhibit the highest concentrations of cations (e.g., K, Na, Si, and Ca) and anions (e.g., SO₄²⁻). This indicates that pyrite oxidation coupled with enhanced silicate weathering acts as a powerful natural fertilizer on the peninsula and is likely to increasingly regulate microbial and ecosystem productivity in the future as global warming drives progressive glacial melting.
Keywords: Maritime Antarctica, Pyrite, Nutrients, Oxidation,
References:
Balci and Gunes, 2024 Generation and geochemical characteristics of acid rock drainage (ARD) in Barton Peninsula, King George Island (KGI), maritime, Antarctica, Vol.954 Science of The Total Environment.
How to cite: Balci, N., Sonmez, E., Unal Ercan, H., and Demiraran, O.: Pyrite oxidation enhances nutrient release into freshwater on the Barton Peninsula, Maritime Antarctica, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8872, 2026.
Iron and sulfur isotope geochemistry serves as a powerful tool for probing diverse geological processes, spanning igneous, metamorphic, sedimentary, hydrothermal, and biological systems. Pyrite, a ubiquitous iron and sulfur-bearing mineral in various rock types and the predominant sulfide in hydrothermal ore deposits, is a common product throughout hydrothermal mineralization stages. The coupled Fe-S isotopic system in pyrite offers crucial constraints on fluid sources, fluid–rock interaction, and the physicochemical and redox conditions during mineral precipitation.
In contrast to conventional bulk analytical methods, in situ microanalytical techniques—notably laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) and secondary ion mass spectrometry (SIMS, mainly for S isotopes)—permit to investigate Fe and S isotopic variations and fine-scale heterogeneity at high spatial resolution, which is essential for deciphering complex, multistage hydrothermal systems. The broader application of these techniques, however, is currently limited by the lack of matrix-matched reference materials with well-characterized Fe and S isotopic compositions.
Here, we assess a natural pyrite sample (IGGPy-1) for its major-element and Fe–S isotopic homogeneity. Bulk analysis by elemental analyzer–isotope ratio mass spectrometry (EA-IRMS) yields a δ34SVCDT value of +17.09 ± 0.30‰. Solution-nebulization MC-ICP-MS (SN-MC-ICP-MS) gives δ56FeIRMM‑014 and δ57FeIRMM‑014 values of –1.31 ± 0.06‰ and –1.94 ± 0.12‰, respectively. These results position IGGPy-1 as a promising candidate reference material for in situ Fe–S isotopic microanalysis of pyrite.
How to cite: Xie, L., wang, X., Yu, H., Gao, J., Xu, L., Huang, C., Yang, Y., Wu, S., and wang, H.: A Newly Natural Pyrite Reference Material for In Situ S and Fe Isotope Microanalysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12796, 2026.
