Supporting the transition to sustainable low-carbon economies at scale poses significant challenges and opportunities for the global geoscience community. Improved integration and tighter interdisciplinary understanding of the subsurface processes that can provide access to alternative energy supplies and critical raw materials is needed, as are unifying science-backed exploration strategies and resource assessment workflows.
This session aims to improve our scientific understanding of the pathways and interdependencies that lead to the concentration of economic quantities of energy carriers or noble gases, mineral resources, and the formation of exploitable geothermal reservoirs. Further, it also focuses on providing input for exploration decision-making and scientific input for policy making as well as for the strategic planning of collaborative research initiatives.
We invite studies on observational data analysis, instrumentation, numerical modeling, laboratory experiments, and geological engineering, with an emphasis on integrated approaches/datasets which address the geological history of such systems as well as their spatial characteristics for sub-topics such as:
- Geothermal systems: key challenges in successfully exploiting geothermal energy are related to observational gaps in lithological heterogeneities and tectonic (fault) structures and sweet-spotting zones of sufficient permeability for fluid extraction.
- Geological (white/natural) hydrogen (H2) and helium (He) resources: potential of source rocks, conversion kinetics, migration and possible accumulation processes through geological time, along with detection, characterisation, and quantification of sources, fluxes, shallow subsurface interactions and surface leakage.
- Ore deposits: To meet the global continued demand for metal resources, new methods are required to discover new ore deposits and assess the spatio-temporal and geodynamic characteristics of favourable conditions to generate metallogenic deposits, transport pathways, and host sequences.
Orals: Mon, 4 May, 16:15–18:00 | Room -2.41/42
Natural hydrogen (H2) is emerging as a promising carbon-free energy source, aligning with France’s ambition for carbon neutrality and energy sovereignty by 2050. Yet, its occurrence, distribution and long-term sustainability remain largely unexplored. In this context, the H2 and helium exploration company 45-8 Energy was granted the “Grand Rieu” exploration license in the northwestern Pyrenees (SW France), to further investigate its natural H2 system prospectivity, with the objective of drilling an exploration well in the near future.
The license covers part of the Mauleon Basin (North-Pyrenean Zone), a Cretaceous hyperextended rift basin inverted during the Tertiary Pyrenean orogeny (e.g. Saspiturry et al., 2020). This region and the adjacent Pyrenean foreland (Arzacq basin) to the north benefit from extensive historical datasets acquired since the 1950s by major academic research programs (e.g. Orogen project) and the Oil & Gas industry (e.g. historical Lacq and Meillon gas fields), including deep exploration wells, 2D/3D seismic reflection surveys and gravimetric and magnetic data.
Our current work aims to integrate and interpret these datasets to characterize each element of the H2 system and perform volumetric and risking evaluations of H2 prospectivity within the Grand Rieu license. Geophysical studies (e.g. Wang et al., 2016; Wehr et al., 2018; Lehujeur et al., 2021; Saspiturry et al., 2024) highlighted gravimetric, magnetic and velocity anomalies suggesting the existence of a large mantle body at depth (8-10 km) under ideal P-T conditions for serpentinization and H2 generation. Numerous active H2 seepages measured at the surface along the North Pyrenean Frontal Thrust system (Lefeuvre et al., 2022) suggest active serpentinization at depth and preferential migration pathways along regional faults. Proven Upper Jurassic and Lower Cretaceous carbonate reservoirs with overlying effective seals are well-known northward in the Pyrenean foreland (Lacq and Meillon gas plays). However, their presence and properties in the Mauleon Basin remain historically poorly studied and therefore needed to be further characterized to improve their predictability. Ongoing seismic interpretation, aiming to identify potential traps and H2 migration pathways at regional scale, reveals a complex structural framework directly linked to Cretaceous hyperextension and following Cenozoic Pyrenean compression. Preliminary results suggest the existence of deep-seated structures suitable for H2 accumulation.
Overall, the Mauleon Basin appears to offer a unique geological setting favorable for natural H2 generation, migration and accumulation. Further characterization of these processes through dynamic numerical modelling is necessary to better constrain the natural H2 system. In addition, volumetric and risking evaluations will guide the selection of a drilling target within the Grand Rieu license, marking a critical step toward assessing the viability of natural hydrogen as a sustainable energy resource in France’s energy transition.
How to cite: Laurent, A., Boka-Mene, M., De Boisgrollier, T., Fontanelli, L., Potel, S., and Hauville, B.: Exploring natural hydrogen in the NW Pyrenees (France), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18410, https://doi.org/10.5194/egusphere-egu26-18410, 2026.
Unlike traditional hydrocarbon and mineral exploration, where decades of empirical data informed threshold values, natural hydrogen exploration requires establishing new baselines for what constitutes an economically significant anomaly. To use soil gas measurements as an effective tool in the geological hydrogen research and exploration we must understand the limitations of the existing instruments, what are background hydrogen values in soil and what other data are required for the reliable interpretation of the soil gas measurements and monitoring data sets.
Current technology constraints remain a significant challenge in natural hydrogen soil gas sensing. Field-appropriate commercially available sensors exhibit combinations of limited operating ranges, cross-sensitivity to humidity and other gases, baseline drift over time and exposure, and hysteretic dynamics. CSIRO has developed Seeptracker multi-gas (hydrogen, methane, carbon monoxide and carbon dioxide) monitoring device. In this presentation we want to share findings regarding the commercially available hydrogen sensing components comprising Seeptracker and results of deploying this instrument around the world to collect soil gas data in various geological settings. Seeptracker utilises multiple commercially available sensors to measure hydrogen and other gases and the output is enhanced by an extensive calibration routine to improve gas measurement accuracy. Developing Seeptracker revealed the challenge of balancing sensing quality, deployment compatibility, and cost/effort scaling. To achieve suitable long-term large-scale autonomous field deployment requires a clearly and concisely defined study scope, together with a well-characterised sensor package and robust calibration routine to address the multi-variate challenge.
Interpreting multi-gas measurements introduces both opportunities and risks for false positives. Effective interpretation of soil gas data for geological hydrogen research requires integration with multiple complementary datasets. Geological mapping identifying serpentinisation fronts, radiolytic source rocks, or fault systems provides essential structural context. Geophysical surveys, particularly magnetotellurics and gravity, can delineate subsurface fluid pathways and potential trap geometries. Geochemical analysis of associated gases, including methane, helium, nitrogen, carbon and noble gas isotopes, potentially enables source discrimination and migration pathway delineation.
Our work with Seeptracker deployments across diverse geological settings around the world suggests that sustained hydrogen concentrations in soil gas can be used as an effective tool for natural hydrogen exploration, but it cannot be used in isolation. The detailed follow-up investigation is required, particularly when accompanied by spatial coherence and temporal stability and crucially ensuring that measured natural hydrogen is geological. Our studies demonstrate that continuous monitoring data capturing temporal variability, rather than single-point measurements, enhances interpretation confidence. In this presentation we show the performance of the current hydrogen sensors within the CSIRO multi-gas monitoring system Seeptracker, including limitations, and present soil gas monitoring results from various sites around the world. We also show in greater detail soil gas studies from Australia, and the interpretation of the soil gas monitoring results is constrained by geochemical, geophysical and isotope data sets.
How to cite: Markov, J., Mow, V., Kasperczyk, D., Breedon, M., Moran, M., Down, D., Camilleri, M., Strand, J., and Liang, J.: Establishing meaningful soil gas measurements for geological hydrogen research and exploration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18056, https://doi.org/10.5194/egusphere-egu26-18056, 2026.
Natural hydrogen gas (H2) generated through the serpentinization of mantle rocks is a promising source of clean energy. For large-scale serpentinization and natural H2 generation to occur, the mantle rocks need to be brought into a optimal temperature range (the serpentinization window) and into contact with water. Alpine-style rift-inversion orogens, formed during the closure of rift basins, provide excellent environments for serpentinization-related natural H2 generation, while also harbouring extensive volumes of sediments in which natural H2 accumulation could form. In such orogens, erosion is known to have an important impact on exhumation processes and sediment distribution, but to what degree erosion efficiency influences natural H2 resource potential remains poorly understood. We use numerical geodynamic models of rift-inversion to explore and, importantly, quantify the relative roles of erosion and tectonic processes by applying different erosion efficiencies and initial rift phase durations.
Our modelling shows that, regardless of erosion efficiency, initial rift duration is a dominant factor during both the extension and inversion phase. Prolonged rifting causes increased mantle exhumation and thus higher natural H2 generation potential. Erosion efficiency exerts only a secondary effect, in that more efficient erosion modestly reduces H2 generation potential by narrowing the serpentinization window. Inversion of advanced rift basins results in asymmetric orogens in which mantle material is incorporated into the overriding wedge, a configuration that is critical for generating high natural H2 generation potential in these systems. Nevertheless, efficient erosion of otherwise symmetric orogens formed after limited rifting allows for a shift to an asymmetric style, with significant mantle exhumation and natural H2 generation potential.
However, efficient erosion and associated fast exhumation of relatively hot material in orogens can also decrease the vertical extent of the serpentinization window, reducing natural H2 generation potential. Moreover, rapid erosion can remove the otherwise abundant potential reservoir rocks and seals needed for exploitable natural H2 accumulations to form. Still, these negative effects of erosion on “conventional” natural H2 resources (involving H2 accumulation in reservoir rocks), may be favourable for “unconventional” natural H2 resources. Systems with relatively hot mantle material close to the surface may in fact be suitable for stimulated natural H2 exploitation efforts, involving direct drilling of the mantle source rock itself.
Thus, although erosion efficiency is not the dominant factor, it can still have a considerable impact on natural H2 potential in rift-inversion orogens. Therefore, a thorough understanding of the evolution of those orogens targeted for exploration, will be of great importance. This challenge can be aided by numerical geodynamic models such as those presented here, with which we perform a first-order analysis of natural examples from the Pyrenees, Alps, and Betics.
How to cite: Zwaan, F., Glerum, A. C., Brune, S., Vasey, D. A., Naliboff, J. B., Manatschal, G., and Gaucher, E. C.: The impact of erosion processes on natural H2 resource potential in Alpine-style orogens, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8255, https://doi.org/10.5194/egusphere-egu26-8255, 2026.
The Engadine valley, located in the Grischun area in SE Switzerland, presents multiple mineralized springs distributed along the Engadine fault. Hydrogen (H2) concentration measured along the Engadine fault can reach up to 1900 ppm, indicating the presence of both, a deep groundwater flow system and a deep-seated 'kitchen'. These observations suggest that the Engadine fault may control the regional hydrodynamics and likely also the hydrogen production along the Engadine valley. A key factor to identify and understand the location of the H2 kitchen, fluid pathways and related water in- and H2 out-flow is the understanding of the nappe stack in the Grischun area and its relation to the Engadine fault. The latter, represents a major SW-NE striking >100km long structure that resulted from post-collisional oblique strike-slip movements during Oligocene-Miocene time. It transects the Late Cretaceous Austroalpine nappe stack, floored by the Pennine, ultramafic rocks bearing ophiolites, inherited from the closure of the Alpine Tethys proto-oceanic domain. Thus, a key question is whether there is a hydrodynamic link between the ultramafic source rocks flooring the rift-inversion nappe stack, the Engadine fault, acting as a possible conduit for deep water circulation, and the occurrence of springs and H2 anomalies in the soil gas. To answer to this question, we constructed a numerical hydrodynamic model of the Engadine and surrounding area, including the Engadine fault. This model allows us to carry out regional-scale simulations to investigate the interplay between topography and a deep, permeable conduit (e.g. Engadine fault) and its control on hydrothermal circulation. The model couples groundwater flow, heat transport and solute transport, and will be calibrated with surface observations (location of springs and chemical anomalies in water and soil gas). First results suggest that fluid upwelling occurs SW of St.Moritz and NE of Scuol along the Engadine valley, whereas the fault-segment between St.Moritz and Scuol corresponds to a region of meteoric recharge. This SW-NE distribution of deep upwelling correlates well with first geochemical field measurements. Future work will include chemical fluid-rock interaction to fully understand the hydro-chemical conditions of H2 formation and H2 pathways to the surface along the Engadine valley. Ultimately, this well-constrained, regional scale model, will serve as an exploration tool, allowing us to quantitatively evaluate the potential for energy-related exploitation (H2 and/or geothermal).
How to cite: Gasser, Q., Manatschal, G., Alt-Epping, P., Gaucher, E. C., Pierre, S., Dimasi, F., and Ulrich, M.: The link between deep groundwater flow and serpentinization-sourced H2 production in rift inversion orogens: the example of the Engadine valley (SE Switzerland), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10381, https://doi.org/10.5194/egusphere-egu26-10381, 2026.
Ophiolitic succession of the Eastern Mediterranean region includes one of the most famous natural H2 leakage spot, globally known as “Chimera Gas Seepage”, noted since ancient times. Geochemical analysis on the seepage revealed that the origin of the gas is abiotic and along CH4, %10-12 of H2 is associated with the seepage due to the serpentinisation process which is widely accepted as one of the main mechanisms for the natural H2 generation.
Radiolysis, considered as another natural H2 generation process, is defined as the decomposition of H2O by decay of 232Th-238U-40K causing an increase in radioactivity levels. Therefore, increasing radioactivity levels can be detected to identify potential natural H2 generating zones by calculating the radiogenic heat generation. This study aims to test this hypothesis by implementing the usually neglected or overlooked 232Th-238U-40K concentration measurements, also known as SGR logs. A-1 well drilled in the onshore portion of the Antalya Bay, SW Turkey, includes 232Th-238U-40K concentration measurements covering an allochthonous ophiolitic section. Penetration into the ophiolites by a well, proximity of well location to the Cirali gas seepage (60 km NE of the seepage) and 2D seismic sections acquired in the region make the study area a perfect spot to test the applicability of integrated methods for natural H2 exploration.
The most significant finding along the ophiolitic section of the A-1 well is the presence of a peak in radiogenic heat generation that might indicate a potential natural H2 generation zone. On the other hand, thermal models derived from the interval velocities of 2D seismic survey nearby indicate that vast majority of generated H2 by serpentinisation process must have migrated from the deepest sections of the ophiolites as temperatures are generally quite low in the area. Apart from that, thermal models also demonstrate the presence of temperature anomalies exhibiting themselves as rapid lateral increases in temperatures that can be associated with the fluids in the sedimentary succession.
As a conclusion, this study provides a unique workflow to reveal potential natural H2 generating zones that can be applied all along the wells if 232Th-238U-40K concentration measurements cover zone of interest not only in the Eastern Mediterranean but for any region. In terms of play fairway, 2 play types have been identified. Naturally generated H2 can accumulate both in the serpentinites as it is already proven by Chimera gas seepage, or it can migrate into Plio-Miocene aged reservoirs in the area. In terms of expulsion mechanism, heavy deformation and compressional tectonic phase controlled by ongoing convergence of African and Anatolian plates create faults and fracture zones that might allow migration of natural H2 from the deeper sections into the shallower structures. However, detailed geomechanical analysis should be performed to understand and prevent potential seal breach risks. The methodologies provided by this study might unlock the path to a potential natural H2 discovery that can turn the Eastern Mediterranean region into a unique natural H2 exploration theatre.
How to cite: Uyanik, A.: Highlighting Natural H2 Generation Potential of the Eastern Mediterranean Ophiolites by Implementing 232Th-238U-40K Concentration Measurements and Thermal Modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-758, https://doi.org/10.5194/egusphere-egu26-758, 2026.
Helium is a critical raw material for medical, industrial, and scientific applications, yet its global supply is largely dependent on hydrocarbon production, linking helium availability to CO₂ emissions and geopolitical constraints. This dependency has driven growing interest in alternative, low-carbon helium sources, particularly radiogenic helium systems associated with N₂-rich and CO₂-poor geological fluids. However, the geological controls on helium generation, migration, and accumulation in such non-hydrocarbon systems remain poorly constrained.
Radiogenic helium systems require the combination of a U–Th-enriched crystalline basement generating helium through alpha decay, sufficient heat to liberate helium from mineral hosts, and fault- and fracture-controlled pathways enabling upward migration while limiting diffusive loss. Where suitable reservoir and seal configurations exist, migrating helium may locally accumulate. Continental rift and geothermal provinces seem especially favourable for these conditions due to elevated heat flow, crustal thinning, and dense fault networks.
In this study, we first compile helium data from the literature to produce a Europe-wide map linking helium occurrence to rifts, sedimentary basins, and Variscan basement exposures, providing a european framework for helium exploration. New helium concentration data from thermal fluids in the Upper Rhine Graben are used to assess the spatial distribution of helium fluxes and their relationship with fault architecture. While near-surface degassing limits shallow accumulation, major fault systems emerge as first-order controls on helium transport. Their deeper continuations beneath sedimentary basins represent promising exploration targets where appropriate reservoir–seal configurations may allow helium retention. This study provides a preliminary framework to guide exploration of helium in European rift and geothermal settings.
How to cite: Wallentin, A., Murray, J., Truche, L., and Lemarchand, D.: Exploring Helium in European Rifts: New Insights from the Upper Rhine Graben, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2992, https://doi.org/10.5194/egusphere-egu26-2992, 2026.
Reliable subsurface temperature models are a key prerequisite for geothermal exploration, reservoir assessment, and broader subsurface energy applications. Within the GeoChaNce research project, we present an integrated geological and thermal characterization of the Bavarian part of the North Alpine Foreland Basin (NAFB), combining petrophysical analyses of a large heterogeneous well dataset with advanced geostatistical modelling approaches.
The thermal analysis focuses on developing a fully volumetric 3D temperature model that covers depths ranging from 300 m to 5000 m true vertical depth. The temperature dataset comprises 196 bottom-hole temperature (BHT) values, which were corrected using Monte Carlo methods to account for uncertainty, and 19 high-quality continuous temperature logs, including wireline and fiber-optic measurements. To robustly account for data heterogeneity and measurement uncertainty, particularly in the error-prone BHT correction methods, Empirical Bayesian Kriging (EBK) was applied within a 3D framework. The model was computed on a 100 × 100 × 100 m voxel grid and provides probabilistic temperature distributions for P10, P50, and P90 scenarios. Cross-validation using a leave-one-out approach yields a mean standard error of 5.6 K, with more than 87% of predictions falling within the modelled 90% confidence interval.
The resulting temperature model reproduces well-known regional thermal anomalies of the Molasse Basin, including positive anomalies in the Munich and Landshut areas and a pronounced negative anomaly associated with the Wasserburg Trough. In addition, a 3D Empirical Bayesian Indicator Kriging approach was used to derive probability maps for reaching specific temperature thresholds (e.g., 80 °C and 100 °C), providing a robust probabilistic framework for geothermal assessment.
Ongoing work focuses on coupling the solely statistical EBK temperature model with lithology-specific thermal conductivity data derived from laboratory measurements, mixing-law models, and petrophysical interpretations of logging data. This will allow calibration of the temperature field, derivation of regional heat-flow densities, and calculation of horizon-based temperature gradients. The GeoChaNce results provide an improved, uncertainty-aware thermal framework for the Bavarian Molasse Basin, contributing to more reliable geothermal resource assessments and forming a key component for a future geothermal decision-support system for the reservoir.
How to cite: Schölderle, F. and Zosseder, K.: From Heterogeneous Well Data to Probabilistic 3D Temperature Modelling of the Bavarian Molasse Basin for Geothermal Exploration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13093, https://doi.org/10.5194/egusphere-egu26-13093, 2026.
The Upper Jurassic to Lower Cretaceous (Purbeck) sedimentary succession of the South German Molasse Basin, here referred as the Malm Reservoir, hosts one of the largest hydrothermal resources in continental Europe. It exhibits strong heterogeneity driven by depositional facies variability within a sequence stratigraphic framework, diagenetic overprint including karst horizon development, and structural elements typical for foreland sedimentary basins. The GIGA-M project aims to study the deep geothermal reservoir of the greater Munich area through integrated well data and large-scale 3D seismic interpretation, providing the geological basis for a reservoir management model enabling synergetic geothermal utilisation. Hydraulically active zones in the most productive geothermal wells are commonly observed within karstified intervals (Hörbrand et al., 2025, Schölderle et al., 2023) and are therefore commonly described as one of the main reasons for the exceptional productivity of the reservoir. Facies architecture and Mesozoic to Cenozoic faults further influence reservoir heterogeneity and fluid flow. Karst horizons are unevenly distributed throughout the reservoir, indicating a complex interplay of syn-depositional and diagenetic controls that is common in many karstified carbonate reservoirs worldwide.
This study evaluates how sequence stratigraphy, facies architecture, and karst development control flow zones and matrix porosity in the Malm Reservoir. The analysis focuses on stratigraphic and facies organisation and karst characterisation. Available well data and recent studies indicate that fault systems and fractures play only a minor role in the hydraulic behaviour of the Malm Reservoir; consequently, they are not a primary focus of this study. Our workflow integrates geophysical well logs, mud-log descriptions, and borehole image logs to identify and classify karst features in wells and, where flow data are available, to correlate karst categories with observed flow zones. This approach enables the recognition of karst horizons associated with enhanced porosity and permeability, directly relevant to reservoir quality and well-interference assessment.
A regional sequence stratigraphic framework (Wolpert et al, 2022; Wolpert, 2020) is used to link relative sea-level changes to facies distribution within the carbonate ramp system. Facies associations primarily control matrix porosity and storage properties, whereas sequence boundaries mark exposure surfaces and sedimentary gaps where karst can develop. While early diagenetic karst may initiate at sequence boundaries, the most extensive karst development is interpreted to result from prolonged subaerial exposure of the reservoir during the Cretaceous, highlighting the critical importance of identifying and differentiating sequence boundaries according to their timing and duration of exposure. This Cretaceous karst generation is considered the main candidate for the laterally extensive karst systems that cross-cut facies boundaries and form the main geothermal flow zones, as confirmed by flow observations in wells. These karst horizons exert a first-order control on transmissivity and hydraulic connectivity. Within the GIGA-M project, this stratigraphic and karst framework provides the geological basis for developing facies- and karst-probability maps calibrated with existing and future GIGA-M 3D seismic data, enabling the assessment of flow connectivity and well interference and supporting geothermal reservoir management at the greater Munich area scale.
How to cite: Crinière, A., Ernst, V., Beichel, K., Bendias, D., Bamberg, B., Schölderle, F., Nasralla, M., Pfrang, D., Banerjee, I., and Zosseder, K.: Sequence-stratigraphic control on facies and karst in Europe’s largest geothermal carbonate reservoir: The Malm Reservoir of the South German Molasse Basin (greater Munich area), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18135, https://doi.org/10.5194/egusphere-egu26-18135, 2026.
Young igneous geothermal systems recharge by magmatic activity. Due to Iceland’s location on the mid-ocean ridge, repeated dyking compensates here for the spreading. This study examines the impact of intrusive and eruptive events on the thermal evolution of the Krafla geothermal system. The so-called “Krafla fires” in 1975-84 were a volcanic episode comprising 20 intrusive and eruptive events, during which seven of them intersected the geothermal system.
The effects of repeated dyking on temperature, pressure, and enthalpy, as well as steam content, are modelled in simple 2D profiles with HYDROTHERM (USGS). Calculating a heat budget can help to exploit geothermal energy sustainably: How much energy is inputted by the dykes into the geothermal system? How much of this heat is lost to the atmosphere by advection and conduction? How fast is heat transferred in the subsurface?
The total heat input of the dyke into the geothermal system is 0.5-1 x 1018 J. During, and shortly after the eruptive episode, the dyke nearly cools down to the ambient temperatures of the system. Models and previous analyses of steam clouds in air photos indicate that around 10 % of the heat is lost from the surface to the atmosphere, mostly in the first weeks/months after the dyking event, while 90 % of the dyke’s energy is dissipated into the geothermal reservoir. As the system is already close to the boiling point, the additional heat input by the dyke, leads to steam generation, which rises in the high-permeable lava-hyaloclastite layer. It collects below the clay cap and rises through fissures and fractures. In the lower permeable layer of basement intrusions, the steam is less mobile and stays in the vicinity of the dyke. The main changes in temperature and pressure can be observed in the two-phase and superheated steam regions, where enthalpy increases strongly compared to the initial setting. Long-term simulations indicate that the heat input by the dykes formed in the Krafla fires remains in the reservoir for at least several decades and plays a critical role in maintaining the geothermal system.
How to cite: Fehrentz, P., Gudmundsson, M. T., and Reynolds, H. I.: Thermal effects of intrusive events on geothermal systems: Heat transfer modelling during (and after) the Krafla volcano-tectonic episode 1975-84, NE-Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18250, https://doi.org/10.5194/egusphere-egu26-18250, 2026.
Global copper demand is projected to increase from 22.8 Mt in 2024 to 35 Mt by 2040, driven largely by the transition to green energy technologies. Existing and announced Cu mining projects are forecast to meet only 70% of this demand by 2035, creating a significant supply deficit. Mining of subvolcanic magmatic brines - hypersaline and potentially supercritical fluids enriched in metals – has been proposed as an alternative source (Blundy et al., 2021). Here, we assess the potential mass of Copper Initially in Place (CIIP) in such reservoirs.
Based on published resistivity models from 46 active magmatic-hydrothermal systems, we estimate the typical volume of brine reservoirs to range from 10 to 200 km3 and the average top reservoir depth to be 1.7 km, well within reach of modern drilling technology. Typical reservoir porosity in the shallow sub-critical zone is 8±6% and decreases to 3±3% in the deeper supercritical zone. Copper concentration in the brines is the most uncertain property. Data from fluid inclusions and Cu solubility modelling suggest that most brine reservoirs will host modest Cu concentration (ca. 10’s to 100’s ppm), but values could exceed 10,000 ppm in the most Cu enriched systems.
We combine these estimates of reservoir volume, porosity and copper concentration using a probabilistic Monte Carlo framework to provide estimates of CIIP. Our analysis indicates a lognormal CIIP distribution with a median (P50) of 8.6 Mt and a P90 of 55 Mt, suggesting that individual magmatic brine resources may be comparable in size to conventional copper porphyry deposits. Moreover, a single high-flow-rate well tapping into a supercritical reservoir could produce approximately 2.4 kt of copper per year. A large-scale operation comprising multiple wells could yield 0.24 Mt/year, equivalent to roughly 1% of current global demand.
A Cu brine mine could extract geothermal energy from the produced fluids. We envisage a self-powered Cu brine mine, with net positive energy per kg of Cu and a minimal environmental footprint. While significant challenges remain regarding exploration for copper-rich brine reservoirs and production of very hot and possibly supercritical brines, brine mining offers a potentially significant source of Cu that could be produced with much lower energy demand and negative environmental impact than conventional mining.
Blundy, J., et al. "The economic potential of metalliferous sub-volcanic brines." Royal Society Open Science 8.6 (2021): 202192.
How to cite: Paulatto, M., Jackson, M., Hu, H., Berry, A., Crisp, L., Beckie, R., and Pacey, A.: Assessing potential ‘copper in place’ in subvolcanic brines, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10130, https://doi.org/10.5194/egusphere-egu26-10130, 2026.
Posters on site: Mon, 4 May, 10:45–12:30 | Hall X4
Natural hydrogen (H₂), often referred to as white hydrogen, is attracting increasing attention as a potential subsurface energy resource. Its occurrence, migration, and preservation are strongly controlled by faults and fracture networks, which regulate fluid flow, fluid–rock interactions, and overall reservoir integrity. This contribution provides a state-of-the-art review of current research on natural hydrogen systems, with particular focus on the role of fault and fracture zones and on recent advances from Italy as an emerging natural laboratory.
At the global scale, natural hydrogen has been reported in a wide range of structurally complex geological settings, including rift zones, ophiolitic complexes, mid-ocean ridges, sedimentary basins, and fractured crystalline basement (e.g., Zgonnik, 2020; Wang et al., 2023; Sequeira et al., 2025; Gorain, 2025). Hydrogen can be generated through multiple processes—such as serpentinization, radiolysis, organic matter pyrolysis, and mantle degassing—that commonly operate in tectonically active and faulted environments. Owing to its small molecular size and high diffusion coefficient, hydrogen migration is particularly sensitive to fracture connectivity, fault permeability, and fault (re-) activation, making structural architecture a primary control on both accumulation and leakage.
Field observations, well data, and monitoring studies indicate that hydrogen frequently migrates along fault and fracture networks, may accumulate transiently within structurally controlled traps, or is released at the surface through focused seepage (Prinzhofer et al., 2019; Baciu and Etiope, 2024). Recent studies emphasize that circulation of hydrogen-rich fluids within fault zones can significantly modify the mechanical and transport properties of host rocks through fluid–rock interactions, potentially leading to either enhanced or reduced permeability and sealing capacity (Sequeira et al., 2025; Gorain, 2025). These coupled processes have important implications for fault stability, leakage risk, and the long-term viability of subsurface energy systems.
In this context, Italy is a particularly favourable setting for research on natural hydrogen. The country hosts a broad spectrum of geological environments conducive to hydrogen generation and migration, including ophiolites, such as those exposed in the Tuscan–Emilian Apennines, active fault systems, geothermal areas, and sedimentary basins sealed by evaporites. Recent structural, geochemical, and geophysical studies suggest that the occurrence of hydrogen in Italy is closely linked to fault architecture, deformation processes, and multiscale fluid circulation (Azor de Freitas et al., 2025).
By integrating global observations with insights from Italian case studies, this review outlines current research trends, identifies key knowledge gaps, and highlights the need for multidisciplinary approaches combining field investigations, monitoring of potential gas emissions from active fault systems, interpretation of subsurface data and conceptual modelling of potential reservoirs and hydrogen emission areas. These insights are directly relevant to low-carbon energy exploration and to the assessment of fault-controlled leakage, reservoir performance, and system stability in subsurface energy applications.
How to cite: Cremonesi, A., Borghini, L., Corradetti, A., Del Ben, A., Franceschi, M., and Bonini, L.: Understanding natural hydrogen systems: From generation to surface emissions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6527, https://doi.org/10.5194/egusphere-egu26-6527, 2026.
Natural hydrogen (H₂) emissions in the northern United Arab Emirates (UAE) occur within the northern continuation of the Semail Ophiolite, where serpentinized peridotites, fault permeability, and groundwater circulation jointly control H₂ generation and migration. Recent soil-gas surveys in Ras Al Khaimah (RAK) and the Masafi structural window report systematic H₂ anomalies above a regional background, including locally elevated concentrations along fault corridors and lithological contacts. In parallel, regional geophysical studies in the UAE–Oman mountain belt provide independent constraints on the ophiolite’s three-dimensional architecture, indicating kilometre-scale thickness variations and structural segmentation, while broadband magnetotelluric (MT) models resolve resistivity contrasts and conductive zones consistent with fluid-focused deformation along major fault systems.
Here we develop an integrated, exploration-oriented workflow that constrains depth-resolved ultramafic/serpentinized source geometry and evaluates its spatial consistency with mapped surface H₂ anomalies. We combine available gravity and magnetic datasets with petrophysical constraints and geological priors to perform petrophysically guided joint inversion, targeting (i) the depth extent and volume of ultramafic bodies, (ii) the distribution of serpentinization-related physical property changes, and (iii) structurally controlled corridors that may promote water ingress and gas migration. Where available, MT-derived constraints on conductive pathways and seismic interpretations of basin/foreland structure are used to reduce non-uniqueness and to test competing structural models.
We then translate the recovered 3D ultramafic geometry into bounded H₂ generation estimates by coupling volume-based metrics with physically realistic limits, including temperature constraints informed by regional geothermal/Curie-depth patterns and process caps imposed by hydrogen solubility and water supply. Spatial comparisons between predicted subsurface H₂-favourable domains and mapped soil-gas anomalies provide a quantitative test of whether surface signals preferentially occur above specific ophiolite blocks and fault systems. The results establish a reproducible template for assessing hydrogen in ophiolite-hosted environments under realistic data availability, supporting evidence-based prioritization of targets in the UAE and across the wider Arabian ophiolite belt.
How to cite: Sobh, M., Ali, M. Y., Saibi, H., Abdelmaksoud, A., and Fadel, I.: Imaging and quantifying ophiolite-hosted natural hydrogen potential in the northern UAE Semail Ophiolite using petrophysically guided joint inversion of geophysical data , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7111, https://doi.org/10.5194/egusphere-egu26-7111, 2026.
Geological hydrogen and helium exploration have increased substantially in recent years, driven by requirements for the energy transition and high-tech industries. These efforts have highlighted the need for fundamental understanding of the underlying geologic systems influencing the generation, migration, and storage of these gases. Since hydrogen (H2) and helium (He) are naturally produced in the subsurface via chemical and nuclear reactions involving major igneous rock types that are common in crystalline basements (e.g., mafic/ultramafic for hydrogen and felsic for helium), predicting and mapping basement terranes and lithologies has become a key focus in these new exploration efforts. Further, historical data from oil and gas wells have suggested the presence He and H2 at depth. While these findings offer promising leads, many of these measurements are outdated and require modern verification to assess their current relevance and potential for commercial accumulation.
Our research aims to generate regional-scale interpretations of the He and H2 system across the state of Texas. To this end, we explore field and well data to complement and refine existing basement lithology interpretations previously derived from core and geophysical data. The main contribution of our work is the application of Bayesian analysis as the basis for joint inversion of gravity and aeromagnetic data to produce probabilistic estimates of basement lithologies throughout the state. Secondly, the extensive analysis of soil and well gas samples for determining He and H2 generation and storage. Thirdly, improve well log analysis of basin scale lithological interpretations to increase the accuracy of the hydrogen and helium migration and storage potential across the system. These methods ultimately aim to significantly improve the predictive capability of He and H2 plays based on a suite of geochemical and geophysical data.
The research is currently focusing on the Permian Basin and Ouachita Thrust Belt region in West Texas (USA) that have traditionally been targeted for oil and gas exploration. The Mesoproterozoic basement of the Permian Basin forms an intractonic sag and consists of a complex assemblage of igneous and metamorphic rocks, which are rock types known to generate He and H2. Interestingly, the basin comprises a 300-1200 m thick Permian evaporite sequence, which may act as an effective seal for basement-sourced He and H2. A soil gas survey was conducted to identify potential emission zones and to evaluate the sealing potential of the evaporite sequence. This survey was complemented by well data to investigate gas presence below any overburden. In the most favorable areas, long-term H₂ monitoring was implemented to assess possible cyclicity (e.g., diurnal, seasonal) in gas emissions. Basement rock sampling and well gas analyses provide insights into both past and potentially ongoing reactions beneath the overburden, helping to constrain the He and H2 system and the geological controls.
In this presentation, we demonstrate this approach to generate Texas-wide basement lithology maps. We focus on specific compositions relevant to geologic He and H2 exploration, and highlight the utility of these maps to help focus future exploration and development efforts for this rapidly growing field of study.
How to cite: Thompson, J., Schuba, C. N., Pasquet, G., Salah, S., Rodriguez Calzado, E., Horne, E., Arasada, R., Mow, V., Kasperczyk, D., Markov, J., Bhattacharya, S., Moscardelli, L., and Shuster, M.: Building a Picture of the Geological Hydrogen and Helium System in West Texas, USA, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13651, https://doi.org/10.5194/egusphere-egu26-13651, 2026.
The evidence base for geological hydrogen sources is expanding rapidly, moving from anecdotal reports to systematic surveys, exploration, and focused research that address fundamental knowledge gaps. These efforts will determine whether geological hydrogen remains a small-scale, local energy source or can evolve into a large-scale resource capable of contributing meaningfully to the global energy transition. In this interactive presentation, we aim to present and discuss effective ways of applying thermo-hydro-mechano-chemical (THMC) modelling approaches to geological hydrogen research. The objective is to reduce interdisciplinary barriers and to enable effective discussion that optimizes the use of THMC modelling for constraining fundamental research questions. These questions primarily relate to assessments of geological hydrogen resource potential and to informing exploration strategies and detection methods.
Much of the scientific and technical progress in deep-seated applications in recent decades has benefited from the development of THMC numerical and theoretical models. Such applications range from fossil fuel exploration and recovery to geothermal energy utilization, ore-forming systems, and the assessment and mitigation of induced seismicity. These advances were facilitated by improvements in computational capability and algorithmic development, enabling effective integration of experimental results and field observations into models. This has often enabled the development of a mechanistic understanding of nonlinear and tightly coupled THMC processes operating at depth across wide spatial and temporal scales.
Geological hydrogen systems are similarly governed by crustal processes, which can be described as interconnected components encompassing the generation, migration, accumulation, and preservation of hydrogen. Leveraging established multiphysics modelling approaches to investigate these components can provide valuable insights. Key examples include constraining migration mechanisms of dissolved or free-phase hydrogen from deep source regions toward potentially exploitable reservoirs, and assessing fluxes into and out of hydrogen reservoirs. Assessing the relative timescales can enable first-order evaluation of losses due to biotic and abiotic reactions, as well as accumulation potential.
How to cite: Aharonov, E., Roded, R., and Toussaint, R.: A cross-disciplinary exchange between modelling, field studies, and industry: How can multiphysics modeling advance geological hydrogen resource development?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16404, https://doi.org/10.5194/egusphere-egu26-16404, 2026.
Abstract
Against the backdrop of the global energy transition, hydrogen is gaining prominence as a clean energy carrier due to its zero emissions and high energy density. In-situ gasification of crude oil reservoirs for hydrogen production has thus emerged as a promising technology. However, conventional process of H2 production from crude oil suffer from high operating temperatures and energy consumption. Developing effective catalysts to lower the required reaction temperature is therefore crucial.
In this study, a series of Fe-based catalysts, including Fe-Zn, Fe-Co and Fe-Ni composite catalysts, were developed. Their properties were comprehensively characterized, and their catalytic performance was evaluated through hydrous pyrolysis experiments. The results indicate that all catalysts significantly reduced the initial hydrogen production temperature. The Fe‑Ni catalyst exhibited the best performance, followed by Fe‑Co and Fe‑Zn. The abundant micropores in these catalysts facilitated the cracking of short‑chain hydrocarbon intermediates, thereby enhancing hydrogen yield. Furthermore, the presence of Fe improved the catalysts' resistance to coking. The reaction mechanism during in‑situ catalytic gasification of crude oil was also explored. This work provides theoretical insights and technical guidance for the future engineering application of in‑situ hydrogen production from crude oil gasification.
Keywords: Hydrogen production; Crude oil; In-situ gasification; Fe-based catalyst
How to cite: Deng, S., Liu, H., and Guo, W.: In-situ catalytic hydrogen production from crude oil gasification using Fe-based composite catalyst: An experimental investigation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16296, https://doi.org/10.5194/egusphere-egu26-16296, 2026.
Energy consumption and heating efficiency are key bottlenecks constraining the large-scale application of in-situ conversion technology. Autothermic pyrolysis in-situ conversion technology (ATS) proposes an innovative solution: by injecting oxidants such as ambient-temperature air into preheated shale formations, the exothermic oxidation reaction of residual carbon after the thermal cracking of kerogen is utilized to continuously generate substantial heat. This sustains the self-propagating thermal cracking process within the reservoir, significantly reducing the need for external energy supply. Laboratory experiments and numerical simulations show that, through precise control of process dynamics, the technology can achieve an energy efficiency of up to 14.80. With the auxiliary injection of a small amount of hydrocarbon gas, its applicability in shale formations with oil content below 5.0% can also be greatly enhanced.
To advance the engineering application of this technology, our team has developed a series of supporting key technologies, including efficient heating technology, shale complex fracture network construction technology, cross-scale multi-field coupling numerical simulation technology for thermal, fluid, solid, and chemical processes, underground space sealing technology, in-situ catalytic enhancement technology, and an integrated development system combining in-situ conversion, waste heat recovery, and CO₂ sequestration. This has established a comprehensive technological support system. Based on these technologies, our team has conducted two pilot tests in the Qingshankou Formation and Nenjiang Formation of the Songliao Basin in China, at formation depths of 80 meters and 480 meters, respectively. Both tests successfully extracted crude oil and natural gas, verifying the feasibility of this technological approach.
With the growing global demand for cleaner extraction of fossil energy resources, this technology can be widely applied in areas such as in-situ development of oil shale and low-to-moderate maturity shale oil, in-situ coal-to-oil and gasification, in-situ hydrogen production from crude oil, and high-temperature upgrading of heavy oil, demonstrating broad prospects for engineering applications.
How to cite: Guo, W., Zhu, C., Li, Q., Deng, S., and Bai, F.: Autothermic Pyrolysis in-situ Conversion Technology and Pilot Test Project, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15257, https://doi.org/10.5194/egusphere-egu26-15257, 2026.
Solid bitumen is an important organic matter (OM) component in shale systems, and its chemical and resulting nanopore structure exert a strong control on unconventional reservoir properties. Solid bitumen is commonly regarded as a product of thermal evolution of primary kerogen or secondary transformation products such as retained oil. The nanoporous structure of post-oil solid bitumen is strongly influenced by the molecular composition of its organic precursors.
In this study, pyrolysis experiments on heterogeneous precursor oil samples were conducted to systematically investigate the coupled chemical and nanostructural evolution of solid bitumen under proceeding thermal maturation. A combination of Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, optical reflectance measurements, pore structural characterization, and scanning electron microscopy (SEM) was applied.
The results show that the size and arrangement of aromatic structural units and the abundance of functional groups vary for solid bitumen derived from different oil types at comparable thermal maturity level. These nanostructural variations control nanopore development, leading to systematic differences in pore types and pore size distributions among samples. Micropores and small mesopores are closely linked to the growth, stacking, and structural reorganization of aromatic clusters, whereas stress-related processes mainly control larger mesopores and therefore exhibit a weaker coupling with molecular-scale aromatic evolution.
This study suggests that nanopore development in post-oil solid bitumen is not solely governed by thermal maturity but is also strongly influenced by the composition of precursor oils. These findings are important for assessing the fluid storage and transport behavior of fine-grained OM-rich sedimentary rocks.
How to cite: Fan, Q., Cheng, P., Xiao, X., and Misch, D.: Coupled chemical and nanostructural evolution of solid bitumen derived from oils with heterogeneous composition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19864, https://doi.org/10.5194/egusphere-egu26-19864, 2026.
With the growing emphasis on reducing the carbon footprint of transport, there is increasing interest in identifying local sources of hydrogen (H₂) and helium (He) closer to consumers. In this context, we present an integrated approach combining near-surface geophysical imaging, soil gas sampling, and bubbling well gas sampling to investigate fluid and gas pathways near a fault system in the Morvan massif, located in the southeastern Paris Basin. Using electrical resistivity and seismic refraction tomography, we mapped a fault network in the area. Soil gas sampling along these faults revealed a helium hotspot, strongly linked to a specific fault segment, indicating a preferential pathway likely driven by water advection. Additionally, exceptionally high helium concentrations were detected in nitrogen (N₂)-dominated free gas from two nearby bubbling wells, closely associated with the soil helium hotspot. Our geophysical data further suggest the presence of a shallow water reservoir at the basement-sediment interface, containing N₂-He gas bubbles. In contrast, hydrogen (H₂) exhibits a broader spatial distribution, likely due to biological production and consumption processes, as well as soil aeration. A potential geological seep, with diffusion controlled by clay and marls, may also contribute to H₂ dispersion. The distinct spatial patterns observed for He and H₂ reflect their differing transport mechanisms. We propose a simple geochemical model to explain the N₂- and He-rich signature of the bubble gas, attributing it to the exsolution of dissolved atmospheric N₂ during recharge, while radiogenic He originates from the underlying granitic basement.
How to cite: Léger, E., Sarda, P., Bailly, C., Zeyen, H., Pessel, M., Portier, E., Dupuy, G., Lambert, R., Courtin, A., Guinoiseau, D., Calmels, D., Durand, V., Monvoisin, G., Battani, A., Moreira, M., Barbarand, J., and Brigaud, B.: Deciphering Intermittently Bubbling Degassing Mechanisms of He‐Rich N2 ‐Bubbles at theSedimentary Basin‐Basement Interface by Surface Geophysics and Gas Geochemistry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9629, https://doi.org/10.5194/egusphere-egu26-9629, 2026.
The dual production of geothermal energy and lithium from fault-controlled reservoirs, such as the Rittershoffen doublet in the Upper Rhine Graben (URG), presents a significant opportunity for the energy transition. However, long-term feasibility depends heavily on the complex interplay of fluid flow and chemical transport. We developed a numerical model using a control volume finite element method with embedded discontinuities, calibrated against comprehensive field data (pressure transients, tracers, and thermal profiles).
Our results reveal a highly heterogeneous flow field: a rapid primary path through the major fault/damage zone creates hydraulic "short-circuits," while slower secondary paths sweep the surrounding fractured reservoir. While thermal energy production remains remarkably stable over a 50-year forecast, lithium concentrations are more sensitive to these flow dynamics.
We show that in the absence of active lithium leaching, concentrations decline as lithium-depleted brine recirculates. However, we demonstrate that even modest leaching rates (0.3 g/m3/yr) can sustain concentrations above 100 ppm. These findings highlight that constraining in-situ leaching rates and hydraulic connectivity is not just a geological challenge, but a critical requirement for de-risking the "lithium-from-brine" industry in the URG.
How to cite: Lamy-Chappuis, B., Pezzulli, E., and Driesner, T.: Numerical Modeling of Geothermal Heat and Lithium Co-Production in Fault-Hosted Reservoirs, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11903, https://doi.org/10.5194/egusphere-egu26-11903, 2026.
The Upper Jurassic-Lower Cretaceous (Malm-Purbeck) reservoir of the North Alpine Foreland Basin (NAFB) in Bavaria represents one of Europe’s most important deep hydrothermal reservoirs for sustainable heat supply. Reservoir transmissibility shows strong spatial variability and remains insufficiently characterized. In particular, the linkage between basin-scale transmissibility, vertically resolved hydraulically active zones, and their sequence stratigraphic context has not yet been systematically investigated. This gap is addressed by integrating transmissibility, hydraulically active zones, and a sequence-stratigraphic framework to provide a comprehensive characterisation of the reservoir.
Transmissibility values were derived from pressure transient analyses of geothermal and research well tests, resulting in a harmonised dataset of 57 high-quality measurements across the NAFB. These data were used to generate a basin-wide probabilistic transmissibility map using Empirical Bayesian Indicator Kriging (EBIK), a geostatistical approach that explicitly accounts for spatial uncertainty and is well-suited for sparse datasets. The resulting map confirms a general decrease in transmissibility with increasing burial depth from north to south, while also revealing regional deviations from this trend.
To resolve reservoir heterogeneity at the vertical scale, flowmeter measurements from 14 wells were analysed to identify hydraulically active zones and quantify their relative contribution to total flow. By distributing total well transmissibility according to flow contribution and zone thickness, transmissibility values were converted into permeability for individual hydraulically active zones. This approach reveals a systematic decrease in permeability with depth, characterized by distinct regional reservoir types previously identified by multivariate statistical analyses.
Hydraulically active zones were further positioned within a sequence-stratigraphic framework, enabling basin-scale correlation. The results demonstrate that hydraulically active zones occur predominantly within specific sequence-stratigraphic intervals, while deeper units contribute progressively less to flow. Although sequence-stratigraphy does not directly control permeability magnitude, it provides a consistent framework for understanding the vertical distribution of flow zones. Overall, this study provides the first integrated basin-scale assessment linking transmissibility, hydraulically active zones, and sequence stratigraphy in the NAFB. The results significantly improve reservoir characterisation, form a robust basis for static and dynamic modelling, and will be a key component of a decision support model for deep geothermal energy in the future.
How to cite: Ernst, V., Felix, S., Crinière, A., and Zosseder, K.: Characterising the Heterogeneity of Transmissibility and Hydraulically Active Zones in the Deep Geothermal Reservoir in Bavaria , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20209, https://doi.org/10.5194/egusphere-egu26-20209, 2026.
Salt tectonics is often simplified with a homogeneous halite rheology, but natural evaporite sequences are heterogeneous, including frictional-plastic anhydrite and low-viscosity K-Mg salts, that can alter the architecture and controlling factors of intra-salt deformations in diapiric structures. We use 2D high-resolution finite-element simulations (FANTOM) to investigate how the vertical position of intra-salt layers controls the formation, geometry, and internal architecture of salt diapirs. The models simulate diapirism driven by sedimentary loading (with varying sedimentation rates and no basal tectonics) and explore different intra-salt stratigraphies. Our results shows that layer position have a first-order control on diapir evolution. When an anhydrite layer is placed at the top of the salt sequence, it acts as a stiff caprock that limits salt flow, resulting in a broad, low-relief salt structure with minimal surface deformation. In contrast, a mid-level anhydrite induces flow partitioning and a bimodal deformation pattern: it decouples movements above and below anhydrite, producing sharp diapir margins and localized folding and disruption of the internal layers. This leads to contrasted intra-diapir complexity. If the strong layer is located near the base of the salt, it initially shows high diapirism from the upper salt but eventually forces the lower salt to flow inside this first diapirs. These tall diapirs are associated with intense rotation of the minibasins and the development of welds where the intra-salt layer breaks and salt flows upward. The presence of low-viscosity K-Mg salt layers further amplifies internal deformation: these weak units flow fast and undergo drastic thinning, creating additional shear zones and irregular internal geometries without significantly impeding diapir growth. Our high-resolution models demonstrate that even thin intra-salt layers significantly influence the localization of deformation, thereby shaping both the external form and internal structure of diapirs. These results are applicable to layered evaporite sequences (LES, e.g. Zechstein Basin) and offer a new way for interpreting complex intra-salt features observed at the seismic scale. These insights have important implications for structural interpretation, resource exploration, and the development of salt formations as effective caprock for CO₂ and for hydrogen storage in salt caverns.
How to cite: Ramos, M., Huismans, R., Pichel, L. M., Theunissen, T., Callot, J.-P., Pichat, A., Célini, N., Delahaye, S., and Gout, C.: Architecture and controlling factors of intra-salt deformation in diapiric structures: A numerical modelling approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13177, https://doi.org/10.5194/egusphere-egu26-13177, 2026.
