Supporting the transition to sustainable low-carbon economies at scale poses significant challenges and opportunities for the global geoscience community. An integrated and interdisciplinary understanding of the subsurface processes that can provide access to alternative energy supplies and critical raw materials is lacking, 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 sufficient geothermal gradients. Further, it also focuses on providing input for exploration decision-making, the engineering of access strategies to the policy makers as well as for the strategic planning of collaborative research initiatives.
In particular, 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 and helium 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 of hydrogen (H2) and Helium (He).
- Ore deposits: To meet the growing global 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.
Hydrogen use today is mostly as a chemical feedstock, producing ammonia used in fertiliser production amongst other hard to abate uses. Today’s hydrogen is produced directly from hydrocarbons with the resulting CO2 contribution ca 2.4% of global emissions. Hydrogen as a future clean energy vector could see hydrogen demand increase from ca 95 Mt H2 today, to 540 Mt H2 by 2050.
The mass of hydrogen generated within the continental crust is only recently being appreciated as a potential societal resource. Accumulation and preservation of a small portion of the natural hydrogen, in accessible parts of the continental crust, is required. The dominant sources of natural hydrogen are through water-rock reactions with mafic or ultramafic rocks and the radiolysis of water from the radioactive decay of U and Th in rocks. The timescales and environments that enable significant hydrogen generation occur in geological different terrane. These vary from dominantly Phanerozoic ophiolite complexes; Proterozoic-Phanerozoic alkaline granite complexes; Mesoproterozoic-Phanerozoic large igneous provinces (LIP) to dominantly Archean TTG and greenstone belts. The tectonic evolution in each setting, and capacity to form traps, is required alongside the porosity and permeability history that exposes the rock to water. To form a commercial reserve, an environment that produces and preserves a free gas phase from the ubiquitous water over the timescale of the system is required. Helium (4He) provides an analogue for natural hydrogen behaviour and the processes that control both deep-seated flux to the near surface and gas phase formation. Loss due to microbial utilisation remains a high preservation risk.
C Ballentine, R Karolytė, A Cheng, B Sherwood Lollar, J Gluyas, M Daly. Natural hydrogen resource accumulation in the continental crust, In review
How to cite: Ballentine, C.: The character and habitat of natural hydrogen resource systems , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19964, https://doi.org/10.5194/egusphere-egu25-19964, 2025.
As the energy transition gathers steam, naturally occurring hydrogen gas (H2) generated by the serpentinization of mantle rocks is a highly promising sustainable alternative to fossil fuels. To undergo serpentinization, mantle rocks that are normally situated at great depth need to be brought closer to the surface by plate tectonics and other geodynamic processes. Here, they may react with water to be efficiently serpentinized and generate natural H2, which can accumulate in reservoirs as it migrates to the surface (as part of a natural H2 system).
Exploring natural H2 systems requires a solid understanding of their geodynamic history, which can be informed by numerical geodynamic modelling. Through such modelling we can trace how, when, and where mantle material enters the serpentinization window, as well as when active, large-scale faults penetrate exhumed mantle bodies allowing for water circulation, as well as serpentinization and H2 generation, to occur.
Our recent modelling of rifting and subsequent rift inversion (Zwaan et al., in press) shows that, although serpentinization-related natural H2 generation is a phenomenon best known from (magma-poor) rifted margins and oceanic spreading ridges, annual volumes of natural H2 generated during inversion may be up to 20 times higher than during rifting, due to the colder thermal regime in rift-inversion orogenic environments. Moreover, suitable reservoir rocks and seals required for natural H2 accumulations to form are readily available in rift-inversion orogens, whereas they may not be present when serpentinization occurs in deep marine continental rift or oceanic spreading settings.
Our model results thus provide a first-order motivation to turn to rift-inversion orogens for natural H2 exploration and are supported by indications of natural H2 generation in rift-inversion orogens such as the European Alps and Pyrenees.
REFERENCE CITED: Zwaan, F., Brune, S., Glerum, A.C., Vasey, D.A., Naliboff, J.B., Manatschal, G., Gaucher, E.C (in press). Rift-inversion orogens are potential hotspots for natural H2 generation. Science Advances. Link to preprint: https://doi.org/10.21203/rs.3.rs-3367317/v1
How to cite: Zwaan, F., Brune, S., Glerum, A. C., Vasey, D. A., Naliboff, J. B., Manatschal, G., and Gaucher, E. C.: Alpine-type orogens are great sites for natural H2 exploration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2570, https://doi.org/10.5194/egusphere-egu25-2570, 2025.
Serpentinization-sourced H2 has become a promising source of decarbonated energy. It can be generated in fiver tectonic settings, namely: (1) intra-craton settings, (2) divergent settings such as hyperextended rifts, ocean continent transitions and mid ocean ridges, (3) subduction systems, (4) obduction, and (5) rift-inverted orogens. Most recently, many studies have been focusing on parts of the H2-system, i.e., the kitchen, plumbing system, reservoir, cap rock and trapping and preservation mechanisms or on the detection of leaking natural H2 systems at or near the surface. However, a holistic understanding of a serpentinization-sourced H2 system is still in its infancy and an exploration protocol tailored to the different tectonic settings is missing to date.
In our study, we aim to develop a protocol to predict, quantify and explore serpentinization-sourced H2 systems in rift-inverted orogens. To do so, we use the Grisons area (SE Alps in Switzerland) as a field analogue. In this area all play-elements of the serpentinization-sourced H2 system exist and can be accessed and the rift and convergent structures are well exposed and investigated. This allows us to examine the interplay, in time and space, between the play-elements of a serpentinization-sourced H2 system and to develop a predictive exploration protocol. In this perspective, we first seek to define a serpentinization-sourced H2 system in a rift-inversion orogen and second to address when and where the serpentinization-sourced H2 forms, what are the essential play-elements and how they interact in time and space, impacting the location and timing of H2 production by considering the two dominant parameters, temperature and access to water, which determine entry into the serpentinization window (kitchen) for mantle rocks. In our presentation, we show the first preliminary results of our holistic, geological approach aiming to integrate different data sets from the Grisons area. We are aware that to develop a predictive play-element based exploration protocol for a serpentinization-sourced H2 system in rift-inverted orogens, similar to that developed in oil and gas systems, further studies will be necessary.
How to cite: Manatschal, G., Ulrich, M., Chenin, P., Dimasi, F., Gasser, Q., Gaucher, E. C., Masini, E., Zhang, C., Alt-Epping, P., Zwaan, F., and Kusznir, N.: Serpentinization-sourced hydrogen systems in rift inversion orogens: a geological/holistic perspective, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10415, https://doi.org/10.5194/egusphere-egu25-10415, 2025.
The relationships between the serpentinised continental mantle in orogens, its geophysical signature at depth and hydrogen seepages are poorly understood. A petro-physical modelling approach accounting for serpentinisation shows that a large domain of serpentinised mantle is present in the northern Pyrenees. The serpentinisation reached a maximum of 40% during the mid-Cretaceous rifting, according to the predicted temperature and pressure. Although high-temperature serpentinisation could have generated large quantify of hydrogen during the Mesozoic, the shallow and inactive faulting in Northern Pyrenees make this process unlikely to explain the entire serpentinisation inferred by petro-physical modelling. A combination of low-temperature alteration of mafic and ultramafic rocks in the North Pyrenean Zone, active normal faulting in the North Pyrenean Fault, accumulation in local traps and transport of H2-rich fluids along inactive but permeable fault may explain the hydrogen seepages observed today.
How to cite: Robert, A., Pajang, S., Mouthereau, F., Kumar, A., and Callot, J.-P.: A petro-physical model for serpentinised mantle and origin of natural hydrogen in the Pyrenees, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6373, https://doi.org/10.5194/egusphere-egu25-6373, 2025.
Climate-CO2 emission models point to the urgency for European society to transition from high to low carbon energy sources. In this frame, H2 could be a key component of the decarbonization strategy. Among the various colours of H2, white (i.e., native) H2 is one of the most promising. The most efficient way to produce native H2 is serpentinization, a high temperature hydrothermal process that forms serpentinites from Earth mantle rocks. This hydrothermal alteration transforms primary magmatic Fe-Mg-bearing silicates (olivine, pyroxenes) into secondary hydrous minerals (e.g. serpentine, brucite) and oxides (magnetite). Serpentinization also produces molecular hydrogen (H2) through oxidation of ferrous Fe (FeII) released from the dissolving primary minerals, to ferric Fe (FeIII) that precipitates in serpentine and magnetite. The serpentinization process has been extensively documented at various geological settings such as mid-ocean ridges or subduction zones. In contrast, it has received much less attention at rift inverted orogens and continental rifts, representing classical sources of oil and gas, but nowadays being at the forefront of carbon capture, geothermal energy, and new decarbonated energy resources such as native hydrogen. In conclusion, understanding the iron redox state in a Wilson cycle will allow us to predict when, where and how serpentinized sourced hydrogen is produced, which is a prerequisite to develop a successful exploration strategy.
Our approach to achieve this goal is based on a representative sampling area, state-of-the-art analyses and modelling (the evolution of redox and the production of H2). A series of analytical methods will be conducted on serpentinites from well-defined sites (Tasna, Platta, Totalp, Val Malenco and Lanzo) documenting the Wilson cycle of the Alpine-Tethys system. The analysis will constrain the conditions of serpentinization, i.e., temperature of fluid-rock interactions, PT paths recorded by mantle rocks, and redox state. Finally, the new data will constrain the evolution of iron speciation and H2 production during serpentinization and may be used to either test or calibrate numerical modelling results used for the quantification of H2 production.
How to cite: Dimasi, F., Ulrich, M., Muñoz, M., Hochscheid, F., and Manatschal, G.: Iron redox state of serpentinized mantle rocks through a Wilson cycle: implications for serpentinization-sourced hydrogen systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11375, https://doi.org/10.5194/egusphere-egu25-11375, 2025.
This study presents a versatile methodological framework, implemented as a Python-based tool called PoNHy (Potential for Natural Hydrogen), designed to assess hydrogen generation in serpentinization environments using geophysical and laboratory data. As a practical application, the approach robustness is demonstrated in the Mauleon Basin localized in the north-western Pyrenees, where extensive data availability facilitates detailed analyses and validation. The workflow begins with a thorough assessment of key petrophysical properties such as density, magnetic susceptibility, and thermal conductivity. These properties guide the interpretation of underlying geological structures and help refining the initial subsurface models. Building on this foundation, gravity and magnetic data are inverted to determine the distribution and volume of source rocks, as well as their degree of serpentinization. Thermal modeling then delineates subsurface temperature regimes, which play a critical role in the serpentinization reactions and subsequent hydrogen production. To translate laboratory-derived hydrogen production rates into realistic field estimates, the framework integrates parameters from both lab experiments and field observations. Factors such as the water-to-rock ratio, fracture spacing, mineral composition, and specific surface area of reacting materials influence fluid flow, reaction rates, and the overall efficiency of hydrogen generation. By integrating these parameters alongside corrections for the degree of serpentinization, our new methodology provides a more accurate representation of subsurface conditions. This comprehensive integration yields hydrogen generation estimates that better reflect in situ conditions, ultimately improving our understanding of natural hydrogen volumes. Such insights are critical for subsequent transport models aimed at identifying potential reservoirs.
How to cite: Christiansen, R., Sobh, M., Saspiturry, N., and Gabriel, G.: A Multi-Scale Framework for Evaluating Hydrogen Generation in Serpentinization Settings, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1857, https://doi.org/10.5194/egusphere-egu25-1857, 2025.
A significant component to international energy net-zero emission goals is the exploration, production, and utilization of hydrogen. It is estimated that the International Energy Agency’s goal to reduce emissions will require approximately 550 megatons of hydrogen annually. While traditional generation methods through electrolysis (green hydrogen) and from fossil fuels (blue hydrogen) are potential pathways, they each come with challenges in terms of critical minerals consumption and CO2 sequestration. An alternative and promising source of meeting these goals is geologic hydrogen, naturally produced within the Earth's subsurface. Recent studies estimate that over 20 megatons of hydrogen seep from various geological formations annually. A team led by industry pioneers, Pristine Energy and researchers from the Idaho National Laboratory aim to explore the potential of geologic hydrogen in the Eastern Snake River Plain (ESRP), Idaho, USA. The ESRP is characterized by iron-rich basalt formations and mid-crustal mafic sills, both conducive to hydrogen production through serpentinization. Additionally, geothermal gradients and geochemical fingerprinting suggest the potential for rapid serpentinization at depth, giving insight into geologic hydrogen conversion kinetics. This project will proceed through a systematic approach including a thorough literature review, detailed field sampling, field instrumentation and measurements, lab characterization, and preliminary modeling. Gas, water, and soil samples will be collected from identified fissures, faults, hot springs, and existing wells to identify source and estimate rates and quantities of generated hydrogen. Hydrogen concentrations will be measured using advanced sensors and characterized via gas chromatography-mass spectrometry (GC-MS). High-seepage locations will undergo continuous monitoring to understand seasonal variations in hydrogen emissions. This innovative approach leverages the unique geological attributes of the ESRP to contribute significantly to geologic hydrogen exploration and assessment workflows, and ultimately to the global hydrogen supply, supporting net-zero emission goals.
How to cite: Atkinson, T., Neupane, G., Fifo, A., and Sylla, K.: Exploration and Potential of Geologic Hydrogen Production in the Eastern Snake River Plain, Idaho, USA: A Pathway to Net-Zero Emissions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7356, https://doi.org/10.5194/egusphere-egu25-7356, 2025.
Natural emanations consisting of N₂-CH₄-H₂ type gases have been documented across the peridotite nappe of the New Caledonia Ophiolite [1], and the presence of H2 has been attributed to serpentinization [2, 3]. We present new major and noble gas compositional and isotopic data from low to high H2 bubbling gas seep sites from both the south (e.g: Lembi River (≤ 20% H2), Les Pirogues River (≤ 15%), Pourina (≤ 10%)), and north east klippes of the Ophiolite (e.g: Fanama and Nemwegi (≤ 300ppm)), providing new insights into gas origins that can be compared to other serpentinization systems (e.g: Oman, Italy, Turkey, and the Philippines).
Results show that gases are dominated by N2 (60-95%; d15N ranging from -0.2 to +0.1‰ vs air), while the H2 content can reach up to 35% with dD ranging from -740 to -710‰ VSMOW. CH4 reaches up to 20% with d13C ranging from -40‰ to -3.6‰ VPDB. Such major gas composition and isotopic values are characteristic of serpentinization [4, 5]. Additional factors, such as olivine-rich peridotite rocks, precipitation of magnetite, carbonates, and brucite, along with the elevated pH of spring waters (up to 10.5), confirm an active serpentinization system. Hydrogen H2-CH4-H2O isotopic fractionation factors suggest that, despite not being at equilibrium, the hydrogen-bearing fluids are formed at around 50°C, in comparison to 95°C, which was determined using magnetite-dolomite O₂ fractionation [6]. H2 and CH4 likely result from low-temperature serpentinization and processes involving inorganic carbon, respectively; potentially catalysed by Ni, Cr, and Chromitite-hosted Ru [7] which are enriched in the peridotite [1, 8]. Microbial activity indicators such as the presence of biogenic methane, when present, aligns with documented microbial communities.
Helium isotopic data (3He/4He) indicate signatures ranging from predominantly radiogenic (0.3 Ra) in the north, where the crust is thick [2], to ASW-like values in the central south (Lembi and La Coulée), to ~25% mantellic contribution in the southernmost coastal Prony region. We argue that the air-like signature is indicative of the degassing of circulating air-saturated groundwater, which aligns well with interpretations that air-like N₂ present in serpentinization systems may originate from aquifers [2, 3, 4].
Seismic and tectonic data reveal multiple deep faults and fractures in the massif du Sud [9], as well as a shallow Moho and 20 km-deep earthquakes that are indicative of active tectonics detected beneath the Prony area [10]. This explains the facilitated migration of mantle fluids to the surface at Prony.
[1] Maurizot et al., 2020(c). Geol. Soc. Lond. Mem. 51(1), 1–12
[2] Deville and Prinzhofer, 2016. Chem. Geol. 440, 139–147
[3] Monnin et al., 2021. JGR Biogeosci. 126, e2021JG006243.
[4] Vacquand et al., 2018. Geochim. Cosmochim. Acta 223, 437–461.
[5] Etiope, 2017. Procedia Earth Planet. Sci. 17, 9–12.
[6] Corre et al., 2023. Sci. Rep. 13(1), 19413.
[7] Molinet-Chinaglia et al., 2024. ChemCatChem 16(24), e202401213.
[8] Maurizot et al., 2020(f). Geol. Soc. Lond. Mem. 51(1), 247–277.
[9] Lagabrielle et al., 2005. Tectonophysics 403(1–4), 1–28.
[10] https://submap.fr
How to cite: Izerumugaba, J. D. L. P., Battani, A., Deville, E., Maziere, C., Jeanpert, J., Lhote, O., Mouthereau, F., Foucher, W., Monge, O., and Ranchou-Peyruse, A.: Isotopic Insights into the Origins of N₂-H₂-CH₄ emanations in the New Caledonia Ophiolite, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12600, https://doi.org/10.5194/egusphere-egu25-12600, 2025.
Identification of source rocks bearing helium generation potential is essential to construct a robust play fairway for natural helium exploration. The main source rock for helium generation are widely accepted as granitic or metamorphic basement rocks of cratons while some researchers suggest that hydrocarbon source rocks and sediments might also generate helium. One of the most critical implications for potential zones is the presence of radioactivity as He generation is sourced from the alpha decay of 232Th, 238U, and 235U. Thus, more He generation means more decay, characterised by increasing radioactive heat. In addition, distinguishing heavy thorium minerals as clay types by 232Th-40K cross-plots could also indicate potential zones. Therefore, measuring and assessing the 232Th-238U-40K levels play a critical role in any region for natural helium exploration.
This study brings forward well log interpretation approach as one of the transferable methods from the oil and gas industry into natural He exploration by examining the 232Th-238U-40K concentration logs, known as SGR logs, which are generally neglected or overlooked although they provide numerous benefits for subsurface evaluation.
Based on the methodology 2 main research questions emerge for this study to answer;
- Can sediments and hydrocarbon source rocks might generate He or contribute to the He generation process?
- Can SGR Logs provide a robust methodology for detection of potential He generating intervals in sedimentary successions?
To answer these questions, Early and Mid-Triassic sediments from the Northern Arabian Plate are selected as a case study. Recently unlocked Mid-Triassic hydrocarbon play, including source rocks, and CO2 / N2 readings on gas chromatography of nearby wells make the region unique and a perfect study area to test the hypothesis. Radiogenic heat generations (A) have been calculated using the equation below to track radioactivity levels.
A = 0.01 p (9.52 238U + 2.56 232Th + 3.48 40K)
A; radiogenic heat (μWm–3),
p; rock density (g/cm3),
238U, 232Th, 40K; Uranium 238U (ppm); Thorium 232Th (ppm); potassium 40K (%)
Regarding the observations, a 1-15 m. thick, theoretical He generation zone has been detected in the shales of the Early Triassic succession. A consistent significant peak in radiogenic heat levels reaching 4 μWm–3 coincide with rapid increases in calculated He log and heavy thorium minerals content. Additionally, shales are represented by as high 232Th-238U levels as granitic basements. A thickness map of potential He generation zone demonstrates that the zone gets thinner towards ESE at where large fault zones dominate the regional geology.
As a conclusion, the findings of this study suggest that sediments might generate natural He and potential zones might be identified by the help of SGR logs. The results can also shed light on the He generation potential of Triassic sediments deposited in the other regions of the Arabian Plate. Moreover, the proposed workflow can be applied for any region or rock type if the interval of interest is covered by 232Th-238U-40K concentration logs.
How to cite: Uyanik, A.: Can Sediments Generate Helium? Implications from 232Th-238U-40K Concentration Logs from the Northern Arabian Plate, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1138, https://doi.org/10.5194/egusphere-egu25-1138, 2025.
Releasing only heat and water vapour when burnt, demand for hydrogen (H₂) is expected to increase eight-fold by 2050, driven by growth sectors such as transportation and industrial energy. Natural or gold H₂ is produced in the lithosphere via water radiolysis in U- and Th-rich Precambrian basement (alongside helium (He)) or serpentinization in mafic-ultramafic rocks. Gas occurrences in South Australia have anomalously high H₂ concentrations of up to 95%. It is, therefore, an excellent geographical focus to further understand the principles of H₂ exploration (source, migration, accumulation, and preservation).
This study reports noble gas isotopes (He to Xe) of gases dissolved in groundwater samples collected from 19 locations across the Yorke Peninsula and Adelaide Superbasin, along with their respective ages from radiocarbon dating. Using helium as a proxy, we provide insights into the source and migration of H₂ in South Australia. Through the use of a novel gas diffusion model (Cheng et al. 2023), we also investigate whether an H₂/He gas phase can be produced, critical for their concentration and formation as accessible resources.
How to cite: Milner, Z., Gluyas, J., McCaffrey, K., Holdsworth, B., Grocke, D., Hillegonds, D., Renshaw, T., Ballentine, C., and Ascough, P.: Origins of Helium and Hydrogen in South Australia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16617, https://doi.org/10.5194/egusphere-egu25-16617, 2025.
Soil gas analysis is among the commonly used methods in the early stages of natural hydrogen exploration. While most punctual [H2] measurements can provide information on spatial variation, observing temporal variation requires long-term monitoring. The University of Pau and Adour Countries developed a hydrogen-monitoring instrument called MONHyTOR. It is a passive instrument capable of acquiring [H2], temperature, and relative humidity data with up to 1-s sampling interval at 1-m depth for up to several months in full autonomy.
Preliminary field data from multiple sites show that (1) an “installation peak” is almost systematically observed after drilling; (2) measured [H2] is nil most of the times; (3) daily oscillations are present in some datasets; (4) small-amplitude isolated peaks are seemingly related to weather events such as storm and heavy rain. These observations raise the question regarding the influence of water saturation and pressure balance in the atmosphere-soil-instrument system. To understand them, experiments are carried out in a controlled environment using airtight container filled with coarse homogeneous sand with a given water saturation level, where hydrogen is introduced via low-pressure (mbar) injections of 5%-95% H2-N2 mixture. The aim of this study is to see how variations in the pressure balance impact [H2] measurements by MONHyTOR.
How to cite: Adjie, N., Bordes, C., Brito, D., Nasri, D., Normandin, E., and Voisin, C.: In-soil hydrogen concentration measurements using MONHyTOR., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16399, https://doi.org/10.5194/egusphere-egu25-16399, 2025.
There is a growing interest in natural hydrogen as a potential new source of energy with a negligible carbon-footprint, especially compared to all the other human-made hydrogen species. The white (or gold, natural, geologic or geogenic) and orange (or induced) hydrogen became the focus of intense research during the last decade.
From the energy industry point of view the fundamental question arises about natural hydrogen exploration, i.e. how different is it going to look compared to what we are used to in the hydrocarbon industry? After many decades of negligible consideration given to natural hydrogen as a subsurface target there are many papers and presentations published just in the last few years suggesting that many items in our collective industry and academic toolbox could be readily applied to natural hydrogen exploration. The consensus appears to be that three out four of the main petroleum systems elements the hydrocarbon industry tends to focus on in exploration projects are still going to play pivotal roles (i.e. migration, trapping and sealing) and it is only the generation/charge part which follows very different rules for hydrogen systems.
From an exploration point of view, several play types for natural hydrogen indeed appear to be very similar to what the oil and gas industry is used to. These include cases where there is a functioning trap, due to effective top seals. Numerous examples can be found in pre-salt traps worldwide where hydrogen has been documented for a long time as part of existing natural gas accumulations (e.g. Dnieper-Donets Basin, Ukraine, and Amadeus Basin, Australia). Another, but unusual trapping style has been documented in the first hydrogen field discovery in Mali where the top seal is a set of dolerite dykes. In these cases, one expects finite hydrogen resources to be in place and the exploration approach has indeed some resemblance to that of hydrocarbon prospecting.
Another group of natural hydrogen targets revolve around large mega-seeps (fairy circles) and geometrically smaller, but pronounced fault-controlled seepages to the surface. These hydrogen occurrences seemingly have no traps or seals and, therefore, do not find a proper analogue in oil and gas exploration workflows. Strictly speaking, these are not yet hydrogen plays as there are no commercial discoveries associated with them. The hydrogen fluxing along fault planes requires a fresh look at the exploitation of various fault architectures if shallow drilling would target conductive (or “leaky”) faults at shallow depth. In a more traditional exploration workflow, properly mapping and quantifying hydrogen fluxing along fault planes in shallow depth might be the first critical step before more conventional deeper targets (>1000 m) could be addressed. This set of plays promises that if these seeps really correspond to ongoing charge in a dynamic, truly renewable system in a steady-state process, tapping successfully into them would provide infinite resources via a low-flux hydrogen “farming” process.
It is quite likely that natural hydrogen exploration, if it becomes economically successful at one point, will look much more different than similar to hydrocarbon exploration.
How to cite: Tari, G.: Natural hydrogen exploration: it is quite different from looking for hydrocarbons, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16903, https://doi.org/10.5194/egusphere-egu25-16903, 2025.
Hydrothermal circulation is a fundamental Earth process that transfers elements and minerals from the crust and mantle to the oceans. This circulation commonly occurs along tectonic plate boundaries in the oceans, where heat sources are located at relatively shallow depths (~2–3 km). Cold seawater percolates downward, becomes heated, and is enriched with minerals from the host rock and magmatic volatiles. The resulting hot fluids (exceeding 300°C) rise buoyantly and are expelled into the ocean through chimney-like structures on the seafloor, commonly referred to as "Black Smokers." The ejected particles settle on the seafloor, forming rich mineral deposits known as "Seafloor Massive Sulfide" (SMS) deposits, making mid-ocean ridges highly attractive for meeting future mineral demands. Moreover, ridge settings hold significant potential for geothermal energy, white hydrogen production, and other valuable resources. However, harnessing these resources requires a thorough understanding of the complex hydrothermal systems to develop sustainable resource management strategies.
Hydrothermal venting sites are widespread along the mid-ocean ridge system, occurring at all spreading rates and across diverse geological settings. However, the mechanisms driving hydrothermal processes vary depending on factors such as the presence of magma bodies, permeable zones, tectonic activity, and temperature. At ultraslow spreading ridges, where spreading rates are less than 20 mm/yr—such as the Southwest Indian Ridge, Mohns Ridge, and Knipovich Ridge—tectonic processes dominate over magmatic activity, resulting in the exhumation of ultramafic material to the seafloor along large-scale detachment faults.
In this study, we developed two-dimensional, high-resolution velocity models through the crust and uppermost mantle of the Southwest Indian Ridge using wide-angle ocean-bottom seismic data. We present two ~150 km-long, high-resolution P-wave velocity models orthogonal to each other, running across and along the ridge axis at 64°30’E. We employed a state-of-the-art imaging technique known as full waveform inversion (FWI) using data from 32 ocean-bottom seismometers positioned along the two profiles. FWI is a data-fitting method in which the forward operator iteratively predicts the observed data by backpropagating the misfits to update the velocity model, thereby producing higher-resolution images of the subsurface.
Based on our high-resolution velocity models, we observe finer patterns of velocity anomalies compared to traveltime models, revealing more detailed variations in the degree of fluid-rock interaction. These interactions are influenced by the presence of faults and the extent of tectonic damage, aiding in the mapping of hydrothermal circulation. Additionally, our high-resolution images provide an improved understanding of the distribution of serpentinization and its correlation to mode of spreading. Overall, the high-resolution velocity models support the assessment of the feasibility of "Artificial Smoker," which replicates natural smokers, for the environmentally sustainable extraction of minerals, white hydrogen, and geothermal resources.
How to cite: Boddupalli, B., Arntsen, B., Minshull, T., Hokstad, K., Leroy, S., Johansen, S., Watremez, L., Corbalan, A., and Sørum, L.: Artificial Smoker: Geophysical characterization of an ultraslow ridge system for sustainable resource management, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11735, https://doi.org/10.5194/egusphere-egu25-11735, 2025.
Fluid temperatures in the Cenozoic basin fill of the North Alpine Foreland Basin (SE Germany) are locally significantly lower compared to adjacent areas of the basin. In the greater Rosenheim area, formation temperatures at a depth of 4000 mbs range ca. 80 K lower than expected with respect to a typical regional geothermal gradient of 28-30 K/km. Possible explanations for this so-called Wasserburg Trough anomaly include thermal blanketing by rapid deposition of cold sediments, effects of convective and advective heat transfer in Cenozoic sediments, long-term effects of glacial thermal overprint, increased gravity-driven recharge due to karstification in the underlying Upper Jurassic Limestone, and heat transfer towards the Tauern Window due to a thermal chimney effect. Recent studies on formation fluid ages in the Upper Jurassic Limestone, a prolific, hydrostatically pressured geothermal aquifer, show comparatively young fluid ages of <20 ka which points at local freshwater infiltration at greater depth. Freshwater influx may reduce heat flow, act as a conductive heat barrier and favour karstification. However, fluid overpressure in shales of the Cenozoic overburden does not allow for direct vertical fluid infiltration across the stratigraphic column.
We propose a tectonic control mechanism responsible for freshwater infiltration with the Bavarian Inntal Fault Zone, a normal fault system that was formed during indentation of the Southern Alps in Oligo-Miocene times, acting as a conduit fault. This fault zone is indicated by a steepening of W-E striking fold axes towards the Bavarian Inntal, and the existence of several, valley-parallel sets of NNW-SSE striking normal faults proving WSW-ENE directed extension. Total vertical displacement inferred from cross-sections and field data yield at ≥250 m which is probably sufficient to ensure hydraulic contact between sedimentary strata of the Alpine nappes and underlying Upper Jurassic Limestone in the deeper subsurface. Thereby, freshwater from the Alps could bypass the overpressure zone in the Bavarian Inntal and infiltrate into the Upper Jurassic Limestone aquifer of the foreland basin.
How to cite: Duschl, F., Aconcha, E., Ettenhuber, R., Tomsu, C., Einsiedl, F., and Drews, M.: Fault-controlled groundwater recharge from Alpine units into Upper Jurassic Limestone of the North Alpine Foreland Basin (SE Germany), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12845, https://doi.org/10.5194/egusphere-egu25-12845, 2025.
Orogenic geothermal systems develop when meteoric water infiltrates the subsurface at high elevations, heats up along a deep circulation path due to the background geothermal gradient and eventually emerges at the surface in low topographic sites as localized hot springs. Such systems depend on permeable fault geometries; however, in orogenic settings fluid-discharge zones may additionally be controlled by the configuration of topography, nappe geometry, fault patterns and unconsolidated deposits that can conceal the bedrock structure. Hence, it is crucial to study local hot springs in the context of fault structures related to regional tectonics in order to predict the locations of blind geothermal systems. The Rhône Valley is a favourable site for such a study, as it shows the highest seismic activity in Switzerland and hosts several clusters of hot springs aligned along the regional Rhône-Simplon fault system.
Here, we combine data sets on geodynamics such as geodesy of recent crustal movements, regional recent stress fields, relocated hypocenters and focal mechanisms as well as structural field data to interpret the hot spring occurrences in the context of regional geodynamics. Our data suggest the presence of three adjacent structural domains: (1) A domain on the NW flank of the Rhône fault characterized by a NW–SE oriented maximum principal stress, high seismicity, and a pervasive network of strike- slip dominated faults; (2) a zone encompassing the Rhône Valley floor with transtensive, dilatant zones along strike-slip fault segments; and (3) a zone on the southern flank of the valley floor subjected to a recent NE–SW extension expressed by dominantly normal to transtensional faulting focal mechanisms. This southern domain constitutes the SW-extruding hanging wall block of the Simplon low-angle normal fault. The block is bounded by two crustal scale strike-slip faults, the dextral Rhône strike-slip fault in the NW and the sinistral Ospizio Sottile line in the SE.
In summary, our study highlights the importance of the large-scale tectonic setting for understanding and exploring fault controlled and hence, strongly localized geothermal resources in orogenic settings.
How to cite: Schmid, T., Herwegh, M., Berger, A., Diehl, T., Madritsch, H., van den Heuvel, D., Wanner, C., and Diamond, L.: Fault-hosted hot springs of the Rhône Valley in the context of varying regional-scale neotectonics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10972, https://doi.org/10.5194/egusphere-egu25-10972, 2025.
Eastern China (EC) is located in the eastern margin of the Eurasian Plate and has been influenced by the subduction of the Izanagi and Pacific Plate since the Late Mesozoic, resulting in a large amount of tectonic-magmatic activities. After the India–Eurasia convergence, the topography of continental China changed from high-east-low-west to high-west-low-east. At present, the Bohai Bay Basin in EC mainly forms sedimentary basin-type geothermal system, and deep circulation-type geothermal systems mainly occur in southeast coastal China, with thermal springs widely distributed. In the northeastern China, Holocene volcanoes such as Changbaishan Volcano have been formed, together with many thermal springs exposed.
The genesis of shallow thermal anomalies is closely correlated with the thermal-rheological structure of the lithosphere. In this study, we comparatively analyzed the lithospheric thermal-rheological structures of different tectonic units in EC, such as the Bohai Bay Basin, the southeast coastal China, and the Changbaishan Volcano field. We revealed that under the influence of the Pacific tectonic domain, the lithospheric thermal structures differed significantly, and the temperatures at the same depth from high to low are the Changbaishan Volcano field, the Bohai Bay Basin and the southeast coastal China. The rheological structures are significantly weakened in the middle and lower crust in the presence of an intracrustal heat source. The shallow thermal anomalies in the three tectonic units are similar in that the reservoir temperatures are mainly in the range of 100-150°C, and the water sources are all meteoric water. The difference between shallow thermal anomalies corresponds to their lithospheric thermal-rheological structures. The geothermal systems in the sedimentary basin of the Bohai Bay Basin are characterized by wells with a geothermal reservoir depth of 3-5 km. The deep-circulation hydrothermal systems in southeast coastal China are characterized by springs with a circulation depth of 4-7 km, and the hydrothermal systems in the Changbaishan Volcano field are characterized by springs with a circulation depth of 4-5 km. The deep thermal-rheological structure influences the behavioral characterization of shallow thermal anomalies with respect to heat-accumulation patterns. When brittle-ductile transition depth greater than the circulation depth, magma chamber (or partial melting body) and fluid circulation systems are relatively independent, and mass transfer from the magma chamber to the geothermal system may not happen.
How to cite: Gan, H., Wang, X., Wang, G., Zhang, W., Xing, L., and Zhang, Y.: Lithospheric thermal-rheological structure and shallow thermal response in eastern China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3367, https://doi.org/10.5194/egusphere-egu25-3367, 2025.
The UAE government is actively exploring the use of Hormuz salt domes for large-scale hydrogen and hydrocarbon storage, aligning with its strategic goals for clean energy transition and decarbonization. A comprehensive understanding of the geometry, kinematics, and halokinetic phases of these Infra-Cambrian Hormuz salt structures is crucial to achieving this vision. This study focuses on the Jebel Al Dhanna salt dome, the only exposed salt dome in onshore Abu Dhabi. Utilizing three 3D seismic surveys and data from four boreholes, the research analyzes its morphology and evolution. The Jebel Al Dhanna salt dome exhibits an elliptical structure elongated in the N-S direction, with dimensions ranging from 2 to 2.8 km (E-W) and 3.2 to 4.2 km (N-S). The dome features irregular crests, steeply dipping flanks, and a series of hills rising approximately 110 m above sea level. Surrounding the dome is a pronounced rim syncline, resulting from the upward evacuation of Hormuz salt through the thick Phanerozoic stratigraphic succession, creating a discordant relationship with the dome structure. Salt withdrawal at Jebel Al Dhanna likely initiated in the Late Cretaceous, driven by the reactivation of inherited basement faults associated with ophiolite obduction onto the Arabian foreland. Halokinetic activity persisted through the Oligocene-Miocene, coinciding with the continent-continent collision of Central Iran and the Arabian Plate. The presence of tilted Upper Miocene and Quaternary strata around and within the Jebel Al Dhanna salt dome underscores continued salt evacuation to the present day. This research highlights the importance of salt tectonics for energy resource storage and provides valuable insights into fault-salt interactions, with significant implications for hydrocarbon exploration, energy security, and the UAE’s decarbonization initiatives.
How to cite: Ali, M., Ali, M., and Alshehhi, H.: Geometry and Kinematics of the Hormuz Salt in the United Arab Emirates: The Jebel Al Dhanna Salt Dome, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3033, https://doi.org/10.5194/egusphere-egu25-3033, 2025.
Thick salt deposits occur in a wide range of sedimentary basins and orogens. They are associated with large and geometrically complex structures due to the inherent ability of salt to flow as a viscous fluid. Salt basins form major hydrocarbon provinces and are increasingly targeted for CO2/H2 storage and geothermal energy due to the unique physical properties of salt, its low viscosity, high thermal conductivity and impermeability. Despite considerable advances in understanding salt basins and salt tectonics, there is still a significant knowledge gap on the internal geometry of salt structures. We apply a novel, very-high resolution (20x50m)2D numerical modelling approach to simulate salt diapirism and minibasin formation for heterogenous, layered salt sequences. We test the effects of varying i) viscosity, ii) density, iii) thickness, and iv) stratigraphic arrangement of intra-salt layers on the kinematics, and the internal and external geometries of deformed salt bodies by using scaled material properties to simulate: i) weak pure halite, ii) less-weak impure halite, ii) strong and dense anhydrite-rich layers, and iv) very-weak K-Mg salts.
Our results show that salt sequences including an alternation of weak and less-weak layers with different viscosity and density produce major intra-salt strain partition and complexity characterized by highly convoluted folding, horizontal and vertical shearing, and preferential flow of the weaker, less-dense salt (pure halite) into the core of diapirs. The less-weak layers can eventually flow into the diapir crest but are generally disrupted by flow of the underlying weak layers and positioned towards the diapirs’ flanks where they become overturned. The most complex and convolute intra-salt geometries occur around the diapirs’ flanks when there is an abrupt internal shift of minibasin depocentres. Recumbent intra-salt folds are also common and associated with the development of secondary minibasins by diapir-fall. For models that include strong anhydrite-rich layers, there is a general decrease in the magnitude and complexity of diapirism, with these layers being passively folded by flow of the underlying weak salt and displaying only moderate to negligible flow onto diapirs and vertical stretching. These stronger layers become trapped underneath the base of diapirs and their associated minibasins where they typically form short-wavelength folds. For models that include very-weak and light K-Mg salt layers, there is an increase in rate of diapirism with rapid vertical shearing and stretching of the weak layers along the diapir’s flanks and sub-horizontal flow and recumbent folds along their crests. Varying the position of both very-weak and strong layers generates very contrasting internal and external diapir geometries. These results can aid in the characterization of the internal structures of deformed, diapiric salt bodies, which is critical for the use of salt structures in the context of energy transition. They provide important insights that can help the design of salt caverns for H2/CH4 storage by identifying areas with broadly homogenous halite-rich salt, 2) avoiding drilling through sheared and highly-stressed and strained intra-salt heterogeneities, and 3) constraining minibasin architecture and evolution, improving the understanding of the distribution and geometry of CO2 reservoirs.
How to cite: Pichel, L., Huismans, R., Theunissen, T., Delahaye, S., Pichat, A., Callot, J.-P., and Celini, N.: The role of intra-salt heterogeneity on the internal and external geometry of salt bodies – a numerical modelling approach with applications for geo-storage, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7103, https://doi.org/10.5194/egusphere-egu25-7103, 2025.
The architecture of the lithosphere is shaped by diverse geodynamic processes, including the presence of metasomatized mantle volumes, lithospheric thickness transitions, crustal- and mantle-scale fluid migration pathways, and the influence of plumes and subducting slabs. These features are preserved in the physical and chemical structures of the lithospheric mantle and sub-lithospheric upper mantle, providing critical insights into mineral systems and resource prospectivity.
To address these complexities within the Canadian lithosphere and mantle, we apply a probabilistic inversion framework, LitMod, which integrates geological constraints with multiple geophysical techniques and incorporates a priori geochemical information. This unified approach enables the resolution of key lithospheric features, distinguishing between compositional (e.g., metasomatism) and thermal anomalies.
We present results from the first application of LitMod to Canada, highlighting its capability to map essential geophysical structures and surfaces. Validation of the model’s predictions using independent geochemical datasets underscores the robustness and reliability of our results. Beyond advancing mineral prospectivity, this work contributes to broader geoscientific applications, including refining Glacial Isostatic Adjustment (GIA) models, improving Carbon Capture, Utilization, and Storage (CCUS) strategies, and enhancing seismic hazard assessments.
How to cite: Dave, R., Schaeffer, A., Darbyshire, F., and Afonso, J. C.: Resolving Whole-Lithospheric Architecture for Mineral Prospectivity and Beyond: A Probabilistic Inversion Approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13046, https://doi.org/10.5194/egusphere-egu25-13046, 2025.
Despite abundant empirical evidence, the details of coupled deformation and mass transfer processes within a framework of the crustal architecture of ancient orogens remains enigmatic. Geophysical imaging of the Larder Lake-Cadillac deformation zone, a well-endowed crustal-scale fault system in the Superior Province of the Canadian Shield, characterises the crustal architecture and fault geometry of the system through the lower crust. By comparing the geophysically determined structure of the Larder Lake-Cadillac deformation zone to stress changes induced by Archean (peak orogeny) rupture of the fault system, we show domains of earthquake-triggered deformation coincide with the geophysically imaged low resistivity zones. These low resistivity zones likely formed due to mineral bearing fluid migration from underlying fertile source zones to downstream (shallower) crustal reservoirs and, ultimately, near surface traps. The multi-disciplinary approach identifies the syntectonic mass-transfer processes and fluid pathways, providing an interpretive framework for unraveling the geophysical manifestation of the deformation controlled processes responsible for upflow of metalliferous fluids that may result in ore deposit formation in collisional orogens.
How to cite: Hill, G., Friemann, B., Roots, E., Wannamaker, P., Maris, V., Haugaard, R., Kamm, J., Kovacikova, S., Klanica, R., Calvert, A., Craven, J., and Smith, R.: Deformation controlled fluid mass-transfer processes in ancient orogens , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7428, https://doi.org/10.5194/egusphere-egu25-7428, 2025.
With the increasing demand for alternative energy sources, natural hydrogen is gaining attention for commercial exploitation. Naturally accumulated hydrogen is only utilized today at the field of Bourakébougou, Mali, highlighting major knowledge gaps in the behaviour of hydrogen systems and in the related exploration-production workflows. Circular depressions called “fairy circles” represent a surface manifestation of hydrogen seeps that commonly occur in continental cratons and are formed relatively quickly (few years). Apart from the topographic imprint of these ~100 m to 2 km diameter depressions, a major signature of the structures is a vegetation anomaly; characterized by a zone of dying vegetation inside the circle, and a ring of healthy, enriched vegetation in their surroundings. Although the connection of surface H2 seeps to deep-seated H2 sources has been implied in several case studies, the exact mechanism of fairy circle formation is still largely unknown, together with the underlying generation, migration, and accumulation processes of H2.
Satellite images are widely used for the mapping of fairy circles, but these observations are mainly restricted to passive satellite sensors without monitoring any temporal changes of the structures. In this study we used Synthetic Aperture Radar (SAR) images acquired by the European Space Agency’s Sentinel-1 satellites to monitor the evolution of fairy circles in terms of morphological and vegetational changes in two demonstration areas: in the Sao Francisco Basin of Brazil, and in the Lublin Basin of SE Poland. In both cases, the duration of the monitoring was ~5 years, with a temporal resolution of ~1 month. We applied the Interferometric Synthetic Aperture Radar (InSAR) method to map ground motions associated with the potentially active surface deformation of fairy circles. We extended the ground motion time series with SAR backscatter analysis to identify changes in the strength of the backscattered signal through time. The aim of the backscatter analysis was to identify any rapid changes associated with the loss/increase of vegetation linked to H2 degassing. Results show significant ground motion and vegetation anomalies associated with fairy circles in the Sao Francisco Basin (Brazil). Results are not that evident in the Polish area, mostly due to its poorer suitability for InSAR and backscatter analysis (generally lower coherence areas and presence of agricultural and other artificial activities overprinting natural variations). The SAR-based observations were compared with geochemical measurements for monitoring H2 emissions in the soil in both areas, to better understand the potential link between H2 degassing and morphological and/or vegetation changes. The detailed understanding of subsurface processes responsible for the detected anomalies and H2 seeping cannot be inferred, but important constraints on fairy circle formation are achieved. This study demonstrates the applicability and limitations of InSAR and backscatter analysis for the mapping of actively changing fairy circles over two different areas, with important implications of the methodology for further case studies worldwide and constraints on natural hydrogen systems in general.
How to cite: Békési, E., Szárnya, C., Prinzhofer, A., Twaróg, A., Porkoláb, K., and Tari, G.: Exploration of “fairy circles” associated with natural hydrogen seepages with synthetic aperture radar interferometry and backscatter analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8374, https://doi.org/10.5194/egusphere-egu25-8374, 2025.
The discovery and exploitation of the first natural (white) hydrogen reservoir in Mali has stimulated global interest in this zero-emission energy resource and carrier. Current research worldwide aims to identify its generation sources, occurrence potential, and extraction feasibility. Tools and methods normally used in hydrocarbon exploration are being adapted for this purpose. One such method is the molecular composition analysis of soil gases, a surface geochemical technique. These methods involve detecting and analyzing trace amounts of light hydrocarbons migrating from subsurface accumulations to the surface. Surface geochemical studies have been conducted across all petroleum basins in Poland. In addition to hydrocarbons, other gases, including hydrogen, were routinely analyzed in many soil gas samples. However, hydrogen played a marginal role in interpreting results aimed at identifying subsurface hydrocarbon accumulations. Large datasets containing hydrogen concentrations in soil gases, recorded over the past 35 years across Poland, remain largely unanalyzed and uninterpreted. One such dataset pertains to the Świdwin-Sławoborze area in Western Pomerania, northern Poland. In 1996, 478 soil gas samples were collected from a depth of 1.2 meters in this region. These samples were analyzed chromatographically for hydrocarbons and non-hydrocarbon gases, including hydrogen.
Molecular composition analysis revealed hydrogen in 85% of the samples, with a maximum concentration of 940 ppm. The mean hydrogen concentration (38 ppm) is five times greater than the median (8 ppm), indicating the presence of anomalous values. Hydrogen concentrations exceeding 40 ppm were partly recorded above an oil deposit located in Zechstein Main Dolomite formations. Elevated hydrogen concentrations in these samples correlate with increased levels of C2-C4 alkanes. Additionally, high hydrogen concentrations were observed above tectonic structures, which may indicate hydrogen migration from deeper horizons.
Reanalyzing and reinterpreting archival geochemical data with a focus on hydrogen concentration variations enables the identification of potential hydrogen migration and leakage zones at the surface. Integrating archived geochemical data with terrain morphology (e.g., potential "fairy circle" structures), geological formations, and the distribution of other resources highlights promising anomalous areas. These zones provide a valuable framework for investigating hydrogen origins and migration patterns within the Polish Zechstein Basin, part of the Central European Permian Basin.
The research project was supported by program “Excellence initiative – research university” IDUB for the AGH University of Krakow (project number 6237).
How to cite: Twaróg, A. and Sechman, H.: Surface geochemistry: from oil and gas exploration to natural hydrogen seeps, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20357, https://doi.org/10.5194/egusphere-egu25-20357, 2025.
One of the main challenges in studying a natural hydrogen system is that ultramafic rocks - potential source rock for hydrogen generation by serpentinization - are often buried deep within the subsurface. The serpentinites of the metamorphic Münchberg Massif, obducted during the Variscian orogeny in Devonian times, offer a unique window into deep crustal and upper mantle processes. As part of an integrated study, we have acquired airborne magnetic and strapdown gravity data, seismic reflection profiles, as well as detailed petrological and geochemical analysis. This approach enables a multi-scale interpretation of the tectonic evolution, serpentinization processes, and associated fluid-rock interactions, mineralogical transformations, and implications for paleo-natural hydrogen generation in the Münchberg Massif.
Serpentinite rock bodies are exposed at multiple outcrops across the Münchberg Massif. Geochemical analyses of major and rare earth elements indicate that serpentinites from both the Peterleinstein (west) and the Zell region (south) share a similar protolith of harzburgitic composition. However, different serpentine minerals dominate at the different locations. The Zell serpentinites, predominantly antigorite, appear to have undergone serpentinization at greater depths and higher temperatures than the Peterleinstein serpentinites, which are dominated by lizardite. Conversely, Peterleinstein demonstrates a higher degree of serpentinization, likely indicating increased fluid availability during the process. The sequence of events during serpentinization is evident in spatially resolved analyses of different generations of serpentine minerals in thin sections using microscopic and Raman micro-spectroscopic analyses.
Initial interpretation of the airborne magnetic data reveals a series of positive high-frequency anomalies with amplitudes of up to ~160 nT, associated with magnetite enrichment, a by-product of serpentinization and hydrogen generation across the Münchberg Massif. Petrological analyses confirm the presence of magnetite-bearing serpentinites. However, preliminary on-site magnetic susceptibility measurements do not resolve differences in the degree of serpentinization. Combined petrophysical, seismic, gravity and magnetic interpretation and modeling will constrain the extent of serpentinization in the subsurface and evaluate the role of major faults as fluid conduits during serpentinization.
How to cite: Klitzke, P., Bagge, M., Hasch, M., Koglin, N., Ruppel, A., Fazlikhani, H., Johann, F., Goldmann, J.-F., Löwer, A., and Ostertag-Henning, C.: Petrological and geophysical characterization of a paleo natural hydrogen kitchen – serpentinites of the Münchberg Massif, Germany, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11413, https://doi.org/10.5194/egusphere-egu25-11413, 2025.
The growing global demand for metal resources requires new discoveries of high-grade ore deposits. Known sediment-hosted clastic-dominated base metal deposits are found in failed continental rifts and the passive margins of successful rifts. Recent studies indicate that the majority of these Zn-Pb deposits are located near steps in lithospheric thickness (e.g., Hoggard et al., 2020), but a potential causal link between ore formation and craton edges remains elusive. However, numerical models have shown that a craton edge close enough to an incipient rift controls the direction of asymmetry of the rift system (Raghuram et al., 2023) and that asymmetric rifts are more favorable to deposit formation (Glerum et al., 2024). Understanding the large-scale controls of cratons on rift-related mineralizing processes, occurring on much smaller spatial and temporal scales, can thus help identify new areas for exploration.
To this end, we use the geodynamic code ASPECT (Kronbichler et al., 2012; Heister et al., 2017) coupled to the landscape evolution model FastScape (Braun and Willett, 2013; Neuharth et al., 2022) to model 2D rift systems from inception to break-up in the presence of a craton. We investigate the relationship between craton distance and favorable conditions for ore formation, i.e., those conditions where potential source rock, host rock, and fluid pathways co-occur. Our results show that cratons have a negative effect on ore formation in narrow asymmetric rifts, but a positive effect in wide rifts.
In a second step, we further investigate the hydrothermal ore-forming mechanisms by using potentially favorable geodynamic configurations from the ASPECT simulations as input for fluid flow modelling with CSMP++ (Weis et al., 2014; Rodríguez et al., 2021). This input comprises basin geometry, temperature, boundary heat flow and a permeability structure dependent on strain and strain rate. With a temperature- and salinity-dependent proxy of metal solubility in the basinal brines, we track the leaching, transport, and precipitation of metals. This cross-scale workflow allows us to identify those rifting scenarios with the highest metal enrichment potential.
References:
Braun and Willett, 2013. Geomorphology 180–181: 170–79. DOI: 10.1016/j.geomorph.2012.10.008.
Glerum et al., 2024. Solid Earth 15: 921-944. DOI: 10.5194/se-15-921-2024.
Heister et al., 2017. Geophys. J. Int. 210 (2): 833–51. DOI: 10.1093/gji/ggx195.
Hoggard et al., 2020. Nat. Geosci. 13 (7): 504–10. DOI: 10.1038/s41561-020-0593-2.
Kronbichler et al., 2012. Geophys. J. Int. 191 (1): 12–29. DOI: 10.1111/j.1365-246X.2012.05609.x.
Neuharth et al., 2022. Tectonics 41 (3): e2021TC007166. DOI: 10.1029/2021TC007166.
Raghuram et al., 2023. Geology 51:1077–1082. DOI: 10.1130/G51370.1.
Rodríguez et al., 2021. GCubed 22 (6). DOI: 10.1029/2020GC009453.
Weis et al., 2014. Geofluids 14, 347-371. DOI: 10.1111/gfl.12080.
How to cite: Glerum, A., Brune, S., Weis, P., Magnall, J. M., and Gleeson, S. A.: The enigmatic role of cratons in Zn-Pb deposit formation during continental rifting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3694, https://doi.org/10.5194/egusphere-egu25-3694, 2025.
The structure, thickness, lateral heterogeneity, and temporal evolution of the lithosphere significantly influence the distribution of kimberlites, carbonatites, and sediment-hosted mineral deposits, including rare earth elements (REE) and critical metals (e.g., Nb and Ti) that are essential for advancing the transition to green energy.
Seismic data provide critical information on the thermal structure of the lithosphere and underlying mantle. However, seismic tomographic models are inherently non-unique. This can be remedied, to a large extent, by thermodynamic inversions, which utilize computational petrology and offer an effective approach to connecting seismic observations to the thermal structure of the lithosphere and mantle.
We present a new model of the African lithosphere’s thickness and thermal structure, derived from state-of-the-art sampling with seismic surface wave data. The model incorporates both Rayleigh and Love waves, to account and correct for seismic anisotropy of the elastic properties. Rayleigh and Love wave data in the 20–300 s range are inverted, on 1°×1° grids, for the upper-mantle temperature and lithospheric thickness, from which upper-mantle density and seismic velocities are calculated, with attenuation corrections. Radial anisotropy, seismic velocities in the crust, transition zone and uppermost lower mantle, and crustal density are also inversion parameters, the latter constrained primarily by the surface elevation. The resulting model reveals distinct regional variations in the lithospheric thickness that reveal deep lithospheric expressions of known crustal geology. Thick lithosphere (>220 km) is found beneath large parts of the West African Craton, Congo Craton, and Zimbabwe Craton. Thin lithosphere (<70 km) is predominantly observed along the East African Rift.
We analyse the new lithosphere model jointly with recent datasets of the distribution of different types of igneous rocks across the continent. These include kimberlites, which were emplaced at locations with thick cratonic lithosphere; basalts, which are emplaced at locations with thin lithosphere; and carbonatites that are commonly found on intermediate-thickness lithosphere (Gibson et al. 2024). Statistics analysis of the locations of these rock samples shows that kimberlites mostly are found within cratons, with some notable exceptions. Most Neogene basalts are in the East African Rift Zone, with a 50–100 km lithosphere. Carbonatite complexes and their associated REE deposits, are typically observed in clusters in the transition regions from cratonic to non-cratonic lithosphere.
This new lithospheric thickness and temperature model enhances our understanding of the dynamics and evolution of the African lithosphere. Furthermore, it provides valuable insights into the processes that govern the generation and spatial distribution of rocks of different types and the associated primary critical mineral deposits.
Gibson, S., McKenzie, D. & Lebedev, S. (2024). The distribution and generation of carbonatites. Geology 52, 667–671.
How to cite: Sui, S., Xu, Y., Lebedev, S., Bowman, E., Fullea, J., and Gibson, S.: A new model for the thickness and thermal structure of the African lithosphere: implications for the distributions of kimberlites, carbonatites and critical mineral deposits, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9976, https://doi.org/10.5194/egusphere-egu25-9976, 2025.
The concentration of critical minerals and metals occurs within 200 km of the transition between thick and thin lithosphere or cratonic edges1. These cratons are regions comprising thicker lithosphere, which has remained stable for billions of years. The critical minerals are initially sourced from the mantle by a range of deep Earth geophysical, geochemical, and tectonic processes, to be further concentrated near the Earth’s surface via hydrothermal processes. These deep Earth processes involving mantle melting also play a crucial role in cratonic stability, and therefore, the improved understanding of these will help unravel intricate connections between craton dynamics and ore deposit formations.
The formation and evolution of cratons play a crucial role in the development of those critical minerals. Cratons formed under different scenarios have different internal structures, which, in turn, influence subsequent tectonics and melting scenarios. One of the challenges is how to deal with the vastly different time and length scales in these processes (e.g. between mantle dynamics and melt processes). Preliminary results regarding the best way to capture the processes of craton formation and stability under different geologic scenarios using numerical models developed with the ASPECT geodynamical software tool (REF) will be presented.
References:
- Hoggard, Mark J., Karol Czarnota, Fred D. Richards, David L. Huston, A. Lynton Jaques, and Sia Ghelichkhan. “Global Distribution of Sediment-Hosted Metals Controlled by Craton Edge Stability.” Nature Geoscience 13, no. 7 (July 2020):504–10.https://doi.org/10.1038/s41561-020-0593-2
How to cite: Chakraborty, A., van Hunen, J., Valentine, A., and Roy, P.: Investigating Craton Dynamics and Ore Deposit Formation , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8635, https://doi.org/10.5194/egusphere-egu25-8635, 2025.
Sedimentary and crustal thickness constraints are crucial for refining dynamic topographic measurements and evaluating geothermal energy prospectivity. Continental sedimentary and crustal thickness measurements are constrained in this ongoing global study. Here, we present the updated methodology and results. Total sedimentary thickness is accurately constrained via a combination of well data and controlled-source seismic experiments. A minimum curvature gridding algorithm is used to interpolate between sedimentary thickness data points. Crustal thickness, defined as the vertical depth from the sediment-basement interface to the Moho, is derived from the updated sedimentary thickness grid and recently published studies which exploit controlled- and passive-source seismic data to constrain depth to Moho. A grid resolution of 0.03 degrees is found to be essential for capturing fine-scale lateral variations in sedimentary thickness. Resulting sedimentary and crustal thickness estimates are used to improve continental residual elevation constraints, a proxy for dynamic topography. Residual elevation is quantified by isolating and removing isostatic signals arising from sediment loading and crustal heterogeneity, revealing the magnitude of mantle-induced vertical motion at the surface. Our estimates additionally improve predictions of surface heat flow and geothermal gradients, directly informing geothermal energy assessments. Collectively, these datasets can be used to advance our understanding of mantle-lithosphere interactions and sustainable energy resources.
How to cite: Slay, P., Holdt, M., and White, N.: Improved global sedimentary and crustal thickness constraints: Implications for dynamic topography and geothermal resource assessment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19524, https://doi.org/10.5194/egusphere-egu25-19524, 2025.
Scaling up geothermal from a niche industry to a viable, global industry is important for all our collective decarbonization efforts. Here we explore the distribution of geothermal projects globally to understand where projects have been positioned to date. As a result of this global analysis, we recommend that future geothermal exploration and development be conducted using a Linnean-style classification system for geothermal entities. Hierarchical thinking and the pre-discovery exploration triangle will provide the technique for gaining the ‘big picture’ context about the location of the optimal geothermal plays and prospects. It is further argued that the engineering approach used to complete a geothermal project significantly impacts the economics of the project, and that engineering should not be confused with play type, which at the highest level is either hydrothermal or petrothermal.
In this study we explore the distribution of Natural hydrothermal systems (NHS), Open loop Geothermal Systems (generically known EGS), and Closed Loop geothermal systems (generically known CLG or AGS). Using the geodynamic model of Hasterock et al., (2022) our findings include an observation that there is little or no coherence to geothermal exploration to date. CLG/Closed Loop: Volcanic Arc systems (44%) EGS/Open Loop: Orogenic Belt systems (45%). Natural Hydrothermal: Volcanics Arc systems (51%). Our analysis is the first coherent global study of the geodynamic domain of geothermal projects. We observe that a better understanding of the internal variation within geodynamic domains and refined geodynamic models (paleo and present day) are necessary to improve the success of geothermal exploration. Furthermore, we find that identifying present day stress-state is important when planning wells and executing geothermal projects, and that higher resolution lithospheric models are needed to help understand the petrothermal and hydrothermal systems. Finally, further R&D is needed to help unlock geothermal exploration and drilling across the most prolific geodynamic settings.
How to cite: Ball, P., Banks, G., Montgomery, M., Afonso, J. C., and Stroganov, V.: The importance of geodynamic settings and exploring for geothermal energy , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2903, https://doi.org/10.5194/egusphere-egu25-2903, 2025.
Using the geodynamic model of Hasterock et al., (2022), Ball et al., (2025) observed that existing natural hydrothermal systems and associated geothermal power plants are distributed across 12 different geodynamic settings. We observe based on the Hasterock classification only 18 out of 489 power plants (3.6%) are located within Back Arc Basins (BABs). This may lead to the conclusion that, at a global scale, BABs are not highly prospective. However, a much more detailed observation of the various tectonic settings at specific locations shows some incongruencies in the Hasterock geodynamic classification. For example, key power plants such as Larderello, Italy are in fact located in a BAB setting, not in a Volcanic Arc setting (Ball, 2022). At a local scale it is important to refine global models to account for younger deformation that overprint previous tectonic events.
With Larderello as an analogue, we explore the idea that other BABs could be increasingly perspective for geothermal resources if the geodynamic setting is correctly assessed, and the local tectonics is understood. BABs, are extensional basins, typically formed behind active or inactive volcanic arc on the overriding plates. BABs, are known to be associated with high heat flow, due to the interplay of mantle dynamics, slab processes and crustal extension. In this work, we review the first-order controls on heat flow within the Aegean and Tyrrhenian back arc systems. We point to the comprehension of how factors like rapid localization of thinning in the crust and lithospheric mantle impacts heat flow, coupled with sedimentary cover. In detail, we evaluate the role of accessory parameters, like hydrothermal fluids ascending along faults and fractures, the role of intrusions due to patrial melting in response to rapid thinning in the crust and mantle, localizing high heat flows spots and causing significant thermal heterogeneities.
The dynamic settings of BABs could offer intriguing geothermal opportunities, but their structural, magmatic and hydrological histories need to be better understood. BAB’s like the Tyrrhenian and Aegean may provide exceptional opportunities for power generation. Exploration in this geodynamic setting could benefit by using the exploration triangle, which organizes the geological assessment into a hierarchical sequence of tasks. This play-based approach focusses assessment from the geodynamic setting and can be applied at the geothermal systems, and reservoirs scale. Successful application could greatly assist in identifying future prospects for geothermal development, successfully exploiting BAB’s for power generation.
How to cite: Nuhu, A.-N., Decarlis, A., Ceriani, A., and Ball, P.: Geodynamic Heterogeneity in Back Arc Basins: Implications for Heat Flow Distribution and Geothermal Energy Potential., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14781, https://doi.org/10.5194/egusphere-egu25-14781, 2025.
The Upper Rhine Graben (URG), situated along the border of France and Germany, is part of the intraplate European Cenozoic Rift System. The graben is widely recognized for its abundant geothermal resources, making it a key region for energy transition initiatives. However, the characterization of the URG’s geothermal potential remains poorly constrained due to its highly variable hydrothermal conditions and large observational gaps. Previous studies on fault criticality have often overlooked the role of historical plate movements, oversimplifying the intricate interactions that govern the thermal and structural evolution of the URG over the past ~40 million years.
Using the numerical geodynamic code ASPECT coupled with the landscape evolution code FastScape, we simulate the lithospheric-scale development of fault networks within the URG under geodynamically realistic stress and strain conditions. Our models incorporate various forms of structural and rheological heterogeneities inherited from the earlier Variscan Orogeny, along with a two-stage Cenozoic kinematic history involving rift-orthogonal extension followed by sinistral strike-slip. Preliminary results show the first-order impact of structural inheritance and divergence obliquity on strain localization, which shape the orientation, spacing, and strain rate of the resulting fault network. These results will lay the groundwork for subsequent basin-wide modelling with the thermo-hydro-mechanical code GOLEM, coupling geodynamically controlled basin development with heat and fluid flow simulations that involve shorter-term rock and fracture mechanics. Throughout all modelling stages, we compare our models with available geological and geophysical observations.
How to cite: Yu, A. J., Brune, S., Bott, J., Glerum, A. C., and Scheck-Wenderoth, M.: Geodynamic controls on the geothermal potential in the Upper Rhine Graben, France-Germany: a multi-scale numerical modelling approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4193, https://doi.org/10.5194/egusphere-egu25-4193, 2025.
The Canary Islands stand out as a prime region within Spanish territory with significant potential for harnessing high enthalpy geothermal resources due to their active volcanic activity. La Palma, one of the youngest islands in the archipelago, has witnessed at least seven volcanic eruptions over the past 500 years, with the most recent one occurring in 2021. Despite these compelling signs, the development of high enthalpy geothermal power plants has not been pursued on the island, mainly because of the financial risk involved in such project and the lack of detailed geophysical data that can support the correct characterization of the geothermal potential on the island. Accordingly, a data-integrative approach that aids the characterization of potential geothermal sites will reduce such uncertainties, supporting the drilling planning phase of the project. Since the last eruption in 2021, several new geophysical experiments and projects have been undertaken within La Palma Island, aiming to understand the present-day configuration of the subsurface. In this study, we integrate the newly geophysical data in order to build a 3D thermal model that is consistent with the geological structure of the island. This research is funded by the Spanish Government projects PRX23/00106 and PID2022-139943NB-I00
How to cite: Jimenez-Munt, I., Gomez-Garcia, A. M., Cacace, M., Scheck-Wenderoth, M., Bott, J., Negredo, A. M., Ledo, J., Martin-Hernández, F., and Bejerano, A.: Thermal state of La Palma (Canary Islands) from a data-integrative approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9147, https://doi.org/10.5194/egusphere-egu25-9147, 2025.
The Tertiary Piedmont Basin (TPB) in northwest Italy is a wedge-top basin developed during Eocene—Pliocene times in the Alps-Apennines tectonic junction. It accommodates, on average, 3 km of clastic sedimentary units with significant lateral facies variations, and several basin-scale unconformities tectonically-controlled. The basin experienced deformation under markedly different tectonic regimes, developing long-lived kilometric structures that affected both the sedimentary successions, and the underlying metamorphic rocks of the Ligurian Alps. The presence of several thermal springs, relatively high surface heat-flow, and locally high geothermal gradient in the TPB, suggests a deep groundwater circulation and heating most likely in a reservoir hosted within the Alpine metamorphic rocks, i.e., the basement.
The geothermal system of the basin is not fully understood, since it still lacks a comprehensive and detailed geological/geophysical model of the basin-basement present-day structure. Aiming to fulfill this gap, this study shows structural analyses performed in the TPB and its Alpine basement at different scales through field-based characterizations, Digital Outcrop Model-based fracture mapping, and seismic interpretation. The integration of these structural results coupled with the spatial distribution of the basement and overlying sedimentary cover, enables a preliminary evaluation of potential reservoir or seal units in the geothermal system. These outcomes provide an adequate conceptual model to better understand the geothermal systems of the TPB, and other systems in analogue settings, having geodynamic peculiarities like slab switches or brake-off.
How to cite: Vidal Reyes, M. I., Reguzzi, S., Marini, M., Petagine, A., Menegoni, N., Amadori, C., Maino, M., Tesauro, M., and Nader, F. H.: Geological characterization of the Tertiary Piedmont Basin geothermal system: new insights from structural and stratigraphic analyses , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8941, https://doi.org/10.5194/egusphere-egu25-8941, 2025.
The North Alpine Foreland Basin is the peripheral foredeep of the Northern Alps, extending from Lake Geneva in the West to Upper Austria in the East. The largest portion of the foredeep consists of an undeformed part, called Foreland Molasse, and a small, deformed belt along the North Alpine Thrust Front, called Subalpine Molasse. Spanning up to 150 km in N-S direction, the North Alpine Foreland Basin has its widest extent in SE Germany (Bavaria). Here, the physical properties of the Cenozoic basin fill and its underlying Mesozoic passive margin sediments display a high degree of heterogeneity in both the Foreland Molasse and Subalpine Molasse parts. Since 2016, we systematically analysed data from more than 300 deep wellbores, with vertical depths up to 5 km below ground level, to understand the distribution and interplay of these heterogeneities: We used minimum stress magnitude measurements such as formation integrity and leak-off tests in combination with geophysical borehole measurements such as density and velocity to infer the distribution of lateral and vertical stresses in the SE German part of the North Alpine Foreland Basin. Collection of pore pressure indicators and measurements such as drilling mud weights, drilling problems, well tests and wireline formation tests and their correlation with vertical stress and sediment compaction allowed us to also infer the regional distribution of pore pressure and to model the variable styles of deformation of the Subalpine Molasse along the North Alpine Thrust Front. In this contribution, we give a graphical overview of how stress, pore pressure and deformation are linked and driven by sediment composition and compaction. We also set our findings into context with high frequency, large amplitude variations of temperature and fluid flow patterns, proposing an updated model for the distribution and interference of physical properties and processes in the North Alpine Foreland Basin in SE Germany.
How to cite: Drews, M., Duschl, F., Mahmoodpour, S., Aconcha, E., Breitsameter, J., Obermeier, P., Shatyrbayeva, I., Babaie, P., Tomsu, C., and Einsiedl, F.: Stress, pore pressure, sediment compaction, deformation, temperature and fluid flow in the SE German part of the North Alpine Foreland Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10051, https://doi.org/10.5194/egusphere-egu25-10051, 2025.
Understanding the internal structure of intra-salt layers within deformed salt bodies is crucial for geo-energy storage in salt-bearing basins. This study integrates high-resolution 2D finite element numerical modelling to explore how variations in salt stratigraphy, lithological heterogeneity, and post-salt sedimentation patterns influence deformation processes and the internal architecture of diapiric salt structures across different basin geometries. Specifically, we examine the impact of lithological variability by systematically varying the position and thickness of frictional-plastic, relatively strong intra-salt layers (e.g., anhydrite or carbonates) within a viscous layered salt sequence. The position of the strong intra-salt layer within a salt body significantly influences salt flow dynamics, internal and external diapir morphology, and overburden deformation. When located at the top, the strong layer acts as a stiff cap, restricting upward salt flow and producing broader diapirs with limited overburden deformation. When located in the middle, it localizes strain within the salt, leading to sharper and more discrete diapirs. When located at the bottom, it enhances upward salt flow of the overlying weak salt layer, resulting in tall, narrow, and more intrusive diapirs with more pronounced overburden deformation. In all cases, the strong intra-salt layer breaks and forms boudins, which vary in dimensions, distribution and structural complexity according to their different position and thickness. These intra-salt boudins can be transported by the salt flow to the upper parts of salt structures, but are often trapped at diapir pedestals, beneath diapir flanks, or under minibasins, where they experience repeated folding and refolding as the weaker, less dense salt flows around them. The presence of this heterogeneous intra-salt layer alters the flow paths of the weaker salt and controls both the geometry of salt structures and associated deformation in the overburden. These findings underscore the critical role of stratigraphic and tectonic controls in shaping both the external and internal architecture of salt diapirs, patterns that are particularly relevant for the North Sea, where salt structures play a crucial role in emerging geo-energy storage.
How to cite: Ramos, M., Huismans, R., Muniz Pichel, L., Theunissen, T., Callot, J.-P., Pichat, A., Célini, N., Delahaye, S., and Gout, C.: Influence of Intra-Salt Lithological Variability on Salt Tectonics: A numerical modelling approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8201, https://doi.org/10.5194/egusphere-egu25-8201, 2025.
The Instituto Português do Mar e da Atmosfera (IPMA) is undertaking extensive high-resolution geophysical and geotechnical studies over two areas proposed for the development of offshore windfarms in Portugal, surveying an area of circa 2000 km2. Leixões and Figueira da Foz study areas are located off the Portuguese mainland west coast, at depths between 120m and 530m, distant 21nm to 35nm to the coastline.
The aim of this work, being conducted between February 2024 and June 2026, is to provide detailed data on the morphology, geology, geophysics and geotechnical properties of the seafloor to inform offshore wind farm developers towards engineering and financial strategies, therefore providing the basis for launching subsequent auctions for the offshore areas listed in the Portuguese National Maritime Spatial Planning Situation Plan.
An initial exploratory campaign, commissioned to the Portuguese Hydrographic Institute, collected the initial MBES data (bathymetry and backscatter) and surface sediment sampling. Furthermore, in August-September 2024, a geophysical survey took place on board IPMA’s NI Mário Ruivo and retrieved over 2100 km of seismic data, from parametric sub bottom profiler (SBP) and multi-channel ultra-high resolution seismic reflection (UHRS). Preliminary results attest the scientific richness of the dataset already collected as well as the complexity and diversity of the seimostratigraphy present in the surveyed areas. Seabed morphology, sediment textural features, seismic horizons and geohazards have been identified which allow inference of a preliminary geomodel of the areas and the planning of subsequent surveys.
Between May and November 2025 a survey will take place expanding the resolution of data collected (> 20 000 km lines planned) but also adding additional methodologies (magnetometer, side scan sonar, vibrocorer and CPT’s).
The data to retrieve over these 2 years will allow to produce a detailed Terrain model supporting a holistic data interpretation, essential for succeeding actions in the pioneering development of floating wind farms offshore Portugal.
This comprehensive geophysical and geotechnical characterization represents a pioneering effort in Portugal's energy transition, providing crucial data for the sustainable development of offshore wind energy and potentially serving as a model for similar initiatives.
This research was funded by PRR funds - RP-C21-i07.01 - Technical studies for offshore energy potential. This work is also supported by the Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2025, UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020) and LA/P/0068/2020 https://doi.org/10.54499/LA/P/0068/2020).
How to cite: Brito, P., Batista, L., Borges, R., Costa, P., Neres, M., Noiva, J., Pereira, Â., Ribeiro, C., Rosa, M., and Terrinha, P.: Geophysical and Geotechnical offshore studies: pioneering contribution to shape Portugal’s wind farm strategy , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19413, https://doi.org/10.5194/egusphere-egu25-19413, 2025.
