Pub Date : 2026-04-01Epub Date: 2026-01-13DOI: 10.1016/j.earscirev.2026.105397
Nicholas Hayward , Quentin Masurel , Nicolas Thébaud , Graham C. Begg
Improving discovery rates for Tier 1 magmatic ore deposits requires more accurate prediction of camp-scale structural targets and mapping of (trans-)lithospheric fault zones (LFZs). Here we review LFZ architecture, evolution and behaviour, and their spatial correlation with large ore deposit clusters based on >120 global case studies of magmatic Ni-Cu (-PGE) and porphyry Cu (-Au,Mo) deposits. At belt-scale, the most prospective LFZs are the longest and deepest ones formed at lithospheric domain boundaries (“primary strike-parallel”). At district- to camp-scales, the strongest structural predictor for giant Ni and Cu discoveries is proximity to secondary transverse LFZ intersections that provided long-lived, subvertical, pipe-like, mantle-tapping conduits. The transverse LFZ correlation is stronger for large porphyry Cu deposits (∼90% within 5 km) than for large magmatic Ni-Cu (-PGE) deposits (∼82% within 25 km).
Magmatic-hydrothermal mineral systems are driven bottom-up by transfer of mechanical stress, heat, fluid, and metals from upwelling asthenosphere or slab subduction. Positive feedback from thermal, reaction, and strain softening partitions these drivers first into translithospheric fault zones, which evolve at the expense of transcrustal fault zones to efficiently channel the extreme energy, fluid and metal fluxes required to form giant magmatic-hydrothermal deposits. The dynamic fault-valve behaviour of LFZs, triggered by intermittent coupling across transient rheological barriers, enhances system self-organization and drives both exceptional fertility enhancement (when stalled) and extreme fluid fluxes (when released).
From our results, we identify key knowledge gaps and future research priorities, and propose a refined, systems-based approach to mapping LFZs aimed at enhancing the targeting of giant ore systems and mineral resource discovery performance.
{"title":"Translithospheric fault targeting for giant magmatic (-hydrothermal) ore deposit discoveries: recent advances and leading practices","authors":"Nicholas Hayward , Quentin Masurel , Nicolas Thébaud , Graham C. Begg","doi":"10.1016/j.earscirev.2026.105397","DOIUrl":"10.1016/j.earscirev.2026.105397","url":null,"abstract":"<div><div>Improving discovery rates for Tier 1 magmatic ore deposits requires more accurate prediction of camp-scale structural targets and mapping of (trans-)lithospheric fault zones (LFZs). Here we review LFZ architecture, evolution and behaviour, and their spatial correlation with large ore deposit clusters based on >120 global case studies of magmatic Ni-Cu (-PGE) and porphyry Cu (-Au,Mo) deposits. At belt-scale, the most prospective LFZs are the longest and deepest ones formed at lithospheric domain boundaries (“primary strike-parallel”). At district- to camp-scales, the strongest structural predictor for giant Ni and Cu discoveries is proximity to secondary transverse LFZ intersections that provided long-lived, subvertical, pipe-like, mantle-tapping conduits. The transverse LFZ correlation is stronger for large porphyry Cu deposits (∼90% within 5 km) than for large magmatic Ni-Cu (-PGE) deposits (∼82% within 25 km).</div><div>Magmatic-hydrothermal mineral systems are driven bottom-up by transfer of mechanical stress, heat, fluid, and metals from upwelling asthenosphere or slab subduction. Positive feedback from thermal, reaction, and strain softening partitions these drivers first into translithospheric fault zones, which evolve at the expense of transcrustal fault zones to efficiently channel the extreme energy, fluid and metal fluxes required to form giant magmatic-hydrothermal deposits. The dynamic fault-valve behaviour of LFZs, triggered by intermittent coupling across transient rheological barriers, enhances system self-organization and drives both exceptional fertility enhancement (when stalled) and extreme fluid fluxes (when released).</div><div>From our results, we identify key knowledge gaps and future research priorities, and propose a refined, systems-based approach to mapping LFZs aimed at enhancing the targeting of giant ore systems and mineral resource discovery performance.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105397"},"PeriodicalIF":10.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145962705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2026-01-22DOI: 10.1016/j.earscirev.2026.105400
Kevin Wong , Martina Cascone , Donato Giovannelli , Alberto Vitale Brovarone
Molecular hydrogen (H2) is a fundamental component of planetary evolution and an important energy source for microbial life. It is now understood that natural mechanisms, spanning geological and biological processes, can produce high concentrations of hydrogen in natural fluids. Quantifying the processes that modulate natural hydrogen concentrations is necessary not only for conceptualising the distribution of life on Earth and elsewhere in the universe, but also for identifying settings where natural hydrogen may potentially accumulate to complement industrial hydrogen production. However, uncertainties persist in assessing these natural fluxes. In this review, we explore the biological and geological processes that can generate natural hydrogen. Compared to previous summary efforts, we include in our updated inventory hydrogen fluxes from biological processes, metamorphic degassing, and subduction zones. By integrating recent advances in quantifying hydrogen generation and transportation in geological environments, we demonstrate that significant concentrations and fluxes of hydrogen can arise in a plethora of settings worldwide, contributing towards a total abiotic production rate of 40 to 64< Mt H2 yr-1. We also highlight that geological environments characterised by high hydrogen production may be associated with high microbial hydrogen consumption (e.g., oceanic sediments). However, large uncertainties regarding the residence time of hydrogen within geological settings remain, and future research endeavours should aim to ascertain the long-term behaviour of hydrogen stored in the deep Earth to assess the viability of natural hydrogen as a renewable energy source.
{"title":"Formation and fluxes of natural hydrogen in the crust and upper mantle","authors":"Kevin Wong , Martina Cascone , Donato Giovannelli , Alberto Vitale Brovarone","doi":"10.1016/j.earscirev.2026.105400","DOIUrl":"10.1016/j.earscirev.2026.105400","url":null,"abstract":"<div><div>Molecular hydrogen (H<sub>2</sub>) is a fundamental component of planetary evolution and an important energy source for microbial life. It is now understood that natural mechanisms, spanning geological and biological processes, can produce high concentrations of hydrogen in natural fluids. Quantifying the processes that modulate natural hydrogen concentrations is necessary not only for conceptualising the distribution of life on Earth and elsewhere in the universe, but also for identifying settings where natural hydrogen may potentially accumulate to complement industrial hydrogen production. However, uncertainties persist in assessing these natural fluxes. In this review, we explore the biological and geological processes that can generate natural hydrogen. Compared to previous summary efforts, we include in our updated inventory hydrogen fluxes from biological processes, metamorphic degassing, and subduction zones. By integrating recent advances in quantifying hydrogen generation and transportation in geological environments, we demonstrate that significant concentrations and fluxes of hydrogen can arise in a plethora of settings worldwide, contributing towards a total abiotic production rate of 40 to 64< Mt H<sub>2</sub> yr<sup>-1</sup>. We also highlight that geological environments characterised by high hydrogen production may be associated with high microbial hydrogen consumption (e.g., oceanic sediments). However, large uncertainties regarding the residence time of hydrogen within geological settings remain, and future research endeavours should aim to ascertain the long-term behaviour of hydrogen stored in the deep Earth to assess the viability of natural hydrogen as a renewable energy source.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105400"},"PeriodicalIF":10.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146033654","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2026-01-30DOI: 10.1016/j.earscirev.2026.105409
José Carlos Gonzalez-Hidalgo , Santiago Beguería
This article reviews published research on trends in extreme precipitation events across the Mediterranean basin between 1980 and 2025. A total of 175 peer-reviewed studies were compiled using standardized search criteria across major bibliographic databases. The review focuses on reporting the diversity of findings as presented by their authors, while it does not assess the quality of data, methods, or definitions used in individual studies. To avoid misinterpretation, and ensure traceability of our research, key statements regarding trends transcribed directly from each paper's abstract, main text, or conclusions are compiled. The results highlight substantial spatial and temporal heterogeneity in reported trends, with few statistically significant and regionally consistent patterns. While in some subregions (particularly parts of Italy, southern France, some areas of Spanish east-coastland and North-Western Africa coastland) localized increases in high-magnitude rainfall events have been found, many areas show either no trend or statistically insignificant changes. The evidence does not support a basin-wide intensification of extreme precipitation, and observed trends appear more strongly influenced by local geographic and synoptic factors, or linked to specific analysis time windows, than by a coherent signal of global climate forcing. These findings underscore the importance of continued observation, high-resolution analysis, and cautious interpretation of regional extremes in a climate change context. A more unified methodological framework is needed to improve comparability across studies and support effective risk management and adaptation strategies in this highly exposed region.
{"title":"Is daily extreme rainfall increasing in the Mediterranean basin? A critical review of the evidence","authors":"José Carlos Gonzalez-Hidalgo , Santiago Beguería","doi":"10.1016/j.earscirev.2026.105409","DOIUrl":"10.1016/j.earscirev.2026.105409","url":null,"abstract":"<div><div>This article reviews published research on trends in extreme precipitation events across the Mediterranean basin between 1980 and 2025. A total of 175 peer-reviewed studies were compiled using standardized search criteria across major bibliographic databases. The review focuses on reporting the diversity of findings as presented by their authors, while it does not assess the quality of data, methods, or definitions used in individual studies. To avoid misinterpretation, and ensure traceability of our research, key statements regarding trends transcribed directly from each paper's abstract, main text, or conclusions are compiled. The results highlight substantial spatial and temporal heterogeneity in reported trends, with few statistically significant and regionally consistent patterns. While in some subregions (particularly parts of Italy, southern France, some areas of Spanish east-coastland and North-Western Africa coastland) localized increases in high-magnitude rainfall events have been found, many areas show either no trend or statistically insignificant changes. The evidence does not support a basin-wide intensification of extreme precipitation, and observed trends appear more strongly influenced by local geographic and synoptic factors, or linked to specific analysis time windows, than by a coherent signal of global climate forcing. These findings underscore the importance of continued observation, high-resolution analysis, and cautious interpretation of regional extremes in a climate change context. A more unified methodological framework is needed to improve comparability across studies and support effective risk management and adaptation strategies in this highly exposed region.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105409"},"PeriodicalIF":10.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146089743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2026-01-28DOI: 10.1016/j.earscirev.2026.105411
Yue Zhang , Zhenxue Dai , Hung Vo Thanh , Mingxu Cao , Lulu Xu , Xiaoying Zhang , Bicheng Yan , Philip H. Stauffer , Huichao Yin , Kenneth C. Carroll , Mohamad Reza Soltanian
Underground Hydrogen Storage (UHS) is a promising solution for large-scale energy storage and a critical component in advancing low-carbon energy system. Ensuring the safety and efficiency of UHS necessitates a comprehensive understanding of multiphysical interactions driven by cyclic pore fluid pressure fluctuations and coupled physicochemical processes. This review examines the key geomechanical responses in UHS, including rock property variations under cyclic loading, fracture evolution and propagation, reservoir stress sensitivity, and fault stability. It also explores the impact of geochemical and microbial reactions on geomechanical characteristics. We provide an in-depth analysis of Thermal-Hydraulic-Mechanical-Chemical (THMC) coupled numerical simulations, highlighting their potential for future multi-scale modeling. Limitations of current machine learning (ML) approaches in addressing UHS challenges are highlighted, emphasizing the need for innovative ML-based methodologies. Operational strategies for hydrogen injection and production are reviewed, focusing on safety, efficiency, and economic viability. The necessity for multi-objective optimization (MOO) to balance storage efficiency, risk mitigation, and cost-effectiveness is also discussed. Current monitoring technologies are evaluated to ensure safe and efficient UHS operations. Finally, this review identifies critical knowledge gaps and underscores the importance of advancing geomechanical understanding under multiphysics-coupling. We highlight the need for ML-driven multiphysics theories, enhanced modeling techniques, and robust optimization strategies to improve UHS performance. This study serves as a comprehensive reference for future research and the large-scale implementation of UHS systems.
{"title":"Innovations in underground hydrogen storage with multiphysics simulations, optimization, and monitoring: A review","authors":"Yue Zhang , Zhenxue Dai , Hung Vo Thanh , Mingxu Cao , Lulu Xu , Xiaoying Zhang , Bicheng Yan , Philip H. Stauffer , Huichao Yin , Kenneth C. Carroll , Mohamad Reza Soltanian","doi":"10.1016/j.earscirev.2026.105411","DOIUrl":"10.1016/j.earscirev.2026.105411","url":null,"abstract":"<div><div>Underground Hydrogen Storage (UHS) is a promising solution for large-scale energy storage and a critical component in advancing low-carbon energy system. Ensuring the safety and efficiency of UHS necessitates a comprehensive understanding of multiphysical interactions driven by cyclic pore fluid pressure fluctuations and coupled physicochemical processes. This review examines the key geomechanical responses in UHS, including rock property variations under cyclic loading, fracture evolution and propagation, reservoir stress sensitivity, and fault stability. It also explores the impact of geochemical and microbial reactions on geomechanical characteristics. We provide an in-depth analysis of Thermal-Hydraulic-Mechanical-Chemical (THMC) coupled numerical simulations, highlighting their potential for future multi-scale modeling. Limitations of current machine learning (ML) approaches in addressing UHS challenges are highlighted, emphasizing the need for innovative ML-based methodologies. Operational strategies for hydrogen injection and production are reviewed, focusing on safety, efficiency, and economic viability. The necessity for multi-objective optimization (MOO) to balance storage efficiency, risk mitigation, and cost-effectiveness is also discussed. Current monitoring technologies are evaluated to ensure safe and efficient UHS operations. Finally, this review identifies critical knowledge gaps and underscores the importance of advancing geomechanical understanding under multiphysics-coupling. We highlight the need for ML-driven multiphysics theories, enhanced modeling techniques, and robust optimization strategies to improve UHS performance. This study serves as a comprehensive reference for future research and the large-scale implementation of UHS systems.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105411"},"PeriodicalIF":10.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146071754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2026-02-01DOI: 10.1016/j.earscirev.2026.105413
Giuseppe Etiope , Geoffrey S. Ellis , Omid H. Ardakani , Christopher J. Boreham , Peter Klitzke , Antonio Martín-Monge , Humberto L.S. Reis , Alexis S. Templeton , Hyeong Soo Kim , Eric Gaucher , Olivier Sissmann
<div><div>A comprehensive scientific research roadmap is essential to bridge knowledge gaps and deepen the understanding of key geological, geochemical, and geophysical aspects of natural hydrogen (H<sub>2</sub>) as a potential new energy resource. This paper reviews major scientific uncertainties on natural H<sub>2</sub>, suggesting research priorities, as a guide for defining exploration strategies, techniques, and data interpretation. The uncertainties concern all phases of the natural H<sub>2</sub> cycle, from generation (source rocks) through migration (advection and diffusion) and accumulation (reservoir and cap rocks) to the application and interpretation of subsurface and surface geochemical and geophysical exploration techniques. Understanding H<sub>2</sub> sources and generation rates (the amount of H<sub>2</sub> generated by a given volume of rock over time) is crucial for determining whether a geological H<sub>2</sub> system operates as a short-term dynamic system with rapid H<sub>2</sub> production and release, or as a conventional gas system with long-term accumulations, analogous to petroleum reservoirs. Preliminary estimates for serpentinisation, radiolysis, and organic matter degradation suggest that H<sub>2</sub> generation is not inherently fast, especially for non-hydrothermal continental systems (crystalline basement of shields, ophiolites, peridotite massifs, sedimentary basins), and long-term accumulations, like those of fossil natural gas systems, represent the most likely scenario. The mechanisms of H<sub>2</sub> migration through geological formations require application of fundamental principles of fluid-flow physics, distinguishing advection and diffusion, as well as their forms (from gas-phase, bubble flows to aqueous solutions). Additional studies of H<sub>2</sub> accumulation and retention in subsurface reservoirs could improve understanding of mechanisms of H<sub>2</sub> migration by focusing on the rock fluid-bearing properties and the factors affecting H<sub>2</sub> preservation, such as the presence of cap rocks impermeable to H<sub>2</sub>, pressure conditions, residence times, and microbial or abiotic consumption. Advanced techniques, including reservoir modelling, flow simulations, 3D imaging (micro-CT) of H<sub>2</sub>-bearing rocks, and extraction and analysis of gas occluded in rocks, can provide insights into the stability and potential recoverability of H<sub>2</sub> accumulations. The interpretation of surface exploration techniques, including gas geochemistry, geophysics, and remote sensing, long employed in mineral and energy resource exploration, is now being adapted for natural H<sub>2</sub> studies, but challenges remain in the data interpretation. Distinguishing H<sub>2</sub> seepage due to geological degassing from H<sub>2</sub> produced near the surface by modern microbial processes or artificial sources, such as hammering or drilling for soil-gas sampling, drilling into aquifers, and corrosion
{"title":"Understanding the resource potential of natural hydrogen on Earth: Scientific gaps, uncertainties and recommendations","authors":"Giuseppe Etiope , Geoffrey S. Ellis , Omid H. Ardakani , Christopher J. Boreham , Peter Klitzke , Antonio Martín-Monge , Humberto L.S. Reis , Alexis S. Templeton , Hyeong Soo Kim , Eric Gaucher , Olivier Sissmann","doi":"10.1016/j.earscirev.2026.105413","DOIUrl":"10.1016/j.earscirev.2026.105413","url":null,"abstract":"<div><div>A comprehensive scientific research roadmap is essential to bridge knowledge gaps and deepen the understanding of key geological, geochemical, and geophysical aspects of natural hydrogen (H<sub>2</sub>) as a potential new energy resource. This paper reviews major scientific uncertainties on natural H<sub>2</sub>, suggesting research priorities, as a guide for defining exploration strategies, techniques, and data interpretation. The uncertainties concern all phases of the natural H<sub>2</sub> cycle, from generation (source rocks) through migration (advection and diffusion) and accumulation (reservoir and cap rocks) to the application and interpretation of subsurface and surface geochemical and geophysical exploration techniques. Understanding H<sub>2</sub> sources and generation rates (the amount of H<sub>2</sub> generated by a given volume of rock over time) is crucial for determining whether a geological H<sub>2</sub> system operates as a short-term dynamic system with rapid H<sub>2</sub> production and release, or as a conventional gas system with long-term accumulations, analogous to petroleum reservoirs. Preliminary estimates for serpentinisation, radiolysis, and organic matter degradation suggest that H<sub>2</sub> generation is not inherently fast, especially for non-hydrothermal continental systems (crystalline basement of shields, ophiolites, peridotite massifs, sedimentary basins), and long-term accumulations, like those of fossil natural gas systems, represent the most likely scenario. The mechanisms of H<sub>2</sub> migration through geological formations require application of fundamental principles of fluid-flow physics, distinguishing advection and diffusion, as well as their forms (from gas-phase, bubble flows to aqueous solutions). Additional studies of H<sub>2</sub> accumulation and retention in subsurface reservoirs could improve understanding of mechanisms of H<sub>2</sub> migration by focusing on the rock fluid-bearing properties and the factors affecting H<sub>2</sub> preservation, such as the presence of cap rocks impermeable to H<sub>2</sub>, pressure conditions, residence times, and microbial or abiotic consumption. Advanced techniques, including reservoir modelling, flow simulations, 3D imaging (micro-CT) of H<sub>2</sub>-bearing rocks, and extraction and analysis of gas occluded in rocks, can provide insights into the stability and potential recoverability of H<sub>2</sub> accumulations. The interpretation of surface exploration techniques, including gas geochemistry, geophysics, and remote sensing, long employed in mineral and energy resource exploration, is now being adapted for natural H<sub>2</sub> studies, but challenges remain in the data interpretation. Distinguishing H<sub>2</sub> seepage due to geological degassing from H<sub>2</sub> produced near the surface by modern microbial processes or artificial sources, such as hammering or drilling for soil-gas sampling, drilling into aquifers, and corrosion ","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105413"},"PeriodicalIF":10.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146098420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2026-01-25DOI: 10.1016/j.earscirev.2026.105402
Jianzhou Tang , Jinzhuang Xue , Shuangming Wang
Coal seams, as a result of the coalification of terrestrial plant matter, were previously regarded as unfavorable for economically significant helium accumulations. However, this viewpoint has been challenged by the increasing discoveries of helium-rich gas reservoirs in such settings. This review investigates the major controls on commercial helium accumulations in coal seams, using an integrated analysis of basin geology and gas geochemistry. Six main findings are summarized as follows. (1) Naturally occurring helium accumulates in nitrogen-, carbon dioxide-, methane-, and mixed-gas reservoirs, with nitrogen and methane reservoirs being the most favorable for commercial helium accumulation. (2) Commercial helium accumulation in coal seams is predominantly (> 70%) of external origin, although these seams are commonly enriched in thorium and uranium. (3) The formation of helium accumulations in coal seams largely depends on an external replenishment system, including source rocks, carrier fluids, migration pathways, and an open system. (4) Two key geological elements contribute to favorable trap conditions: one is coal seams that show high water saturation, effective pore connectivity, and adequate natural gas; and the other is overlying cap rocks that exhibit fine pore throats, high gas pressure, low temperature, and high associated fluid content. (5) An accumulation window at a depth of ca. 100–1250 m for helium in coal seams is proposed. (6) Three main geological patterns, namely basement uplift, basement fault and anticlinal crest patterns, are proposed for commercial helium accumulations in coal seams, and these patterns can be distinguished by variations in He/N2 ratios and N2, CO2, and CH4 contents. The findings presented herein are expected to provide guidance for helium exploration in coal seams.
{"title":"Controls on commercial helium accumulation in coal seams: From fundamentals to an integration of basin geology and gas geochemistry","authors":"Jianzhou Tang , Jinzhuang Xue , Shuangming Wang","doi":"10.1016/j.earscirev.2026.105402","DOIUrl":"10.1016/j.earscirev.2026.105402","url":null,"abstract":"<div><div>Coal seams, as a result of the coalification of terrestrial plant matter, were previously regarded as unfavorable for economically significant helium accumulations. However, this viewpoint has been challenged by the increasing discoveries of helium-rich gas reservoirs in such settings. This review investigates the major controls on commercial helium accumulations in coal seams, using an integrated analysis of basin geology and gas geochemistry. Six main findings are summarized as follows. (1) Naturally occurring helium accumulates in nitrogen-, carbon dioxide-, methane-, and mixed-gas reservoirs, with nitrogen and methane reservoirs being the most favorable for commercial helium accumulation. (2) Commercial helium accumulation in coal seams is predominantly (> 70%) of external origin, although these seams are commonly enriched in thorium and uranium. (3) The formation of helium accumulations in coal seams largely depends on an external replenishment system, including source rocks, carrier fluids, migration pathways, and an open system. (4) Two key geological elements contribute to favorable trap conditions: one is coal seams that show high water saturation, effective pore connectivity, and adequate natural gas; and the other is overlying cap rocks that exhibit fine pore throats, high gas pressure, low temperature, and high associated fluid content. (5) An accumulation window at a depth of ca. 100–1250 m for helium in coal seams is proposed. (6) Three main geological patterns, namely basement uplift, basement fault and anticlinal crest patterns, are proposed for commercial helium accumulations in coal seams, and these patterns can be distinguished by variations in He/N<sub>2</sub> ratios and N<sub>2</sub>, CO<sub>2</sub>, and CH<sub>4</sub> contents. The findings presented herein are expected to provide guidance for helium exploration in coal seams.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105402"},"PeriodicalIF":10.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2026-01-28DOI: 10.1016/j.earscirev.2026.105412
Franck Eitel Kemgang Ghomsi , Robert Tenzer , Wenjin Chen , Alexey Baranov , Ojima Isaac Apeh , Tan Xiaolong , Hong Guoqing , Julienne Stroeve
The African continent is characterized by a complex tectonic and geological history, with its current configuration shaped by the assemblage of Precambrian cratons and fragments delineated by Proterozoic and Paleozoic mobile belts. Knowledge of its lithospheric structure has primarily been derived from sparsely and irregularly distributed seismic surveys, limiting continent-wide analysis. To address this issue, we utilize satellite (e.g., GOCE, GRACE) and terrestrial gravity observations, integrated with lithospheric structure models, to compile a suite of gravity maps on a 5′ × 5′ geographical grid. The maps of the free-air, Bouguer, crust-stripped, mantle, lithosphere-stripped, and sub-lithospheric mantle gravity disturbances enable detailed interpretation of Africa's lithospheric architecture. Our methodology enhances traditional gravimetric studies by applying advanced corrections for topographic, bathymetric, sediment, crustal, and lithospheric mantle density heterogeneities, revealing deeper structural signatures. The free-air gravity map exhibits a signature of topographic and upper crustal density variations, with positive anomalies (+50 to +150 mGal) over elevated regions (e.g., Ethiopian Plateau) and negative anomalies (−50 to −150 mGal) over sedimentary basins (e.g., Congo Basin). The Bouguer gravity map highlights tectonic and volcanic features, reflecting crustal thickness variations, with isostatic equilibrium in cratons and disequilibrium along continental rifts like the East African Rift System (EARS). The crust-stripped gravity map mirrors Moho geometry, showing a stark contrast between thin oceanic and thick continental crust. The mantle gravity map exhibits a thermal signature, with gravity lows marking active divergent margins along the East and West Rift Systems and highs coinciding with cold, stable Archean cratons. Combined Bouguer and mantle gravity analyses confirm a non-collisional origin of mountain ranges along the EARS. Notably, the southern portion of the EARS lacks a clear thermal signature, suggesting distributed deformation at diffuse plate boundaries. These findings, alongside signatures of the African Superswell and the Congo Craton subsidence, provide new insights into Africa's geodynamic evolution, supporting future geophysical and resource exploration efforts.
{"title":"Gravity maps of the African continental crustal and mantle structure","authors":"Franck Eitel Kemgang Ghomsi , Robert Tenzer , Wenjin Chen , Alexey Baranov , Ojima Isaac Apeh , Tan Xiaolong , Hong Guoqing , Julienne Stroeve","doi":"10.1016/j.earscirev.2026.105412","DOIUrl":"10.1016/j.earscirev.2026.105412","url":null,"abstract":"<div><div>The African continent is characterized by a complex tectonic and geological history, with its current configuration shaped by the assemblage of Precambrian cratons and fragments delineated by Proterozoic and Paleozoic mobile belts. Knowledge of its lithospheric structure has primarily been derived from sparsely and irregularly distributed seismic surveys, limiting continent-wide analysis. To address this issue, we utilize satellite (e.g., GOCE, GRACE) and terrestrial gravity observations, integrated with lithospheric structure models, to compile a suite of gravity maps on a 5′ × 5′ geographical grid. The maps of the free-air, Bouguer, crust-stripped, mantle, lithosphere-stripped, and sub-lithospheric mantle gravity disturbances enable detailed interpretation of Africa's lithospheric architecture. Our methodology enhances traditional gravimetric studies by applying advanced corrections for topographic, bathymetric, sediment, crustal, and lithospheric mantle density heterogeneities, revealing deeper structural signatures. The free-air gravity map exhibits a signature of topographic and upper crustal density variations, with positive anomalies (+50 to +150 mGal) over elevated regions (e.g., Ethiopian Plateau) and negative anomalies (−50 to −150 mGal) over sedimentary basins (e.g., Congo Basin). The Bouguer gravity map highlights tectonic and volcanic features, reflecting crustal thickness variations, with isostatic equilibrium in cratons and disequilibrium along continental rifts like the East African Rift System (EARS). The crust-stripped gravity map mirrors Moho geometry, showing a stark contrast between thin oceanic and thick continental crust. The mantle gravity map exhibits a thermal signature, with gravity lows marking active divergent margins along the East and West Rift Systems and highs coinciding with cold, stable Archean cratons. Combined Bouguer and mantle gravity analyses confirm a non-collisional origin of mountain ranges along the EARS. Notably, the southern portion of the EARS lacks a clear thermal signature, suggesting distributed deformation at diffuse plate boundaries. These findings, alongside signatures of the African Superswell and the Congo Craton subsidence, provide new insights into Africa's geodynamic evolution, supporting future geophysical and resource exploration efforts.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105412"},"PeriodicalIF":10.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146072659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2026-02-02DOI: 10.1016/j.earscirev.2026.105419
Shreya Katre, K. Ravi, Archana M. Nair
Scalable geochemical Carbon Dioxide Removal (CDR) technologies are essential for limiting global warming to 1.5 °C. These technologies capture and permanently store atmospheric CO₂ as carbonates using alkaline substrates such as mafic and ultramafic rocks rich in calcium (Ca) and magnesium (Mg) minerals. This study is the first to comprehensively map and assess the significant geological resources of India for geochemical CDR. Ophiolitic sequences, mafic dyke swarms in cratons, and basaltic formations contain diverse Ca- and Mg-rich silicate minerals, providing substantial alkalinity sources for effective CO₂ sequestration through aqueous engineered carbon mineralisation and enhanced chemical weathering. Analysis of 500 data points across India revealed an average CDR potential of ∼424 gCO₂/kg through alkalinity production and ∼270 gCO₂/kg via carbonation. Ultramafic rocks, including dunite, harzburgite, and peridotite, demonstrated the highest average CDR potential (∼647 gCO₂/kg), while mafic rocks, such as gabbro and basalt, showed moderate potential (∼308 gCO₂/kg). A shrinking core model assessed how rock composition affects cumulative CDR potential over 0–70 years under ambient conditions. Dunite showed the highest sCDR potential (∼441 gCO₂/kg), followed by peridotite (∼298 gCO₂/kg), while plagioclase-rich rocks like gabbro exhibited much lower rates (<30 gCO₂/kg). These results underline the high CDR efficiency of ultramafic rocks and highlight olivine-rich rocks as promising candidates for rapid CO₂ mineralisation, achieving substantial sequestration on human timescales. In summary, this study highlights the vast potential of India's geological resources for CDR through geochemical pathways.
{"title":"A review on geochemical carbon dioxide removal potential of mafic and ultramafic rocks in India","authors":"Shreya Katre, K. Ravi, Archana M. Nair","doi":"10.1016/j.earscirev.2026.105419","DOIUrl":"10.1016/j.earscirev.2026.105419","url":null,"abstract":"<div><div>Scalable geochemical Carbon Dioxide Removal (CDR) technologies are essential for limiting global warming to 1.5 °C. These technologies capture and permanently store atmospheric CO₂ as carbonates using alkaline substrates such as mafic and ultramafic rocks rich in calcium (Ca) and magnesium (Mg) minerals. This study is the first to comprehensively map and assess the significant geological resources of India for geochemical CDR. Ophiolitic sequences, mafic dyke swarms in cratons, and basaltic formations contain diverse Ca- and Mg-rich silicate minerals, providing substantial alkalinity sources for effective CO₂ sequestration through aqueous engineered carbon mineralisation and enhanced chemical weathering. Analysis of 500 data points across India revealed an average CDR potential of ∼424 gCO₂/kg through alkalinity production and ∼270 gCO₂/kg via carbonation. Ultramafic rocks, including dunite, harzburgite, and peridotite, demonstrated the highest average CDR potential (∼647 gCO₂/kg), while mafic rocks, such as gabbro and basalt, showed moderate potential (∼308 gCO₂/kg). A shrinking core model assessed how rock composition affects cumulative CDR potential over 0–70 years under ambient conditions. Dunite showed the highest sCDR potential (∼441 gCO₂/kg), followed by peridotite (∼298 gCO₂/kg), while plagioclase-rich rocks like gabbro exhibited much lower rates (<30 gCO₂/kg). These results underline the high CDR efficiency of ultramafic rocks and highlight olivine-rich rocks as promising candidates for rapid CO₂ mineralisation, achieving substantial sequestration on human timescales. In summary, this study highlights the vast potential of India's geological resources for CDR through geochemical pathways.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105419"},"PeriodicalIF":10.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146110674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2026-02-02DOI: 10.1016/j.earscirev.2026.105417
Kate Andrzejewski , Julia A. McIntosh , Erik L. Gulbranson , Daniel Ibarra
Fossilized soils, or paleosols, contain soil-formed phyllosilicates whose stable isotopic compositions may be used to calculate paleotemperature and thus reconstruct ancient terrestrial environments. Though paleosols are common in the geologic record, the use of phyllosilicates as paleotemperature proxies is limited in the literature owing to difficulties with selecting optimal paleosols, isolation from non-clay minerals and organic materials, mixtures of phyllosilicates in natural samples, wide variations of chemical compositions for phyllosilicates, and limited to undefined equilibrium fractionation factors between phyllosilicates-water. Here, we address these challenges by examining and comparing methods used for sample selection, mineral isolation, pretreatments, mineral identification, conventional and developing methods for oxygen and hydrogen isotopic analyses, and determination of phyllosilicate-water equilibrium fractionation factors, concluding with recommendations for best approaches for paleotemperature estimation. Additionally, we discuss how to identify and avoid detrital phyllosilicates, the impacts of diagenesis, comparison of stable isotope and non-isotope paleosol paleotemperature proxies, and challenges and opportunities for broadly using paleosols as paleoclimate archives. With ongoing efforts to refine this multi-faceted paleotemperature approach, the stable isotope geochemistry of soil-formed phyllosilicates continues to be an invaluable proxy system, enhancing our understanding of terrestrial paleoenvironments and paleoclimate.
{"title":"Estimating paleotemperature using stable isotopes of soil-formed phyllosilicates from paleosols: A review","authors":"Kate Andrzejewski , Julia A. McIntosh , Erik L. Gulbranson , Daniel Ibarra","doi":"10.1016/j.earscirev.2026.105417","DOIUrl":"10.1016/j.earscirev.2026.105417","url":null,"abstract":"<div><div>Fossilized soils, or paleosols, contain soil-formed phyllosilicates whose stable isotopic compositions may be used to calculate paleotemperature and thus reconstruct ancient terrestrial environments. Though paleosols are common in the geologic record, the use of phyllosilicates as paleotemperature proxies is limited in the literature owing to difficulties with selecting optimal paleosols, isolation from non-clay minerals and organic materials, mixtures of phyllosilicates in natural samples, wide variations of chemical compositions for phyllosilicates, and limited to undefined equilibrium fractionation factors between phyllosilicates-water. Here, we address these challenges by examining and comparing methods used for sample selection, mineral isolation, pretreatments, mineral identification, conventional and developing methods for oxygen and hydrogen isotopic analyses, and determination of phyllosilicate-water equilibrium fractionation factors, concluding with recommendations for best approaches for paleotemperature estimation. Additionally, we discuss how to identify and avoid detrital phyllosilicates, the impacts of diagenesis, comparison of stable isotope and non-isotope paleosol paleotemperature proxies, and challenges and opportunities for broadly using paleosols as paleoclimate archives. With ongoing efforts to refine this multi-faceted paleotemperature approach, the stable isotope geochemistry of soil-formed phyllosilicates continues to be an invaluable proxy system, enhancing our understanding of terrestrial paleoenvironments and paleoclimate.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105417"},"PeriodicalIF":10.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146110675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2026-01-26DOI: 10.1016/j.earscirev.2026.105410
William D. Harcourt , Danni M. Pearce , Wojciech Gajek , Harold Lovell , Erik S. Mannerfelt , Andreas Kääb , Douglas I. Benn , Adrian Luckman , Richard Hann , Jack Kohler , Tazio Strozzi , Rebecca McCerery , Bethan J. Davies
Glacier surges are episodes of significantly increased ice flow due to ice-dynamical feedbacks, and are often repeated in a quasi-periodical manner. Ice mass is redistributed during a surge, which leads to surface lowering at high elevation as ice is transferred down-glacier and thickening nearer the terminus. In this paper, we review different approaches for monitoring and detecting glacier surges in Svalbard, one of the most prominent global clusters of surge-type glaciers. Current surge detection is mainly based upon tracking the speed of glaciers over time, measuring elevation and frontal changes, and more recently automatically detecting surface changes such as increased crevassing. Thermal and hydrological changes near the glacier bed drive surge dynamics and can be measured using geophysical sensors such as ground-penetrating radar (GPR) and seismometers. When glaciers surge, they often produce diagnostic landforms in subglacial and proglacial environments, allowing historical surging to be identified even if surges have not been directly observed.
Through this review, we have compiled an updated database of surge-type glaciers in Svalbard and find that 36% of glaciers display surge-type behaviour, which accounts for 75% of the total glacier area on Svalbard. Only 10% of all glaciers have been directly observed to surge, yet account for 48% of the total glacier area on Svalbard. Svalbard surge-type glaciers have gentler slopes, are generally longer, and extend across a larger elevation range compared to non surge-type glaciers across the archipelago. We find that the behaviour of surge-type glaciers is variable and more closely resembles a continuum from glaciers that do not surge to those which redistribute mass in a single event of strongly enhanced ice flux. We can describe the variability in surge behaviour using the concept of enthalpy and a six-stage surge model that characterises the build-up of energy at the glacier bed driven initially by thermal change and then ice acceleration which is prompted by changes in subglacial hydrology. Observations of glacier surges have improved significantly with routine mapping from satellites such as Sentinel-1, Sentinel-2 and the Landsat satellite series. Furthermore, an increasing number of geophysical measurements is enabling an improved understanding of subglacial processes before, during and after a surge, which is crucial for improving models of surge behaviour. As our observations of surges continue to improve, we expect to uncover new elements and details of surge behaviour, reaffirming the need to rethink the binary classification of glaciers as either ‘surge-type’ or ‘not surge-type’ in Svalbard and across the world.
{"title":"Surging glaciers in Svalbard: Observing their distribution, characteristics and evolution","authors":"William D. Harcourt , Danni M. Pearce , Wojciech Gajek , Harold Lovell , Erik S. Mannerfelt , Andreas Kääb , Douglas I. Benn , Adrian Luckman , Richard Hann , Jack Kohler , Tazio Strozzi , Rebecca McCerery , Bethan J. Davies","doi":"10.1016/j.earscirev.2026.105410","DOIUrl":"10.1016/j.earscirev.2026.105410","url":null,"abstract":"<div><div>Glacier surges are episodes of significantly increased ice flow due to ice-dynamical feedbacks, and are often repeated in a quasi-periodical manner. Ice mass is redistributed during a surge, which leads to surface lowering at high elevation as ice is transferred down-glacier and thickening nearer the terminus. In this paper, we review different approaches for monitoring and detecting glacier surges in Svalbard, one of the most prominent global clusters of surge-type glaciers. Current surge detection is mainly based upon tracking the speed of glaciers over time, measuring elevation and frontal changes, and more recently automatically detecting surface changes such as increased crevassing. Thermal and hydrological changes near the glacier bed drive surge dynamics and can be measured using geophysical sensors such as ground-penetrating radar (GPR) and seismometers. When glaciers surge, they often produce diagnostic landforms in subglacial and proglacial environments, allowing historical surging to be identified even if surges have not been directly observed.</div><div>Through this review, we have compiled an updated database of surge-type glaciers in Svalbard and find that 36% of glaciers display surge-type behaviour, which accounts for 75% of the total glacier area on Svalbard. Only 10% of all glaciers have been directly observed to surge, yet account for 48% of the total glacier area on Svalbard. Svalbard surge-type glaciers have gentler slopes, are generally longer, and extend across a larger elevation range compared to non surge-type glaciers across the archipelago. We find that the behaviour of surge-type glaciers is variable and more closely resembles a continuum from glaciers that do not surge to those which redistribute mass in a single event of strongly enhanced ice flux. We can describe the variability in surge behaviour using the concept of enthalpy and a six-stage surge model that characterises the build-up of energy at the glacier bed driven initially by thermal change and then ice acceleration which is prompted by changes in subglacial hydrology. Observations of glacier surges have improved significantly with routine mapping from satellites such as Sentinel-1, Sentinel-2 and the Landsat satellite series. Furthermore, an increasing number of geophysical measurements is enabling an improved understanding of subglacial processes before, during and after a surge, which is crucial for improving models of surge behaviour. As our observations of surges continue to improve, we expect to uncover new elements and details of surge behaviour, reaffirming the need to rethink the binary classification of glaciers as either ‘surge-type’ or ‘not surge-type’ in Svalbard and across the world.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105410"},"PeriodicalIF":10.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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