Pub Date : 2026-02-09DOI: 10.1016/j.earscirev.2026.105416
Lei Zhao, Qiang Wei, David French, James C. Hower, Ian T. Graham, Gregory C. Smith
{"title":"The influence of terrestrial plants on the enrichment of critical metals in coal","authors":"Lei Zhao, Qiang Wei, David French, James C. Hower, Ian T. Graham, Gregory C. Smith","doi":"10.1016/j.earscirev.2026.105416","DOIUrl":"https://doi.org/10.1016/j.earscirev.2026.105416","url":null,"abstract":"","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"1 1","pages":""},"PeriodicalIF":12.1,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153131","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}
Organic-inorganic interactions are ubiquitous within organic-rich shale systems and exert a pivotal control on the formation and evolution of integrated shale source-reservoir systems. However, a comprehensive and in-depth understanding of the microscale physicochemical processes underpinning these interactions in shale source-reservoir systems remains lacking to date. This review provides a holistic elaboration of the evolutionary processes of shale source-reservoir systems and systematically synthesizes the diverse pathways of organic-inorganic interactions in organic-rich shales. At the macroscale, climatic conditions and provenance jointly constrain the mineral composition during sedimentation. At the microscale, minerals exhibit selective adsorption characteristics toward organic matter (OM) owing to differences in adsorption mechanisms, which directly modulates the abundance and type of OM in sediments. The physical protection afforded by mineral pores mitigates the oxidation of organic carbon and regulates the overall reactivity and burial efficiency of organic carbon. During the thermal evolution stage, minerals and transition metals significantly accelerate kerogen cracking by reducing reaction activation energy, providing proton donors, or facilitating free radical reactions. Notably, under high-temperature conditions, inorganic-derived hydrogen and oxygen drive extensive organic-inorganic interactions, which exert a profound impact on deep hydrocarbon generation potential, natural gas isotopic compositions, and the upper limit of secondary pore formation. The generation of organic acids fuels pore evolution in shale reservoirs; secondary pores formed via mineral dissolution alter the pore characteristics and heterogeneity of shales. Ions released during dissolution drive mineral transformation and authigenic mineral precipitation. Coupled with the involvement of exogenous hydrogen, the sustained acid generation from hydrocarbon pyrolysis in deep reservoirs perpetuates this pore-forming effect. During the mature to high-maturity stages, organic-inorganic interactions exert a prominent influence on pore formation and heterogeneity. Even at higher thermal maturity levels, these interactions persist due to the participation of inorganic hydrogen and oxygen, yet the depth threshold of organic-inorganic interactions remains undefined. The formation of integrated shale source-reservoir systems is a complex, dynamic evolutionary process involving the coupling of multiple components, stages, and mechanisms. Focusing on the regulatory mechanisms of organic-inorganic interactions in integrated shale source-reservoir systems, this review synthesizes key scientific issues including mineral - and transition metal compound-catalyzed hydrocarbon generation, hydrocarbon evolution involving multi-source hydrogen, and pore development under varying maturity conditions. It aims to provide theoretical support and scientific guidance for the exploration and
{"title":"Impact of organic-inorganic interactions on shale source-reservoir systems","authors":"Yue Huang, Zhenkai Huang, Xi Li, Guangyou Zhu, Zhiyuan Lu, Siyu Chen, Ruilin Wang, Wanyan Lan, Jiezhi Zhang","doi":"10.1016/j.earscirev.2026.105422","DOIUrl":"https://doi.org/10.1016/j.earscirev.2026.105422","url":null,"abstract":"Organic-inorganic interactions are ubiquitous within organic-rich shale systems and exert a pivotal control on the formation and evolution of integrated shale source-reservoir systems. However, a comprehensive and in-depth understanding of the microscale physicochemical processes underpinning these interactions in shale source-reservoir systems remains lacking to date. This review provides a holistic elaboration of the evolutionary processes of shale source-reservoir systems and systematically synthesizes the diverse pathways of organic-inorganic interactions in organic-rich shales. At the macroscale, climatic conditions and provenance jointly constrain the mineral composition during sedimentation. At the microscale, minerals exhibit selective adsorption characteristics toward organic matter (OM) owing to differences in adsorption mechanisms, which directly modulates the abundance and type of OM in sediments. The physical protection afforded by mineral pores mitigates the oxidation of organic carbon and regulates the overall reactivity and burial efficiency of organic carbon. During the thermal evolution stage, minerals and transition metals significantly accelerate kerogen cracking by reducing reaction activation energy, providing proton donors, or facilitating free radical reactions. Notably, under high-temperature conditions, inorganic-derived hydrogen and oxygen drive extensive organic-inorganic interactions, which exert a profound impact on deep hydrocarbon generation potential, natural gas isotopic compositions, and the upper limit of secondary pore formation. The generation of organic acids fuels pore evolution in shale reservoirs; secondary pores formed via mineral dissolution alter the pore characteristics and heterogeneity of shales. Ions released during dissolution drive mineral transformation and authigenic mineral precipitation. Coupled with the involvement of exogenous hydrogen, the sustained acid generation from hydrocarbon pyrolysis in deep reservoirs perpetuates this pore-forming effect. During the mature to high-maturity stages, organic-inorganic interactions exert a prominent influence on pore formation and heterogeneity. Even at higher thermal maturity levels, these interactions persist due to the participation of inorganic hydrogen and oxygen, yet the depth threshold of organic-inorganic interactions remains undefined. The formation of integrated shale source-reservoir systems is a complex, dynamic evolutionary process involving the coupling of multiple components, stages, and mechanisms. Focusing on the regulatory mechanisms of organic-inorganic interactions in integrated shale source-reservoir systems, this review synthesizes key scientific issues including mineral - and transition metal compound-catalyzed hydrocarbon generation, hydrocarbon evolution involving multi-source hydrogen, and pore development under varying maturity conditions. It aims to provide theoretical support and scientific guidance for the exploration and","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"9 1","pages":""},"PeriodicalIF":12.1,"publicationDate":"2026-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146322","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 : 2026-02-06DOI: 10.1016/j.earscirev.2026.105420
X. Rui , D.S. Stamps
Previous studies have constrained fault slip rates and crustal block geometries of the Southeastern Tibetan Plateau (SETP) with contradictory results due to complex geodynamics and deformation patterns as well as subjective choices of crustal block boundaries. In this work, we address the issue of uncertain crustal block geometries by employing an unsupervised machine learning Euler pole clustering algorithm that automatically resolves regions that behave as rigid blocks (clusters) rotating on a sphere using GNSS velocity vectors. Optimal clustering results, determined by F-test and Euler-vector (angular velocity vector) overlap analyses, indicate 4 elongated crustal blocks exist in the SETP that are approximately parallel and delineated by a set of arcuate sinistral-slip faults. Our clustering results redefine the first-order kinematics of the SETP region with new crustal block definitions that elucidate the dominance of sinistral-slip faults.
{"title":"Euler-pole clustering of GNSS velocities using unsupervised machine learning in the Southeastern Tibetan Plateau: Crustal block identification and the dominance of sinistral-slip faults","authors":"X. Rui , D.S. Stamps","doi":"10.1016/j.earscirev.2026.105420","DOIUrl":"10.1016/j.earscirev.2026.105420","url":null,"abstract":"<div><div>Previous studies have constrained fault slip rates and crustal block geometries of the Southeastern Tibetan Plateau (SETP) with contradictory results due to complex geodynamics and deformation patterns as well as subjective choices of crustal block boundaries. In this work, we address the issue of uncertain crustal block geometries by employing an unsupervised machine learning Euler pole clustering algorithm that automatically resolves regions that behave as rigid blocks (clusters) rotating on a sphere using GNSS velocity vectors. Optimal clustering results, determined by F-test and Euler-vector (angular velocity vector) overlap analyses, indicate 4 elongated crustal blocks exist in the SETP that are approximately parallel and delineated by a set of arcuate sinistral-slip faults. Our clustering results redefine the first-order kinematics of the SETP region with new crustal block definitions that elucidate the dominance of sinistral-slip faults.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"276 ","pages":"Article 105420"},"PeriodicalIF":10.0,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135068","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 : 2026-02-05DOI: 10.1016/j.earscirev.2026.105418
Xiuling Ren , Fujun Niu , Degou Cai , Jing Luo , Qihao Yu , Minghao Liu , Guoan Yin , Zeyong Gao
Soil frost heave seriously threatens the stability of engineering structures and the normal operation of major infrastructures in cold regions. This paper aims to synthesize the development and state of the art in moisture migration, cryostructure, soil frost heave, as well as their underlying micro-mechanisms, impacting factors and simulation models. First, we provide a brief review on moisture migration, cryostructure and soil frost heave. Second, some microstructural experiments incorporate X-ray computed tomography (X-CT), scanning electron microscope (SEM), and nuclear magnetic resonance (NMR) were reviewed to elucidate the underlying micro-mechanisms. Third, impacting factors for soil frost heave covering soil intrinsic properties, testing and environmental conditions were summarized. Moreover, numerous frost heave models involving theoretical, numerical, and machine learning (ML) models were discussed. Then, we point out some limits and identify the direction of future efforts. Despite advances achieved through decades of researches, some issues remain in the research on the frost heave of the coarse-grained soils, and soils with admixtures. To solve these problems by performing one-dimensional (1D) freezing and microstructural experiments on these soils considering these factors, and establishing novel frost heave models. Overall, this review will provide significant references for further research on soil frost heave, and an important theoretical guidance for the prevention and control of the frost heave distresses of infrastructures.
{"title":"Moisture migration, ice lenses and frost heave characteristics of soils under one-dimensional freezing action: A critical literature review","authors":"Xiuling Ren , Fujun Niu , Degou Cai , Jing Luo , Qihao Yu , Minghao Liu , Guoan Yin , Zeyong Gao","doi":"10.1016/j.earscirev.2026.105418","DOIUrl":"10.1016/j.earscirev.2026.105418","url":null,"abstract":"<div><div>Soil frost heave seriously threatens the stability of engineering structures and the normal operation of major infrastructures in cold regions. This paper aims to synthesize the development and state of the art in moisture migration, cryostructure, soil frost heave, as well as their underlying micro-mechanisms, impacting factors and simulation models. First, we provide a brief review on moisture migration, cryostructure and soil frost heave. Second, some microstructural experiments incorporate X-ray computed tomography (X-CT), scanning electron microscope (SEM), and nuclear magnetic resonance (NMR) were reviewed to elucidate the underlying micro-mechanisms. Third, impacting factors for soil frost heave covering soil intrinsic properties, testing and environmental conditions were summarized. Moreover, numerous frost heave models involving theoretical, numerical, and machine learning (ML) models were discussed. Then, we point out some limits and identify the direction of future efforts. Despite advances achieved through decades of researches, some issues remain in the research on the frost heave of the coarse-grained soils, and soils with admixtures. To solve these problems by performing one-dimensional (1D) freezing and microstructural experiments on these soils considering these factors, and establishing novel frost heave models. Overall, this review will provide significant references for further research on soil frost heave, and an important theoretical guidance for the prevention and control of the frost heave distresses of infrastructures.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"276 ","pages":"Article 105418"},"PeriodicalIF":10.0,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135070","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 : 2026-02-02DOI: 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":"2026-02-02","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 : 2026-02-02DOI: 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":"2026-02-02","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 : 2026-02-01DOI: 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":"2026-02-01","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 : 2026-01-31DOI: 10.1016/j.earscirev.2026.105415
Bo Liu , Qamar Yasin , Eshimiakhe Daniel , Ghulam Mohyuddin Sohail , Mengdi Sun , David A. Wood
Characterization of microfracture systems and nanopore networks in organic-rich shales is critical for understanding fluid transport, hydrocarbon storage capacity, and the feasibility of carbon dioxide (CO₂) sequestration. However, the inherent heterogeneity, complex morphology, and nano-scale features of shale microstructures present significant challenges for conventional image segmentation techniques. This study reviews and evaluates the performance of state-of-the-art deep learning architectures for automated high-precision segmentation of microfractures and pore systems in FIB-SEM images of organic-rich shales. To enhance the generalizability of each model, a hybrid training dataset comprising 5,000 real and 5,000 synthetically generated GAN-based FIB-SEM images is evaluated. Quantitative analysis reveals that Kite-Net (KiU-Net) outperforms both Swin UNET Transformers (Swin-UNETR) and Attention U-Net, achieving an overall segmentation accuracy of 94%, precision of 94%, and recall of 93%. Notably, KiU-Net excels in accurately delineating microfractures and complex pore geometries within kerogen-rich matrices. Based on KiU-Net's superior validation performance compared to the two other deep learning models, we employed it to segment 3D FIB-SEM image stacks, enabling volumetric reconstruction and analysis of pore connectivity. Results revealed marked morphological distinctions between organic and inorganic pores, with over 94% of pores existing as isolated, non-percolating clusters, a finding consistent with prior geological investigations. Cross-validation considering various shales and coals further validates the model's effectiveness across a range of lithofacies. Our study presents a scalable deep learning framework for analyzing nanoscale shale microstructures from images.
{"title":"Automated characterization of microfracture systems in organic-rich shales and their influence on porosity using convolutional neural networks on FIB-SEM images: A review","authors":"Bo Liu , Qamar Yasin , Eshimiakhe Daniel , Ghulam Mohyuddin Sohail , Mengdi Sun , David A. Wood","doi":"10.1016/j.earscirev.2026.105415","DOIUrl":"10.1016/j.earscirev.2026.105415","url":null,"abstract":"<div><div>Characterization of microfracture systems and nanopore networks in organic-rich shales is critical for understanding fluid transport, hydrocarbon storage capacity, and the feasibility of carbon dioxide (CO₂) sequestration. However, the inherent heterogeneity, complex morphology, and nano-scale features of shale microstructures present significant challenges for conventional image segmentation techniques. This study reviews and evaluates the performance of state-of-the-art deep learning architectures for automated high-precision segmentation of microfractures and pore systems in FIB-SEM images of organic-rich shales. To enhance the generalizability of each model, a hybrid training dataset comprising 5,000 real and 5,000 synthetically generated GAN-based FIB-SEM images is evaluated. Quantitative analysis reveals that Kite-Net (KiU-Net) outperforms both Swin UNET Transformers (Swin-UNETR) and Attention U-Net, achieving an overall segmentation accuracy of 94%, precision of 94%, and recall of 93%. Notably, KiU-Net excels in accurately delineating microfractures and complex pore geometries within kerogen-rich matrices. Based on KiU-Net's superior validation performance compared to the two other deep learning models, we employed it to segment 3D FIB-SEM image stacks, enabling volumetric reconstruction and analysis of pore connectivity. Results revealed marked morphological distinctions between organic and inorganic pores, with over 94% of pores existing as isolated, non-percolating clusters, a finding consistent with prior geological investigations. Cross-validation considering various shales and coals further validates the model's effectiveness across a range of lithofacies. Our study presents a scalable deep learning framework for analyzing nanoscale shale microstructures from images.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105415"},"PeriodicalIF":10.0,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146095930","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 : 2026-01-30DOI: 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":"2026-01-30","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 : 2026-01-29DOI: 10.1016/j.earscirev.2026.105414
Marta Magán , David J. Sanderson , David C.P. Peacock
Joint networks exhibit a range of geometrical and topological features described by many different parameters. Data were collected using unmanned aerial vehicle images of ten limestone beds in the Lower Liassic rocks of Somerset, SW England, which were analysed using a GIS and relational database. Parameters were measured from digitizing maps and images of joint networks, and investigated using a range of parameters and statistical methods without assigning joints to sets. Geometry is analysed using: rose diagrams and cumulative plots of orientation, trace length statistics, and measures of intensity and block size; with the poly-modal orientation data treated by non-parametric methods (Kuiper tests). Topology is analysed based on the numbers of nodes, branches and regions.
The results show that the networks have similar topology, but have significant variations in intensity, block size and orientation between beds. The within-bed and between-bed variability is evaluated using analysis of variance methods. This allows discussion of stratigraphical and spatial variation, and the evolution of joint networks in multi-bedded sequences. Although bed thickness accounts for some of this variability, long, early formed joints are argued to control much of the network geometry and topology. The methods developed here can be applied directly, or with minor modification, to networks of veins, faults and other structures.
{"title":"Comparison of joint networks in limestones interbedded in shales","authors":"Marta Magán , David J. Sanderson , David C.P. Peacock","doi":"10.1016/j.earscirev.2026.105414","DOIUrl":"10.1016/j.earscirev.2026.105414","url":null,"abstract":"<div><div>Joint networks exhibit a range of geometrical and topological features described by many different parameters. Data were collected using unmanned aerial vehicle images of ten limestone beds in the Lower Liassic rocks of Somerset, SW England, which were analysed using a GIS and relational database. Parameters were measured from digitizing maps and images of joint networks, and investigated using a range of parameters and statistical methods without assigning joints to sets. Geometry is analysed using: rose diagrams and cumulative plots of orientation, trace length statistics, and measures of intensity and block size; with the poly-modal orientation data treated by non-parametric methods (Kuiper tests). Topology is analysed based on the numbers of nodes, branches and regions.</div><div>The results show that the networks have similar topology, but have significant variations in intensity, block size and orientation between beds. The within-bed and between-bed variability is evaluated using analysis of variance methods. This allows discussion of stratigraphical and spatial variation, and the evolution of joint networks in multi-bedded sequences. Although bed thickness accounts for some of this variability, long, early formed joints are argued to control much of the network geometry and topology. The methods developed here can be applied directly, or with minor modification, to networks of veins, faults and other structures.</div></div>","PeriodicalId":11483,"journal":{"name":"Earth-Science Reviews","volume":"275 ","pages":"Article 105414"},"PeriodicalIF":10.0,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146072727","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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