Pub Date : 2026-02-10DOI: 10.1016/j.coal.2026.104964
D.A. Bagdonas, R.W. Gregory, C.M. Messa, E.H. Phillips, T.C. Brown
Unconventional geologic sources of rare earth elements, such as those preserved within coal-bearing strata, represent a potential domestic supply of critical minerals. Here we present major and trace element geochemical data from both the coal bed and stratabounding sediments. Representative samples were collected from the Wyodak-Anderson Coal Zone in U.S. Powder River Basin (WY, MT) and then analyzed using inductively coupled plasma mass spectroscopy and optical emission spectroscopy. These chemical analyses show that coal samples collected from multiple locations across the basin host concentrations of rare earth elements plus yttrium above average coal values for the United States. Additionally, these subbituminous coals are anomalously concentrated in CaO relative to coals from other U.S. basins. Total concentrations of rare earth elements and yttrium are highly variable when sampled at different depths within coal beds but show consistent relative enrichment at their margins. Sample locations within the basin and their proximity to bounding highlands appear to show predictable trends in rare earth element variability indicative of geochemical sorting mechanisms through geologic time. This contribution not only indicates an unconventional source of rare earth elements plus yttrium for active coal mines in the Powder River Basin, but also presents pathways for future work to grow our current understanding of this potential resource.
{"title":"Rare earth element occurrence and distribution within the largest U.S. coal resource: Geochemical variability of powder river Basin Coals, Wyoming and Montana","authors":"D.A. Bagdonas, R.W. Gregory, C.M. Messa, E.H. Phillips, T.C. Brown","doi":"10.1016/j.coal.2026.104964","DOIUrl":"https://doi.org/10.1016/j.coal.2026.104964","url":null,"abstract":"Unconventional geologic sources of rare earth elements, such as those preserved within coal-bearing strata, represent a potential domestic supply of critical minerals. Here we present major and trace element geochemical data from both the coal bed and stratabounding sediments. Representative samples were collected from the Wyodak-Anderson Coal Zone in U.S. Powder River Basin (WY, MT) and then analyzed using inductively coupled plasma mass spectroscopy and optical emission spectroscopy. These chemical analyses show that coal samples collected from multiple locations across the basin host concentrations of rare earth elements plus yttrium above average coal values for the United States. Additionally, these subbituminous coals are anomalously concentrated in CaO relative to coals from other U.S. basins. Total concentrations of rare earth elements and yttrium are highly variable when sampled at different depths within coal beds but show consistent relative enrichment at their margins. Sample locations within the basin and their proximity to bounding highlands appear to show predictable trends in rare earth element variability indicative of geochemical sorting mechanisms through geologic time. This contribution not only indicates an unconventional source of rare earth elements plus yttrium for active coal mines in the Powder River Basin, but also presents pathways for future work to grow our current understanding of this potential resource.","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"315 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-04DOI: 10.1016/j.coal.2026.104962
Debora Berti, Anne E. Oberlink, John G. Groppo, Prakash Joshi, Dorin V. Preda, David P. Gamliel, Todd Beers, Michael Schrock, Shelley D. Hopps, Tonya D. Morgan, Bernd Zechmann, James C. Hower
{"title":"Addendum: Electron microbeam investigations of the spent ash from the pilot-scale acid extraction of rare earth elements from a beneficiated Kentucky fly ash (2025, Int. J. Coal Geol. 303, 104738): Further consideration of particle-size reduction from feed to processed fly ash","authors":"Debora Berti, Anne E. Oberlink, John G. Groppo, Prakash Joshi, Dorin V. Preda, David P. Gamliel, Todd Beers, Michael Schrock, Shelley D. Hopps, Tonya D. Morgan, Bernd Zechmann, James C. Hower","doi":"10.1016/j.coal.2026.104962","DOIUrl":"https://doi.org/10.1016/j.coal.2026.104962","url":null,"abstract":"","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"45 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","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.coal.2026.104948
Ibrahim Okunlola , Rona Donahoe , Kalyn Tew , Marcella McIntyre-Redden , Elena Tajuelo Rodriguez
Critical minerals (CM) such as rare earth elements (REE+) and Lithium (Li) are essential to technological innovation, energy transitions, global economic and defense security, necessitating the search for unconventional resources and efficient recovery methods to avert supply chain disruptions. This study evaluates coal-associated sediments (underclay and roof rock) and wastes from the Pennsylvanian Pottsville Formation of the Southern Appalachian Basin (SAB) as potential feedstocks for CM recovery. A total of 34 samples (15 underclays, 12 roof rocks, 5 Acid Mine Drainage (AMD) sludges, and 2 coal mining wastes) were characterized using XRD, XRF, ICP-MS, and μ-XRF analytical methods. The REE+ and Li concentrations of these materials ranged from 46.8 to 334.4 ppm and from 11.1 to 519 ppm, respectively, with one underclay sample (Hendrix 3456) yielding the highest values for both. Bulk mineralogy for all samples was dominated by aluminosilicate clay phases, particularly illite and kaolinite. All samples exhibited REYdef, rel% values >26% and Coutl indices that ranged from 0.69 to 0.94, classifying their REE ore potential as Category II (Promising) as defined by Seredin and Dai (2012). Extractability tests (EPA method 3051 A) yielded low REE+ and Li recoveries, with maximum values of 3.3% and 3.6%, respectively, suggesting associations with resistant minerals like clay and phosphates. Elemental mapping indicates that REE+ is associated with phosphate, whereas statistical analysis suggests that REE+ are associated with aluminosilicates, suggesting heterogeneous associations or minimal phosphate contribution. Li also correlated positively with Al2O3, indicating an aluminosilicate host. This study highlights the potential of coal-associated sediments in the SAB.
{"title":"Evaluation of coal-associated sediments, wastes, and AMD sludge in the Southern Appalachian Basin as feedstock materials for REE and Li recovery","authors":"Ibrahim Okunlola , Rona Donahoe , Kalyn Tew , Marcella McIntyre-Redden , Elena Tajuelo Rodriguez","doi":"10.1016/j.coal.2026.104948","DOIUrl":"10.1016/j.coal.2026.104948","url":null,"abstract":"<div><div>Critical minerals (CM) such as rare earth elements (REE+) and Lithium (Li) are essential to technological innovation, energy transitions, global economic and defense security, necessitating the search for unconventional resources and efficient recovery methods to avert supply chain disruptions. This study evaluates coal-associated sediments (underclay and roof rock) and wastes from the Pennsylvanian Pottsville Formation of the Southern Appalachian Basin (SAB) as potential feedstocks for CM recovery. A total of 34 samples (15 underclays, 12 roof rocks, 5 Acid Mine Drainage (AMD) sludges, and 2 coal mining wastes) were characterized using XRD, XRF, ICP-MS, and μ-XRF analytical methods. The REE+ and Li concentrations of these materials ranged from 46.8 to 334.4 ppm and from 11.1 to 519 ppm, respectively, with one underclay sample (Hendrix 3456) yielding the highest values for both. Bulk mineralogy for all samples was dominated by aluminosilicate clay phases, particularly illite and kaolinite. All samples exhibited REY<sub>def, rel%</sub> values >26% and C<sub>outl</sub> indices that ranged from 0.69 to 0.94, classifying their REE ore potential as Category II (Promising) as defined by <span><span>Seredin and Dai (2012)</span></span>. Extractability tests (EPA method 3051 A) yielded low REE+ and Li recoveries, with maximum values of 3.3% and 3.6%, respectively, suggesting associations with resistant minerals like clay and phosphates. Elemental mapping indicates that REE+ is associated with phosphate, whereas statistical analysis suggests that REE+ are associated with aluminosilicates, suggesting heterogeneous associations or minimal phosphate contribution. Li also correlated positively with Al<sub>2</sub>O<sub>3,</sub> indicating an aluminosilicate host. This study highlights the potential of coal-associated sediments in the SAB.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"316 ","pages":"Article 104948"},"PeriodicalIF":5.7,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146089707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-28DOI: 10.1016/j.coal.2026.104951
Mengdi Sun , Qamar Yasin , Eshimiakhe Daniel , Ghulam Mohyuddin Sohail , Atif Ismail , Bo Liu , David A. Wood
Three-dimensional (3D) digital rock reconstruction, image resolution enhancement, pore network segmentation, and porosity prediction are fundamental to advancing digital rock physics. This study introduces a deep learning framework, Swin-UNETR, based on the Swin Transformer. It is a hybrid architecture that integrates Swin Transformer attention with the U-Net decoder for automated pore network segmentation and connectivity analysis from computed tomography (CT) images. The framework addresses key limitations of traditional Vision Transformers, particularly for heterogeneous low-permeability rocks. Furthermore, to address dataset scarcity, a generative adversarial network (GAN) was used to generate synthetic digital cores. This enhancement contributed to improved class balance and diversity. A comparative evaluation reveals that Swin-UNETR achieved a higher Dice score and improved porosity estimation compared to TransUNet on the same dataset. Cross-domain validation using coal and shale samples from the Longmaxi Formation in the Sichuan Basin of China confirmed strong generalization across lithologies and imaging conditions. In addition, the workflow was extended and applied to predict water distribution and wetting domains in shale for remaining gas recovery. This leveraged grayscale features from two-dimensional (2D) CT images to map the presence of fluid. The results correlated with cryo-SEM measurements, validating its physical interpretability. The 3D volumetric reconstructions revealed complex pore connectivity patterns that were invisible in 2D analysis, enabling a more robust characterization of fluid transport pathways. The proposed Swin-UNETR framework established a new paradigm for digital rock physics, with applications to coal and hydrocarbon flow modeling.
{"title":"Swin-UNETR: A transformer-based model for 3D pore network segmentation in low-permeability sedimentary rocks","authors":"Mengdi Sun , Qamar Yasin , Eshimiakhe Daniel , Ghulam Mohyuddin Sohail , Atif Ismail , Bo Liu , David A. Wood","doi":"10.1016/j.coal.2026.104951","DOIUrl":"10.1016/j.coal.2026.104951","url":null,"abstract":"<div><div>Three-dimensional (3D) digital rock reconstruction, image resolution enhancement, pore network segmentation, and porosity prediction are fundamental to advancing digital rock physics. This study introduces a deep learning framework, Swin-UNETR, based on the Swin Transformer. It is a hybrid architecture that integrates Swin Transformer attention with the U-Net decoder for automated pore network segmentation and connectivity analysis from computed tomography (CT) images. The framework addresses key limitations of traditional Vision Transformers, particularly for heterogeneous low-permeability rocks. Furthermore, to address dataset scarcity, a generative adversarial network (GAN) was used to generate synthetic digital cores. This enhancement contributed to improved class balance and diversity. A comparative evaluation reveals that Swin-UNETR achieved a higher Dice score and improved porosity estimation compared to TransUNet on the same dataset. Cross-domain validation using coal and shale samples from the Longmaxi Formation in the Sichuan Basin of China confirmed strong generalization across lithologies and imaging conditions. In addition, the workflow was extended and applied to predict water distribution and wetting domains in shale for remaining gas recovery. This leveraged grayscale features from two-dimensional (2D) CT images to map the presence of fluid. The results correlated with cryo-SEM measurements, validating its physical interpretability. The 3D volumetric reconstructions revealed complex pore connectivity patterns that were invisible in 2D analysis, enabling a more robust characterization of fluid transport pathways. The proposed Swin-UNETR framework established a new paradigm for digital rock physics, with applications to coal and hydrocarbon flow modeling.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"315 ","pages":"Article 104951"},"PeriodicalIF":5.7,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146072696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-27DOI: 10.1016/j.coal.2026.104950
Gaobo Zhao , Deniz Tuncay
Shale roof dominates underground coal mines in the United States, often exhibiting complex failure behaviors due to their inherent anisotropy and brittle nature associated with bedding planes. This review synthesizes recent advancements in understanding the brittle failure mechanisms and reinforcement strategies for the shale roof. The discussion is structured into four key sections: (1) shale and bedding plane characterization, (2) laboratory-scale shale modeling, (3) entry-scale numerical modeling, and (4) shale roof reinforcement. The first section reviews shale composition and bedding structures, emphasizing the limitations of traditional simplifications and the use of advanced methods (e.g., image processing, LiDAR) to extract spatially realistic bedding data. The second section summarizes laboratory-scale mechanical testing and modeling, illustrating the critical role of bedding planes in the brittle response of shale and approaches to model calibration. The third section extends to entry-scale numerical simulations, incorporating in-situ stress, roof sag, and cable loading data to improve model realism. The final section focuses on roof failure modes and support strategies, particularly the use of Ground Reaction Curves (GRCs) and emerging data-driven approaches for support optimization. While significant progress has been made, several key challenges remain, particularly in accurately representing anisotropic failure and integrating diverse data sources. This comprehensive review consolidates existing knowledge and outlines future directions for improving shale roof modeling and support design, contributing to safer and more efficient underground coal mining.
{"title":"Review of brittle failure mechanisms and reinforcement strategies for shale roof in U.S. underground coal mines","authors":"Gaobo Zhao , Deniz Tuncay","doi":"10.1016/j.coal.2026.104950","DOIUrl":"10.1016/j.coal.2026.104950","url":null,"abstract":"<div><div>Shale roof dominates underground coal mines in the United States, often exhibiting complex failure behaviors due to their inherent anisotropy and brittle nature associated with bedding planes. This review synthesizes recent advancements in understanding the brittle failure mechanisms and reinforcement strategies for the shale roof. The discussion is structured into four key sections: (1) shale and bedding plane characterization, (2) laboratory-scale shale modeling, (3) entry-scale numerical modeling, and (4) shale roof reinforcement. The first section reviews shale composition and bedding structures, emphasizing the limitations of traditional simplifications and the use of advanced methods (e.g., image processing, LiDAR) to extract spatially realistic bedding data. The second section summarizes laboratory-scale mechanical testing and modeling, illustrating the critical role of bedding planes in the brittle response of shale and approaches to model calibration. The third section extends to entry-scale numerical simulations, incorporating in-situ stress, roof sag, and cable loading data to improve model realism. The final section focuses on roof failure modes and support strategies, particularly the use of Ground Reaction Curves (GRCs) and emerging data-driven approaches for support optimization. While significant progress has been made, several key challenges remain, particularly in accurately representing anisotropic failure and integrating diverse data sources. This comprehensive review consolidates existing knowledge and outlines future directions for improving shale roof modeling and support design, contributing to safer and more efficient underground coal mining.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"315 ","pages":"Article 104950"},"PeriodicalIF":5.7,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146072695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Permanently storing CO2 in geological formations is a critical strategy for reducing carbon emissions. Coal reservoirs are a particularly promising option, as injecting CO2 into coal seams enables enhanced coalbed methane (ECBM) recovery by displacing CH4, offering combined economic and environmental benefits. Micropores serve as the primary spaces for CO2 storage and CH4 displacement, with various functional groups on their surfaces providing the driving force for gas adsorption. Coal exhibits a higher adsorption affinity for CO2 than for CH4. The injected CO2 effectively displaces pre-adsorbed CH4 molecules through competitive adsorption. As CH4 desorbs, the stronger interaction between coal macromolecules and CO2 induces more significant structural deformation in the coal macromolecules This deformation subsequently alters the micropore characteristics. Given the high heterogeneity of coal, which varies greatly in coal rank and maceral composition, the resulting macromolecular and micropore structures ultimately govern the CO2 storage capacity and CH4 displacement efficiency. Therefore, a fundamental investigation into the response characteristics and interaction mechanisms of coal macromolecules and micropores during CO2-ECBM processes is crucial for understanding the phenomena of matrix deformation and the underlying adsorption-storage behavior.
{"title":"Responses of coal macromolecules and micropores to CO2 injection and their implications for ECBM: A review","authors":"Jianxin Li, Jienan Pan, Songhang Zhang, Mengyuan Zhang, Kai Wang, Quanlin Hou","doi":"10.1016/j.coal.2026.104949","DOIUrl":"https://doi.org/10.1016/j.coal.2026.104949","url":null,"abstract":"Permanently storing CO<ce:inf loc=\"post\">2</ce:inf> in geological formations is a critical strategy for reducing carbon emissions. Coal reservoirs are a particularly promising option, as injecting CO<ce:inf loc=\"post\">2</ce:inf> into coal seams enables enhanced coalbed methane (ECBM) recovery by displacing CH<ce:inf loc=\"post\">4</ce:inf>, offering combined economic and environmental benefits. Micropores serve as the primary spaces for CO<ce:inf loc=\"post\">2</ce:inf> storage and CH<ce:inf loc=\"post\">4</ce:inf> displacement, with various functional groups on their surfaces providing the driving force for gas adsorption. Coal exhibits a higher adsorption affinity for CO<ce:inf loc=\"post\">2</ce:inf> than for CH<ce:inf loc=\"post\">4</ce:inf>. The injected CO<ce:inf loc=\"post\">2</ce:inf> effectively displaces pre-adsorbed CH<ce:inf loc=\"post\">4</ce:inf> molecules through competitive adsorption. As CH<ce:inf loc=\"post\">4</ce:inf> desorbs, the stronger interaction between coal macromolecules and CO<ce:inf loc=\"post\">2</ce:inf> induces more significant structural deformation in the coal macromolecules This deformation subsequently alters the micropore characteristics. Given the high heterogeneity of coal, which varies greatly in coal rank and maceral composition, the resulting macromolecular and micropore structures ultimately govern the CO<ce:inf loc=\"post\">2</ce:inf> storage capacity and CH<ce:inf loc=\"post\">4</ce:inf> displacement efficiency. Therefore, a fundamental investigation into the response characteristics and interaction mechanisms of coal macromolecules and micropores during CO<ce:inf loc=\"post\">2</ce:inf>-ECBM processes is crucial for understanding the phenomena of matrix deformation and the underlying adsorption-storage behavior.","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"185 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-20DOI: 10.1016/j.coal.2026.104946
Yun Jiang , Zhaoyu Yang , Jianqiang Wang , Zhilei Hao , Gengshun Yao , Hui Xue , Dongdong Zhang , Chao Liang , Heng Peng , Nan Du , Chiyang Liu
The deep-seated processes in the Earth's interior significantly influence surficial geological systems by transporting energy and matter upwards, with volcanic and hydrothermal activities being intrinsically linked to tectonic dynamics. However, the mechanisms by which volcanism and hydrothermal circulation regulate sedimentary environments and organic carbon enrichment remain insufficiently constrained. In this study, we investigated fully cored scientific drillholes from a deep-lacustrine depocenter in the southeastern Ordos Basin, obtained by high-resolution continuous sampling of the Chang 73 sub-member of the Yanchang Formation. Integrated zircon UPb geochronology, petrography, and multiparameter geochemical analyses identified three distinct sedimentary end-members based on Zr/Al and (Fe + Mn)/Ti ratios: Non-hydrotherma/lvolcanic activity (NHV), hydrothermal-dominated activity (HA), and volcanism-dominated activity (VA). Paleoclimate reconstruction reveals warm-humid conditions during HA deposition, contrasting with aridification under weak VA activity. Redox conditions evolve from anoxic–sulfidic in HA-type intervals to predominantly oxic in NHV-type intervals, while paleoproductivity decreases from exceptionally high values in HA-type deposits to much lower levels in NHV-type deposits. The presence of sphalerite-Ag-pyrite hydrothermal assemblages and seismites (e.g., sandstone dikes, mud-chip rip-ups) confirms syndepositional tectonic activity. Hydrothermally derived elements (Fe, Cu, U, Mo) enhanced organic enrichment through nutrient-driven productivity blooms and sulfidic preservation conditions created by reduced sulfides. Consequently, HA-type shales exhibit consistently high total organic carbon (TOC) content (>6%), with peak values reaching 34%. This supernormal enrichment is primarily attributed to deep-seated hydrothermal activity, as extreme TOC concentrations show a direct correlation with hydrothermal intensity, which sustains organic matter preservation. On this basis, and distinguishing between hydrothermal and volcanic controls, we propose that the subduction-induced extensional setting beneath the South China Block created a tectonic regime with frequent seismicity and intense deep-seated processes, thereby giving rise to a hydrothermal–tectonic enrichment model for anomalous organic-matter accumulation in the Ordos Basin.
地球内部的深层过程通过向上输送能量和物质对地表地质系统产生重大影响，火山和热液活动与构造动力学有着内在联系。然而，火山作用和热液循环调节沉积环境和有机碳富集的机制尚不明确。在这项研究中，我们对鄂尔多斯盆地东南部深湖沉积中心的全芯科学钻孔进行了研究，这些钻孔是通过延长组长73亚段的高分辨率连续采样获得的。综合锆石UPb地质年代学、岩石学和多参数地球化学分析，根据Zr/Al和(Fe + Mn)/Ti比值确定了三个不同的沉积端元：非热液/火山活动（NHV）、热液主导活动（HA）和火山主导活动（VA）。古气候重建揭示了HA沉积时期的温暖湿润环境，与弱VA活动下的干旱化形成对比。氧化还原条件由ha型层段的缺氧-硫化物条件演变为nhv型层段的主要氧化条件，而古生产力则从ha型矿床的异常高值下降到nhv型矿床的低水平。闪锌矿-银-黄铁矿热液组合和震积岩（如砂岩岩脉、泥屑碎裂）的存在证实了同沉积构造活动。水热衍生元素（Fe, Cu， U, Mo）通过营养驱动的生产力华和硫化物还原产生的硫化物保存条件增强了有机富集。因此，ha型页岩的总有机碳（TOC）含量一直较高（6%），最高可达34%。这种异常富集主要归因于深部热液活动，极端TOC浓度与热液强度直接相关，从而维持了有机质的保存。在此基础上，区分热液和火山的控制作用，提出华南地块俯冲诱发的伸展环境形成了一个地震活动频繁、深部作用强烈的构造环境，从而形成了鄂尔多斯盆地异常有机质富集的热液-构造富集模式。
{"title":"Hydrothermal activity control on the Mid-Triassic palaeoenvironmental evolution and organic matter enrichment mechanisms in the Ordos Basin, North China Craton","authors":"Yun Jiang , Zhaoyu Yang , Jianqiang Wang , Zhilei Hao , Gengshun Yao , Hui Xue , Dongdong Zhang , Chao Liang , Heng Peng , Nan Du , Chiyang Liu","doi":"10.1016/j.coal.2026.104946","DOIUrl":"10.1016/j.coal.2026.104946","url":null,"abstract":"<div><div>The deep-seated processes in the Earth's interior significantly influence surficial geological systems by transporting energy and matter upwards, with volcanic and hydrothermal activities being intrinsically linked to tectonic dynamics. However, the mechanisms by which volcanism and hydrothermal circulation regulate sedimentary environments and organic carbon enrichment remain insufficiently constrained. In this study, we investigated fully cored scientific drillholes from a deep-lacustrine depocenter in the southeastern Ordos Basin, obtained by high-resolution continuous sampling of the Chang 7<sub>3</sub> sub-member of the Yanchang Formation. Integrated zircon U<img>Pb geochronology, petrography, and multiparameter geochemical analyses identified three distinct sedimentary end-members based on Zr/Al and (Fe + Mn)/Ti ratios: Non-hydrotherma/lvolcanic activity (NHV), hydrothermal-dominated activity (HA), and volcanism-dominated activity (VA). Paleoclimate reconstruction reveals warm-humid conditions during HA deposition, contrasting with aridification under weak VA activity. Redox conditions evolve from anoxic–sulfidic in HA-type intervals to predominantly oxic in NHV-type intervals, while paleoproductivity decreases from exceptionally high values in HA-type deposits to much lower levels in NHV-type deposits. The presence of sphalerite-Ag-pyrite hydrothermal assemblages and seismites (e.g., sandstone dikes, mud-chip rip-ups) confirms syndepositional tectonic activity. Hydrothermally derived elements (Fe, Cu, U, Mo) enhanced organic enrichment through nutrient-driven productivity blooms and sulfidic preservation conditions created by reduced sulfides. Consequently, HA-type shales exhibit consistently high total organic carbon (TOC) content (>6%), with peak values reaching 34%. This supernormal enrichment is primarily attributed to deep-seated hydrothermal activity, as extreme TOC concentrations show a direct correlation with hydrothermal intensity, which sustains organic matter preservation. On this basis, and distinguishing between hydrothermal and volcanic controls, we propose that the subduction-induced extensional setting beneath the South China Block created a tectonic regime with frequent seismicity and intense deep-seated processes, thereby giving rise to a hydrothermal–tectonic enrichment model for anomalous organic-matter accumulation in the Ordos Basin.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"315 ","pages":"Article 104946"},"PeriodicalIF":5.7,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146015020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-19DOI: 10.1016/j.coal.2026.104947
Wenxin Hu , Qingyong Luo , Jianfa Chen , Linhao Fang , Man Lu , Medet Junussov , Tao Du , Xintong Liu , Xiaohang Pan , Gui Wang , Fangchao Yan
Wildfires play a pivotal role in shaping Earth's ecosystems and provide key insights into interactions among the environment, climate and vegetation dynamics. The Triassic–Jurassic (T–J) transition saw a notable increase in wildfire activities, largely attributed to climate shifts and intensified greenhouse effects associated with the Central Atlantic Magmatic Province eruptions (CAMP). However, direct comparisons between volcanic activity and wildfire patterns at high paleolatitude during the T–J transition remain limited. Here, we reconstruct co-temporal changes in wildfire activity and volcanism in the Haojiagou section in the Junggar Basin of northwestern China, a high-paleolatitude region (∼70°N), using charcoal abundance, combined with previously published pyrogenic polycyclic aromatic hydrocarbons (PAHs), palynology, mercury/total organic carbon (Hg/TOC), and Chemical Index of Alteration (CIA). High contents of inertinites were observed in the samples, which indicates the occurrence of extensive wildfires during the T–J transition. The overall low inertinite reflectance and the low coronene index values in the samples suggest the wildfires were primarily low-temperature fires, ranging from 330 °C to 446 °C, with only minor occurrences of small-scale high-temperature fire (> 559 °C). Additionally, our findings reveal that peaks in wildfire frequency closely correspond to volcanic events, climate fluctuations and shifts in vegetation, inferring that volcanic activity drove intense wildfires by altering climate and vegetation. This heightened wildfire activity in response to climate warming highlights the increasing wildfire risk associated with current human-induced climatic change.
{"title":"Intensified wildfire activity due to volcanism across the Triassic-Jurassic boundary in northwestern China","authors":"Wenxin Hu , Qingyong Luo , Jianfa Chen , Linhao Fang , Man Lu , Medet Junussov , Tao Du , Xintong Liu , Xiaohang Pan , Gui Wang , Fangchao Yan","doi":"10.1016/j.coal.2026.104947","DOIUrl":"10.1016/j.coal.2026.104947","url":null,"abstract":"<div><div>Wildfires play a pivotal role in shaping Earth's ecosystems and provide key insights into interactions among the environment, climate and vegetation dynamics. The Triassic–Jurassic (T–J) transition saw a notable increase in wildfire activities, largely attributed to climate shifts and intensified greenhouse effects associated with the Central Atlantic Magmatic Province eruptions (CAMP). However, direct comparisons between volcanic activity and wildfire patterns at high paleolatitude during the T–J transition remain limited. Here, we reconstruct co-temporal changes in wildfire activity and volcanism in the Haojiagou section in the Junggar Basin of northwestern China, a high-paleolatitude region (∼70°N), using charcoal abundance, combined with previously published pyrogenic polycyclic aromatic hydrocarbons (PAHs), palynology, mercury/total organic carbon (Hg/TOC), and Chemical Index of Alteration (CIA). High contents of inertinites were observed in the samples, which indicates the occurrence of extensive wildfires during the T–J transition. The overall low inertinite reflectance and the low coronene index values in the samples suggest the wildfires were primarily low-temperature fires, ranging from 330 °C to 446 °C, with only minor occurrences of small-scale high-temperature fire (> 559 °C). Additionally, our findings reveal that peaks in wildfire frequency closely correspond to volcanic events, climate fluctuations and shifts in vegetation, inferring that volcanic activity drove intense wildfires by altering climate and vegetation. This heightened wildfire activity in response to climate warming highlights the increasing wildfire risk associated with current human-induced climatic change.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"315 ","pages":"Article 104947"},"PeriodicalIF":5.7,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146001417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-15DOI: 10.1016/j.coal.2026.104945
Jorge Eliecer Mariño-Martinez , Tim A. Moore , Juan Sebastian Gomez-Neita
Coalbed methane (CBM) has garnered growing attention in Colombia due to declining conventional energy resources and reserves, persistent mining accidents caused by methane explosions, and climate regulations aimed at reducing greenhouse gas (GHG) emissions. This study provides a review of the current status of CBM in Colombia, synthesizing geological, geochemical, and technical data to assess its development potential. Despite the significant coal reserves of Colombia, early CBM resource estimates were overly optimistic. Updated evaluations reveal that most coal seams exhibit low gas contents (<200 ft3/ton - 5.66 m3/ton), having gas saturations typically less than 50%. This level of gas content poses particular challenges for commercial development. In Colombia, four provinces or coal zones—Cundinamarca, Boyacá, Cesar, and La Guajira—show localized potential, with some samples exceeding 300 ft3/ton. However, reservoir modeling, particularly from the Umbita-Chinavita area (Boyacá), demonstrates that low permeability (<10 mD), thin and discontinuous coalbeds, and structural complexity may inhibit development. The gas quality in these areas also varies, with a methane content averaging 75%, which also places additional pressure on commerciality. Isotopic and hydrogeological analyses suggest a predominantly biogenic origin of methane, often linked to meteoric recharge of the aquifers. Despite technical promise, development faces significant barriers, including inconsistent laboratory standards for existing historical data, a lack of clear legal frameworks, insufficient infrastructure, and limited investor interest and research. Regulatory and institutional fragmentation between coal and gas authorities further complicates the management of CBM resources. To unlock the CBM potential, Colombia must implement standardized exploration practices, develop robust incentive structures, and conduct comprehensive feasibility studies incorporating desorption, adsorption, and isotopic data. This work concludes that while Colombia possesses notable CBM resources, substantial technical, economic, and regulatory challenges must be overcome before near-term commercial production can be realized. The findings provide a foundation for future exploration, policy reform, and sustainable energy strategies aligned with national safety and environmental goals.
{"title":"Coal bed gas in Colombia: Current status","authors":"Jorge Eliecer Mariño-Martinez , Tim A. Moore , Juan Sebastian Gomez-Neita","doi":"10.1016/j.coal.2026.104945","DOIUrl":"10.1016/j.coal.2026.104945","url":null,"abstract":"<div><div>Coalbed methane (CBM) has garnered growing attention in Colombia due to declining conventional energy resources and reserves, persistent mining accidents caused by methane explosions, and climate regulations aimed at reducing greenhouse gas (GHG) emissions. This study provides a review of the current status of CBM in Colombia, synthesizing geological, geochemical, and technical data to assess its development potential. Despite the significant coal reserves of Colombia, early CBM resource estimates were overly optimistic. Updated evaluations reveal that most coal seams exhibit low gas contents (<200 ft<sup>3</sup>/ton - 5.66 m<sup>3</sup>/ton), having gas saturations typically less than 50%. This level of gas content poses particular challenges for commercial development. In Colombia, four provinces or coal zones—Cundinamarca, Boyacá, Cesar, and La Guajira—show localized potential, with some samples exceeding 300 ft<sup>3</sup>/ton. However, reservoir modeling, particularly from the Umbita-Chinavita area (Boyacá), demonstrates that low permeability (<10 mD), thin and discontinuous coalbeds, and structural complexity may inhibit development. The gas quality in these areas also varies, with a methane content averaging 75%, which also places additional pressure on commerciality. Isotopic and hydrogeological analyses suggest a predominantly biogenic origin of methane, often linked to meteoric recharge of the aquifers. Despite technical promise, development faces significant barriers, including inconsistent laboratory standards for existing historical data, a lack of clear legal frameworks, insufficient infrastructure, and limited investor interest and research. Regulatory and institutional fragmentation between coal and gas authorities further complicates the management of CBM resources. To unlock the CBM potential, Colombia must implement standardized exploration practices, develop robust incentive structures, and conduct comprehensive feasibility studies incorporating desorption, adsorption, and isotopic data. This work concludes that while Colombia possesses notable CBM resources, substantial technical, economic, and regulatory challenges must be overcome before near-term commercial production can be realized. The findings provide a foundation for future exploration, policy reform, and sustainable energy strategies aligned with national safety and environmental goals.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"316 ","pages":"Article 104945"},"PeriodicalIF":5.7,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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