International Journal of Coal Geology最新文献

{"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 ,&nbsp;Rona Donahoe ,&nbsp;Kalyn Tew ,&nbsp;Marcella McIntyre-Redden ,&nbsp;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_{def, rel%} values &gt;26% and C_outl 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 Al₂O_3, 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":"2026-02-28","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}

{"title":"Authigenic mineral growth in sedimentary and metasedimentary rocks enhances the degree of structural order of carbonaceous material","authors":"Sami Nabhan ,&nbsp;Christoph Heubeck ,&nbsp;Don E. Canfield","doi":"10.1016/j.coal.2026.104966","DOIUrl":"10.1016/j.coal.2026.104966","url":null,"abstract":"<div><div>The degree of structural order of carbonaceous matter (CM) in metasedimentary rocks is thought to largely depend on the maximum temperature the host rock experienced. This led to the widespread use of Raman spectroscopy of carbonaceous matter (RSCM) as geothermometer to determine maximum burial or metamorphic temperatures. The analytical certainty of most geothermometers based on RSCM is given as ±30–50 °C and the structural order of CM is often shown to be heterogeneous within individual samples, geological beds and units. To better understand the influence of authigenic mineral growth on CM maturation and heterogeneity we analyzed samples from three Precambrian CM-bearing stratigraphic units. Raman spectroscopic results indicate large heterogeneities in the degree of structural order of CM, resulting in ranges of up to 190 °C in calculated temperature within individual samples. Generally, within each sample, CM within authigenic minerals shows a significantly higher degree of structural order than CM in areas devoid of authigenic minerals. This results in calculated average temperatures from CM within authigenic minerals that are 27–94 °C higher than temperatures calculated from CM in neighboring areas devoid of authigenic minerals. Our results indicate that the structural order of CM within authigenic minerals is significantly enhanced. Thus, geothermometers based on RSCM must be used carefully with a thorough awareness of the petrographic context.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"316 ","pages":"Article 104966"},"PeriodicalIF":5.7,"publicationDate":"2026-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160596","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}

{"title":"Tectonic and climatic controls on organic matter accumulation and redox dynamics in Campanian-Maastrichtian strata of the Abu Tartur Plateau, southern Tethys (Egypt)","authors":"Ahmed Mansour ,&nbsp;Eva Geršlová ,&nbsp;Dominik Vöröš ,&nbsp;Omar Mohamed ,&nbsp;Thomas Gentzis ,&nbsp;Ahmed Ali","doi":"10.1016/j.coal.2026.104967","DOIUrl":"10.1016/j.coal.2026.104967","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Despite widespread organic-rich accumulations in southern Tethyan basins during the Late Cretaceous greenhouse, the relative role of climate-derived weathering, redox regime, paleoproductivity, and regional tectonics in controlling organic matter enrichment and preservation remains poorly constrained. This work investigates how these interacting geological processes governed organic matter richness and redox evolution in Campanian-Maastrichtian strata of the Abu Tartur Plateau, Dakhla Basin (southern Western Desert, Egypt). The study combined bulk-rock elemental and organic geochemical and sedimentological data from phosphates, black and gray shales, limestones, and glauconites of the Phosphate, Liffiya Shale, and Maghrabi Shale members of the Duwi Formation and the overlying Dakhla Formation. Chemical index of alteration (CIA), C-value and other elemental proxies revealed deposition under predominant humid climates and intense continental weathering, interrupted by short-lived arid-semi-arid to semi-humid intervals, corresponding to the development of phosphorite and carbonate beds. These climatic and weathering trends coincide with coeval intervals from the Red Sea and Nile Valley, reflecting the regional geological processes at the near-equatorial southern Tethyan margin during the Campanian-Maastrichtian. Source rock characterization indicates poor to very good with a few intervals of excellent organic matter richness and kerogen Type III with minor Type II. The deposition of the Duwi and Dakhla formations was concurrent with episodic subsidence versus uplift of the Gilf El-Kebir spur and Nubian Swell, consistent with sea-level rise and increased accommodation space and induced upwelling in open shelf settings of the southern Tethys. These conditions governed O&lt;sub&gt;2&lt;/sub&gt; replenishment faster than consumption leading to oxic-suboxic environments dominated by organic-rich deposits via organic matter production under enhanced upwelling than persistent anoxia. Conversely, black shales of the Maghrabi Shale Member were deposited under anoxic settings accompanied by elevated biological productivity. Preferential Mo enrichments in black shales compared to limited enrichments of other redox-sensitive metals suggest the operation of a particulate shuttle during short-term redox fluctuations. The mechanism behind enhanced anoxia included episodes of relative sea-level fall and decreased accommodation space along with regional tectonic uplift of adjacent uplands, resulting in a semi-enclosed basin with restricted circulation that promoted nutrient supply and oxygen depletion, favorable for organic matter preservation. The Dakhla Formation was deposited in similar marine environmental conditions to the Liffiya Shale Member; however, intensified weathering and associated terrigenous supply versus limited biological productivity and well-ventilated water column resulted in a strong dilution of labile organic matter and deposition of organic car","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"316 ","pages":"Article 104967"},"PeriodicalIF":5.7,"publicationDate":"2026-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146172368","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}

{"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 ,&nbsp;R.W. Gregory ,&nbsp;C.M. Messa ,&nbsp;E.H. Phillips ,&nbsp;T.C. Brown","doi":"10.1016/j.coal.2026.104964","DOIUrl":"10.1016/j.coal.2026.104964","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"316 ","pages":"Article 104964"},"PeriodicalIF":5.7,"publicationDate":"2026-02-28","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}

{"title":"Application of statistical methods to evaluate identification credibility of macerals in high-maturity marine shales","authors":"Lin Wei ,&nbsp;Maria Mastalerz ,&nbsp;Jingwen Wang ,&nbsp;Yanan Wang ,&nbsp;Xiaomiao Li ,&nbsp;Xiong Cheng","doi":"10.1016/j.coal.2026.104952","DOIUrl":"10.1016/j.coal.2026.104952","url":null,"abstract":"<div><div>Vitrinite reflectance is a key parameter for thermal maturity assessment in sedimentary basins; however, its application in high-maturity marine shales is complicated by optical convergence between vitrinite and solid bitumen and strong reflectance anisotropy. These factors lead to substantial data dispersion, as highlighted by interlaboratory studies defining the empirical bounds of analytical reproducibility. This study aims to evaluate the internal reliability of reflectance datasets and quantify uncertainty in maturity interpretations.</div><div>We present an integrated statistical framework combining the analytical hierarchy process (AHP) and bootstrap resampling to assess data reliability and quantify uncertainty in thermal maturity assessments. This approach is demonstrated with three high-maturity shale samples (Barnett, Haynesville, and Eagle Ford), analyzed by two petrographers with contrasting experience levels.</div><div>The AHP model incorporates three evaluation indices-interval coverage probability, confidence interval width, and mean absolute percentage error-to generate composite reliability scores for each dataset. Results show that AHP assigns higher credibility to measurements from the more experienced analyst, effectively distinguishing data quality within the same environment, highlighting the model's ability to capture systematic biases. Bootstrap resampling generates robust confidence intervals for mean reflectance values, establishing probabilistic maturity ranges that better capture uncertainty than conventional single-point estimates. Our findings show that maceral identification and particle selection at high maturity levels introduce variations in reflectance measurements, ranging from 0.01% to 0.29% R_o (%R_o = mean random vitrinite reflectance). These variations arise from sample heterogeneity and subjective selection, rather than analytical error alone.</div><div>The integrated framework shifts from deterministic maturity reporting to probabilistic, credibility-weighted maturity assessment, providing a practical tool for uncertainty-aware maturity interpretation in high-maturity shale systems.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"316 ","pages":"Article 104952"},"PeriodicalIF":5.7,"publicationDate":"2026-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146095634","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}

{"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 ,&nbsp;Anne E. Oberlink ,&nbsp;John G. Groppo ,&nbsp;Prakash Joshi ,&nbsp;Dorin V. Preda ,&nbsp;David P. Gamliel ,&nbsp;Todd Beers ,&nbsp;Michael Schrock ,&nbsp;Shelley D. Hopps ,&nbsp;Tonya D. Morgan ,&nbsp;Bernd Zechmann ,&nbsp;James C. Hower","doi":"10.1016/j.coal.2026.104962","DOIUrl":"10.1016/j.coal.2026.104962","url":null,"abstract":"<div><div>As part of the scanning electron microscopy (SEM)/ transmission electron microscopy (TEM)/ energy dispersive x-ray spectroscopy (EDS) investigation of the pre- and post-pilot-scale HNO₃-based extraction of rare earth elements from a beneficiated eastern Kentucky coal-derived fly ash, 2- to 3-μm-thick rims were observed in cross sections of post-processing Al<img>Si fly ash spheres. Compared to the cores of the particles, the rims are depleted in all measured elements except Si. As an aside, Berti et al. (2025) noted an apparent depletion, if not absence of &lt;4-μm particles in the HNO₃-processed ash. In this addendum, particle-size analysis demonstrates that the processed ash is finer than the feed ash. Some of the fineness may be attributed to dissolution or partial dissolution of the finest grains. The latter trend might be offset, in part, by the attrition of fine flakes of material from the rims of coarser particles.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"316 ","pages":"Article 104962"},"PeriodicalIF":5.7,"publicationDate":"2026-02-28","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}

{"title":"Swin-UNETR: A transformer-based model for 3D pore network segmentation in low-permeability sedimentary rocks","authors":"Mengdi Sun ,&nbsp;Qamar Yasin ,&nbsp;Eshimiakhe Daniel ,&nbsp;Ghulam Mohyuddin Sohail ,&nbsp;Atif Ismail ,&nbsp;Bo Liu ,&nbsp;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":"2026-02-12","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}

{"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 ,&nbsp;Zhaoyu Yang ,&nbsp;Jianqiang Wang ,&nbsp;Zhilei Hao ,&nbsp;Gengshun Yao ,&nbsp;Hui Xue ,&nbsp;Dongdong Zhang ,&nbsp;Chao Liang ,&nbsp;Heng Peng ,&nbsp;Nan Du ,&nbsp;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 7₃ 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 (&gt;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":"2026-02-12","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}

{"title":"Intensified wildfire activity due to volcanism across the Triassic-Jurassic boundary in northwestern China","authors":"Wenxin Hu ,&nbsp;Qingyong Luo ,&nbsp;Jianfa Chen ,&nbsp;Linhao Fang ,&nbsp;Man Lu ,&nbsp;Medet Junussov ,&nbsp;Tao Du ,&nbsp;Xintong Liu ,&nbsp;Xiaohang Pan ,&nbsp;Gui Wang ,&nbsp;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 (&gt; 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":"2026-02-12","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}

{"title":"Responses of coal macromolecules and micropores to CO2 injection and their implications for ECBM: A review","authors":"Jianxin Li ,&nbsp;Jienan Pan ,&nbsp;Songhang Zhang ,&nbsp;Mengyuan Zhang ,&nbsp;Kai Wang ,&nbsp;Quanlin Hou","doi":"10.1016/j.coal.2026.104949","DOIUrl":"10.1016/j.coal.2026.104949","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Permanently storing CO&lt;sub&gt;2&lt;/sub&gt; in geological formations is a critical strategy for reducing carbon emissions. Coal reservoirs are a particularly promising option, as injecting CO&lt;sub&gt;2&lt;/sub&gt; into coal seams enables enhanced coalbed methane (ECBM) recovery by displacing CH&lt;sub&gt;4&lt;/sub&gt;, offering combined economic and environmental benefits. Micropores serve as the primary spaces for CO&lt;sub&gt;2&lt;/sub&gt; storage and CH&lt;sub&gt;4&lt;/sub&gt; displacement, with various functional groups on their surfaces providing the driving force for gas adsorption. Coal exhibits a higher adsorption affinity for CO&lt;sub&gt;2&lt;/sub&gt; than for CH&lt;sub&gt;4&lt;/sub&gt;. The injected CO&lt;sub&gt;2&lt;/sub&gt; effectively displaces pre-adsorbed CH&lt;sub&gt;4&lt;/sub&gt; molecules through competitive adsorption. As CH&lt;sub&gt;4&lt;/sub&gt; desorbs, the stronger interaction between coal macromolecules and CO&lt;sub&gt;2&lt;/sub&gt; 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&lt;sub&gt;2&lt;/sub&gt; storage capacity and CH&lt;sub&gt;4&lt;/sub&gt; displacement efficiency. Therefore, a fundamental investigation into the response characteristics and interaction mechanisms of coal macromolecules and micropores during CO&lt;sub&gt;2&lt;/sub&gt;-ECBM processes is crucial for understanding the phenomena of matrix deformation and the underlying adsorption-storage behavior.&lt;/div&gt;&lt;div&gt;Firstly, this paper presents an investigation to understand how various functional groups contribute to CO&lt;sub&gt;2&lt;/sub&gt; adsorption. CO&lt;sub&gt;2&lt;/sub&gt; adsorption can induce the rearrangement of microcrystalline structure, accompanied by alterations in its microporous structure. The response characteristics of micropores and microcrystalline structures, their interaction mechanisms with CO&lt;sub&gt;2&lt;/sub&gt;, and the factors controlling these interactions will be systematically analyzed in subsequent sections. Finally, an in-depth discussion of current challenges and future research directions is presented, offering valuable insights for further in-depth research.&lt;/div&gt;&lt;div&gt;Owing to their higher molecular stability and superior adsorption capacity, anthracites are recommended as more promising targets for CO&lt;sub&gt;2&lt;/sub&gt;-ECBM projects compared to low- and medium-rank coals. Anthracite, the rarest form of coal, is mined in only a few countries, including China, the United States, Russia, Ukraine, Vietnam, North Korea, South Africa, Australia, and Canada. These countries possess potential advantages in applying the CO&lt;sub&gt;2&lt;/sub&gt;-ECBM technology to their high-rank coal resources. Matrix deformation is intrinsically linked to alterations in molecular structure. Looking forward, a promising future direction lies in actively regulating this microscopic deformation by using surfactants to modify the molecular structure, thereby controlling the assoc","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"315 ","pages":"Article 104949"},"PeriodicalIF":5.7,"publicationDate":"2026-02-12","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}