International Journal of Coal Geology最新文献

{"title":"Review of brittle failure mechanisms and reinforcement strategies for shale roof in U.S. underground coal mines","authors":"Gaobo Zhao ,&nbsp;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":"2026-02-12","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}

{"title":"Molecular characterization of Carboniferous plant biomarkers from two low-maturity European coal basins","authors":"Ádam Nádudvari ,&nbsp;Justyna Smolarek-Lach ,&nbsp;Ewa Szram ,&nbsp;Monika J. Fabiańska ,&nbsp;Bernd R.T. Simoneit ,&nbsp;Magdalena Misz-Kennan ,&nbsp;Dmitry Zastrozhnov ,&nbsp;Leszek Marynowski","doi":"10.1016/j.coal.2026.104944","DOIUrl":"10.1016/j.coal.2026.104944","url":null,"abstract":"<div><div>The study investigated Mississippian low-rank coals from the Moscow Coal Basin (MCB) in Russia and the lowermost Pennsylvanian coals from the Upper Silesian Coal Basin (USCB) in Poland. The high sulfur content of the MCB coals is consistent with peat accumulation under neutral to alkaline conditions in a sulfur-rich environment. The more intense microbial activity and clay mineral contribution is supported by porigelinite, abundant hopenes, benzohopanes, diasterenes, and monoaromatic steroids. The USCB coal is characterized by low sulfur content, which points to mires not affected by sea water, and the prevalence of more oxic to suboxic conditions during deposition. Nevertheless, microbial transformation of organic matter is also evident, as indicated by the occurrence of aromatized triterpenoids such as aromatized fernanes. Biomarkers in the MCB coals, e.g. phyllocladane-, kaurane-, and abietane-type, ferruginol, sugiol, are derived predominantly from flood-plain plants (<em>Eskdalia olivieri</em>, <em>Gryzlovia meyenii, Lepidodendron spetsbergense, Archaeocalamites</em>) and <em>Adiantites</em> sp., <em>Sphenopteris</em> sp., <em>Rhodeopteridium</em> sp., <em>Cardiopteridium dobrovii</em> or <em>Archaeopteridales</em>, whereas the USCB coals reflect contributions from pteridosperms (<em>Lyginopteridales, Medullosales, Callistophytales, Peltaspermales</em>) or cordaite remains, supporting a significant role for cordaitalean plants (e.g., Voltziales, Coniferales, Taxales, Cordaitales). Compounds such as ββ-hopanes, tocopherols, methyltrimethyltridecylchromans (MTTCs), and alkanoic acids-generally rare in Carboniferous coals-occur more frequently in the MCB samples, indicating lower thermal maturity relative to the USCB coals. Remarkably, the MCB samples also contain exceptionally well-preserved free saccharides, which may represent the oldest such compounds documented in a sedimentary organic matter environment.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"315 ","pages":"Article 104944"},"PeriodicalIF":5.7,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995725","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":"Organic petrology of coals from Botswana: Evidence of variations in depositional environments","authors":"Sanki Biswas,&nbsp;Nicola J. Wagner,&nbsp;Ndivhuho Nendouvhada,&nbsp;Ofentse M. Moroeng","doi":"10.1016/j.coal.2026.104937","DOIUrl":"10.1016/j.coal.2026.104937","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Permian coal samples from five major coalfields in Botswana—Lechana, South Orapa, Morupule, Takatokwane, and Tuli—were systematically characterized using coal petrography (maceral and mineral composition, microlithotype, and vitrinite reflectance) and geochemical analyses (inherent moisture, volatile matter, ash, and fixed carbon contents, total sulphur (TS), and gross calorific value (GCV)) to assess coal quality and enable the consideration of the depositional environments at the time of coal formation in these coalfields. Lechana and Morupule coals are inertinite-rich (avg. 54.5 and 84.4 vol.%, respectively; mmf basis), indicative of oxidizing conditions, whereas South Orapa, Takatokwane, and Tuli coals are vitrinite-dominated (avg. 78.1, 67.3, and 82.5 vol.%, respectively), reflecting deposition under oxygen-depleted (oxygen-lean), waterlogged peat-forming environments. Vitrinite reflectance indicates medium-rank D-C bituminous coals at Lechana, Morupule, and Tuli; low-rank sub-bituminous coals with localized medium-rank intervals at South Orapa; and a broader range of reflectance readings obtained for the Takatokwane samples, likely influenced by igneous intrusions and tectonic control. Elevated ash contents in all samples reflect detrital input of silicates and epigenetic mineralization of carbonates and sulphides, overall impacting the calorific value. The TS contents, up to 4.5 wt.% in some samples, will require selective mining and/or beneficiation prior to use in industrial applications. Selected samples, notably from Morupule Coalfield, might have potential to meet thermal power specifications, and certain studied coal samples (no. 12106, 12110, 12111, 1287, 1298, and 1471) from different coalfields shows potential for synthetic fuel production. Therefore, further detailed and systematic investigations are recommended.&lt;/div&gt;&lt;div&gt;Microlithotype and maceral analyses enable the elucidation of palaeomire depositional conditions. The peat-producing plants in the Lechana Coalfield accumulated in palaeomires evolving from lacustrine–deltaic to fluvial and back to lacustrine facies conditions. The occurrence of clay minerals, individual quartz grains, sporinite, and inertodetrinite highlights water table fluctuations, sediment influx, and periodic oxidation. The Morupule coal samples, dominated by durite and inertite, reveal more stable lacustrine deposition interrupted by episodic flooding, oxidation, and palaeowildfire events. The association of inertodetrinite, semifusinite, fusinite, and detrital clay infillings within cell lumens provides further evidence of episodic fluvial incursions into the mire. In contrast, the Takatokwane, South Orapa, and Tuli coals are vitrite and clarite rich, consistent with fluvial peat mire formation under waterlogged, oxygen-depleted (oxygen-lean) conditions. Variations in mineral and sulphur content further highlight localized geochemical controls. A regional gradient from fluvial to deltaic–lacus","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"314 ","pages":"Article 104937"},"PeriodicalIF":5.7,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145903478","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":"Paleoenvironmental reconstruction based on Early Cretaceous lignite deposits from Central Mongolia (Tevshiin Govi mine)","authors":"Fritz-Lukas Stoepke ,&nbsp;Ralf Littke ,&nbsp;Alexander Wheeler ,&nbsp;Hitoshi Hasegawa ,&nbsp;Niiden Ichinnorov ,&nbsp;Ulrich Heimhofer","doi":"10.1016/j.coal.2025.104924","DOIUrl":"10.1016/j.coal.2025.104924","url":null,"abstract":"<div><div>Lignites from the Mongolian Khukhteeg Formation bear exceptionally well-preserved plant macro- and mesofossils, providing important insights into the evolution and composition of peat forming flora in inner-continental paleo-Asia during the late Early Cretaceous. Numerous paleobotanical studies deal with fossil plant material from the Tevshiin Govi site, a small-scale open-cast lignite mine located in the Choir-Nyalga Basin of central Mongolia. However, information on the peat depositional environment of the Tevshiin Govi site is limited. In order to reconstruct the conditions during peat formation, coal petrology and palynology, complemented by geochemical measurements (TOC, TS, δ¹³C_org), was applied across a ∼ 35 m thick lignite-rich succession. Maceral composition is dominated by huminite with few samples being rich in inertinite and/or mineral matter. Calculated maceral indices indicate a topogenous mire setting. Variability of the GWI_AC indicates regular flooding of the peat. The stratigraphic trend in δ¹³C_org covaries with fusinite content, suggesting short-lived events such as peat fires affecting the δ¹³C_org signature. Palynological observations show a strong dominance of pollen produced by Cupressaceae and Pinaceae, which is in accordance with the meso- and macrofossil findings. No angiosperm pollen was observed. Based on diverse spore genera, a high diversity of herbaceous plants is suggested, which contrasts with previous reconstructions. Overall, the Tevshiin Govi site reveals a paleoenvironment that was mainly forested. Trees were dominated by conifers with an understory of pteridophytes (mainly ferns). The depositional setting was strongly influenced by fluvial processes. During phases of peat formation, the swamp was either covered by water or regularly flooded.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"314 ","pages":"Article 104924"},"PeriodicalIF":5.7,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145785693","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":"Aspects of Germanium and Nickel accumulation in low-ash coal: Examples from the Blue Gem coal, eastern Kentucky, USA","authors":"James C. Hower ,&nbsp;Susan M. Rimmer ,&nbsp;Darrell N. Taulbee ,&nbsp;Debora Berti ,&nbsp;Robert B. Finkelman ,&nbsp;David French ,&nbsp;Ian T. Graham ,&nbsp;Harold H. Schobert ,&nbsp;Lei Zhao ,&nbsp;Shifeng Dai","doi":"10.1016/j.coal.2025.104927","DOIUrl":"10.1016/j.coal.2025.104927","url":null,"abstract":"<div><div>The high volatile A bituminous Pennsylvanian (Duckmantian substage) Blue Gem coal, southeastern Kentucky, provides an opportunity to examine the concentration of minor elements in high-vitrinite, low-ash specific gravity fractions of the basal and middle lithotypes and the whole coal. For this study, the distributions of Ge and Ni are emphasized. While previous studies have suggested that Ge may be in an organic association, at least at ranks lower than the high volatile bituminous coal in this study, the studies generally relied upon indirect methods. Nickel, an element with known hyperaccumulation tendencies, is not correlated with the ash yield in the +90 %-vitrinite specific gravity fractions. Among the +90 %-vitrinite samples, Ni, Ge, and vitrinite decrease and Fe concentration increases with a decrease in density. While the absence of a correlation between element concentration and ash content might be an indirect indicator of an organic association, a previous transmission electron microscopy study demonstrated that Ni and Ge were present in a NiSn mineral, with the Ge possibly substituting for Sn. The association of Ge with minerals in high volatile bituminous coal does not necessarily imply that the peat through the low-rank precursors of that coal did not have organic associations. The functional groups responsible for binding inorganics in low-rank coals are lost in the metamorphic passage to bituminous coal and the previously organic elements may be incorporated into clays or other minerals, precipitated as oxides, or lost to the coal system. In the case of the Blue Gem coal, one factor in the coal metamorphism was the flow of hydrothermal brines coincident with the emplacement of the Pine Mountain thrust sheet. New elements introduced to the coal, at the time at a lower rank than the present high volatile A bituminous, could have interacted with elements in organic association, resulting in an episode of mineralization.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"314 ","pages":"Article 104927"},"PeriodicalIF":5.7,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145796308","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":"Evolution of maceral composition with thermal maturation of kerogen type II: Example from Silurian marine shales, Baltic Basin","authors":"Grzegorz P. Lis ,&nbsp;Tomasz Topór ,&nbsp;Maria Mastalerz","doi":"10.1016/j.coal.2025.104935","DOIUrl":"10.1016/j.coal.2025.104935","url":null,"abstract":"<div><div>Organic matter (OM) quantity, type, and thermal maturity are fundamental parameters in the evaluation of unconventional shale reservoirs. While numerous prior studies have addressed the chemical evolution of OM, detailed petrographic analyses tracing evolution of maceral composition across a full maturity range are less common, especially for pre-Devonian shale formations. This study examines maceral composition in 93 Lower Silurian shale samples from the Baltic Basin, Poland, spanning a maturity range from immature to overmature (0.50–4.19 % VRE). The results show a systematic evolution of maceral composition with increasing thermal maturity. Immature samples are dominated by macerals of the liptinite group, with bituminite being the most common maceral in the majority of the samples. The exception are organic-lean samples, where alginite and liptodetrinite dominate, possibly due to preferential degradation of bituminite. With increasing maturity, these primary macerals progressively convert to secondary solid bitumen, which becomes the dominant OM component above 0.8 % VRE. The study identifies distinct populations of solid bitumen, including diagenetic, initial-oil, primary-oil, and late-oil varieties, often coexisting, which complicates the use of solid bitumen reflectance as a robust maturity indicator. Graptolites, present in most samples, do not show significant morphological change across maturity but serve as a reliable maturity indicator. The maceral composition, characterized by an abundance of liptinite macerals at lower maturity, indicates that the formation had significant hydrocarbon potential, and that its OM quality is not responsible for the current low gas content. This research provides a quantitative model for OM transformation in a pre-Devonian source rock, bridging the gap between geochemical and petrographic studies and providing a crucial reference for interpreting ancient marine shales.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"314 ","pages":"Article 104935"},"PeriodicalIF":5.7,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145845305","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":"The Emeishan large igneous province (middle-late Permian) and implications for source rock development in South China (Sichuan Basin)","authors":"Ahmed Mansour ,&nbsp;Lamia A. Abdelhalim ,&nbsp;Wei Hengye ,&nbsp;Thomas Gentzis ,&nbsp;Sameh S. Tahoun ,&nbsp;Daniel Campos","doi":"10.1016/j.coal.2026.104936","DOIUrl":"10.1016/j.coal.2026.104936","url":null,"abstract":"<div><div>The middle-late Permian was an interval with global paleoenvironmental and paleoeceanographic instabilities, including the end-Guadalupian or the Guadlupian-Lopingian major extinction event. It was controlled by massive eruptions of the Emeishan Large Igneous Province (LIP) in South China, leading to the release of significant quantities of greenhouse gases and toxic elements into the ocean-atmosphere ecosystem. Here, the middle-upper Permian strata at the Xibeixiang section and well Daye 1 (DY1) from the western and northern depression of the Sichuan Basin were analyzed for palynological data, total organic carbon (TOC), Rock-Eval pyrolysis, and organic petrography. The identified palynomorphs are dominated by significantly high concentrations of acritarch, mainly of <em>Leiosphaeridia</em> and <em>Lophosphaeridium</em>, along with moderate to low abundances of prasinophytes, mainly <em>Dictyotidium</em> with some <em>Cymatiosphaera</em>. These palynomorphs reflect deposition of the Gufeng and Wujiaping formations in a shallow marine shelf environment characterized by low-energy and reducing conditions, consistent with occasional occurrences of foraminiferal test linings, pollen, and spores. Elevated levels of phytoclasts and sparse spores and pollen in the Gufeng Formation reinforce high terrestrial influx, compared to low phytoclasts and absence of terrestrial palynomorphs in the Wujiaping Formation, which indicated low-energy, distal depositional conditions associated with subsidence of the Guangwang-Kaijiang–Liangping Trough. Source rock evaluation revealed fair to excellent organic matter richness in the Gufeng Formation, compared to poor to very good richness in the Wujiaping Formation. However, both formations exhibited poor present-day hydrocarbon generation potential of Type III–IV kerogen, with most samples have reached the dry gas stage. The back-calculated (original) S₂o and HIo values revealed good to excellent generative potential and Type II to mixed Type II/III kerogen. In the study region, the eruption of the Emeishan LIP resulted in high rates of greenhouse outgasing and isotopically light carbon resulting in global perturbations in the carbon cycle, elevated organic carbon export, and the development of anoxic-euxinic conditions as evidenced from framboidal pyrite size and redox-sensitive elements. Additionally, it controlled a spike in heat flow patterns throughout the Sichuan Basin and thus expedited the thermal evolution of organic matter. As a consequence, the Permian source rocks in the Sichuan Basin entered the peak oil window in the Early Triassic, while they reached the dry gas window by the Jurassic.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"314 ","pages":"Article 104936"},"PeriodicalIF":5.7,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145893887","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":"Isotope and chemical alteration of coalbed gases during migration from underground coal mine into the atmosphere","authors":"Yaroslav Bezyk ,&nbsp;Dawid Szurgacz ,&nbsp;Maciej Górka ,&nbsp;Dariusz Strąpoć ,&nbsp;Łukasz Kruszewski ,&nbsp;Przemysław Wachniew ,&nbsp;Jarosław Nęcki ,&nbsp;Miroslaw Zimnoch ,&nbsp;Izabela Sówka ,&nbsp;Magdalena Modelska ,&nbsp;Wojciech Wołkowicz ,&nbsp;Carina van der Veen ,&nbsp;Thomas Röckmann","doi":"10.1016/j.coal.2025.104922","DOIUrl":"10.1016/j.coal.2025.104922","url":null,"abstract":"<div><div>Methane release into mine workings and the atmosphere poses a serious environmental and safety risks. This study examines the composition and stable isotope geochemistry of coalbed methane in a hard coal mine of the Upper Silesian Coal Basin (Poland), with emphasis on gas migration pathways from the coal seam through mine workings and ventilation shaft to the atmosphere. Methane concentrations decrease progressively with distance from the active excavation zone toward the exhaust shaft. In addition to CH₄ and CO₂, the coalbed gas contained notable amounts of nitrogen heterocyclic compounds, sulfur-bearing species, and chlorinated gases, depending on the sampling location and temporal window.</div><div>Geochemical results reveal a strong link between gas migration and isotopic variability in the underground environment. Zones of methane accumulation, commonly associated with bends in return airways, showed enrichment in ¹³C, consistent with diffusive fractionation. Variations in CH₄ and corresponding isotope effects during coal transport indicate multiple gas origins within the coal seam. Isotope signatures point to predominantly thermogenic CH₄ at the active mining level, whereas ¹³C-depleted methane at the exploited and flooded levels suggests secondary microbial generation. The microbial contribution is likely promoted by infiltrating meteoric waters supplying nutrients for methanogenic archaea, as supported by δ²H, δ¹⁸O signatures of mine water, and measurable tritium activity. The absence of enriched δ¹³C values in CO₂ and dissolved inorganic carbon (DIC) further implies mixed thermogenic-microbial gas origin in abandoned mine workings.</div><div>These findings highlight the combined influence of mining operations, diffusion-desorption processes, microbial activity, and gas mixing on the molecular and isotope composition of coalbed gases transported toward the exhaust shaft. Moreover, isotopic data from downwind emission plumes demonstrate the value of integrating underground measurements with atmospheric observations to trace and quantify methane emissions from coal mining operations.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"313 ","pages":"Article 104922"},"PeriodicalIF":5.7,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145689431","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":"Origin and diagenetic evolution of claystones in the CP2 coal seam, Adaohai Mine, Daqingshan Coalfield: Evidence from mineralogy and geochemistry","authors":"Ni He ,&nbsp;Shangying Li ,&nbsp;Hongfei Cheng ,&nbsp;Zhenxiao Wu ,&nbsp;Yichen Wang ,&nbsp;Shaoxian Liang","doi":"10.1016/j.coal.2025.104913","DOIUrl":"10.1016/j.coal.2025.104913","url":null,"abstract":"<div><div>The Daqingshan Coalfield in Inner Mongolia takes the CP₂ coal section (Shuanmazhuang Formation) as its primary mineable layer, with the CP₄ coal section (Zahuaigou Formation) as a local mineable layer. These coal sections contain abundant claystone resources. This study presents a systematic analysis of claystone samples from the CP₂ seam in the Adaohai Mine, integrating mineralogical and geochemical data to elucidate sediment provenance and diagenetic evolution. The dominant clay minerals include kaolinite, illite (with K⁺ primarily occupying the interlayer sites), and NH₄⁺-bearing illite (with NH₄⁺ primarily occupying the interlayer sites), with minor non-clay phases such as quartz, pyrite, diaspore, anatase, and calcite. The provenance of the claystones in the study area mainly derives from the intermediate-felsic volcanic ash associated with the Late Paleozoic continental arc volcanic activities in the Inner Mongolia Uplift, which is located on the northern margin of the North China Block. During the Late Paleozoic, the Paleo-Asian Ocean Plate subducted beneath the North China Block triggered extensive volcanic activity in the Inner Mongolia Uplift along the northern margin of the North China Block. The erupted volcanic ash was deposited in the coeval peat swamp basins of the North China region. Kaolinite primarily formed through the alteration of volcanic ash in basins, with minor kaolinite originating from the recrystallization of aluminosilicate colloidal solutions. Numerous fine-grained illite and NH₄⁺-bearing illite exhibit textural characteristics of replacing kaolinite grains, indicating that illite and NH₄⁺-bearing illite were formed by the transformation of the precursor mineral kaolinite under hydrothermal fluids associated with thermal anomaly activity in the Late Jurassic-Early Cretaceous of North China. These fluids, enriched in Ca, Mg, Al, Si, and N, can form fracture fillings predominantly composed of silexite, dickite, calcite, diaspore, and NH₄⁺-bearing illite with fractures. Beyond providing thermal impetus for mineral alteration, the hydrothermal fluids also have provided the necessary elements supply for the compositional changes of the claystone, promoting mineral transformation. This work highlights the complex interplay between volcaniclastic provenance and post-depositional hydrothermal processes in shaping clay mineral assemblages in coal-bearing sequences.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"313 ","pages":"Article 104913"},"PeriodicalIF":5.7,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145619780","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":"A deep learning system for sporomorph identification and Spore Coloration Index (SCI) calculation for evaluating source rocks' thermal maturity","authors":"Richard Bryan Magalhaes Santos ,&nbsp;Karen Soares Augusto ,&nbsp;Sidnei Paciornik ,&nbsp;Marcos Henrique de Pinho Maurício ,&nbsp;Tiago de Souza Mota ,&nbsp;Bruno Conceição do Nascimento ,&nbsp;Italo de Oliveira Matias ,&nbsp;Lauro Tiago Souza Santos ,&nbsp;Leandra Costa Lages ,&nbsp;Gil Marcio Avelino Silva ,&nbsp;André Luiz Durante Spigolon","doi":"10.1016/j.coal.2025.104921","DOIUrl":"10.1016/j.coal.2025.104921","url":null,"abstract":"<div><div>Determining the degree of maturation and thermal evolution in kerogen is vital to the hydrocarbons industry. This study evaluates the thermal maturation of source rock sections in sedimentary basins. Its determination makes it possible to estimate whether a sample from a given depth in an oil well falls within the window of oil or natural gas generation or remains immature. The Spore Coloration Index (SCI) can indicate the maturation of oil- and gas-prone material. The objective of this study is to automate this analysis, thereby achieving significant improvements in time efficiency and reliability. Traditionally, an operator visually identifies the presence of sporomorphs in slides using an optical microscope. When they encounter a sporomorph, the operator visually compares it with standard reference slides. The standard consists of 19 slides of spores of different degrees of maturity, ranging from the lightest to the darkest, from 1.0 to 10.0, in increments of 0.5. Comparison with the standard allows the operator to estimate the Spore Coloration Index (SCI) of a sporomorph. Various tests corroborated the literature's indication that the red channel best correlates with the thermal maturation index. A linear relationship was obtained between the average intensity of the red channel and the SCI (correlation coefficient R² = 0.97). Images of samples from various wells at different depths were acquired under conditions similar to those standardized for organopalynological slides. Deep Learning-based systems were trained to identify sporomorphs in the images. With the help of an expert operator, the objects were manually outlined in the images to create a reference database. This database was separated into a training set and a validation set, allowing the network to learn and then have its performance evaluated (accuracy ≈ 86 %). The captured images feed the system, which identifies the presence of sporomorphs, measures the SCI value of each one, and generates a histogram of SCI distribution for each case, allowing, for the first time, the direct calculation of the SCI without the need for visual analysis.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"313 ","pages":"Article 104921"},"PeriodicalIF":5.7,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145689426","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}