International Journal of Coal Geology最新文献

{"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}

{"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}