International Journal of Coal Geology最新文献

{"title":"Element geochemical characteristics for the roof and floor rocks of coal seams in the Shendong mining area: Emphasis on hazardous element fluorine","authors":"Zheng Zhang ,&nbsp;Guoqing Li ,&nbsp;Lei Wang","doi":"10.1016/j.coal.2025.104709","DOIUrl":"10.1016/j.coal.2025.104709","url":null,"abstract":"<div><div>The Shendong mining area produces over 200 million tonnes of coal annually, resulting in notable gangue output, including materials from coal roof, floor and gangue itself. The hazardous elements, particularly fluorine (F), present in the gangues pose challenges for energy utilization and safe use of mine water. Despite this, studies on the elemental geochemical characteristics of gangues in the Shendong mining area are limited. This study collected 19 samples of coal roof and floor and employed methods such as SEM-EDS, XRD, XRF and ICP-MS to analyse the mineral compositions and quantify major-element oxides, rare earth elements and yttrium (REY), and most trace elements. Additionally, fluorine concentration was determined using the alkali fusion–ion selective electrode method. Results indicate that fluorine has the highest average concentration (655 μg/g) among the trace elements, with an enrichment coefficient of 1.21. The major minerals identified in the samples include clay minerals, quartz, and feldspar. The REY distribution patterns in the investigated samples predominantly show L-type enrichment. Combined analysis of B/Ga, Sr/Ba, V/Cr, U/Th, Ni/Co and <em>δ</em>U suggest that the coal roof and floor formations occurred in a continental freshwater and oxic sedimentary environment. The material source analysis indicates that coal roof and floor rocks are primarily derived from felsic rocks in the upper continental crust, especially a mixed provenance of granite and calcareous mudstone. Principal component analysis (PCA) reveals that the fluorine primarily exists on the surface of illites in an adsorption state, with Cu, Cs, Se, Th and Rb exhibiting similar states of occurrence. Correlation analyses between fluorine concentrations in the coal roof and floor rocks and parameters of ∑LREY, La_N/Lu_N, and <em>δ</em>Ce suggest that fluorine tends to be enriched in weathering residues; additionally, a weakly oxidising environment appears to facilitate fluorine enrichment in these coal roof and floor rocks. The findings in this study can guide the development of effective strategies to reduce fluorine contamination in the mine water; additionally, they aid in developing approaches to address fluorine-related issues during combustion, thereby promoting the safe and efficient utilization of coal gangue as a supplemental fuel resource.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"300 ","pages":"Article 104709"},"PeriodicalIF":5.6,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083307","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 matter accumulation, paleoenvironment and kerogen structure of the Middle Jurassic Dameigou Formation, Qaidam Basin: Evidence from organic petrography and geochemistry","authors":"Zhongrui Wu ,&nbsp;Ralf Littke ,&nbsp;Tianxu Guo ,&nbsp;Sheng He ,&nbsp;Sebastian Grohmann","doi":"10.1016/j.coal.2025.104707","DOIUrl":"10.1016/j.coal.2025.104707","url":null,"abstract":"<div><div>The organic matter in terrestrial sediments provides not only a record of geological events but is also as a vital source of fossil fuels. Its enrichment is fundamentally governed by the interplay of complex depositional environments and diverse climatic conditions. This study presents an integrated investigation utilizing major element oxides, trace elements, rare-earth elements, organic petrography, pyrolytic analysis, and infrared spectroscopy to systematically evaluate the provenance, tectonic setting, paleoclimate, weathering conditions, and organic matter accumulation of the Middle Jurassic Dameigou Formation, as well as to elucidate the chemical composition of kerogen. Geochemical parameters, particularly the Th/Sc vs. Zr/Sc ratios, indicate the absence of recycled sediments throughout the studied succession. Geochemical discrimination diagrams, particularly the Th/Sc vs. Zr/Sc and La/Th vs. Hf plots, provide compelling evidence for felsic volcanic rocks serving as the predominant source material.The interpretation of the tectonic setting as an active continental margin is constrained by multiple discrimination diagrams, such as the La–Th–Sc and Th–Co–Zr/10 ternary systems. The depositional sequence exhibits distinct vertical variations in organic matter composition and paleoenvironmental conditions. Unit 1 is characterized by terrestrially derived macerals (vitrinite and inertinite), while units 2 and 3 show a progressive transition to liptinite-dominated assemblages, primarily composed of lamalginite. Multiple chemical weathering proxies, specifically the Chemical Index of Alteration, Weathering Index, and Sr/Cu ratios, demonstrate that paleoclimatic conditions evolved from warm/humid environments characterized by intense chemical weathering towards cooler conditions with diminished continental weathering intensity. Molecular-level characterization using μ-FTIR and CP-Py-GC/MS reveals distinctive organic matter compositions: unit 1 is dominated by aromatic structures (73.0–83.5 %), while unit 2 shows predominant aliphatic compounds (41.6–72.9 %). The decrease in aliphatic compounds to 39.2 % in unit 3 correlates with increased water salinity, suggesting environmental control on kerogen composition. The δ¹³C values exhibit stratigraphic variations, with comparatively higher values in Unit 1 (−33.01 ‰ to −25.70 ‰) compared to lower values in Units 2 and 3 (−41.56 ‰ to −28.79 ‰), reflecting the higher abundance of terrestrial maceral components in Unit 1 and proximal Unit 2 deposits. These findings provide crucial insights into the depositional evolution and organic matter accumulation mechanisms in the study area.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"300 ","pages":"Article 104707"},"PeriodicalIF":5.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083369","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 modes of occurrence and evolution mechanism of germanium and lithium in coal: Insights from density functional theory","authors":"Ruifeng Mu ,&nbsp;Shaoqing Wang ,&nbsp;Xiaoling Wang ,&nbsp;Haofan Su ,&nbsp;Yan Shao","doi":"10.1016/j.coal.2024.104661","DOIUrl":"10.1016/j.coal.2024.104661","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Critical elements in coal, such as Ge and Li, recently have attracted attention due to their economic significance. Modes of occurrence of these critical elements are academically and practically important, because they can not only provide evidence for sources of elements and minerals in coal and regional geological background information, but also help with design of recovery methods. However, conventional analytical methods are unable to observe precisely the organic binding sites of Ge and Li in coal, and this limits the understanding of their enrichment mechanism and the improvements for recovery techniques. In this study, organic modes of occurrence and evolution mechanism of Ge&lt;sup&gt;4+&lt;/sup&gt; and Li&lt;sup&gt;+&lt;/sup&gt; were investigated at the atom level by constructing molecular models of Ge- and Li-rich coals combined with density functional theory (DFT) methods. The solid-state &lt;sup&gt;13&lt;/sup&gt;C nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and helium pycnometry analyses indicate that the molecular formulas of Ge- and Li-rich coals are C&lt;sub&gt;166&lt;/sub&gt;H&lt;sub&gt;162&lt;/sub&gt;N&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;32&lt;/sub&gt; and C&lt;sub&gt;153&lt;/sub&gt;H&lt;sub&gt;174&lt;/sub&gt;N&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;24&lt;/sub&gt;S, respectively. The DFT analysis reveals that the binding sites for Ge&lt;sup&gt;4+&lt;/sup&gt; in Ge-rich coal are located near the carboxyl group (-COOH) and the pyrrole ring, while those for Li&lt;sup&gt;+&lt;/sup&gt; in Li-rich coal are near the carbonyl group (-C=O) and the pyrrole ring. The Ge&lt;sup&gt;4+&lt;/sup&gt; is immobilized in the Ge-rich coal molecular model through coordination bonds with the O atom in the -COOH and the C atom in the pyrrole ring, while being away from the N atom in the pyrrole ring. Li&lt;sup&gt;+&lt;/sup&gt; forms a coordination bond with the O atom in the -C=O and additional coordination bond with the nearby hydroxyl group during binding to the pyrrole ring. The impact of coal rank on the organic modes of occurrence of Ge&lt;sup&gt;4+&lt;/sup&gt; and Li&lt;sup&gt;+&lt;/sup&gt; was investigated using Wender coals of different ranks, which were one of the earliest proposed coal models. At the lignite stage, oxygen-containing functional groups and aromatic rings show a strong binding ability to Ge&lt;sup&gt;4+&lt;/sup&gt; and Li&lt;sup&gt;+&lt;/sup&gt;, facilitating their enrichment in coals. Along with coal rank advance to bituminous coal, the reduction of oxygen-containing functional groups (e.g., -COOH and -C=O) and the relatively low condensation of aromatic rings decrease binding sites for Ge&lt;sup&gt;4+&lt;/sup&gt; and Li&lt;sup&gt;+&lt;/sup&gt;, and the binding ability also decline, resulting in a decrease in their concentration. In anthracite stage, highly condensed aromatic rings provide binding sites for Ge&lt;sup&gt;4+&lt;/sup&gt; and Li&lt;sup&gt;+&lt;/sup&gt;. The strong binding ability of aromatic rings to Ge&lt;sup&gt;4+&lt;/sup&gt; indicates that it is probably enriched in anthracite, whereas Li&lt;sup&gt;+&lt;/sup&gt; is difficult to enrich owing to its relatively weak binding ability to aromatic rings. The low conte","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"298 ","pages":"Article 104661"},"PeriodicalIF":5.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143127865","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":"","authors":"James C. Hower","doi":"10.1016/j.coal.2024.104672","DOIUrl":"10.1016/j.coal.2024.104672","url":null,"abstract":"","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"298 ","pages":"Article 104672"},"PeriodicalIF":5.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142901784","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":"Coalbed gas: A review of research directions from the past to the future as facilitated by bibliometrics","authors":"Romeo M. Flores ,&nbsp;Tim Moore","doi":"10.1016/j.coal.2024.104683","DOIUrl":"10.1016/j.coal.2024.104683","url":null,"abstract":"<div><div>This bibliometric review used coalbed gas articles published in the International Journal of Coal Geology (IJCG) from 1986 to 2022 catalogued in the Scopus database to compare similar articles indexed in the Web of Science (WoS) database from 1999 to 2016. Comparison focused between highly cited articles (top 1 % versus &gt;100 citations in the WoS and Scopus databases, respectively) from the 2007–2016 period. Analysis of articles in the WoS database reveals research fronts center on modeling fractal pores related to gas adsorption and gas exploration in China's basins (Luo et al., 2017). In contrast, this study of research fronts of articles in the Scopus-IJCG database range from laboratory methods and models of coal reservoir properties; enhanced coalbed methane recovery and carbon dioxide storage; to experiments on microbes, methanogenesis, isotope geochemistry, and biochemical nutrients for biogenic gas generation. Thus, a key difference in coalbed-gas research fronts between the databases is disciplinary breadth for Scopus and discipline specific for WoS.</div><div>Caveats in interpreting analysis of citation numbers about research fronts include high rate of self-citation (“clubbing/inwardness”); researchers maintaining “continuous stream of publications for long periods”; growth of highly cited research of narrow fields with large datasets used to publish for prolonged periods; mass publications (“salami slicing”) to increase citation counts; researchers publishing in high-profile journals indexed by WoS for professional advancement; and experimental methods and review papers more cited than original papers. Also, the fall of gas prices from 2008 to 2014 facilitated rapid decrease in coalbed gas production and caused significant drop in the number of articles published in the IJCG from the United States and Europe. Conversely, the number of coalbed-gas articles from 2008 to 2022 increased 7–52 % for China and 25–33 % for Australia. Finally, analysis of IJCG articles reveals international research collaboration (IRC) grew up to 70 % by 2011 and became more diversified in research topics by 2022. Thus, IRC is the future pathway that brings together researchers to advance new knowledge of coalbed gas such as deep coalbed gas reservoirs to support Just Energy Transition as countries changeover to energy mix that moves away from coal to attain net-zero carbon emissions by 2050.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"298 ","pages":"Article 104683"},"PeriodicalIF":5.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142975197","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":"Geochemistry of tonsteins and its implications for Li-Zr (Hf)-Nb (Ta) enrichments in Cisuralian coal seams, Shanxi Province, North China","authors":"Zhanming Guo ,&nbsp;Beilei Sun ,&nbsp;Chao Liu ,&nbsp;Mingyuan Lei ,&nbsp;Xu Wang ,&nbsp;Yao Wang","doi":"10.1016/j.coal.2025.104697","DOIUrl":"10.1016/j.coal.2025.104697","url":null,"abstract":"<div><div>Altered volcanic ashes within coal and coal-bearing sequences, often occurring as persistent bands embedded within coal seams (generally as tonsteins), can characterize the geochemical features and hence quality of coal. This study investigates the mineralogical and geochemical features of tonsteins within the coal seams from Shanxi Formation, North China in order to define the critical elements enrichments in coal benches. Mineralogical analysis indicates that the tonsteins are predominantly composed of kaolinite and quartz, while illite was identified in one tonstein sample and some parting/floor samples. The geochemical data indicate enrichments in SiO₂, Al₂O₃, and CaO, while tonsteins display higher SiO₂/Al₂O₃ ratios than partings/floor and coals. Compared with world hard coals, the coal benches are enriched in Zr, Hf, Pb, and Th. These critical metals enrichments in coal benches are attributed to the volcanic ash input during peat accumulation. Hierarchical clustering of trace, major, and REY elements shows distinct grouping patterns between coal and non-coal samples. Group A3 clusters trace elements Li, Zr, Hf, Nb, and Ta together with major element oxides Al₂O₃ and SiO₂, and is primarily related to ash yield. The TiO₂/Al₂O₃ ratios, discrimination diagrams of Zr/TiO₂ vs. Nb/Y and Al₂O₃/TiO₂ vs. Nb/Yb ratios as well as REY distribution patterns, indicated that the tonsteins, transformed from air-fall volcanic ash, were likely derived from volcanic eruptions in Inner Mongolia Paleo-Uplift (IMPU), with volcanic ash of intermediate rock composition. The enrichment of critical metals, particularly Li-Zr (Hf)-Nb (Ta) assemblage, is primarily influenced by the input of multiple layers of intermediate volcanic ash during peat accumulation in the Cisuralian coal, North China.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"300 ","pages":"Article 104697"},"PeriodicalIF":5.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083371","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":"","authors":"James C. Hower","doi":"10.1016/j.coal.2025.104698","DOIUrl":"10.1016/j.coal.2025.104698","url":null,"abstract":"","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"300 ","pages":"Article 104698"},"PeriodicalIF":5.6,"publicationDate":"2025-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083308","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":"Climatic reconstruction of the Late Palaeocene using sedimentary archives from the Bikaner-Nagaur Basin, Rajasthan, India","authors":"Dinesh Kumar ,&nbsp;Tushar Adsul ,&nbsp;Ofentse M. Moroeng ,&nbsp;Zoremsiami Pachuau ,&nbsp;Ashutosh Panigrahi ,&nbsp;Santanu Ghosh ,&nbsp;Asmita Datta ,&nbsp;Rupayan Sen ,&nbsp;Atul Kumar Varma","doi":"10.1016/j.coal.2025.104695","DOIUrl":"10.1016/j.coal.2025.104695","url":null,"abstract":"<div><div>The present study examines Late Palaeocene climatic changes recorded in the shale-lignite‑carbonaceous shale sequence of the Bikaner-Nagaur Basin, Rajasthan, India. Various analytical methods such as organic petrography, stable isotopes of organic carbon (δ¹³C_org), organic carbon to total nitrogen ratio (C_org/TN), Rock-Eval parameters, and Fourier transform infrared spectroscopy are employed to investigate the palaeoclimatic shifts. From the bottom shale to the overlying lignite sequence, δ¹³C_org shows minimal fluctuations, indicating a consistent supply of organic matter from both angiosperms and gymnosperms. However, a significant negative carbon isotopic excursion (nCIE; δ¹³C_org ranging from −26.8 to −29.9 ‰) is observed from the lignite to the overlying carbonaceous shales. This suggests a sudden increase in isotopically lighter CO₂ or its higher partial pressure in the atmosphere during the Late Palaeocene. This nCIE is accompanied by a sharp decrease in the C_org/TN values and a notable increase in ash yield for the carbonaceous shales, suggesting peatland flooding by sediment-laden surface runoffs triggered by intense precipitation. The increased rainfall also raised groundwater levels, stabilizing hydrological balance within the mire. This facilitated the selective preservation of hydrogen-rich alginite under anoxic conditions, as indicated by geochemical proxy (relative hydrocarbon potential = 4.52, on average), contributing to elevated hydrogen index values (443 mg HC/g TOC on average) in the carbonaceous shale samples. The increased groundwater level is linked with the observed nCIEs in the carbonaceous shale samples, suggesting an abrupt climatic transition characterized by ¹³C-depleted atmospheric CO₂ and intensified rainfall under warm-humid conditions during the deposition of these carbonaceous shales. These findings point towards potential influences of a Late Palaeocene global-scale hyperthermal event.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"299 ","pages":"Article 104695"},"PeriodicalIF":5.6,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143050020","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":"Climatically-driven cessation of coal formation in tropical Pangea around the Pennsylvanian-Permian boundary; an example from alluvial-lacustrine succession of the Líně Formation (Czechia)","authors":"Roland Nádaskay ,&nbsp;Stanislav Opluštil ,&nbsp;Karel Martínek ,&nbsp;Zbyněk Šimůnek ,&nbsp;Jaroslav Zajíc ,&nbsp;Jana Drábková ,&nbsp;Petra Podzimková ,&nbsp;Ivana Sýkorová","doi":"10.1016/j.coal.2025.104694","DOIUrl":"10.1016/j.coal.2025.104694","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Increasing climatic seasonality within tropical Pangea during the Pennsylvanian–Permian transition had a significant impact on landscape habitat and terrestrial biota evolution. One of the important consequences was cessation of peat formation in tropical Pangea – an underexplored issue because successions of this age in major European coalfields are either not preserved or are stratigraphically poorly constrained. The about 1 km thick Líně Formation (upper Gzhelian–lower Asselian) of Bohemian basins dominated by fluvial and alluvial red-beds interbedded by grayish lacustrine deposits records ∼3.5 Myr long tectono-sedimentary, climatic and biotic history already calibrated by TIMS ages to the Pennsylvanian–Permian transition. By integrating outcrop- and basins-scale data on sedimentary facies as well as on terrestrial biota, this paper evaluates the effects of climate and of post-orogenic tectonic processes on resulting depositional and biotic records and their effect on peat accretion. The current data indicate that the climate oscillated in about 450 kyr scale between less and more seasonal. During the Late Pennsylvanian, minimum seasonality (max. humidity) supported presence of ‘wet fluvial systems’ and meromictic lake formation lined with rheotrophic peat swamps, whereas during the driest climate (max. seasonality), well-drained fluvial landscape dominated the basin lowland. During the Early Permian, well-drained fluvial/small shallow lake habitats (‘dry fluvial systems’) prevailed due to long-term aridification trend in tropical Pangea, and wetland – dryland biomes coexisted over most of the time in a preservation window of the basin lowland and/or adjacent upland habitats. Their proportion, however, varied significantly in accord with climatic oscillations. The Líně Fm. was deposited in a half-graben basin system formed in response to post-Variscan intra-plate extension. The basin filling reflected three ‘rift phases’: (1) initiation, with localized subsidence and opening of initial sub-basins; (2) climax, with more distributed, maximum subsidence and interconnecting of sub-basins to form extensive basin system; (3) waning, likely dominated by thermal subsidence.&lt;/div&gt;&lt;div&gt;Formation of major, basinwide Klobuky Lake was facilitated by wet period ocurring during the rift climax stage with the most rapid creation of the accommodation space. Peat swamps formed and the peat accreted only during the late Gzhelian up to TIMS calibrated C&lt;img&gt;P boundary. Increasing aridification, however, constrained peat swamps from floodplain to shallowed lakes, the water table of which suffered less from seasonal oscillations comparing to floodplain areas. Purely rheotrophic, usually high-ash peat swamps formed. The peat-swamp development was often interrupted by temporary rise of lake level and influx of clastic material. Resulting coal beds are usually few tens of centimeters thick, and if thicker, they commonly contain clastic partings or high-ash c","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"300 ","pages":"Article 104694"},"PeriodicalIF":5.6,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083372","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":"Dynamic evolution and differential enrichment of deep coalbed methane: A case study in Qinshui Basin","authors":"Xiongxiong Yang ,&nbsp;Shuheng Tang ,&nbsp;Zhaodong Xi ,&nbsp;Songhang Zhang ,&nbsp;Qian Zhang ,&nbsp;Ke Zhang ,&nbsp;Donglin Lin ,&nbsp;Jing Wang","doi":"10.1016/j.coal.2025.104696","DOIUrl":"10.1016/j.coal.2025.104696","url":null,"abstract":"<div><div>Gas content is a critical factor in evaluating the resource potential and predicting the productivity of deep coalbed methane reservoirs. This study investigates the evolution of gas content in deep coal reservoirs over geological time and explores models of differential gas enrichment. Using Carboniferous-Permian deep coal reservoirs in the Yushe-Wuxiang block of the Qinshui Basin as a case study, fluid inclusion analysis, basin modeling, and theoretical gas content calculations were combined to quantitatively reconstruct the pressure and gas content evolution during the uplift of these coal reservoirs. Fluid inclusion analysis revealed homogenization of temperatures ranging from 85 °C to 155 °C in the coal-bearing strata, indicating trapping pressures between 33.16 MPa and 46.42 MPa. These inclusions were trapped between 228.05 and 216.09 million years ago, coinciding with the period of maximum burial depth, and exhibit a pressure coefficient of 1.05–1.19, confirming an overpressure state. During the uplift phase, decreasing temperature and pressure led to the conversion of free gas into adsorbed gas. This transition resulted in a gradual increase in adsorbed gas content while free gas content declined. Intense tectonic activity during the Himalayan orogeny induced fracturing and depressurization of the coal reservoirs, causing substantial dissipation of free gas. Consequently, the deep coal reservoirs in the Yushe-Wuxiang block currently exist at normal pressure and are devoid of free gas. Comparative analysis of gas content and reservoir pressure evolution across different blocks led to the proposition of four distinct coalbed methane enrichment models: (1) deep burial and weak tectonic reworking, (2) deep burial and intense tectonic reworking, (3) shallow burial and weak tectonic reworking, and (4) shallow burial and intense tectonic reworking. The deep burial and weak tectonic reworking model are identified as a promising target for coalbed methane exploration and development in North China. This study elucidates the mechanisms responsible for differential gas content enrichment in deep coal reservoirs, providing valuable insights for guiding the exploration and development of deep coalbed methane resources.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"299 ","pages":"Article 104696"},"PeriodicalIF":5.6,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143049662","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}