International Journal of Coal Geology最新文献

{"title":"Degradation of organic matter by radioactive radiation in black shales: An overlooked modification of organic molecular structures","authors":"Leibo Bian ,&nbsp;Zhe Zhao ,&nbsp;Xiaomei Wang ,&nbsp;Hamed Sanei ,&nbsp;Anthony Chappaz ,&nbsp;Jin Dong ,&nbsp;Zhongtian Dong ,&nbsp;Linfeng Xie ,&nbsp;Niels H. Schovsbo ,&nbsp;Fariborz Goodarzi ,&nbsp;Shuichang Zhang ,&nbsp;Wenzhi Zhao","doi":"10.1016/j.coal.2025.104864","DOIUrl":"10.1016/j.coal.2025.104864","url":null,"abstract":"<div><div>Natural radioactive radiation emitted by uranium (U) in sedimentary basins continuously transforms organic matter and thus its degrading impact overprints the burial-related thermal maturation process. However, the systematic pathway for irradiated alteration of sedimentary organic matter and its influence remain poorly understood. This omission hinders a comprehensive understanding of organic matter evolution after burial. Our study investigated the artificially and naturally irradiated alteration of organic matter in the U- and organic-rich Cambro-Ordovician Alum Shale of Northern Europe and Triassic Chang 7–3 shale in the Ordos Basin of China. After exposure of samples to a Co-60 source, radiation accelerated the conversion of bitumen to natural gas with a lower gas dryness (C₁/C_1–5 &lt; 0.8), while kerogen is converted to natural gas with a higher gas dryness (&gt;0.8). Moreover, enhanced radiation dose facilitates the transformation from resins and asphaltenes to aromatics and leads to enrichments of carbon-13 isotope, when the radiation dose reaches the thresholds of approximately 100 and 2000 kGy, respectively. Natural radiation exposure in the Chang 7–3 shales, identified by spatial distribution and affiliated phases of U, may have influenced bitumen structures through accelerating transformation of macro- to micro-organic compounds and generation of wet gas that could have enhanced hydrocarbon mobility. Moreover, an addition to the standard model for organic matter burial and transformation is proposed with integration of natural radiation exposure. Based on the calculated Proterozoic-Phanerozoic radiation dose in sedimentary rocks, we hypothesize that the radioactive processes might have consistently modified the characteristics of retained bitumen in uranium-enriched shales, thereby affecting carbon cycle on Earth's surface environments.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"309 ","pages":"Article 104864"},"PeriodicalIF":5.7,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144867138","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":"Understanding coalbed gas distribution from longwall mining: Geochemical and isotopic approach","authors":"Yaroslav Bezyk ,&nbsp;Dawid Szurgacz ,&nbsp;Dariusz Strąpoć ,&nbsp;Magdalena Misz-Kennan ,&nbsp;Monika J. Fabiańska ,&nbsp;Ewa Szram ,&nbsp;Łukasz Kruszewski ,&nbsp;Miroslaw Zimnoch ,&nbsp;Jarosław Nęcki ,&nbsp;Izabela Sówka ,&nbsp;Tomasz Kowalski ,&nbsp;Carina van der Veen ,&nbsp;Thomas Röckmann ,&nbsp;Maciej Górka","doi":"10.1016/j.coal.2025.104859","DOIUrl":"10.1016/j.coal.2025.104859","url":null,"abstract":"<div><div>Coalbed methane plays a critical role in both energy resource potential and environmental and mine safety strategies. Despite much research has been done on coalbed gas origin, the combined effects of coal maturity, gas migration processes, and mine ventilation in an active mining environment are still not fully understood. This study combined molecular and stable carbon and hydrogen isotope analyses of coalbed gases collected along the longwall coal face during the early and final stages of operation, with petrographic and geochemical characteristics of freshly mined coal from the Upper Silesian Coal Basin, Poland. Complementary organic petrography and biomarker analysis performed on freshly mined coal revealed that the vitrinite-rich bituminous coal is at peak oil-window maturity. Gas composition from a borehole in the coal seam indicated methane as the dominant component (up to 87 %), with contributions from carbon dioxide (up to 2.3 %) and lower amounts (0.1–1.5 %) of heavier hydrocarbons (C₂ − C₆). Heterocyclic species of sulfur (thiophene) and nitrogen (pyridine), chlorinated (1,2-DCE) compounds, oxygen-bearing organic gases (acetic acid), dimethyl sulfide (DMS), and some portion of ortho-cresol, tetrahydrofuran, formaldehyde, and cumene tracers were also found in the complex gas mixtures from the borehole.</div><div>Isotopic data of methane in the examined longwall coal face averaged at −48.1 ± 0.7 ‰ for δ¹³C and − 192.1 ± 7.1 ‰ for δ²H and coal maturity vitrinite reflectance at 0.75 ± 0.02 %. These molecular and isotopic coalbed gas data implied a thermogenic origin of the coalbed methane, with fingerprints of biodegradation in thermogenic system. Slightly depleted isotope values from the borehole under examination (δ¹³C: −50.9 ± 0.2 ‰ and δ²H: −194.2 ± 2.8 ‰) suggested the presence of free gas stored in the coal fractures. Spatial variations in gas composition and isotopic shifts across the longwall panel were found to be driven by ventilating airflow supplied to the working face. Isotope alteration along airflow path from main- to tailgate entries emphasized the influence of secondary processes, such as desorption and diffusion. Preferential loss of isotopically light ¹²CH₄ molecules, especially at gas accumulation zones (tailgate), aligns with findings from laboratory desorption experiment on successively crushed coal samples. In contrast, less systematic δ²H-CH₄ patterns under active mining reflected the combined effects of gas mixing, site-specific conditions, and parameters of coal mine operations.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"309 ","pages":"Article 104859"},"PeriodicalIF":5.7,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144780412","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":"CBM enrichment mechanisms in the Southern Qinshui Basin: A synergistic role of tectonic-lithological-hydrodynamic coupling","authors":"Xiaoxiao Sun ,&nbsp;Hui Wang ,&nbsp;Fengfeng Du ,&nbsp;Yanbin Yao ,&nbsp;Dameng Liu ,&nbsp;Zhong Liu","doi":"10.1016/j.coal.2025.104861","DOIUrl":"10.1016/j.coal.2025.104861","url":null,"abstract":"<div><div>The Qinshui Basin is renowned for its thick, laterally extensive coal seams, high thermal maturity, and significant coalbed methane (CBM) potential. However, reservoir heterogeneity resulting from multi-stage tectonic activity leads to pronounced variability in CBM enrichment, posing challenges for efficient development. This study examines the influence of individual and coupled tectonic, roof–floor lithological, and hydrodynamic factors on CBM accumulation in the southern Qinshui Basin, using seismic data, well logs, and gas content analysis. Four distinct CBM enrichment models are identified from north to south: in shallow seams, atmospheric precipitation-driven groundwater recharge, coupled with anticlinal structures, controls the spatial distribution of gas; with increasing burial depth, reduced groundwater mobility and improved roof–floor sealing shift the dominant control from hydrodynamic to lithological factors; in structural slope zones, gas enrichment is governed by the coupling of nose structure and hydrodynamic sealing; In fault-dominated areas, gas migration along faults and the sealing capacity of fault zones are the primary controls. These findings provide a scientific basis for optimizing CBM exploration and development in geologically complex basins.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"309 ","pages":"Article 104861"},"PeriodicalIF":5.7,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144766729","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":"Characteristics of different types of soluble organic matter in low- to middle-rank coals: Implications for tar generation and migration during tar-rich coal pyrolysis","authors":"Ruihui Zheng ,&nbsp;Yuan Bao ,&nbsp;Jiajun Li ,&nbsp;Jiao Xue ,&nbsp;Xuan Yuan ,&nbsp;Kuan Liu","doi":"10.1016/j.coal.2025.104863","DOIUrl":"10.1016/j.coal.2025.104863","url":null,"abstract":"<div><div>Soluble organic matter (SOM) in low- to middle-rank coal can be categorized into free (FSOM), mineral-associated (MSOM) and chemical-associated (CSOM) states. However, the characteristics of these different types of SOM remain poorly understood in tar-rich coal research, primarily due to the long-standing perception of coal as a conventional gas source rock. This paper investigates the geochemical characteristics of different types of SOM and the molecular structure characteristics of their residues after successive treatments, discusses the influence of organic matter maturity and tar yield on these characteristics, and clarifies the generation and migration mechanisms of pyrolysis tar. Nine low- to middle-rank coals with different maturity and tar yield collected from the Ordos Basin underwent successive treatments to obtained FSOM, MSOM and CSOM. Comparison of organic characteristics reveals: (1) SOM content follows the order of FSOM&gt; CSOM&gt; MSOM. The FSOM and MSOM are primarily composed of aromatics, while asphaltenes are the main components of the CSOM. (2) SOM polarity follows the order of CSOM&gt; MSOM&gt; FSOM, the polarity of FSOM and MSOM is influenced by both organic matter maturity and tar yield, while the polarity of CSOM is primarily affected by matter origin. (3) SOM maturity shows the order of CSOM&gt; MSOM&gt; FSOM, the geochemical characteristics of SOM are influenced by both organic matter maturity and tar yield. Comparison of molecular structure characteristics reveals: (1) Oxygen functional group content gradually increases across all SOM fractions, while aliphatic functional group content gradually decreases across all SOM fractions. (2) Molecular structure is influenced by both organic matter maturity and tar yield. Comprehensive comparison of the organic geochemistry and molecular structure characteristics reveals: (1) Group composition of CSOM is significantly affected by aromatic and hydroxyl functional groups. (2) FSOM and MSOM primarily contribute to the free hydrocarbons during tar-rich coal pyrolysis. (3) Migration pathway of pyrolysis tar follows the order of silicate minerals, carbonate minerals, pores and expulsion. These differences provide new insights into the understanding of pyrolysis tar generation and migration mechanisms.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"309 ","pages":"Article 104863"},"PeriodicalIF":5.7,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144867137","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":"Mineralogy and elemental geochemistry of Pennsylvanian high-sulfur coals in the Huanghebei Coalfield, Shandong, Northern China: Implications for the enrichment and controlling factors of U","authors":"Bofei Zhang ,&nbsp;Wenfeng Wang ,&nbsp;Qingfeng Lu ,&nbsp;Wenlong Wang ,&nbsp;Xiaozhen Teng ,&nbsp;Long Chen","doi":"10.1016/j.coal.2025.104867","DOIUrl":"10.1016/j.coal.2025.104867","url":null,"abstract":"<div><div>Uranium enrichment in coal is of great significance for understanding metallogenic processes and assessing resource potential. Numerous studies have investigated the geochemical behavior and modes of occurrence of U in super-high-organic‑sulfur coals from Southern China. However, the Huanghebei Coalfield in Shandong, a major high‑sulfur coal-bearing region in North China, yet remains largely unidentified. This study investigates the U enrichment and controlling factors of the Pennsylvanian No.11 coal from Huanghebei Coalfield, Shandong, Northern China. Uranium is enriched in the No. 11 coal (up to 89.3 μg/g), where U, Mo, and V are exclusively concentrated in the topmost coal bench underlying the limestone roof. The enrichment of critical elements, including U, Mo, and V, is attributed to infiltration of marine water from the overlying strata during the early diagenetic stage. Uranium in the coal shows both organic and inorganic associations. Notably, a small portion of U occurs in uraninite, which is more easily reduced and precipitated under anoxic conditions. The relationships of Al₂O₃ vs. TiO₂, Al₂O₃/TiO₂-Nb/Yb and the REY distribution patterns indicate that the sediment-source rocks of the No. 11 coal were the North Qinling Orogenic Belt. The predominant minerals identified in the No. 11 coal are NH₄-illite, calcite, quartz, pyrite, bassanite and kaolinite, with minor amounts of dolomite and siderite. The modes of occurrence of NH₄-illite, kaolinite, calcite, pyrite, and quartz, as well as fluorapatite, indicate that the No. 11 coal was likely influenced by multi-stage injection of hydrothermal fluids. Authigenic NH₄-illite is relatively high abundant, probably formed by the interaction of kaolinite with nitrogen released from organic matter during metamorphism induced by igneous intrusion. The δ¹³C_VPDB and δ¹⁸O_VPDB values of epigenetic carbonates in the coals indicate that the carbon and oxygen in the carbonates are primarily derived from hydrothermal fluid activities. The No. 11 coal has potential for resource development and utilization as raw material for U and deserves further attention.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"309 ","pages":"Article 104867"},"PeriodicalIF":5.7,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903083","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":"Sedimentology and geochemistry of the Upper Permian Longtan and Dalong formations in the Lianyuan Sag, Xiangzhong Depression, South China: Implications for paleoclimate, provenance, tectonic setting, and organic matter accumulation","authors":"Zhongrui Wu ,&nbsp;Ralf Littke ,&nbsp;Shuo Qin ,&nbsp;Yahao Huang ,&nbsp;Sheng He ,&nbsp;Yaohui Xu ,&nbsp;Yan Liu ,&nbsp;Xiao Chen ,&nbsp;Kaiming Wang","doi":"10.1016/j.coal.2025.104849","DOIUrl":"10.1016/j.coal.2025.104849","url":null,"abstract":"<div><div>The organic-rich shales in the Upper Permian Longtan Formation (LF) and Dalong Formation (DF) are important hydrocarbon source rocks and have become key targets for shale gas exploration in the Yangtze area, South China. To investigate the provenance, tectonic setting, paleoenvironmental conditions, and mechanisms of organic matter (OM) accumulation, this study presents an integrated petrological and geochemical study of a continuously cored well in the Xiangzhong Depression, South China. The LF was deposited in marine–continental transitional facies under a hot and humid climate with intense chemical weathering. OM is predominantly terrigenous-derived, consisting mainly of vitrinite and inertinite. Multiple geochemical proxies, together with pyrite framboid analyses, suggest that oxic, brackish water conditions, low paleoproductivity, and a high influx of terrestrial material prevailed during the deposition of the LF. In contrast, the DF comprises fully marine sediments, reflecting a depositional setting influenced by a rapid sea-level rise and progressive climatic aridification. These changes resulted in a saline, anoxic water column with enhanced primary productivity and reduced weathering intensity. The relationships between total organic carbon (TOC) content and geochemical indicators suggest that paleoclimate and terrigenous influx are the dominant factors controlling the OM accumulation in the LF, whereas upwelling-induced high productivity was the dominant factor driving OM enrichment in the DF. This study provides a comprehensive dataset on the LF and DF, which exhibit markedly different depositional environments, and aims to address the gap in the evaluation of Permian shale gas potential in the Middle Yangtze region.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"309 ","pages":"Article 104849"},"PeriodicalIF":5.7,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144749815","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":"Industrial and mining impacts on the organic matter of soils in a protected area of the Central Portuguese Coast: A petrographic and geochemical approach","authors":"Fernando Michels ,&nbsp;Joana Ribeiro ,&nbsp;Maria Helena Henriques ,&nbsp;Ádám Nádudvari ,&nbsp;Magdalena Misz-Kennan ,&nbsp;Monika J. Fabiańska","doi":"10.1016/j.coal.2025.104847","DOIUrl":"10.1016/j.coal.2025.104847","url":null,"abstract":"<div><div>Long-term industrial operations fueled by coal and oil have the potential to significantly impact surrounding ecosystems, particularly in the past when environmental regulations were less stringent. In this study, organic contamination was investigated in soils surrounding a former industrial complex and coal mining area on the Portuguese Atlantic coastline, active from the 19th century through the early 21st century. This area is currently included in the Natural Monument of Cabo Mondego, which highlights concerns regarding its environmental quality. Surface soil samples were investigated through a multi-technique approach using organic petrography, an uncommon yet powerful tool that provides unequivocal evidence of contaminants, and geochemical methods to identify sources of fossil fuel-derived contaminants. Results indicate that most of the samples exceed national reference levels for priority polycyclic aromatic hydrocarbons (PAH), with the highest concentrations found in the samples located up to 500 m from the former industrial facilities. These findings suggest that emissions from the industrial complex are the primary source of organic contamination in the area. Elevated levels of PAH (recognized environmental pollutants and human carcinogens) associated with contaminant combustion-derived organic particles (coke and char) raise environmental concerns. The presence of both local and imported coal particles in soil, along with the disposal of coal residues in the area, highlights contamination linked to historical coal handling and transport. The detection of charcoal particles in soil reflects the influence of regional wildfires that occurred in recent decades. These findings contribute to understanding the environmental vulnerabilities of the Cabo Mondego Natural Monument.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"309 ","pages":"Article 104847"},"PeriodicalIF":5.6,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144714490","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":"Implications of element enrichment in paralic coals from the Carboniferous in England","authors":"D.A. Spears","doi":"10.1016/j.coal.2025.104865","DOIUrl":"10.1016/j.coal.2025.104865","url":null,"abstract":"<div><div>The enrichment of trace elements in coals is of significant economic importance because of the growing demand for the critical elements. Several enrichment processes have been identified and in this paper the role of palaeosalinity is evaluated using published data from the East Pennine Coalfield (UK). The coal and associated mudrocks for which comprehensive ICP- AES and ICP-MS analyses are available is the Parkgate Coal. This is a high volatile bituminous coal of Upper Carboniferous (Pennsylvanian) age with a variable S content mainly due to pyritic S (Total S = 2.34 ± 1.83 %, Pyritic S = 1.17 ± 1.79 %).</div><div>Supporting information on the mineralogy of this and other major coals comes from XRD analyses. Although there is an extensive geochemical data base on coals and mudrocks from this Coalfield, most of the analyses were made using XRF with a restricted suite of trace elements (13). Comprehensive analyses of marine shales are not available for this coalfield and to evaluate the marine influence use is made of analyses of samples from the Netherlands. These samples are of comparable age and from the same extensive depositional area. Enrichment values calculated for the Parkgate Coal based on detrital trace elements in the mudrocks show that the chalcophile elements are enriched and pyrite is the major host for many of them. Other elements are enriched including Ge and Be and there is an organic association, possibly reflecting an original plant origin. The importance of a seawater control is demonstrated by close similarities in the enrichment values between the coals and marine shales. Use could be made of the enrichment values determined in this work to identify a seawater influence in coals elsewhere. Elements not enriched, and for which other controls operated, are Ga, Li, Zr and Nb. Although not confirmed for the UK coals the REE are probably in the same category. Alternatives to the control of seawater on the element enrichments in the studied coals are considered and rejected as having little or no effect.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"309 ","pages":"Article 104865"},"PeriodicalIF":5.7,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144895537","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":"Petrological and organic geochemical insights into the peat-forming environmental settings during the deposition of the early Oligocene Pirin coal deposit, SW Bulgaria","authors":"Alexander Zdravkov ,&nbsp;Achim Bechtel ,&nbsp;Ksenija Stojanović ,&nbsp;Doris Groβ ,&nbsp;Johannes Weitz ,&nbsp;Ivan Kojić ,&nbsp;Reinhard F. Sachsenhofer ,&nbsp;David Misch ,&nbsp;Dragana Životić","doi":"10.1016/j.coal.2025.104843","DOIUrl":"10.1016/j.coal.2025.104843","url":null,"abstract":"<div><div>The up to 30-m-thick Brezhani coal seam in the Pirin deposit (SW Bulgaria) is the only coal of early Oligocene age on the territory of Bulgaria, providing important insights into peat-forming environments during that period. The coal seam was investigated using organic petrography, bulk organic geochemistry and biomarker analysis.</div><div>Coal is predominantly composed of detrovitrinite with subordinate collotelinite and abundant corpogelinite. Liptinite macerals are mostly represented by alginite and suberinite, and locally resinite. The coal commonly contains semi-inertinized (oxidized) root tissues without apparent thermal influence. The low- to moderate tissue preservation indicates predominant contribution from plants with low preservation potential. Rare resin-impregnated woody tissues argue for peat accumulation within a sparsely forested shrub-dominated mire. Biomarker proxies indicate a contribution from mixed vegetational communities, composed of flowering plants and bald cypresses. A contribution of aquatic macrophytes is also evident.</div><div>Variable ash yields and sulfur contents indicate changeable water supply and pH conditions. However, high sulfur contents and ash yields in a large number of the samples denote organic matter accumulation within a topogenous mesotrophic marginal limno-telmatic mire. Plant material accumulated at or very close to the water surface in a predominantly water-logged environment, indicated by strong gelification. The initial oxidizing conditions were quickly shifted to reductive settings due to flooding of the peat surface with possible seasonal dynamics.</div><div>Low maturity of the organic matter and limited hydrocarbon generation potential are evident from the low vitrinite reflectance (avg. Ro = 0.52 %), biomarker parameters and Rock-Eval data.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"308 ","pages":"Article 104843"},"PeriodicalIF":5.6,"publicationDate":"2025-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144621965","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":"Relationship between vitrinite reflectance, fluoresence red/green quotients, apatite fission tracks and temperature by joint inversion of three wells","authors":"Søren B. Nielsen,&nbsp;Oskar Hagelskjær,&nbsp;Hamed Sanei","doi":"10.1016/j.coal.2025.104832","DOIUrl":"10.1016/j.coal.2025.104832","url":null,"abstract":"<div><div>Thermal maturity assessment in sedimentary basins often relies on thermal indicators of varying quality and sensitivity, frequently available in an uneven distribution across wells. To improve interpretative reliability and reduce the influence of local statistical variability, we apply a joint inversion approach to thermal maturity data from three wells situated in contrasting geological settings. One well, Aars-1, located in the Danish Basin of the eastern North Sea, is constrained by high-quality data including present-day temperature, vitrinite reflectance (VRo), red-to-green (R/G) fluorescence quotients, and apatite fission track (AFT) ages. The other two wells, from the northwestern Black Sea Basin, contain VRo and R/G data but lack temperature and AFT records.</div><div>All wells contribute to constraining a kinetic model for the R/G quotient and the thermal evolutiuon of the Black Sea wells. The resulting models yield predicted present-day bottom hole temperatures of approximately 100 °C at 4000 m depth, consistent with values from independent studies in the region. The thermal immaturity of the Black Sea wells is attributed to low background heat flow and high sedimentation rates. In the immature to early mature maturity window, a linear relationship is established between VRo and R/G, described by the equation: VRo = 1.3239 × R/G – 0.2352, valid within the calibration range of 0.43 &lt; R/G &lt; 0.73 and 0.33 &lt; VRo &lt; 0.73. Based on this relationship, the previously reported VRo discontinuities at the base of the Black Sea wells are likely artefactual.</div><div>This study demonstrates the value of combining independent thermal indicators across multiple wells and depositional settings. The approach enhances the robustness of thermal history reconstructions and offers a practical framework for evaluating relative heat flow and maturity in basins with incomplete or uneven datasets. Particularly, the R/G quotient, derived from autochthonous alginite deposited within the basin, is less affected by transport-related degradation than VRo and may offer a more representative measure of in-place thermal maturity, particularly in high-sedimentation environments.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"308 ","pages":"Article 104832"},"PeriodicalIF":5.6,"publicationDate":"2025-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144515591","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}