International Journal of Coal Geology最新文献

{"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":"2025-12-21","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":"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":"2025-12-18","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":"Changes in optical properties and morphology of anthracites oxidized under different conditions: In HNO3, air and plasma oxygen","authors":"Sławomira Pusz ,&nbsp;Anna Hercog ,&nbsp;Karolina Olszowska","doi":"10.1016/j.coal.2025.104926","DOIUrl":"10.1016/j.coal.2025.104926","url":null,"abstract":"<div><div>Anthracites, due to their highly ordered internal structure, are chemically quite inert and thus difficult to process. However, for various applications of anthracites, including as precursors of carbon materials with specific properties, improving their processability is often necessary. For this purpose, various pretreatments are used, among which oxidation methods are of great importance. This work aimed to study the influence of oxidation using three different methods (in concentrated HNO₃, in air at 420 °C, in plasma oxygen) on optical properties and morphology of three anthracites of increasing rank (VIC &lt; MO &lt; DON) from the Lower Silesian Coal Basin and Upper Silesian Coal Basin (Poland) and from Donbass (Ukraine), respectively. Scanning electron microscopy (SEM) with energy dispersive X-ray spectrometer (EDS), Raman spectroscopy, and light microscopy (imaging and reflectance measurement) allow for following the changes in morphology and optical properties of anthracites after oxidation. In the case of the highest rank DON anthracite, its morphology and optical properties remained almost unchanged following oxidation by all the methods used, except for the narrow oxidation zone created by HNO₃. In the case of lower rank anthracites, MO and VIC, their morphology and optical properties changed significantly under oxidation in HNO₃ and air, but remained unchanged after plasma oxidation. The extent and intensity of the oxidation process were stronger for VIC anthracite than for MO.</div><div>Ultimately, it was shown that the level of anthracite oxidation in HNO₃ and thermal oxidation with air strongly depends on the rank of the anthracite. The nature of the changes in morphology and reflectance parameters also suggests that the liquid agent, HNO₃, acts more intensively but also more closely at the surface of anthracite grains, as it has a lower ability to penetrate deeper into the grains than air. The oxidation level under the influence of oxygen plasma was similar for all anthracites, regardless of their rank.</div><div>Optical properties are very sensitive indicators, which can reveal even very subtle structural changes in anthracites during oxidation, invisible to other research methods. The nature and intensity of changes of optical properties illustrate the extent and level of anthracites' oxidation and can be a useful complement to the results obtained using other research methods for determining anthracites' structural transformations. Due to the growing interest in using anthracite as a potential source of new carbon materials, thorough knowledge of their structural changes resulting from various technological processes, including oxidation, seems to be important from a scientific as well as technological point of view.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"313 ","pages":"Article 104926"},"PeriodicalIF":5.7,"publicationDate":"2025-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145753508","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":"Assessment and integration of different methodologies for the characterisation of carbon aromaticity and structure in biochar","authors":"K. Alami Sounni ,&nbsp;M. Camps-Arbestain ,&nbsp;J. Kaal ,&nbsp;C.J. Tighe ,&nbsp;M.M. Titirici ,&nbsp;G. Siavalas","doi":"10.1016/j.coal.2025.104925","DOIUrl":"10.1016/j.coal.2025.104925","url":null,"abstract":"<div><div>Carbon removal permanence refers to the duration over which carbon remains securely stored across various reservoirs without re-entering the atmosphere. Random reflectance (R_o) has been proposed as a proxy for assessing carbon permanence in biochar. In this study, R_o was measured for 25 plant-derived biochars and compared with (i) the molar H/C ratio, (ii) Raman spectroscopy parameters, and (iii) pyrolysis-GC–MS fingerprints. Four of the biochars showed bimodal R_o distributions, indicating two distinct reflectance populations. A strong relationship was found between mean R_o and H/C (r² = 0.88). Biochars with H/C ≤ 0.40 had mean R_o ≥ 2.3 %, with ≥83 % of the 500 measurement points per sample exceeding 2 % (IBR_o2), except one bimodal sample. This sample, despite mean R_o of 3.72 %, and H/C of 0.37, had only 65 % of measurements &gt; IBR_o2. Based on the fraction &gt; IBR_o2, the biochars were grouped as: Class 1: &lt; 50 %; Class 2: 50–80 %; Class 3: ≥ 80 %. For unimodal biochars, these classes corresponded to mean R_o &lt; 2.0 %, 2.0–2.3 %, and ≥ 2.3 %, and H/C ≥ 0.45, 0.40–0.45, and ≤ 0.40, respectively. Among Raman parameters, saddle intensity effectively distinguished the classes. Mean R_o inversely related to analytical pyrolysis yield (r² = 0.72). Chemical markers (methoxyphenols and (alkyl)phenols) helped explain transitions between classes. The strong correspondence between mean R_o and H/C in unimodal biochars suggests either proxy may suffice in most cases. However, the fraction &gt; IBR_o2 becomes critical for polymodal, Class 2, non-plant feedstock biochars, or when required by certification registries.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"313 ","pages":"Article 104925"},"PeriodicalIF":5.7,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145732129","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":"In loving memory of Deolinda Flores (1958–2025)","authors":"Manuela Marques ,&nbsp;Isabel Suárez-Ruiz ,&nbsp;Lopo Vasconcelos ,&nbsp;Henrique Pinheiro ,&nbsp;João Graciano Mendonça Filho","doi":"10.1016/j.coal.2025.104923","DOIUrl":"10.1016/j.coal.2025.104923","url":null,"abstract":"","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"313 ","pages":"Article 104923"},"PeriodicalIF":5.7,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145732135","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":"2025-12-05","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}

{"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":"2025-12-04","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":"2025-11-30","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":"Hydrothermal enrichment of rare earth elements in Carboniferous–Permian coal-measure kaolins in the Datong Coalfield, North China, linked to Paleo-Asian Ocean evolution","authors":"Shuai Zhang,&nbsp;Yong Ding,&nbsp;Xiliang Zhang,&nbsp;Zhengguo Hu,&nbsp;Qinfu Liu","doi":"10.1016/j.coal.2025.104912","DOIUrl":"10.1016/j.coal.2025.104912","url":null,"abstract":"<div><div>Carboniferous–Permian coals in North China are widely recognized for their enrichment in critical metals, yet the enrichment within their adjacent rocks has received comparatively less attention. Recent investigations have identified rare earth elements and yttrium (REY)-enriched coal-measure kaolins, occurring as partings and floor of coal seams in the southeastern Datong Coalfield. These REY anomalies are of economic interest for potential recovery during kaolin utilization. This study integrates petrological, mineralogical, geochemical, and isotopic geochronological analyses with sequential chemical extraction to determine the origin of the kaolins, the modes of REY occurrence, and their enrichment mechanisms. Zircon U-Pb dating reveals a dominant age peak at ∼300 Ma, consistent with the depositional age of the coal seams. This, together with the presence of volcanic quartz and well-developed columnar/tabular and vermicular kaolinite, indicates a genesis from altered volcanic ash. Zircon geochemistry further suggests that the volcanic ash was derived from continental arc volcanism linked to the southward subduction of the Paleo-Asian Ocean (PAO) beneath the North China Craton (NCC) during the Late Paleozoic. The REY are predominantly hosted in epigenetic siderite and ankerite of hydrothermal origin and in hydrothermally altered kaolinite. Carbon and oxygen isotopic compositions, together with the trace element assemblages enriched in the carbonates, indicate that the hydrothermal fluids were derived from carbonatitic magmas. These magmas formed by partial melting of an enriched mantle that had been metasomatized by carbonate-rich fluids released during dehydration of the subducted PAO slab and its associated sediments. Following PAO closure, the northern NCC transitioned into an extensional tectonic regime during the Middle to Late Triassic. Asthenospheric upwelling triggered partial melting of the metasomatized mantle, generating carbonatitic magmas that intruded along lithosphere-scale faults at the eastern margin of the Datong Coalfield. The evolved hydrothermal fluids infiltrated the coarse-grained coal-measure kaolins and reacted with kaolinite to form carbonate minerals via replacement. The REY and other elements transported by these fluids were incorporated into the crystallizing carbonates and captured by hydrothermally altered kaolinite.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"312 ","pages":"Article 104912"},"PeriodicalIF":5.7,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145593672","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":"Enrichment characteristics, volatilization properties, speciation transformation, and environmental implications of trace elements during coal combustion from Huaibei Coalfield, Anhui, China","authors":"Mengfei Lu,&nbsp;Ruijia Liu,&nbsp;Minglian Shen,&nbsp;Guijian Liu,&nbsp;Hao Hu,&nbsp;Zongfan Xie,&nbsp;Zhen Yue","doi":"10.1016/j.coal.2025.104911","DOIUrl":"10.1016/j.coal.2025.104911","url":null,"abstract":"<div><div>The behavior of trace elements (TEs) during coal combustion is highly temperature-dependent, presenting a dual challenge of environmental risk and resource potential. However, the strategic utilization and effective pollution control of coal ash are hindered by insufficient understanding of how combustion temperature differentially governs the fate of critical and harmful elements. Combining combustion experiments with thermodynamic simulations, this study systematically investigated the impact of temperature (400–1100 °C) on the enrichment, volatilization, and speciation transformation of selected critical (Li, V, Ga, Ge, Zr, and Mo) and harmful elements (Cr, Ni, Cu, Zn, Cd, and Pb) in Huaibei coal, and evaluated their distinct environmental implications. The results show that the elements Li, Ga, Zr and Pb are all slightly enriched or enriched in five coal samples, and their contents in coal ashes are on average more than twice those in raw coals, and up to more than four times. The decomposition of organic matter is completed at 500/600 °C, and kaolinite-quartz-muscovite in the raw coal transform into mullite-quartz in coal ash. Trace elements are mainly stabilized as sulfate (Li, V, Cr, Ni, Cu, Zn, Cd, and Pb) at low temperatures, and partially volatilized as gaseous hydroxides (Li, Ga, Mo, Cr, Ni, Cu, Zn, and Cd) with increasing temperatures, or exist as metal oxides in coal ash (Li, V, Ga, Ge, Zr, Cr, Cu, Zn, and Pb). Principal component analysis (PCA) reveals differential responses of TEs to progressive temperature increases. The generally lower volatility of critical elements compared to harmful elements in coal ash leads to their higher retention, highlighting their potential for resource recovery and the consequent positive environmental benefits. However, the presence of harmful elements in ash also causes tangible negative environmental effects, primarily manifested as increased potential ecological risks with increasing temperatures. Cadmium is identified as the dominant risk contributor capable of reaching high risk levels at elevated temperatures. This study provides scientific basis for the harmless utilization of coal ash resources through temperature regulation.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"312 ","pages":"Article 104911"},"PeriodicalIF":5.7,"publicationDate":"2025-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145560220","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}