International Journal of Coal Geology最新文献

{"title":"Shale oil potential and mobility in low- to medium-maturity lacustrine shales: A case study of the Yanchang Formation shale in southeast Ordos Basin, China","authors":"Huairen Cao ,&nbsp;Jun Shi ,&nbsp;Zhao-Wen Zhan ,&nbsp;Hao Wu ,&nbsp;Xiaoyu Wang ,&nbsp;Xin Cheng ,&nbsp;Haolin Li ,&nbsp;Yan-Rong Zou ,&nbsp;Ping'an Peng","doi":"10.1016/j.coal.2023.104421","DOIUrl":"10.1016/j.coal.2023.104421","url":null,"abstract":"<div><p><span><span><span>Oil mobility is essential for the evaluation of shale oil resources, yet there has been limited research conducted on the oil mobility of low- to medium-maturity lacustrine shale. This study integrates multiple methodologies such as </span>organic geochemistry, </span>mineralogy, oil-kerogen adsorption-swelling experiments, and </span><em>in-situ</em><span> conversion process (ICP) models to evaluate the mobility and potential for shale oil in the lacustrine shale of the Yanchang Formation in the Yaoqu 1 (YQ1) well situated in the southeastern region of the Ordos Basin. The Chang 7 shales are categorized as highly favorable source rocks, nonetheless, the oil contained within these layers predominantly exists in an adsorbed-swelling state, resulting in limited mobility as indicated by the oil saturation index, a modified oversaturation index, and production index. Therefore, the utilization of existing conventional techniques for shale oil exploitation is not viable for the Chang 7 shale characterized by low to medium maturity in the study area. Nevertheless, during the ICP, the quantity and mobility of oil within the Chang 7 shales exhibit a substantial increase as temperature rises. Moreover, once the Chang 7 type II shales reach a maturity level of around 0.91%R</span>_o, they demonstrate noteworthy prospects for shale oil production. The findings of this study serve as a valuable reference for guiding the advancement of <em>in-situ</em> conversion process technology in the study area, while also offering substantial evidence for addressing the intricate challenge of crude oil mobility in low- to medium-maturity lacustrine shale reservoirs.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138635017","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 and geochemistry of the Devonian-Mississippian bakken formation, Williston Basin, North Dakota","authors":"Zain Abdi,&nbsp;Susan M. Rimmer","doi":"10.1016/j.coal.2023.104420","DOIUrl":"10.1016/j.coal.2023.104420","url":null,"abstract":"<div><p><span>The Devonian–Mississippian (D–M) black shales<span> of the Bakken Formation are of interest as a hydrocarbon source due to their high total organic carbon<span> (TOC; 2.2–17.4%) content. The Upper and Lower Members of the Bakken Fm. are shallow marine (100–150 m) sequences. Thirty samples were selected for maceral identification, kerogen typing, and solid bitumen reflectance (SBR</span></span></span>_o<span><span><span>) based on TOC content and down-core spacing. The shales contain alginite, bituminite, abundant solid bitumen (SB), and minor amounts of </span>inertinite. Solid bitumen increases in quantity with increasing </span>thermal maturity<span>. Pyrolysis (85 samples) provided S1 (avg. 8.0 mg HC/g rock), S2 (avg. 24.3 mg HC/g rock), hydrogen index (HI; avg. 201 mg HC/g TOC), oxygen index (OI; avg. 7 mg CO</span></span>₂/g TOC), and R_o (0.60–1.03%) calculated from T_max. Plots of HI vs. OI and HI vs. T_max (°C) were used to assess kerogen type but are not consistently in agreement with the petrographic assessment. Some samples from more thermally mature cores plot as Type III (vitrinite) kerogen instead of Type II (alginite and bituminite) kerogen, the latter confirmed through petrographic observations of lower maturation samples. This is largely due to increased SB in more thermally mature samples (R_o = 0.83–1.03%), as SB is known to have a lower HI content than Type II kerogen. Petrographic data show more alginite and bituminite (19–55%) in the thermally less mature samples (R_o = 0.60–0.83%) compared to more dispersed SB (67–86%) and less alginite and bituminite (&lt;1%) in the more thermally mature samples (R_o = 0.89–1.01%).</p><p><span>Early research on the Bakken Fm. reported lower than expected vitrinite reflectance<span> values and attributed them to vitrinite “suppression”. The scarcity of vitrinite and abundance of SB suggest that early work likely reported reflectance on SB. Recent attempts to assess the thermal maturity of the Bakken black shales have converted SBR</span></span>_o to vitrinite reflectance equivalence (V_RE). However, there are multiple SB populations present in these shales and it is not always clear which SB populations were included, possibly contributing to error. In the current study, only smooth, homogenous SB was measured (0.68–1.14% SBR_o) and V_RE<span> values calculated (0.54–1.49%) to assess thermal maturity from the basin margin to the depocenter<span>; inclusion of measurements on granular, heterogeneous SB (14–21 vol%), which are ∼53% lower than those for smooth, homogenous SB (3–12 vol%), results in lower mean reflectances, especially in more mature samples. Vitrinite reflectance equivalent data calculated using the D–M New Albany Shale equation of Liu et al. (2019) agrees with liptinite fluorescence and Rock-Eval R</span></span>_o, whereas V<sub>RE</s","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2023-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138635014","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":"Exploring the uncertainty of machine learning models and geostatistical mapping of rare earth element potential in Indiana coals, USA","authors":"Snehamoy Chatterjee ,&nbsp;C. Özgen Karacan ,&nbsp;Maria Mastalerz","doi":"10.1016/j.coal.2023.104419","DOIUrl":"10.1016/j.coal.2023.104419","url":null,"abstract":"<div><p><span>Rare earth elements and </span>yttrium<span><span><span><span> (REEs) have a wide range of applications in high- and low-carbon technologies. The strategic significance of REEs has grown due to their expanding applications in manufacturing industries and the constrained availability of these essential resources. This research explores the applicability of machine learning models and their uncertainty for assessing the REE potential in coal beds using various coal parameters as inputs. The work focuses on developing a predictive model based on geological variables, excluding considerations related to potential shifts in the commodities market. The Indiana Coal Quality Database was used as the data source. The promising and unpromising indicators derived from the outlook coefficient of samples from the database were used as the REE potential indicator for machine learning classification models. The filter-based approach with bootstrap was used to evaluate the importance of the coal parameters and their prediction uncertainties. Four </span>machine learning methods (linear </span>discriminant analysis (LDA), random forest (RF), </span>support vector machine<span> (SVM), and artificial neural networks (ANN), a data balancing and augmentation approach (Synthetic Minority Over-sampling Technique), and bootstrap resampling techniques were used for building the models and evaluating their prediction capabilities under uncertainty. It was determined that the SVM bootstrap model with ten-times balanced and augmented data provided superior results compared with other models. Finally, stochastic spatial maps of the REE potential within the coal basin were generated using sequential indicator simulation. The spatial maps of the REE potential showed that a 29% area of the Indiana section of the Illinois coal basin has economic potential of REEs, with 90% confidence.</span></span></p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2023-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138563376","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":"Assessing biochar's permanence: An inertinite benchmark","authors":"Hamed Sanei ,&nbsp;Arka Rudra ,&nbsp;Zia Møller Moltesen Przyswitt ,&nbsp;Sofie Kousted ,&nbsp;Marco Benkhettab Sindlev ,&nbsp;Xiaowei Zheng ,&nbsp;Søren Bom Nielsen ,&nbsp;Henrik Ingermann Petersen","doi":"10.1016/j.coal.2023.104409","DOIUrl":"10.1016/j.coal.2023.104409","url":null,"abstract":"<div><p>The natural removal of carbon dioxide and its permanent storage by the Earth system occurs through (i) inorganic carbon and (ii) organic carbon pathways. The former involves the “mineralization” of carbon and formation of carbonate minerals, whereas the latter employs the “maceralization” or natural carbonization of biomass into the “inertinite maceral”. The production of biochar is a carbon dioxide removal (CDR) method that imitates the geological organic carbon pathway, using controlled pyrolysis to rapidly carbonize and transform biomass into inertinite maceral for permanent storage. Therefore, the main challenge in assessing biochar's permanence is to ensure complete transformation has been achieved.</p><p>Inertinite is the most stable maceral in the Earth's crust and is hence considered an ultimate benchmark of organic carbon permanence in the environment. Therefore, this study aims to measure the degree of biochar's carbonization with respect to the well-established compositional and microscopic characteristics of the inertinite. The random reflectance (R_o) of 2% is proposed as the “inertinite benchmark” (IBR_o2%) and applied to quantify the permanent pool of carbon in a biochar using the R_o frequency distribution histogram. The result shows that 76% of the studied commercial biochar samples have their entire R_o distribution range well above IBR_o2% and are considered pure inertinite biochar. The oxidation kinetic reaction model for a typical inertinite biochar indicates a time frame of approximately 100 million years for the degradation and loss of half of the carbon in the biochar. This estimate assumes exposure to a highly oxidizing environment with a constant surface temperature of 30°C, highlighting the inherent “permanent” nature of the material. In a less hostile environment, the expected permanence of inertinite is generally anticipated to be even longer.</p><p>In addition to the inertinite that constitutes the largest fraction of the typical commercial biochar, an incompletely carbonized biochar may contain up to three other organic pools in descending order of stability. The relative concentration of these pools in a biochar can be quantified by a combination of geochemical pyrolysis and random reflectance methods. Furthermore, the R_o can be used to calculate the carbonization temperature (CT ^oC) of a biochar, which is the maximum temperature to which biochar fragments have been exposed during pyrolysis. This indicator provides important information about the efficiency of the carbonization process and subsequently the biochar's stability, with respect to production temperature (PT ^oC), heating residence time, and thermal diffusivity.</p></div><div><h3>Short summary</h3><p>The Earth's carbon dioxide removal and storage occur via inorganic and organic pathways: mineralization and maceralization. Biochar, imitating the organic pathway, unde","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2023-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516223002276/pdfft?md5=dc1bacc6cbaabf1948ff24e9222934bf&pid=1-s2.0-S0166516223002276-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138563488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mineralogical and elemental composition of the Middle Miocene coal seams from the Alpu coalfield (Eskişehir, Central Türkiye): Insights from syngenetic zeolite formation","authors":"Ali İhsan Karayiğit ,&nbsp;Rıza Görkem Oskay ,&nbsp;Patricia Córdoba Sola ,&nbsp;Yılmaz Bulut ,&nbsp;Mete Eminağaoğlu","doi":"10.1016/j.coal.2023.104408","DOIUrl":"10.1016/j.coal.2023.104408","url":null,"abstract":"<div><p><span><span><span>This study focuses on determining mineralogical and elemental compositions of coal seams (to the upwards, D, C, B, A, and S0) within seven coal exploration wells from the Alpu coalfield (Eskişehir, Central Türkiye). Furthermore, the special goal of the study is a comparative analysis of the relations between the elements by using agglomerative </span>hierarchical clustering<span><span> algorithm with different linkage methods as well as different similarity measures. Clay minerals and quartz are commonly detected as abundant to dominant phases, while natural zeolite<span> formations were detected in the studied seams C, B, A, and S0. The SEM-EDX data shows that clinoptilolites in zeolite minerals were observed within the organic matter, while crystalline and non-crystalline </span></span>analcime<span> minerals along with syngenetic authigenic rhomboid K-feldspars were only detected in the seam A from one studied well. The existence of some micron-sized minerals such as apatite, </span></span></span>monazite<span><span>, and Ti-oxides within the smectite matrix and the measurable amount of Ti in smectite imply that alteration of epiclastic and contemporaneous volcanic inputs was developed under weak acidic to neutral conditions during peat accumulation. The lack of natural zeolite and </span>carbonate minerals<span> in the seam D could be an indicator of weak acidic to neutral conditions and semi-closed hydrogeological conditions. Nevertheless, the alkalinity of mire water, water table, and hydrogeological regime seem to be variable during the accumulation of precursor peats of seams C, B, A, and S0. In turn, alteration of volcanic inputs was observed under neutral to weak alkaline conditions and semi-closed to closed hydrogeological regime. Hence, syngenetic authigenic, micron-sized clinoptilolites were formed. Moreover, the existence of authigenic rhomboid K-feldspars and syngenetic authigenic analcimes in certain exploration well could suggest local increases on dissolved Na</span></span></span>⁺<span><span><span> concentrations, alkalinity, and water table. Except for volcanogenic origin for minerals, accessory micron-sized minerals, like chromite<span><span>, pentlandite, and </span>allanite grains presumably originated from clastic influxes of ophiolitic rocks in the basement into palaeomires. The variations in mire </span></span>water chemistry<span><span> and clastic-influx source area could also control the elemental enrichments in the studied seams. Epiclastic and contemporaneous volcanic inputs into palaeomires seem to control enrichments of Li, B, Sc, and Ti in coal samples, while clastic influx from ophiolitic rocks into palaeomires caused to enrichments of Cr, V and Ni. Furthermore, the liberated Ba, Sr, and As ions from the alteration of epiclastic and contemporaneous volcanic inputs are absorbed by syngenetic zeolite minerals, while anoxic conditions in the palaeomires resulted in precipitation","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138563690","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":"Combining atomic force microscopy and nanoindentation helps characterizing in-situ mechanical properties of organic matter in shale","authors":"Jianfeng Wang ,&nbsp;Joanna Dziadkowiec ,&nbsp;Yuke Liu ,&nbsp;Wenmin Jiang ,&nbsp;Yijun Zheng ,&nbsp;Yongqiang Xiong ,&nbsp;Ping'an Peng ,&nbsp;François Renard","doi":"10.1016/j.coal.2023.104406","DOIUrl":"10.1016/j.coal.2023.104406","url":null,"abstract":"<div><p>The quantification of mechanical properties of organic matter in shale is of significance for the fine prediction and characterization of shale reservoir's mechanical properties. Due to the micron-sized and dispersed distribution of organic matter particles in shale, the accurate evaluation of the actual mechanical response remains challenging. This work focuses on shale from Wufeng-Longmaxi Formation, which is the main shale gas exploration and development formation in China. A method based on atomic force microscopy (AFM) with an optical microscope (i.e., in-situ AFM technique) is presented to locate the organic matter in-situ and then visualize and quantify its mechanical properties using AFM Young's modulus mapping. The merits and limitations for determining the mechanical properties of organic matter in shale between the AFM and the more conventional nanoindentation technique are discussed. Results show that combining in-situ nanoindentation and in-situ AFM mapping provides more accurate description of the mechanical properties of organic matter in shale than traditional grid indentation methods with low spatial resolution. The Young's moduli of organic matter calculated from nanoindentation are around twice smaller than those obtained from AFM measurements mainly because the elasto-plastic deformation zone of organic matter in nanoindentation tests is larger and can be additionally affected by the presence of inorganic particles and/or larger micro-pores in organic matter. The Young's modulus and hardness of graptolite in the shale obtained by nanoindentation are slightly larger than those of solid bitumen at the same thermal maturity. Both in-situ AFM and in-situ nanoindentation results show that the mechanical strength of organic matter increases with increasing maturity. Overall, the presented approach shows a great potential for accurate and in-situ measurement of the mechanical properties of organic matter in shale at the nanoscale, which may be beneficial to the development of rock mechanical models for the accurate evaluation of the actual mechanical properties of shale.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516223002240/pdfft?md5=47bbf5b76096164e9e474b4c76c9210d&pid=1-s2.0-S0166516223002240-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138468763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enrichment of rare earth elements in epigenetic dolomite occurring in contact metamorphosed Witbank coals (South Africa)","authors":"Ofentse M. Moroeng,&nbsp;Bridgette Murathi,&nbsp;Nicola J. Wagner","doi":"10.1016/j.coal.2023.104405","DOIUrl":"10.1016/j.coal.2023.104405","url":null,"abstract":"<div><p>The emplacement of igneous intrusions into coal alters both the organic and inorganic components, and may result in the addition of specific components, including rare earth elements (REEs), into the country rock. Previous studies on the intruded coals of the Main Karoo Basin (South Africa) have mainly focused on understanding changes to their organic fraction despite the likelihood that the inorganic composition is also affected, as demonstrated by others studying intruded coals elsewhere in the world. This study reports on the effects of a 0.4 m thick dolerite dyke on the mineralogy and geochemistry of Witbank coals, South Africa. Coal samples were collected at 0.25 m intervals on both sides of the dyke (west and east); in addition to the intruded coals, an unaltered coal from the same seam and a sample of the dolerite were included. The samples were assessed using petrography, X-Ray Diffraction, X-Ray Fluorescence, Scanning Electron Microscopy, and Inductively Coupled Plasma Mass Spectrometry following sequential leaching, focusing on REEs for the latter analysis. Inertinite is the main maceral group in the coal samples; as a result, the impact of the intrusion on the organic fraction is compared using mean random total reflectance (%RoTmr). Total reflectance increases from 1.65 %RoTmr (for the unaltered coal) to 4.17 %RoTmr closer to the dyke on the western side. In contrast, the eastern side reports lower values (max. 1.94 %RoTmr). Similar to reflectance, dolomite is higher in samples from the western side of the dyke. Dolomite is also found in the unaltered coal (4 wt%) and the dolerite sample (15 wt%). Syngenetic dolomite and a weak positive Gd anomaly for the unaltered coal (ΣREE = 83.7 μg/g) suggest the presence of acidic groundwaters during peatification. Subsequently, the coals were also affected by hydrothermal activity, related to the intrusion of the dolerite dyke. For the intruded coals, dolomite (fracture-infilling) and ΣREEs are higher on the western side, at a maximum of 24 wt% and 153.0 μg/g, respectively. Carbonate associated REEs are higher for the intruded coals than the total for the dolerite (ΣREE = 23.3 μg/g). This reflects the incompatibility of REEs with early-formed minerals in the dolerite, concentrating them in the residual melt. Increased reflectance and dolomite (and associated REEs) in coals from the western side suggest pronounced hydrothermal activity, related to the availability of accommodation space (i.e., fractures).</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516223002239/pdfft?md5=cd8a781d5b820d293cb46b8961366c9d&pid=1-s2.0-S0166516223002239-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138468754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Weathering alterations of coal mining wastes geochemistry, petrography, and mineralogy, a case study from the Janina and Marcel Coal Mines, Upper Silesian Coal Basin (Poland)","authors":"M.J. Fabiańska ,&nbsp;J. Ciesielczuk ,&nbsp;M. Szczerba ,&nbsp;M. Misz-Kennan ,&nbsp;D. Więcław ,&nbsp;E. Szram ,&nbsp;Á. Nádudvari ,&nbsp;Z. Ciesielska","doi":"10.1016/j.coal.2023.104407","DOIUrl":"10.1016/j.coal.2023.104407","url":null,"abstract":"<div><p><span><span><span>Weathering-caused alterations in coal mining<span> waste geochemistry, </span></span>petrography, and </span>mineralogy<span><span><span> occurring in the known time span of 1998–2018 in the temperate climate<span><span> of Poland were investigated. A series of coal mining waste rocks representing two parts of the Upper Silesian Coal Basin (USCB), differing in </span>coalification<span> stage, i.e., corresponding to sub-bituminous and bituminous coals, have been selected to find how the level of organic matter conditionates the weathering. Differences in organic matter content, petrographic composition, rock mineralogy and </span></span></span>inorganic geochemistry were also taken into account. Whereas organic petrography, including </span>vitrinite reflectance<span> values, do not show significant weathering signs, apart from irregular cracks and, in very rare cases, paler in color oxidation<span> rims, organic geochemistry has been affected due to low-temperature secondary processes, including increased oxygen index values, particularly in less mature coal mining wastes. Biomarker distribution has been changed to the largest extent, with partial removal of </span></span></span></span><em>n</em><span>-alkanes possibly due to biodegradation of organic matter and water-washing of lighter polycyclic aromatic hydrocarbons, including alkyl naphthalenes<span>. Organic matter of lower maturity in coal mining wastes from the USCB eastern part, as more reactive, showed a higher level of secondary transformations. Minerals formed during weathering due to time and storage on dumps were mainly oxidation products of iron sulphides<span><span>: goethite and </span>jarosite<span><span>; however, most of the minerals have not been altered. Thus, despite physical changes in coal mining wastes, such as increased brittleness, decreasing fragment size and surface color change, there are only limited changes in </span>inorganic chemistry and mineralogy. This indicates that low-temperature processes do not favour the inorganic elements release to the environment and points out that measures to prevent self-heating within the dumps are the most vital part of post-mining activity leading to the best scenario - slow low-temperature weathering of coal mining wastes.</span></span></span></span></p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138468830","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":"Formation of boehmite through desilication of volcanic-ash-altered kaolinite and its retention for gallium: Contribution to enrichment of aluminum and gallium in coal","authors":"Shuai Zhang ,&nbsp;Tangchen Yuan ,&nbsp;Bo Sun ,&nbsp;Lei Li ,&nbsp;Xiaojun Ma ,&nbsp;Songlin Shi ,&nbsp;Qinfu Liu","doi":"10.1016/j.coal.2023.104404","DOIUrl":"10.1016/j.coal.2023.104404","url":null,"abstract":"<div><p><span>Multiple parting bands within Permo–Carboniferous coal that are generally enriched in critical metals in the northern North China have been confirmed to be altered from volcanic ash (tonsteins). The tonsteins and adjacent coal in some areas contain boehmite with varying contents. Whether or not the boehmite has a relationship with the volcanic-ash-altered </span>kaolinite<span><span> remains poorly understood. Herein, petrographical, mineralogical, whole-rock geochemical, and in-situ elemental analyses, combined with U–Pb–Hf isotopic analysis of </span>zircon<span>, were performed for the boehmite-bearing/rich partings and coal collected from the eastern edge of the Datong and Jungar coalfields. Except for the boehmite, well-ordered kaolinite is predominant in the parting samples, where the columnar/tabular and vermicular kaolinite are commonly present. Additionally, the zircons separated from the representative parting and coal samples are mostly igneous origin with only one age population of ca. 300 Ma, almost same with the depositional age of the coal, suggesting that the kaolinite in the inorganic constitutes of the investigated coal seams<span> were mainly altered from volcanic ash. Numerous fine-grained boehmite exhibit textural features of replacement for columnar/tabular and vermicular kaolinite along the cleavage cracks in the parting samples, suggesting that such boehmite were formed from desilication of volcanic-ash-altered kaolinite. The tonsteins and coal along the eastern edge of the coalfields were uplifted and influenced by fault activities due to Indosinian and Yanshan orogeny, which were probably experienced intensive leaching by silica-undersaturated percolating water and groundwater, resulting in desilication of volcanic-ash-altered kaolinite and precipitation of residual Al as boehmite. The Ga, preserved in the alumina octahedral sheets of volcanic-ash-altered kaolinite, were retained by boehmite due to its very similar geochemical behavior with Al. The formation of boehmite and its retention for Ga made a contribution to the genesis of high–Al–Ga coal in the northern North China.</span></span></span></p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138449908","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 minerals in a self-heating coal-waste dump in Upper Silesia, Poland: Structure, formation pathways and environmental issues","authors":"Ádám Nádudvari ,&nbsp;Tomasz Krzykawski ,&nbsp;Mariola Jabłońska ,&nbsp;Monika Fabiańska ,&nbsp;Katarzyna Skrzyńska ,&nbsp;Anna Abramowicz ,&nbsp;Maria Książek ,&nbsp;Justyna Ciesielczuk","doi":"10.1016/j.coal.2023.104403","DOIUrl":"10.1016/j.coal.2023.104403","url":null,"abstract":"<div><p><span><span>The study presents research on the unusual appearance of purple-colored organic minerals, ravatite (phenanthrene) and freitalite (anthracene), occurring in the migrating front wall of a heating spot in the Bytom coal waste dump<span> (Upper Silesia Coal Basin, Poland). These minerals are known to be sublimation products, but their formation mechanism remains unclear. Additional minor components are fluorene, dibenzothiophene, naphthothiophenes, </span></span>dibenzofuran, and their alkyl-derivatives, and </span><em>n</em>-C₁₇ – <em>n</em>-C₂₀<span><span> alkanes. Temperatures were surprisingly low (30–60 °C on the surface) at the sampling sites, though such large amounts of Polycyclic Aromatic Hydrocarbons (PAHs) typically form in a burning environment where temperatures reach 800–1000 °C. The relatively low temperatures suggest that the primary mechanism of formation was not direct evaporation (desublimation) of </span>phenanthrene<span><span><span> and anthracene from coal-waste gases but that their occurrence may reflect a catalytical polymerization of ethylene on iron (III) chloride synthesized in a reaction between </span>HCl<span> and a common Fe mineral such as goethite. Subsequently, both minerals crystallized on the cold dump surface. High concentrations of phenanthrene and anthracene in self-heating products, testified by ravatite and freitalite, mean that self-heating of coal waste may significantly increase backgrounds of </span></span>environmental pollution by PAHs.</span></span></p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2023-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138450077","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}