International Journal of Coal Geology最新文献

{"title":"Organic petrography, biomarkers, and stable isotope (δ13C, δD, δ15N, δ18O) compositions of liptinite-rich coals","authors":"Bangjun Liu , Achim Bechtel , Ksenija Stojanović , James C. Hower , Cunliang Zhao , Xu Guo","doi":"10.1016/j.coal.2024.104561","DOIUrl":"10.1016/j.coal.2024.104561","url":null,"abstract":"<div><p>Liptinite-rich coals were evaluated using organic petrography, biomarkers, and stable isotopes to investigate their origin and paleoenvironmental significance, particularly, to explore fractionation characteristics of stable isotopes (δ<sup>13</sup>C, δD, δ<sup>15</sup>N, and δ<sup>18</sup>O) between bulk coal, extractable organic matter (EOM), and extracted coal residue (ER). The samples were collected from Cenozoic coal seams from the Yunnan and Liaoning Provinces in China. The samples are characterized by the enrichment of different types of liptinite. The late Pliocene sample YNP (liptinite = 73.5%) is dominated by sporinite and bituminite, whereas the late Pliocene sample YND (liptinite = 65.5%) is characterized by isolated resinite particles and amorphous resinite. The liptinite in the Eocene sample SB (46.0%) is represented by blocky resinite with homogeneous morphology. The differences in distribution and morphology of liptinite are due to the different coal-forming plants and depositional environments, as indicated by the biomarker compositions. Biomarker results indicated that the sample YNP was formed mainly by Pinaceae and angiosperms under oxidizing conditions with bacterial/fungal degradation, whereas the sample YND was derived from the woody parts of gymnosperms with lower contributions of angiosperms under reducing conditions with low microbial activity. The sample SB predominantly originated from Cupressaceae/Pinaceae under reducing conditions with a lack of bacterial/fungal degradation.</p><p>The fractionations of δ<sup>13</sup>C, δD, δ<sup>15</sup>N, and δ<sup>18</sup>O between bulk coal, EOM, and ER in the liptinite-rich coals are different. The δ<sup>13</sup>C values of bulk coal, EOM, and ER are mostly controlled by precursor paleovegetation and isotopic composition of CO<sub>2</sub>. The lower δ<sup>13</sup>C values of samples YNP and YND from the late Pliocene compared to that of the Eocene sample SB resulted from the change of palaeoconditions (e.g., δ<sup>13</sup>C of atmospheric CO<sub>2</sub>, cooling, and decrease of CO<sub>2</sub> concentration). The δ<sup>13</sup>C values of EOM in the samples YNP and YND are about 3‰ lower than δ<sup>13</sup>C values of bulk coal/ER, whereas δ<sup>13</sup>C fractionation between EOM and bulk coal/ER is small (< 0.8‰) in the sample SB, probably due to the very limited microbial/fungal degradation. The δD values of EOM are 50 to 90‰ lower than that of bulk coal/ER within the same sample, reflecting different isotopic compositions of monomeric compounds compared to the macromolecular matrix of kerogen most probably due to differences in H-isotope fractionation during biosynthesis. The δ<sup>15</sup>N of bulk coal and ER show limited fractionation (< 0.5‰) and are mainly controlled by precursor paleovegetation and microbial induced degradation processes. The studied liptinite-rich coals yield higher δ<sup>18</sup>O values than those detected in humic coals. The difference","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"290 ","pages":"Article 104561"},"PeriodicalIF":5.6,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141638132","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":"Decoding paleomire conditions of paleogene superhigh-organic-sulfur coals","authors":"Tushar Adsul ,&nbsp;Molly D. O'Beirne ,&nbsp;David A. Fike ,&nbsp;Santanu Ghosh ,&nbsp;Josef P. Werne ,&nbsp;William P. Gilhooly III ,&nbsp;Paul C. Hackley ,&nbsp;Javin J. Hatcherian ,&nbsp;Bright Philip ,&nbsp;Bodhisatwa Hazra ,&nbsp;Sudip Bhattacharyya ,&nbsp;Ritam Konar ,&nbsp;Atul Kumar Varma","doi":"10.1016/j.coal.2024.104559","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104559","url":null,"abstract":"<div><p>Superhigh-organic‑sulfur (SHOS) coals (coals with organic sulfur content &gt;4 wt%) are unique coal deposits found at a few notable locations in the world. Specific peat accumulation and preservation conditions must be met to form SHOS coals. Organic sulfur is a major constituent of such coals, and it may have various sources depending on the prevailing paleomire conditions. Understanding such paleomire conditions sheds light on the formation mechanisms of SHOS coals. This investigation decodes the paleomire conditions of the Paleogene SHOS coals from Meghalaya, India, using sulfur isotopic compositions (<em>δ</em>³⁴S) of organic sulfur (<em>δ</em>³⁴S_OS) and pyritic sulfur (<em>δ</em>³⁴S_Py) along with organic petrography, pyrite morphology and trace element ratios. Thirty coal samples were collected from the Jaintia Hills in the east, Khasi Hills in the middle, and Garo Hills in the west of Meghalaya. The organic sulfur content in the Garo, Khasi, and Jaintia coals varies from 1.0 to 3.3 wt%, 1.4 to 13.8 wt%, and 1.0 to 7.2 wt%, respectively. Further, after separation from pyritic sulfur and sulfate sulfur phases, the organic sulfur content ranges from 54.4 to 69.2%, 63.8 to 79.9%, and 59.3 to 73.8%, in the Garo, Khasi, and Jaintia Hills, respectively, suggesting the SHOS nature of these coal samples. The <em>δ</em>³⁴S_Py varies from −29.3 ‰ to +5.7 ‰, −21.3 ‰ to +27.3 ‰, and  −12.1 ‰ to −4.3 ‰, in the Jaintia, Khasi, and Garo Hills, respectively, while the <em>δ</em>³⁴S_OS fluctuates from −4.6 ‰ to +3.7 ‰, −9.3 ‰ to +7.8 ‰, and − 9.0 ‰ to −5.0 ‰, respectively. The <em>δ</em>³⁴S values of pyrite and organic sulfur (OS) in Jaintia coals are ³⁴S depleted compared to seawater sulfate (+22 ‰), leading to fractionations in the range of −51.3 ‰ to −16.3 ‰ (mean − 31.6 ‰) and − 26.6 ‰ to −18.3 ‰ (mean − 23.1 ‰) for pyritic and organic sulfur (OS), respectively. Pyrite in Khasi coals show a relatively heavier <em>δ</em>³⁴S composition averaging at −20.5 ‰, whereas organic sulfur (OS) isotope compositions range from −31.3 ‰ to −14.2 ‰ with a mean of −22.6 ‰. Pyrite and OS in the Garo coals are depleted compared to seawater sulfate. Isotope variations in the Jaintia, Khasi, and Garo coals indicate microbial sulfate reduction (MSR) of seawater sulfate. Large isotopic fractionations between Eocene seawater sulfate and pyritic sulfur (<em>Δ</em>³⁴S_{SO4Eocene – pyrite} = up to −51.3 ‰; mean − 31.6 ‰) in Jaintia coals indicate their possible formation in the water column/near the sediment-seawater interface (open system) and also hint toward dissimilatory sulfate reduction pathways that prevailed under anoxic redox conditions. However, mean values of <em>Δ</em>³⁴S_{SO4Eocene – pyrite} (−20.5 ‰) in the Khasi coals imply pyrite formation deeper in the sediments (more closed system) under d","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"290 ","pages":"Article 104559"},"PeriodicalIF":5.6,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141582360","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":"Weathering-induced organic matter enrichment in marine-continental transitional shale: A case study on the early Permian Taiyuan Formation in the Ordos Basin, China","authors":"Zhengfu Zhao ,&nbsp;Caineng Zou ,&nbsp;Shifeng Dai ,&nbsp;Zhaojie Guo ,&nbsp;Yong Li ,&nbsp;Arne Thorshøj Nielsen ,&nbsp;Niels Hemmingsen Schovsbo ,&nbsp;Zhenhua Jing ,&nbsp;Hanlin Liu ,&nbsp;Ming Yuan ,&nbsp;Fangliang Fu ,&nbsp;Jia Yin ,&nbsp;Fujie Jiang","doi":"10.1016/j.coal.2024.104562","DOIUrl":"10.1016/j.coal.2024.104562","url":null,"abstract":"<div><p>A comparative analysis of the factors controlling organic matter (OM) enrichment between marine-continental transitional (transitional hereafter) and marine or lacustrine shales is lacking. The early Permian Taiyuan Formation in the Ordos Basin, deposited during a shift from marine to continental settings in northern China, provides a unique opportunity to unravel the differences in OM enrichment mechanisms among these shales. The Taiyuan Formation is characterized by high TOC content (average 4.50%) and kerogen type II₂-III. Most samples are thermally mature with a few high to post-mature samples relating to the Late Jurassic–Early Cretaceous Yanshanian magmatism. Rare earth elements and yttrium (REY) are dominated by light- and medium-types enrichments, with distinctly positive Gd anomaly, likely due to seawater incursion. A warm and humid climate prevailed during deposition of the Taiyuan Formation, consistent with the tropical-subtropical location of the North China Plate in the early Permian. The climatic conditions promoted intense continental weathering as reflected by high Th/Sc ratios, chemical index of alteration values, and feldspar alteration to scaly kaolinite. The V/(V + Ni) ratio is inconsistent with the other redox proxies, presumably due to variations in the redox buffer supply in the transitional facies (e.g., OM and pyrite), varying burial rates and dissimilar redox potential of different elements. Hence, this proxy should be interpreted with caution in such settings. Most redox proxies indicate oxic bottom water during deposition of the Taiyuan Formation transitional shale, in contrast to typical OM enriched marine and lacustrine shales where redox stratification or euxinic conditions are common. Instead, the dominant factor for OM enrichment in transitional shales appears to have been a high influx of terrestrial weathering products, including abundant higher-plants OM, associated with preservation of OM due to rapid burial. This process minimizes the detrimental effects of oxic conditions on OM accumulation in the transitional shale facies. This mechanism may hold relevance for analogous basins elsewhere.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"291 ","pages":"Article 104562"},"PeriodicalIF":5.6,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141703618","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":"Sulfur stable isotopes in Paleogene coals of Northeast India","authors":"Vivek Kumar ,&nbsp;Dibyendu Paul ,&nbsp;Sudhir Kumar","doi":"10.1016/j.coal.2024.104550","DOIUrl":"10.1016/j.coal.2024.104550","url":null,"abstract":"<div><p>Sulfur stable isotope signatures are instrumental in tracing the sources and tracking the movement of sulfur in different environmental compartments, besides providing vital insights into the origin and transport dynamics. Sulfur stable isotope composition in coal can give valuable information regarding sulfur sources and the process of sulfur incorporation in coal. The present study was conducted to determine the total sulfur content and sulfur isotopic composition for bulk sulfur (bulk S δ³⁴S) in Oligocene and Eocene coal samples from coal mines and a few coal stockings in northeast India. The results revealed that the total sulfur content in coal samples varied between 1.03 and 4.80 (wt%) with an average value of 2.64 wt%. The bulk S δ³⁴S in coal samples exhibited a wide range between −4.66 ‰ to 14.78 ‰ (VCDT). Oligocene coal samples from mines in Arunachal Pradesh, Assam, and Nagaland were enriched with heavier sulfur isotopes relative to Eocene coal samples from the Jaintia Hills region of Meghalaya. A moderate positive correlation was observed in the Oligocene coal samples, in contrast to the moderate negative correlation found in the Eocene coal samples. The bulk S δ³⁴S values and sulfur content in coal samples from coal stockings matched closely with Assam and Meghalaya mine samples. The findings of this study can be used to track the sources and movement of coal sulfur in various environmental compartments, besides providing valuable information about sulfur sources, the process of sulfur incorporation in coal, and the depositional environment.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"290 ","pages":"Article 104550"},"PeriodicalIF":5.6,"publicationDate":"2024-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141403976","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":"Insights on the regional thermal evolution from semianthracite petrology of the Fengfeng coalfield, China","authors":"Na Wang ,&nbsp;Joan S. Esterle ,&nbsp;Sandra Rodrigues ,&nbsp;James C. Hower ,&nbsp;Shifeng Dai","doi":"10.1016/j.coal.2024.104548","DOIUrl":"10.1016/j.coal.2024.104548","url":null,"abstract":"<div><p>Igneous intrusions induce alterations in coal and minerals. Alteration degree depends upon the in-situ coal rank and maceral composition, the intrusion temperature, heat source proximity, and intrusion size. In the Permo-Carboniferous Fengfeng coalfield, coal rank increases over some 50 km distance south to north from high volatile bituminous coal to anthracite. The coal seams were commonly intruded, and the regional elevation of rank was augmented by Jurassic-Cretaceous igneous intrusions, not just burial coalification. The petrographic examination of a semianthracite from the Dashucun mine in the north of the Fengfeng coalfield shows development of coke microstructure and increased reflectance approaching the dike in the No. 2 Seam. Based on 11 samples at 50-cm horizontal intervals, random vitrinite reflectance value (R_r) declines from 5.41% at the contact to the background value of 2.05% at 5-m distance from the contact. Towards the dike, vitrinite anisotropy increases and the microtexture shows development of circular, coarse mosaic, and ribbon anisotropic coke textures and devolatilization vacuoles. Natural coke textures respond to an estimated temperature &gt; 570 °C at the intrusion/coal contact. However, the occurrence of coke structures within a semianthracite reveals a local and regional thermal evolution. Coke textures suggest that coal rank was high volatile A bituminous coal at the time of intrusion. This has implications for burial history, heating, and subsidence rates. Assuming a paleogeothermal gradient of 40 °C/km, high volatile A bituminous coal (1% R_r) would have been buried to 3 km at the time of the Jurassic intrusion. The intrusion metamorphosed high volatile bituminous coal to natural coke and subsequent larger-scale regional metamorphism then metamorphosed the coal to semianthracite.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"290 ","pages":"Article 104548"},"PeriodicalIF":5.6,"publicationDate":"2024-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141408515","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 data reveal depositional and thermal history of coal in the Guaduas formation, Colombian Eastern Cordillera","authors":"L. Camacho-Aristizabal ,&nbsp;L. Burnaz ,&nbsp;L. Castro-Vera ,&nbsp;L. Mojica Silva ,&nbsp;R. Littke","doi":"10.1016/j.coal.2024.104549","DOIUrl":"10.1016/j.coal.2024.104549","url":null,"abstract":"<div><p>Colombia is a country rich in coal deposits; however, there are few published studies characterizing these coals in detail from a scientific perspective. This study investigates the thermal maturity and depositional environment of a coal seam from the Guaduas formation (Maastrichtian-Paleocene) of the Eastern Colombian Cordillera Basin, providing insight into burial and temperature history and changes in the depositional environment over time. This three-meter-thick hard coal seam reflects about 20 m of former peat deposition, representing a period of roughly 10.000 years.</p><p>Five large, fresh samples (A to E) were collected from the seam every thirty centimeters and divided into seventeen sub-samples analyzed using organic petrological methods, Rock-Eval pyrolysis and organic geochemistry. Different thermal maturity- and depositional environment-related parameters have been determined. Results reveal a maturity of approximately 0.9% vitrinite reflectance, and relatively high HI values (kerogen type II-III). Correspondingly, high values of νCHx over γCH indicate a high relative abundance of aromatic rings over aliphatic groups. Moreover, high CH₂/CH₃ ratios suggest long and simple aliphatic chain structures. Molecular data indicate a balanced odd- over even <em>n</em>-alkane distribution and a high amount of long-chain <em>n</em>-alkanes. High Pr/Ph ratios and hopanoid biomarkers reveal an oxidizing depositional environment. The coal seam investigated in this study is characterized by low ash yields and low sulfur contents particularly in the central part of the seam, while percentages of inertinite are high (up to 54 Vol.-%). This data supports a low water table and oligotrophic, raised bog conditions during deposition in a humid, tropical climate which is consistent with the almost equatorial position of the study area during deposition of the Guaduas Formation. Water was mainly supplied via rainfall leading to overall low ash yields. In contrast, the top of the coal seam is strongly enriched in sulfur revealing that rapid marine flooding ultimately ceased peat accumulation leading to authigenic pyrite formation.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"289 ","pages":"Article 104549"},"PeriodicalIF":5.6,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S016651622400106X/pdfft?md5=0678b51a064e43ac5115f21dfd3a7881&pid=1-s2.0-S016651622400106X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141391485","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":"Evaluation of coal mine drainage and associated precipitates for radium and rare earth element concentrations","authors":"Bonnie McDevitt ,&nbsp;Charles A. Cravotta III ,&nbsp;Ryan J. McAleer ,&nbsp;John C. Jackson ,&nbsp;Aaron M. Jubb ,&nbsp;Glenn D. Jolly ,&nbsp;Benjamin C. Hedin ,&nbsp;Nathaniel R. Warner","doi":"10.1016/j.coal.2024.104547","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104547","url":null,"abstract":"<div><p>Coal mine drainage (CMD) and associated metal-rich precipitates have recently been proposed as unconventional sources of rare earth elements (REEs). However, the potential occurrence of radium (Ra), a known carcinogen, with the REE-bearing phases has not been investigated. We hypothesized that Ra may occur in solids that are precipitated from CMD as a “radiobarite” solid solution ((Ba,Sr,Ra)SO₄) and/or adsorbed with hydrous metal oxides. REEs have been documented to sorb or co-precipitate with iron (Fe), manganese (Mn), and aluminum (Al) oxyhydroxide in CMD solids. Likewise, Ra has been documented to sorb to hydrous Fe and Mn oxides especially where sulfate (SO₄) and/or barium (Ba) concentrations are insufficient to precipitate radiobarite. Thus, we conducted the first-ever survey of Ra concentrations in corresponding CMD water and solid samples in the United States. Samples were analyzed from 4 untreated and 9 treated CMD sites in both the bituminous and anthracite coal regions of Pennsylvania across a range of pH and SO₄ concentrations. The dissolved Ra in CMD was relatively low (&lt;0.5 Bq/L), consistent with radiobarite solubility; however, CMD solids were largely composed of amorphous Fe, Al, and Mn oxyhydroxide and silicate minerals. Ra was associated with Mn-enriched CMD solids, upwards of 875 Bq/kg. Total REE + yttrium (Y) content in the CMD solids was enriched upwards of 3600 mg/kg and was significantly correlated with Al content. These preliminary results suggest that REE extraction may target Al-rich solids to avoid Ra in Mn-rich solids.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"289 ","pages":"Article 104547"},"PeriodicalIF":5.6,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224001046/pdfft?md5=67423a80d2c08b9416a3db6ead8d212b&pid=1-s2.0-S0166516224001046-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141324630","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":"Diagenesis and mineralization in the Central African Copperbelt, implications from the reflectance of pyrobitumen and Kübler (illite crystallinity) index","authors":"Qiuping Liu ,&nbsp;Pascal Mambwe ,&nbsp;Ralf Littke ,&nbsp;Philippe Muchez","doi":"10.1016/j.coal.2024.104534","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104534","url":null,"abstract":"<div><p>The Central African Copperbelt stands out as one of the world's largest sediment-hosted Cu-Co provinces, contributing to over 60% of global Co production. A comprehensive basin analysis approach is imperative for unraveling the ore-forming processes, encompassing an understanding of the diagenesis or metamorphism that the mineralized rocks underwent. In this study, two types of pyrobitumen (burial related and burial plus hydrothermal related) reflectance values have been measured, which record maximum temperatures during deep burial and hydrothermal imprint. The calculated temperatures provide important information about the maximum burial and hydrothermal fluid temperatures in distinct regions of the Copperbelt. The average burial related pyrobitumen reflectance for Nkana, the southeastern part of the Copperbelt, ranges between 3.43 and 3.75% BR_r, indicating a maximum burial temperature of about 240 °C. Moving towards the central part of the Copperbelt at Luiswishi, the average pyrobitumen reflectance varies between 2.65 and 2.87% BR_r, with calculated maximum burial temperatures reaching about 220 °C. In the northwestern part (Tenke Fungurume mining district, TFMD), the maximum burial temperatures decrease to approximately 200 °C, based on the calculation of pyrobitumen reflectance at 2.10% BR_r. This decreasing temperature trend from southeast to northwest corresponds to the observed decrease in metamorphic grade across the Copperbelt, ranging from amphibolite and upper greenschist facies in the Zambian part to prehnite-pumpellyite facies in the Congolese Copperbelt. The temperatures calculated during maximum burial, especially at the Nkana ore deposit, are lower than those previously proposed based on the mineralogy of the rocks, i.e. upper greenschist facies. However, the latter does correspond to the temperatures reached by the mineralizing fluids in this area and thus rather reflects the alteration assemblage and temperature. The average burial plus hydrothermal related pyrobitumen reflectance measured at TFMD ranges between 3.06 and 5.36% BR_r, indicating calculated average temperatures of 300–350 °C. These temperatures align with those recorded for the late diagenetic to syn-orogenic mineralization by fluid inclusion microthermometry (180–340 °C) at TFMD. The data suggests a pervasive migration of hydrothermal fluid through the rocks, contributing to the observed pyrobitumen reflectance. The illite crystallinity of the examined samples is notably high. At Nkana, the KI values range between 0.10 Δ°2θ and 0.22 Δ°2θ, for Luiswishi between 0.12 Δ°2θ and 0.24 Δ°2θ, for Kamoto between 0.17 Δ°2θ and 0.23 Δ°2θ, for TFMD between 0.17 Δ°2θ and 0.25 Δ°2θ, which indicates all these samples were placed in epizone, with only a few in anchizone. This high value could be attributed to two potential factors: the admixing of detrital muscovite to the sediments or the influx of potassium due to the pervasive","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"289 ","pages":"Article 104534"},"PeriodicalIF":5.6,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141303307","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 the burial history and the hydrocarbon potential of the late Paleozoic Claromecó foreland Basin (Southwestern Gondwana, Argentina) by combining organic geochemistry, organic petrology, and thermal modeling","authors":"María Belén Febbo ,&nbsp;Silvia Omodeo-Salé ,&nbsp;Andrea Moscariello","doi":"10.1016/j.coal.2024.104546","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104546","url":null,"abstract":"<div><p>The Claromecó foreland Basin (Carboniferous–Permian; southern Buenos Aires province, Argentina) is key to understanding the paleotectonic evolution of the southwestern Gondwana margin and is relevant to energy resource exploration. This study reconstructs the thermal and burial history of the Claromecó Basin by integrating geochemical data, organic petrology, and thermal modeling techniques. Cores samples of the Tunas Formation (Pillahuincó Group, Early Permian) were studied. A 1D thermal model was constructed, calibrated with vitrinite reflectance measurements (VRo %), and corroborated with fluid inclusion and apatite fission track data from previous studies. Rock-Eval pyrolysis results show TOC% values ranging from 0.13 to 60.35 wt%. The Hydrogen index (HI &lt; 50 mg HC/g TOC) and Oxygen index (OI &lt; 50 mg CO₂/g TOC) indicate the dominance of Type III and Type IV kerogens, most likely resulting from the thermal maturation of an original Type III kerogen. Petrologic observations confirm the presence of macerals from the inertinite group, as well as minor amounts of vitrinite and liptinite. The Tmax displays a temperature range mostly from 460 to 610 °C. The VRo % values range from 1.5 to 2.0%. Geochemical data combined with VRo % measurements confirm a late catagenesis to metagenesis stage within the wet to dry gas window for coals and organic-rich strata.</p><p>In order to constrain the thermal evolution of the basin infill, different scenarios were tested by varying the heat flow and the missing section thickness associated with the uplift and erosion of the basin (Permian–Cenozoic unconformity). The best calibration results were obtained with an erosion thickness of 3000 up to 4200 m and paleo heat flow peaks of either 60 or 80 mW/m² during the Lower Permian–Lower Cretaceous. The Tunas Formation was deposited and buried during the Permian–Triassic (Gondwanides Orogeny phase), reaching a maximum temperature of 180 °C. The results obtained by combining geochemical analysis, organic petrology, and thermal modeling techniques indicate that the coal beds of the Tunas Formation could have a current potential as gas-prone source rocks. Despite that, the hydrocarbon generation capacity of coal levels is currently low due to the high percentage of residual (Type IV) kerogen. Further research could help clarify if the hydrocarbons potentially expelled by these source rocks have been lost due to migration or could be trapped somewhere in the basin.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"289 ","pages":"Article 104546"},"PeriodicalIF":5.6,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141302474","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 geochemistry of rare metal (Zr-Nb-Hf-Ta-REE-Ga) coals of the seam XXX of the Izykh Coalfield, Minusinsk Basin, Russia: Implications for more widespread rare metal mineralization in North Asia","authors":"A.V. Vergunov ,&nbsp;S.I. Arbuzov ,&nbsp;D.A. Spears ,&nbsp;A.S. Kholodov ,&nbsp;S.S. Ilenok","doi":"10.1016/j.coal.2024.104542","DOIUrl":"10.1016/j.coal.2024.104542","url":null,"abstract":"<div><p>This study focuses a comprehensive mineralogical and geochemical study of rare-metal (Zr-Nb-Hf-Ta-REE-Ga) mineralization in the Permian coal seam XXX-XXXa of the Izykh Coalfield, Minusinsk Basin, southern Siberia. A link is demonstrated between the accumulation of rare metals in the coal with a volcanogenic rock parting up to 45 cm thick separating the coal seams. The floor of seam XXX is also characterized by the presence of pyroclastic material, which affects the level of accumulation of rare elements in the coal of the seam. Coals and intra-seam rock partings in seam XXX-XXXa have abnormally high concentrations of Zr, Nb, Hf, Ta, REE and Ga. In coal ash samples, the contents of some elements are highly evaluated, e.g., 1.4% Zr, 0.26% Nb, 164 ppm Hf, 17.9 ppm Ta, 0.8% REE, 0.13% Y, and 226 ppm Ga. The concentration of rare elements is higher in the coal and coal ash of the XXX coal seam than in the XXXa coal seam. The accumulation of anomalous concentrations of Zr-Nb-Hf-Ta-REE and Ga is mostly specific for the rock parting between the XXX and XXXa seams, as well as for the coals in contact with this parting. Zirconium, Nb, Y, and REE form more contrasting halos near the parting compared to Ta, Hf, and Ga. This is explained by the different mobility of the elements under weathering and diagenetic conditions. Other ore elements are concentrated to a greater extent in the coal in the near-contact zone, as well as at a distance from the partings. Ore material is concentrated primarily in the fine-dispersed mineral phase represented mainly by Zr-Nb-Ti-Fe oxides, complex Nb-Zr-P silicates, and REY-bearing phosphates (monazite, xenotime). Volcanogenic pyroclastics of acidic and alkaline composition (rhyolite-pantellerite) influenced the accumulation of rare metals in coal. Volcanic ash, transported from a distant source, served as the raw material for the formation of the rock interlayer in coal. The composition of this volcanic ash is believed to correspond to a pantelleritic tuff. These findings are comparable to those reached in earlier work on the altered ash in the coal seam XI of the Kuznetsk Coal Basin, which has similar geochemical features and is also of Permian age. Complex Zr-Nb-Hf-Ta-REE-Ga mineralization in the coals of the Kuznetsk and Minusinsk basins, associated with volcanogenic pyroclastics, indicates a wide manifestation of active acid and alkaline volcanism during the formation of coal deposits and the possibility of identifying similar mineralization in Permian coals of East and North Asia.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"289 ","pages":"Article 104542"},"PeriodicalIF":5.6,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141281203","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}