Pub Date : 2024-06-15DOI: 10.1016/j.coal.2024.104550
Vivek Kumar , Dibyendu Paul , Sudhir Kumar
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.
硫稳定同位素特征有助于追溯硫的来源并追踪硫在不同环境区划中的移动,此外还能提供有关硫的来源和迁移动态的重要见解。煤中的硫稳定同位素组成可以提供有关硫来源和煤中硫掺入过程的宝贵信息。本研究的目的是测定印度东北部煤矿和一些煤层样本中渐新世和始新世煤炭样本中的总硫含量和块状硫(bulk S δ34S)的硫同位素组成。结果显示,煤样中的全硫含量在 1.03 至 4.80(重量百分比)之间变化,平均值为 2.64(重量百分比)。煤样中的大量 S δ34S 在 -4.66 ‰ 至 14.78 ‰(VCDT)之间变化很大。阿鲁纳恰尔邦、阿萨姆邦和那加兰邦煤矿的渐新世煤炭样品与梅加拉亚邦詹蒂亚山地区的始新世煤炭样品相比,富含更重的硫同位素。在渐新世煤炭样本中观察到了中等程度的正相关,而在始新世煤炭样本中则发现了中等程度的负相关。煤炭样品中的大量 S δ34S 值和硫含量与阿萨姆邦和梅加拉亚邦的煤矿样品非常吻合。这项研究的结果可用于追踪煤炭硫磺在不同环境区划中的来源和移动,此外还提供了有关硫磺来源、煤炭中硫磺掺入过程和沉积环境的宝贵信息。
{"title":"Sulfur stable isotopes in Paleogene coals of Northeast India","authors":"Vivek Kumar , Dibyendu Paul , 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 δ<sup>34</sup>S) 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 δ<sup>34</sup>S 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 δ<sup>34</sup>S 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":null,"pages":null},"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}
Pub Date : 2024-06-15DOI: 10.1016/j.coal.2024.104548
Na Wang , Joan S. Esterle , Sandra Rodrigues , James C. Hower , Shifeng Dai
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 (Rr) 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 > 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% Rr) 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.
火成岩侵入会引起煤炭和矿物的改变。蚀变程度取决于原位煤的等级和宏观矿物组成、侵入温度、热源远近和侵入体大小。在二叠纪峰峰煤田,煤炭等级从高挥发烟煤到无烟煤,由南向北递增约 50 公里。煤层普遍被侵入,侏罗纪-白垩纪火成岩侵入体加剧了区域等级的提升,而不仅仅是埋藏煤化。对峰峰煤田北部大树村煤矿的半无烟煤进行的岩相检查显示,焦炭微观结构有所发展,2 号煤层中接近堤坝的反射率增加。根据 11 个水平间隔为 50 厘米的样本,随机玻璃光泽反射率值(Rr)从接触面处的 5.41% 下降到距离接触面 5 米处的背景值 2.05%。向堤坝方向,矾土各向异性增加,微纹理显示出圆形、粗镶嵌、带状各向异性焦炭纹理和脱溶空泡的发展。天然焦炭纹理与侵入体/煤接触处的估计温度 > 570 °C 相符。然而,半无烟煤中出现的焦炭结构揭示了局部和区域的热演化。焦炭纹理表明,侵入时煤炭等级为高挥发性 A 级烟煤。这对埋藏历史、加热和沉降速度都有影响。假设古地热梯度为 40 °C/km,那么在侏罗纪侵入时,高挥发性 A 烟煤(1% Rr)将被埋藏 3 km。入侵将高挥发性烟煤变质为天然焦炭,随后更大规模的区域变质作用又将煤变质为半无烟煤。
{"title":"Insights on the regional thermal evolution from semianthracite petrology of the Fengfeng coalfield, China","authors":"Na Wang , Joan S. Esterle , Sandra Rodrigues , James C. Hower , 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<sub>r</sub>) 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 > 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<sub>r</sub>) 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":null,"pages":null},"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}
Pub Date : 2024-06-14DOI: 10.1016/j.coal.2024.104549
L. Camacho-Aristizabal , L. Burnaz , L. Castro-Vera , L. Mojica Silva , R. Littke
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.
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 n-alkane distribution and a high amount of long-chain n-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.
{"title":"Organic petrology and geochemistry data reveal depositional and thermal history of coal in the Guaduas formation, Colombian Eastern Cordillera","authors":"L. Camacho-Aristizabal , L. Burnaz , L. Castro-Vera , L. Mojica Silva , 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 CH<sub>2</sub>/CH<sub>3</sub> 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":null,"pages":null},"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}
Pub Date : 2024-06-10DOI: 10.1016/j.coal.2024.104547
Bonnie McDevitt , Charles A. Cravotta III , Ryan J. McAleer , John C. Jackson , Aaron M. Jubb , Glenn D. Jolly , Benjamin C. Hedin , Nathaniel R. Warner
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 (<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.
{"title":"Evaluation of coal mine drainage and associated precipitates for radium and rare earth element concentrations","authors":"Bonnie McDevitt , Charles A. Cravotta III , Ryan J. McAleer , John C. Jackson , Aaron M. Jubb , Glenn D. Jolly , Benjamin C. Hedin , 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)SO<sub>4</sub>) 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 (SO<sub>4</sub>) 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 SO<sub>4</sub> concentrations. The dissolved Ra in CMD was relatively low (<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":null,"pages":null},"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}
Pub Date : 2024-06-06DOI: 10.1016/j.coal.2024.104534
Qiuping Liu , Pascal Mambwe , Ralf Littke , Philippe Muchez
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% BRr, 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% BRr, 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% BRr. 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% BRr, 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
{"title":"Diagenesis and mineralization in the Central African Copperbelt, implications from the reflectance of pyrobitumen and Kübler (illite crystallinity) index","authors":"Qiuping Liu , Pascal Mambwe , Ralf Littke , 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<sub>r</sub>, 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<sub>r</sub>, 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<sub>r</sub>. 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<sub>r</sub>, 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":null,"pages":null},"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}
Pub Date : 2024-06-06DOI: 10.1016/j.coal.2024.104546
María Belén Febbo , Silvia Omodeo-Salé , Andrea Moscariello
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 < 50 mg HC/g TOC) and Oxygen index (OI < 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.
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.
{"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 , Silvia Omodeo-Salé , 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 < 50 mg HC/g TOC) and Oxygen index (OI < 50 mg CO<sub>2</sub>/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/m<sup>2</sup> 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":null,"pages":null},"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}
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.
{"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 , S.I. Arbuzov , D.A. Spears , A.S. Kholodov , 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":null,"pages":null},"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}
Pub Date : 2024-06-03DOI: 10.1016/j.coal.2024.104545
Riza Nurbekova , Xiangyun Shi , Randy Hazlett , David Misch , Milovan Fustic , Reinhard F. Sachsenhofer
Extensive nanoindentation testing over a range of deflection depths of up to 4 μm yielded a large dataset, providing a viable framework for the statistical assessment of the mechanical properties, specifically elastic modulus (E) and hardness (H), of compositionally diverse organic-rich mudstone samples. The data from indentations as shallow as 300–400 nm were clustered using the k-means algorithm to identify three mechanical categories in the samples: a soft pseudophase (e.g., organic matter, gypsum, and clay minerals), a stiff pseudophase (e.g., quartz and feldspar), and a transitional composite-like pseudophase bridging the soft and hard minerals. The initially diverse values of E and H for the mechanical pseudophases were observed to converge to a constant value at indentations beyond 2–2.5 μm (varying between different samples), implying the existence of a minimal probing depth for assessing the bulk E and H of heterogeneous mudstone samples. The obtained bulk E and H values (8–21 GPa and 0.3–0.9 GPa, respectively) demonstrated a strong correlation with the mineralogical composition of the indented samples. Despite containing a notable proportion of mechanically stiff components (>45 vol%), the bulk mechanical parameters determined in this study were significantly lower than those reported for major shale formations such as the Barnett and Longmaxi Shale. This discrepancy is primarily due to the presence of organic matter with low thermal maturity (Ro < 0.6%), which constitutes <36 vol% of the samples, and a significant gypsum content, accounting for <15 vol%.
The employed approach not only demonstrated the importance of choosing the proper indentation depths for investigating the mechanical properties of highly heterogeneous mudstone rocks and their constituent minerals, but it also illustrated the capability of examining various volumes of investigation using nanoindentation, approaching macroscopic values, and identifying a representative element volume (REV). The findings also provided crucial insights into the fracability and overall producibility of the investigated formations, thereby enhancing our understanding of their extraction potential.
在高达 4 μm 的挠曲深度范围内进行的广泛纳米压痕测试产生了一个大型数据集,为富含有机物的不同成分泥岩样品的力学性能(特别是弹性模量(E)和硬度(H))的统计评估提供了一个可行的框架。使用 K-means 算法对浅至 300-400 nm 的压痕数据进行聚类,以确定样品中的三个力学类别:软假相(如有机物、石膏和粘土矿物)、硬假相(如石英和长石)以及连接软硬矿物的过渡复合假相。据观察,机械假相最初不同的 E 值和 H 值在压痕超过 2-2.5 μm 时趋于一个恒定值(不同样品之间存在差异),这意味着存在一个最小探测深度来评估异质泥岩样品的体积 E 值和 H 值。所获得的体积 E 值和 H 值(分别为 8-21 GPa 和 0.3-0.9 GPa)与压痕样品的矿物成分密切相关。尽管含有相当比例的机械刚性成分(45% vol%),但本研究确定的块体机械参数明显低于巴尼特页岩和龙马溪页岩等主要页岩层的报告参数。造成这种差异的主要原因是样本中存在热成熟度较低的有机物(Ro < 0.6%),占样本总量的 36%,以及大量石膏(占样本总量的 15%)。所采用的方法不仅证明了选择适当的压痕深度对研究高度异质泥岩及其组成矿物的机械特性的重要性,而且还说明了使用纳米压痕法检测各种调查体积、接近宏观值和确定代表性元素体积(REV)的能力。研究结果还对所调查地层的可压裂性和总体可开采性提供了重要见解,从而加深了我们对其开采潜力的了解。
{"title":"Geomechanical characterization and mineralogical correlation of compositionally diverse world-class Kazakhstani source rocks: Insights from nanoindentation testing","authors":"Riza Nurbekova , Xiangyun Shi , Randy Hazlett , David Misch , Milovan Fustic , Reinhard F. Sachsenhofer","doi":"10.1016/j.coal.2024.104545","DOIUrl":"10.1016/j.coal.2024.104545","url":null,"abstract":"<div><p>Extensive nanoindentation testing over a range of deflection depths of up to 4 μm yielded a large dataset, providing a viable framework for the statistical assessment of the mechanical properties, specifically elastic modulus (<em>E</em>) and hardness (<em>H</em>), of compositionally diverse organic-rich mudstone samples. The data from indentations as shallow as 300–400 nm were clustered using the <em>k</em>-means algorithm to identify three mechanical categories in the samples: a soft pseudophase (e.g., organic matter, gypsum, and clay minerals), a stiff pseudophase (e.g., quartz and feldspar), and a transitional composite-like pseudophase bridging the soft and hard minerals. The initially diverse values of <em>E</em> and <em>H</em> for the mechanical pseudophases were observed to converge to a constant value at indentations beyond 2–2.5 μm (varying between different samples), implying the existence of a minimal probing depth for assessing the bulk <em>E</em> and <em>H</em> of heterogeneous mudstone samples. The obtained bulk <em>E</em> and <em>H</em> values (8–21 GPa and 0.3–0.9 GPa, respectively) demonstrated a strong correlation with the mineralogical composition of the indented samples. Despite containing a notable proportion of mechanically stiff components (>45 vol%), the bulk mechanical parameters determined in this study were significantly lower than those reported for major shale formations such as the Barnett and Longmaxi Shale. This discrepancy is primarily due to the presence of organic matter with low thermal maturity (R<sub>o</sub> < 0.6%), which constitutes <36 vol% of the samples, and a significant gypsum content, accounting for <15 vol%.</p><p>The employed approach not only demonstrated the importance of choosing the proper indentation depths for investigating the mechanical properties of highly heterogeneous mudstone rocks and their constituent minerals, but it also illustrated the capability of examining various volumes of investigation using nanoindentation, approaching macroscopic values, and identifying a representative element volume (REV). The findings also provided crucial insights into the fracability and overall producibility of the investigated formations, thereby enhancing our understanding of their extraction potential.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141277094","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}
Pub Date : 2024-05-31DOI: 10.1016/j.coal.2024.104535
J.K. Pearce , H. Hofmann , K. Baublys , D.I. Cendón , S.D. Golding , S.J. Herbert , Z. Bhebhe , A. Nguyen , P. Hayes
Understanding inter-aquifer connectivity or leakage of greenhouse gases and groundwater to aquifers overlying gas reservoirs is important for environmental protection and social licence to operate. Australia's Great Artesian Basin (GAB) is the largest artesian groundwater system in the world with groundwater extracted for agriculture, livestock, mines, energy, private or town water supply. Microbial coal seam gas (CSG) and production water are also extracted from the GAB. Here a range of groundwater tracers is used to investigate the potential for gas and groundwater connectivity between the CSG reservoir and aquifers.
The GAB aquifer and alluvium contained a range of methane concentrations (0.001 to 2100 mg/L) that exhibit an increase with depth and δ13C-CH4. Aquifer and alluvium groundwater 87Sr/86Sr were in the range 0.7042 to 0.7082. CSG production waters however had non-radiogenic, distinctive 87Sr/86Sr signatures <0.7036, indicating a lack of significant groundwater leakage. One gassy aquifer bore with 160 mg/L methane conversely has 87Sr/86Sr, δ13C-CH4, δ2H-CH4 and δ13C-DIC values overlapping the CSG waters. In several aquifers δ34S-SO4 and δ18O-SO4 are sourced from windblown surface salts of inland Australian playa lakes in recharge waters. Bacterial sulphate reduction is additionally occurring in a regional aquifer. Cosmogenic isotopes and tritium show recent recharge and mixing with older groundwaters in several shallow aquifers.
Groundwater and gas signatures indicate that leakage of groundwater and methane from the CSG reservoir was not occurring in the majority of areas investigated here. Methane was consistent with in situ generation in shallow GAB aquifers by primary microbial CO2 reduction or acetate fermentation. Connectivity of one alluvial bore and the underlying GAB aquifer could not be completely ruled out. Separately, one gassy Springbok GAB aquifer bore is either connected to the underlying CSG gas reservoir, or has in situ secondary microbial CO2 reduction producing methane from interbedded coal within the aquifer. This study is relevant to other basins in Australia and internationally where gas is observed in aquifers that overly conventional, unconventional or coal seam gas reservoirs.
{"title":"Geochemical tracers associated with methane in aquifers overlying a coal seam gas reservoir","authors":"J.K. Pearce , H. Hofmann , K. Baublys , D.I. Cendón , S.D. Golding , S.J. Herbert , Z. Bhebhe , A. Nguyen , P. Hayes","doi":"10.1016/j.coal.2024.104535","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104535","url":null,"abstract":"<div><p>Understanding inter-aquifer connectivity or leakage of greenhouse gases and groundwater to aquifers overlying gas reservoirs is important for environmental protection and social licence to operate. Australia's Great Artesian Basin (GAB) is the largest artesian groundwater system in the world with groundwater extracted for agriculture, livestock, mines, energy, private or town water supply. Microbial coal seam gas (CSG) and production water are also extracted from the GAB. Here a range of groundwater tracers is used to investigate the potential for gas and groundwater connectivity between the CSG reservoir and aquifers.</p><p>The GAB aquifer and alluvium contained a range of methane concentrations (0.001 to 2100 mg/L) that exhibit an increase with depth and δ<sup>13</sup>C-CH<sub>4</sub>. Aquifer and alluvium groundwater <sup>87</sup>Sr/<sup>86</sup>Sr were in the range 0.7042 to 0.7082. CSG production waters however had non-radiogenic, distinctive <sup>87</sup>Sr/<sup>86</sup>Sr signatures <0.7036, indicating a lack of significant groundwater leakage. One gassy aquifer bore with 160 mg/L methane conversely has <sup>87</sup>Sr/<sup>86</sup>Sr, δ<sup>13</sup>C-CH<sub>4</sub>, δ<sup>2</sup>H-CH<sub>4</sub> and δ<sup>13</sup>C-DIC values overlapping the CSG waters. In several aquifers δ<sup>34</sup>S-SO<sub>4</sub> and δ<sup>18</sup>O-SO<sub>4</sub> are sourced from windblown surface salts of inland Australian playa lakes in recharge waters. Bacterial sulphate reduction is additionally occurring in a regional aquifer. Cosmogenic isotopes and tritium show recent recharge and mixing with older groundwaters in several shallow aquifers.</p><p>Groundwater and gas signatures indicate that leakage of groundwater and methane from the CSG reservoir was not occurring in the majority of areas investigated here. Methane was consistent with in situ generation in shallow GAB aquifers by primary microbial CO<sub>2</sub> reduction or acetate fermentation. Connectivity of one alluvial bore and the underlying GAB aquifer could not be completely ruled out. Separately, one gassy Springbok GAB aquifer bore is either connected to the underlying CSG gas reservoir, or has in situ secondary microbial CO<sub>2</sub> reduction producing methane from interbedded coal within the aquifer. This study is relevant to other basins in Australia and internationally where gas is observed in aquifers that overly conventional, unconventional or coal seam gas reservoirs.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000922/pdfft?md5=79a21be44647689570498e729acffea5&pid=1-s2.0-S0166516224000922-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141290912","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}
Pub Date : 2024-05-28DOI: 10.1016/j.coal.2024.104533
Ahmed Mansour , Thomas Gentzis , Timothy O. Nesheim , Jian Wang , Xiugen Fu , Mohamed S. Ahmed , Humberto Carvajal-Ortiz
The Carboniferous was a period of intense environmental perturbations, climate changes between greenhouse and icehouse, eustatic sea level change, and accumulation of organic carbon-rich sediments. At this time, the Tyler Formation was deposited in the midcontinent USA. A detailed palynological analysis of the Tyler Formation revealed a highly diverse assemblage of spores with minor pollen content, represented by 100 species belonging to 51 genera. Stratigraphically constrained spores and pollen grains were used to construct three interval zones of middle-late Chesterian (late Viséan-Serpukhovian) to early Morrowan (middle Bashkirian) ages. The stratigraphic position of the Mississippian-Pennsylvanian boundary was determined in the lower Tyler Formation based on the last appearance of typical forms of the late Chesterian, including Tripartites vetustus, Knoxisporites triradiatus, Knoxisporites stephanephorus, Densosporites diatretus, and Schopfipollenites acadiensis, compared to the first appearance of early Morrowan Crassispora kosankei, Cirratriradites saturnii, Radiizonates aligerens, and Raistrickia saetosa. Palynofacies analysis and statistical clustering of the Tyler Formation showed three palynofacies assemblages. PFA-1 showed moderate relative abundances of phytoclasts and AOM, suggesting deposition close to fluvio-deltaic and shallow marine environments, while PFA-2 exhibited high abundances of phytoclasts, mostly of opaque wood, reflecting deposition in active river-dominated delta plains. PFA-3 showed the highest abundances of AOM, suggesting deposition in a shallow marine environment. Organic petrography and geochemistry data indicate that the Tyler Formation is one of the best source rock intervals throughout the midcontinent USA. Based on organic matter richness, the Tyler Formation is subdivided into three groups. The first group has TOC contents higher than 10 wt% of kerogen Types III, mixed II/III, and II with excellent hydrocarbon generation potential. The second group has TOC content in the range of 2–10 wt% of kerogen Types III, mixed II/III, and II, and fair to excellent hydrocarbon generation potential. The third group shows organic matter richness with TOC content below 2 wt% with good organic matter richness and kerogen Types III to IV, and poor to fair hydrocarbon generation potential. The organic matter thermal maturity is evaluated based on Tmax and VRo% values, suggesting that all samples of Tyler Formation are in the early to late stages of the oil window. However, care should be considered when assessing a mature source rock because the kerogen typing and generation is based on present-day TOC, S2, and HI rather than their original values.
石炭纪是一个环境剧烈扰动的时期,气候在温室和冰室之间变化,海平面发生震荡性变化,富含有机碳的沉积物不断积累。此时,泰勒地层沉积于美国中部大陆。对泰勒地层进行的详细古生物学分析表明,这里的孢子种类繁多,花粉含量较少,共有 51 个属 100 个种。根据地层制约的孢子和花粉粒,构建了从切斯特期中晚期(Viséan-Serpukhovian 晚期)到莫罗期早期(Bashkirian 中期)的三个区间带。根据晚期切斯特期典型形态的最后出现时间,包括、、、和,与早期摩罗期的首次出现时间、、、和,确定了密西西比期-彭斯瓦尼期界线在泰勒地层下部的地层位置。泰勒地层的古生界分析和统计聚类显示出三种古生界组合。PFA-1显示出中等相对丰度的植物蜕皮器和AOM,表明沉积在靠近氟三角洲和浅海环境的地方;PFA-2显示出较高丰度的植物蜕皮器,主要为不透明木质,反映出沉积在以河流为主的活跃三角洲平原。PFA-3 显示出最高的 AOM 丰度,表明沉积在浅海环境中。有机岩石学和地球化学数据表明,泰勒地层是整个美国中部大陆最好的源岩层段之一。根据有机质的丰富程度,泰勒地层被细分为三组。第一组的总有机碳(TOC)含量高于 10 wt%,属于角质三类、混合二/三类和二类,具有极佳的碳氢化合物生成潜力。第二组的 TOC 含量在 2-10 wt%之间,包括 III 型角质、II/III 混合型和 II 型角质,碳氢化合物生成潜力从一般到优秀。第三组显示有机质丰富度,TOC 含量低于 2 wt%,有机质丰富度较好,角质类型 III 至 IV,碳氢化合物生成潜力较差至一般。根据 T 和 VRo%值评估有机质热成熟度,表明泰勒地层的所有样本都处于石油窗口的早期至晚期阶段。不过,在评估成熟源岩时应注意,因为角质层的分类和生成是基于目前的 TOC、S 和 HI 值,而不是其原始值。
{"title":"Palynostratigraphy of the Mississippian-Pennsylvanian boundary in the Tyler Formation, Williston Basin, USA: Implications for organic matter-rich source rocks and paleoenvironmental reconstruction","authors":"Ahmed Mansour , Thomas Gentzis , Timothy O. Nesheim , Jian Wang , Xiugen Fu , Mohamed S. Ahmed , Humberto Carvajal-Ortiz","doi":"10.1016/j.coal.2024.104533","DOIUrl":"10.1016/j.coal.2024.104533","url":null,"abstract":"<div><p>The Carboniferous was a period of intense environmental perturbations, climate changes between greenhouse and icehouse, eustatic sea level change, and accumulation of organic carbon-rich sediments. At this time, the Tyler Formation was deposited in the midcontinent USA. A detailed palynological analysis of the Tyler Formation revealed a highly diverse assemblage of spores with minor pollen content, represented by 100 species belonging to 51 genera. Stratigraphically constrained spores and pollen grains were used to construct three interval zones of middle-late Chesterian (late Viséan-Serpukhovian) to early Morrowan (middle Bashkirian) ages. The stratigraphic position of the Mississippian-Pennsylvanian boundary was determined in the lower Tyler Formation based on the last appearance of typical forms of the late Chesterian, including <em>Tripartites vetustus</em>, <em>Knoxisporites triradiatus</em>, <em>Knoxisporites stephanephorus</em>, <em>Densosporites diatretus</em>, and <em>Schopfipollenites acadiensis</em>, compared to the first appearance of early Morrowan <em>Crassispora kosankei</em>, <em>Cirratriradites saturnii</em>, <em>Radiizonates aligerens</em>, and <em>Raistrickia saetosa</em>. Palynofacies analysis and statistical clustering of the Tyler Formation showed three palynofacies assemblages. PFA-1 showed moderate relative abundances of phytoclasts and AOM, suggesting deposition close to fluvio-deltaic and shallow marine environments, while PFA-2 exhibited high abundances of phytoclasts, mostly of opaque wood, reflecting deposition in active river-dominated delta plains. PFA-3 showed the highest abundances of AOM, suggesting deposition in a shallow marine environment. Organic petrography and geochemistry data indicate that the Tyler Formation is one of the best source rock intervals throughout the midcontinent USA. Based on organic matter richness, the Tyler Formation is subdivided into three groups. The first group has TOC contents higher than 10 wt% of kerogen Types III, mixed II/III, and II with excellent hydrocarbon generation potential. The second group has TOC content in the range of 2–10 wt% of kerogen Types III, mixed II/III, and II, and fair to excellent hydrocarbon generation potential. The third group shows organic matter richness with TOC content below 2 wt% with good organic matter richness and kerogen Types III to IV, and poor to fair hydrocarbon generation potential. The organic matter thermal maturity is evaluated based on T<sub>max</sub> and VRo% values, suggesting that all samples of Tyler Formation are in the early to late stages of the oil window. However, care should be considered when assessing a mature source rock because the kerogen typing and generation is based on present-day TOC, S<sub>2</sub>, and HI rather than their original values.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141187741","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}