Occurrence and genetic mechanism of pyrite in the No. 9 coal seam in magmatic erosion area of the Handan coalfield

The No. 9 coal of Yunjialing Coal Mine in Handan Coalfield, which is subject to obvious magmatic intrusion, is taken as the research object. Optical microscope observation, electron probe energy spectrometry (EPMA-EDS), X-ray diffractometer (XRD), X-ray fluorescence spectrometry (XRF) and other analytical tests were used to analyze the enrichment characteristics of whole sulfur, sulfur forms and minerals, to study the occurrence of sulfur and pyrite in the coals, and to explore the sources of different types of pyrite. The results show that the No. 9 coal of Yunjialing Coal Mine in Handan Coalfield is a high-sulfur coal (0.61%～7.12%), sulfide sulfur is the main form of sulfur in the coal (1.18%～4.90%), followed by organic sulfur (0.56%～2.16%) with a little sulphate sulfur (0.01%～0.06%). The No. 9 coal of Yunhailing coal mine was deposited in the transitional environment of sea and land phases, and seawater intrusion provided abundant sulfur source for the No. 9 coal seam, the gas-liquid materials brought about by neutral magmatism during the Yanshan period elevate the total sulfur content in the No. 9 coal of the Yunjialing Caol Mine, especially the total sulfur content of the upper coal plies are significantly higher than the total sulfur content of the whole coal seam. The microscopic occurrence of pyrite in the No. 9 coal mainly includes massive pyrite, disseminated pyrite and fissure-filled pyrite, and is characterized by multi-stage evolution. Massive pyrite is mainly formed in the early diagenetic stage, the high temperature and gas-liquid materials brought about by neutral magmatism during the Yanshan period modified the morphology of pyrite in the coal, resulting in the activation and recrystallization of pyrite in the coal into a massive fraction. Inorganic sulfur from the high-temperature-affected portion of the pyrite diffused into the surrounding coal body and sequestered as organic sulfur, increasing the organic sulfur content of the upper coal plies

Geochemical characteristics of rare earth elements in Late Permian coals in Western Henan and indicative meaning

With the wide application of rare earth metals in high-tech fields such as medical treatment and new materials, its strategic position has been increasing. As a major country in rare earth, China supplies rare earth products of different varieties and grades to all countries in the world, making great contributions to the development of emerging industries in the world .In order to explore the enrichment degree, occurrence state and sedimentary environment of rare earth elements in late Permian coal in western Henan, 20 stratified coal samples from No.21 coal in Huixiang mining area in western Henan were taken as the main research object. The rare earth elements and major elements in stratified coal samples were measured by ICP-MS and XRF, and the content characteristics and enrichment degree of rare earth elements in coal samples were discussed. The occurrence state and sedimentary environment of rare earth elements in samples were discussed by correlation analysis and characteristic parameters .The results show that the mass concentration of REY is 35.29-133.61 μg/g, and the average concentration is 79.14 μg/g, which is slightly higher than the average concentration of REY in the world coal, but obviously lower than the average concentration of REY in China coal. The REY content is low, and LREY is mainly enriched. There is a significant positive correlation between REY and ash content (Ad), SiO2, Al2O3 and other major oxides in the No.21 coal of Huixiang mining area, indicating that REY mainly occurs in clay minerals .The negative anomalies of Ce and Eu elements and slight positive anomalies of (Gd/Gd)N* in the samples in the study area indicate that the study area is mainly affected by terrigenous sources and the coal forming environment is a weakly acidic reducing environment

Mineralogical Characteristics of Early Permian Paragonite-Bearing Coal (No. 3) in the Jinyuan Mine, Tengxian Coalfield, Shandong Province, Eastern China

The Early Permian coal is of great value in the Tengxian Coalfield, Shandon Province, Eastern China. This work deals with the new data focusing on mineralogical characteristics in the Early Permian Shanxi Formation No. 3 coal from the Jinyuan Mine. The Jinyuan coal is a low ash and highly volatile A bituminous coal. Minerals in the No. 3 coal mainly comprise of kaolinite, ankerite, illite, calcite, siderite, and quartz, with varying compositions of trace amounts of pyrite, jarosite, bassanite, anatase, and rutile. According to mineral assemblage in the coal plies, three Types (A to C) can be identified in the No. 3 coal. The dominant minerals in Type A are poorly-ordered kaolinite, illite, quartz, pyrite, and jarosite. Type B is mainly composed of well-ordered kaolinite, illite, siderite, ankerite, and calcite. Type C, with just one sample (JY-3-7c), which contains high proportions of calcite (54%) and ankerite (34%). Terrigenous minerals are elevated in coal plies that typically have relatively high contents of ash yield. The formation of syngenetic pyrite was generally due to seawater, while the sulphate minerals (jarosite and coquimbite) were derived from the oxidation of pyrite. Epigenetic vein-like or fracture-fillings carbonate minerals (ankerite, calcite, and siderite), kaolinite, and pyrite, as well as authigenic quartz were derived from the influx of hydrothermal fluids during different periods, from the authigenic to epigenetic. The paragonite in the coal may have been formed by the precipitated from Na-rich hydrothermal fluids. No effects of magmatic intrusion on mineralogy were investigated in this research

Mineralogical characteristics of early permian paragonite-bearing coal (No. 3) in the Jinyuan Mine, Tengxian coalfield, Shandong Province, Eastern China

The Early Permian coal is of great value in the Tengxian Coalfield, Shandon Province, Eastern China. This work deals with the new data focusing on mineralogical characteristics in the Early Permian Shanxi Formation No. 3 coal from the Jinyuan Mine. The Jinyuan coal is a low ash and highly volatile A bituminous coal. Minerals in the No. 3 coal mainly comprise of kaolinite, ankerite, illite, calcite, siderite, and quartz, with varying compositions of trace amounts of pyrite, jarosite, bassanite, anatase, and rutile. According to mineral assemblage in the coal plies, three Types (A to C) can be identified in the No. 3 coal. The dominant minerals in Type A are poorly-ordered kaolinite, illite, quartz, pyrite, and jarosite. Type B is mainly composed of well-ordered kaolinite, illite, siderite, ankerite, and calcite. Type C, with just one sample (JY-3-7c), which contains high proportions of calcite (54%) and ankerite (34%). Terrigenous minerals are elevated in coal plies that typically have relatively high contents of ash yield. The formation of syngenetic pyrite was generally due to seawater, while the sulphate minerals (jarosite and coquimbite) were derived from the oxidation of pyrite. Epigenetic vein-like or fracture-fillings carbonate minerals (ankerite, calcite, and siderite), kaolinite, and pyrite, as well as authigenic quartz were derived from the influx of hydrothermal fluids during different periods, from the authigenic to epigenetic. The paragonite in the coal may have been formed by the precipitated from Na-rich hydrothermal fluids. No effects of magmatic intrusion on mineralogy were investigated in this research

Geochemistry of carboniferous–permian coal from the Wujiawan mine, Datong coalfield, Northern China: modes of occurrence, origin of valuable trace elements, and potential industrial utilization

This paper provides new geochemical data focusing on valuable elements in the coal, parting, and floor samples in the No. 5 coal seam of the Taiyuan Formation from the Wujiawan mine, Datong coalfield, northern China. The minerals mainly consist of kaolinite, calcite, and pyrite, as well as trace amounts of quartz and illite. The No. 5 coal is enriched in Li, Ga, high field strength elements (HFSEs), and rare earth elements and yttrium (REY) when compared with world hard coals. Of particular interest is the high average concentration of Li (67.66 μg/g), which is around seven times higher than the value for world hard coals. Lithium, Ga, and HFSEs have strong inorganic affinities, whereas REY have organic affinities. The main carrier of Li, Ga, and HFSEs is aluminosilicate minerals, while REY appear to occur with organophosphorus. These HFSEs are enriched, both in the parting and in the adjacent coal samples. This suggests that these elements are likely to leach out during the diagenetic process. The distribution patterns of REY, along with the ratio of Al2O3/TiO2 and the figure of Zr/TiO2 vs. Nb/Y are suggestive of their derivation from felsic parent material. In the northern and eastern part of the Datong coalfield, there are several regions where the Li content is higher than the mineable grade, in particular in the northern Datong coalfield where there is a mine with an Li content of 294.6 μg/g. This is significantly higher than the mineable grade. Therefore, there is a potential for financially viable recovery of Li in these coals of the Datong coalfield