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Abstract: This paper describes the mineralogy and geochemistry of a batch of 17 coal samples covering the Late Permian Longtan Formation from a drill core from the Taoshuping mine, eastern Yunnan Province, China. The results show that minerals in the coals include quartz, kaolinite, calcite, chamosite, pyrite, mixed-layer I/S and minor marcasite, siderite, anatase, ankerite, and dolomite. Modes of occurrences of authigenic quartz and chamosite suggest that they were mainly precipitated from Fe–Mg-rich siliceous solution derived from the weathering of Emeishan basalt, which was induced by mantle plume eruption during late Middle Permian and covers most places of southwest China. Kaolinite and mixed layer I/S are mainly of detrital origin. Correspondingly, the elevated trace elements, including V, Cr, Co, and Ni, in the coals are closely related to Emeishan basalt. Trace amounts of detrital calcite, ankerite and siderite in the coals probably originated from the Maokou limestone. The frequent presence of high temperature quartz indicates that felsic volcanic eruption took place through the entire Late Permian Epoch. Mineral matter in the coals was not only derived from Emeishan basalt in the Kangdian Oldland, but also felsic volcanic ashes, mafic volcanic ashes, and limestone of the Maokou Formation. [Copyright &y& Elsevier]

Abstract: The mineralogy and geochemistry of a superhigh-organic-sulfur (SHOS) coal of Late Permian age from the Yanshan Coalfield, Yunnan Province, southwestern China, have been studied using optical microscope, low-temperature ashing plus X-ray diffraction analysis, scanning electron microscope equipped with energy-dispersive X-ray spectrometer, a sequential chemical extraction procedure, and inductively coupled plasma mass spectrometry. The M9 Coal from the Yanshan Coalfield is a SHOS coal that has a total sulfur content of 10.12%–11.30% and an organic sulfur content of 8.77%–10.30%. The minerals in the coal consist mainly of high-temperature quartz, sanidine, albite, muscovite, illite, pyrite, and trace amounts of kaolinite, plagioclase, akermanite, rutile, and dawsonite. As compared with ordinary worldwide (bituminous coals and anthracite) and Chinese coals, the M9 Coal is remarkably enriched in B (268 μg/g), F (841 μg/g), V (567 μg/g), Cr (329 μg/g), Ni (73.9 μg/g), Mo (204 μg/g), and U (153 μg/g). In addition, elements including Se (25.2 μg/g), Zr (262 μg/g), Nb (20.1 μg/g), Cd (2.07 μg/g), and Tl (2.03 μg/g) are also enriched in the coal. Occurrence of high-temperature quartz, sanidine, muscovite, and illite in the M9 Coal is evidence that there is a volcanic ash component in the coal that was derived from acid volcanic ashes fallen into the swamp during peat accumulation. Occurrence of albite and dawsonite in the coal and strong enrichment of some elements, including F, S, V, Cr, Ni, Mo and U, are attributed to the influence by submarine exhalation which invaded along with seawater into the anoxic peat swamp. Abundances of lithophile elements, including rare earth elements, Nb, Y, Zr, and TiO2, indicate that the silicate minerals in the coal were derived from the northern Vietnam Upland to the south of the basin. [Copyright &y& Elsevier]