Abstract
AbstractMinerals in the Late Permian coals from the Niuchang-Yigu mining area, Zhenxiong County, northeastern Yunnan, China, were investigated using optical microscopy and low temperature ashing plus X-ray diffraction (LTA + XRD). The results showed that minerals in the coal LTAs are mainly quartz, kaolinite, chamosite, mixed-layer illite/smectite (I/S), pyrite, and calcite, with trace amounts of marcasite, dolomite, and bassanite. The authigenic quartz generally occurs in collodetrinite or as a filling in cleats or cell cavities. This silica was mainly derived from aqueous solutions produced by the weathering of basaltic rocks in the Kangdian Upland and from hydrothermal fluids. The presence of β-quartz paramorph grains in collodetrinite probably indicates that these grains were detrital and came from a volcanic ash. Clay minerals are generally embedded in collodetrinite and occur as cell-fillings. Pyrite occurs as framboidal, anhedral, and euhedral grains and a cell-filling. The coals are high in pyrite and the high pyrite content probably results from seawater invading during the stage of peat accumulation. Calcite generally occurs as vein-fillings, indicating an epigenetic origin.
Highlights
Understanding the abundance and occurrence modes of minerals in coal is significant both academically for developing conjectures concerning coal-forming processes and pragmatically for optimizing coal utilization (Ren 1996; Ward 2002; Dai et al 2012c).T
The results showed that minerals in the coal Low-temperature ashing (LTA) are mainly quartz, kaolinite, chamosite, mixed-layer illite/smectite (I/S), pyrite, and calcite, with trace amounts of marcasite, dolomite, and bassanite
Previous work on the origin and mode of occurrence of mineral matter in the Late Permian coals from eastern Yunnan includes that of Chen et al (1992), Dai and Chou (2007), Dai et al (2008, 2014), and Wang et al (2012, 2013)
Summary
Understanding the abundance and occurrence modes of minerals in coal is significant both academically for developing conjectures concerning coal-forming processes and pragmatically for optimizing coal utilization (Ren 1996; Ward 2002; Dai et al 2012c). Tian Chongqing Research Center of State Key Laboratory of Coal Resources and Safe Mining, Chongqing 400042, China. Previous work on the origin and mode of occurrence of mineral matter in the Late Permian coals from eastern Yunnan includes that of Chen et al (1992), Dai and Chou (2007), Dai et al (2008, 2014), and Wang et al (2012, 2013). Tonsteins derived from pyroclastics in the Late Permian coal seams from eastern Yunnan have been studied (Zhou 1999; Zhou and Ren 1983; Zhou et al 1982, 1990; Dai et al 2014). We present new data on the abundances, origin, and mode of occurrence of minerals in coal from two cores, the ‘‘NYa’’ and ‘‘NYb’’ holes drilled through the Longtan and Changxing Formations in the Niuchang-Yigu mining area, Zhenxiong County, northeastern Yunnan
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