Mineralogy of the Pennsylvanian coal seam in the Datanhao mine, Daqingshan Coalfield, Inner Mongolia, China: Genetic implications for mineral matter in coal deposited in an intermontane basin

This paper deals with the mineral matter in the coal and associated strata from the Datanhao mine, Daqingshan Coalfield, which is closely located to the previously-reported Adaohai and Hailiushu mines of the same coalfield. The coal from the Datanhao mine is mainly high-ash and low-sulfur bituminous. The mineral assemblage in the coal is dominated by quartz, kaolinite, with varying proportions of carbonates (calcite, ankerite and siderite), small proportions of muscovite, illite, pyrite and anatase. The associated non-coal (claystone) samples have similar mineral assemblage, except that most non-coal samples contains less quartz than the adjacent coal plies. Although deposited in the same intermontane basin of the orogenic belt, the Yinshan Upland, the Datanhao coal seam shows different mineralogical characteristics from those of the nearby Adaohai and Hailiushu mines. This may reflect the different sediment-source regions during the peat accumulation stage. The sediment source for the Datanhao coal was probably the Ordovician quartz-rich sandstone or the Sinan quartzite in the surrounding sub-uplifts. High proportions of quartz in the Datanhao coal suggest intense terrigenous input into the paleomire and a short distance from the sediment source region. Different mineralogical characteristics of the coals from the three mines (Datanhao, Hailiushu, and Adaohai) of the Daqingshan Coalfield are probably due to the different source material in their respective surrounding subuplifts within the intermontane basin. Kaolinite displaying graupen, tabular and vermicular textures, and the common presence of β-quartz in the intra-seam non-coal bands from the Datanhao coal seam indicate that most of these bands are tonsteins (altered airborne volcanic ash). The original magma is probably high level volatile-rich silicic in composition.