Abstract
High concentrations of Mn were observed in 5-2 coal (Jurassic age) from Qinglongsi coal mine in the Northern Ordos Basin. To study the occurrence characteristics and sedimentary environment of the 5-2 coal (3.9 m), 22 samples were collected from a mining face. The test result indicates that the 5-2 coal is in low-ash, high-volatile, very low-sulfur, and bituminous rank, with high inertinite content. The minerals in Jurassic 5-2 coal are composed primarily of kaolinite, siderite, calcite, quartz, pyrite, K-feldspar, and fluorapatite. The Mn element is enriched in the upper part of the 5-2 coal seam with an average of 1243.01 μg/g, which is about 17.5 times higher than the average of world hard coal. The concentration level of Mn has a positive correlation with that of Fe2O3 and carbonate minerals. A weak reduction environment of the coal-accumulating swamp may induce the enrichment of Mn, which is mainly carried by siderite in the 5-2 coal.