Enrichment and Occurrence of Mn in 5-2 Coal from Qinglongsi Coal Mine, Northern Ordos Basin, China.

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.