Mineralogy and geochemistry of the No. 6 Coal (Pennsylvanian) in the Junger Coalfield, Ordos Basin, China |
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| Authors: | Shifeng Dai Deyi Ren Chen-Lin Chou Shengsheng Li Yaofa Jiang |
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| Institution: | aKey Laboratory of Resource Exploration Research of Hebei Province, Handan 056038, China;bChina University of Mining and Technology, D11, Xueyuan Road, Haidian District, Beijing 100083, China;cIllinois State Geological Survey (Emeritus), 615 East Peabody Drive, Champaign, IL 61820, USA;dXuzhou Institute of Architectural Technology, Xuzhou 221008, Jiangsu, China |
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| Abstract: | This paper discusses the mineralogy and geochemistry of the No. 6 Coal (Pennsylvanian) in the Junger Coalfield, Ordos Basin, China. The results show that the vitrinite reflectance (0.58%) is lowest and the proportions of inertinite and liptinite (37.4% and 7.1%, respectively) in the No. 6 Coal of the Junger Coalfield are highest among all of the Late Paleozoic coals in the Ordos Basin. The No. 6 Coal may be divided vertically into four sections based on their mineral compositions and elemental concentrations. A high boehmite content (mean 6.1%) was identified in the No. 6 Coal. The minerals associated with the boehmite in the coal include goyazite, rutile, zircon, and Pb-bearing minerals (galena, clausthalite, and selenio-galena). The boehmite is derived from weathered and oxidized bauxite in the weathered crust of the underlying Benxi Formation (Pennsylvanian). A high Pb-bearing mineral content of samples ZG6-2 and ZG6-3 is likely of hydrothermal origin. The No. 6 coal is enriched in Ga (44.8 μg/g), Se (8.2 μg/g), Sr (423 μg/g), Zr (234 μg/g), REEs (193.3 μg/g), Hg (0.35 μg/g), Pb (35.7 μg/g), and Th (17.8 μg/g). Gallium and Th in the No. 6 Coal mainly occur in boehmite, and the Pb-bearing selenide and sulfide minerals contribute not only to Se and Pb contents in the coal, but also probably to Hg content. A high Zr content is attributed to the presence of zircon, and Sr is related to goyazite. The REEs in the coal are supplied from the sediment-source region, and the REEs leached from the adjacent partings by groundwater. |
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| Keywords: | Coal Mineral matter Trace elements Boehmite Junger Coalfield Ordos Basin |
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