Mineralogical and geochemical composition of the early carboniferous Li-enriched coals of the Zhaotong coalfield, Northeast Yunnan, China

Abstract

The Middle and Lower Carboniferous sedimentary sequences in the central and western parts of Guizhou, southwest China, are enriched in bauxite, and are characterized by increased levels of the critical element Li. In the adjacent area (northeastern Yunnan), the Lower Carboniferous sequences contain coal seams. Whether these coal seams are enriched in Li, and the provenance affinity between the bauxites and these coal seams are still unclear. In this study, the mineralogy and geochemistry of the C1 coal seam in the Wanshoushan Formation, Lower Carboniferous sedimentary sequences, Zhaotong Mining Area, northeastern Yunnan Province, were investigated. The results showed that the major minerals in the C1 coal seam are clay minerals, Al-bearing minerals, quartz, pyrite, and so on, most of which are of authigenic origin. This coal seam was enriched in Li, Cu, Zn, and so on with the Li concentration coefficient reaching to 8.92. The trace elements in the C1 coal seam of the Wanshoushan Formation and the elements in the bauxites of the Jiujialu and Dazhuyuan Formations were similar, and their provenance was the underlying Cambrian - Ordovician carbonate rocks.