Geochemical Anomalies of the Late Permian Coal in the Guishan Coalfield, Eastern Yunnan, China

Abstract

The coal-bearing sequences of the Late Permian in southwest China are enriched in critical elements Sc, V, Co, Ni, Cu, Zn, Nb, Ta, Zr and Hf. Ascertaining the conditions and basis for the enrichment of critical elements in this area is very important to support the critical metal demands of China. In this study, we analyzed the concentrations of elemental compositions of coal samples collected from the Late Permian Guishan coalfield in the eastern Yunnan, China. The results show that the C4-Upper coal seam of the Feilongma mine and C5 + 10 coal seam of the Shipeng mine are indeed rich in critical elements. The average concentration coefficients (CC) of transition metal elements Sc, V, Co, Ni, Cu, and Zn are 3.23 and 2.93, respectively, in the two coal seams. The average CCs of high-field-strength elements Nb, Ta, Zr, and Hf and non-variable valence chalcophile elements Ga and In are 2.21 and 2.53, respectively, in the two coal seams. The C4-Upper coal seam of the Feilongma mine can be divided into two sections based on the different ash contents, and the CCs of the critical elements in the two sections are almost equal. The main minerals in the two coal seams are kaolinite, siderite, quartz, gypsum, rozenite and marcasite. Multiple indicators of provenance show that the enrichment of critical elements in the Guishan coalfield is controlled by clastic terrigenous material. The source area of the Guishan coalfield is Kangdian Oldland in the northwest, and the main clastic materials are related with high-Ti basalts from the Emeishan Large Igneous Province.