Geochemistry and mineralogy of Late Carboniferous coal (No. 8) from the Jialequan Mine, Xishan Coalfield, Shanxi Province, China: evidences for the geologic controls of trace elements

Abstract

Xishan Coalfield is a vital coking coal production base in Shanxi Province of China. This study describes the geochemical, mineralogical, and carbon isotope values of two host rocks and ten coal benches of the Late Carboniferous (No. 8) coal of the Jialequan Mine from Xishan Coalfield. The coals are medium-ash coal (22.42%) and are of bituminous B rank (1.16–1.26%, Ro,ran). Minerals in the No.8 coal are dominated by clay minerals and calcite, along with quartz, pyrite, and anatase. The clay assemblages include kaolinite, illite, and mixed-layer I/S. Sulfate minerals, including bassanite, anhydrite, and jarosite, are identified in several coal benches. The No.8 coal is enriched in Li, Zr, Nb, Hf, Ta, Pb, Th, and U in comparison with world hard coals. Lithium is largely distributed in kaolinite and illite. Zirconium, Hf, Nb, Ta, and Th are related with clay minerals (kaolinite) or anatase if present. Lead dominantly occurs in sulfide minerals, including pyrite/marcasite or water-bearing Fe-oxysulfates, and to a lesser extent in galena. Uranium has an affinity with the carbonate minerals. The ratios of Sr/Ba and redox-sensitive elements indicate an oxic-dysoxic seawater environment during the coal deposition. REY in No.8 coal are related with clay minerals and phosphates minerals, and are derived from the terrigenous input (moyite of the Yinshan Upland), seawater influence, and HREY-rich hydrothermal injection in coal basins.