Lithium and redox-sensitive (Ge, U, Mo, V) element mineralization in the Pennsylvanian coals from the Huangtupo coalfield, Shanxi, northern China: With emphasis on the interaction of infiltrating seawater and exfiltrating groundwater

Geochemistry of low-ash and medium-sulfur coal and non-coal horizons from the Huangtupo coalfield, Shanxi, northern China was investigated. The economic potential of coal mining for critical elements (e.g., U, Li) was investigated in the present study. Uranium, Mo, and Sr are slightly enriched in the Pennsylvanian Huangtupo coal; with U and Mo reaching their highest concentrations in the topmost coal bench underlying the limestone roof. These enrichments are probably related to a marine invasion in the basin. The Al₂O₃/TiO₂ ratio and the Zr/TiO₂-Nb/Y relationship indicate the input of felsic-intermediate materials. The similar rare earth elements plus Y (REY) distribution patterns between non-coal horizons and Yinshan Upland granite suggests a detrital input from the Yinshan Upland. The Li mineralization, common in coals of the Qinshui basin, is represented by Li enrichments in the lower coal benches associated with the parting and floor mudstones. This mineralization is probably related to the neutralization of infiltrating seawater by acidic groundwater. This acidic water, possibly derived from the Triassic Li-Cs-Ta pegmatites and exfiltrated through the clastic deposits into the coal seam, could cause some additional Li enrichments in the lower coal benches and associated clastic rocks. Some coal benches (e.g., from the Jincheng and Changzhi Mines) in the Qinshui Basin meet the mining grade of lithium (80–120 μg/g, on whole coal and/or rock basis) for coals, making them promising for commercial Li recovery.