Mineralogy and geochemistry of the Late Triassic coal from the Caotang mine, northeastern Sichuan Basin, China, with emphasis on the enrichment of the critical element lithium

•Concentration of Li in the investigated coal is ∼20-times higher than that in the world coals.•Chlorites are the dominant host of Li in the coal.•Cookeite, chamosite, and a chlorite mineral of intermediate composition were identified.•The coal has been subjected to a multi-stage injection of hydrothermal fluids.•Chlorite in the coal was derived from Li-bearing solutions.