The “coal–bauxite–iron” structure in the ore-bearing rock series as a prospecting indicator for southeastern Guizhou bauxite mines

Bauxite deposits in southeastern Guizhou occur in the lower Permian Liangshan Formation. The rock series bearing the sedimentary bauxite exhibit a typical “coal–bauxite–iron” structure, in which the lower part consists of bauxitic shale intercalated with siderite concretions, the middle part consists of bauxitic rock intercalated with multilayer lenticular or earthy bauxite, and the upper part consists of carbonaceous shales and sandstones intercalated with coal seams. The paralic, coastal and paludal depositional environments at one time had a stable tectonic setting. By studying the elemental geochemistry of the ore-bearing rock series, it can be seen that the common presence of the “coal–bauxite–iron” structure has resulted from (1) the extensive desilication and iron depletion during the formation of the sedimentary bauxite due to the varying physical and chemical environment, and (2) the sufficient supply of organic matter by the external environment. Such geological anomalies that resulted from the physical and chemical changes during the formation of the layered structure in the ore-bearing rock series can serve as a mineralization indicator in prospecting for new deposits.