Metallogenic model of the carboniferous karst bauxites in Central Guizhou Province, Southwest China

Karst bauxites, the dominant mineral resources of Guizhou Province, southwest China, are hosted in the Lower Carboniferous Jiujialu Formation and the Lower Permian Dazhuyuan Formation. Currently, the total bauxite resources in central Guizhou area (CGA) have exceeded 500 million tons. Herein, we present a detailed petrographic, mineralogical, and geochemical characterization of the Tanguanyao and Ganba bauxite deposits located in CGA, with a particular focus on the differences in mineral composition. The aim of this study is to discuss the genesis of major minerals, analyze the sedimentary environment of representative bauxite deposits, and further reveal the metallogenic model of the Jiujialu Formation. Mineralogically, the Tanguanyao bauxite is mainly composed of diaspore, chamosite, anatase, and pyrite, whereas the Ganba bauxite consists of diaspore, chamosite, anatase, boehmite, kaolinite, and illite. This is because the Tanguanyao and Ganba bauxite deposits are located in different paleo-elevation, and their mineral compositions are significantly different due to the fluctuation of groundwater level. Mineralogical evidence suggests that the diaspore in the Tanguanyao and Ganba bauxite deposits also includes supergene crystallization in addition to metamorphic processes. In terms of sedimentary environment, the Tanguanyao bauxite deposit belongs to the phreatic bauxite type characterized by a reducing environment, while the Ganba bauxite belongs to the transitional type between the vadose and phreatic facies.