Influence of geomorphology and leaching on the formation of Permian bauxite in northern Guizhou Province, South China

Abstract Geomorphology is an important control on the formation of bauxite. However, geomorphological research on bauxite deposit formation is usually hampered by the lack of systematic detailed data collection. This study focuses on the Wuchuan–Zheng'an–Daozheng (Wu–Zheng–Dao) area of northern Guizhou Province, South China, an area containing bauxite deposits of the Dazhuyuan Formation. These deposits formed during the early Permian in a period associated with the peak timing of the late Paleozoic Ice Age (LPIA). This study used data from 329 drillcores within the Dazhuyuan mining district (DMD) to generate high-precision geomorphological reconstructions for the period of bauxite formation. This includes a series of contour maps showing the total thickness of the bauxite deposit, ore grades, the thickness of Lower (bauxitic claystone) and Upper (bauxite ore) members of the bauxite formation, and the distribution of different types of bauxite ore. These maps indicate that thicker deposits of bauxite are concentrated in deep depressions, whereas no bauxite is found in highly elevated erosional regions. High-grade bauxite ores, including clastic, oolitic, and porous types of mineralization, are located within depressions or in gently sloping areas, whereas low-grade bauxite deposits, including massive bauxite and bauxitic claystone mineralization, are located at the bottom of depressions or are present as thin units within uplifted areas. The geochemistry of the drillcore samples from the study area indicates that leaching is the main control on bauxite ore quality in the study area. Finally, a low groundwater table and water-permeable underlying units provide good drainage, which also contributes to the generation of high-grade bauxite ores.