The zonal model for the paleo-weathering crust of the Xianrenyan bauxite deposit in Guizhou Province

Abstract：With the Xianrenyan bauxite deposit as an example and according to the evolution of mineral composition and chemical composition in the process of laterite weathering in the basic shale, the authors established a paleo-weathering crust zonal model for Zunyi bauxite deposits. The paleo-weathering crust is divided into four parts from top to bottom: (1) iron and aluminum crust zone, also known as the strongly weathered zone or the ultimate weathering zone; (2) iron and aluminum clay zone, also known as moderately weathered zone or the decomposition zone; (3) clay–pyrite zone, also known as weakly weathered zone or minor decomposition zone; (4) native shale zone. It is shown that the paleo-weathered crust was formed in the Jiusi Datang stage of Early Carboniferous period, as evidenced by fossil pollen identification and Rb-Sr isotopic dating, and it should be an in-situ residual product.