The effects of red beds on fluid flow and implications for the formation of volcanic-type uranium deposits in the Xiangshan basin, China

Abstract

The South China uranium metallogenic province is an important hydrothermal uranium metallogenic region in China, which is spatially and temporally associated with the Cretaceous-Neogene red beds. Previous studies suggest that the red beds might have played critical role in the ore-forming processes by providing oxidizing fluids. However, the effects of the red beds on fluid flow are poorly understood. In this study, numerical modeling was conducted to investigate the roles of red beds on ore-forming fluid flow in the Xiangshan basin in Jiangxi Province, hosting the largest volcanic hydrothermal uranium deposit in China. The modeling results show that the variation of the slope gradient of the red beds greatly affects the fluid flow patterns, whereas the change of thickness and permeability of the red beds has little influence on fluid flow pattern. The fluid can circulate into the volcanic and basement rocks driven by topographic relief of the red beds. Furthermore, for models with fault, although the fluid velocities in the fault were more than one order of magnitude larger than those in the surrounding strata, the overall fluid flow patterns in the strata did not show great variation. The modelling results suggest that the topographic relief of the red beds may have driven the oxidizing fluids into the underlying rocks which are necessary for uranium mineralization in the Xiangshan basin.