A preliminary study on the formation conditions and weathering leaching enrichment mechanism of secondary phosphorite in the Xinhua phosphate mining area, Zhijin, Guizhou

Abstract

The Xinhua phosphate mining are alocated in Zhijin County, Guizhou Province, is a famous superlarge low-grade phosphate deposit containing rare earth elements in the southwest of China.The average P2O5 grade of the deposit is 17.22%.The proven phosphorite ore resources are 1.348 billion tons, and the rare earth resources are 3 500 kilotons.In recent years, experts and scholars have found that the fluctuation of Xinhua phosphorite ore grade is closely related to weathering, leaching and enrichment effects.To further clarify the influence of weathering and leaching on the element geochemistry as well as the secondary enrichment of phosphate rock, the author focuses on the Gezhongwu ore block and carries out field observations and descriptions of phosphate rock series.A total of 19 chemical analysis samples were collected using block knocking method and 16 rock ore samples were identified through polarizing microscope.On these basis, identification and comprehensive research on the samples were conducted.The results show that the contents of P2O5 in the weathered phosphate rock are 8%-18%, higher than that in the primary phosphate rock, while the contents of MgO are 4%-7%, lower than that in the primary phosphate rock.The weathering intensity of phosphate rock is in the weak to mature stage.The formation of Xinhua weathered phosphate rock in Zhijin County is controlled by lithology, geological structure and hydrological conditions.The purpose of this paper is to provide new information for the further study of the influences of the secondary weathering mineralization of the ore deposit on the chemical composition of phosphate rock, to enrich the metallogenic theories of weathering eluvial phosphate mining in China and to provide the oretical guidance for the rational development and utilization of weathering phosphate resources in the mining area