The Geological Characteristics And Material Sources Of Permian Bauxite In Western Guangxi

Western Guangxi is rich in bauxite resources.There are two ore deposit types,Permian sedimentary type and the quaternary accumulation type, with the quaternary bauxite being widely used. Accumulation type bauxite is formed by Permian sedimentary bauxite after weathering and accumulation. Sedimentary type bauxite in western guangxi is located on ancient karst surface of Permian Maokou group, at the bottom of the Heshan group. The mineral-bearing system is composed of bottom weathering crust and upper aluminum-bearing rock series. The thickness of mineral-bearing system is greatly impacted by the ups and downs of the karst landform. The paper aims to discuss the material sources of sedimentary bauxite based on the typical geochemical composition,zircon U-Pb age, Hf isotope and zircon trace elements analysis.In accordance to microscope, X-ray diffraction（XRD） and electron probe analysis, the minerals in the ore mainly includes diaspore, chamosite, goethite, anatase, and a small amount of kaolinite. The main existence of diaspore is idiomorphic-subidiomorphic, fragmental or oolite structure.Geochemical analysis reveals constant elements of sedimentary bauxite ore are mainly Al₂O₃, SiO₂, TFe₂O₃, TiO₂ and the LOI, about 99% of the total amount, other elements content is relatively small, usually less than 1%. Among these constants, the amount of Al₂O₃, with an average of 53.7%, fluctuates, showing an inverse correlation with that of SiO₂ and Fe₂O₃. In the range of trace element, bauxite enriched sulfophile element, acid soil element and radioactive elements, alkaline and alkaline earth elements undergo a loss, while siderophile element has both enrichment and losses. Sedimentary bauxite is rich in rare earth elements, especially in light rare earths. Light rare earth element has an obvious fractionation effect within, Whereas internal fractionation effect of heavy rare earth elements are faint.U-Pb Age of detrital zircon shows a single peak, largely concentrating around 260 Ma. The majority of detrital zircon with clear volatility band and poor grinding degree demonstrates the bauxite metallogenic material mainly comes from the same issue of magmatic rocks, and sedimentary process handling distance is not long.The probe of the geochemical features of bauxite and detrital zircon U-Pb age as well as the characteristics of trace rare earth elements analysis illustrate: igneous rock associated with the mantle plume of Mount Emei and Arc magmatic rocks on the southwest margin of south China plate are the key source materials of sedimentary bauxite. Magmatic rocks in the process of the formation may be a mixture of mantle and crust material; The Cambrian strata, devonian strata, even the Cathaysian block may provided its formation with a small amount of material, despite a small proportion. The formation of sedimentary bauxite in western guangxi and the carbonate rocks at the bottom of bauxite are closely related.