Petrology and major-trace elements characteristics of the Indosinian uranium-rich pluton in southern Xiangshan volcanic basin

Abstract:Petrology and major-trace elements analysis shows that Xiankou pluton is a compound granitic body characterized by high SiO2, high K and slightly peraluminous nature, thus belonging to the high-K calc-alkaline series. Chondrite-normalized REE patterns are characterized by right-inclined shape, rich light rare earth, significant negative europium anomalies, and more obvious fractionation of LREE than that of HREE. Trace elements are characterized by rich Rb, Th, U, Pb, Ta, Nd, Hf, obviously poor Nb, Ce, Pr, Zr, Ba, and significant variation of Rb/Sr ratio（0.92～6.52）, with the average uranium content being 19.55ppm, suggesting that the pluton belongs to uranium-rich granite. The tectonic setting discrimination diagram of trace elements and main elements shows that Xiankou pluton is a uranium-rich granite formed in an environment of intraplate post-orogensis. The discovery of Xiankou pluton provides a new train of thought for resolving the uranium source problem of the Xiangshan uranium orefield, and might guide the prospecting for granite type uranium deposits in southern Xiangshan.