Isotopic characteristics of metallogenic fluid and its genesis in Yunji uranium deposit of Xiangshan

Based on the study of C and O isotopic composition in gangue minerals calcite of metallogenic period, as well as He and Ar isotopic composition of metallogenic fluid inclusions in Yunji uranium deposit of Xiangshan, this paper discusses the sources of uranium ore-forming fluid in the deposit. Analytical test results show that the δ¹³C_V-PDB and δ¹⁸O_V-SMOW of calcite is respectively -9.4‰∼-3.1‰ and 4.7‰∼15.4‰, and the carbon in metallogenic fluid mainly comes from the mantle. The ³He/⁴He of fluid inclusions in calcite is 0.0615∼0.3760 Ra, significantly higher than the characteristic values in the earth crust (0.01∼0.05 Ra), Displaying the characteristics of mantle and crustal fluid mixing The ⁴⁰Ar/³⁶Ar is 314.4∼334.1, slightly higher than the isotopic composition of atmospheric argon (⁴⁰A/³⁶Ar = 2955), showed that there is meteoric end and a small amount mantle argon in the metallogenic fluid. Comprehensive analysis reveals that the uranium metallogenic fluid of Yunji deposits has deep genesis and it has the characteristics of crust-mantle mixing. (authors)