Genesis of the South Zhuguang Uranium Ore Field, South China: Pb Isotopic Compositions and Mineralization Ages

U-Pb isotopic analyses indicate that ores from the South Zhuguang uranium ore field, south China, have high common (non-radiogenic) Pb contents, with variable and relatively radiogenic initial Pb contents. The U-Pb isochron method was used to date these ores, with plots of Pb-208/Pb-204 and Pb-207/Pb-204 versus Pb-206/Pb-204 being used to identify sample suites with similar initial Pb isotopic ratios and to normalize variable initial Pb isotopic ratios. The resulting U-Pb isochrons indicate two substages of uranium mineralization at similar to 57 and 52 Ma, with a later hydrothermal reformation at similar to 49 Ma, which homogenized Pb isotopic compositions. Initial Pb isotopic systematics indicate that the ore-forming fluid was characterized by high Pb-206/Pb-204 and Pb-207/Pb-204 ratios and low Pb-208/Pb-204 ratios, suggesting that the ore-forming fluid was sourced from Cretaceous-Paleogene red-bed basins, rather than from magma or the mantle, with consideration of mineralization ages.