The geologic features of mineralization at the Dongsheng uranium deposit in the northern Ordos Basin (Central China)

The Dongsheng uranium deposit, localized in the northern Ordos Basin in northern Central China, is among the largest deposits of thistype in China. It occurs in the sandstones of the Middle Jurassic Zhiluo Formation. The crystalline rocks of the Yinshan and Daqingshanorogenic belts in the northern Ordos Basin are the source of uranium for the deposit. The Dongsheng deposit shows the main characteristicsof a sandstone uranium deposit of interstratal oxidation zone, including specific hydrothermal rock alteration. It displays distinct lithologicand mineral zoning. The sandstones of the oxidation zone are variegated and oxidized, and the sandstones of the reduction zone are gray andlight gray medium- to coarse-grained and underwent albitization, carbonatization, chloritization, epidotization, pyritization, etc. Ore-bearingsandstones occur in the transitional oxidation-reduction zone, being confined mainly to the reduction zone. Uranium minerals are predominanthigh-temperature coffinite and subordinate brannerite and uraninite. The homogenization temperature of fluid inclusion in the sandstone cementis 150–160 °C. The performed geological analysis suggests that the hydrothermal alteration of the uranium deposit is intimately related to thesynchronous Mesozoic regional magmatic events in the Ordos Basin.