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 this type in China. It occurs in the sandstones of the Middle Jurassic Zhiluo Formation. The crystalline rocks of the Yinshan and Daqingshan orogenic belts in the northern Ordos Basin are the source of uranium for the deposit. The Dongsheng deposit shows the main characteristics of a sandstone uranium deposit of interstratal oxidation zone, including specific hydrothermal rock alteration. It displays distinct lithologic and mineral zoning. The sandstones of the oxidation zone are variegated and oxidized, and the sandstones of the reduction zone are gray and light gray medium- to coarse-grained and underwent albitization, carbonatization, chloritization, epidotization, pyritization, etc. Ore-bearing sandstones occur in the transitional oxidation-reduction zone, being confined mainly to the reduction zone. Uranium minerals are predominant high-temperature coffinite and subordinate brannerite and uraninite. The homogenization temperature of fluid inclusion in the sandstone cement is 150-160 degrees C. The performed geological analysis suggests that the hydrothermal alteration of the uranium deposit is intimately related to the synchronous Mesozoic regional magmatic events in the Ordos Basin. (C) 2011, V. S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B. V. All rights reserved.