Two Distinct Geological Environments from Sedimentary to Diagenesis Stages: Examples from Sandstone-Type Uranium Deposits, Turpan-Hami Basin

The formation of sandstone-type uranium depositsis not only related to sedimentary environment, but also related to diagenesis environment. This paper illustrates the original sedimentary environment of the Shuixigou Group using sedimentology methods and analysis results of element geochemistry in mudstone, and discusses the diagenesis environment by means of fluid inclusions and Raman spectrum analysis in sandstone in the southwestern margin of the Turpan-Hami basin. The results show that two distinct geological environments from sedimentary to diagenesis stages are observed in the Shuixigou Group. In sedimentary stage, mudstones have the Sr/Ba value of less than 0.3 and the average B content of 46.35× 10^-6, and the fresh water faunal fossils are observed, which indicates that in-situ sedimentary environment shows warm, wet, oxygen-deficient and fresh water.However, the diagenesis environment with middle-lower temperature(156.1 ℃)and supersalinity(about 7.4%)as evidenced from fluid inclusions is the same as that of the present formation water with a salinity of 7.8%. The research results indicate that the mineralization ages of uranium are basically coincident with the main diagenesis stages, which are(104± 1)Ma, (24± 1)Ma and (7± 0)Ma, respectively.So it is possible that supersaline hydrocarbon-bearing fluid with middle-lower temperature should be a favorable mineralization environment of uranium.