Meso-Cenozoic tectonic evolution and uranium potential evaluations of basins in Beishan-Gansu Corridor region

Beishan-Gansu Corridor region is located at the intersection of the plates of Tarim,North China,Kazakhstan,Siberia and Qaidam.During the Meso-Cenozoic,the region experienced movements of Indo-sinian,Yanshanian,Sichuanian,North China,Himalayan and Neotectonic,and over 20 medium-small size superimposed continental basins were formed.On the basis of analyzing the tectonis stress field,sediment-filling and structure-deformation,the general trending of tectonic evolution in the Meso-Cenozoic is summarized as three-time compressional uplifting and two-time extensional down-faulting.The different evolution of basins under the above mentioned setting can be divided into six stages according to characteristics of filled sediment.The sand bodies developed in down-faulted basins are favorable for uranium ore-formation as they are formed under humid paleoclimates,and rich in reducing matter.Therefore,the Lower-Middle Jurassic is selected as the main target horizon for sandstone-hosted uranium deposit,and the Lower Cretaceous as the minor one.Although the tectonic reactivation of the target horizon after its deposition was generally strong,the slopes formed in some basins could be favorable for the infiltration of uranium-and oxygen-bearing groundwater into sand bodies and form uranium deposits.According to the favorable sand bodies and tectonic reactivation,the northern parts of Chaoshui and Bayingobi basins are regarded as potential regions which are worthy of further exploration.