Relationship between hydrocarbon-containing fluid and metallogenesis in Dongsheng sandstone-type uranium deposit

Dongsheng sandstone-type uranium deposit is located at the contact zone of grayish green sandstones and gray sandstones in north Ordos Basin,which is controlled basically by paleo-interlayer oxidation zone.The uranium deposit is generally platy and uranium mainly exists as uranium-bearing minerals(coffinite etc.) and adsorbed uranium,with UO2 contents of 46.72%-74.60%.Proportions of the adsorbed uranium,U+ 6 and U+ 4 vary from section to section in this deposit.Based on the characteristics of ore deposit,lithogeochemical environment and ore-controlling factor,the origin of the uranium deposit is different from that of other sandstone-type uranium deposit in the world.Hydrocarbons-containing heat fluid from Late Jurassic to Early Cretaceous tectono-thermal events participated in ore-forming processes.The heat fluid not only contributed to the activation,migration and enrichment of uranium,but also provided a reducing environment for this uranium deposit,and played an important role in the conservancy of the deposit.The gray and grayish green sandstones formed by hysterogenic reduction can be used as the lithogeochemical markers for exploration of uranium deposit.