ANALYSIS ON THE EPIGENETIC REDUCING CONDITIONS OF NEOGENE IN-SITU LEACHABLE SANDSTONE URANIUM DEPOSITS IN BAICHENG-KAILU AREA OF SONGLIAO BASIN

Uranium precipitation and concentration are closely related to the types and content of reducing agent, such as organic material, pyrite, oil and gas. The content of organic carbon and its humic acid and pyrite in Neogene System in Baicheng-Kailu area is not enough for uranium mineralization. However, the oil and gas in deep layer may pierce into the sand body of Neogene Daan formation to make up the low content of reducing material of sandstone. As regards the oxidation, Da'an formation belongs to phreatic-interformational type, which provides basic conditions for sandstone type of uranium deposit. However, the content of kaolinite is lower than that of the ore-bearing formation in Yili Basin, indicating weak oxygenic water and metallogenetic conditions. In some extent, it explains why large-scale Neogene uranium deposits in Songliao basin are not found so far.