Impact of Diagenesis and Hydrocarbon Charging on Sandstone Uranium Mineralization: An example of Toutunhe Formation in Liuhuanggou area, southern Junggar Basin

Key words: 
• southern margin of Junggar Basin /
• J₂t sandstone /
• diagenesis /
• hydrocarbon /
• sandstone-type uranium deposit

Abstract: To study the relationship between diagenesis-fluid evolution and uranium mineralization of J₂t sandstone in Liuhuanggou area, the southern margin of Junggar basin, finally assessing the metallogenetic potentiality. By means of microscope, X-diffraction and scaning electron microscopy, the author conducted that the studied rock are mainly rock-fragment fine sandstone, which underwent shallow burial period, deep burial period and hypergene-thermal period diagenetic evolution, finally suffered from relatively strong compaction, cementation and dissolution. The clay minerals are mainly kaolinite. There are also some fine sparry and micrite carbonate minerals, a few of siliceous cementations, fine grain pyrite and limonite locally. The diagenetic environment may experienced acid-weak alkalicy-acid and syngenetic oxidation-reduction in the shallow burial period-0xidation/reduction in the transitory elevation period-reduction enhancing in the deep burial period-oxidation in the period of large scale lifting evolutionary process. Simultaneously, hydrocarbon charging on the sandstone were proved by the following evidence:field investigating, oil and gas inclusions verificating, total acidolysis hydrocarbon range from 5.72 μL/kg to 449.14 μL/kg, mainly for the methane, C-O stable isotope values of calcite are -25‰~-6.7‰, 11.1‰~18.9‰, respectively, which influenced the geochemical properties(Eh and pH) of sandstone. The above diagenetic and hydrocarbon evolution controlled the migration, accumulation and localization of uranium, namely it formated and locatly conserved some small interlayer oxidation type uranium deposits in the early phase and formed some groundsurface phreatic oxidation type uranium deposits in the later preiod.