摘要
详细研究鄂尔多斯盆地含铀砂岩的碳氧同位素地球化学特征,探讨了鄂尔多斯盆地砂岩型铀矿富集成矿机理及多种能源共存的内在联系,从而进一步探讨盆地型多种能源富集成藏(矿)的潜在的规律.含铀砂岩的碳酸盐胶结物C-O同位素测定结果表明:所有样品δ13CPDB值变化范围为-4.2‰^-23.62‰,大部分样品δ13CPDB值落在碳酸盐岩δ13CPDB值范围内或略低,4个样品δ13CPDB值均低于-10‰;样品中碳酸盐胶结物含量为0.5%~16.12%.综合分析表明:含铀砂岩所属的中侏罗统直罗组在浅变质作用过程中受到过来自深部流体的交代渗滤作用,在淋滤与溶解盆地下古生界的海相碳酸盐过程与古生界的油气相互混合,在砂岩的成岩(成矿)过程中并且具有一定比例有机质的加入,使得含铀砂岩的胶结物中碳同位素值变低.含铀砂岩在成岩(成矿)过程中和一定比例有机质进行水岩交换作用,有机质的参与促使本区铀矿质的络合与运移,最终在有利氧化-还原条件下沉淀和富集.
Based on the analyses of C-O isotopes from the sandstones of sandstone-type uranium deposits in the Ordos Basin, the mechanism of genesis of multiple energies and the formation of different ore deposits in this basin were studied. The geochemical data show that the δ13^ CPDB values range from -4.2%0 -23. 62%o and the carbon contents of carbonate cement are from 0. 5% - 16. 12%, respectively. The samples with very low contents of δ13^ CPDB（-10%0‰-23. 62‰） are due to the addition of organic materials during the metamorphic formation of these sandstones. Carbon and oxygen isotopic data of carbonate cement in sandstones indicate that the deep fluids once eluviated the sea-facies carbonate in Paleozoic sedimentary layers and brought the carbonate to participate during the alteration of sandstones in Zhiluo Group （middle Jurassic）, accompanying with this processing, some organic carbons derived from the Paleozoic sedimentary layers were involved during the alteration and cementation of these sandstones. This process is conducive to the migration and precipitation of U compounds under favorable redox conditions.
基金
国家重点基础研究发展(973)计划(2003CB214600)资助
