伊犁盆地砂岩型铀成矿同位素地质特征

Characteristics of isotope geology of sandstone-type uranium deposit in Yili basin,Xinjiang

本文对伊犁盆地可地浸砂岩型铀矿及其蚀源区进行了同位素地质特征研究 ,结果表明 :伊犁盆地砂岩型铀矿具有多时期成矿的特点 ,其成矿年龄分别为 82 4、6 0、1 1 4、7 1、3 5Ma,而主要成矿期集中在第三纪的中、上新世。伊犁盆地南侧蚀源区发育有以海西期为主的花岗岩和火山岩 ,前者为2 93— 31 6Ma,后者为 2 35— 2 5 9Ma。从含矿砂体精选出的锆石 ,其U Pb同位素年龄为 30 8Ma ,与蚀源区花岗岩、火山岩的时代一致 ,从而肯定了含矿砂体的物质来源。此外 ,通过对含矿砂体和蚀源区岩石U Pb同位素体系演化特征的研究 ,指出伊犁盆地砂岩型铀矿具有多铀源富集的特点 ,这些铀源分别是 :地层沉积时形成的富铀砂体 (主要的 )

This paper expounds the isotopic characteristics of in-situ leachable sandstone-type uranium deposits and provenance area of Yili basin.The results suggest that the sandston-type uranium deposits are characterized by multi-stage metallization.Uranium mineralization ages of 82.4Ma,60Ma,11.4Ma,7.1Ma and 3.5Ma are obtained.The main mineralization stages are concentrated in Miocene and Pliocene,Neogene Period.Hercynian granites and volcanic rocks with isotope ages of 293-316Ma,235-259Ma respectively are developed in the southern provenance area of the basin.The U-Pb age of clastic zircons from ore-bearing sandstone is 308Ma which is corresponding to the age of granites and volcanic rocks in the provenance area indicating the material source of uraniferous sandstone.Moreover,the study of the U-Pb isotopic system evolution of ore-bearing sandstone and provenance area rocks shows the characteristics of multi-source uranium concentration of sandstone-type uranium deposits in Yili basin.The sources are uraniferous sandstone(main source) accumulated during the deposition and the uranium leached from provenance area rocks by weathering.