准噶尔盆地车排子铀矿产地元素地球化学特征及其地质意义OA

In order to reveal the weathering degree,source properties,tectonic background and mineralization process of source rocks in Chepaizi uranium occurrences of Junggar Basin,elemental geochemical studies were carried out in this paper.The results show that:Sedimentary rock samples from Shawan Formation,Taxihe Formation,and Dushanzi Formation in Chepaizi uranium occurrence have SiO2 contents ranging from 40.70%to 78.70%(averaging 53.71%),Al2O3contents ranging from 4.72%to 15.60%(averaging 11.63%),and are characterized by high K2O/Na2O ratios(averaging 1.46).In the mineralized sandstones,the contents of SiO2,FeO/Fe2O3,and CaO,as well as the loss on ignition,are significantly increased,while the contents of Al2O3,Fe2O3,and MgO are relatively decreased,indicating that significant redox reactions occurred during the uranium mineralization process.The average w(LREE)/w(HREE)ratio is 10.39,showing a marked fractionation between light and heavy rare earth elements.The chemical weathering degree(average CIA index value is 73.83)in the source area is moderate and the source is dominated by neutral igneous rocks with dual sources from the north and the south(Zaire Mountains and Tianshan Mountains),and the tectonic background is the continental island arc.The uranium mineralized belt are simultaneous enriched in Mo,Re,Co and Se which is obviously different from the typical zonation of Mo,Se and Re in the phreatic or interlayer oxidation sandstone uranium deposits.The sandstone-type uranium deposits in Chepaizi uranium occurrence were formed in a weak oxidation-reduction transition environment,which have some difference to the typical interlayer oxidation uranium deposit,while have some characteristics of the"seepage"uranium metallogenic model.