鄂尔多斯盆地北部特拉敖包地区紫色铀矿石特征及富集机理研究OA

Lower Cretaceous in Ordos Basin is the new target stratum for sandstone-type uranium deposits recently identified in China and purple uranium ores were found in the upper member of Lower Cretaceous Huanhe Formation.In this paper,ores characteristics were studied in petrology,spatial distribution and geochemical composition.Spatially,the purple uranium ore is located at a depth of 180-350 m,generally distributed in a scattered manner with a thin thickness.The uranium content in the purple uranium ore is 2 800×10-6.Purple uranium ore contains a high content of Fe2O3 but low contents of CaO、MgO、SiO2,the trace elements of Pb,Mo,Ba and Y are positively correlated with U.The LREE and HREE ratio in the rare-earth elements is 1.4.Eu and Ce both show positive anomaly and the content of Y is relatively high.These indicated that the purple uranium ore was formed in a highly oxidizing environment.The uranium ore are mainly composed of coffinite and with large amounts of strawberry-shaped pyrite in the fringe,and a large amount of charcoal remained on the local surface.In the later stage of mineralization,the grey orebody sandstone experienced reoxidation under the effect of uranium oxygen containing water from the northwest direction.Under the strong reduction conditions,U in the sandstone was re-concentrated and the pyrite was oxidized into limonite,giving rise to high uranium content in the purple mineral-containing sandstone.