鄂尔多斯盆地西南缘中下侏罗统地层物源及构造演化对铀成矿的制约

The southwest margin of the Ordos basin is located at the intersection of the Alxa massif, the Qinling orogenic belt and the Qilian orogenic belt, which is challenging to the study of the provenance and uranium mineralization of the uranium bearing rock.This paper selects the Zhiluo Formation and Yan 'an Formation sandstones in the Jingchuan area to conduct clastic zircon U-Pb dating and trace element research.The analysis results show that the clastic zircon ages of the Zhiluo Formation sandstones in Jingchuan area are 215-767 Ma and 1 501-1 905 Ma; The clastic zircon ages of Yan 'an Formation sandstones are 215-453 Ma, 1 506-1 918 Ma and 2 136-2 579 Ma, respectively.Compared with the isotopic chronology of the source area, it is believed that the provenance components of the Zhiluo and Yan 'an Formation sandstones are relatively complex, mainly from the Alxa block, followed by the northern margin of the North China plate and the North Qilian area.During the sedimentary period from Yan ' an Formation to Zhiluo Formation, Qilian Mountain and Alxa landmass were rapidly uplifted and denuded, providing provenance for Zhiluo Formation, and the proportion of provenance provided by Paleozoic and Mesozoic intrusive rocks gradually increased.The study shows that the strata of middle Jurassic can be taken as the prospecting target strata in the west margin of basin, and the ore bearing strata near the basin gradually become younger.