Detrital zircon U-Pb geochronology of uranium-bearing sandstone in the lower member of Luohe Formation in the southwest margin of the Ordos Basin: Implications for the lithospheric extension

This paper is the result of mineral exploration engineering.

Objective In recent years, the study of sandstone-type uranium deposits has become a hotspot among geologists, especially the study of uranium-bearing strata.

Methods Based on LA-ICP-MS U-Pb dating of detrital zircons from the lower part of the Lower Cretaceous Luohe Formation uranium-bearing sandstones in Zhenyuan area, southwestern Ordos Basin, the provenance and tectonic significance of uranium-bearing sandstones are discussed.

Results The results show that the detrital zircon U-Pb ages of the lower member of the Lower Cretaceous Luohe Formation are mainly distributed in five age intervals: 166-370 Ma (n=49), 388-472 Ma (n=14), 1744-2150 Ma (n=14), 2241-2740 Ma (n=14) and 615-1623 Ma (n=9), besides 615-1623 Ma whose peak age can not be determined, and the corresponding peak ages are 272 Ma, 427 Ma, 1899 Ma and 2493 Ma, respectively.

Conclusions Comparative analysis of detrital zircon U-Pb age spectra shows that the lower member of Lower Cretaceous Luohe Formation in the study area has six source areas, including the eastern part of the North Qilian orogenic belt, the North Qinling orogenic belt, the Xingmeng orogenic belt, the Helan Mountain, the basement of the North China Plate and the Alxa Block, among which the eastern part of the North Qinling orogenic belt and the North Qilian orogenic belt are the main source areas. The detrital zircon ages show that the southwest margin of Ordos Basin formed a passive continental margin in Ordovician, the Silurian-Devonian transformed into a collisional orogenic belt, the Carboniferous-Permian transformed from an orogenic belt into a sedimentary basin, and the Jurassic-Cretaceous formed stable sedimentary strata to provide favorable space for uranium ore storage.