Distribution characteristics of heavy minerals in the sandstone of Zhiluo Formation of northern Ordos Basin and its implication

In recent years, the evaluation of sandstone-type uranium ore in Ordos Basin has made great progress, and the problems about provenance and uranium sources of the target layer have drawn the most attention for a long time. Based on the comprehensive analysis of heavy minerals, this paper discusses the source of detrital materials and ore-forming uranium sources in Zhiluo Formation of sandstone type uranium deposits in the northern Ordos Basin. The results show that the heavy mineral assemblages of Zhiluo Formation in the study area mainly include garnet, zircon, epidote, biotite, spinel, as well as a small amount of apatite, sphene, rutile and hornblende, tourmaline, ilmenite, which reflects the parent rock type of mainly intermediate and high-grade metamorphic rocks and intermediate acid magmatic rocks. The heavy mineral characteristic index reflects the characteristics of the garnet-bearing metamorphic rock as the main source rock type and proximal deposition. The comprehensive analysis shows that the main provenance areas of Zhiluo Formation are the Middle-Lower Archean Proterozoic Wulashan Rock Group, the Middle Proterozoic Zartai Group and intermediate acid intrusive bodies of various periods in Daqingshan and Wulashan regions in the northern part of the basin. Among them, the ancient basement metamorphic rocks and various periods intermediate acid magmatic rocks generally have high uranium content, with an obvious uranium migration along the NW-SE direction, providing the initial uranium source for the later uranium mineralization.