Provenance of Uranium Mineralization of the Yuqia Area, Northwest China: Constraints from Detrital Zircon U-Pb Geochronology and Hf Isotopes

Many sandstone-type uranium mineralization sites have been identified along the northern margin of the Qaidam Basin in North China.Intense tectonism and multistage magmatism that occurred there have restricted the use of conventional techniques (petrogeochemistry) to deduce the sources of detritus and uranium in these sediments,and to further explore the sandstone-type uranium deposits.In this study,U-Pb geochronological and Hf isotopic analyses were conducted on detrital zircon grains collected from Jurassic to Paleogene sandstones exposed in the Yuqia area of the Qaidam Basin.The results indicate that the U-Pb ages of the analyzed zircon grains are clustered into four groups,285–229,498–401,999–806,and 2 520–2 305 Ma.The εHf(t) of the analyzed zircon grains ranges from -21.9 to +10.5,with two-stage Hf model ages (TDM2) concentrated between 2.1 and 1.3 Ga.Based on paleocurrent studies and results of petrological,detrital zircon geochronology,and Hf isotopic analyses,the Jurassic sediments in the Yuqia area were likely derived from the tectonic belt along the northern margin of the Qaidam Basin,such as the Qilian Mountains and the Quanji Block.In contrast,the Paleogene sediments were probably sourced from the northern margin of the Qaidam Basin and the Qilian Mountains.The uranium and thorium content and Th/U value of the rock mass and sedimentary strata in the source area show that the Indosinian Early Paleozoic uranium-rich granites and the Middle Jurassic uranium-rich strata of the northern margin of the Qaidam tectonic belt in the source area provide dual uranium sources for the Yuqia sandstone-type uranium mineralization.Therefore,the study area appears to be favorable for sandstone-type uranium mineralization and may have potential for uranium prospecting.