Geochemical characteristics and UPb chronology of detrital zircon in the Neogene Shizigou Formation, Qigequan area, western Qaidam Basin: Implications for tectonics, paleoclimate, and uranium sources

Uranium deposits have been recently discovered in the Qigequan mining area, located at the transition zone between the Cenozoic strata of the Qaidam Basin and Altyn Tagh orogenic belt. This study presents detailed petrogeochemical and UPb detrital zircon geochronological analyses of sandstones from the Cenozoic Shizigou Formation within this region. This study aims to clarify the provenance and explore the interrelations among stratigraphy, tectonics, paleoclimate, hydrocarbons, and the genesis of sandstone-type uranium deposits. Detrital zircon ages are clustered in two periods: 343–542 and 200–285 Ma, corresponding with rock units in the Altyn Tagh and East Kunlun orogenic belts. Comparative analysis of zircon age spectra reveals the Altyn Tagh and Qimantag mountains as the primary source areas, with the Altyn Tagh being the most significant. Major, trace, and rare earth element analyses suggest relatively stable tectonic conditions and an oxidizing sedimentary environment during the deposition of the Lower Shizigou Formation, with a high concentration of reducing media. Low chemical weathering in the source region, coupled with the angularity of detrital zircon grains, indicates rapid uplift under arid climatic conditions, leading to the swift transport and deposition of unweathered clastic material. Oxygenated surface waters transported uranium from erosion areas into the structural cavities of the Lower Shizigou Formation, depositing it in oxygen-rich sedimentary layers. Subsequently, ascending hydrocarbon and brine-rich fluids intruded along structural fractures, leaching uranium from the strata and creating a favorable reducing environment for uranium mineralization. The Cenozoic subduction and collision of the Indian and Eurasian plates triggered the rapid uplift of the Altyn Tagh, driving climatic changes that generated the necessary redox conditions for uranium ore formation. These findings provide valuable insights into the sedimentary processes, tectonic evolution, and exploration of sandstone-type uranium deposits.