Sandstone-hosted uranium mineralization characteristics and prospecting direction in Delingha area,northeast margin of Qaidam basin
Located in the northeastern margin of the Qaidam basin,Delingha area has been surveyed for quite a long time,but no breakthrough was gotten in the exploration of sandstone-hosted uranium deposits.Based on detailed field geological surveys and indoor analysis,the newly discovered uranium prospects of Deke,Dedong,and Wanggaxiu was reviewed and carefully studied.The research reveals that the main host layer for sandstone type uranium deposit in the Delingha area are the Lower Youshashan formation(N1y),Upper Youshashan formation(N2y)and Shizigou formation(N2s)of the Middle Miocene.The uranium-bearing rocks primarily consist of brownish-red,yellow,brownish-yellow,yellow-green medium-to-coarse grained sandstone,as well as gray-green calcareous fine-grained sandstone.The ores also contain a large amount of organic matter,often presenting in the combination of the"organic matter+pyrite+uranium mineral".Field geological survey revealed that,sandstone-hosted uranium mineralization in the study area is closely related to fault structures,mainly occurred near the wing of the anticline structure and also developed in some faults.Data from the petroleum sector indicated the presence of a～200 m thick set of uranium-rich dark mudstones of the Carboniferous Keluke formation(C2h)in Delingha,with uranium contents over(30～50)×10-6,which can serve as a deep uranium source for the later deposited ore-bearing formations.The structural combination of"anticline+fault"in the study area forms a favorable tectonic decompression zone,providing a conducive pathway for the upward migration of deep uranium-rich ore-forming fluids.Based on this analysis,the exploration for sandstone type uranium deposits in the northeastern margin of the Qaidam basin,especially in Delingha,should primarily focus on"exudative"sandstone-type uranium deposits.The target horizons should mainly include the Lower Youshashan formation,Upper Youshashan formation,and Shizigou formation of the Miocene,special attention should paid to the overlapping areas of"anticlines+faults".
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