Redox Environment For Mineralization Of Aeolian Sandstone Type Uranium Deposit In The Jingchuan Area,Ordos Basin,China

Uranium minerals in sandstone-type uranium deposits are affected by the geochemical properties of uranium elements,which are a kind of REDOX environment sensitive minerals.Whether it is the widely distributed fluvial uranium deposit or the recently discovered aeolian sand uranium deposit in Jingchuan area,the metallogenic location is the transition position of REDOX conditions.The main ore-bearing strata of fluvial uranium deposits in Ordos Basin are Jurassic Zhiluo Formation sandstone,and the main ore-bearing strata of aeolian sedimentary sandstone uranium deposits are Cretaceous Luohe Formation aeolian sandstone.Through the comparative study of REDOX environment of two types of sandstone-type uranium deposits,the metallogenic theory and field prospecting practice of uranium deposits in Ordos Basin are enriched,which has theoretical significance and practical value.The research data of REDOX environment of fluvial sandstone-type uranium deposits in the northern margin of the basin are abundant and detailed,while the REDOX parameter information of newly discovered aeolian sand-type uranium deposits in Jingchuan area is relatively insufficient.In this paper,through literature research,field investigation,logging core,collecting and sorting out the relevant data and experimental analysis of the research group（mainly through electron probe mineral analysis）,the symbiotic relationship of minerals in uranium enrichment horizon is studied and REDOX environment indicator parameters are found.The characteristics of trace elements and REDOX conditions of aeolian sandstone-type uranium deposits in Jingchuan area are discussed.Through the analogy of REDOX parameters and zoning of fluvial sandstone-type uranium deposits in northern basin,the REDOX environment of aeolian sandstone-type uranium deposits in Jingchuan area is studied.By summarizing and analyzing the REDOX characteristics of fluvial uranium deposits in the northern margin of the basin and aeolian sedimentary uranium deposits in Jingchuan area,the following new understandings are obtained:1.According to the results of probe test,the uranium minerals in Jingchuan area are divided into pitchblende,titanium-bearing uranium minerals and uranium stone.Uranium minerals have a strong symbiotic relationship with Fe²⁺and Ti.2.For the Jingchuan aeolian sand uranium deposit,the oxidation zone-REDOX transition zone（metallogenic belt）-reduction zone is divided,which is the same as the conditions for the division of REDOX zoning of other uranium deposits in the basin.The Jingchuan uranium deposit is similar to other uranium deposits in the northern part of the basin.They all have vertical color zoning characteristics.The oxidation zone is a red rock layer,and the REDOX transition reduction zone is a gray rock layer.3.The trace elements of uranium deposits in the northern margin of the basin and Jingchuan uranium deposits were compared.The content of trace elements in the northern part was higher than that in the Jingchuan area.The difference of trace element Cu,Sr content and Sr/Cu ratio shows that the organic carbon content of Jingchuan uranium deposit is lower than that of the northern uranium deposit,which is consistent with the desert and river sedimentary background.The overall climate environment of the Cretaceous in the Jingchuan area is an arid desert environment,while the Jurassic Zhiluo Formation in the northern margin is a warm and humid river environment.Jingchuan uranium deposit lacks internal reducing medium（charcoal,pyrite,etc.）.The reducing medium required for the formation of uranium deposit comes from the deep fluid upwelling along the fault,which is the external reducing medium such as oil and gas.In summary,by comparing the metallogenic REDOX conditions of the northern and Jingchuan uranium deposits.The main sedimentary facies of Jingchuan uranium minerals is desert facies,and the ore body is located in the gray sandstone layer of REDOX transition zone.