| Tarim Basin,the largest Mesozoic-Cenozoic inland sedimentary basin in China,has a strong tectonic activation zone on its northern margin,which is inconsistent with the metallogenic theory that the number of sandstone-type uranium deposits in interlayer oxidation zone is more than that in relatively stable tectonic zone.However,with the investment of uranium exploration in the basin,a series of uranium mineralization points and uranium deposits with industrial value have been found in the northern margin of the basin in recent years,which indicates that the northern margin of the basin has the potential to form mediumsized and large-scale uranium deposits,and also poses new challenges to the sandstone-type uranium metallogenic theory in the strong tectonic activation area.In this paper,the petrology,diagenesis and its evolution characteristics,sequence of diagenesis and mineralization,characteristics of element geochemistry and its change rule of the target stratum are systematically studied through field geological survey and indoor sample analysis.Summarizes the characteristics of the post-regeneration of the ore-bearing sand body in the Kezilenur Formation,on the basis of this,combined with the geological factors such as the spatial distribution characteristics of the sand body in the target stratum,the constraints of epigenetic transformation on uranium mineralization are clarified,and the metallogenic model for sandstone-type uranium mineralization of the interlayer oxidation zone in strong tectonic activation area is established,which provides reference for the exploration of sandstone-type uranium deposits in strong tectonic activation area.The target stratum of sandstone-type uranium deposit in Tarik area is a set of coal-bearing clastic rocks deposited near provenance.The maturity of composition and structure of sandstone is low;the diagenetic evolution of target stratum is low,and the diagenesis mainly includes compaction,cementation,metasomatism,dissolution,etc.The results of trace element analysis show that U,Re,Mo and other elements in the transitional zone are obviously positive anomalies,U is positively correlated with Re and Mo,and the anomalous elements are controlled by the oxidation-reduction transitional zone,which is comparable with the typical sandstone-type uranium deposits in the interlayer oxidation zone.Therefore,Re and Mo can be used as indicative elements for uranium prospecting in Tarik area.There are strong epigenetic alterations in the target stratum,such as interlayer oxidation,hydrocarbon reduction,etc.The distribution of authigenic minerals(such as pyrite,limonite,uranium minerals)in the alteration zones of interlayer oxidation zone has a certain regularity.Through microscopic identification,there are at least two large-scale oil and gas reduction events in the target stratum,and the first stage of oil and gas participates in the uranium mineralization process,and the second stage of oil and gas contributes little to the uranium mineralization.The process of diagenesis and mineralization in the study area can be divided into four stages.The first stage is the stage of synsedimentation-early diagenesis,starting with the deposition of the target stratum and ending with the Upper Cretaceous,which controls the formation of the target stratum;the second stage is the large-scale metallogenic stage of interlayer oxidation,which controls the development of interlayer oxidation zone from Upper Cretaceous to the end of Paleogene;the third stage is the stage of deep burial,beginning in Miocene and ending in Pleistocene,which terminates uranium mineralization of interlayer oxidation zone;and the fourth stage is the stage of tectonic transformation,which lasts from the Pleistocene to the present,during this period,the target stratum emerges from the surface and begins to accept the leaching of surface water and the transformation of oil and gas reduction. |
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