Sedimentary Faces And Geochemical Characteristics Of Uranium Enrichment In Sifangtai Formation In XX Area Of Songliao Basin

Sandstone type uranium deposits in China are concentrated in the oil-bearing basins of the north,mostly located in the basin edge.The newly discovered uranium-enriched stratum was located in the uplift area of the basin,which was the new type"basin inner edge"construction style.This type provides a new direction for exploration of sandstone-type uranium deposits.In this article,recording of core drilling and sampling and logging research of core in the east-west and north-south of XX area in the Songliao basin,the uranium deposits are found mainly in the gray sandstone in the member 1 and 2 of Sifangtai formation.According to the analysis of petrography and mineralogy of four borehole sections in the direction of the research area,it is believed that the sandstone is mainly composed of feldspar lithic sandstone,and the holes in the east and west are non-mineralized holes and mineralized holes respectively,and the corresponding mineral-bearing sandstone is transformed from feldspar sandstone to feldspar lithic sandstone-lithic sandstone,which reflects the special composition and structural characteristics of sandstone,closely contact with uranium enrichment.Through the color,sedimentary structure,inclusions and special minerals of the core of the borehole,the microfacies identification markers of the Sifangtai formation of the study area are determined.Based on the comprehensive analysis of the rock facies assemblage,sedimentary structure and log data,the Sifangtai formation in the study area was established as a set of meandering river-delta?plain?sedimentary system.On the basis of the analysis of single well and even well sedimentary facies,the characteristics of the microfacies distribution in each section of the sifang group are clarified:On the vertical,the main development of the east is the meandering river-delta?plain?-meandering river sedimentation,which reflects the shallow and turbulent waters of the Sifangtai stage in the study area.On the longitudinal,the east mainly develops the meandering river sedimentation and the west mainly develops the meandering river-delta?plain?sedimentation,which is regarded as the source direction of the research area in the east and the sedimentary center of the research area in the west.Based on geochemical analysis of surrounding rock,mineralized sandstone and uranium sandstone in the study area,the characteristics of trace elements in cobwebs were basically the same,and the enrichment and loss degree are slightly different,which may be affected by the later fluid transformation.Besides U element,other elements enrichment degree is generally low,and there is no common enrichment of elements such as Mo-V-Re-Sc in typical interlayer oxidation zone sandstone-type uranium deposits,which is different from typical sandstone-type uranium deposits.The correlation trend shows that the correlation between uranium and other trace elements in the uranium-rich sandstone is more obvious than that in the surrounding rock and mineralized sandstone.According to rare earth elements chondrite standardized distribution curve,the surrounding rock,mineralized sandstone and uranium sandstone are all inclined to the right and have the characteristics of light rare earth enrichment,and the internal fractionation of light rare earth components is stronger than that of heavy rare earth.Most of?Eu are negative anomalies,and individual was positively abnormal which may be caused by plagioclase.The value of?Ce is nothing abnormal or slightly negative.The standardized distribution curve of rare earth elements in North American shale shows that the distribution of surrounding rock,mineralized sandstone and uranium sandstone is similar to that of continental crust,and the difference may be caused by the fluid alteration in the later stage.The Ce_anomnom index of all three shows that the conditions of the ancient water medium are reducing environment.The diagram of Hf-La/Hf?La/Sc-Co/Th?REE-La/Yb?Zr/Sc-Th/Sc indicates that the source of the surrounding rock,mineralization sandstone and rich uranium sandstone are felsic rocks.The diagram of Th-Co-Zr/10?La-Th-Sc?La/Sc-Ti/Zr also reflects that the source may come from various sources such as the granite and yanshanian granite,and the tectonic background of the source rock may be the active continental margin and the continental island arc.According to the analysis of uranium-rich strata by grant method,it is found that many trace elements migrate out in the process of uranium enrichment,showing different activities for LREE and HREE.Based on the analysis of the sedimentary facies and environmental sensitive elements in the four boreholes in the near east and west,the uranium is found to be concentrated in meander channel facies of member 1 in Sifangtai formation,and the drier the climate,the higher the salinity of water and the reduction of the ancient medium,the better the enrichment of uranium.In general,the uranium-riched stratum in XX area is a non-typical sandstone type uranium deposit,obviously controlled by sedimentary facies,and the enrichment of uranium is influenced by various factors.