| As one of the most important uranium deposits reasonable exploration of sandstone type uranium deposits is of great significance to promote the green and low-carbon development of national economy and society.The sandstones of Sifangtai Formation in Sanzhao sag of Songliao Basin are rich in uranium resources,but there are few studies on the distribution of uranium-rich sandbodies,uranium ore characteristics and metallogenic conditions.This paper,by using drilling,logging and seismic geological data,combined with regional geological background of three hollow square table set of stratigraphic framework and(phase)for identification of sedimentary microfacies are divided,on this basis,the study area is studied quartet group of sedimentary system evolution,and further analysis depicting rich uranium distribution characteristics of sand body,observe the quartet group characteristics of sandstone type uranium deposit,Finally,the geological conditions and metallogenic models of uranium ore are summarized and analyzed from four aspects: uranium source,deposit,structure and REDOX conditions.First of all,based on a large number of drilling and logging data,this paper divides the Sifangtai Formation into three sections in a more precise manner.Sedimentary system at the same time,studies have shown that the quartet group lithology is mainly for the gray sandstone,siltstone and purple mudstone,meandering river facies,including riverbed detainment sedimentation,beach,flood land,natural levee,crevasse splay five types of sedimentary microfacies,riverbed detainment sedimentation in gray gravel coarse sandstone,sandstone,the main beach as the gray fine sandstone and siltstone,high maturity,good separation,The sand body is thick.The embankment subfacies is dominated by argillaceous siltstone and purplish red mudstone.In the first section,the stratum is mainly channel sand body and floodplain sand body,with local crevasses.The thickness is about 20m～60m,and the thickness is relatively stable,the grain size gradually becomes fine,and the natural gamma ray anomaly at the bottom is significant.The strata of the second member are mainly floodplain,and the channel sand body is interbedded,with local crevasse fans and natural dikes.The thickness of the stratum is about 30m～60m,and the stratum thickness is relatively stable,and there are obvious natural gamma anomalies.The strata of the third section are mainly floodplain,with relatively developed natural dikes.Locally,lenticular and thin bedded channel sand bodies and crevage fans can be seen,with thickness of 20m～40m,and thinning from east to west,without obvious anomalies of natural gamma ray.Combined with the observation of the characteristics of uranium deposits in The Sifangtai Formation,uranium content is the largest in fine and medium sandstones.Uranium deposits are mainly in the form of independent minerals,namely pitchblende and uranite,and a large amount of symbiosis pyrite can also be seen.At the same time,the natural gamma ray(> 260API)is the most direct logging identification feature of uranium deposits in this area.The coupling of the natural gamma ray anomaly with the spatial distribution of sedimentary units such as edge beach and retained deposits in the first and second member of sifangtai formation indicates that the edge beach and channel sandbodies are the main uranium rich sandbodies of sandstone type uranium deposits in this area.Highland from source of uranium fluid(such as groundwater,surface precipitation)provide abundant uranium source,its by the late tectonic compression structure of denudation of the skylight infiltration quartet group thickness stable and continuous flood land,the river channel sand body,combined with the tectonic extrusion formation of the deep fracture will also reducing fluid(oil and gas,etc.),It can reduce the oxidized uranium in the sand body and lead to uranium enrichment and mineralization. |
