| Songliao Basin is a large terrestrial sedimentary energy basin in the north of China.In recent years,the exploration of sandstone-type uranium deposits in the south of the basin has made remarkable achievements.However,due to the late start of the exploration of sandstone-type uranium deposits in the north of the Songliao Basin,the unknown sedimentary law of ore-bearing strata and distribution of favorable sand bodies have restricted the research on the development law of oxidation zone,resulting in the bottleneck of the exploration of sandstone-type uranium deposits in the north of the Songliao Basin.Baiquan area is located in the northeast uplift area in the northern part of Songliao Basin.Yaojia Formation of the Upper Cretaceous is the main ore-bearing target layer in the northern part of Songliao Basin.Only some drilling holes were constructed in the oil system in this area in the 1990 s,and the seismic coverage area was relatively low.In recent years,the nuclear industry system has carried out a series of uranium exploration in this area,but the spatial distribution of favorable metallogenic facies belts and sand bodies is not clear,the metallogenic conditions are not clear,which seriously restricts the exploration and prediction of sandstone-type uranium deposits in the northern Songliao Basin.Aiming at the above problems,this paper makes a detailed analysis of stratification marks,formation production characteristics and depositional system of Yaojia Formation in Baiquan area of northern Songliao Basin through field geological survey,typical borehole core recording,well logging interpretation,single hole microfacies analysis,well profile analysis,plane sedimentary facies analysis,and microscopic petrology observation.Combined with the structural conditions,uranium source conditions,uranium bearing property analysis,sand body and sedimentary facies characteristics,and epigenesis reconstruction conditions,the uranium metallogenic potential of Yaojia Formation in Baiquan area is further evaluated.The following main understandings and conclusions are obtained:(1)Through data collection and secondary development,it is believed that the inversion structure on the east side of the Baiquan area is relatively developed,and the strata are obviously uplifted.After uplifting,the strata are denuded,resulting in the development of the "skylight" structure,changing the circulation state of groundwater,which is conducive to the infiltration of uranium-containing oxygen-containing water in the mineralization period.Uranium sources are abundant in the erosion source area around the study area,and various signs show that most of the uranium sources have been activated and migrated to the basin,the target layer Yaojia Formation gray construction sandstone is the most rich in uranium(2)The Upper Cretaceous strata in the study area are mainly formed in the Upper Cretaceous Quantou Formation,Qingshankou Formation,Yaojia Formation and Nenjiang Formation.In this paper,four stratigraphic division markers of the Upper Cretaceous strata in Baiquan area in the north of the basin are established based on the characteristics of lithology,petrography and logging curves,and the spatial distribution law and burial depth of the Yaojia Formation are preliminatively mastered.(3)The depositional facies of Yaojia Formation in Baiquan area of northern Songliao Basin are analyzed by field geological survey,typical outcrop profile data,borehole geological records and drilling and logging data.The identification mark of sedimentary facies was preliminarily established.Combined with the analysis of single pore facies and connected well facies,the plane distribution characteristics of sedimentary facies and the spatial distribution law of sand body characteristics were systematically sorted out,and the sedimentary facies types of Yaojia Formation in the area were roughly defined,including 3 sedimentary facies,7 subfacies and 12 microfacies.(4)In the study area,the sand bodies around Baiquan area are widely distributed,and 2-3 thick large sand bodies are developed vertically.The thickness of single layer of sand bodies is 20-50 m,and the connectivity of sand bodies is good.The grain size of sand bodies is mainly medium and fine sandstone.According to the theory of interlayer oxidation zone,it is inferred that there are two front lines of interlayer oxidation zone in Baiquan,and the Baiquan area is selected as a favorable area for uranium mineralization. |
