Study On Sedimentary System Quan Tou Formation-YaoJia Formation In Southwestern Of Songliao Basin

The southwestern Songliao Basin,as a first-level structural unit area,is an important hydrocarbon accumulation and sandstone-type uranium-rich integrated mining area.Since uranium deposits are mainly enriched in sedimentary sand bodies,it is extremely important to study favorable sand bodies and sedimentary systems in the study area.First of all,based on the comprehensive field,drilling,seismic,logging and other geological data,this paper uses sequence stratigraphic analysis methods to compare the strata in the study area and establish the stratigraphic framework of each layer in the study area.Then,combined with the characteristics of geological structural evolution,paleo-geomorphic characteristics,provenance change characteristics and experimental analysis and test data,sandstone type uranium deposit enrichment in the study area,the characteristics of tectonic environment sand body and the distribution and evolution of sedimentary system formed were comprehensively analyzed,and the distribution of favorable uranium deposit area was further predicted.The result show that:Four sedimentary facies types,alluvial fans,rivers,deltas,and lakes were mainly developed during the deposition period of Quantou Formation-Yaojia Formation in the study area.During the K2 q and K2 y periods,the sedimentary system of the southwest marginal zone was obviously controlled by provenance,and the supply area of the provenance developed the alluvial fan-braided river system,and the sand bodies were mainly distributed in the fan subfacies and braided river channel microfacies.The lithology is mainly composed of conglomerate sand,coarse and medium fine sandstone with thin layers of argillaceous siltstone,silty mudstone and mudstone.Both the K2 qn and K2 n periods were dominated by lacustrine deposits.In the period of K2 qn,the study area was dominated by lacustrine facies,and some areas developed delta facies deposits,lacking large-scale sand body deposits,and were not thick.At this time,sand bodies mainly existed in underwater distributary channel microfacies and estuary bar microfacies.The lithology is mainly composed of interbedded fine sandstone,argillaceous siltstone and silty mudstone.The K2 n sand body is mainly developed in thin and small sand beaches or sandy shallow lake microfacies,and the lithology mainly develops thick gray and black gray mudstone,and the thickness of the mudstone water barrier is stable.During the Quantou Formation-Nenjiang Formation in the southwestern Songliao Basin,the predicted favorable uranium deposits are distributed as follows:vertically,the main ore-bearing layers are K2q and K2y;horizontally,they are mainly distributed near the Baxiantong of the Quantou Formation and around Zhanggutai-Xi'ersu-JinbaotunShuangliao;Yaojia Formation Yihuta-Tongliao-Tongliao-Qianjiadian-Zhonghui Gutian,gamma spit southward to the edge of the basin and the Jinbaotun-Shuangliao area.Uranium metallogenic laws indicate that the favorable sedimentary systems for uranium deposits in the southwest are the Quantou period alluvial fan-braided river sedimentary system,and the Yaojia Formation braided river-delta front-shore-shallow lake sedimentary system.