Study On Sedimentary System Of Quantou Formation-Yaojia Formation In Southeastern Uplift Of Songliao Basin

As a primary tectonic unit of the Songliao basin,the southeast uplift area has been extensively explored since the 1960s,which not only proves that the southeast uplift area of the songliao basin is a rich reservoir of oil and gas,but also an important integrated uranium mining area.Uranium deposits are mainly concentrated in sedimentary sand bodies,so it is very important to study the sedimentary system of southeast uplift.Based on the comprehensive field,drilling,seismic and other geological data,on the basis of sedimentary facies and sedimentary system is divided into a key,combination of sequence stratigraphy analysis,on the southeast uplift area of QuanTou?Q?-YaoJia?Y?,tectonic environment,sedimentary facies,sedimentary system sand body characteristics are studied,for provides the important basis of sandstone type uranium deposits.Four types of sedimentary facies,including alluvial fan,river,delta and lake,developed in the sedimentary period of Q and Y formation in the research area,were identified through detailed study of field outcrops,rock thin sections and logging data,and 12 subfacies and 25 microfacies were further divided.The sedimentary system in the southeastern margin is obviously controlled by the provenance,and the alluvial fan-braided river system is developed in the marginal supply area.The braided river of Q formation is developed in the area of Changchun-Jiutai-Fanjiatun.The monolayer sand body is generally 12-26m thick,and the vertical direction is the transition from the braided river in the Q₁ to the meandering river Q₄.The delta is developed in the west of the study area and the sand body is mainly distributed in distributary channel microfacies and estuary dam microfacies.The Qn formation is composed of lacustrine sediments,mainly in the water-inflow system domain and the high-water level system domain,and lacks large-scale sand body deposition.The Qn₁section developed shore-shallow lake sediments.In the Yang area,shallow-sandy lake and shore-beach sand bodies were developed,with a thickness of 6-8m in general.The lake basins of the second and third sections of the qing dynasty were enlarged,mainly composed of deep lake and semi-deep lake deposits,and the thickness of mudstone water barrier was stable.The lake area of Y formation is reduced in the late development stage of the depression,which is manifested in the shore-shallow lake-delta front facies sedimentary system.The sand-mudstone interbeds are mainly distributed in the Qingshankou anticline belt and the Denglouku anticline belt,and developed in the subaqueous distributary channel microfacies and the estuary dam microfacies.The sandstone thickness is generally 7-10m,and there is a lack of horizontal continuity.The uranium mineralization rules indicate that the favorable sedimentary systems for uranium deposits in the southeastern uplift are the alluvial fan-braided river sedimentary system in the Q period,the Y formation delta frontier-shore-shallow lake sedimentary system and the Qn formation sandy shallow-lake-binghu sandbank sedimentary system.During the sedimentary period of Q formation,braided river and fan-shaped braided channel sand bodies were deposited in the Jiutai area of Fanjiatun.During the sedimentary period of Qn formation,the mudstone water-proof layer was developed,and the dark mudstone water-proof layer was developed at the upper and lower levels.Although the sedimentary sand bodies in the front margin of the delta of Y formation are small and discontinuous in thickness,the hot arid and semi-arid climate is conducive to the activation and migration of uranium,which is an important factor affecting the enrichment of low-grade uranium in the Y₁ formation.