Deformation And Activity Characteristics Of Strike-slip Fault Zones In The Shunbei-4 Area,Tarim Basin

In recent years,with the discovery of the Shunbei oil and gas field,the study of the strike-slip fault zones in the Tarim Craton basin has been gradually deepened.The area studied in this paper is the Shunbei-4 area located in the western part of the Shuntuoguole low uplift,Tarim Basin,which is also one of the key oil and gas exploration blocks in the north-central part of the basin.In this paper,guided by the tectonic theory of the oil-bearing basin and based on the interpretations of 2D and 3D seismic data,the deformation characteristics,active periods and active intensity of the strike slip faults in the Shunbei-4 area are analyzed,and the formation mechanism of the strike slip faults in the Shunbei-4 area,Tarim Basin is discussed in combination with the orogeny around the basin.The results show that:(1)The identification characteristics of strike-slip faults in the Shunbei-4 area mainly include dislocated type,the roof shape,gypsum-salt fold,beaded type,dislocation type and flower structure in the sections,and overlapped,oblique,echelon and narrow graben in plane.(2)The strike-slip faults in the Shunbei-4 area have obvious characteristics of "layered deformation,plane segment and multi–stage activities ".In vertical direction,the deep faults are mainly erect in section,linear or oblique in plane,branch faults are developed upward,and combine with the mid-shallow faults to form flower structure,while the shallow faults are echelon,overlap or narrow graben in plane.Transversely,the strike-slip faults develop compressional,extensional or translational segments at different stratigraphic interfaces,which are characterized by weak compressional structural deformation and strong extensional structural deformation.The main active periods of the strike-slip faults include the middle Caledonian,late Caledonian and late Hercynian.(3)NNW and NNE strike-slip faults are mainly developed in the study area.The NNW main strike-slip faults occurred right-lateral strike-slip activity in the middle Caledonian,late Caledonian and late Hercynian,and the activity weakened from north to south.The NNE secondary strike-slip faults mainly occurred in the middle Caledonian sinistral strike-slip activity and weakened from east to west.(4)The strike slip faults in the Shunbei-4 area have the forming mechanism of "bidirectional compression and independent extension",and the NNW strike-slip fault system is closer to the strike slip fault system in the Tabei uplift,which is controlled by the north to south compression stress caused by the multi-period subduction of the Tianshan Ocean in the northern margin of Tarim Basin.The NNE strike-slip fault system is closer to strike-slip fault system in the Tazhong uplift and is controlled by the NW compression stress generated by the closure of the Altyn ocean in the southern margin of Tarim Basin.