塔里木盆地顺北及邻区走滑断裂体系差异发育特征及成因机制探讨

Characteristics and formation mechainism of the strike-slip fault networks in the Shunbei area and the surroundings,Tarim Basin

塔里木克拉通盆地内部走滑断裂体系滑移距小、变形弱、埋深大,其成因机制一直以来是构造领域研究的热点和难点问题。基于高密度三维地震新资料,开展了顺北及邻区系统编图和走滑断裂精细解析工作,对比解剖和明确了顺北东区和顺北西区走滑断裂体系的差异发育特征及活动规律,并探讨了其成因机制。结果表明:顺北东区发育约NE30°走向近平行主次级走滑断裂体系,深部主干走滑断裂变形强于次级走滑断裂且自西向东挤压程度增强,上覆雁列断层活动整体呈现自西向东增强的变化;顺北西区走滑断裂体系南北差异明显,北部以一组由塔北隆起向南延伸减弱的NW向断裂体系发育为主,南部以一组数量多、密度大、多期活动的约NE15°走向断裂发育为主。顺北地区走滑断裂体系“南北分区展布、东西差异活动、多段拼接生长”的发育特征,揭示其由多套形成于不同区域应力场下的走滑断裂体系分区差异展布并向腹部延伸对接而成,推测这与晚奥陶世盆缘受到多方向挤压的构造事件有关。

Intracratonic strike-slip fault systems in the Tarim Basin are characterized by small displacement,low strain deformation and large burial depth.These attributes make it challenging to study the formation mechanism of these fault systems.Based on the recently obtained high-density 3D seismic data,3D mapping and detailed analysis of strike-slip faults are conducted in Shunbei and its surrounding area.The distinct characteristics of fault array development in the east and west of the Shunbei area are analyzed and clarified,and the formation mechanism of the strike-slip arrays is also discussed.It was found that a set of~30NE trending strike-slip faults,including the major and secondary strike-slip faults,are developed in eastern Shunbei.At depth,strike-slip deformation is stronger in the major faults than in the secondary faults,and the compressive strain increases gradually eastward in the major faults.In the shallow strata en echelon fault activity intensifies eastward.The strike-slip fault systems differ between the northwest and southwest of Shunbei.The northwest mainly develops a set of NW-trending faults spreading southward from the Tabei uplift,whereas in the southwest a set of~15NE trending faults with high density and multistage activity are developed.The strike-slip fault systems in Shunbei are characterized by“north-south zonal distribution,east-west differential activity and multi segments coalescing growth”,indicating the fault systems consist of multiple sets of strike-slip faults formed in different areas under distinct regional stress fields and later coalesced in the interior Tarim Basin,and their formation is probably related to multi-directional compressional tectonic event at the basin boundaries in the Late Ordovician.