准噶尔盆地腹部两类走滑断裂带及其构造变形样式

Two Types of Strike⁃Slip Fault Zones and Their Tectonic Deformation Patterns in the Central Junggar Basin

走滑断裂带对中国西部压扭性叠合盆地大中型油气田形成与分布具有重要的控制作用,也是研究难点之一.基于高密度三维地震资料,本文采用多种地震构造解析技术,瞄准噶尔盆地腹部侏罗系开展了精细走滑断裂带解释和变形样式分析.在燕山Ⅱ幕构造活动期,侏罗系发育了NWW向左行压扭性和NE向左行张扭性两类走滑断裂带.它们都是由4组剪切断层复合而成,共同遵从左行简单剪切模式,但几何学特征和构造属性差异很大.NWW和NE向走滑断裂带不存在共轭剪切关系,而是在钝夹角区(135°左右)普遍具有弧形联合与归并趋势.在构造变形中,两类同期左行走滑断裂带弧形联合控制了变形区域旋扭形变和剪切破裂,构成了一个大尺度“面”状旋扭构造体系.旋扭构造变形样式对中亚陆内造山带研究具有一定借鉴意义,也为压扭盆地的油气勘探实践提供了新思路.

The strike-slip fault zone plays an important role in controlling the formation and distribution of large and medium oil and gas fields in the compressional superimposed basins in western China,which is also one of the difficult problems in the study.Based on the high-density 3D seismic data,a fine strike-slip fault zone interpretation and deformation pattern analysis of the Jurassic in the central Junggar basin using a variety of structural analysis techniques are conducted in this study.During the second episode of Yanshan tectonic movement,two types of strike-slip fault zones of NWW left-lateral compression-torsion and NE leftlateral tension-torsion were developed in the Jurassic.They were both composed of four groups of shear faults,which followed the simple left-lateral shear mode,but they were very different in their geometric characteristics and structural attributes.There is no conjugate shear relationship between NWW and NE strike-slip fault zones,but arc-shaped joint and merge in the blunt angle zone(about 135°).In the tectonic deformation,the arc-shaped joint action of two types of left-lateral strike-slip faults controlled torsion deformation and shear fracture in the deformation area,forming a large scale clockwise torsional structural system.The deformation pattern of torsional structure can be used as a reference for the study of intracontinental orogenic belts,and also provides a new idea for oil and gas exploration in compression-torsional basins.