四川盆地中部高石梯-磨溪地区FI9走滑断裂带构造特征与演化

Structural Characteristics and Evolution of No.9 Strike-Slip Fault Zone in Gaoshiti-Moxi Area in Central Sichuan Basin

四川盆地中部高石梯-磨溪地区已识别出多组走滑断裂,为深化川中地区走滑断裂的构造几何学与运动学特征认识,基于川中地区深钻井及高精度三维地震资料,详细刻画高石梯-磨溪地区FI9走滑断裂带的构造几何学特征,建立断层三维构造模型.通过构造回剥反演重建其形成演化过程.FI9走滑断裂带整体为近东西走向,延伸长度60 km,表现为右行张扭性走滑断层.断裂带在平面上发育马尾构造、线性构造、斜列构造、叠覆构造,具有明显的分段特征;剖面上发育高陡线性构造、“Y”字形构造、花状构造等典型走滑构造样式.断裂带由7条主干断层组成,各断层片的规模、展布、倾向以及相互之间的连接方式等存在差异.FI9走滑断裂带在基底先存断裂的基础上,经历了3期构造叠加活动:晚震旦世-早加里东期的雏形发育阶段、晚加里东期-早海西期的强烈活动阶段以及晚二叠世的局部复活阶段.断层在元古界-下古生界中具有不同的生长模式:(1)断层由基底逐渐向上生长,上下地层断距一致或逐渐减小;(2)断层核部位于下古生界中,断层在活动期逐渐向上、下扩展,在下古生界中断距最大.

Multiple strike-slip faults have been identified in the Gaoshiti-Moxi area in the central Sichuan basin.In order to deepen the understanding of the structural geometry and kinematic characteristics of these strike-slip faults,based on deep drilling and high-precision three-dimensional seismic data in the central Sichuan basin,in this paper it describes in detail the structural geometry of the No.9 strike-slip fault zone in the Gaoshiti-Moxi area,and establishes a three-dimensional structural model of the fault.The formation and evolution process is reconstructed through structural back stripping and inversion.The No.9 strike-slip fault zone is nearly east-west trending,with an extension length of 60 km,showing a dextral transtensional fault.The fault zone develops horsetail structure,linear structure,oblique structure,and overlapping zones on the plane,with obvious segmentation characteristics.Typical strike-slip structural styles such as high-steep linear structure,‘Y’-shaped and anti‘-Y’-shaped structures,flower structures are developed on the section.The different tectonic styles developed in different strata.The fault zone is composed of 7 main faults,and the development scale,inclination and connection mode of each fault slice are different.On the basis of pre-existing basement faults,the No.9 strike-slip fault zone experienced three stages of deformations:the embryonic development stage in the Late Sinian-Early Caledonian,the main growth stage in the Late Caledonian,and the inherited extension stage of Late Permian.The faults developed different growth patterns in Proterozoic-Lower Paleozoic:(1)the fault gradually grows upward from basement,and the fault throws of the upper and lower strata is consistent or gradually reduced;(2)the fault core is located in the Lower Paleozoic,the fault gradually propagated up and down during the active period,and the fault throw of the Lower Paleozoic strata was larger than that of the underlying strata.