右江地区新生代走滑断裂活动特征及其构造意义

Characteristics and Tectonic Significance of Cenozoic Strike-slip Faults in Youjiang Region

右江地区位于华南、川滇和印支三个活动块体的结合部位,新生代该区发育一系列北西向左旋走滑断裂及伴生盆地。这些断裂近等间距分布,将右江地区分割成多个长条形区间,断裂活动又导致各区间相互发生左行运动。根据这些断裂的走滑错移量以及伴生盆地的拉分量,计算获得区域应变和动力学涡度。研究结果表明右江地区在新生代整体发生无旋转的简单剪切变形,其最大主张应变为近南北向。新生代以来,右江地区先后受到印支块体和川滇块体侧向挤出的影响,右江地区的单剪变形和区内的北西向断裂活动正是这两个块体共同作用的结果,同时也是印度–欧亚板块碰撞产生的连锁反应之一。

The Youjing area is in the southwestern most portion of the South China Block,bordering the Indochina Block on the southwest and the Xichuan-Yunnan Block on the northwest.A set of NW-striking transcurrent faults,as well as their associated basins,formed in the area during the Cenozoic.They are approximately evenly spaced and left-lateral.Strain and vorticity analyses of these faults indicate that the study area has undergone irrotational simple-shear deformation,where the maximum principal strain axis has a nearly north direction,as a whole.This deformation mode is likely resulted from the southeastward extrusion of the Indochina Block and the Xichuan-Yunnan Block in response to the Cenozoic India-Eurasia collision.