溱潼凹陷西斜坡断裂特征及形成机制

Fault Features and Formation Mechanism of West Slope in Qintong Sag

溱潼凹陷断裂发育,构造复杂,为典型的箕状断陷,横向上分为断阶带、深凹带、斜坡带;垂向上具有"上、中、下"三层结构。通过对断裂平面、剖面特征的剖析,结合板块运动、岩浆活动、构造应力分析,认为该区构造演化具有阶段性,不同期次构造运动形成的断裂具有一定的规律性,将溱潼凹陷构造演化划分为印支期板块碰撞挤压期、燕山期左行走滑挤压期、喜山Ⅰ幕左行走滑断陷期、喜山Ⅱ幕右行走滑拉伸断陷期、喜山Ⅲ幕区域抬升剥蚀期、喜山Ⅳ幕平稳坳陷期;不同期次构造运动形成的断裂相互交切,形成了现今的构造格局。

The fault development and complex structure of Qintong Sag is of typical dustpan-like fault depression,which is divided into faulted zone,deep concave zone and slope zone horizontally and into three layers of structure of"upper,middle and lower vertically.Based on the analysis of fault plane and cross-section characteristics,combined with plate movement,magmatic activity and tectonic stress,it is concluded that the tectonic evolution of this area is periodic and the formation of faults resulting from different tectonic movements are regular.The tectonic evolution of Qintong Sag is divided into the collision and compression period of Indosinian plate,the left strike-slip period of Yanshanian stage,the left strike-slip faulting stage of Himalayan Ⅰ,the right strike-slip and stretch faulting stage of Himalayan Ⅱ,the area uplift and denudation stage of Himalayan Ⅲ and the stable depression stage of HimalayanⅣ.The faults formed by different tectonic movements are intersected,which leads to the present tectonic pattern.