扬子板块北缘中段前陆带构造变形特征及意义

扬子板块北缘中段前陆褶皱逆冲带在中生代经历了多期的构造叠加和改造,其复杂的构造样式记录了早期扬子板块与秦岭-大别微板块拼贴碰撞作用以及晚期转入的陆内变形过程。本文在前人研究的基础上通过对扬子板块北缘中段保康-房县地区前陆带构造变形样式及运动学特征的分析,划分出扬子板块北缘前陆褶皱逆冲带的根部、前锋及其内部次级的逆冲推覆构造单元,同时识别出一条过保康-神农架-蒲溪一带近东西走向的左行走滑剪切带,分析表明该左行走滑带形成于扬子板块北缘全面转入陆内变形之后、大巴山大规模向南西逆冲推覆运动之前的中侏罗世到晚侏罗世期间。该左行走滑剪切带对扬子板块相对于华北板块发生顺时针旋转的过程起到了调节作用,对于扬子板块北缘中生代构造演化具有重要意义。

Structural style and tectonic significance of foreland belt in the middle segment of northern Yangtze plate

The foreland fold-and-thrust belt developed in the middle segment of northern Yangtze plate underwent many periods of structural superpose and reformation,whose complex structural deformation distinctly records the process of collision and subduction between the Yangtze plate and Qingling-Dabie micro-plate in Mesozoic and the later tectonic evolution after transforming into intracontinental deformation.Based on the analysis of the structural deformation styles and kinematic characteristics in the middle segment of northern Yangtze plate,Baokan-Fangxian area,this paper assures the specific location of the front of the foreland fold-and-thrust belt in the northern Yangtze plate and the features of the thrust and napping tectonics,which developed at the later stage,and also identifies a sinistral strike slip fault running through the region of Baokang,Fangxian and Puxi.At the same time,the analysis shows that the strike slip fault played a regulating role in the process of Yangtze plate clockwise rotation relatively to the north China plate after the period of Middle-Jurassic,which is vital to understand the tectonic evolution of the northern Yangtze plate in Mesozoic.