雪峰陆内构造系统燕山期构造变形特征和动力学

通过分析雪峰陆内构造系统燕山期褶皱-断裂的构造特征和时空演化,得出研究区雪峰山西侧构造样式具有明显的块断效应,各次级构造单元的边界断裂对构造样式具有强烈的控制作用。时序上,燕山期有两期褶皱变形,早期褶皱轴向总体为NE向,晚期褶皱轴向为S-N向或NNE向;动力学上,雪峰陆内构造系统在NW-SE向的缩短作用下,其中的雪峰山隆升带的前寒武纪基底垂向推挤隆升,且不同块体平面上表现为复杂的走滑逃逸:以怀化-新晃断裂为界,以南的块体向SW向挤出。结合古太平洋板块在燕山期的俯冲规律,古太平洋板块NW向和W向的两次俯冲可能控制了燕山期两幕褶皱和逆冲作用。

YANSHANIAN STRUCTURAL DEFORMATION AND DYNAMICS OF THE XUEFENGSHAN INTRACONTINENTAL TECTONIC SYSTEM

This paper deals with the geometry and temporal-spatial evolution of the Yanshanian faults and folds in the Xuefengshan intracontinental tectonic system. The results show that the structural pattern of the west of the Xuefengshan Mountain is obviously controlled by the blocking effect and the boundary faults between different structural units play a significant role in controlling structural styles. In general, there are two-stages of Yanshanian folding in this region. The early-stage fold extends in NE-NNE,and the late-stage fold in SN-NNE directions. Under the stress of SE-NW shortening, the Xuefengshan Precambrian basement lifted up vertically along some thrusts and escaped laterally along some strike-slip faults in a plane view. Separated by the Huaihua-Xinhuang fault, the south part of the Xuefengshan Precambrian basement escaped southwestward. Compared the subduction of the paleo-Pacific plate in the Yanshanian period with the Yanshanian deformation of the Xuefengshan intracontinental tectonic system, we can find that the northwestward and westward subduction of the paleo-Pacific plate possibly controlled the two stages of Yanshanian folding and thrusting in this region.