大别造山带现今构造格局的形成--来自石英C轴组构的证据

Formation of present tectonic framework in Dabie Mountains:Evidences from quartz C-axis fabrics

石英C轴组构常常记录递进变形过程中晚期增量变形的构造特征,因而可以通过对大别造山带内岩石中石英C轴组构的分析来确定造山带构造变形历史中的晚期变形事件的运动学特征。本次工作在大别造山带各单元中采集了一系列样品,对其进行石英C轴组构分析。石英C轴组构结果表明,北淮阳带就位于同造山折返第一阶段,其运动型式为上盘向NW的剪切变形;南大别高压—超高压榴辉岩带与宿松杂岩带就位于同造山折返第二阶段,运动型式表现为上盘向SE的剪切变形;北大别带就位于早白垩世穹状隆升过程中。北大别带在穹状隆升过程中表现为上盘向NW的运动型式,在深部可能存在向NW方向的下地壳物质的塑性流动。

Quartz C-axis fabrics record the tectonic characters of last deformation event in progressive deformation. Therefore, quartz C-axis fabrics from Dabie Mountains can be used to obtain kinematics of last deformation event in evolution history of Dabie Mountains. A series of samples were collected from Dabie Mountains for measuring quartz C-axis fabrics. Based on quartz C-axis fabrics, a conclusion can be drew as follows : present distribution of the North Huaiyang unit formed in the first fast exhumation with shear sense of top-to-the-NW; present distribution of the HP-UHP rocks of the South Dabie unit and the Susong complex unit formed in the second fast exhumation with shear sense of top-to-the-S; present distribution of the North Dabie complex unit formed during doming in Cretaceous. The North Dabie complex unit had shear sense of top-to-the-NW during doming and viscous flow of lower crust existed under Dabie Mountains.