皖南地区加里东运动构造特征

前人认为皖南地区加里东运动仅表现为抬升造陆运动.文中从构造运动不整合接触关系证据、盖层构造、劈理及变形变质程度,以及古构造应力场特征等方面开展研究.于皖南地区多处发现了上泥盆统与下伏志留系呈角度不整合接触,表明了区内发育加里东褶皱.通过区域地质调查和构造解剖,揭示了区内复式褶皱为加里东和印支两期褶皱叠加的产物.其中,加里东期构造样式主要为区域性开阔褶皱,规模巨大,其轴迹呈北东东向或近东西向延伸,然而,印支期构造样式为线性中常褶皱,规模较小,其轴迹主要呈北东向展布.应用赤平极射投影法对研究区内的褶皱轴面产状、劈理产状要素进行统计分析,结果显示发育加里东期、印支期等多期变形构造;并利用该法求得褶皱两翼优势产状,应用数学计算法计算出区内3期构造应力场特征值,显示华南地块自南而北向扬子地块俯冲挤压的陆内造山动力学过程.早古生代盖层造山属性为陆内造山.区内加里东期褶皱构造属性的厘定和深入研究,对区域构造格架的建立具有重要意义.

Tectonic characteristics of the Caledonian orogeny in the southern Anhui

Previous research thought that the expression of the Caledonian tectonic movement that only uplift to a peirogenetic movement in the southern Anhui. In this paper, this study provided evidence of the tectonic movement interface features, caprock structural characteristics, cleavage structures characteristics, deformation metamorphic grade and fracture feature, ancient tectonic stress field. An angle unconformity contact was found between the upper Devonian Wutong Formation and the Silurian of it’s underlying strata. It indicates that main development Caledonian fold structures in the caprock in the southern Anhui. Though regional geological surveys and tectonic anatomy, it is revealed that the complex folds in the region are the product of the superposition of both the Caledonian and Indosinian folds. Among them, the Caledonian structural styles are mainly regional open folds, large scale, its axis is extending near EW direction or NEE direction. However the Indosinian structural styles are linear-medium folds. It is smaller scale, and its axis direction extends to the NE. Hemispherical projection method was applied to analyze attitude of axial surfaces of folds and attitude of cleavages, the results showed that it development the deformation structure of the phase of Caledonian, Indosinian and so on, and the advantages of the two wings of the folds are obtained by this method. Thus, it is caculated by athematical method that the characteristic value of three periods of tectonic stress field in the study area, and these show the dynamic process of intracontinental orogeny in South China from south to north to Yangtze. So, the Early Paleozoic orogeny is all belong to intracontinental orogenesis. The Caledonian fold is determined and researched on its tectonic characteristics and evolution in the study area, it is important to establish the regional tectonic framework.