郯庐断裂带(安徽段)及邻区的动力学分析与区域构造演化

依据区域构造层次划分,采用构造筛分法,层层深入,层层筛分,确定发生于各个不同时代地层/岩层内的断裂活动的同期及叠加的应力场特征。综合所有的同期应力场特征及辅以叠加的应力场特征来验证,从而确定了一个连续的、完整的断裂活动的应力场演化序列;结合区域构造变形特征分析,阐明郯庐断裂带(安徽段)的构造演化。应力场分析显示:晚三叠-早侏罗世应力场为北北西—南南东或近南北向挤压,属古特提斯构造域,断裂发生同造山走滑;早白垩世早期,应力场为北西—南东向挤压,断裂发生左行走滑运动,中国东部处于西环太平洋构造域;早白垩世晚期—古新世(始新世),区域发生北西—南东向伸展作用,断裂处于伸展断陷作用阶段;新生代,受区域上近东西向的挤压作用影响,断裂发生挤压逆冲兼右行走滑作用。

ANALYZING ON GEODYNAMICS AND REGIONAL TECTONIC EVOLUTION OF THE TAN-LU FAULT ZONE (ANHUI SEGMENT) AND ITS ENVIRONS

According to the regional tectonic layer division and proceeding from a dynamic analysis of faults in the youngest strata, the analyses were performed layer by layer along the Tan-Lu fault zone and its environs. Through statistical analysis and calculation of striations on fault planes by means of the computer program, the paleostress state at every point was obtained, and then the state of the regional paleostress field was reconstructed. After that, the characters of paleostress fields in which fault movements occurred in different periods of time could be determined. Finally, a complete and successive evolutionary succession of the paleostress field could be determined. On that basis, and combined with an analysis of the features of regional tectonic deformation, the succession of tectonic events occurring in the Tan-Lu fault zone and its significance could be elucidated. The evolution of the regional tectonic paleostress fields since Late Triassic could be summarized as follows. A compressional stress field, striking NNW-SSE or nearly N-S, developed during Late Triassic to Early Jurassic, which related to the inner-continental orogeny and belonged to the Paleo-Tethyan regimes. A compressional stress field of NW-SE occurred during early Early Cretaceous, and resulted in the sinistral strike-slip movement of the NE-striking Tan-Lu fault, which attached to the Circum-Pacific Ocean regime. An extentional stress field of NW-SE created during middle-late stage of Early Cretaceous to Paleocene (or Eocene), a group of grabens or pull-apart basins formed along the Tan-Lu fault zone and its environs. A compression one of nearly E-W appeared in Cenozoic, which was evidenced by a series of thrusts or reversed faults developing.