郯庐断裂带的两大发展阶段——广义的逆冲推覆断裂带和狭义的平移断裂带

Two development stages of the Tanlu fault zone: the stages of the overthrust fault zone sensu lato and the wrench fault zone sensu stricto

笔者总结了近年来的研究成果认为,中国东部的郯庐断裂带自海西期以来经历了两个主要发展阶段:第一阶段是广义的郯庐断裂带发展阶段,晚三叠世—早侏罗世由于扬子地块与华北地块的碰撞,成为两地块的对接边界,具有逆冲推覆的性质,属广义的特提斯构造域。第二发展阶段从早白垩世以来,发展成为一条平移断裂带,属于狭义的环太平洋构造域的平移系统。岩相古地理资料显示了扬子地块与华北地块的对接始于晚二叠世早期;印支期的郯庐断裂带是一条由NE、NNE向展布的缓‘S’型的地块拼贴边界,在现今的郯庐断裂带上表现为残留的由北北西向南南东的斜向逆冲推覆的性质,中下构造层次表现为韧性逆冲推覆变形,上部构造层即前陆褶皱冲断带内的变形;应力场分析资料显示:早三叠世晚期开始地表浅部就有近南北向的挤压作用,左行走滑平移作用开始发育;早白垩世晚期开始转入引张伸展阶段,与中国东部的伸展作用一致;新近纪又转为近东西向挤压,发育逆冲兼右行走滑作用。

The Tanlu fault zone has experienced two main development stages since the Hercynian. The first stage was a stage of the development of the Tanlu fault zone sensu lato. In the Late Triassic-Early Jurassic, the collision between the Yangtze plate and North China plate gave rise to a boundary of the two plates, which was of overthrust nature, belonging to the Tethys tectonic domain sensu lato. In the second stage, since the Early Cretaceous, the fault has developed into a wrench fault zone, which belongs to the wrench system of the circum- Pacific tectonic domain sensu stricto. Lithofacies and paleogeography shows that the junction between the Yangtze plate and North China plate was initiated in the early Late Permian and that the Indosinian Tanlu fault zone was a gendy ＂S＂-shaped block amalgamation boundary of NE and NNE trends, which displays the nature of a residual NE- and NNE-trending, oblique overthrust zone in the present Taulu fault zone, while the middle and lower tectonic layers show ductile overthnst deformation and the upper tectonic layer shows the deformation inside a foreland fold-thrust zone. Stress field analysis indicates that： as early as the late Early Triassic nearly N-S compression occurred at shaUow levels of the crust and sinistral strike-slip movement was initiated; in the late Early Cretaceous the fault zone began to turn into the extension stage, which was consistent with the extension in eastern China; and in the Neogene it underwent nearly E-W compression, resulting in thrusting and dextral strike-slip movement.