下扬子区中生代走滑活动带初析

AN APPROACH TO MESOZOIC STRIKE-SLIP ACTIVE ZONE IN LOWER YANGZI REGION

沉积学特征表明，下扬子区中生代具有走滑活动带性质。控制这一走滑活动带的主要构造是位于该区中部的长江断裂带，北部以郯庐断裂为主于断裂的楔状断裂系统，以及南部以青阳广德断裂为主干断裂的马尾状断裂系统。它们在中生代均发生过左行走滑。

The depocenter of Middle-Upper Triassic,Lower-Middle Jurassic and Cretaceous sediments in Lower Yangzi Region is a sinistral echelon and has obvious sedimentary thickness gradients.The MiddleUpper Triassic Huangmaqing Group contains phengite and large amounts of apatite,which demonstrats that the area composed of Precambrian metamorphic rocks and situated at the northern side of the basin was the source area of the Huangmaqing deposits,and a significant shift from the source provenance to the despition site could be found.Both the Lujiang-Zongyang and Naming-Wuhu Mesozoic volcanic basins aness the features of pull-apart basin, and occur on strike-slip extensional fault branches of NNE striking.Two fold episodes of Middle-Late Triassic are obvious in some places but obscure in others.The above mentioned characteristics suggest that Lower Yangzi Region should belong to a Mesozoic strike-slip active zone.The main tectonics controlling the development of this zone are:1.The Yangzi fault zone;2.A wedge-like fualt system in which Tancheng-Lujiang fualt is the main body;3.A horsetail-like fualt system in which Qingyang-Guangde fualt is the main part.All of the fualts were active sinistral strike-slip during Mesozoic.