龙门山断裂带北段晚新近纪以来的右行走滑运动及其构造变换研究——以青川断裂为例

龙门山断裂带位于青藏高原东缘,构成了青藏高原和四川盆地的重要构造边界。近年来的研究表明:在新生代晚期,除了存在逆冲推覆之外,龙门山的中段和南段还发生了明显的右行走滑活动。对龙门山北段的青川断裂进行的系统研究发现:断裂具有明显的右行走滑特征,沿断裂发育大量不同规模的水系位错,其中嘉陵江水系位错规模最大,据此可确定青川断裂的最大位移量为17km。进一步的野外工作证实断裂的走滑位移在尾端发生构造变换,位于断裂南西端的轿子顶穹隆是叠加构造,吸收了青川断裂的部分位移量;位于断裂北东端的汉中盆地则是处于伸展应力环境下的断陷盆地,吸收了其大部分位移量。

Dextral strike-slip and tectonic transformation of the northern Longmen Shan fault belt from Late Neogene:A case study from the Qingchuan fault

As an eastern boundary of the Qinghai-Tibetan plateau,the Longmen Shan fault belt devided the Songpan-Ganzi orogen from the Sichuan Basin on the Yangtze Block.A Study in the latest years have indicated that the middle and south segments of the Longmen Shan fault belt experienced right lateral shearing coeval with thrusting in Late Cenozoic time.The Qingchuan fault is an embranchment of the Longmen Mountain fault belt,we have found dextral strike-slip movement of the Qingchuan fault from field survey and remote sensing in Late Cenozoic.Many streams were offset along the fault,with a maximum of dextral offset being about 17 km.The Jiaoziding dome absorbed part of the offset at the southwest terminal,and the Hanzhong Basin absorbed most of the offset at the northeast terminal of the Qingchuan fault.Combined with strike-slip activities of the main fractures in the Qinghai-Tibetan plateau,the activity age of the Qingchuan fault was discussed.Furthermore,the mechanism for dextral strike-slipping of the Longmen Shan in Late Neogene was briefly explored in the paper.