阿尔金断裂东段的构造转换模式

大型走滑断裂控制着青藏高原的变形,众多学者通过阿尔金断裂来探索青藏高原北部的构造变形过程。基于野外调查和前人的研究结果可知阿尔金断裂的滑动速率在肃北—疏勒河口段表现为三联点两侧的突降,祁连山西段的逆冲和走滑断裂吸收了阿尔金断裂的左旋位移。由于祁连山内部次级断裂活动性的增强,现存阿尔金断裂连续地表破裂终止于酒泉盆地西侧,但位于其东侧的断裂系仍属于阿尔金断裂。在Kohistan岛弧与欧亚板块碰撞之后,青藏高原沿阿尔金断裂曾发生滑动速率近一致的侧向挤出,断裂两侧此时并未发生明显的隆起。随后东昆仑造山带和祁连山造山带的先后大规模隆升,高原的北东向挤出迅速减弱。阿尔金断裂北东向挤出能力与东昆仑造山带和祁连山造山带的隆起存在明显的耦合作用。

The structural deformation pattern in the eastern segment of the Altyn Tagh fault

The large left lateral strike- slip faults are responsible for the continental deformation of the Qinghai- Tibet Plateau. Recent studies on the Altyn Tagh fault have called attention to the growth of the northern edge of the Plateau. Field survey and previous results suggest that the slip rate of the Altyn Tagh fault abruptly decreased on two sides of the triple junction from the Subei County to the Shule River. The thrust faults, strike faults in the western segment of the Qilian Mountain have absorbed the sinistral displacement of the Altyn Tagh fault, and thus the present trace disappeared in west of Jiuquan basin. But the Altyn Tagh fault had extended into the Alxa block before mid- Miocene. The Plateau began to extend laterally along the Altyn Tagh fault at the almost same slip rate after collision between the Kohistan and Eurasian plates, and there is no obvious uplift on both sides of the fault. Then, the East Kunlun and Qilian orogenic belts prominently uplifted successively, and the lateral extension of the Altyn Tagh fault rapidly decreased. Therefore, a coupling interaction exists between the extrusion of the Altyn Tagh fault and the uplift of the East Kunlun and Qilian orogenic belts.