西昆仑山前冲断带断裂特征及构造单元划分

Fault characteristics and division of tectonic units of the thrust belt in the front of the West Kunlun Mountains

受新生代帕米尔构造结大幅度向北推移、旋转的影响,形成了弧形的西昆仑山前冲断带。本文主要通过野外地质调查、地震反射剖面的精细解释,对西昆仑山前冲断带最基本的组成部分-断裂进行系统研究。西昆仑山前冲断带内以发育与其弧形形态一致的逆冲断裂为主,但弧形冲断带中段的断裂具有挤压逆冲的同时兼有右行走滑性质。冲断带内还发育了NE向和近EW向的走滑断裂,它们的发育时间和成因不尽相同,它们控制了冲断带内的变形,调节和改造了早期形成的构造。在对断裂系统研究的基础上,结合冲断带各个部位的结构特征和变形时间,将冲断带划分为9个次级构造单元。西昆仑山前冲断带开始发育于中新世中晚期,此后经历了上新世早期、上新世中晚期、早更新世早中期以及早更新世晚期四个演化阶段。

The arc-shaped thrust belt in the from of West Kunlun Mountains formed in Cenozoic with the northward thrust and lateral rotation of Pamir syntax. We here present our new field investigation and seismic profile interpretation data to study the fault system, which provides the basis to understand the complex arc-shaped foreland thrust belt. The results indicate that the thrust belt mainly consists of thrust faults with consistent striking to the arc shape Of the thrust belt, but in the middle portion occur some thrust fault holding dextral strike-slip component. Also occur NE-SW and E-W trending strike-slip faults, which differs in their active timing and mechanisms. These NE-SW and E-W trending faults control the deformation of the thrust belt and accommodate and reconstruct previous existing structures. Based on the study of fault system, determination of deformation time and structural characteristics of different portions, the arc-shaped thrust belt has been divided into 9 tectonic units. After formed in Middle-Late Miocene, the thrust belt experienced four evolution stages： Early Pliocene, Middle-Late Pliocene, early-middle Early Pleistocene and late Early Pleistocene.