西昆仑山前冲断带的分段变形特征及控制因素

本文在精细地表构造地质学解析的基础上,利用塔里木油田公司在塔里木盆地西南缘完成的高分辨率地震资料、钻井资料,开展新生代构造变形的精细几何学解析,确定不同构造部位的变形几何学和运动学特征,分析不同构造部位构造变形特征的差异性及其变化规律,探讨构造变形分段性的控制因素。根据西昆仑山前冲断带的变形特征,可以将冲断带划分为5个构造段,自西北向东南分别为:乌泊尔段、苏盖特段、齐姆根段、柯东段与和田段,且各段又可分为1~4个的构造带。各段的构造样式存在较大差异,乌泊尔段表现为受主帕米尔断裂(MPT)和帕米尔北缘断裂(FPT)控制,帕米尔北缘断裂表现为地表突破和大规模的垂向位移,限定了冲断作用的往北传播,浅部发育了上新世以来的背驼盆地;苏盖特段表现为走滑逆冲作用导致的构造变形的特点,构造样式总体上靠近山前地区为堆垛构造,盆地内部为薄皮的叠瓦扇构造;齐姆根段受深部右行走滑断裂带控制,形成了向北东突出的走滑构造;柯东段则以逆冲作用为主,变形向盆地内部发生大规模的薄皮传播;和田构造段表现为南部发育高角度的铁克里克断裂及基底卷入构造,北部发育断层转折褶皱。北西向的喀什-叶城转换系统、北东向的库尔干右行压扭断裂带和齐姆根深部右行走滑断裂带、古近系的膏盐滑脱层、新近纪同构造沉积作用和乌拉根古隆起等对西昆山山前冲断带分段变形起到了重要的控制作用。

The segmentation deformation of the thrust belt in front of Western Kunlun, western China, and its controlling factors

On the basis of structural geology analysis upon the thrust belt of the West Kunlun Orogeny according to field geological investigations and high resolution seismic data and drilling data obtained from the Tarim Oilfield Company, the purpose of this paper is to determine the geometry and kinematics characteristics of Cenozoic deformation and the difference of deformation characteristics, and investigate its variation law at different tectonic unit and the control factors of segmentation. According to the deformation characteristics, the thrust belt in front of Western Kunlun can be divided into five structural segments. From west to east, they are Wupoer, Sugaite, Qimugeng, Kedong and Hotan segment, and it also can be divided into 1 to 4 structural belts from orogenic belt to basin. For the Wupoer segment, the deformation is controlled by the Main Pamir Thrust (MPT) and the Front Pamir Thrust (FPT), the Front Pamir Thrust breaks through the land surface and has large-scale vertical displacement which limits the north propagation of the Wupoer thrust belt, and a piggyback basin develops at the shallow layer since Pliocene. For the Sugaite segment, it is characterized by strike-slip thrusts in its structural deformations, and there are stacking structures near to the orogenic belt and thin skin imbricate structures inside the basin. For the Qimugeng segment, it is controlled by the deep right strike-slip fault zone, and there is a northeast prominent structure related to the strike-slip. For the Kedong segment, the deformation is mainly northward thrusting with large scale propagation to the inner basin in the style of thin skin structure. For the Hotan segment, it is composed of the Tiekelike thrust fault with a high dip angle and basement involved structure developed in its south, and a fault-bend fold in its north. The geological factors, such as the northwest-striking Kashgar-Yecheng transfer system, the northeast-striking Kuergan right strike-slip reverse fault and Qimugan right strike-slip fault in deep, the Palaeogene gypsum-salt detachment layer, the Neogene syn-tectonic sedimentation and the palaeohigh such as Wulagen etc. play a very important role in the deformation diversities of different segments.