前陆冲断带构造分段特征——以准噶尔盆地西北缘断裂构造带为例

Characteristics of structural segmentation of foreland thrust belts—A case study of the fault belts in the northwesternmargin of Junggar Basin

前陆冲断带普遍具有构造分段的特点。横断层、侧断坡与斜断坡常是构造分段的边界 ,它们起着运动方向、变形速率、构造样式与成因机制转换的作用。准噶尔西北缘前陆冲断带是古生代晚期—中生代早期发展起来的大型冲断推覆系统 ,南自车排子 ,北至夏子街、红旗坝的大型断裂带为其冲断前锋断裂。由于形成时间、活动方式与受力条件等出现变化 ,车排子—夏子街断裂带被北西向的横断层分割为构造样式与地质结构截然不同的三段 ,南段为红山嘴—车排子断裂带 ,构成车排子断隆的东部逆冲边界 ;中段为具压扭性质的克拉玛依—百口泉断裂带 ;北段为具冲断推覆性质的乌尔禾—夏子街断裂带。中生代晚期—新生代以来该前陆冲断带被稳定埋藏 。

The foreland thrust belt has a characteristic of structural segmentation in general. The cross fault, the lateral ramp, and the oblique ramp are the familiar boundaries between the structural segments, which function as zones of transition of movement directions, of deformation rates, of structural styles, and of formation mechanism. The foreland thrust belt in the northwestern margin of Junggar Basin is a large thrust and nappe system developed from the Late Paleozoic to the early Mesozoic. The huge fault zone, beginning with the Chepaizi area in the south and extending to the Xiazijie and Hongqiba area in the north, is the thrust boundary between the whole thrust and fold system. Due to the variations in the formation period, in the deformation style, and in the acting force, the Chepaizi-Xiazijie fault belt has been subdivided into three segments with distinctive structural style and geological framework by the northwest extending cross faults. The southern segment is the Chepaizi-Hongshanzui fault zone constituting the eastern thrust boundary of the Chepaizi faulted uplift. The central segment is the Kelamay- Baikouquan fault zone with a property of transpression. The northern segment is the Wuerhe-Xiazijie fault zone presenting a typical thrust-and-fold style. The foreland thrust belt has been more or less stably buried since the late Mesozoic. The structural segmentation has moderately resulted in the petroliferous difference between these segments.