中国中西部前陆冲断带运动学分类、模型与勘探领域

根据冲断系统内断层位移传递和消减的方式,将中国中西部前陆冲断带划分为4类:①Ⅰ型前陆冲断带,断层位移沿滑脱面全部传递至盆地内部,根据冲断构造规模和结构,又可分为库车型、川西南型和酒泉型3个亚类;②Ⅱ型前陆冲断带,以准噶尔盆地南缘为代表,冲断带内既存在向盆地方向传递的位移,也存在向造山带方向消减的位移;③Ⅲ型前陆冲断带,以塔西南甫沙冲断带为代表,断层位移全部沿着深部构造楔顶部的反冲断面向造山带方向消减;④复杂边界制约下的前陆冲断带,主要发育在柴西南和柴北缘,冲断系统内断层位移的传递受柴达木盆地形态和周缘边界限制,以至没有形成稳定的前陆区和前陆盆地特有的楔形沉积结构。通过中西部前陆冲断带运动学分类和复杂构造建模,提出并论证了准噶尔盆地南缘深层叠加构造楔形体、川西北寒武系倒转推覆体下的晚古生代被动陆缘层序、库车中段—东段的煤下构造以及准噶尔盆地西北缘下盘掩伏构造4个勘探新领域。

Kinematic classification, structural modeling and prospective fields of the foreland thrust belts in Midwest China

According to the distribution and transfer directions of thrust displacements under which the size, shape and pattern of thrust belt are controlled, the foreland thrust belts are classified into four types in middle and western China: (1) Type I, all the fault displacements in the thrust belt transfer from the mountain front to the basin along detachment. This type is the most popular in central and western China and can be divided into three subtypes: Kuche type, southwestern Sichuan type and Jiuquan type. (2) Type II, represented by southern Junggar Basin, in which there are fault displacements transferring to both basin and orogenic belt directions. (3) Type III, represented by Fusha thrust belt in southwestern Tarim Basin, in which all the fault displacements transfer toward the mountain front as deep structural wedges propagating toward the basin direction. (4) Type IV, represented by southwestern and northern Qaidam Basin, in which the transfer of fault displacements is restrained by the size, shape and boundary of the basin, and the stable foreland part and typical wedge sedimentary structure not produced. On basis of the above four types and the modeling of complicated structures, four new exploration areas are identified: the deep imbricate structural wedges in southern Junggar Basin, late Paleozoic passive continental margin sequence under the reverse Cambrian nappe in northwestern Sichuan, under-coal structures in middle and eastern Kuche, and footwall covered structures in northwestern Junggar Basin.