塔里木盆地中部阿—满低梁带断裂构造分析

Analysis on the faults of Awati-Manjiaer lower ridge,central Tarim Basin,NW China

塔里木盆地北部坳陷中部存在一个北东—南西方向的下古生界的(鞍状)低梁带(阿—满低梁带)。它是阿瓦提凹陷和满加尔凹陷之间的天然分界,以此低梁带的脊线划分出两个凹陷。以三维地震资料解释为依据,本文研究了阿—满低梁带的断裂构造特征。研究区主要发育4期断裂构造:1)南华纪—奥陶纪的正断层与罗迪尼亚超大陆的裂解有关,并可进一步划分为南华纪—震旦纪和寒武纪—奥陶纪两个断裂活动阶段。南华纪—震旦纪正断层的成因是罗迪尼亚超大陆的裂解作用,形成堑垒构造;寒武纪—奥陶纪正断层的成因是塔里木自罗迪尼亚超大陆裂解出来后,游离于古特提斯洋所处的区域性弱伸展构造背景,形成负花状构造。2)晚奥陶世—中志留世断层包括晚奥陶世—志留纪初的滑脱—冲断构造和早-中志留世的挤压走滑断裂,形成断层传播褶皱和正花状构造。其形成的动力来源是昆仑加里东碰撞造山作用。3)晚志留世—石炭纪正断层是昆仑加里东碰撞造山后构造应力松弛阶段的产物,形成典型的负花状构造,组合成雁列状张扭性断层带。4)二叠纪正断层是大陆裂谷作用的结果,往往受相关岩浆作用的改造。剖面上形成堑垒构造和负花状构造,平面上组合成雁列状张扭性断层带。二叠纪断裂与晚志留世—石炭纪的断裂可能有继承关系。

There is a NE-SW extend saddle-shaped lower ridge between Awati and Manjiaer sags, central Tarim Basin. It is proposed as the separate boundary between these two sags. The faults of this ridge are studied on the basis of 3D seismic data interpretation. The faults development in the ridge are classified into 4 stages ： 1 ） Nanhua-Ordovician normal faults are related to the breakup of Rodinia supercontinent, and can be further divided into 2 sub-stages, Nanhua- Sinian and Cambrian-Ordovician. Nanhua-Sinian normal faults directly related to the breakup of Rodinia, forming graben-horst structures. Cambrian-Ordovician normal fault were formed under the gentle extensional background of Tarim wandering in paleo-Tethys. These faults usually form negative flower structure. 2）Terminal Ordovician-Middle Silurian faults composed of terminal Ordovician-beginning Silurian detachment-thrust faults and compressive strike slip faults, forming fault-propagation fold and flower structure. The faults of this stage is related to the Kunlun Caledonian collisional orogeny. 3） Late Silurian-Carboniferous normal faults form typical negative flower-structure and usually group into transtensional fault zones. The formation of this stage normal fault is associated with the stress relaxation after Kunlun Caledonian collisional orogeny. 4 ）Permian normal faults were formed under the continental-rifting background of Tarim, and often deformed by the rift-related magmation. Permian normal faults usually group into graben-horst structure and negative flower structure, and form transtensional fault zones. Some Permian faults may inherit the Late Silurian-Carboniferous faults.