塔里木西部地区古生代断裂活动的方式和机制

Active modes and mechanisms of the Paleozoic faultings in western Tarim

基于系统的地震剖面解释及其与塔中地区的对比,本文探讨了塔里木西部地区古生代断裂活动的方式和机制。玛东断裂带是一条宽阔的北东向盖层滑脱型褶皱冲断带,前展式向东南扩展,冲断作用发生在奥陶纪末。巴东断裂(吐土休克Ⅱ号断裂)为北西向基底卷入型冲断带,奥陶纪末和中二叠世末发生冲断。巴西断裂和塔参2井南断裂是海西期的正断层。塔里木古板块古生代的发育受邻侧的造山带演化制约,近东西向和北东向断裂奥陶纪末的冲断是继承基底构造发育的。塔中地区的近北西向断裂是晚寒武世的新生断裂,加里东运动可分为两幕:奥陶纪末的冲断(艾比湖运动)和晚志留-中泥盆世的冲断—走滑,后者向西明显减弱。塔里木西部的部分北西向断裂(如康西断裂)可归入塔中北西向断裂系。北东向的玛东断裂带是其西的向北(东)冲断的吐木休克断裂带与其东的向南偏东冲断的塔中8-1井—塔中5井断裂带之间的调节断层。

Based on systematic interpretation of seismic profiles and a comparative study to central area of the Tarim Basin, the active modes and mechanisms of the Paleozoic faultings in western Tarim were explored in the paper. The NE-striking Madong（Badongnan） fault zone, as a part of southeastern boundary of the Bachu Fault-Uplift, was a superficial decollement fold-and-thrust belt, and expanded southeastwards. The piggy-back thrusting occurred in the end of Ordoviclan. The NW-striking Badong fracture（or the No. 2 Tumxuk fracture）, the eastern boundary of the Bachu Fault-Uplift, was a basement-involved thrust, with the thrusting occurring in the ends of Ordovician and Middle Permian respectively. The Baxi and South of Well Tacan 2 fractures in north part of the Markit Slope were Hercynian normal faults. The Paleozoic development of the Tarim paleo-plate was constrained by the neighbouring orogenic evolution. The thrusting of nearly W-E and NE-striking fractures in early Caledonian, related to subduction of the West Kunlun ocean, might inherit the basement structures. The NW-striking fractures in central Tarim was neogenic in Late Cambrian, in which two episodes of Caledonian deformation could be recognized ： the early thrusting in the end of Ordovician and late thrusting and strikeslipping during Late Silurian to Middle Devonian. The later deformation should be resulted from the activation of the Paleo-Altun shearing orogen, so as to obviously become weeker westwards. Some NW-striking fractures in west Tarim, for example, the Kangxi fracture, attached to the Tazhong（ central Tarim）NW-striking fracture system. The NE-striking Madong fault zone was a transfer fault between the Tumxuk fault zone（thrusting towards the north to east）and the Wells Tazhong 8-1 and Tazhong 5 fault zone（thrusting towards the south to east）.