塔里木西部地区古生代断裂活动的方式和机制

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。

Active modes and mechanisms of the Paleozoic faultings in western Tarim

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 d閏ollement fold-and-thrust belt,and expanded southeastwards.The piggy-back thrusting occurred in the end of Ordovician.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 strike-slipping 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).