塔里木盆地玉北地区断裂构造差异变形及其控制因素

Differential Deformation and Control Mechanism of Fault Structures in Yubei Area of Tarim Basin

为揭示断裂构造差异变形特征及其成因机制,在二维和三维地震资料精细断裂解释的基础上,对塔里木盆地玉北地区断裂构造分层、分期和分区发育强度差异性进行了研究。结果表明:纵向上,断裂可以分为以逆冲构造为主的盐下基底构造、以盖层滑脱为主的盐上下古生界、以断层相关褶皱为主的上古生界和新生界4个构造层,自盐上下古生界至新生界构造变形总体逐渐减弱;平面上,玉北地区东部断裂活动更为强烈,以叠瓦冲断构造为主,次级断裂更为发育,密集分布,而玉北地区中西部冲断作用较弱,以逆冲滑脱、高角度逆冲构造为主,次级断裂不太发育,相对分散分布;断裂演化时间上,加里东中期玉北地区东部断裂活动强,中西部断裂活动较弱,加里东晚期—海西早期、海西晚期东部断裂相对稳定,中西部断裂活动相对较强,反映断裂活动自东向西的迁移特征;断裂构造发育位置、走向和分布受先存基底构造、构造应力场背景和膏盐岩滑脱层等共同控制;加里东中期断裂主要密集发育于先存基底构造薄弱带,受SE向挤压应力控制,断裂沿中、下寒武统由NW向朝SE向被动逆冲,形成多排NE向差异分布的逆冲断裂带。

In order to reveal the differential deformation and control mechanism of fault,the 2D and 3D seismic profiles were detailed analyzed, and the variances of layering, staging and developing intensity of fault structure were carefully studied in Yubei area of Tarim Basin.The results show that in the vertical,the fault structure can be divided into 4 structure layers, including pre-salt basal structure mainly with thrust structure,post-salt Lower Paleozoic mainly with cover detachment,Upper Paleozoic and Cenozoic mainly with fault-related fold,and the structural deformation gradually becomes weaker from post-salt Lower Paleozoic to Cenozoic;in the plane,fault activity in the eastern of Yubei area is strong mainly with nappe thrust structure, and secondary faults develop much better and intensively,while thrusting in the central-western of Yubei area is weak mainly with thrust-decollement and high-angle thrust structures,and secondary faults develop poorly and dispersively; for the evolution time of fault, Middle Caledonian is the strongest period of fault activity in the eastern of Yubei area while weakest in the central-western,and Late Caledonian-Early Hercynian and Late Hercynian are the stable periods of fault activity in the eastern while relatively strong in the central-western, and Himalayan is the weakest period of fault activity as a whole,so that the fault activities migrate from the eastern to the western;development position,direction and distribution of fault structures are controlled by pre-existing basement structure,tectonic stress field setting and gypsum-salt detachment layer;faults develop intensively in the weak zone of pre-existing basement structure and are controlled by SE-trending extrusion stress,and faults passively thrust from NW to SE along the Lower-Middle Cambrian and form thrusting fault zone with the differential distribution of multiple NE-trending.