南天山库车秋里塔格中段构造结变形特征和变形机理

Structural characters and deformation mechanisms of middle segment of Qiulitag anticline zone in Kuqa fold-and-thrust belt,southern Tianshan Mountain,China

本文通过遥感影像解译和地表调查,利用二维地震剖面,结合钻、测井数据,分析秋里塔格中段构造结的构造特征,利用轴面分析和多余面积方法计算构造缩短量。研究表明,秋里塔格中段构造结的构造变形受3个滑脱面,即中新统吉迪克组(N_1j)膏盐岩、古-始新统库姆格列木组(E_(1-2)km)膏盐岩和侏罗系(J)煤层控制。构造结东部发育两个滑脱面,分别位于中新统吉迪克组膏盐岩和侏罗系煤层,形成浅层的滑脱褶皱和深层的断层转折褶皱,构成复合型背斜;西部发育一个滑脱面即库姆格列木组膏盐岩,膏盐岩聚集形成南秋里塔格滑脱褶皱。库车塔吾背斜向西倾伏,背斜下伏沿吉迪克组膏盐岩和侏罗系煤层发育的断层(F_1和F_3)的滑移量向西减小,如东部A-A′剖面上断层F_3的滑移量为7.7 km,西部C-C′剖面上为3.8 km;南秋里塔格背斜向东倾伏,背斜下伏沿库姆格列木组膏盐岩发育的断层的滑移量向西增大,东部的A-A′剖面断层不发育,西部的D-D′剖面构造缩短量达5.1 km。构造结地区3个滑脱面交汇:①东、西段卷入变形的断层和褶皱在此发生了叠加干涉,②断层的滑移量在此汇合转换,③库车塔吾背斜、南秋里塔格背斜和托克拉克坦背斜在此交汇,交汇处发育多个高角度的逆冲剪切断层和表皮褶皱,形成了秋里塔格中段复杂构造结,构造结地区未发育大规模走滑断层。根据上述认识,我们提出了秋里塔格中段构造结的三维构造模型。

The Qiulitag anticline zone locates in the front of the Kuqa fold-and-thrust belt, southern Tianshan Mountain. We study the structural characters and deformation mechanisms of middle segment of Qiulitag anticline zone based on several cross sections, which integrate surface geology, seismic reflection depth profiles and well log data. There are three decollements （Jurassic coal bed,Paleocene-Eocene Kumugeliemu Fm. salt and Miocene Jidike Fm. Salt） distribute in Kuqa, which displacements raring regularly laterally in the middle segment of Qiulitag anticline zone. The displacements of the faults developped by Jidike Fm. Salt and Jurassic coal bed decrease to west, while the displacement of the fault developped by Kumugeliemu Fm is inverse. The folding styles of middle segment of Qiulitag anticline zone is controlled by the distributing area of the three decollements and their displacements. The eastern Kuchetow anticline is a detachment fold cored by Miocene Jidike Fm. Salt, which overlying a deep fault-bend fold, the fault-bend fold have a lower decollement flat located in Jurassic coal bed. The western Southern Qiulitag anticline is a detachment fold cored by Paleocene-Eocene Kumugeliemu Fm. salt. Kuchetow anticline plunge to west, Southern Qiulitag anticline plunge to east, so the two antclines plunge with their underlying faults individually. As a result, as （1）the eastern part and western part of Qiulitag anticline zone involved in deformed strara, （2）the displacements of the three decollements converge and transform,and （3）Kuchetow anticline, Southern Qiulitag anticline and Tuokelaketan anticline converge in middle segment of Qiulitag anticline zone,so the deformation of middle segment of Qiulitag anticline zone is complex. Based on study results,a 3-D model is proposed to illustrate the deformed mechanism of middle segment of Qiulitag anticline zone.