库车坳陷克拉苏构造带的反转构造及其形成机制

库车坳陷克拉苏构造带发育复杂的褶皱冲断构造，尤其是盐下层构造变形强烈，具有反转构造的变形特征。克拉苏构造带反转构造在剖面上具有先存正断层重新活动并在断层下盘形成捷径断层的特征，在南部远离反转断层处具有盖层滑脱性质，据此可将克拉苏构造带划分为反转断隆背斜带、楔状叠瓦构造带和逆冲前缘构造带3个次级构造带；平面上构造反转程度西弱东强，西段主要表现为在反转断层下盘形成分支断层，而东段具有在反转断层上盘形成反向断层和褶皱变形的趋势。构造变形分析表明，南天山水平挤压叠加垂直剪切的作用导致克拉苏构造带发育基底卷入的高角度逆断层，并使部分早期正断层重新活动而形成反转构造。对次级构造带构造圈闭有效性的分析表明，反转断隆背斜带形成规模大、产状平缓的构造圈闭，但是上覆盐岩层厚度较薄，天然气容易散失；楔状叠瓦构造带形成规模相对较小、幅度大的构造圈闭，上覆盐岩层厚度大，有利于天然气的保存。

Inversion structure of Kelasu structure zone in Kuqa Depression and its formation mechanism

The complicated fold-thrust belt is developed in the Kelasu structure zone of Kuqa Depression. The structural deformation of subsalt strata is more intensive and has the deformation features of inversion structure. According to the geologic section, the inversion structure of the Kelasu structure zone has the reactivation property of precursor normal fault and shortcut fault formed on the footwall. In the position far from the reactivated fault of the south part, the decollement of cover probably occurred. The Kelasu structure zone can be divided into three secondary belts including the inversion faulted anticline belt, wedge-like imbricate belt and thrust front belt. On the footwall of reactivated fault, the branch fault was developed in the west part of the Kelasu structure zone more than in the east part. In the latter back, the thrust and folding were generated on the hanging wall of reactivated fault. The horizontal compression and vertical shear of Southern Tianshan resulted in the basement-involved high-angle thrusts and the reactivation of some normal faults, which makes generation of inversion structure. In the inversion faulted anticline belt, the large-scale and plane structural traps with the thin superposition salt layers were developed, and natural gas easily disappeared in the superposition salt layers. In the wedge-like imbricate belt, the small-scale and large-attribution structural traps with the thick superposition salt layers were developed, which is favorable for preservation of natural gas.