基于高精度航空磁测的塔西南坳陷深部地质构造研究

由于受地表沙漠和巨厚新生界覆盖,塔里木盆地西南部开展的基础地质调查较少,特别是对深部地质结构认识还比较模糊。笔者根据近年来在塔西南实测的高精度无人机航空磁测数据资料,对塔西南的地质构造、磁性基底隆坳格局、构造格架等较模糊的地质问题进行了深入研究。本文应用三维欧拉反褶积反演方法计算磁性基底深度显示,在伽师北部存在一近东西向的凹陷带,在磁性基底- 10 km等深线上前陆中部坳陷带自西向东展现出由喀什凹陷、英吉沙凸起等9个凹陷和凸起相间构成,凸起或凹陷受基底断裂控制,凹陷内存在多个局部洼陷中心具逆冲推覆断裂前缘局部洼陷构造规律。根据基底深度差异,提出前陆中部凹陷与麦盖提斜坡西段之间基底断裂构造边界认识,中新生界下伏的基性火山岩主要分布在岳普湖-色力布亚和叶城南部,其形成受近东西、北东向深断裂控制等地质认识。研究成果对塔西南深坳盆地的深部地质构造研究及深层油气调查具有一定的指导意义。

Some understanding of the deep geological structure in Southwest Tarim Basin based on high-precision aeromagnetic survey

Limited by surface desert and thick Cenozoic cover, few basic geological surveys have been carried out in southwest Tarim Basin, thus the understanding of deep geological structure beneath this area remains poor. To fill this gap, based on the high-precision and large-scale aeromagnetic survey data of recent years, this work attempts to address some geological issues such as the geological structure, the uplift and depression pattern of magnetic basement, and the tectonic framework in this area. The three-dimensional Euler deconvolution inversion method was used to calculate the depth of magnetic basement. The result shows that there is a nearly EW-trending depression belt in the north of Jiashi. On the -10 km isobath of the magnetic basement, the central foreland depression is composed of nine depressions and uplifts alternately, such as the Kashi depression and Yingjisha uplift. The uplift or depression is controlled by basement faults, and there are many local sags in the depression. There are several local sags with thrust nappe fault front features in the depression. According to the difference of basement depth, a new structural boundary between the central depression of foreland and the western section of the Maigaiti slope was defined. The basic volcanic rocks underlying Mesozoic and Cenozoic are mainly distributed in the Yuepu Lake-Selibuya and the south of Yecheng, and their formation is controlled by deep nearly EW- and NE-trending faults. All these results have certain guiding significance for further research of the deep geological structure and surveys to oil and gas at depth in the southwest Tarim Basin.