塔西南坳陷和田凹陷前陆逆冲带构造特征

TECTONIC FEATURES OF THE FORELAND OBDUCTION ZONE IN THE HETIAN SAG OF THE SOUTHWEST TARIM DEPRESSION

和田凹陷前陆逆冲带位于塔里木盆地西南坳陷东部 ,剖面上由上而下、自南而北是由推覆体、多个冲断席片叠加而成的叠加背斜双重构造体以及弱变形的原地体组成。其中 ,推覆体厚 5 0 0 0～ 70 0 0m ,东西长 2 0 5km ,南北宽 14～ 43km ,向北推覆距离为 40～10 0km ,是一与上盘生长断层有关的转折褶皱背斜 ,受和田大型台阶式滑脱断层的控制 ;推覆体侧缘发育了与边界断层平行的侧断坡、斜断坡次级断层相关褶皱背斜 ;而在其前缘 ,由于沿推覆背斜北翼的轴面发生破裂 ,产生了一系列的次级断层及相关褶皱 ;在推覆体内部 ,沿东西向轴线发生了起伏变化 ,形成了背斜圈闭。在推覆体之下 ,由东向西依次发育了弱变形的东倾斜坡、皮牙曼叠加断坡背斜型的双重构造、桑株三角带构造与叠瓦冲断带。在剖面上 ,叠瓦冲断带位于三角带构造的前缘下方 ,平面上呈重叠分布。

The foreland obduction zone of the Hetian Sag is located in the eastern of the Southwest Depression of the Tarim Basin. On the section, it consists of a superimposed anticline double tectosome overlapped by a nappe and many thrust sheets and a weakly deformed autochthon from upper to lower and from south to north. The nappe is 5000-7000m thick, 205km long from east to west and 14-43km wide from south to north. Its northward displacement distance is 40-100km. It is a hinge folded anticline related to hanging-wall growth faults, and is controlled by Hetian large-scale step-typed decollement faults. On the lateral border of the nappe, lateral and oblique fault-slope secondary fault-related folded anticlines parallel to boundary faults were developed. On the front margin of it, a series of secondary faults and related folds were generated because the axis plane along the northern limb of the nappe anticline fractured. Within the internal of the nappe, rolling changes took place along the WE-direction axis, and anticline traps were formed. Under the nappe, the weakly deformed E-inclined slope, the Piyaman sumperimposed fault-slope anticline-typed double structure, the Sangzhu triangular-zone structure and the imbricate thrust zone were developed successively from east to west. On the section, the imbricate thrust zone is situated below the front margin of the triangular-zone structure, and they are overlapping distributed on plane.