塔里木盆地西部吐木休克断裂带的主要特征和构造演化

塔里木盆地西部的吐木休克断裂带是中央隆起(前身是晋宁期碰撞造山带)的次级单元巴楚断隆与北部坳陷的次级单元阿瓦提凹陷之间的分界。本文以大量的地质和地球物理证据,证明它是一条内部结构复杂且切穿地壳的深断裂。结合区域构造演化恢复了断裂发育史,指出它经历过三期重大的冲断活动,分别发生在加里东期、海西期和新近纪。新近纪的冲断与巴楚断隆的南界断裂带有相同的构造样式,可分为两幕:中新世的冲断受制于南天山前陆冲断带的向南扩展,更新世的冲断主要受制于西昆仑前陆冲断带的向北扩展。吐木休克断裂带的东西走向段和北西走向段的构造特征尚有若干差异,前者在加里东期活动较强,反映了构造的继承性;北西走向段则是加里东期出现的新生构造,在海西期进一步发展,更新世时因被卷入西昆仑的前陆冲断作用,表现出强烈而复杂的变形。

Main characteristics and structural evolution of the Tumxuk fault zone in the western Tarim Basin

The Tumxuk fault zone in the western Tarim Basin is a boundary between the Bachu Fault-Uplift,a sub-order unit of the Central Rise whose predecessor was a Jinningian collisional orogen,and the Awat Sag(sub-order unit of the North Depression). A lot of geological and geophysical data demonstrated that the Tumxuk fault zone,with a very complicated internal structures,was a deep fracture cutting across the crust. To combine the regional tectonic evolution,the structural development of the fault was reconstructed,which showed three generations of thrusting once occurred during geohistory. The Caledonian thrusting in the latest Ordovician was more violent in the W-E-striking segment of the fault,with the Bachu Fault-Uplift obducted north(east)wards onto the Awat Sag,and the NW-striking structure might be a neogenic one during that time. The igneous activity along the fault recorded rifting occurred in Early-Middle Permian,then it inverted and thrust by the end of Middle Permian. The fault zone acted as a demarcation line between the depressing and uplifting regions in Juro-Cretaceous. The Neogene thrusting could be divided into two epochs. The Miocene thrusting,with the Bachu Fault-Uplift obducted southwards onto the Markit Slop,attached to southward expand of the South Tianshan foreland fold-and-thrust belt,while the Pleistocene one,with the Bachu Fault-Uplift obducted north(east)wards onto the Awat Sag,attached to northeastward expand of the West Kunlun foreland fold-and-thrust belt. The NW-striking segment showed a stronger deformation in the Pleistocene thrusting,indicated a closer relation to the West Kunlun intracontinental orogeny. The segmentation of the Tumxuk fault zone resulted mainly from development of the fault itself: the NW-striking segment,as a neogenic structure,enhanced successively in the Hercynian and Himalayan orogenies,especially in Pleistocene.