吐哈盆地早、中侏罗世聚煤期古构造

吐哈含煤和油气盆地是地质历史演化过程中不同时代、不同性质的沉积盆地转化叠合的结果。岩相古地理分析表明，早、中侏罗世含煤岩系发育于伸展机制下的泛湖盆环境，经历了沼泽化-湖化-沼泽化-湖化过程。两次沼泽化（聚煤期）时间分别为早侏罗世八道湾期和中侏罗世西山窑期早期，两次湖泊扩张期为早侏罗世三工河期和中侏罗世西山窑期晚期。盆地基底具有受北东-南西向断裂和北西-南东向断裂控制、呈菱形断块组合的性质，同沉积期基底断块活动控制盆地古地理面貌和沉积格局。早、中侏罗世地层厚度等值线呈北东东-南西西向和北西西-南东东向交织展布，地层增厚、减薄带呈北东-南西向和北西-南东向相间排列。一般而言，两组凹陷带相交部位构成次级沉积中心，如台北凹陷西部、托克逊凹陷西部、哈密坳陷和艾维尔沟坳陷。吐哈盆地早、中侏罗世伸展作用的地球动力学背景是东天山地区后造山期应力松弛，导致造山带之间地幔物质运动激化，热扩容莫霍面上隆，使地壳上部处于引张应力状态，基底断裂以正断层位移形式造成断陷伸展，接受沉积并逐步扩展。

PALAEOTECTONICS IN THE EARLY AND MIDDLE JURASSIC COAL-FORMING PERIODS OF THE TURPAN-HAMI BASIN

The Turpan-Hami Basin, rich in coal and petroleum, was formed by superimposition of basins of different periods and different geneses in the geological history. Lithofacies palaeogeography analyses show that the Early and Middle Jurassic coal measures developed in the extensional pan-lake environments, and had experienced the swamping - lake flooding - swamping - lake flooding processes. The two swamping (coal accumulation) periods developed in the Badaowan Stage and the early Xishanyao Stage and the two lake flooding periods occurred in the Sangonghe Stage and the late Xishanyao Stage. The basement of theTurpan-Hami Basin is characterized by a rhombohedral fault block framework resulting from activities of the NE-SW and NW-SE striking faults. The palaeogeographic feature and depositional framework of the basin were controlled by synsedimentary activity of these basement blocks. The isopaches of the Jurassic extend in NEE-SWW direction and NWW-SEE direction. Thick and thin zones of the strata are horizontally alternated along both the NE-SW direction and the NW-SE direction. Depocenters such as the Taibei Sag, Toksun Sag, Hami Depression and Aiwergou Depression generally occurred in places where two subsiding zones intersected. The geodynamics of extension of the Turpan-Hami Basin in the Early and Middle Jurassic resulted from the late orogenic stress relaxation in the East Tianshan region, which promoted the activity of the upper mantle between the orogenic belts, followed by a heat-expansion and uplift of the Moho surface. The Moho dome in the Turpan-Hami Basin put the upper crust into a ten-sional stress state and made basement faults reactivate as normal faults so as to control the deposition and basin extension.