塔里木盆地中央地区的断裂系统：几何学、运动学和动力学背景

Fault systems in central area of the Tarim Basin:geometry,kinematics and dynamic settings

塔中低凸起位于塔里木盆地中央隆起的中段,发育4组不同方向的断裂,以北西向的塔中Ⅰ号断裂带为主干断裂,其南的近北西向断裂和近东西向断裂与之组成"入"字形构造,向西撒开;剖面上则因塔中Ⅰ号断裂带活动强度自东向西减弱而出现不同的断裂组合样式。基于地层记录和区域演化分析了该区断裂系统的活动时期和活动方式,两次重大的挤压—剪切事件分别发生在奥陶纪末和晚志留-中泥盆世,因而塔里木盆地中央隆起可能是晋宁期山体在后期重新活动形成的加里东期陆内造山带。北西向断裂是二叠纪岩浆侵入或玄武岩喷溢的通道,之后全区断裂基本处于平静状态。结合塔里木周边造山带的演化,认为古生代—三叠纪时塔中地区的盆地发育主要受西昆仑造山带演化制约,同时叠加有古阿尔金剪切造山带的影响,这是为塔中地区特殊的构造位置决定的。侏罗纪—新近纪,该地的盆地主要与阿尔金断裂的剪切造山作用耦合发育,仅早白垩世时与塔北—库车地区同属南天山的"盆""山"系统。断裂的运动学特征取决于其动力学背景,实际上受制于邻侧的造山带发育。断裂系统的发育是塔中地区能形成复式油气田的关键条件之一,本文的研究对推进复式油气成藏的机理研究、明确近期的重点勘探靶区等有积极意义。

There developed four groups of fault with varied orientations in the Central Tarim Lower Uplift, the middle segment of the Central Rise of Tarim Basin. The NW-striking Central Tarim （Tazhong） No. 1 fault zone was a mainstay of the fault systems, with the NW- and WE-striking faults south of it making up a westward opened λ-shaped structure. The activation intensity of the Central Tarim No. 1 fault zone became weakened westwards, so as to appear different faultcombination patterns sectionally. Based on the stratigraphic records and regional tectonic evolution, the periods and modes of the fauhings were analysed. Two main compression-shearing events occurred in the latest Ordovician and Late Silurian-Middle Devonian respectively, which meant that the Central Rise of Tarim Basin might be a Caledonian intracontinental orogen resulted from reactivation of the Jinningian mountain chains. The NW-striking fractures were pathways of magmatic intrusion or basaltic eruption in Permian, and afterwards all the fault systems in the area seemed unmobile, only except the Madong No. 3 fault. The peri-basinal orogenic evolutions were briefly described. The basin developing in central Tarim area during Paleozoic and Triassic might be mainly constrained by the West Kunlun orogenesis, and subordinately cocontrolled by the Paleo-Ahun shearing orogenesis, which was decided by its unique tectonic position of the area. The basin developing of the area during Jurassic-Neogene might be coupled with the shearing orogeny of the Altun fault, only in Early Cretaceous the area, together with the northern Tarim and Kuqa areas, attached to the South Tienshan basin-orogen system. To sum up, the kinematic features of the fault systems were decided by their dynamic settings, which, in fact, depended on the neighbouring orogenic occurring. The fault system was one of key condition for the composite hydrocarbon accumulation play in central Tarim area, and this study would promote the research on mechanism of the composite accumulation and pointed out the target regions of oil-gas exploration in the near future.