摘要
天山地区的板块活动可以追溯到中晚元古代。天山陆壳的基底可分为三种类型,中天山的花岗——变质岩层基底形成于早元古代末;南天山及塔里木北部的基底形成于晚元古代;北天山及准噶尔的基底大致与中天山相同。从震旦纪至二叠纪、天山的板块活动以手风琴式张、合为特征,经历了七次张、合旋回。板块活动的挤压缝合带与扩张带相对应,在时间上,它们“此张彼合”;在空间上,互相对偶,分别存在于板块的对侧。天山(及邻区)陆块与相邻褶皱带的空间关系,不是陆核与边缘褶带的增生关系。天山陆壳是由不同时代的褶皱带及其间的苦干地块坩成的镶嵌构造区。板块张、合所产生的褶皱带及蛇绿岩带,大致以中天山为轴,向南、北方向交错排列。
The plate activity in Tianshan can be traced back to Middle and Late proterozoic. The basement of Tianshan continent can be divided into three types, the middle formed in the end of Proterozoic, and the south (incleding north Tarim) formed in Late Proterozoic, whereas the north( including Junger) is nearly the same as that in the middle Tianshan. From the Sinan to the Permian the plate activity in Tianshan is characterized by accordion movement. This area once underwent opening and closing for seven times. A suture at one side of the plate is always connected with a tension belt in another side. When the suture was closing, therelated tension belt must be opening at the same time. So they are conjugated in the epposite sides of the plate. The spatial distribution relation of the continent block and its adjacent folded belts in Tianshan area is not accretion relation as in Siberian plate. The Tianshan continent block is a mosaic tectonic area made of several different folded belts and some smaller blocks between them. These folded belts were resulted from the opening and closing of plate, and arranged alternately on both sides of the early Caledonian folded belt in the middle Tianshan. For a folded belt an opening-closing is only one cycle or stage, but for the whole Tianshan area from the Sinian to the Permian several times of opening and classing had made the Tianshan continent block be in motion continuously. The disfanees of block openings in Tianshan had gradually diminished from the Sinian to Permian, If, taking 0.5-1.5cm/y as a rate of block opening, the Early Caleaonian eugeosyncline between the middle Tianshan and southern Hasakstan, would have reached a width of 1000-3000km 500-1500km for the Junger-Beishan Caledonian eugeosyncline, 250—750km for the late Caledonian eugeosyncline in the south Tianshan, 150—450km for the middle Variscan one in the north Tianshan, and 50—150km for late Variscan one in the southern Beishan. Every change in direction of plate oscillation had resulted a openingclosing cycle, so the folded belts are records of change in direction of plate motion during the Sinian to Permian. That is why the cycle of folded belt motion thand the continuity of Plate motion are considered as of dialectic accordance. Tension belt, pressure belt and shear belt are the three elements of plate motion in Tianshan. The front margin of moving plate is a pressure belt, its back margin is Usually a tension belt, and the sides will be shear belts, when the direction of a moving plate changes, its front margin translates into back one, and so are pressure belt and tension belt. This is the pattern of plate motion in Tianshan. The authors we consider that the above-mentioned pattern will be applicable for other plates, for example; the north China plate and the north America plate, in elementary characteristics.
