摘要
中国西部中新生代大型大陆扩张盆地相当发育,可分为内陆扩张盆地和弧后扩张盆地。这两种盆地的形成和演化与相邻大洋板块俯冲机制密切相关。晚二叠世以来,中国发生过三次与大洋板块俯冲相关的陆块碰撞和一次显著的板间陆壳俯冲。中国中新生代造山运动主要是由大陆扩张盆地和大洋扩张盆地的扩张作用引起的,因此存在两种造山运动的基本类型。中国中新生代大陆壳厚度颇不均匀,增厚是通过叠冲和传递挤压方式实现的;减薄是凭借拉伸和传递扩张方式进行的。
West China has been pieced with the following Palaeozoic-Triassicplates and terranes, the Siberian Plate, the Kazakhstanian Plate, theTarim-Sinokorean Plate composed of the Tarim, Qaidam, Alxa, Helan-Liupan and North China terranes, the South China-Southeast Asia Platemade of the Changning-Menglian, Shuangjiang-Lancang, Changdu andYangtze terranes in the west part of the plate, the Zangbei(North Tibet)-Dianxi (West Yunnan) Microplate containing the Karakorum, Lhasa,Gangmacuo, Tengchong and Baoshan terranes and the Indian Plate. Great Meso-Cenozoic continental spreading basins of West China areconsiderably developmental. They can be divided into inland spreadingbasins including the Junggar, Tarim and Qaidam basins and back-arcspreading basins containing the Bayan Har, Tanggula, Changdu, Lanping-Simao and Zangbei basins. The basins are closely related with the sub-duction mechanism of the adjacent ocean. Since Late Permian the main geological events, which occurred inChina, comprise three times of continental block collisions including sub-duction of the allied ocean plate in company with the development ofcontinental spreading basins and a time of interplate continental crustsubduction. The Cathaysian Collision Period from Late Permian to LateTriassic, in which the Tarim-Sinokorean Plate and the South China-Southeast Asia Plate split from Pacifica came into the collision withthe Angara old land, forming the Eurasian Plate and accompanied bythe transformation from the Paleotethys Ocean into the Mesotethys Ocean,take the general layout of the Meso-Cenozoic tectonic evolusion of China.The Zangbei Collision Period from Late Triassic to Early Cretaceous: ischaracterized by the subduction of the Mesotethys Ocean Plate, the clo- sure of the Mesotethys Ocean and the collision of the Zangbei-DianxiMicroplate divided from Gondwana with the Eurasian Plate. The Zangnan(South Tibet) Collision Period from Late Triassic to Middle Eocene,in which the Indian Plate is connected with the Eurasian Plate, is markedby the closure of the Newtethys Ocean and an intensive orogenic movementshowing an extensive unconformity. Since Late Eocene the north part ofthe Indian Plate subduces northwards under the Eurasian Plate by meansof a wide zone of imbricate thrust faults, exhibiting a kind of interplatecontinental crust subduction. There are two principal types of the Meso-Cenozoic orogeny of China:I. A Continental Spreading Basin Orogeny and 2.An Ocean SpreadingBasin Orogeny divided into two subtypes, a Continental Collision Orogenyincluding ocean plate subduction and continental block collision and anInterplate Continental Crust Subduction Orogeny. The thickness of thecontinental crust of China is very uneven because of secondary thickeningand thinning. There are two thickening ways of the continental crust:1. A lmbricate Thrust Thickening, in which the crust is thickened by aseries of imbricate thrust faults overlapped thrustedly each other, distribu-ting along continental crust subduction zones of intraplate andinterplate; 2. A Transmission-squeeze Thickening, in which the crust ma-terial is eroded and carried to mountain roots at margins of spreadingbasins by the secondary mantle convections. The crust is thinned with twoways: 1. A Pull-Extension Thinning, in which the crust is thinned bymeans of normal fault systems; 2. A Transmission Spreading Thinning,in which the crust is thinned by the secondary mantle convectioas trans-miting basin materials to margins of spreading basins.
