NEW RESEARCHES ON THE TECTONIC CHARACTERISTICS OF CHINA
Huang Jiqing (T.K.Huang)
Three Precambrian paraplatf orms occur in China:Sino-Korean Paraplatf orm. Yangtze Paraplatform and Tarim Paraplatform. They are interspersed with and surrounded by Paleozoic geosynclines to form a mosaic structure in E. Asia. This was the result of the successive development of orogenic cycles: the Fuping Cycle, the Wutai Cycle, the Zhongtiao Cycle, the Yangtze ycle, cthe Caledonian Cycle, the Variscan Cycle and the Alpine Cycle (which is subdivided into the Indosinian, the Yanshanian and the Himalayan subcy-cles), while three periods of rifting systems during the Phanerozoic were present: the Xingkai rifting, the Permian rifting in S. W. China and the Cenozoic rifting in E. China.Plate tectonics dominated the Uralo-Mongolian-Okhotsk foldbelts to the north of the Sino-Korean and Tarim Paraplatforms, forming suture zones. The Karamaili-Pingdingshan-Hogenshan suture zone of Late Variscan age was the central zone, on both sides of which Early Variscan and Caledonian sutures were formed by subduction and collision, giving rise to a partially closed plate system. South of the Sino-Korean and Tarim Paraplatforms run the Qilian and Qinling Geosynclines; both appeared to be characterized by a closed system of plate motions.The Tethys-Himalayan Region was divided near the northern margin by the Longmu Co-Yushu and Jingshajiang-Changning-Shuangjiang suture zone, which separated Gondwana from Eurasia in Paleozoic times but became a suture zone by the collision of the northward drifting Gondwana in Late Permian. In Indosinian time this region was rifted widely apart along the Indus-Yarlung Zangbo line, which reclosed in Eocene time. The presence of the complicated Late Paleozoic and Meso-Cenozoic suture zones in Tibet, W. Yunnan and S. Asia indicated the closing, opening, reopening and reclo-sing of the seas separating several tectonic regions, showing a characteristic "accordion movement" of plate tectonics.The Precambrian cratons and Paleozoic foldbelts were activized during the Indosinian, Yanshanian and Himalayan Cycles. The Indosinian Cycle was the turning p~int in the formation of Gondwanaland and Eurasia. Yanshanian activization was most pronounced in E. China, while Himalayan activization dominated W. China, thus giving rise to the three tectonic domains.The polycyclic evolution of the foldbelts and other crustal structures was pronounced in China as shown by the Tianshan, Qinling, S. E. China, etc. The polycyclic plate motions in Mongolia and Tibet were particularly striking.