A DIWA ATTRIBUTION OF THE QINGHAI-XIZANG (TIBET)PLATEAU:EVIDENCE AND ANALYSIS
青藏高原大地构造性质归属地洼区的论证和分析

In terms of tectonic attribution the Qinghai-Xizang Plateau has commonly been interpreted as a geosynclinal region. Here, the Qinghai-Gansu, Northern Xizang and Southern Himalaya diwa geodepression regions, in addition to geosynclinal regions, have been recognized by Professor Chen Guoda. On the basis of recent studies, the author suggests that the Qinghai-Xizang (Tibet) Plateau during Cenozoic time was characterized by entire rapid uplifting accompanied by rapid subsidence in the surrounding regions, tectonically indicating neither a geosynclinal nor a platformal nature but a diwa attribution.The basement of the Qinghai-Xizang (Tibet) Plateau can be interpreted as a structural layer of pre-geosyncline, which later-entered a geosynclinal stage in some areas and a platform stage in other areas. During Palaeozoic -Mesozoic period, a polycyclic conversion of geosyncline and platform appeared also in some areas. Since Jurassic time, a diwa stage was initiated and developed on a structural layer of platform or geosyncline.The development of the diwa stage of the Qinghai-Xizang Plateau showed a youthening tendency from N to S in age. The entire rapid luplifting of the Qinghai-Xizang (Tibet) Plateau since Pliocene time can be considered to be equivalent to a maximum-mobility period of the diwa stage, i. e. a major plateau-forming period. The frequency of seismic activity, a variety of geo-thermal features associated with major faults, and the strong tectonic-geomo rphological contrast in the region indicate the presence of a diwa stage.On the Qinghai-Xizang (Tibet) Plateau, there extensively occur intermediate-acidic and ultrabasic-basic intrusive rocks and volcanic rocks oi the Caledonian, Variscan, Indosinian-Yanshanian, Early Yanshanian,Late Yanshanian-Early Himmalayan and Himalayan periods, respectively, in the Qilian,Kunlun-Altun, Hoh Xil-Bayan Har, Karakorum-Hengduanshan, Gangdise-Nyainqenta-nglha and Himalaya areas. These magmatic activities show a youthening tendency from N to S in age. Also, the magmatic activity during the diwa stage showed an intensifying tendency from N to S.In the light of geological evolution of the Qinghai-Xizang(Tibet)plateau, during Jurassic time the Qilian-Kunlun and Bayan Har-Western Qinling regions began to enter into a diwa stage, in which both Jurassic - Cretaceous initial-mobility and Tertiary - Middle Pleistocene maximum-mobility periods can be recognized. The northern Xizang-Sanjiang region generally entered into a diwa stage during Cretaceous time, but its southeastern part (Sanjiang area) possibly began the diwa stage at Jurassic time, the central part at the Early Cretaceous, and the western part at the Late Cretaceous. Here,a maximum-mobility period appeared during Tertiary - Middle Pleistocene time. In the Gan-gdise-Nyianqentanglha region, the diwa stage initiated during the Late Cretaceous, with both Late Cretaceous initial-mobility and Tertiary - Middle Pleistocene maximum-mobility periods recognized. Bot