Pan Guitang

The geology of the Tibetan Plateau is interpreted within the framework of archipelago orogenesis, with the relief of the plateau owing its origin to the Neogene subduction of the Indian continental lithosphere under Tibet. Late Precambrian back-arc spreading resulted in the genesis of island arcs and back-arc basins south of the Angaran craton. A magmatic front is located at or near the position of the Kunlun Mountains. The part including and south of the Tianshan and Neimonide was separated from the Angaraland and formed microcontinents as well as numerous back-arc basins and remnant arcs in China. The Early Paleozoic basins collapsed behind the Kunlun magmatic front to form the Tianshan, Qilian, and other mountains. A part ofthe accretionary complex to the south of the Kunlun Arc was split off to form Late Paleozoic and Early Mesozoic island arcs and back-arc basins to the northeast of the Bangong/Nujiang suture. The collapse of those basins before the end of the Triassic caused the accretion of the archipelago rocks to the Cathaysian continent. A Late Paleozoic magmatic front on the northern edge of Gondwanaland was responsible for arc volcanism and back-arc spreading in Tibet. The microcontinent became separated from the rest of Gondwanaland during the Early Mesozoic when the Neotethys ocean came into existence. The northern magmatic front produced a belt of arc magmatism just south and west of the Bangong/Nujiang suture. Jurassic and Cretaceous back-arc basins were formed in northern Tibet by back-arc spreading. Those basins collapsed to form mountains before the mid-Cretaceous collision of Tibet and Cathaysia along the Bangong/Nujiang front. The Zhanbo ophiolites represent the relics of two rows of back-arc basins that came into existence as the Neotethys ocean floor was subducted under the Himalayas. Those back-arc basins collapsed in the Eocene, but the Neotethys was consumed only in the Early Miocene. The continued northward displacement of the Indian plate caused the subduction of the Indian continentallithosphere under the Himalayas and Tibet, thus causing uplift of the Tibetan Plateau.

Researches on tectonic formation,evolution and subdivision in China have had a history of more than 100 years.There are several kinds of opinions concerning the tectonic subdivision of China,which are based on different sorts of epistemology and methodology regarding the formation and evolution of the continental crust.Tectonic subdivision blueprints guided bythree mainstream tectonic viewsinclude Mr.Huang Jiqing's polycyclic tectonics,Mr.Wang Hongzhen's historical tectonics and Mr.Li Chunyu's plate tectonics.The ideas of these researchers have been playing a guiding role in this field and hence have had extensive and profound influence in China.Nowadays tectonic subdivision seems to be the key to the research on micro-structures of plates in that it is not only a theoretical problem in the study of plate tectonics but also a practical problem which must be solved immediately so as to help perform studies in such aspects as regional geology,metallogenic prognosis and mineral resources evaluation.In this paper,the tectonic subdivision is based on records of stratigraphic division and correlation,sedimentary formation,volcanics formation,intrusive magmatism,metamorphism and deformation,and consistent with the classic division theory ofthree mainstream tectonic viewsin China.Guided by theories of plate tectonics and earth dynamics,based on the requirements of metallogenic regularity and mineral energy resource prognosis,and following the main line of spatial-temporal structure analysis of tectonic facies environment of different-sized stable ancient continent block domains and different episodic orogenic systems,the authors have divided the tectonic environment of China into continent block domains and orogenic systems,which include nine first-order tectonic units and fifty-six corresponding second-order tectonic units.As there are a number of major tectonic problems in China that remain to be solved in future,a prolonged painstaking efforts are still needed for more accurate subdivision.