Lithospheric removal and destruction of the North China Craton have been hotly discussed recently. It has been confirmed that the timing of a strong lithospheric removal took place in Late Mesozoic; however, little is known about when the lithospheric removal was initiated and how the Late Permian to Early Triassic deep subduction of Yangtze continental crust affected the cratonic destruction. This paper presents an overview on the temporal and spatial framework and geochemical characteristics of the Triassic intrusive rocks in the eastern North China Craton and use these data to trace their sources and petrogenetic processes, in order to constrain the tectonic setting in which they evolved. It is concluded that the destruction of the North China Craton was initiated in the Late Triassic and induced by delamination of the thickened continental crust by deep subduction of Yangtze continental crust and continent-continent collision. This suggests that the subduction of the continental crust and continent-continent collision are possibly interpreted as the inducement of Late Mesozoic decratonization of the North China Craton.
The studies of continental deep subduction and ultrahigh-pressure metamorphism have not only promoted the development of solid earth science in China, but also provided an excellent opportunity to advance the plate tectonics theory. In view of the nature of subducted crust, two types of subduction and collision have been respectively recognized in nature. On one hand, the crustal subduction occurs due to underflow of either oceanic crust (Pacific type) or continental crust (Alpine type). On the other hand, the continental collision proceeds by arc-continent collision (Himalaya-Tibet type) or continent-continent collision (Dabie-Sulu type). The key issues in the future study of continental dynamics are the chemical changes and differential exhumation in continental deep subduction zones, and the temporal-spatial transition from oceanic subduction to continental subduction.
The foramtion and evolution of collisional orogen is a prominent feature along convergent plate margins, and is generally a complex process. This article presents an integrated study of zircon genesis, U-Pb age and Lu-Hf isotope composition as well as geological characteristics for the western Dabie orogen to constrain its multi-stage evolution history. The results suggest that the formation of oceanic crust in the Huwan area was constrained at ca. 400―430 Ma, which was slightly later than the collision of the northern Qinling with the North China Block. It formed in a marginal basin in the northern margin of the Yangtze Block. The peak metamorphism of eclogite in the Huwan area occurred at ca. 310 Ma, and the timing of the initial exhumation of oceanic eclogite was about 270 Ma. The high to ultrahigh pressure (HP-UHP) metamorphic rocks in the Xinxian and the Hong'an metamorphic zones have the same ages and natures as those of the HP-UHP metamorphic rocks in the other Dabie-Sulu terrains, and also have experienced multi-stage exhumation, and thus can be taken as a coherent part of the Dabie-Sulu orogen. Therefore, the Qinling-Dabie-Sulu orogen is a typical multi-stage continental collision orogen, with an amalgamation process extending more than 200 Ma.
WU YuanBao State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China
