Conclusions
At the Late Triassic, the North China craton and South China craton collided at the Qinling-Dabie Orogen and resulted in the thickening of the lithosphere in the North China craton (Figure 8a). At about 160-150 Ma (Late Jurassic), drastic thinning and collapse of the lithosphere occurred in the eastern NC due to delamination of the cold and heavy lithosphere (Deng et al., 2000; Zhang et al., 2001a, 2001b, 2001c; Gao et al., 2002). The delamination led to upwelling of the asthenosphere, volcanism and the production of granite belts in the eastern NC (Dong et al., 2000; Hou et al., 2003). Following delamination, thinning of the lithosphere and collapse of the plateau occurred. The initial extension and collapse of the Eastern North China Plateau began in the Late Jurassic and Early Cretaceous. The extensive collapse of the plateau happened predominantly in the Eocene and caused development of the extensional basins-mountains system (Ma et al., 1983; Zheng et al., 1988; Hou et al., 2001; Wang et al., 2005). The destruction of the NC finally produces the thinnest lithosphere of the eastern China (Figure 8b and 8c).
Figure 8. The destruction history of the North China Craton
(a) Intra-plate deformation of the North China Craton; (b) the first stage of destruction of the NCC (delamination of lower crust); (c) the second stage of destruction of the NCC (underplating and replacement of lithoshpere).
The above-discussed tectonics of the Bohai Bay Basin suggests that the basin experienced a complex evolution in the Mesozoic and Cenozoic. The evolution of the basin spans from the Late Jurassic to the Neogene, and discrete, Late Jurassic-Early Cretaceous and Eogene-Neogene rifting cycles are distinguished on the basis of differing basin orientations. Extension and thermal subsidence of the basin is related to rifting events triggered by the response of the Eurasian plate to movement of the Kula and Pacific plates.
The Eastern North China Plateau resulted from Early Mesozoic convergence between the NC and the SC. Evidence for the onset of the destruction of the NC, triggered by the delamination of thick lithosphere of the eastern NC, is preserved in the NW-trending grabens which form an en echelon arrangement on the west of Tanlu Fault Zone and the NNE-trending grabens within the Tanlu Fault Zone (especially in the offshore portion of the Bohai Bay Basin). The extensive destruction of the craton was associated with the broader extensional environment of northeast Asia. The offshore (Bohai Sea) portion is the region that best preserves the evidence of the destruction of the NC. The NC represents a non-typical craton unique with respect to the Earth’s other stable cratons.