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Precambrian |
Key Laboratory of Mineral Resources, Institute of Geology & Geophysics, Chinese Academy of Sciences, Beijing, 100029, China mgzhai{at}mail.igcas.ac.cn
The North China Craton (NCC) is a major Archaean craton, covering an area of c.300 000 km2 in north and northeast China. Almost all Archaean rocks on the craton experienced high-grade metamorphism and strong migmatization, so that the preserved greenstone belts underwent granulite-amphibolite-facies metamorphism, anatectic melting and strong deformation. This suggests that the NCC may have a more complicated early tectonic history than most other cratonic nuclei. The oldest NCC rocks are 3.8 Ga granitic gneisses in NE China and supracrustal rocks in eastern Hebei. Major continental growth occurred at 2.9–2.7 Ga. Two subsequent high-grade metamorphic events occurred at 2.6–2.45 Ga (‘2.5 Ga event’) and 1.9–1.75 Ga (‘1.8 Ga event’). The older episode is considered to mark an amalgamation event, whereas the 1.8 Ga event represents the final cratonization of the NCC. Some researchers have divided the 1.8 Ga event into a 1.9–1.8 Ga metamorphic event (interpreted as a continent-continent collision) followed by a 1.8–1.65 Ga rifting episode. Other workers have suggested that the metamorphism and rifting could be parts of a single tectonic event related to Palaeo-Mesoproterozoic mantle upwelling. The general consensus on the NCC for the period 2.5–1.8 Ga is that the craton was then in an inactive stage. However, in this paper it is proposed that several Palaeoproterozoic mobile belts existed (showing many of the characteristics of Phanerozoic orogens). During the Mesoproterozoic-Neoproterozoic, a set of sedimentary sequences (the Changcheng-Jixian-Qingbaikou systems) constituted a disconformable-pseudoconformable succession within an intra-cratonic aulacogen. The signature of a 1.4–0.9 Ga orogen and the Rodinia breakup is very weak, indicating that the NCC did not experience major deformation as it was amalgamated into the Rodinia supercontinent.
