Cratonization is a key geological process to form stable continental masses with a considerable scale.The Precambrian global cratonization and formation of supercratons in the world is an unrepeated event in the history of the Earth's formation and evolution.Mainly based on study of early Precambrian geology in Eastern Hebei Region and combining other Archean regions in the North China Craton (NCC),the author proposes a two-stage cratonization model of the NCC.The first stage took place at the end of Neoarchean of ～2.5 Ga (boundary time between Archean and Proterozoic),when several micro-blocks were amalgamated together with amphibolite-granulite facies metamorphism and intrusion of crustal-melting granites to form the present-scale NCC.The second cratonization event is cratonic reworking,corresponding to rifting-subduction-collision at 2.3-1.97 Ga and subsequent extension-uplifting related to upwelling mantle at 1.97-1.82 Ga,which could be linked to,respectively,assembly and breaking up of the Columbia Supercontinent.Three main Paleoproterozoic mobile belts in the NCC record that small remnant Neoarchean ocean basins and continental rift basins within the craton were opened and finally closed,and metamorphosed to greenschist-amphibolite facies at ～2.0-1.97 Ga.After that,high-grade granulite facies (HT-HP and HT-UHT) metamorphism with abnormally high heat occurred at 1.97-1.82 Ga.A metamorphism-migmatization event that includes lower crust of the NCC uplifting as a whole,intrusion of mafic dyke swarms,continental rifting and anorogenic magmatic action took place in 1.82-1.65 Ga,marking that the second cratonization of the NCC was finally accomplished and started to evolve to a period of stable continent (platform).
The main old lands in China include the North China Block(NCB),South China Block(SCB)and Tarim Block(TRB),all of which have individual tectonic evolving histories.The NCB experienced complex geological evolution since the early Precambrian onwards,and carries important records from the old continental nuclei,giant crustal growth episode and cratonization(stabilitization),then to the Paleoproterozoic rifting-subduction-accretion-collision with imprints of the Great Oxygen Event(GOE),and to the Late Paleoproterozoic-Neoproterozoic multi-stage rifting representing North China platform tectonic features.The TRB has two-layer basement of the Early Precambrian metamorphic complexes and Neoproterozoic sedimentary sequences.Three till sheets have been reported.The SCB consists of the Yangtze Block(YZB)and Cathaysia Block(CTB)that were cohered in the Neoproterozoic.The YZB recorded tectonic processes of the Early Precambrian crustal growth,1.0–0.9 Ga and 0.8–0.6 Ga metamorphic-magmatic events,and two Neoproterozoic glaciations.The CTB consists of ca.1.8Ga,1.0 to 0.9 Ga and ca.0.8 Ga granitic gneisses and metamorphic rocks,indicating there was a vast Precambrian basement.The Neoproterozoic sedimentary rocks overlie partly on the basement.That the YZB and CTB have a Neoproterozoic uniform cover layer illustrates the SCB should form,at least,during 1.0–0.9 Ga,corresponding to the Rodinia Supercontinent.The Central Chinese Orogenic System with high-ultra-high-pressure metamorphic rocks supports a suggestion that the abovementioned three old lands were collided to assemble a unified Chinese Continent during the Pangea orogenic period.
