Precambrian key tectonic events and evolution of the North China craton

Abstract

The North China craton (NCC) is one of oldest cratons in the world, with crust up to c. 3.8 Ga old, and has a complicated evolution. The main Early Precambrian geological events and key tectonic issues are as follows. (1) Old continental nuclei have been recognized in the NCC, and the oldest remnants of granitic gneiss and supracrustal rocks are 3.8 Ga old. The main crustal growth in the NCC took place at 2.9–2.7 Ga. The NCC can be divided into several microblocks, which are separated by Archaean greenstone belts that represent continental accretion surrounding the old continental nuclei. (2) By 2.5 Ga, the microblocks amalgamated to form a coherent craton by continent–continent, arc–continent or arc–arc collisions. The tectonic processes in Neoarchaean and modern times appear to differ more in degree than in principle. Extensive intrusion of K-granite sills and mafic dykes and regional upper amphibolite- to granulite-facies metamorphism occurred, and marked the beginning of cratonization in the NCC. Coeval ultramafic–mafic and syenitic dykes of c. 2500 Ma in Eastern Hebei indicate that the NCC became a stable, thick and huge continent at the end of the Archaean, and probably was a part of the Neoarchaean supercontinent that has been suggested by previous studies. (3) In the period between 2500 and 2350 Ma, the NCC was tectonically inactive, but the development of a Palaeoproterozoic volcanic and granitic rocks occurred between 2300 and 1950 Ma. The volcanic–sedimentary rocks are termed Palaeoproterozoic mobile belts; these have a linear distribution, and were affected by strong folding and metamorphism at 1900–1850 Ma, and intruded by granites and pegmatites at 1850–1800 Ma. The Palaeoproterozoic mobile belts formed and evolved within the craton or continental margin (epicontinental geosyncline). Some 2.30–1.95 Ga rift-margin, passive continental margin deposits, analogous arc or back-arc assemblages, as well as HP and HT–UHT metamorphic complexes seem to be comparable with many in the late Phanerozoic orogenic belts. Regarding Palaeoproterozoic orogeny in other cratons, it is possible that a global Palaeoproterozoic orogenic event occurred, existed and resulted in the formation of a pre-Rodinian supercontinent at c. 2.0–1.85 Ga. (4) In contrast, the c. 1800 Ma event is an extension–migmatization event, which includes uplift of the lower crust of the NCC as a whole, the emplacement of mafic dyke swarms, continental rifting, and intrusion of an orogenic magmatic association. This event has been considered to be related to the break-up of the pre-Rodinian supercontinent at 1.8 Ga, attributed to a Palaeoproterozoic plume. (5) As HP and HT–UHT metamorphic rocks occur widely in the NCC, their high pressure of 10–14 kbar has attracted attention from researchers, and several continental collisional models have been proposed. However, it is argued that these rocks have much higher geothermal gradient and much slower uplift rate than those in Phanerozoic orogenic belts. Moreover, HP and HT–UHT rocks commonly occur together and are not distributed in linear zones, suggesting that the geological and tectonic implications of these data should be reassessed.

Episodic crustal growth in the southern segment of the Trans-North China Orogen across the Archean-Proterozoic boundary

“…11b and c), suggesting two episodes of crustal growth from the Late Mesoarchean to the beginning of the Early Paleoproterozoic in the southern segment of the TNCO, which are contemporaneous with the two main crustal growth episodes recognized in the NCC (2.9-2.7 Ga and 2.55-2.50 Ga; Zhai et al, 2010). Juvenile continental crust is produced at subduction zones or by mantle plumes (Condie, 1998).…”

“…1a) is the oldest cratonic block in China (∼3.8 Ga; Liu et al, 1992), with widespread Archean to Paleoproterozoic rocks (Fig. 1a) forming during several tectonic cycles (e.g., Zhao et al, 2005Zhao et al, , 2012Lu et al, 2008;Zhai et al, 2010;Zhao and Zhai, 2013). It is commonly recognized that the NCC resulted from amalgamation of several microblocks, but the timing and processes involved are still a subject of debate (e.g., Kusky and Li, 2003;Zhai et al, 2000Zhai et al, , 2005Zhai et al, , 2010Zhao, 2001;Zhao et al, 2005Zhao et al, , 2012Zhao and Zhai, 2013), with several competing models proposed.…”

“…1a) forming during several tectonic cycles (e.g., Zhao et al, 2005Zhao et al, , 2012Lu et al, 2008;Zhai et al, 2010;Zhao and Zhai, 2013). It is commonly recognized that the NCC resulted from amalgamation of several microblocks, but the timing and processes involved are still a subject of debate (e.g., Kusky and Li, 2003;Zhai et al, 2000Zhai et al, , 2005Zhai et al, , 2010Zhao, 2001;Zhao et al, 2005Zhao et al, , 2012Zhao and Zhai, 2013), with several competing models proposed. Zhai et al (2000Zhai et al ( , 2005Zhai et al ( , 2010 proposed that the NCC can be divided into several microblocks connected by greenstone belts and granites and were amalgamated at the end of the Neoarchean (∼2.5 Ga).…”

“…It is commonly recognized that the NCC resulted from amalgamation of several microblocks, but the timing and processes involved are still a subject of debate (e.g., Kusky and Li, 2003;Zhai et al, 2000Zhai et al, , 2005Zhai et al, , 2010Zhao, 2001;Zhao et al, 2005Zhao et al, , 2012Zhao and Zhai, 2013), with several competing models proposed. Zhai et al (2000Zhai et al ( , 2005Zhai et al ( , 2010 proposed that the NCC can be divided into several microblocks connected by greenstone belts and granites and were amalgamated at the end of the Neoarchean (∼2.5 Ga). Zhao (2001) initially proposed that the NCC formed by amalgamation of the Eastern and Western Blocks along the Trans-North China Orogen (TNCO; Fig.…”

A ∼2.5 Ga magmatic event at the northern margin of the Yangtze craton: Evidence from U-Pb dating and Hf isotope analysis of zircons from the Douling Complex in the South Qinling orogen

“…It is well known that Archean rocks are extensively exposed in the North China craton. The oldest rocks and crustal materials were dated at 3.8 Ga. Two major phases of magmatism occurred in 2.8-2.7 Ga and 2.55-2.50 Ga, whereas high grade metamorphism took place at ~2.5 Ga [2,3]. In contrast, the Precambrian basement of the Yangtze craton is poorly exposed; it was deeply buried and was covered by voluminous Neoproterozoic-Phanerozoic sedimentary sequences.…”