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The North China Craton (NCC) is the largest craton on the Chinese Mainland, with 3.8–3.0 Ga rocks occurring mainly in three areas, namely: Anshan-Benxi (Anben), eastern Hebei, and Xinyang. In addition, 3.0 Ga and 3.1 Ga TTG (tonalite-trondhjemite-granodiorite) rocks have also been identified in north Liaoning and the Bohai Bay Basin, respectively. Detrital and xenocrystic zircons dated at 4.1–3.1 Ga occur more widely in the craton. In Anben, >3.3 Ga rocks are mainly distributed in six complexes, whereas in eastern Hebei, 3.8 Ga TTG rocks and 4.0–3.9 Ga detrital zircons have recently been discovered. Anben is similar to eastern Hebei in terms of the Archean zircon age records, but >3.3 Ga TTG rocks are different in both rock-type and composition. The recent identification of 3.8 Ga granitic xenoliths in young volcanic rock at Xinyang indicates the existence of Eoarchean rocks in the deep crust of the craton. Taking the NCC as a whole, the most significant zircon-forming magmatic events occurred at 3.8 Ga, 3.7–3.65 Ga, 3.45 Ga, 3.3 Ga and 3.1 Ga. The >3.0 Ga TTG rocks are mainly trondhjemite, with their low Sr/Y and La/Yb ratios indicating formation under low- to medium-pressure conditions. These are different from 3.0 to 2.5 Ga TTG rocks in the NCC and 3.8–3.0 Ga TTG rocks in southern West Greenland, which are dominated by tonalite, with some having high Sr/Y and La/Yb ratios. The >3.0 Ga rocks have large variations in whole-rock ε Nd (t) and in-situ zircon ε Hf (t), with many showing negative values. Zircons have δ18O values mainly between 5.0 and 7.0‰, consistent with Hadean and Archean magmatic zircon data worldwide. The diversity of Eoarchean granitoid magmatism across the craton indicates that continental evolution on Earth at that time already displayed complexity and maturity. It is further considered that the NCC may contain several different ancient continental nuclei with long-term formation and evolutionary histories back to the Hadean. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two new paragneisses containing detrital zircons as old as 3.8Ga were reported. [•] Multi-phased crustal addition and recycling from 3.8 to 3.4Ga were identified. [•] A nearly complete Archean crustal evolution was recorded in eastern Hebei. [Copyright &y& Elsevier]

Abstract: The eastern part of the North China Craton in eastern Hebei Province contains metamorphosed and deformed Neoarchaean to earliest Palaeoproterozoic rocks (∼2550–2490Ma) with some older Archaean rocks. Numerous precise U–Pb zircon ages, structural observations, Nd and Hf isotopic data and whole rock geochemistry (our new data with reassessment and integration of previous work) show that there is not a single protracted event at the end of the Archaean lasting ∼60 million years, but that from east to west there are several separate events with their own unique character. The eastern coastal region is dominated by weakly deformed 2530–2510Ma granites with subordinate granodiorites, diorites and magnesian-gabbros. This suite has inclusions of older 2550–2540Ma plutonic rocks. ∼80km inland to the west, there are amphibolite facies biotite-rich schists, lenses of BIF, siliceous fuchsite bearing rocks with 3880–3540Ma zircons, peridotites and orthogneisses, all intruded by younger granites and monzonites. Three amphibolite–granulite facies gneisses and schists with volcano-sedimentary protoliths have 2548–2534Ma igneous zircon populations, rare inheritance back to >3600Ma and 2506±6Ma zircon equated with granulite facies metamorphism. Older tonalitic to granitic polyphase orthogneisses contain 3287±11Ma to ∼2940Ma igneous components. Late kinematic high Fe/Mg gabbros, monzonites and granites have ages of 2499±7 to 2491±13Ma. 160–100km inland, gneissose 2550–2530Ma quartz-diorite to tonalitic rocks occur as intrusions into, or intercalations with, mafic rocks. These were affected by granulite facies metamorphism but then widely retrogressed. Abundant syn-granulite facies neosome and later shear zones disrupt the early geological relationships. The granulite facies metamorphism is dated at 2503±5Ma from several samples, including a syn-granulite facies pegmatite. The Neoarchaean igneous rocks show marked negative Nb, Ti anomalies, LIL enrichment and enrichment of the light REE relative to the heavy REE across the entire ultramafic, basaltic, tonalitic and granitic compositional spectrum: 2550–2530Ma tonalites and quartz diorites are most important in the west and 2530–2510Ma granites are most important in the east. Their composition resembles those formed at various stages of magmatic arc evolution at a convergent plate boundary, rather than being plume products. The eastern Hebei rocks thus formed in a complex arc with distinct pulses of plutonism at 2550–2540 and 2530–2510Ma, with local incorporation of older continental crust. The 2500–2490Ma thermal event with its associated higher Fe/Mg magmas involved interaction of underplated fractionated gabbroic melt with deep crustal melts, possibly during extension of an already ∼50 million years old arc. [Copyright &y& Elsevier]