Hadean to early Mesoarchean rocks and zircons in the North China Craton: A review

Abstract

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.