Growth and reworking of the early Precambrian continental crust in the North China Craton: Constraints from zircon Hf isotopes

Abstract

We synthesize more than 2600 Hf isotope data on the Archean-Paleoproterozoic zircons from the North China Craton (NCC). Recalculation of the data based on single stage and two-stage Hf model ages of the Eastern Block of the NCC shows peak ages of 3902±13Ma and 3978±18Ma, respectively, and also small peaks at 3.5–4.0Ga. The majority of zircon εHf(t) values are positive, suggesting the possibility of the crust and the mantle differentiation at ca. 3.9–4.0Ga in the Eastern Block of the NCC. Most magmatic zircons from the whole of NCC have their Hf model age range of 2.4–2.9Ga, and the single stage model ages is cluster at 2698±4Ma, whereas the two-stage model ages concentrate at 2714±5Ma, implying that the protoliths were juvenile crustal rocks. The most prominent peak at 2.7Ga indicates that this period marks the most important stage of the crust-mantle differentiation and crust formation of the NCC. The widespread 2.5Ga rocks in the NCC and the absence of the 2.5Ga peaks in Hf model ages are consistent with the partial melting and reworking of the juvenile rocks at 2.5Ga. Furthermore, the 2.5–1.7Ga zircon Hf isotope features are also related to the reworking of the crustal rocks. Our results from the integration of a large database suggest that the Eastern Block and the Trans-North China Orogen have undergone similar crust-mantle differentiation and magmatism, leading to the conclusion that the essential cratonization of the North China took place at the end of Neoarchean.