Evidence of Episodic Crustal Formation From the Hadean to the NeoArchean From China

Hadean to Neoarchean episodic crustal growth: Detrital zircon records in Paleoproterozoic quartzites from the southern North China Craton

Authors:

Zhang et al

Abstract:

The Archean terranes exposed in several regions of the North China Craton (NCC) provide important winodws to evaluate the Hadean-Archean continental crustal evolutoin history. Here we report results from SIMS zircon geochronology and oxygen isotopes, as well as LA-ICPMS zircon Hf isotopic analyses on detrital zircons from Paleoproterozoic quartzites to probe the early crustal evolution in the southern NCC. Our data show episodic magmatism during the Eoarchean, Paleoarchean, Mesoarchean, Neoarchean and Paleoproterozoic as inferred from the concordant ages of 3.6 Ga and 2.2 Ga and the well-defined upper intercept ages of 3404 ± 30 Ma, 2919 ± 31 Ma, 2772 ± 9.5 Ma, 2698 ± 4.7 Ma, 2652 ± 6.7 Ma, and 2532 ± 5.2 Ma. The Hf and oxygen isotopic compositions of Eoarchean-Paleoarchean zircons demonstrate that the cratonic nucleus of the NCC was built in the Hadean (∼4.0 Ga), similar to the timing of formation of the nuclei of old cratons elsewhere on the globe such as the Yilgarn Craton, Western Australia, and the Slave Craton, Canada, with the Eoarchean-Paleoarchean (3.8 Ga, 3.6 Ga and 3.4 Ga) marking the first phase of crustal reworking of the Hadean crust. The salient aspect of our data is that the Meoarchean to early Neoarchean (3.0-2.6 Ga with a peak at 2.7 Ga) was a significant period for crustal growth from the mantle throughout the NCC, comparable with the event of major Archean crustal growth worldwide. The latest Neoarchean (∼2.5 Ga) marks a period of significant crustal reworking that led to remelting of the newly-formed juvenile mafic crust (∼2.7 Ga). Integration with the data obtained from the TTG (tonalite-trondhjemite-granodiorite) and granitoid rocks of the Archean terranes and the lower crustal granulite xenoliths from various parts of the NCC suggests that the episodic Eoarchean via Paleoarchean and Mesoarchean to Neoarchean crustal growth as well as crustal reworking intensely destroyed the ancient cratonic nucleus, resulting in the scarce preservation of the Hadean and Eoarchean remnants in both the upper and lower crust of the NCC. Following the Paleoproterozoic sedimentation of the Archean zircons, apart from Pb loss during the subsequent thermal events, there was no major alteration in the Hf and oxygen isotopic compositions. Thus, our detrital zircon data provide convincing evidence for the repeated crustal growth and reworking of the NCC in the Archean.