Early Neoarchean geodynamic regime in the North China Craton: Constraints from 2.7 Ga granitoids in the southern Jilin terrane

Abstract

Identifying the processes responsible for the generation and evolution of the Archean continental crust is crucial for understanding the tectonic regimes present on early Earth. A major episode of continental growth during the early Neoarchean has been identified in many cratons worldwide. Indeed, early Neoarchean magmatism has been recognized in several terranes within the North China Craton over the past decade, although the geodynamic regime in which such activity occurred remains highly debated. Here, we focus on newly recognized early Neoarchean mylonitic trondhjemite and granodiorite from the southern Jilin terrane, China, to address this knowledge gap. Zircon U-Pb geochronology reveals that these granitoids formed at ca. 2.7 Ga. They display adakitic geochemical characteristics, such as high Sr/Y and LaN/YbN ratios. Their low MgO, Cr, and Ni contents, along with low δ18O values (4.19‰–5.39‰) and positive εHf(t) (0.7–6.5) and εNd(t) (2.0–2.6) values, indicate that they originated from thickened juvenile lower continental crust. Thermodynamic modeling further constrains the ca. 2.7 Ga granitoids to have been generated from partial melting driven by amphibole breakdown under granulite-facies P-T conditions of 10–15 kbar and 800–900 °C, with garnet and amphibole as the major residual minerals. Combined with previous studies, we suggest that the North China Craton underwent significant crustal growth during the early Neoarchean, which was likely attributed to the synergistic effects of waning mantle plume activity and the coeval onset of plate tectonics.