A two-stage mantle plume-sagduction origin of Archean continental crust revealed by water and oxygen isotopes of TTGs
Dingyi Zhao, Peter A. Cawood, Fang‐Zhen Teng, Guochun Zhao, Xiaoping Xia, Min Sun, Xiangsong Wang
Abstract
Evolution of Archean continental crust involved partial melting of mafic crust to form the tonalite-trondhjemite-granodiorite (TTG) series. However, crustal generation remains enigmatic with both plate tectonic and non-plate tectonic modes proposed. In this study, we show that zircons from the ~2.5–billion years ago TTGs in the Eastern Block (EB) of the North China Craton have low water contents (median of 263 parts per million) and high δ 18 O values (median of 6.22‰) and a negative correlation between them, which suggest a thick hybridized and hydrated mafic source. By contrast, zircon water contents of the adjoining coeval TTGs in the Trans-North China Orogen, formed in a supra-subduction zone setting, are notably higher. These results support a two-stage mantle plume-sagduction process for TTG formation. Our study suggests that Archean continental crust, such as that in the EB, most likely originated from plume-related oceanic plateaus, rather than subduction-related island arc magmatism under a plate tectonic regime.