Paleoarchean continental emergence in the North China Craton indicated by low δ18O granites

Emergent continental crust is important for the evolution of Earth’s surface system and the development of habitability, and it is apparent that early Archean cratons were locally emerged. However, it remains unresolved if the North China Craton, which preserves ancient (4.1−4.0 Ga) crustal remnants, had emergent continental crust during the early Archean. Here, we report geochronological and geochemical data on Paleo−Mesoarchean potassic granites in Eastern Hebei, within the North China Craton, to determine whether or not there was any early Archean exposed landmass in this craton. We constrain that the studied potassic granites formed at ca. 3.2 Ga, and their bulk-rock and zircon Hf isotopic geochemistry reveals that they were produced by anatexis of Paleoarchean tonalite-trondhjemite-granodiorite (TTG) crust. Their low zircon δ18O values should have been inherited from their Paleoarchean TTG source, and 18O-depletion of this Paleoarchean TTG source was achieved through high-temperature hydrothermal alteration with the infiltration of isotopically light meteoric water into the shallow crust, prior to the ca. 3.2 Ga anatexis. The identification of Paleoarchean TTG crust altered by meteoric water in Eastern Hebei indicates the emergence of continental crust in the North China Craton during 3.6−3.2 Ga, and this Paleoarchean continental emergence could have been associated with magmatic underplating during mantle plume activities, which is also evidenced by the Paleoarchean enriched plume remnants in Eastern Hebei.