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

Emergent continental crust with subaerial exposure is important for the evolution of Earth’s surface system and the development of habitability, and it is evident that early Archean local emergence of continental crust occurred in several Archean cratons. 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 trace 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 and 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 the early Archean, 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.