Major advancements in understanding the formation and evolution of early continental crust have been made following the study on origin of tonalite–trondhjemite–granodiorite (TTG) rocks, which dominate in Earth’s earliest-formed continental crust. There is a broad consensus that Archean felsic continental crust was derived from the partial melting of mafic crust. However, controversy has long surrounded the issue of whether Archean TTG rocks were sourced from subducted oceanic slabs or oceanic plateau (overthickened crust), corresponding to plate tectonic settings (e.g., island arc) or some pre-plate tectonics (e.g., mantle plume, sagduction, etc.), respectively. In this case, water contents, oxygen isotopes and some other trace elements of the source rocks are regarded as important insights as they should be different between plate tectonic settings and other pre-plate tectonic settings (e.g., mantle plumes). Therefore, we report variations in water contents, oxygen isotopes, hafnium isotopes and trace elements of zircons, associated with whole-rock major and trace elements of the ~2.5 Ga Taipingzhai TTG gneisses in the Eastern Block of the North China Craton. Based on these data, we prove that oxygen and water in zircons can be used as a good proxy for primordial oxygen and water in TTG magmas. In this study, zircons from the Taipingzhai TTG gneisses show high oxygen isotopes but relatively low water content, with no or weakly negative correlation between water and oxygen isotopes, indicating that the source rocks of TTG were hybridized hydrated mafic rocks with majority of slightly hydrous oceanic plateau and minority of high-δ18O supracrustal materials. The low water content is revealed by TTG gneisses in this study in contrast to high water content of ~2.5 Ga TTG gneisses in the Trans-North China Orogen, which were suggested to be formed in subduction zone through previous studies. Such results indicate a combined two-stage mantle plume-sagduction model, in which minor TTG (mantle-like δ18O, low H2O) and voluminous TTG (high δ18O, low H2O) were formed in the Eastern Block of the North China Craton at ~2.7 Ga and ~2.5 Ga, respectively. Through our study, Earth’s earliest-formed Archean continents were suggested to be most likely originated from oceanic plateaus, which was formed by mantle plumes associated with sagduction, relative to the island arcs via oceanic subduction under a plate tectonics regime.