Chemical Diversity of Archean Sanukitoids Driven by Variable Sediment Recycling: A Case Study from the North China Craton

Late Archean sanukitoid rocks preserve the key to unravel the transitional crust–mantle geodynamics of the early Earth. The increasingly identified chemical diversity of Archean sanukitoid rocks could provide new clues to clarify this issue. Here, a suite of late Neoarchean (~2560–2491 Ma) dioritic and (quartz) monzodioritic gneisses were identified in the Pingquan complex of North China Craton, and whole-rock major and trace element as well as zircon U–Pb and Lu-Hf isotopic data were obtained for these rocks. In particular, the (quartz) monzodioritic gneisses show higher K2O/Na2O, Sr + Ba, Sr/Y, and more enriched zircon εHf(t2) values than the dioritic gneisses, and their overall chemical variation broadly overlaps with that of global sanukitoid rocks. Petrogenetic and thermodynamic-trace element modeling studies were carried out. The dioritic gneisses were modeled to be derived from partial melting of a mixed mantle source (65% depleted MORB mantle (DMM), 29% altered oceanic crust melts (OCM), and 6% sediment-derived melts (SM)) at 1.4–1.9 GPa (1030–1060°C and 2 wt.% H2O content). The monzodioritic gneisses require more sediment recycling (9%), and were derived from the metasomatized mantle sources (~65% DMM, ~26% OCM, and ~ 9% SM) at higher pressures of ~ 2.0–2.1 GPa (980–1050°C and 2 wt.% H2O content). In comparison, the quartz monzodioritic gneisses were derived from the metasomatized mantle sources (~60% DMM, ~29% OCM, and ~ 11% SM) at the highest pressures of ~ 2.4–2.8 GPa (1050–1070°C and 2 wt.% H2O content). Integrating the modeled melting P–T conditions and regional geological data, these rocks formed most likely under a hot plate subduction system. Further compilation of global Archean sanukitoid rocks indicate that similar chemical diversity as the Pingquan case appeared globally during the Neoarchean. This chemical diversity cannot be achieved without sediment recycling, which is coincident with the inferred late Archean continental emergence and weathering, and likely evolved under the plate tectonic paradigm.