Role of Post-Collisional Magmatism in Continental Growth and Reworking Since the Late Archean

The mechanisms responsible for the formation and compositional evolution of continental crust remain central questions in Earth science. Post-collisional magmatism is widely preserved in the continental record; however, its contribution to crustal growth may be underestimated because enriched isotopic signatures obscure juvenile mantle input. Here, we present integrated whole-rock geochemical, Sm–Nd–O isotopic, and zircon U–Pb–Hf–O isotopic data for ∼2.49–2.45 Ga post-collisional mafic and felsic rocks from the Daqingshan Terrane, western North China Craton. The Daqingshan mafic rocks lack diagnostic arc-like signatures, show no pronounced depletion in high-field-strength elements, and have relatively radiogenic Nd–Hf isotopic compositions, indicating derivation from a depleted but variably hybridized mantle source. Systematic mafic–felsic isotopic correspondences, together with large isotopic variations (whole-rock ε_Nd(t) = −3.1 to +4.5, zircon ε_Hf(t) = −11.2 to +6.4, zircon δ¹⁸O = 2.9‰ to 9.2‰), indicate that the felsic batholiths were genetically linked to the mafic magmas and formed through variable combinations of mafic magma differentiation, magma hybridization, and crustal anatexis. Hf–O isotope mixing and mass-balance estimates suggest that juvenile mantle-derived material accounts for at least ∼36% of the exposed felsic–intermediate assemblage and may approach ∼50% when unexposed mafic underplates are considered. Comparable magmatic timescales and mafic compositional trajectories in other collisional belts suggest that similar processes may have operated more widely. These results identify post-collisional mafic magmatism as a cryptic mechanism for continental crust preservation, growth, and reworking since the late Archean.