Low-pressure ∼3.53 Ga trondhjemite in the Eastern Hebei: Implications on the continental nucleus formation of the North China Craton

Abstract

Continental nuclei provide essential genetic insights into the formation and evolution of the continental crust during the early Archean. This study reported the discovery of a ∼3.53 Ga trondhjemite from the newly identified Eoarchean–Paleoarchean Labashan Complex, located within the Eastern Hebei continental nucleus of the North China Craton (NCC). This study conducted comprehensive analyses, including zircon geochronology, zircon Hf isotopes, and whole-rock geochemistry, on this ancient rock. Zircon U-Pb dating revealed a crystallization age of 3533 ± 27 Ma. The trondhjemite displays characteristics typical of low-pressure types, such as low Sr/Y (7.5–12.8), (La/Yb)_N (9.2–19.2), and (Gd/Yb)_N (1.1–2.0) ratios, along with slight negative Eu anomalies (0.54–0.86). Most zircons exhibit unradiogenic Hf isotopes, with negative ε_Hf(t) values as low as −7.0 and T_DM² ages ranging from 4501 to 3606 Ma. These results suggest that the parental magma of the ∼3.53 Ga trondhjemite likely originated from the partial melting of Hadean to early Eoarchean hydrated mafic protocrust, and formed at shallow depths with a residue enriched in amphibole and plagioclase. Our findings, alongside previous research, indicate that the NCC possesses a Hadean crustal evolutionary history, positioning it as one of Earth’s oldest fragments. We propose that the formation of the NCC’s continental nuclei, including the Eastern Hebei region, involved multiple stages of crustal reworking and recycling, with minor contributions from juvenile mantle-derived materials before the early Neoarchean. The most plausible mechanism for this evolution is the activity of mantle plumes beneath a stagnant lid.