Zircon U-Pb and Lu-Hf isotopes of Huai'an complex granites, North China Craton: Implications for crustal growth, reworking and tectonic evolution

Abstract The Huai'an Complex, located in the north-central North China Craton (NCC), consists of tonalite-trondhjemite-granodiorite (TTG) gneisses and minor intrusive bodies of granite. Its late Neoarchean to Paleoproterozoic crustal evolution is still unclear, and the study of this evolution will constrain the tectonic evolution of the NCC. The LA-ICP-MS zircon U Pb ages of ten granites from the Huai'an Complex reveal three episodes of magmatism: 2.6–2.3 Ga, 2.0–1.7 Ga, and a few ages from ~2.3–2.0 Ga. The 2.6–2.3 Ga, 2.3–2.0 Ga and 2.0–1.7 Ga zircons have average eHf(t) values of 2.79, −4.0, and − 6.05, average TDM2 values of 2.78 Ga, 2.98 Ga, and 2.86 Ga, and average 176Lu/177Hf ratios of 0.033, 0.021, and 0.027, respectively, indicating that their magma sources were from the melting of the Neoarchean “mildly depleted” SCLM, the mafic Mesoarchean lower crust, and the mafic Meso-Neoarchean lower crust. Zircon geochemical characteristics indicate that the Huai'an Complex was a long-lived continental magmatic arc during 2.6–2.0 Ga. The juvenile crustal proportion was 100% during 3.1–2.6 Ga and decreased through 50% at 2.5 Ga to 20% at 2.45 Ga; it then increased to 45% at 2.3 Ga and finally decreased to 0% during 1.95–1.7 Ga, indicating that the crust experienced a growth stage during 3.1–2.5 Ga and reworking stage during 2.5–1.7 Ga and that the Huai'an Complex underwent compression-extension-compression processes during 2.6–1.7 Ga. The compression-dominant tectonic setting during 2.6–2.45 Ga may have been linked to the subduction and amalgamation of microblocks. The compressive setting during 2.3–1.7 Ga may have been related to amalgamation between the Eastern and Western Blocks. The modeled crustal growth curve suggests that approximately 67% of the existing continental crust of the Huai'an Complex formed before 2.6 Ga, which is similar to the NCC and several other cratons worldwide. Our results favor the two-stage cratonization model of the NCC.