∼2.7-Ga Crustal Growth in the North China Craton: Evidence from Zircon U-Pb Ages and Hf Isotopes of the Sushui Complex in the Zhongtiao Terrane

Abstract

AbstractThe major Precambrian crustal growth in the North China Craton (NCC) has been thought to have occurred at ∼2.5 Ga. Here we present secondary ion mass spectroscopy (SIMS) and laser ablation–inductively coupled mass spectrometry (LA-ICP-MS) zircon U-Pb ages and Hf isotope compositions from dioritic and tonalite-trondhjemite-granodiorite (TTG) gneisses of the Neoarchean-Paleoproterozoic metamorphic terrane in the central NCC. Zircons from the trondhjemitic samples yield emplacement ages at and Ma. Those from the dioritic gneiss yield an age of Ma. The TTG gneisses are characterized by a Na-rich and K-poor () nature; strongly fractionated rare earth element patterns (); high Sr (418‰, 318‰) and Sr/Y (78, 49); low Y (5.4‰, 6.4‰) and YbN (3.0, 3.6); and low MgO (0.89%, 1.10%), Mg# (47, 42), Cr (39‰, 20‰), and Ni (11‰, 8‰), Nb/Ta (16, 12), which suggests that magmas were derived from the partial melting of a flatly subducted oceanic slab. The dioritic gneiss shows higher MgO (3.17%), Mg# (50), Cr (44‰), ...