华北克拉通辽南地块太古宙地壳增生与再造OA

Late Neoarchean granitoid gneisses are widely distributed in the Early Precambrian metamorphic base-ment of the Liaonan Block,the North China Craton(NCC),and record important information on the formation and evolution of the continental crust in the Early Precambrian.In this study,we present zircon LA-ICP-MS U-Pb ages,trace element compositions,and Lu-Hf isotopic data from four granitoid gneiss samples collected from the Liaonan Block.Most zircons exhibit oscillatory zoning and high Th/U ratios(0.18～2.21),along with REE pat-terns characterized by depleted LREEs and enriched HREEs,consistent with a magmatic origin.The 207Pb/206Pb weighted mean ages of the four granitoid samples are 2 529±10 Ma(MSWD=0.12,n=14),2 475±27 Ma(MSWD=3.1,n=13),2 502±15 Ma(MSWD=2.7,n=14),and 2 478±8 Ma(MSWD=0.81,n=25),respectively,recording the magmatic events related to crustal differentiation during the late Neoarchean.Zircon Hf isotopic compositions show positive εHf(t)values(+0.11 to+5.29),with two-stage model ages(tDM2)ranging from 2.9 to 2.7 Ga,suggesting the granitoids were derived mainly from partial melting of juvenile crust formed during this period.A few zircons yield negative εHf(t)values(-3.2 to-0.8)and older tDM2 ages of 3.12～2.90 Ga,reflecting the involvement of ancient reworked continental crustal components older than 2.9 Ga.Combi-ning the new results with published zircon Hf isotope data,it has been demonstrated that the Liaonan Block experi-enced major crustal growth during 2.9～2.7 Ga and crustal reworking at 2.5 Ga and 2.47 Ga,which were driven by upwelling mantle.The resulting widespread potassic granitic rocks signify the stabilization and cratonization of the block.