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ABSTRACT. We present an integrated study of zircon U-Pb dating and O-Hf isotopic analyses combined with whole-rock geochemistry and Nd isotopic systematics on widespread late Neoarchean syenogranites (Qidashan Pluton) and other granitoids (granodiorite, quartz monzonite, monzogranite) in the Anshan-Benxi area, eastern North China Craton. All these rocks were emplaced at ca. 2.5 Ga according to SHRIMP zircon U-Pb dating and other indirect methods. The syenogranites are characterized by high SiO2 and K2O /Na2O and low CaO, FeOt, MgO, TiO2 and P2O5. However, they differ in trace element and REE compositions and can be roughly subdivided into two types. Type 1 syenogranite has strongly negative Eu anomalies and Ba depletion, with large variations of LREE to HREE differentiation; type 2 syenogranite has no negative Eu anomaly and Ba depletion. Other granitoids are also rich in K2O and show similar trace element and REE compositional features as the type 2 syenogranite. Most syenogranite samples have whole-rock εNd(t) values of -10.5 to -2.7 and tDM(Nd) ages of 2.96 to 3.90 Ga, whereas the other granitoids have εNd(t) values of -5.2 to -2.2 and tDM(Nd) ages of 2.95 to 3.19 Ga. Magmatic zircon from the syenogranites has εHf(t), values and Hf crustal model ages ranging mainly from -11.0 to +4.4 and 2.70 to 3.46 Ga, respectively; those from other granitoids have εHf(t) values and Hf crustal model ages of -16.0 to + 2.4 and 2.81 to 3.72 Ga, respectively. All these rocks contain Meso- to Paleoarchean xenocrystic zircon grains with εHf(t) values and Hf crustal model ages ranging from -14.3 to +8.3 and 2.79 to 3.93 Ga, respectively. Decoupling of wholerock Nd and Hf-in-zircon isotopes occurs in some samples. Most low-U magmatic zircon (U<200 ppm) from all granitoids has δ18O values in the range of +4 to +7.2 permil, whereas high-U magmatic zircon (U≥200 ppm) shows a larger variation with the lowest δ18O value being 1.6. The xenocrystic zircon grains have δ18O values in the normal range of Archean magmatic zircon. Combined with previous studies, we conclude that the 2.5 Ga granitoids formed by recycling of mature, old continental crust, including metasedimentary sources, probably in an extensional tectonic environment. [ABSTRACT FROM AUTHOR]