Zircon U-Pb Ages and Hf Isotopic Composition of Wenquan Rapakivi Granites from Northwestern Hebei Province

摘要

Using LA-MC-ICP-MS method, this paper presents zircon U-Pb ages and Hf isotopic composition of Wenquan rapakivi granites from northwestern Hebei province. 22 analytical spots yield ~(207)pb/ ~(206)pb ages ranging from 1743.52 to 1764.81 Ma with weighted mean ~(207)Pb/ ~(206)Pb ages of 1749.5±3.4Ma(MSWD =0.53). The dating results imply that Wenquan rapakivi granites formed in Paleoproterozoic is compatible with the post-orogenic extensional tectonic setting of the continent-continent collision between the Western and Eastern blocks of the North China craton at 1850Ma. ε Hf(t) values show a minor range from-4.68 to 5.02, with a mean value of-2.31. Two-stage Hf model ages range from 2122 to 2708 Ma, focusing on 2500 to 2708 Ma. These Hf isotopic features indicate that Wenquan rapakivi granites were mainly derived from recycling Neoarchean crust material, with a little join of mantle composition.