Petrogenesis of the Late Archean (∼2.5 Ga) Na- and K-rich granitoids in the Zhongtiao-Wangwu region and its tectonic significance for the crustal evolution of the North China Craton

Abstract

Petrogenesis of coexisting Late Archean (∼2.5Ga) Na- and K-rich granitoids in the Zhongtiao-Wangwu region is significant for understanding the crustal evolution of the North China Craton (NCC). In this paper, we present new zircon U-Pb age, and whole-rock geochemical and isotope data on a ∼2.5Ga Na- and K-rich granitoid suite from the Zhongtiao-Wangwu region, southern NCC. The Na-rich granitoids (TTG) and K-rich granitoids (A-type granites) are zircon U-Pb dated to be 2.45Ga and 2.49Ga, respectively. Integrated geochemical data indicate that the TTG were formed by partial melting of the mafic lower crust, while the A-type granites were formed by partial melting of a TTG-like source in the shallower crust. The petrogenesis likely occurred under lithospheric delamination and the subsequent asthenospheric upwelling and mafic magma underplating. We proposed that the coeval occurrence of Na- and K-rich granitoids in the southern NCC is probably ascribed to the partial melting of continental crust at different depths, which could be an important way to induce the Archean crustal reworking and compositional changes at ∼2.5Ga.