Paleoproterozoic rifting of the North China Craton: Geochemical and zircon Hf isotopic evidence from the 2137 Ma Huangjinshan A-type granite porphyry in the Wutai area

Abstract SHRIMP zircon U–Pb dating of the Huangjinshan granite porphyry in the Wutai area, North China Craton (NCC) yielded concordant ages, with a weighted mean 207 Pb/ 206 Pb age of 2137 ± 9 Ma, which indicates that the granite was emplaced in the middle Paleoproterozoic. The granite porphyry is enriched in SiO 2 , REEs (except Eu), Zr, Nb, Ga, Y and Zn, and depleted in MgO, CaO, Al 2 O 3 , Sr, Ba, V, Cr and Ni, with high FeO * /MgO ratios. With the zircon saturation temperatures ranging from 856 to 895 °C and a lack on detected inherited zircon, this indicates it is a ‘hot’ A-type granite, of the type emplaced in anorogenic or extensional settings with high heat flow. Zircons in the granite porphyry have e Hf ( t ) values ranging from −1.72 to +1.84, and Hf model T DM1 ages of 2429–2554 Ma. The Hf isotopes indicate source of the granites was pre-Neoarchean continental crust mixed with mafic rocks derived from depleted mantle, or directly from the partial melting of ca. 2.5 Ga crust. Given that there are no syn-plutonic gabbro enclaves in the Huangjinshan granite porphyry, it is preferred that it originated mainly from partial melting of ca. 2.5 Ga upper crust without mixing with mantle-derived magma. 2.2–2.0 Ga volcanic and plutonic rocks, which exhibit bimodal magma characteristics emplacing in rifting setting, are abundant in the central NCC. The results presented here are further evidence for that 2.2–2.0 Ga is an important stage of Paleoproterozoic rifting in the central NCC.