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

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• 作者：Lilin Du^a ; ^{dulilin7310@cags.ac.cn} ; Chonghui Yang^a ; Wei Wang^b ; Liudong Ren^a ; Yusheng Wan^a ; ^c ; Jiashan Wu^a ; Lei Zhao^b ; Huixia Song^a ; Yuansheng Geng^a ; Kejun Hou^d
• 关键词：Granite porphyry ; The Wutai area ; Zircon U&ndash ; Pb dating ; Hf isotopes ; A-type granite ; Rifting setting
• 刊名：Journal of Asian Earth Sciences
• 出版年：2013
• 出版时间：10 August, 2013
• 年：2013
• 卷：72
• 期：Complete
• 页码：190-202
• 全文大小：4230 K

文摘

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 ²⁰⁷Pb/²⁰⁶Pb age of 2137 ¡À 9 Ma, which indicates that the granite was emplaced in the middle Paleoproterozoic. The granite porphyry is enriched in SiO₂, REEs (except Eu), Zr, Nb, Ga, Y and Zn, and depleted in MgO, CaO, Al₂O₃, Sr, Ba, V, Cr and Ni, with high FeO^*/MgO ratios. With the zircon saturation temperatures ranging from 856 to 895 ¡ãC 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 ¦Å_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.