Zircon UPb geochronology and Hf isotopes of major lithologies from the Yishui Terrane: Implications for the crustal evolution of the Eastern Block, North China Craton

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• 作者：Meiling Wu^a ; Guochun Zhao^a ; ^{gzhao@hkucc.hku.hk} ; Min Sun^a ; Sanzhong Li^b ; Yanhong He^c ; Zhian Bao^c
• 关键词：Neoarchean ; Crustal accretion ; North China Craton ; Yishui Terrane ; Zircon
• 刊名：Lithos
• 出版年：2013
• 出版时间：June, 2013
• 年：2013
• 卷：170-171
• 期：Complete
• 页码：164-178
• 全文大小：2953 K

文摘

As an important component of the Western Shandong Complex in the Eastern Block of the North China Craton, the Yishui Terrane consists of Neoarchean high-grade supracrustal rocks, granitoid gneisses and charnockites. LA-ICP-MS zircon UPb dating and Hf isotopic analyses on these lithologies have been carried out and the results provide new insights into the Neoarchean crustal evolution of the Eastern Block of the North China Craton. New zircon dating results reveal that the magmatic precursors of the supracrustal metapelites and granitoid gneisses were generated at 2.54-2.53 Ga and 2.57-2.55 Ga, respectively, and the charnockites were emplaced contemporaneously around 2.56-2.53 Ga. Single metamorphic zircon grains and overgrowth rims from these rocks document consistent metamorphic ages at ~ 2.50 Ga, suggesting that the Yishui Terrane experienced a high-grade metamorphic event at the end of the Neoarchean. Detrital zircons from pelitic gneisses yield ²⁰⁷Pb/²⁰⁶Pb ages of 2.89-2.65 Ga, with a major age peak at ~ 2.53 Ga and a subordinate age peak at ~ 2.70 Ga, implying that the sedimentary protoliths of the pelitic gneisses may have been sourced from ~ 2.53 Ga rocks in the Yishui Terrane and ~ 2.70 Ga rocks in the adjacent Luxi Granite-Greenstone Terrane. Hf isotopic compositions show that the Neoarchean magmatic zircons have positive ¦Å_Hf(t) values ranging from + 1.4 to + 7.8 and depleted mantle model ages of 2.92-2.60 Ga with a prominent peak at 2.8-2.7 Ga, suggesting that the Neoarchean crust was derived mainly from juvenile sources and partly from the recycling of old continental crust in the Yishui area. Combined with previous data from the adjacent Luxi Granite-Greenstone Terrane and other complexes in the Eastern Block, it is concluded that the Neoarchean was an important period of crust accretion in the Eastern Block of the North China Craton.