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Geochronology and Geochemistry of Archean TTG and Tremolite Schist Xenoliths in Yemadong Complex: Evidence for ≥3.0 Ga Archean Continental Crust in Kongling High-Grade Metamorphic Terrane, Yangtze Craton, China

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Wuhan Center of China Geological Survey, Wuhan 430205, China
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Central South China Innovation Center for Geosciences, Wuhan 430205, China
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Research Center of Granitic Diagenesis and Mineralization, China Geological Survey, Wuhan 430205, China
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Institute of Geological Survey, China University of Geosciences, Wuhan 430074, China
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Hubei Geological Survey, Wuhan 430034, China
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Guangxi Regional Geological Survey, Guilin 541001, China
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Author to whom correspondence should be addressed.
Minerals 2019, 9(11), 689; https://doi.org/10.3390/min9110689
Received: 28 September 2019 / Revised: 19 October 2019 / Accepted: 29 October 2019 / Published: 8 November 2019
(This article belongs to the Special Issue Geochemistry of Granites and Granitic Pegmatites)
The origin and significance of the tonalite–trondhjemite–granodiorite (TTG) units and the familiar metabasite xenoliths they host in the Yangtze Craton, China, remain controversial, and resolving these issues is important if we are to understand the evolution of the early Yangtze Craton. We focused on biotite–tremolite schist xenoliths in the Archean TTG units of the Kongling high-grade metamorphic terrane, and U–Pb dating of their zircons yielded 207Pb/206Pb ages of ca. 3.00 Ga, which provides a minimum age for the formation of the pre-metamorphic basic igneous rock. The host TTGs and late intrusive granitic dikes yield three groups of upper intercept ages at 2.87–2.88, 2.91–2.94, and 3.07 Ga, and a concordant age at 2.94 Ga, which suggest that the Yangtze continental nucleus underwent three important metamorphic–magmatic events in the Mesoarchean at ca. 3.00, 2.94, and 2.87 Ga. The biotite–tremolite schists have high ratios of K2O/Na2O and high contents of CaO, Cr, and Ni, thus showing the characteristics of high-K calc-alkaline island-arc volcanic rocks (basalt–andesite) that form by the partial melting of subducted oceanic crust. The data also provide further proof that a Mesoarchean metamorphic basement exists in the Yangtze Plate. Derivation of the magmatic protoliths of the biotite–tremolite schist enclaves from an oceanic crust during slab subduction, and the presence of these xenoliths within the TTG suite, indicate the existence of the initiation of plate tectonics during the Mesoarchean (≤2.94 Ga). View Full-Text
Keywords: Archean TTG; tremolite schist; Yemadong complex; Kongling high-grade metamorphic terrane; Yangtze craton Archean TTG; tremolite schist; Yemadong complex; Kongling high-grade metamorphic terrane; Yangtze craton
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Wei, Y.; Zhou, W.; Hu, Z.; Li, H.; Huang, X.; Zhao, X.; Xu, D. Geochronology and Geochemistry of Archean TTG and Tremolite Schist Xenoliths in Yemadong Complex: Evidence for ≥3.0 Ga Archean Continental Crust in Kongling High-Grade Metamorphic Terrane, Yangtze Craton, China. Minerals 2019, 9, 689.

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