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Type: Artigo
Title: Granulite Facies Metamorphism And Crust Melting In The Huai'an Terrane At Similar To 1.95 Ga, North China Craton: New Constraints From Geology, Zircon U-pb, Lu-hf Isotope And Metamorphic Conditions Of Granulites
Author: Wang
Hao-Zheng; Zhang
Hua-Feng; Zhai
Ming-Guo; Oliveira
Elson Paiva; Ni
Zhi-Yao; Zhao
Lei; Wu
Jia-Lin; Cui
Abstract: Geological implications of similar to 1.95 Ga and similar to 1.85 Ga metamorphic ages for HP granulites in the Huai'an terrane are still controversial, which have affected the crustal evolution models for the North China Craton. This study reports two geological sections in which distinct geological relationships of a quartz-dioritic and a tonalitic dike cutting through mafic HP granulite and granulite fades meta-sedimentary rocks are described. In these two sections, magmatic dikes, mafic HP granulites and meta-sedimentary rocks preserve conformable foliation to indicate their similar deformation history. The U-Pb dating and Lu-Hf isotopic analysis of zircons from metamorphic and meta-igneous rocks provide new constraints on the timing and mechanism of thermal events associated with metamorphic and deformation events. Both magmatic dikes were formed around similar to 1.95 Ga and overprinted by later metamorphic event during similar to 1.85 Ga. The S-type granite, at geological section (GS) 1, revealed its formation age was formed around 1959 +/- 34 Ma (n = 3, MSWD = 1.5), and overprinted by later metamorphic event at 1840 +/- 8 Ma (n = 10, MSWD = 1.2). Additionally, zircons from the mafic HP granulite in the GS2 are dominated by metamorphic ages of 1972 +/- 22 Ma (n = 6; MSWD = 0.03) with few grains recording an age of 1856 +/- 29 Ma (n = 3; MSWD = 0.17). In situ Lu-Hf analyses on zircons from the quartz-dioritic dike, tonalitic dike, mafic HP granulite and S-type granite, reveal that the magmatic dikes were derived from partial melting of similar to 2.0-2.2 Ga meta-basic rocks and the S-type granite was generated by melting of meta-sediments beyond 840 +/- 50 degrees C. It suggested that those meta-sediments were taken into the lower crust in a certain way at granulite fades conditions ca. 1.95 Ga ago. A clockwise P-T path acquired from mafic HP granulite revealed peak metamorphic conditions of 880-890 degrees C and 11-13 kbar. The temperature results recorded in the similar to 1.95 Ga zircons of mafic HP granulite, similar to those of high-pressure mineral assemblage in matrix, suggest that the HP granulite metamorphism was approximately 1.95 Ga ago. According to the results above, this contribution concludes that mafic and meta-sedimentary rocks were metamorphosed together under high-pressure granulite metamorphic conditions 1.95 Ga ago, followed by high-temperature granulite facies melting event that gave rise to granite and S-type granite at similar to 1.95 Ga. The granulite facies metamorphic rocks and magmatic dikes in the Huangtuyao graphite mine experienced the same evolution history after similar to 1.95 Ga. The mafic and pelitic HP granulites in the Huai'an terrane are interpreted to be collisional products of the Paleoproterozoic cratonization of the NCC. (C) 2016 Elsevier B.V. All rights reserved.
Subject: Hp And Ht Granulite Facies Metamorphism
1.95 Ga Tectono-thermal Event
Huai'an Terrane
North China Craton
Editor: Elsevier Science BV
Rights: fechado
Identifier DOI: 10.1016/j.precamres.2016.09.012
Date Issue: 2016
Appears in Collections:Unicamp - Artigos e Outros Documentos

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