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Paleogene crustal anatexis and metamorphism in Lhasa terrane, eastern Himalayan syntaxis: evidence from U–Pb zircon ages and Hf isotopic compositions of the Nyingchi Complex

Guo, Liang; Zhang, Hong-Fei ; Harris, Nigel; Parrish, Randall; Xu, Wang-Chun and Shi, Zhang-Liang (2012). Paleogene crustal anatexis and metamorphism in Lhasa terrane, eastern Himalayan syntaxis: evidence from U–Pb zircon ages and Hf isotopic compositions of the Nyingchi Complex. Gondwana Research, 21(1) pp. 100–111.

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DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1016/j.gr.2011.03.002
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Abstract

In the eastern Himalayan syntaxis, the southern Lhasa terrane is dominated by middle- to high-grade metamorphic rocks (Nyingchi Complex), which are intruded by felsic melts. U–Pb zircon dating and zircon Hf isotopic composition of these metamorphic and magmatic rocks provide important constraints on the tectono-thermal evolution of the Lhasa terrane during convergent process between Indian and Asian continents. U–Pb zircon data for an orthogneiss intruding the Nyingchi Complex yield a protolith magma crystallization age of 83.4 ± 1.2 Ma, with metamorphic ages of 65–46 Ma. This orthogneiss is characterized by positive εHf(t) values of + 8.3 and young Hf model ages of ~ 0.6 Ga, indicating a derivation primarily from a depleted-mantle or juvenile crustal source. Zircons from a quartz diorite yield a magma crystallization age of 63.1 ± 0.6 Ma, with εHf(t) values of − 8.2 to − 2.7, suggesting that this magma was sourced from partial melting of older crustal materials. Zircon cores from a foliated biotite granite show ages ranging from 347 to 2690 Ma, with age peaks at 347–403 Ma, 461–648 Ma and 1013–1183 Ma; their zircon εHf(t) values range from − 30.6 to + 6.9. Both the U–Pb ages and Hf isotopic composition of the zircon cores are similar to those of detrital zircons from the Nyingchi Complex paragneiss, implying that the granite was derived from anatexis of the Nyingchi Complex metasediments. The zircon rims from the granite indicate crustal anatexis at 64.4 ± 0.7 Ma and subsequent metamorphism at 55.1 ± 1.3 and 41.4 ± 2.3 Ma. Our results suggest that the late Cretaceous magmatism in the southern Lhasa terrane resulted from Neo-Tethys oceanic slab subduction and we infer that Paleocene crustal anatexis and metamorphism were related to the thermal perturbation caused by rollback of the northward subducted Neo-Tethyan oceanic slab.

Item Type: Journal Article
Copyright Holders: 2011 International Association for Gondwana Research
ISSN: 1342-937X
Project Funding Details:
Funded Project NameProject IDFunding Body
Not SetNot SetNatural Science Foundation of China (grants: 40773019 and 40821061)
Not SetNot SetProgram for Changjiang Scholars and Innovative Research Team in University (Grant B07039)
Not SetNot SetSinoProb 04-02 (2101105)
Keywords: U–Pb zircon dating; zircon Hf isotope; Nyingchi Complex crustal anatexis; eastern Himalayan syntaxis
Academic Unit/Department: Science > Environment, Earth and Ecosystems
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 28478
Depositing User: Nigel Harris
Date Deposited: 07 Apr 2011 15:11
Last Modified: 27 Oct 2012 17:06
URI: http://oro.open.ac.uk/id/eprint/28478
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