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Shoshonitic enclaves in the high Sr/Y Nyemo pluton, southern Tibet: Implications for Oligocene magma mixing and the onset of extension of the southern Lhasa terrane

Wang, Zhenzhen and Zhao, Zhidan and Asimow, Paul D. and Liu, Dong and Zhu, Di-Cheng and Mo, Xuanxue and Wang, Qing and Zhang, Liangliang and Sheikh, Lawangin (2020) Shoshonitic enclaves in the high Sr/Y Nyemo pluton, southern Tibet: Implications for Oligocene magma mixing and the onset of extension of the southern Lhasa terrane. Lithos, 362-363 . Art. No. 105490. ISSN 0024-4937. https://resolver.caltech.edu/CaltechAUTHORS:20200320-085750658

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[img] MS Excel (Supplementary Table S1. Zircon U-Pb results of the shoshonitic enclaves and high Sr/Y host rocks in Nyemo pluton) - Supplemental Material
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[img] MS Excel (Supplementary Table S2. Zircon Lu-Hf isotopic compositions of shoshonitic enclaves and high Sr/Y host rocks in Nyemo pluton) - Supplemental Material
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[img] MS Excel (Supplementary Table S3. Chemical composition of amphibole from shoshonitic enclaves and high Sr/Y host rocks in Nyemo pluton) - Supplemental Material
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[img] MS Excel (Supplementary Table S4. The reference sources of post-collisional high Sr/Y rocks with adakitic affinity in southern Lhasa terrane in Fig. 6) - Supplemental Material
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Abstract

Post-collisional potassic and high Sr/Y magmatism in the Lhasa terrane provides critical constraints on the timing and mechanism of subduction of Indian lithosphere and its role in the uplift of the Tibetan Plateau. Here, we report whole-rock geochemistry, mineral geochemistry, zircon U Pb ages, and in situ zircon Hf isotope ratios for the Nyemo pluton, a representative example of such magmatism. The Nyemo pluton is composed of high Sr/Y host rocks and coeval shoshonitic mafic microgranular enclaves (MMEs). Whole-rock compositions of the host rocks and MMEs form linear trends in Harker diagrams, consistent with modification of both end-members by magma mixing. Although the main high Sr/Y phase of the pluton formed by partial melting of the lower crust of the thickened Lhasa terrane, the MMEs display abnormally enriched light rare earth elements, low whole-rock ε_(Nd)(t) and low zircon ε_(Hf)(t) that suggest derivation from low degree melting of hydrous and enriched mantle. Based on the occurrence of shoshonitic magma and high La/Yb and high Sr/Y with adakitic affinity host rocks around 30 Ma, the Nyemo pluton is best explained as a record of onset of extension that resulted from convective removal of the mantle lithosphere beneath Tibet in the Oligocene.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.lithos.2020.105490DOIArticle
ORCID:
AuthorORCID
Asimow, Paul D.0000-0001-6025-8925
Additional Information:© 2020 Published by Elsevier B.V. Received 4 December 2019, Revised 17 March 2020, Accepted 18 March 2020, Available online 20 March 2020. We thank editor Xian-Hua Li for handling this manuscript and two anonymous reviewers for constructive comments. We are grateful to Liyuan Xing and Yan Tang for assistance of fieldwork in Tibet and geochemical analyses. This research was supported by the Second Tibetan Plateau Scientific Expedition and Research (STEP) program (grant 2019QZKK0702), the National Key Research and Development Project of China (project 2016YFC0600304), the Natural Science Foundation of China (grant 41802058), the Fundamental Research Funds for the Central Universities (grants 2652018122 and QZ05201902), and the 111 Project of the Ministry of Science and Technology of China (projects BP0719021 and B18048). ZW acknowledges a fellowship from the China Scholarship Council (CSC No. 201806400019). The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funders:
Funding AgencyGrant Number
Second Tibetan Plateau Scientific Expedition and Research Program2019QZKK0702
National Key Research and Development Project of China2016YFC0600304
Natural Science Foundation of China41802058
Fundamental Research Funds for the Central Universities2652018122
Fundamental Research Funds for the Central UniversitiesQZ05201902
Ministry of Science and Technology (Taipei)BP0719021
Ministry of Science and Technology (Taipei)B18048
China Scholarship Council201806400019
Subject Keywords:High Sr/Y rocks; Shoshonitic MMEs; Magma mixing; Convective removal; Extension onset; Lhasa terrane; Tibetan plateau
Record Number:CaltechAUTHORS:20200320-085750658
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200320-085750658
Official Citation:Zhenzhen Wang, Zhidan Zhao, Paul D. Asimow, Dong Liu, Di-Cheng Zhu, Xuanxue Mo, Qing Wang, Liangliang Zhang, Lawangin Sheikh, Shoshonitic enclaves in the high Sr/Y Nyemo pluton, southern Tibet: Implications for Oligocene magma mixing and the onset of extension of the southern Lhasa terrane, Lithos, Volumes 362–363, 2020, 105490, ISSN 0024-4937, https://doi.org/10.1016/j.lithos.2020.105490. (http://www.sciencedirect.com/science/article/pii/S0024493720301274)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102019
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:20 Mar 2020 16:08
Last Modified:30 Mar 2020 17:40

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