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Perovskite U-Pb and Sr-Nd isotopic perspectives on melilitite magmatism and outward growth of the Tibetan Plateau.

Liu, Dong and Zhao, Zhidan and Niu, Yaoling and Zhu, Di-Cheng and Li, Xian-Hua (2018) 'Perovskite U-Pb and Sr-Nd isotopic perspectives on melilitite magmatism and outward growth of the Tibetan Plateau.', Geology., 46 (12). pp. 1027-1030.

Abstract

Mantle-derived alkaline magmatism along major strike-slip faults provides unique insights into the lateral growth of the Tibetan Plateau. Here we use the geochemistry of perovskites from the West Qinling melilitite to probe into the nature and dynamics of sub-lithospheric mantle beneath the northeastern Tibetan Plateau. The texture and chemical composition of perovskites indicate their early crystallization from a CO2-rich melilitite magma. Most perovskite crystals have moderately depleted Sr-Nd isotopic compositions, whereas a few grains exhibit high 87Sr/86Sri and low εNd(t). Together with the bulk-rock geochemistry of the melilitite, the perovskite Sr-Nd isotope data imply that the primary magma parental to the melilitite was most likely derived from seafloor subduction–modified asthenosphere and underwent interaction with lithospheric mantle during ascent. In situ U-Pb dating of the perovskites demonstrates the temporal correlation between the melilitite magmatism and Kunlun strike-slip faulting in the early Miocene. These findings indicate the fundamental role of India-Asia convergence in driving outward plateau growth through strike-slip extrusion and in reactivating long-lived lithospheric zones of weakness for evacuating low-volume asthenospheric melts.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1130/G45329.1
Date accepted:23 September 2018
Date deposited:16 October 2018
Date of first online publication:12 October 2018
Date first made open access:12 October 2019

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