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Gangdese magmatism in southern Tibet and India-Asia convergence since 120 Ma

Zhu Dicheng, Wang Qing, Sun-Lin Chung, Peter A. Cawood and Zhao Zhidan
Gangdese magmatism in southern Tibet and India-Asia convergence since 120 Ma (in Himalayan tectonics; a modern synthesis, Peter J. Treloar (editor) and Michael P. Searle (editor))
Special Publication - Geological Society of London (October 2018) 483 (1): 583-604

Abstract

A compilation of 290 zircon U-Pb ages of intrusive rocks indicates that the Gangdese Batholith in southern Tibet was emplaced from c. 210 Ma to c. 10 Ma. Two intense magmatic pulses within the batholith occur at: (1) 90 + or - 5 Ma, which is restricted to 89-94 degrees E in the eastern segment of the southern Lhasa subterrane; and (2) 50 + or - 3 Ma, which is widespread across the entire southern Lhasa subterrane. The latter pulse was followed by a phase of widespread but volumetrically small, dominantly felsic adakitic intrusive rocks at 16 + or - 2 Ma. The Linzizong volcanism in the Linzhou Basin was active from 60.2 to 52.3 Ma, rather than 69-44 Ma as previously estimated. During 120-75 Ma, Gangdese Batholith magmatism migrated from south to north, arguing against rollback of the downgoing, north-dipping Neo-Tethyan oceanic lithosphere for the generation of the 90 + or - 5 Ma magmatic pulse. Petrological, geochemical and metamorphic data indicate that this pulse was likely to have been generated through subduction of the Neo-Tethyan oceanic ridge lithosphere. Subsequent Gangdese Batholith magmatism propagated both south and north during 70-45 Ma, and finally concentrated at the southern margin of the Lhasa Terrane at 45-30 Ma. The enhanced mafic magmatism since c. 70 Ma, magmatic flare-up with compositional diversity at c. 51 Ma and increased magmatic temperature at 52-50 Ma are interpreted as the consequences of slab rollback from c. 70 Ma and slab breakoff of the Neo-Tethyan oceanic lithosphere that began at c. 53 Ma. The India-Asia convergence was driven by Neo-Tethyan subduction with a normal rate of convergence at 120-95 Ma, ridge subduction at 95-85 Ma, then subduction of a young and buoyant oceanic lithosphere after ridge subduction with rate deceleration at 84-67 Ma, Deccan plume activity and slab rollback with rate acceleration at 67-51 Ma, slab breakoff for sudden drop of the convergence rate at c. 51 Ma, and finally the descent of the high-density Indian continental lithosphere beneath Asia since c. 50 Ma. Supplementary material: U-Pb age data of detrital zircons from the uppermost Shexing Formation sandstones in Maxiang are available at https://doi.org/10.6084/m9.figshare.c.4267850


ISSN: 0305-8719
Serial Title: Special Publication - Geological Society of London
Serial Volume: 483
Serial Issue: 1
Title: Gangdese magmatism in southern Tibet and India-Asia convergence since 120 Ma
Title: Himalayan tectonics; a modern synthesis
Author(s): Zhu DichengWang QingChung, Sun-LinCawood, Peter A.Zhao Zhidan
Author(s): Treloar, Peter J.editor
Author(s): Searle, Michael P.editor
Affiliation: China University of Geosciences, State Key Laboratory of Geological Processes and Mineral Resources, Beijing, China
Affiliation: Kingston University, Department of Geography, Geology and the Environment, London, United Kingdom
Pages: 583-604
Published: 20181024
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 148
Accession Number: 2019-005122
Categories: Solid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., strat. col., geol. sketch maps
N29°00'00" - N30°30'00", E85°00'00" - E95°00'00"
Secondary Affiliation: Academia Sinica, TWN, TaiwanMonash University, AUS, Australia
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201905
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