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A Triassic to Jurassic arc in north Borneo : geochronology, geochemistry, and genesis of the Segama Valley Felsic Intrusions and the Sabah ophiolite.

Burton-Johnson, A. and Macpherson, C.G. and Millar, I.L. and Whitehouse, M.J. and Ottley, C.J. and Nowell, G.M. (2020) 'A Triassic to Jurassic arc in north Borneo : geochronology, geochemistry, and genesis of the Segama Valley Felsic Intrusions and the Sabah ophiolite.', Gondwana research., 84 . pp. 229-244.

Abstract

New field, geochemical, and geochronological data from the Segama Valley Felsic Intrusions (SVFI) of Sabah, north Borneo, shows them to be arc-derived tonalites; not windows or partial melts of a crystalline basement beneath Sabah. UPb zircon ages date emplacement in the Triassic and Jurassic: 241.1 ± 2.0 Ma, 250.7 ± 1.9 Ma, 178.7 ± 2.4 Ma, and 178.6 ± 1.3 Ma; contemporaneous with peaks in magmatism and detrital zircons in Sarawak and west Kalimantan (west Borneo). Isotopic data for Sr, Nd, and Pb from whole rocks, and for Hf and O from zircon all show mantle and/or MORB affinities indicating a mantle-derived origin. Enrichment of fluid mobile trace elements and trace element ratios indicate that the most likely setting for this is in a continuation of the Sundaland continental arc. There is no evidence in the field, geochemical, or zircon UPb data for continental basement in the Segama Valley region. The intrusive nature of the Segama Valley tonalites constrains the emplacement age of their supra-subduction zone host rocks to at least the Triassic. This new data expands the Triassic and Jurassic extent of Borneo and the Sundaland arc, and challenges models of Borneo's development predominantly through allochthonous terrane accretion in the Cretaceous. Instead, we propose a model of protracted autochthonous growth through supra-subduction zone crustal extension and associated magmatism.

Item Type:Article
Full text:(AM) Accepted Manuscript
Available under License - Creative Commons Attribution Non-commercial No Derivatives.
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1016/j.gr.2020.03.006
Publisher statement:© 2020 This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Date accepted:20 March 2020
Date deposited:15 May 2020
Date of first online publication:01 May 2020
Date first made open access:01 May 2021

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