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The geology and tectonics of central Bhutan

Greenwood, Lucy V.; Argles, Tom W.; Parrish, Randall R.; Harris, Nigel B. W. and Warren, Clare (2016). The geology and tectonics of central Bhutan. Journal of the Geological Society, 173(2) pp. 352–369.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1144/jgs2015-031
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Abstract

Lithotectonic mapping, metamorphic observations and U–Pb zircon ages underpin a substantial revision of central Bhutan geology, notably a more extensive and continuous outcrop of the Tethyan Sedimentary Series (TSS) than previously mapped. Metamorphic grade in the TSS increases downward towards a basal north-vergent tectonic contact with the underlying Greater Himalayan Series (GHS), interpreted as a southward continuation of the South Tibetan Detachment (STD). Miocene (c. 17–20 Ma) leucogranite sheets are associated with the STD in this region but appear to diminish southwards. Two leucogranite dykes that cross-cut TSS structures yield ages of 17.8 ± 0.2 and 17.9 ± 0.5 Ma. A 500 ± 4 Ma (U–Pb zircon) metamorphosed ash bed in the Pele La Group within the psammite-dominated lower TSS yields the first direct isotopic age for the TSS in the eastern Himalaya, confirming existing age constraints from detrital zircon and fossil studies. A continuation of the Paro metasedimentary unit underlying the GHS was mapped near Wangdue Phodrang. Our observations, notably the exposure of a wholly ductile STD so far south and the significance of large nappe-like structures in the TSS, prompt a major revision to the geological map of the Bhutan Himalaya and require a reassessment of tectonic interpretations of the Bhutan Himalaya.

Item Type: Journal Item
Copyright Holders: 2015 The Authors
ISSN: 2041-479X
Project Funding Details:
Funded Project NameProject IDFunding Body
Orogenesis in the Eastern Himalaya: A study of Structure, Geochronology and Metamorphism in BhutanS168BGS/BUFI and OU
Keywords: Himalayan geology; Bhutan; South Tibetan Detachment; Tethyan Sedimentary series; leucogranite; geochronology
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Related URLs:
Item ID: 44725
Depositing User: Thomas Argles
Date Deposited: 05 Nov 2015 10:45
Last Modified: 08 Dec 2018 05:58
URI: http://oro.open.ac.uk/id/eprint/44725
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