Monazite geochronology and petrology of kyanite- and sillimanite-grade migmatites from the northwestern flank of the eastern Himalayan syntaxis

Palin, R.M. and Searle, M.P. and St-Onge, M.R. and Waters, D.J. and Roberts, N.M.W. and Horstwood, M.S.a. and Parrish, R.R. and Weller, O. M. and Chen, S. and Yang, J. (2014) Monazite geochronology and petrology of kyanite- and sillimanite-grade migmatites from the northwestern flank of the eastern Himalayan syntaxis. Gondwana Research, 26 (1). pp. 323-347. ISSN 1342-937X DOI https://doi.org/10.1016/j.gr.2013.06.022

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Abstract

A combined geochronological and petrological study of pelitic migmatites from the northwestern flank of the eastern Himalayan syntaxis has constrained the timing and P–T conditions of two high-grade metamorphic events that affected the south Lhasa block (Asian margin) and provides new insight into the tectonothermal evolution of the India–Asia collision. U(–Th)–Pb dating of in situ monazite shows that upper amphibolite-facies sillimanite-grade metamorphism and consequent partial melting occurred between c. 71 and 50 Ma at P–T conditions above 6.3 ± 1.2 kbar and 750 ± 30 °C. Further partial melting at upper amphibolite-facies kyanite-grade conditions occurred between c. 44 and 33 Ma at minimum P–T conditions of 10.4 ± 1.0 kbar and 698 ± 20 °C. These data are interpreted to record a south Lhasa block mid-crustal sillimanite-grade melting event in the Late Cretaceous to Early Eocene related to regional heat advection caused by coeval and prolonged emplacement of Gangdese batholith units. This was followed by a higher pressure and lower temperature kyanite-grade melting event during the Middle Eocene to Early Oligocene associated with deformation and crustal thickening in the south Lhasa block, coeval with kyanite-grade metamorphism along the Himalaya, as a result of the on-going India–Asia collision. These partially-melted crustal lithologies offer potential sources (or otherwise analogs for sources) for the Miocene emplacement of adakitic intrusions previously documented in the eastern Himalayan syntaxis region.

Item Type:	Article
Uncontrolled Keywords:	NILAREP
Subjects:	05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions:	05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Journal or Publication Title:	Gondwana Research
Volume:	26
Page Range:	pp. 323-347
Identification Number:	https://doi.org/10.1016/j.gr.2013.06.022
Depositing User:	Sarah Humbert
Date Deposited:	08 Apr 2017 00:42
Last Modified:	08 Apr 2017 00:42
URI:	http://eprints.esc.cam.ac.uk/id/eprint/3841

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