Garnet pyroxenite from Nilgiri Block, southern India: Vestiges of a Neoarchean volcanic arc

Samuel, Vinod O and Kwon, Sanghoon and Santosh, M and Sajeev, K (2018) Garnet pyroxenite from Nilgiri Block, southern India: Vestiges of a Neoarchean volcanic arc. In: LITHOS, 310 . pp. 120-135.

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Abstract

Southern peninsular India preserves records of Late Neoarchean Early Paleoproterozoic continental building and cratonization. A transect from the Paleoarchean Dharwar Craton to the Neoarchean arc magmatic complex in the Nilgiri Block across the intervening Moyar Suture Zone reveals an arc-accretionary complex composed of banded iron formation (BIF), amphibolite, metatuff, garnet-kyanite schist, metagabbro, pyroxenite and charnockite. Here we investigate the petrology, geochronology and petrogenesis of the pyroxenite and garnet-clinopyroxenite. The pyroxenite is mainly composed of orthopyroxene and clinopyroxene with local domains/pockets enriched in a clinopyroxene-gamet assemblage. Thermobarometric calculations and phase equilibria modeling suggest that the orthopyroxene-and clinopyroxene-rich domains formed at 900-1000 degrees C, 1-1.2 GPa whereas the garnet-and clinopyroxene-rich domains record higher pressure of about 1.8-2 GPa at similar temperature conditions (900-1000 degrees C). Zircon U-Pb SHRIMP dating show weighted mean Pb-207-Pb-206 age of 2532 +/- 22 Ma, with metamorphic overgrowth at 2520 +/- 27 Ma and 2478 +/- 27 Ma. We propose a tectonic model involving decoupling and break-off of the oceanic plate along the southern flanks of the Dharwar Craton, which initiated oceanic plate subduction. Slab melting eventually built the Nilgiri volcanic arc on top of the overriding plate along the flanks of the Dharwar Craton. Our study supports an active plate tectonic regime at the end of the Archean Era, aiding in the growth of paleo-continents and their assembly into stable cratons. (C) 2018 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Publication:	LITHOS
Publisher:	ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
Additional Information:	Copyright of this article belong to ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
Department/Centre:	Division of Mechanical Sciences > Centre for Earth Sciences
Date Deposited:	26 Jul 2018 15:08
Last Modified:	26 Jul 2018 15:08
URI:	http://eprints.iisc.ac.in/id/eprint/60304

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