Geochemistry and zircon geochronology of the Neoarchean volcano-sedimentary sequence along the northern margin of the Nilgiri Block, southern India

Samuel, Vinod O and Santosh, M and Yang, Qiong-Yan and Sajeev, K (2016) Geochemistry and zircon geochronology of the Neoarchean volcano-sedimentary sequence along the northern margin of the Nilgiri Block, southern India. In: LITHOS, 263 . pp. 257-273.

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Abstract

The Nilgiri Block is one of the major Archean crustal blocks that define the tectonic framework of southern India. Here we report geologic, petrologic, geochemical, and zircon U-Pb,-REE, and -Lu-Hf data of a highly metamorphosed and disrupted sequence of amphibolite, meta-gabbro, websterite, volcanic tuff, meta-sediment, and banded iron formation (BIF) from the northern fringe of the Nilgiri Block. Geochemically, the amphibolite shows altered ocean floor basalt signature, whereas the meta-gabbro and the websterite samples form part of a volcanic arc. The metamorphosed volcanic tuff shows subalkaline rhyolitic signature. U-Pb isotope analysis of zircon grains from the volcanic tuff and meta-gabbro shows Pb-207/Pb-206 ages of 2490 +/- 12 Ma and 2448 +/- 16 Ma, respectively. Zircons from the meta-sediments show an age range of 2563 +/- 33 Ma to 2447 +/- 34 Ma. The dominantly positive epsilon Hf (t) values of the zircons in the analyzed rock suite suggest that the magmas from which the zircons crystallized evolved from a Neoarchean depleted mantle source. The Hf model ages (T-DM) of volcanic tuff, meta-sediment and meta-gabbro samples are ranging between 2908-2706 Ma, 2849-2682 Ma, and 2743-2607 Ma, respectively. The ca. 2500 Ma ages for the arc-related magmatic rock suite identified along the northern periphery of Nilgiri Block suggest prominent Neoarchean arc magmatism and early Paleoproterozoic convergent margin processes contributing to the early Precambrian crustal growth in Peninsular India. (C) 2016 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Publication:	LITHOS
Additional Information:	Copy right for this article belongs to the ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
Department/Centre:	Division of Mechanical Sciences > Centre for Earth Sciences
Date Deposited:	03 Dec 2016 06:47
Last Modified:	03 Dec 2016 06:47
URI:	http://eprints.iisc.ac.in/id/eprint/55323

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