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Sm-Nd ages of two meta-anorthosite complexes around Holenarsipur: Constraints on the antiquity of Archean Supracrustal rocks of the Dharwar craton

Rao, Bhaskar YJ and Kumar, Anil and Vrevsky, AB and Srinivasan, R and Iyer, Anantha GV (2000) Sm-Nd ages of two meta-anorthosite complexes around Holenarsipur: Constraints on the antiquity of Archean Supracrustal rocks of the Dharwar craton. In: Proceedings of the Indian Academy of Sciences Earth and Planetary Sciences, 109 (1). pp. 57-65.

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Abstract

Whole-rock Sm-Nd isochron ages are reported for two stratiform meta-anorthosite complexes emplaced into the Archean supracrustal-gneiss association in the amphibolite facies terrain around Holenarsipur, in the Dharwar craton, South India. While these metaperidotite-pyroxenite-gabbro-anorthosite complexes are petrologically and geochemically similar, they differ in the intensity of tectonic fabric developed during the late Archean (c. 2.5 Ga) deformation. They also differ in their whole-rock Sm-Nd isochron ages and initial Nd isotopic compositions: 3:285 _ 0:17 Ga, "Nd à 0:82 _ 0:78 for the Honnavalli metaanorthosite complex from a supracrustal enclave in the low-strain zone, and 2:495 _ 0:033 Ga, "Nd à ¡2:2_0:3 for the Dodkadnur meta-anorthosites from the high-strain southern arm of the Holenarsipur Supracrustal Belt (HSB). We interpret these results as indicating that the magmatic protoliths of both meta-anorthosite complexes were derived from a marginally depleted mantle at c.3.29 Ga but only the Dodkadnur rocks were isotopically reequilibrated on a cm-scale about 800Ma later presumably due to the development of strong penetrative fabrics in them during Late Archean thermotectonic event around 2.5 Ga. Our results set a younger age limit at c. 3.29 Ga for the supracrustal rocks of the HSB in the Dharwar craton.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Indian Academy of Sciences.
Keywords: Archean;anorthosite;Dharwar craton;Sm-Nd;Geochronology
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 09 Sep 2004
Last Modified: 19 Sep 2010 04:15
URI: http://eprints.iisc.ernet.in/id/eprint/1783

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