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Geochemistry of meta-anorthosites from Holénarasipur, Karnataka, South India

Kutty, TRN and Iyer, Anantha GV and Ramakrishnan, M (1984) Geochemistry of meta-anorthosites from Holénarasipur, Karnataka, South India. In: Lithos, 17 . pp. 317-328.

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Abstract

Geochemical and Rb---Sr isotope studies indicate that the meta-anorthosites of Holénarasipur, occurring as minor differentiates in ultramafic-mafic complex are igneous intrusives with cumulus character, emplaced around 3095 m.y. ago. The fine-grained nature is secondary; relict cumulus features are preserved in less deformed bodies. In major element chemistry, they compare well with other Archean anorthosites. Abundance levels of Ti, Zr, Y and P indicate the evolution through crystal fractionation of a parental magma; cumulus olivine and pyroxenes dominated chemistry for ultramafites, cumulus plagioclase and possibly clinopyroxene controlled chemistry for anorthosite-gabbros and cumulus magnetite in magnetite-gabbros. Magnetite is not an early cumulate. REE geochemistry is dominated by plagioclase with low abundance levels, slightly LREE enriched and variable positive Eu anomaly. Sr and Image values vary with An content in plagioclase. Isotopic studies show low initial Image (=0.7016) indicating that Rb---Sr isochron age represents the time of intrusion rather than the time of metamorphism.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Elsevier Science.
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 21 Aug 2009 09:15
Last Modified: 21 Aug 2009 09:15
URI: http://eprints.iisc.ernet.in/id/eprint/22297

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