The generation and emplacement of Closepet granite during Late Archean granulite metamorphism in southeastern Karnataka

Jayananda,, M. and Mahabaleswar, B. (1991) The generation and emplacement of Closepet granite during Late Archean granulite metamorphism in southeastern Karnataka. Journal of the Geological Society of India, 38 (4). pp. 418-26. ISSN 0016-7622

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Official URL: http://www.geosocindia.org/index.php/jgsi/article/...

Abstract

In the amphibolite-​granulite facies transition zone of southeastern Karnataka (India)​, a typical metamorphic-​anatectic sequence is exposed. In this zone, large-​scale melting of basement gneisses during Late Archean granulite metamorphism has led to the generation of the Closepet granite. Field evidence suggests a space-​time relation between charnockite development, migmatite formation, and generation of the Closepet granite. This is also substantiated by U-​Pb and Pb-​Pb isotope data. At the southern end of the Closepet granite, conventional petrol. data and O isotope work suggest that CO2-​rich fluid phase of subcrustal origin was instrumental in granulite metamorphism and anatexis. The Southern Closepet granite is highly heterogeneous and displays a very complex polyphase internal structure. Based on texture and cross cutting relations, 4 major granite phases are recognized. The pressure-​temp. conditions inferred from mineralogic geothermometry and geobarometry indicate that granite melts were generated at midcrustal levels. The spatial assocn. of migmatites and gradational contacts suggest that the granite in the transition zone did not rise far from its source region. The occurrence of ductile mylonites and augen gneisses further north of the study area indicate a major shear control in the generation of the Closepet granite. A model involving collision of eastern and western crustal blocks is the possible tectonic set-​up for evolution of the Closepet granite.

Item Type: Article
Uncontrolled Keywords: Closepet Granite, Anatexis, Migmatites, Charnockite, CO2 Fluid Phase, Karnataka.
Subjects: Faculty of Science > Earth Sciences > Geology
Divisions: Jnana Bharathi / Central College Campus > Department of Geology
Depositing User: Ms. Rekha Jadhav
Date Deposited: 23 Sep 2016 07:28
Last Modified: 23 Sep 2016 07:28
URI: http://eprints-bangaloreuniversity.in/id/eprint/6011

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