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Mineral chemistry and reaction textures in metabasites from the Eastern Ghats belt, India and their implications

Published online by Cambridge University Press:  05 July 2018

Somnath Dasgupta
Affiliation:
Department of Geological Sciences, Jadavpur University, Calcutta-700 032, India
Pulak Sengupta
Affiliation:
Department of Geological Sciences, Jadavpur University, Calcutta-700 032, India
A. Mondal
Affiliation:
Department of Geological Sciences, Jadavpur University, Calcutta-700 032, India
M. Fukuoka
Affiliation:
Department of Geological Sciences, Jadavpur University, Calcutta-700 032, India

Abstract

Three types of mafic granulites, namely two pyroxene-plagioclase granutite (MG), two pyroxeneplagioclase-garnet granulite (GMG) and spinel-olivine-plagioclase-two pyroxene granulite (SMG) are exposed at Sunkarimetta, Eastern Ghats belt, India. The marie granulites exhibit a foliation concordant with that in associated granulite facies quartzofeldspathic gneisses. Textural characteristics and mineral chemical data suggest the following mineral reactions: olivine + plagioclase = spinel + orthopyroxene + clinopyroxene (SMG), orthopyroxene + plagioclase = garnet + quartz (GMG), clinopyroxene + plagioclase = garnet + quartz (GMG) and plagioclase + hemoilmenite + quartz = garnet + ilmenite + 02 (GMG). Geothermobarometry indicates maximum P-T conditions of metamorphism at c. 8.5 kbar, 950°C The marie granulites later suffered nearly isobaric cooling to c. 7.5 kbar, 750°C Bulk compositional characteristics suggest that SMG is of cumulate origin. The protoliths of the mafic granulites, emplaced at c. 32 km depth, are probably responsible for thermal perturbation causing granulite facies metamorphism of the enclosing rocks.

Type
Mineralogy
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1993

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Footnotes

*

Present address: Department of Earth and Planetary Sciences, Kyushu University Fukuoka 812, Japan.

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