Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

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Whole Rock and Mineral Chemistry of Aluminous Granulites From the Eastern Ghats Granulite Belt, Andhra Pradesh


Affiliations
1 Department of Geology, Andhra University, Visakhapatnam-530 003, India
2 National Geophysical Research Institute, Hyderabad- 500 007, India
3 Department of Geosciences, Osaka City University, Osaka 558, Japan
4 Department of Geological Sciences, Yokohama National University, Yokohama, Japan
     

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The whole rock analyses confirm the basic to intermediate nature of the protolith (SiO2, > 53% - < 67%) with high alumina (highest 22.18%) and high K2O (∼ 4%). Metamorphic segregation as well as source rock compositions appear to have contributed -to the formation of high alumina granulites. The temperatures of metamorphism estimated using garnet - hypersthene/cordierite pairs range from 680-980°C, The gamet-cordierite reference temperatures with narrow range 700-750°C, indicate a pressure range of 5-7 kbar for the garnet-orthopyroxene-plagioclase-quartz assemblage in the aluminous granulites. Textural relationships of cordierite breakdown and reappearance of cordierite supplement the two generations of cordierite from aluminous granulites in the Eastern Ghats Granulites Belt.

Keywords

Geochemistry, Aluminous Granulites, P-T Estimates, Eastern Ghats Granulite Belt (EGGB), Andhra Pradesh.
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  • Whole Rock and Mineral Chemistry of Aluminous Granulites From the Eastern Ghats Granulite Belt, Andhra Pradesh

Abstract Views: 214  |  PDF Views: 2

Authors

A. T. Rao
Department of Geology, Andhra University, Visakhapatnam-530 003, India
V. Divakara Rao
National Geophysical Research Institute, Hyderabad- 500 007, India
M. Yoshida
Department of Geosciences, Osaka City University, Osaka 558, Japan
M. Arima
Department of Geological Sciences, Yokohama National University, Yokohama, Japan

Abstract


The whole rock analyses confirm the basic to intermediate nature of the protolith (SiO2, > 53% - < 67%) with high alumina (highest 22.18%) and high K2O (∼ 4%). Metamorphic segregation as well as source rock compositions appear to have contributed -to the formation of high alumina granulites. The temperatures of metamorphism estimated using garnet - hypersthene/cordierite pairs range from 680-980°C, The gamet-cordierite reference temperatures with narrow range 700-750°C, indicate a pressure range of 5-7 kbar for the garnet-orthopyroxene-plagioclase-quartz assemblage in the aluminous granulites. Textural relationships of cordierite breakdown and reappearance of cordierite supplement the two generations of cordierite from aluminous granulites in the Eastern Ghats Granulites Belt.

Keywords


Geochemistry, Aluminous Granulites, P-T Estimates, Eastern Ghats Granulite Belt (EGGB), Andhra Pradesh.