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

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Physical Conditions of Metamorphism of Calc-Silicate: Rocks from Koduru-Garividi, Andhra Pradesh


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1 Geological Department, The Associated Cement Companies Ltd., 121, Maharshi Karve Road, Bombay 400020, India
     

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Calc-silicate rocks with the assemblage calcite + K feldspar + quartz + wollastonite + diopsidess + scapolite + sphene ± grossular-andradite ± hornblende ± magnetite ± zoisite occur associated with metasedimentary manganese deposits at Garividi in Vijayanagaram district of Andhra Pradesh. From the mineral assemblages the temperature, pressure and composition of an ideally mixed H2O-CO2fluid phase during metamorphism have been derived for the following mineral reactions:

Calcite + Quartz = Wollastonite + CO2.

Grossular + Quartz = Anorthite + Wollastonite.

Tremolite + 3 Calcite + 2 Quartz = 5 Diopside + 3 CO2 + H2O.

For the analysed mineral compositions temperatures of the order of 700 ± 50°C and pressures of 7 ± 1 kb have been estimated. Mole fraction of H2O dnring metamorphism was at least 0.6. Fluid compositions appear to have been internally buffered during metamorphism.


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  • Physical Conditions of Metamorphism of Calc-Silicate: Rocks from Koduru-Garividi, Andhra Pradesh

Abstract Views: 225  |  PDF Views: 2

Authors

C. Sivaprakash
Geological Department, The Associated Cement Companies Ltd., 121, Maharshi Karve Road, Bombay 400020, India

Abstract


Calc-silicate rocks with the assemblage calcite + K feldspar + quartz + wollastonite + diopsidess + scapolite + sphene ± grossular-andradite ± hornblende ± magnetite ± zoisite occur associated with metasedimentary manganese deposits at Garividi in Vijayanagaram district of Andhra Pradesh. From the mineral assemblages the temperature, pressure and composition of an ideally mixed H2O-CO2fluid phase during metamorphism have been derived for the following mineral reactions:

Calcite + Quartz = Wollastonite + CO2.

Grossular + Quartz = Anorthite + Wollastonite.

Tremolite + 3 Calcite + 2 Quartz = 5 Diopside + 3 CO2 + H2O.

For the analysed mineral compositions temperatures of the order of 700 ± 50°C and pressures of 7 ± 1 kb have been estimated. Mole fraction of H2O dnring metamorphism was at least 0.6. Fluid compositions appear to have been internally buffered during metamorphism.