Metamorphism of cordierite gneisses from the Bangalore region of the Indian Archean |
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Authors: | N.B.W Harris S Jayaram |
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Affiliation: | 1. Department of Earth Sciences, Open University, Miltou Keynes, England;2. Department of Mines and Geology, Race Course Road, Bangalore, India |
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Abstract: | Mineral compositions from cordierite-bearing metasedimentary enclaves adjacent to the Closepet granite in the Bangalore region of the South Indian Craton indicate peak metamorphism in the range 4.5–5.0 kb, 690–730°C. PH2O is found to decrease towards the south and those assemblages which lie south of the charnockite line are formed under conditions of PH2O < 0.3 Ptotal. 250 km north Bangalore, andalusite-bearing assemblages from the northern margin of the Closepet granite indicate peak metamorphic conditions in the range 2.6–3.8 kb, 520–620°C. The inferred piezotacrmic array is strongly convex towards the temperature axis and may represent a transient geotherm in the upper crust related to the emplacement of the Closepet granite or to volatile activity along the margins of the granite. |
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