Bull. Minéral. (1981), 104, 848-855.
Geothermometry of Karnataka charnockites
by Bhogisetti MAHABALESWAR and Channappa NAGANNA, Department of Geology, Bangalore University, 560056 Bangalore, India.
Géothermométrie des charnockites de Karnataka.
1. Introduction
2. Location
Charnockite is a wide spread orthopyroxene-bearing quartzo-felspathic rock in the Precambrian of Karnataka. It is associated with various types of supracrustals, arïbrthosites, gneisses and granites. Though some workers consider these rocks as resul¬ ting from recrystallisation of calc-alkaline suite of rocks, the available literature on the charnockites of Karnataka does not tell anything about the attain¬ ment of chemical equilibrium and temperature condi¬ tions of charnockite recrystallisation. Bearing this in mind, the authors have tried to establish the chemical equilibrium and temperature conditions of recrystalli¬ sation of charnockites of Sivasamudram area by conducting a detailed investigation on the chemistry of important co-existing mineral phases. This -area, being situated in Karnataka within the marginal tract, where the Nilgiri and Biligirirangana charnockites culminate, is considered by the authors as typical of these rocks within the state. Besides this a comparati¬ ve study is also made of the P-T estimates for char¬ nockites occurring in different parts of India.
The Sivasamudram area described in this investiga¬ tion lies in the Mandya district of Karnataka and is located 115 km. SW of Bangalore city. It is bounded
Map I.