1 - Cochin University of Science and Technology

occurrence), is estimated to be 530°C. This is comparable to
the alk-Fs (av)-plag (av) temperature (527°C) obtained for
the granite sample at 5 Kbar pressure. Neomineralisation
associated with migmatisation and granitic emplacement is
therefore, fixed at 532°C (mean).
Core pressures estimated for the khondalites and
associated gneisses using Ghent (1976), Newton & Haselton
( 1981) , Mckcenna & Hodges (1988) and Koziol Newton
(1988,1989) barometers yield values ranging from 7.58 to 9.99
Kbars at 800°C. Cordierite-bearing gneisses yield peak
pressures in the range from 5.7 to 8.15 Kbars. Geobarometric
calculations at PHD = Ptotal conditions, based on garnet-
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cordierite geobarometers of Bhattacharya & Sen (1985) and
Bhattacharya (1986) bracket equilibrium pressures within
reasonable limits (9.07 & 10.38 Kbars), thus fixing the peak
pressure approximately at 8.4 Kbars. Application of
clinopyroxene-garnet-plagioclase-quartz method of Perkins &
Newton (i981) yields a mean pressure value of 3.3 Kbars for
the calc granulite sample occurring close to the Gap proper.
Extensive application of Moecher et al (1988) geobarometer
for the present study has been limited due to the
compositional constraints introduced by extensive so I id
solution between hedenbergite and diopsidic compositions of
clinopyroxene grains.
Rim pressures corresponding to peak temperatures,
calculated for the khondalites and associated gneisses are
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