gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1993.057.386.11 Mineralogy Mineral Chemistry and Reaction Textures in Metabasites from the Eastern Ghats Belt, India and Their Implications Dasgupta Somnath Sengupta Pulak Mondal A. Fukuoka M. * Department of Geological Sciences, Jadavpur University, Calcutta-700 032, India

Present address: Department of Earth and Planetary Sciences, Kyushu University Fukuoka 812, Japan.

 3 1993 57 386 113 120 2 4 1991 5 3 1992 Copyright © 1993, The Mineralogical Society 1993 Abstract

Three types of mafic granulites, namely two pyroxene-plagioclase granutlite (MG), two pyroxene-plagioclase-garnet granulite (GMG) and spinel-olivine-plagioclase-two pyroxene granulite (SMG) exposed at Sunkarimetta, Eastern Ghats belt, India. The mafic granulites exhibit a foliation concordant with that in associated granulite facies quartzofeldspathic gneisses. Textural characteristics and mineral chemical data suggest the following mineral reactions: olivine + plagioclase = spinel + orthopyroxene + clinopyroxene (SMG), orthopyroxene + plagioclase = garnet + quartz (GMG), clinopyroxene + plagioclase = garnet + quartz (GMG) and plagioclase + hemoilmenite + quartz = garnet + ilmenite + O2 (GMG). Geothermobarometry indicates maximum P-T conditions of metamorphism at c. 8.5 kbar, 950°C. The mafic granulites later suffered nearly isobaric cooling to c. 7.5 kbar, 750°C. Bulk compositional characteristics suggest that SMG is of cumulate origin. The protoliths of the mafic granulites, emplaced at c. 32 km depth, are probably responsible for thermal perturbation causing granulite facies metamorphism of the enclosing rocks.

 Keywords basite granulite texture Eastern Ghats India