Oxygen isotope values in granulite facies rocks from the Eastern Ghats Granulite Belt, India

Oxygen isotope values in metapelites including garnet-sillimanite gneisses (khondalites), quartzo-feldspathic gneisses (leptynites), cordierite-sapphi rine gneisses and the associated marbles, calc-silicates, quartzites, basic granulites and charnockites from the Eastern Ghats Granulite Belt are pres ented and their significance discussed. Metapelites show a wide variation i n delta(18)O values (4.50 to 13.90 parts per thousand) that is controlled l argely by the mineralogy of the rocks. Coarse grained porphyritic charnocki tes have higher delta(18)O values (8.60-11.20 parts per thousand) than that of medium grained ones (5.90-6.60 parts per thousand). Basic granulites ha ve the minimum delta(18)O values (similar to 5.0 parts per thousand). Oxyge n isotope values of different rock units in the granulite belt are constrai ned mostly by the composition of the source rocks of the sediments and of t he protoliths in the case of charnockites. Post-depositional metamorphic an d metasomatic fluids had little contribution to the delta(18)O variations i n these rocks.