Sillimanite aggregates in high-pressure and ultrahigh-temperature granulites from the Gondwana suture zone in southern India: implications for P-T path

Abstract

The southern Indian granulite terrane is composed of several blocks and shear zones that underwent Cambrian HP (high-P) and UHT (ultrahigh-T) metamorphism. Kyanite inclusions occur in garnet as a key mineral of HP metamorphism. In contrast, three types of sillimanite occur in the matrix; radial, columnar, and fine-grained types. One sample contains fine-grained sillimanite mantled by columnar type. Laser Raman spectroscopic studies of the fine-grained sillimanite identified small peaks of kyanite in the dominant sillimanite peaks. This could suggest a reaction: Ky → Sil, which is concordant with the HP and UHT evolution model of the study area.