Characterization of partial melting events in garnet-cordierite gneiss from the Kerala Khondalite Belt,India

Phase equilibria modelling coupled with U-Pb zircon and monazite ages of garnet-cordierite gneiss from Vallikodu Kottayam in the Kerala Khondalite Belt,southern India are presented here.The results suggest that the area attained peak P-T conditions of～900℃at 7.5-8 kbar,followed by decompression to 3.5-5 kbar and cooling to450-480℃,preserving signatures of the partial melting event in the field of high to ultra-high temperature metamorphism.Melt reintegration models suggest that up to 35% granitic melt could have been produced during metamorphism at～950℃.The U-Pb age data from zircons(～1.0-～0.7 Ga) and chemical ages from monazites(～540 Ma and～941 Ma) reflect a complex tectonometamorphic evolution of the terrain.The～941 Ma age reported from these monazites indicate a Tonian ultra-high temperature event,linked to juvenile magmatism/deformation episodes reported from the Southern Granulite Terrane and associated fragments in Rodinia,which were subsequently overprinted by the Cambrian(～540 Ma) tectonothermal episode.