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

Abstract 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 °C at 7.5–8 kbar, followed by decompression to 3.5–5 kbar and cooling to 450–480 oC, 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 °C. The U–Pb age data from zircons (∼1 to ∼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.