Hith-temperature dehydration melting and decompressive textures in Mg-Al granulites from the Palni hills, South India

摘要

The Palni hills form part of the granulite facies terrain of the south Indian shield which contains a variety of rock types.The Mg-Al granulites of the Palni hill display evidence of metamorphic reactions involved in the formation of diverse mineral assemblages documented in different types of reaction textures,coronas and symplectites.Petrographic studies show evidence for melting and decompression reactions that are preserved in individual samples.The UHT assemblage includes some of Opx,Crd,Sil,Grt,Kfs,Qtz,Spr and Bt which coexisted with melt in equilibrium at the thermal peak.In a later stage,the majority of the reactions involve cordierite formation at the expense of partial or complete breakdown of garnet.A possible correlation of similar post-peak decompression textures in the high-grade granulites in the continental fragments of southern India,Sri Lanka,Madagascar and East Antarctica support the probability that they share similar lithologies and thus form an integral part of a megacontinent.