Geochronologic and isotopic constraints on granulite formation in the Kodaikanal area, southern India

Abstract

The Kodaikanal hill ranges constitute a major granulite massif. Metasediments quartzo-feldspathic charnockites, mafic granulites and anorthosites form the major lithologies. Single zircon evaporation ages indicate 2.1 Ga for the initial crust formation. Sm-Nd garnet - whole rock isochron ages suggest 553 ± 15 Ma for near peak metamorphism followed by isothermal uplift upto 459 ± 19 Ma. Reactivation of Palghat-Cauvery shear zone followed by lithospheric extension and breakdown of Gondwana continent probably occurred at 350 ± 16 Ma. Whole rock Nd and Sr isotope data suggest that the magmatic protoliths of charnockites were generated by reworking of ancient crustal source with significant juvenile input. -from Authors