Graduate School of Science and Technology, Niigata University
Abstract
The ultrahigh-temperature (UHT)granulite from the central Highland Complex,Sri Lanka preserves histories of several metamorphic events.The application of geothermobarometries on sapphirine-garnet-orthopyroxene-sillimanite-quartz bearing granulites confirms that metamorphism occurred under the UHT condition. We report a middle Proterozoic age of 1478+-58 Ma from the internal isochron using a garnet core,whole rock and felsic fraction (quartz in the Sm-Nd system from the same rock samples.As this granulite preserves several stages of orthopyroxene formation,the measured isotope composition of orthopyroxene give mixed values.The reference isochron plotted with orthopyroxene and whole rock give an age of 550 Ma.The present results can be interpreted to mean that the middle Proterozoic metamorphic event could have been the thermal peak.During the uplift stage,this granulite might have remetamorphosed at younger stages along with the adjacent rocks