Mesoproterozoic Reworking of Palaeoproterozoic Ultrahigh-temperature Granulites in the Central Indian Tectonic Zone and its Implications

In the southern periphery of the Sausar Mobile Belt (SMB), the southern component of the Central Indian Tectonic Zone (CITZ), a suite of felsic and aluminous granulites, intruded by gabbro, noritic gabbro, norite and orthopyroxenite, records the polymetamorphic evolution of the CITZ. Using sequences of prograde, peak and retrograde reaction textures, mineral chemistry, geothermobarometric results and petrogenetic grid considerations from the felsic and the aluminous granulites and applying metamorphosed mafic dyke markers and geochronological constraints, two temporally unrelated granulite-facies tectonothermal events of Pre-Grenvillian age have been established. The first event caused ultrahigh-temperature (UHT) metamorphism (M1) (T 950C) at relat-ively deeper crustal levels (P 9 kbar) and a subsequent post-peak near-isobaric cooling P–T history (M2). M1 caused pervasive biotite-dehydration melting, producing garnet–orthopyroxene an