Constraints on the timing of Pan-African granulite-facies metamorphism in the Kerala Khondalite Belt of southern India: SHRIMP mineral ages and Nd isotopic systematics

The supracrustal Kerala Khondalite Belt (KKB; southern India) constitutes an important but little understood terrain in the evolution of East Gondwana. Here we report SHRIMP U-Pb zircon and titanite ages for a suite of metasedimentary rocks from the KKB. Metamorphic ages at 530.2 ± 4.4 and 525 ± 4.5 Ma were obtained from metapelitic and metapsammitic migmatites, respectively. These ages are interpreted to date peak metamorphism because both rock types have extensively melted under granulite-facies conditions. A similar age (520 ± 4.7 Ma) was obtained from titanite from a granulite-facies calc-silicate rock. These ages are within error of SHRIMP ages for granulite-facies assemblages in Lützow-Holm Bay, East Antarctica, the Highland and Wanni Complexes of Sri Lanka, and Southern Madagascar. We propose that this timing reflects a short span (∼10 m.yr.) of high-temperature granulite-facies metamorphism and concomitant widespread migmatization that marks the final stage of collision between East and West Gondwana.