NEODYMIUM ISOTOPE CONSTRAINTS ON THE TECTONIC EVOLUTION OF EAST GONDWANA

East Gondwana incorporates a collage of polymetamorphic terrains with long-lived tectonic histories from the Early Archaean to the Neoproter ozoic. The oldest cratonic areas have been identified in South India ( north of the Palghat-Cauvery shear zone) and East Antarctica (the Napi er Complex). These terrains are remnants of an East Gondwana craton th at underwent initial crustal growth during the Early Archaean and gran ulite-facies metamorphism at similar to 2.5 Ga. Both were virtually un affected by the Pan-African orogeny (1.1-0.5 Ga). In contrast, Protero zoic terrains were subject to high-grade metamorphism during the Pan-A frican event. On the basis of published Nd model ages, a direct correl ation can be made between southern Madagascar (south of the Ranotsara shear zone), southern India (the Madurai Block and Kerala Khondalite B elt) and the Highland/Southwestern Complex of Sri Lanka, which compris e a Later Archaean-Palaeoproterozoic (3.0-2.0 Ga) mobile belt that may extend eastwards into East Antarctica. The youngest period of crustal growth in East Gondwana has been recognised at 1.5-0.8 Ga from isotop ic studies of the Mozambique Belt of East Africa, the Vijayan Complex of Sri Lanka and the Yamato-Belgica Complex/Sor Rondane Mountains of E ast Antarctica. Small slivers of terrain of intermediate age (1.9-1.2 Ga) have been recognised in South India (Achankovil metasediments) and Sri Lanka (Wanni Complex) that may represent mixed-age contributions to elastic sedimentary basins. Copyright (C) 1996 Elsevier Science Ltd