Ca. 750–1100 Ma magmatic events and Grenville-age deformation in Sri Lanka: relevance for Rodinia supercontinent formation and dispersal, and Gondwana amalgamation

Abstract

Large volumes of ∼880–1100 Ma calc-alkaline granitoid rocks in the Wanni and Vijayan crustal provinces of Sri Lanka make it likely that these domains were produced in active margin settings, probably Grenville-age magmatic arcs. We report new single zircon evaporation ages and Nd isotopic systematics for dioritic to granodioritic gneisses of the Kadugannawa Complex of central Sri Lanka which record a period of magmatic arc activity between 1006 and 881 Ma and show this complex to be part of the Wanni domain. Both provinces were probably generated in arc-related settings at the outer margin of Rodinia, but this cannot be ultimately proven on the basis of the currently available data. In spite of a strong Pan-African tectono-thermal overprint at ∼600–550 Ma that we relate to involvement of Sri Lanka in the amalgamation of the Gondwana Supercontinent, rare ∼1000–900 Ma structures are preserved in the gneisses of the Kadugannawa Complex that may constitute remnants of the accretion history of Rodinia. We further suggest that the basement rocks of Sri Lanka do not correlate with crustal domains in southern India or in East Africa, since these were not part of Rodinia.