Chemical Composition, U–Th–Pb Age, and Geodynamic Setting of Metavolcanic Filla Series (Rauer Islands, East Antarctica)

Abstract

An assemblage of mafic granulites (schists), plagiogneisses, and metasedimentary rocks, which is referred to as the Filla Series, is exposed in the Rauer Islands (opposite the eastern coast of the Prydz Bay). The chemistry and Nd isotope composition of the schists, which are interpreted as metavolcanics, are characterized; the results of U–Th–Pb dating (SHRIMP) of zircons from these rocks are presented. The data obtained indicate that the protolith of these rocks crystallized ca. 1500 Ma ago and that the rocks later underwent thermal events at ca. 1000 Ma and 545–515 Ma. The relatively high eNd(t) values, ranging from 2 to 4.5 for most samples, indicate the primitive composition of the mantle source and the limited extent of crustal contamination. The specific chemical composition of these rocks suggests that the Filla Series was formed in a convergent (back-arc(?)) setting with contributions from both plume and lithospheric sources. The apparently heterogeneous rock assemblage may be a product of tectonic interaction between the active continental margin and oceanic plateau. The obtained Early Mesoproterozoic age of the mafic rocks of the Filla Series argues for correlation of the Rauer Islands area with the long-lived Musgrave–Albany–Fraser–Wilkes Proterozoic (super) province in Australia and Antarctica, on the one hand, and the Eastern Ghats Province in India, on the other. The formation of the Early Mesoproterozoic Filla Series suggests that the development of the hypothetical paleocean (its convergent margins) did not terminate during the Paleoproterozoic but continued into the Mesoproterozoic. Correlation with the Musgrave–Albany–Fraser–Wilkes (super) province suggests a shared geological evolution of large crustal blocks, represented by the Prydz Bay coast and the Australian–Antarctic block starting from the Early Mesoproterozoic.