GEOCHEMISTRY OF THE 755 MA MUNDINE WELL DYKE SWARM, NORTHWESTERN AUSTRALIA: PART OF A NEOPROTEROZOIC MANTLE SUPERPLUME BENEATH RODINIA?

Abstract

Geochemical and Nd-Hf isotopic data are reported for dolerite samples from the Neoproterozoic (755 Ma) Mundine Well dyke swarm in northwestern Australia. These dolerites are tholeiitic in composition, crystallised from a common parental magma. Although the dolerite magma underwent varying degrees of crustal contamination during ascent and emplacement, the uncontaminated parental melt possessed geochemical and Nd isotopic characteristics, such as Nb/La ≈ 1.5, Nb/Th ≈ 15, Nb/U ≈ 50, εNd(T) ≈ 5, and εHf(T) ≈ 9 (estimated by extrapolation from geochemical correlations), that closely resemble plume-derived ocean island basalts. These features are also similar to those of dolerite dykes of similar age from Seychelles and South China. We propose that these late Neoproterozoic mafic suites may have been generated by melting of a vast asthenospheric mantle superplume that developed beneath, and led to breakup of, the Rodinia supercontinent. © 2005 Elsevier B.V. All rights reserved.