Isotope evidence of a mantle convection boundary at the Australian-Antarctic Discordance

Abstract

Basalts from the Southeast Indian Ridge south of Australia form two geographically and isotopically distinct groups that show affinities with either Indian Ocean or Pacific/Atlantic Ocean isotope compositions. The data raise the possibility that there is a sharp boundary between the Indian and Pacific Ocean isotope provinces. The isotope boundary occurs over less than 200km within the Australian–Antarctic Discordance, a technically complex region believed to overlie a zone of downwelling mantle flow.