Abstract Geochemical and Nd isotopic studies are reported for widespread Late Proterozoic (∼ 800 Ma) mafic dyke swarms and volcanics in central-southern Australia. These mafic suites, although occurring over a large area of > 1000 km, show remarkably uniform geochemical and isotopic features characterised by similar trace element distribution patterns, smooth LREE-enriched patterns, and a limited range of ε Nd(800 Ma) values (+2.4 to +4.2), closely resembling the Hawaiian basalts and the high-Ti Karoo flood basalts. These features suggest that this mafic province was probably derived by decompressional melting of a large-scale, uniform asthenospheric mantle plume. Upwelling of the plume resulted in domal uplift of the continental lithosphere, aulacogen-type rifting and onset of flood basalt volcanism. Large-scale crustal extension and thinning followed by thermal subsidence as a result of the plume activity may have been responsible for the formation of the large sedimentary basins in central-southern Australia.