CHARACTERIZATION OF A PLUME-RELATED SIMILAR-TO-800 MA MAGMATIC EVENT AND ITS IMPLICATIONS FOR BASIN FORMATION IN CENTRAL-SOUTHERN AUSTRALIA

Geochemical and Nd isotopic studies are reported for widespread Late P roterozoic (approximately 800 Ma) mafic dyke swarms and volcanics in c entral-southern Australia. These mafic suites, although occurring over a large area of > 1000 km, show remarkably uniform geochemical and is otopic features characterised by similar trace element distribution pa tterns, smooth LREE-enriched patterns, and a limited range Of epsilon( Nd)(800 Ma) values (+2.4 to +4.2), closely resembling the Hawaiian bas alts 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, aulacog en-type rifting and onset of flood basalt volcanism. Large-scale crust al extension and thinning followed by thermal subsidence as a result o f the plume activity may have been responsible for the formation of th e large sedimentary basins in central-southern Australia.