The Louisiade Plateau: Is this 100,000 km2 Feature a Large Igneous Province in the Coral Sea, northeast of Australia

One of the fundamental predictions of mantle plume theory is that the start of the plume should cause a massive outpouring of magma, forming a Large Igneous Province (LIP). Nevertheless, comparatively few plume-derived hotspot chains have been conclusively linked with a corresponding LIP. One of the world's most spatially extensive intraplate volcanic regions is located around eastern Australia, including the world's longest continental hotspot trail and two parallel trails offshore, the Tasmantid and Lord Howe Seamount chains. No LIP has yet been linked to this hotspot volcanism, but at the northern (older) end of this region lies the submerged Louisiade Plateau, located in the northern Coral Sea, northeast of Australia. At 100,000 km2, this feature is comparable in aerial extent to the Columbia River LIP. In 2019, the rocks of the Louisiade Plateau were sampled for the first time by the Australian research vessel Investigator, yielding a variety of mafic and felsic igneous rocks. In this study, we combine bathymetry, 40Ar/39Ar and U-Pb geochronology, trace element and isotopic geochemistry, and geophysics to investigate if the Louisiade Plateau could be a LIP linked to the widespread age-progressive volcanism of eastern Australia. Preliminary results indicate most of the samples are basalts formed via high degrees of mantle melting, consistent with origin as a LIP. However, at one location, rhyolites are also present, with geochemical signatures characteristic of a substantial input of continental material (e.g., high Pb/Nd and Th/Nb), indicating that at least part of the plateau is underlain by rifted and submerged continental crust, potentially in a similar manner to the Kerguelen LIP.