Tasman Sea evolution and hotspot trails

Thermal upwellings 80-100Ma ago initiated Tasman spreading. With an adjoining event 65Ma ago, this left a legacy of basaltic ‘hotspot’ activity, still current 55Ma after spreading ceased. Tasman triple points are proposed as hotspots, with some still active in West Antarctica. The Gippsland hotspot forms a Tasman-Balleny Islands reference seamount trail. Spacing of southern Tasman sites (South Tasman Rise, East Tasman Rise, Gippsland hotspots) coincides with present West Antarctic volcanism (Mt. Erebus, Mt. Melbourne, Balleny Islands). Northern Tasman triple points formed matching basaltic trails through eastern Australia (Barrington, Ipswich and Bundaberg trails), which include some felsic features (alkaline lavas, zircons, sapphires). Later 65-55Ma Coral Sea-Louisiade-Cato spreading, linked into Tasman spreading, introduced further hotspot sites. Using the Tasman reference trail, these intersect age progressive Tasmantid seamount and east Australian volcano chains. Still later 35-28Ma spreading links into the Lord Howe trail. Antarctic hotspot volcanoes and older east Australian lineages show low 87 Sr/ 86 Sr and radiogenic Nd and Pb, with some HIMU source mixing. The later hotspots show higher 87 Sr/ 86 Sr and Enriched Mantle (EM1) mixing. A reconstructed Tasman hotline and Coral Sea starting plume links evolution of Tasman floor to a 4000 km long hybrid hotspot system.