Among many mantle plumes, the Kerguelen plume stands out as a large, long-lived plume manifesting itself as the Kerguelen Plateau, one of the two giant oceanic plateaus of the world. The P.I.s propose to investigate geochemical aspects of the evolutionary history of the plume. Our effort will be focused into two separate projects: (1) Basalt project (Frey) will focus on the old plateau basalt lavas in the northwestern province. Geochemical characterization of these oldest basalts will present clear understanding of secular isotopic variations observed on younger eruptives. Comparative studies between the Kerguelen and Hawaiian plumes will provide important information on how different parts of mantle plumes are tapped and on how mantle plumes evolve geochemically. (2) Xenolith project (Shimizu) will focus on detailed petrography, mineral chemistry (major and trace elements) and isotopic compositions of lower crustal and mantle xenoliths. The P.I.s intend to obtain definitive answers on whether granulites are pieces of ancient continental crust or young basaltic crust recrystallized in the granulite facies conditions. Upper mantle xenoliths will also be used to investigate the plate setting, a possible involvement of ancient continental lithosphere, and interaction between plume-derived melts and lithosphere/asthenosphere.
