Magma Genesis and Mantle Sources in the Easter Hotspot-Easter Microplate System

Large scale flow of material between upwelling mantle plumes and mid-ocean ridge spreading axes has been shown to occur throughout the ocean basins (Schilling, 1985). The volcanism associa ted with the Easter H o t s p o t E a s t e r Microplate spreading axes allows us to study the geochemical variation due to partial melting and source composition over a wide area. West of Easter Island young submarine volcanic fields and seamounts with ages of < 0.5 Ma occur in a 200 km wide region which marks the present-day position of the Easter Hotspot. The volcanic fields Ahu, Umu and Tupa lie closest to the spreading axis on about 2 Ma old crust while the two seamounts Moai and Pukao and Easter Island are located on about 3 Ma old crust (Naar and Hey, 1991).