Is the depleted component entrained, depleted upper mantle?
An entrained, depleted upper mantle component should be mostly present in the Kerguelen plateau lithosphere, which formed by melting of the head of the Kerguelen plume, where most of the entrained depleted mantle may have mingled with the upwelling plume (e.g. Campbell & Griffiths, 1990). Only one ODP Leg 120 site shows the important involvement of a depleted component (Site 749; Frey et al., 2002b). Alternatively, melting of plume and entrained depleted mantle may occur in ponded plume material areas, which can reach lateral extensions of thousands of kilometres (Nataf, 2000), and where mingling is more efficient. On the basis of the geochemical data we are unable to determine if the depleted component was depleted mantle entrained during plume ascent or depleted material associated with the SEIR. Is the depleted component the upwelling asthenospheric source for SEIR basalts? Rare earth element patterns of lower-crustal metagabbro xenoliths found in the alkalic dykes and flows on the
