抄録
High-pressure experiments suggest the possibility that liquid iron from the core may infiltrate the lower mantle oxides at grain boundaries thus creating heterogeneity at the grain scale. Lateral heterogeneity in seismic velocities, in the D" layer at the base of the mantle, exists at the scale of hundred kilometers. Various scenarios purporting to account for the seismic heterogeneities by infiltration are examined and found wanting. However, if it is assumed that convection can spread infiltrated material throughout the D" layer, it is possible to account for the observed decrease or increase in seismic velocities by about 1 vol% iron alloy at grain boundaries in the liquid or solid state respectively, depending on the depth of the isotherm corresponding to the melting point of the alloy.
