Top: perspective view of a hot mantle plume interacting with a moving lithospheric plate. Bottom: Cross section of predicted melting rate of an enriched (EC) and depleted (DC) material in the plume.

Predicted map of the geochemical composition of magma that (conceptually) rises vertically out of the mantle onto the seafloor. Gray circles mark hypothetical magma capture zones of two volcanoes passing over the melting zone with the lithospheric plate

Todd Bianco (Ph.D. 2008). "Dynamics and Melting of a Heterogeneous Mantle: Importance to Geographic Variations in Hotspot Lava Composition". This study uses numerical models to study the dynamics and melting of a plume as it interacts with a moving plate. The mantle is assumed to be composed of small-scale chemical heterogeneities that begin melting at different depths owing to differences in composition. Spatial variations in melting rate (left figure, bottom) cause components to melt at different rates and thus to be expressed chemically with different strengths at the surface (right figure)

See: Bianco, T. A., G. Ito, J. van Hunen, M. D. Ballmer (2008), J. J. Mahoney, Geochemical variation at the Hawaiian hotspot caused by upper mantle dynamics and melting of a heterogeneous plume, Geochem. Geophys. Geosys,.9, Q11003, doi:10.1029/2008GC002111.PDF