Plume fluxes from seismic tomography

We use mantle plume images from finite frequency tomography and the Stokes equation to obtain a quantitative estimate of the heat and volume flux across several well resolved plume sections in mid-mantle. Although not a perfect barrier, widening of plumes just below 670 km depth indicates that the phase transition from ringwoodite to perovskite plus magnesowustite and possibly iron enrichment of the lower mantle resists plume passage into the upper mantle. Estimated heat- and volume flux for individual plumes at mid-mantle depths is greater than predicted by surface observations of buoyancy flux, even for very high viscosity. Although uncertainties are large, the high flux observed in plumes at mid-mantle depth is compatible with the view that plumes are responsible for all upward advective heat transport in the lower mantle that eventually breaks through into the upper mantle. (c) 2006 Elsevier B.V. All rights reserved.