Detection of upper mantle flow associated with the African Superplume

• Published in: Earth and planetary science letters 2004-08, Vol.224 (3), p.259-274
• Main Authors: Behn, Mark D., Conrad, Clinton P., Silver, Paul G.
• Format: Article
• Language: English
• Subjects: African Superplume; mantle convection; seismic anisotropy
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2004.05.026

A continental-scale, low seismic velocity anomaly in the mid to lower mantle beneath Africa is a robust feature of global tomographic models. Assuming the low velocities are associated with warm, less dense material, the African seismic anomaly has been ascribed to a long-lived thermal upwelling from the lower mantle. Such a large-scale upwelling should also affect the regional horizontal flow field in the upper mantle. To test this model, we compare seismic anisotropy inferred from shear-wave splitting measurements with instantaneous flow calculations that incorporate mantle density structure inferred from seismic tomography. We calculate splitting parameters at 13 ocean island stations surrounding Africa. Splitting measurements from island stations are ideal for interpreting anisotropy induced by asthenospheric flow because they lack a thick overlying lithosphere that may also contribute to the observed anisotropy. We tested for a possible lithospheric contribution by comparing the splitting measurements with the fossil spreading directions. We find that although the fossil lithospheric fabric closely matches the observed fast polarization directions at stations