Continent-Ocean Chemical Heterogeneity in the Mantle Based on Seismic Tomography
Alessandro M. Forte 1,
Adam M. Dziewonski 2, and
Richard J. O'Connell 2
1 Département de Sismologie, Institut de Physique du Globe de Paris, 4 place Jussieu, 75252 Paris Cedex 05, France
2 Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA.
Seismic models of global-scale lateral heterogeneity in the mantle show systematic differences below continents and oceans that are too large to be purely thermal in origin. An inversion of the geoid, based on a seismic model that includes viscous flow in the mantle, indicates that the differences beneath continents and oceans can be accounted for by differences in composition in the upper mantle superposed on mantle-wide thermal heterogeneities. The net continent-ocean density differences, integrated over depth, are small and cause only a low flux of mass and heat across the asthenosphere and mantle transition zone.
Submitted on August 29, 1994
Accepted on January 26, 1995
