Thermo-mechanical models of lithosphere and asthenosphere: can a change in plate velocity induce magmatic activity?

Abstract

The thermal and mechanical structure of the upper mantle is investigated on the basis of the law of deformation of olivine combined with appropriate equations of motion and of heat balance. The effect of changes in plate velocities is shown to generate temperature anomalies underneath the lithospheric plate. The time delay is not the usual thermal time constant but represents the time necessary to generate enough heat to approach a new steady state situation. It depends strongly upon the magnitude of the velocity jump and upon the amount of radiogenic heat sources present in the mantle. The correlations described by Briden & Gass ( Nature , Lond . (1974) 248, 650) for Africa between polar wander and magmatism can in principle be explained by our models.