HR: 1330h
AN: V12B-0587    [PDF]
TI: Penetration of mantle plumes through the lithosphere.
AU: * Jurine, D
EM: jurine@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place jussieu, Boite 89, Paris cedex 05, 75252 France
AU: Jaupart, C
EM: cj@ccr.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place jussieu, Boite 89, Paris cedex 05, 75252 France
AU: Brandeis, G
EM: brandeis@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place jussieu, Boite 89, Paris cedex 05, 75252 France
AB: Many theories have emerged these last years in order to explain the many forms of melt anomalies. The traditional plume theory has to deal with the interaction of a thermally driven plume with the lithosphere which is still poorly known. Oceanic and continental lithospheres differ by their composition and thickness, implying differences of rheology and density. Continental lithosphere is thicker, chemically distinct from the underlying mantle and probably more viscous and less dense. In order to quantify the effect of these differences, we have used both laboratory experiments and numerical calculation. A thermal plume is generated by a point source of heat at the base of a layer and rises towards an upper layer which is buoyant and more viscous. We study the effects of the energy flux, the density difference, the viscosity ratio, and the thickness of the upper layer. Numerical simulations are made with the STAG3D program developed by Paul Tackley. We solve the equations governing the convective motion in a non-compressible viscous fluid and use active tracers to model the upper layer. Simulations allow to vary all the parameters in a wide range and show good agreement with the experiments. Both experiments and numerical simulations show a wide range of behaviors: the mantle plume can spread laterally at the interface or penetrate through the lithosphere. Moreover, the lithosphere is heated from below by the plume and can become convectively unstable. The thickness and viscosity of the lithosphere are key parameters. The difference of thickness and composition between continental and oceanic lithosphere can lead to very different end-results at the surface.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 8125 Evolution of the Earth
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting