HR: 0800h
AN: V51B-0536    [Abstracts]
TI: Diagnostic Features of Mantle Plume Penetration Into the Lithosphere.
AU: * Jurine, D
EM: jurine@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, 75005 France
AU: Jaupart, C
EM: cj@ccr.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, 75005 France
AU: Brandeis, G
EM: brandeis@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, 75005 France
AB: The success or failure of the mantle plume hypothesis rests in part on its predictions for the manner of plume penetration through the lithosphere. We study how thermal plumes interact with viscous and buoyant boundary layers which serve as analogs for oceanic and continental lithospheres of various ages. Laboratory experiments and numerical simulations have been performed over a large range of values of plume buoyancy flux, lithosphere density, viscosity and thickness. Plume penetration proceeds in two distinct phases. In an initial phase, the lithosphere thins and is heated by the plume. The extent of plume penetration depends on lithosphere viscosity and plume buoyancy, and is not sensitive to plume dimensions. In a second phase, heated lithosphere becomes unstable and generates a secondary upwelling of larger dimensions than the plume. The shape and dimensions of the intrusion into the lithosphere vary significantly as a function of the control parameters. Scaling laws have been derived for the initial penetration velocity and for the critical time for lithosphere instability. Application to the Earth leads to a critical time equal to a few tens of My. The two penetration phases are associated with different styles and rates of upwelling, and hence different melting rates and magma compositions involving mixtures of asthenospheric and lithospheric melts.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 7218 Lithosphere and upper mantle
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting