HR: 0800h
AN: T21C-0511    [Abstracts]
TI: Generation and Stability of Hotspots and Plumes in a Spherical Mantle Convection Model Incorporating Tectonic Plate Motions
AU: * Quere, S
EM: squere@sca.uqam.ca
AF: GEOTOP, Universite du Quebec A Montreal, Montreal, Qc H3C 3P8 Canada
AU: Forte, A M
EM: forte.alessandro@uqam.ca
AF: GEOTOP, Universite du Quebec A Montreal, Montreal, Qc H3C 3P8 Canada
AB: We investigate the influence of tectonic plate motions on plume generation in a 3-D spherical mantle convection model in which surface tectonic plates are dynamically coupled to the underlying convective flow. We first derived a simple reference convection model, based on a two-layer viscosity profile, in which we incorporate only the geometry of the tectonic plates in the No-Net-Rotation (NNR) NUVEL-1 model. This model readily yields the principal features of plate tectonics (i.e. linear subduction zones, divergent mid-ocean rises) as well as four focussed upwelling mantle plumes. In the first, time-dependent simulation, which was initiated with the mean geotherm extracted from the reference model, we imposed the present-day (NUVEL-1) plate velocities and observed the generation of six focussed upwellings whose location and number is very similar to the primary terrestrial hotspots (e.g. Hawaii, Iceland and Réunion) which have been recently identified (Courtillot et al, 2003). To determine the robustness of these results we carried out a second time-dependent convection simulation incorporating the past 120 Ma history of tectonic plate evolution (Lithgow-Bertelloni & Richards, 1998). We found shifting `hotlines' at the CMB, but the locations of the overlying hotspot plumes remained relatively stable. The geometry of the hotlines in both sets of time-dependent convection experiments are very similar to each other, showing that the present-day (NUVEL-1) plate motions are sufficient for modelling realistic terrestrial hotspot generation. In a third set of simulations, in which the tectonic plate motions are not imposed but rather predicted on the basis of the underlying convective stresses, we found that the locations of the subduction zones changed rapidly but the locations of the hotspot plumes were quite stable overall.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8125 Evolution of the Earth (0325)
DE: 8157 Plate motions: past (3040)
DE: 8158 Plate motions: present and recent (3040)
SC: Tectonophysics [T]
MN: Fall Meeting 2005