HR: 09:45h
AN: T21C-08 INVITED    [Abstracts]
TI: High Resolution Modelling of Convective Flow in the Sublithospheric Mantle Below the African Plate
AU: Forte, A M
EM: forte.alessandro@uqam.ca
AF: GEOTOP, Université du Québec à Montréal, CP 8888, Montréal, QC H3C 3P8, Canada
AU: * Moucha, R
EM: moucha@sca.uqam.ca
AF: GEOTOP, Université du Québec à Montréal, CP 8888, Montréal, QC H3C 3P8, Canada
AU: Simmons, N A
EM: simmons27@llnl.gov
AF: Lawrence Livermore National Laboratory, Seismology Group, 7000 East Avenue, Livermore, CA 94550, United States
AU: Grand, S P
EM: steveg@maestro.geo.utexas.edu
AF: Jackson School of Geosciences, University of Texas at Austin, 1 University Station, Austin, TX 78712, United States
AU: Quéré, S
EM: quere.sandrine@uqam.ca
AF: GEOTOP, Université du Québec à Montréal, CP 8888, Montréal, QC H3C 3P8, Canada
AU: Rowley, D B
AF: The Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637, United States
AB: The African continent is unique, both in terms of its surface topography and in terms of the high-temperature, plume-like structures in the subcontinental mantle which have been inferred by seismic tomographic imaging. No other continent on Earth displays the pervasive influence of very large scale tensional stresses and widely distributed topographic domes and late-Cenozoic volcanic eruptions which have impacted the surface geology of Africa. Advances in high resolution seismic tomographic imaging of global Earth structure have revealed that the African continent is sitting atop an immense thermochemical plume which stretches upward from the core- mantle boundary under southern African and extends into the upper mantle (Simmons et al. 2007). The most recent high-resolution tomography model is derived from a joint inversion of both global seismic and surface geodynamic data sets and it incorporates mineral physical constraints on the thermal properties of the mantle. This tomographic inversion yields a 3-D distribution of mantle density anomalies that includes both thermal and compositional heterogeneity and it therefore enables us to incorporate the stabilising effect of compositional buoyancy in the continental tectosphere and in the deep lower mantle. This new inference of the 3-D structure below the African plate are used in a new series of numerical simulations of the present day mantle convective flow below the continent. We obtain a remarkably detailed pattern of shallow, sublithospheric flow below Africa and we trace its dynamical relationship to the deep-mantle flow driven by the African superplume. The asthenospheric flow patterns show clearly focussed upwellings below all the major late-Cenozoic volcanic domes on the African plate. We employ these predictions of shallow mantle flow to explore the implications for present-day dynamic topography and stress on the African plate.
DE: 7218 Lithosphere (1236)
DE: 8031 Rheology: crust and lithosphere (8159)
DE: 8138 Lithospheric flexure
DE: 8159 Rheology: crust and lithosphere (8031)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting