HR: 0800h
AN: T11C-0728    [Abstracts]
TI: Mantle Evolution Beneath Supercontinents Since the Archean
AU: * Phillips, B R
EM: benp@lanl.gov
AF: Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545, United States
AU: Coltice, N
EM: coltice@univ-lyon1.fr
AF: Laboratoire de Sciences de la Terre, Université Lyon 1, ENS Lyon, Bat Géode, 2 rue Raphael Dubois, Villeurbanne Cedex, 69622, France
AU: Bertrand, H
EM: herve.bertrand@ens-lyon.fr
AF: Laboratoire de Sciences de la Terre, Université Lyon 1, ENS Lyon, Bat Géode, 2 rue Raphael Dubois, Villeurbanne Cedex, 69622, France
AU: Ricard, Y
EM: ricard@ens-lyon.fr
AF: Laboratoire de Sciences de la Terre, Université Lyon 1, ENS Lyon, Bat Géode, 2 rue Raphael Dubois, Villeurbanne Cedex, 69622, France
AU: Rey, P
EM: prey@geosci.usyd.edu.au
AF: School of Geosciences, University of Sydney, Edgeworth Building, Sydney, NSW 2006, Australia
AB: Supercontinents promote mantle warming and associated large-scale magmatism. Mechanisms for this feedback include the clustering of mantle plumes and lithospheric forcing of convective length scales. Modeling studies show that long-wavelength convection inherent to an internally heated mantle with no active plumes and a supercontinent produces mantle temperature anomalies of +100 °C. Such global mantle warming could have sourced the Central Atlantic Magmatic Province during the breakup of Pangea. However, the sensitivity of the mantle to smaller supercontinents that might have existed during the Archean when total continental area amounted to only 10--20% of the Earth's surface is unknown. Here we use 3D spherical mantle convection models with continents to show that convective length scales, and hence subcontinental temperatures, increase concurrently with continental area. Plumes magnify warming, leading to a temperature excess of ~200 °C. We also find that significant broadly distributed heating occurs beneath diminutive supercontinents appropriate to the Archean, even in purely internally heated models. This result could help to explain the pulse in continental growth at 2.7 Ga.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
DE: 8178 Tectonics and magmatism
SC: Tectonophysics [T]
MN: 2007 Fall Meeting