HR: 12:05h
AN: T42A-08    [Abstracts]
TI: Lithospheric thickness and heat flux beneath cratons
AU: * Shapiro, N M
EM: nshapiro@ciei.colorado.edu
AF: Center for Imaging the Earth's Interior, University of Colorado at Boulder Campus Box 390, Boulder, CO 80303-0390 United States
AU: Mareschal, J
EM: mareschal.jean-claude@uqam.ca
AF: GEOTOP-UQAM-McGill, UQAM. P.O. Box 8888, Montreal, QC H3C 3P8 Canada
AU: Ritzwoller, M H
EM: ritzwoll@ciei.colorado.edu
AF: Center for Imaging the Earth's Interior, University of Colorado at Boulder Campus Box 390, Boulder, CO 80303-0390 United States
AU: Jaupart, C
EM: jaupart@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, CO 75252 France
AB: We apply a physically constrained Monte Carlo inversion of surface wave data to study lithospheric structure beneath cratons in Canada, Siberia, and Australia. We, first, invert available surface heat-flow measurements to estimate crustal geotherms and to bound the temperatures in the uppermost mantle. These bounds are then applied as a constraint on the seismic surface wave inversion. We reformulate the inversion by replacing the seismic parameterization with physical parameters that describe the thermal state and evolution of the upper mantle. These parameters include the temperature in the uppermost mantle directly beneath Moho, the mantle temperature gradient (or mantle heat flux), and the potential temperature of the sublithospheric convecting mantle. We also apply a priori constraints based on the condition that melting temperatures were not reached in the crust in Proterozoic times as well as other theoretical considerations. The combination of seismic and thermal data is based on the interconversion between temperature and seismic velocity. The inversion is formulated as a Monte-Carlo sampling of model space that results in an ensemble of models that fit the data, which provides estimates of uncertainties in the model parameters. Results are presented as the distribution of mantle heat flux and lithospheric thickness. Although variations in these parameters are not well correlated with surface tectonic history within cratons, they are anticorrelated with each other. This is consistent with the hypothesis that the old cratonic lithosphere and the underlying astenosphere are in thermal equilibrium and the heat flux through the deep lithosphere is governed by small-scale sublithospheric convection.
DE: 8180 Tomography
DE: 7255 Surface waves and free oscillations
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8130 Heat generation and transport
DE: 7218 Lithosphere and upper mantle
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting