HR: 09:30h
AN: T21D-07    [Abstracts]
TI: Upper Mantle Velocity, Temperature, and Composition in the Southern Superior Province, Canada
AU: * Perry, C
EM: perry@ipgp.jussieu.fr
AF: Institut de Physiqque du Globe, 4 Pl Jussieu, Paris, 75252 France
AU: * Perry, C
EM: perry@ipgp.jussieu.fr
AF: GEOTOP-UQAM-McGill, P.O.B. 8888, sta. "downtown", Montreal, QC H2V3B5 Canada
AU: Jaupart, C
EM: cj@ccr.jussieu.fr
AF: Institut de Physiqque du Globe, 4 Pl Jussieu, Paris, 75252 France
AU: Mareschal, J
EM: mareschal.jean-claude@uqam.ca
AF: GEOTOP-UQAM-McGill, P.O.B. 8888, sta. "downtown", Montreal, QC H2V3B5 Canada
AU: Shapiro, N
EM: nshapiro@fignon.colorado.edu
AF: Institut de Physiqque du Globe, 4 Pl Jussieu, Paris, 75252 France
AB: We compile upper mantle P_n velocities from seismic refraction/wide-angle reflection surveys in the southern Superior Province of the Canadian Shield and compare them with temperatures at the Moho deduced from heat flow data. Calculated Moho temperatures and P_n velocities correlate well, showing that, in this area, P_n depends primarily on temperature. The values of ∂ V(P_n)/∂ T obtained depend weakly on the assumed value of Moho heat flow and take a value of -0.60×10^-3 ± 10% km s^-1~K^-1, within the range of temperature derivatives obtained in laboratory studies of ultramafic rocks. Comparison between observed P_n velocities and predicted values for several mineralogical models at Moho temperatures provides constraints on both the Moho heat flow and the shallow mantle composition. For all Moho heat flows, undepleted (cpx rich) mantle compositions do not yield a good fit to the data. For depleted mantle compositions, temperatures consistent with the observed P_n velocities correspond to values of the Moho heat flow larger than 12 mW m^-2. For our preferred value of 15 mW m^-2 for the Moho heat flow, the best-fit mantle composition is slightly more depleted than the on-craton model of McDonough and Rudnick [1998], with a slightly lower olivine content. The similarity in P_n-T conversion factors estimated from this empirical large-scale geophysical study and from laboratory data further supports absolute temperature values deduced from heat flow measurements and seismic studies.
DE: 7218 Lithosphere (1236)
DE: 8103 Continental cratons
DE: 8130 Heat generation and transport
SC: Tectonophysics [T]
MN: Fall Meeting 2005