HR: 0800h
AN: S11B-0551    [Abstracts]
TI: A depleted and destabilized continental lithosphere near the Rio Grande Rift
AU: * Song, T A
EM: asong@ciw.edu
AF: Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, Washington, DC 20015, United States
AU: Helmberger, D V
EM: helm@gps.caltech.edu
AF: Seismological Laboratory, Division of Geological and Planetary Science, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, United States
AB: Seismic waveform diffraction patterns reveal a 120 km thick slab-like anomaly with about 4% increases in both compressional and shear wave speed, extending down to nearly 600 km between the Rio Grande Rift and the western Great Plains in the southwestern United States. Monte Carlo simulations suggest that the most probable interpretation is a temperature anomaly of about -400 K with additions of olivine (11%), orthopyroxene (12%) and losses of clinopyroxene (-14%), garnet (-9%) relative to the adjoining mantle asthenosphere beneath the Rio Grande Rift. This sesimic anomaly, probably continental lithosphere, is cold and is as depleted as the Archean continental lithosphere. It was likely formed in the Proterozoic age but destabilized during the Cenozoic rifting of the Rio Grande Rift
DE: 7203 Body waves
DE: 7218 Lithosphere (1236)
DE: 8103 Continental cratons
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
SC: Seismology [S]
MN: 2007 Fall Meeting