HR: 14:55h
AN: V43G-05    [Abstracts]
TI: Plumes or Not? Yes, and Plenty!
AU: * Montelli, R
EM: montelli@princeton.edu
AF: Dept of Geosciences, Princeton University, Guyot Hall, Princeton, NJ 08544 United States
AU: Nolet, G
EM: nolet@princeton.edu
AF: Dept of Geosciences, Princeton University, Guyot Hall, Princeton, NJ 08544 United States
AU: Dahlen, F
EM: fad@princeton.edu
AF: Dept of Geosciences, Princeton University, Guyot Hall, Princeton, NJ 08544 United States
AU: Masters, G
EM: guy@igpp.ucsd.edu
AF: Institute of Geophysics and Planetary Physics, U.C. San Diego, La Jolla, CA 92093 United States
AB: We present confirmation of the detection of deep mantle plumes, earlier imaged using P waves (Montelli et al., Science 2004) using a finite-frequency inversion of long period S waves. Our data set comprises 69079 S traveltimes, 26337 SS-S and 13856 ScS-S differential traveltimes. We invert for both velocity anomalies, origin times, and the relocation of the 6834 hypocenters, using the banana-doughnut kernels derived by Dahlen et al. (GJI, 2000). The S-wave images confirm the presence of well resolved deep mantle plume beneath Ascension, Azores, Canary, Easter, Samoa and Tahiti. Among the deep plumes that were not very well resolved in the earlier P-wave study, the S wave inversion shows a robust extension all the way to the CMB of the plumes beneath Cape Verde, Cook Island and Kerguelen. The presence of plumes rising from the base of the mantle but not reaching yet the surface in the Coral Sea, East of Solomon and South of Java is validated. Plumes such as Bowie, Eifel, Etna and Seychelles remain mostly confined to the upper mantle. However, the new S-wave images reopen the question on the depth extent of Iceland and Galapagos plumes. The weakening of the plume in the mid-mantle beneath Iceland is confirmed, but the S inversion clearly shows the presence of a low velocity zone at greater depth that was not visible in the P-wave images. For Galapagos, the new S-wave images show more clearly a possible connection of the plume with a broad low velocity anomaly in the lowermost mantle that feeds Easter as well. We will present the final S-wave plume images and will provide a synthesis of our findings in the light of existing ideas about plume characteristics and their superficial signature.
DE: 8450 Planetary volcanism (5480)
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 7207 Core and mantle
DE: 3640 Igneous petrology
DE: 1025 Composition of the mantle
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting