HR: 0800h
AN: V51B-0532    [Abstracts]
TI: On the Zoology of Mantle Upwellings : the case of the Pacific
AU: Davaille, A
EM: davaille@ipgp.jussieu.fr
AF: Institut de Physique du Globe, 4 Place Jussieu, PARIS cedex 05, 75 252 France
AU: * Bonneville, A
EM: bonnevil@ipgp.jussieu.fr
AF: Institut de Physique du Globe, 4 Place Jussieu, PARIS cedex 05, 75 252 France
AU: Stutzmann, E
EM: stutz@ipgp.jussieu.fr
AF: Institut de Physique du Globe, 4 Place Jussieu, PARIS cedex 05, 75 252 France
AB: The characteristics of intraplate volcanism in the Pacific are very diverse. There is probably more than $10^6$ seamounts on the Pacific seafloor created by past or present volcanism. Among them, a number are organized in alignments, some of which showing increasing ages along the track in the direction of plate motion. Sorting the latter by their track duration further shows two populations : a big peak around 20 Myr and a few tracks longer than 50 Myr, sometimes originating at an oceanic basaltic plateau. The Pacific presents also a number of isolated oceanic plateaus, as well as the Polynesian superswell, a region of anomalously shallow sea-floor several thousands of kms in extent with an unusually dense concentration of alignments. Tomographic images of the Pacific mantle reveal several 3D structures of slow velocities, presumably indicating hot material. Moreover, paleo-reconstructions show replication of volcanism over certain areas on a 100 Myr time-scale. In a heterogeneous viscous fluid like the mantle, several kinds of upwellings may develop, from the classical, mushroom-shaped, thermal plume to more complicated thermo-chemical structures. Fluid Mechanics studies give definite constraints on the necessary conditions for these upwellings existence, characteristics (spacing, recurrence time, temperature anomaly,.), and ability to reach the lithosphere. We therefore use those constraints to identify : 1) what types of upwellings could develop in the Earth's mantle, 2) what observations, if any, CAN be explained by a mantle upwelling, 3) what observations can NOT be explained by a mantle upwelling.
DE: 8180 Tomography
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 8125 Evolution of the Earth
DE: 1213 Earth's interior--dynamics (8115, 8120)
DE: 1645 Solid Earth
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting