HR: 0800h
AN: T31A-0474    [Abstracts]
TI: Axial Magma Chamber Properties of the Lau Back-arc Basin Spreading Centers
AU: * Jacobs, A M
EM: amjacobs@ucsd.edu
AF: Allison M. Jacobs, 9500 Gilman Dr. MC 0225, La Jolla, CA 92093-0225 United States
AU: Kent, G M
EM: gkent@ucsd.edu
AF: Allison M. Jacobs, 9500 Gilman Dr. MC 0225, La Jolla, CA 92093-0225 United States
AU: Harding, A J
EM: aharding@ucsd.edu
AF: Allison M. Jacobs, 9500 Gilman Dr. MC 0225, La Jolla, CA 92093-0225 United States
AB: From multichannel seismic data we have observed a nearly continuous axial magma chamber along much of the Central Lau Spreading Center, southern Eastern Lau Spreading Center, and southern Valu Fa Ridge. However, little is known about the seismic properties of the melt generating the reflectors. By employing stacking and waveform inversion methods from a similar study of the East Pacific Rise [ Singh et al., 1998], we distinguish seismic signals from the standard P-wave reflection as well as from a converted P- to S-wave reflection, referred to as P_meltS. Based on the inability of molten magma to withstand shear stresses, this later signal provides insight into where the axial magma chamber is nearly pure melt versus a more mushy mixture of melt and crystals. In the Lau Basin, the P_meltS signal has appeared at several locations along the Central Lau Spreading Center and southern Valu Fa Ridge. Correlating these sites of pure melt with the locations of hydrothermal vents and recent magmatic eruptions offer additional clues into the processes driving oceanic spreading, particularly in a back-arc environment.
DE: 3001 Back-arc basin processes
DE: 3025 Marine seismics (0935, 7294)
DE: 7220 Oceanic crust
DE: 7245 Mid-ocean ridges
SC: Tectonophysics [T]
MN: Fall Meeting 2005