HR: 1330h
AN: B12A-0755    [PDF]
TI: A New View of 3-D Magma Chamber Structure Beneath Axial Seamount and Coaxial Segment: Preliminary Results from the 2002 Multichannel Seismic Survey of the Juan de Fuca Ridge
AU: * Kent, G
EM: gkent@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, IGPP-0225 UCSD, San Diego, CA 92093 United States
AU: Harding, A
EM: aharding@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, IGPP-0225 UCSD, San Diego, CA 92093 United States
AU: Babcock, J
EM: jbabock@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, IGPP-0225 UCSD, San Diego, CA 92093 United States
AU: Orcutt, J
EM: jorcutt@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, IGPP-0225 UCSD, San Diego, CA 92093 United States
AU: Detrick, R
EM: rdetrick@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Geology and Geopyhsics, Woods Hole, MA 02543 United States
AU: Canales, J P
EM: jpcanales@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Geology and Geopyhsics, Woods Hole, MA 02543 United States
AU: Van Ark, E
EM: emilyva@mit.edu
AF: Woods Hole Oceanographic Institution, Department of Geology and Geopyhsics, Woods Hole, MA 02543 United States
AU: Carbotte, S
EM: carbotte@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, PO Box 1000 61 Route 9W, Palisades, NY 10964 United States
AU: Diebold, J
EM: johnd@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, PO Box 1000 61 Route 9W, Palisades, NY 10964 United States
AU: Nedimovic, M
EM: mladen@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, PO Box 1000 61 Route 9W, Palisades, NY 10964 United States
AB: In the summer of 2002, a multichannel seismic (MCS) experiment was conducted across all segments of the Juan de Fuca Ridge, including Axial seamount and Coaxial segment. These two segments were surveyed over a twelve-day period, with a lengthy excursion southward to the Vance/Cleft segments due to sea-state. In total, some 20 MCS profiles were collected in these two areas, including a dense survey over Axial seamount. Not to disappoint, magma bodies were imaged beneath both the Axial and Coaxial segments, although absent along portions of Coaxial where previous work suggested sub-surface melt accumulations; in contrast, a large magma body was imaged along the southeast flank of Axial seamount in a region thought to be devoid of significant amounts of melt. MCS profiling across Axial seamount revealed a very complex set of reflections, with significant depth variations. The two-way travel-time between seafloor and melt sill reflectors varied between 600 ms to 1200 ms, with a minimum depth of about 1400 m bsf based on travel-time modeling of individual gathers. Melt appears to underlie most of the caldera, with depth variations of at least 600-800 m. Outside of the caldera, most of the melt is observed extending outward, along the southeast flank of Axial seamount to a distance of 12 km and appears to be quite extensive. No significant melt bodies were observed along either of the ridge-related rift zones. A magma chamber reflector was also seen along extended parts of Coaxial segment, in particular a continuously bright event was observed in between the conjugate set of ridges between $46\deg$25'N and $46\deg$15'N. This region was the site of a recent extrusive event, although the source for this eruption was thought to lie to the south, around $46\deg$09'N. Interestingly, the southern section of Coaxial appears to be devoid of such a melt-lens. Further south, toward Helium basin, a small stranded melt-lens was imaged at approximately $46\deg$05'N. Three-dimensional, interactive "fly-throughs" of magma chamber structure will be presented.
DE: 0400 Biogeosciences
DE: 3035 Midocean ridge processes
SC: Biogeosciences [B]
MN: 2003 Fall Meeting