HR: 1340h
AN: T23B-1408    [Abstracts]
TI: Three-dimensional Geometry of Magma Chamber Roof and Faults from 3D Seismic Reflection Data at the Lucky Strike Volcano, Mid-Atlantic Ridge
AU: * Combier, V
EM: combier@ipgp.jussieu.fr
AF: Equipe de Geosciences Marines, Institut de Physique du Globe de Paris 4 Place Jussieu, Paris, 75252, France
AU: Seher, T
EM: seher@ipgp.jussieu.fr
AF: Equipe de Geosciences Marines, Institut de Physique du Globe de Paris 4 Place Jussieu, Paris, 75252, France
AU: Singh, S C
EM: singh@ipgp.jussieu.fr
AF: Equipe de Geosciences Marines, Institut de Physique du Globe de Paris 4 Place Jussieu, Paris, 75252, France
AU: Crawford, W
EM: crawford@ipgp.jussieu.fr
AF: Equipe de Geosciences Marines, Institut de Physique du Globe de Paris 4 Place Jussieu, Paris, 75252, France
AU: Cannat, M
EM: cannat@ipgp.jussieu.fr
AF: Equipe de Geosciences Marines, Institut de Physique du Globe de Paris 4 Place Jussieu, Paris, 75252, France
AU: Escartin, J
EM: escartin@ipgp.jussieu.fr
AF: Equipe de Geosciences Marines, Institut de Physique du Globe de Paris 4 Place Jussieu, Paris, 75252, France
AU: Carton, H
EM: hcarton@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Marine Geology and Geophysics 61 Route 9W - PO Box 1000, Palisades, NY, 10964-800, United States
AB: A three-dimensional (3D) seismic reflection survey was carried out during the SISMOMAR 2005 experiment covering an area of 18x3.8 km², which includes the Lucky Strike volcano and associated hydrothermal vent sites, part of the graben on top of the volcano, and extends out to the median valley bounding faults. The survey consisted of 39 lines shot at 100 m spacing using a 4.5 km-long streamer resulting in a sixty-fold coverage and 6.25 m CDP spacing. We present here the resulting 3D seismic volume migrated and converted to depth with the velocities from the 3D refraction survey (Seher et al). 3D processing allowed us to determine the geometry and depth of a bright reflector identified at depth beneath the volcano, which is interpreted as the roof of a magma chamber. The magma chamber reflector is 1 to 2 km wide and located 3.4±0.3 km deep beneath the seafloor. Several faults, among which the axial valley bounding faults and faults on the volcano, are imaged at depth and some reach the vicinity of the magma chamber reflector (< 1 km). The dip of faults is constrained; it is comprised between 40 and 55°, except the western bounding fault which dips 33±5°. A map of layer 2A thickness was derived from picks of layer 2A arrivals on the reflection volume, which shows a characteristic thinning of layer 2A associated with major faults. We also derived a high-resolution seafloor bathymetric map from picks of the seafloor arrival on the reflection volume. The 3D geometry of the magma chamber and faults, along with the overlying tectonic and accretion expressions at the seafloor provide new insights into the interplay between magmatic and tectonic processes at slow spreading ridges. By constraining the heat source and probably the main fluid paths locations, these results also provide a geometric pattern for the hydrothermal circulation feeding the vents.
DE: 7220 Oceanic crust
DE: 7245 Mid-ocean ridges
DE: 8178 Tectonics and magmatism
DE: 8416 Mid-oceanic ridge processes (1032, 3614)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting