HR: 0800h
AN: T31A-0491    [Abstracts]
TI: Detailed Studies of the Axial Summit Trough of the East Pacific Rise 9-10N
AU: * Fornari, D J
EM: dfornari@whoi.edu
AF: Woods Hole Oceanographic Institution, 266 Woods Hole Rd., Woods Hole, MA 02543 United States
AU: Soule, S A
EM: ssoule@whoi.edu
AF: Woods Hole Oceanographic Institution, 266 Woods Hole Rd., Woods Hole, MA 02543 United States
AU: Escartin, J
EM: escartin@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, Laboratoire de Geosciences Marines 4 Place Jussieu, Paris, 75252 France
AU: Perfit, M
EM: perfit@geology.ufl.edu
AF: University of Florida, 241 Williamson Hall PO Box 112120, Gainesville, FL 32611 United States
AU: Tivey, M
EM: mtivey@whoi.edu
AF: Woods Hole Oceanographic Institution, 266 Woods Hole Rd., Woods Hole, MA 02543 United States
AU: Schouten, H
EM: hschouten@whoi.edu
AF: Woods Hole Oceanographic Institution, 266 Woods Hole Rd., Woods Hole, MA 02543 United States
AU: Ferrini, V L
EM: vferrini@whoi.edu
AF: Woods Hole Oceanographic Institution, 266 Woods Hole Rd., Woods Hole, MA 02543 United States
AB: The axial summit trough is a nearly continuous feature along the East Pacific Rise from 9-10 deg. N. The AST marks the central spreading axis of the ridge, is the site of the bulk of the volcanic eruptions, and hosts the majority of hydrothermal vent sites. In the past, the AST has been interpreted to be a purely tectonic or purely volcanic feature. Detailed analysis of sidescan imagery and high-resolution microbathymetry are used to identify the morphology and structural variability of the axial summit trough (AST) along the EPR crest in the study area. We use these data to address questions related to the causes for variability in width and character of the AST and how those parameters relate to the morphology and volcanic history of adjacent seafloor, relationships between lava flows and faults and fissures developed within ~4 km of the AST, and the frequency and size of volcanic eruptions. With constraints from microbathymetry data and knowledge of the detailed volcanic contacts along the EPR 9-10N AST derived from Alvin and towed camera data, we explore models of AST formation in an effort to better understand relationships between dike intrusion and how extensional strain is accommodated across the EPR axis. Assuming purely tectonic origins for the AST, 3D boundary element modeling suggests that dike widths and the levels to which dikes rise beneath the EPR axis are variable along-axis. For well-mapped portions of the AST we are able to infer the number of dikes needed to produce its current geometry, and as a result, the timescale of formation. Where the ridge is most volcanically active, we find that modeled dike widths and depths are unreasonable, and suggest that volcanic overprinting has modified the character of the AST. We conclude that both volcanic and tectonic processes are responsible for the formation of the AST and that the balance between these parameters controls the physical characteristics of the AST observed on the seafloor today.
DE: 3035 Midocean ridge processes
DE: 3045 Seafloor morphology, geology, and geophysics
SC: Tectonophysics [T]
MN: Fall Meeting 2005