HR: 0800h
AN: T41E-1350    [Abstracts]
TI: Seamount Characteristics and Abundance as Proxy for Volcanic Accretion Style, Magma Supply, and Lithospheric Strength at the Southwest Indian Ridge
AU: * Mancinone, J I
EM: jim1715@uncw.edu
AF: Center for Marine Science University of North Carolina Wilmington, 5600 Marvin Moss Lane, Wilmington, NC 28409 United States
AU: Grindlay, N R
EM: grindlayn@uncw.edu
AF: Center for Marine Science University of North Carolina Wilmington, 5600 Marvin Moss Lane, Wilmington, NC 28409 United States
AB: Seamounts have been used as indicators of volcanic accretion style, magma supply, and lithospheric strength because they are of significant size (>50 m in height), indicating a steady magma source at the time of formation, and require strong lithosphere to support them. Seamount size, height, and population density will be analyzed along six segments of the Southwest Indian Ridge (SWIR) between 15°E and 35°E. The segments are offset by the 750 km-long Andrew Bain megatransform fault. Two segments to the northeast of the fault, thermally influenced by the Marion hotspot 250 km to the east, display an accretion style indicative of robust magma supply (shallow axial depths <1600 m, muted rift valley), creating hot, thin, weak lithosphere. In this area, seamount abundance should increase due to increased magma supply, while characteristic seamount height decreases, as weak lithosphere cannot support tall volcanic structures. Two segments to the southwest, thermally influenced by the Andrew Bain Fracture Zone, are accreting crust amagmatically through mechanical deformation (asymmetric rift valley, low magnetization, axial depths ~3600 m at most shallow). The Andrew Bain Fracture Zone acts as a cool mantle boundary for the southwestern segments, blocking the effects of the hotspot and creating cooler, stronger lithosphere that can support tall seamounts; seamount abundance should decrease due to low magma supply. Thermal effects of the transform fault and the hotspot on the ridge segments will be evaluated based on seamount abundance and characteristics in relationship to axial morphology, bounding discontinuities, and crustal thickness (as determined by gravity). Comparison will be made with two "normal" segments from 15°E to 25°E, a section of the SWIR far removed from large offsets and hotspot influence.
DE: 3035 Midocean ridge processes
DE: 3037 Oceanic hotspots and intraplate volcanism
DE: 3039 Oceanic transform and fracture zone processes
DE: 8178 Tectonics and magmatism
DE: 8414 Eruption mechanisms and flow emplacement
SC: Tectonophysics [T]
MN: Fall Meeting 2005