HR: 0800h
AN: T41D-1245    [Abstracts]
TI: Inferred Variations in Crustal Accretion Processes Along the Southwest Indian Ridge Near the Marion Hotspot
AU: * Stroup, D F
EM: dfs6676@fsu.edu
AF: Florida State University, Department of Geological Sciences, Tallahassee, FL 32306 United States
AU: Georgen, J E
EM: georgen@gly.fsu.edu
AF: Florida State University, Department of Geological Sciences, Tallahassee, FL 32306 United States
AB: The Southwest Indian Ridge (SWIR) presents a unique opportunity to study hotspot/ridge interactions in an ultra-slow spreading, highly segmented environment. We investigate the effects of the Marion hotspot on SWIR crustal accretion processes. More specifically, the goal of this study is to constrain the history of Marion/SWIR interactions by looking at temporal variations in SWIR magmatism, inferred from global gravity and bathymetry databases, for the last approximately 35 Myr. Marion lies in the central portion of the SWIR on 28 Ma crust, about 250 km south of the ridge axis and approximately 360 km to the east of the extremely long (750 km) offset Andrew Bain FZ. The region of study encompasses eight ridge segments and approximately 425 km of ridge axis, from the Andrew Bain FZ to the Discovery II FZ. Ridge offsets in the study area include both long-lived, well-developed transform faults as well as oblique discontinuities. To constrain temporal variability in crustal accretion, we consider shipboard bathymetry, satellite free-air gravity, and seafloor age data. We also calculate residual bathymetry, by removing a predicted lithospheric subsidence curve from GEBCO seafloor depth. Further, we utilize published calculations of mantle Bouguer and residual mantle Bouguer anomalies from Georgen et al. (2001). We examine both two-dimensional patterns using map projections and one-dimensional variations using quasi-axis-perpendicular profiles along GEBCO ship tracks. The data suggest that large inferred variations in rates of crustal accretion have occurred over the past approximately 35 Myr. Moreover, these variations are not always temporally correlated between the segments in the study region, nor are they symmetric about the ridge axis. To better constrain the style of crustal accretion processes along this highly-segmented, ultra-slow spreading ridge, we also compare the Marion-hotspot-influenced region of the SWIR to non-hotspot-affected sections of the ridge and to other hotspot-ridge systems.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3010 Gravity
DE: 3035 Midocean ridge processes
DE: 1206 Crustal movements--interplate (8155)
DE: 1219 Local gravity anomalies and crustal structure
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting