HR: 0800h
AN: T11C-0729    [Abstracts]
TI: Competing Effects of Ridge Proximity and Slab Strength on Slab Detachment
AU: * Andrews, E R
EM: andrews@geology.ucdavis.edu
AF: UC Davis, Department of Geology, Davis, CA 95616, United States
AU: Billen, M I
EM: billen@geology.ucdavis.edu
AF: UC Davis, Department of Geology, Davis, CA 95616, United States
AB: The detachment of lithosphere from a subducted plate causes observable changes in subduction zones by affecting mantle dynamics and plate tectonics. Knowledge of the dynamics of slab detachment and its signature in the overlying surface is necessary for a complete understanding of the deformation and fate of subducted slabs and may provide constraints on the rheology of subducting lithosphere and the upper mantle. Early evidence supporting slab detachment includes observations of gaps in hypocentral distributions and within tomographic images of subducted slabs. The process has also been called upon to explain observed magmatism, uplift, extension, and metamorphics, but few studies have explored or demonstrated a link between these processes and slab detachment. A proposed cause of slab detachment is the approach of buoyant features such as a spreading ridge to subduction zones, a scenario that has previously not been tested using fully-dynamic numerical models including a non-Newtonian rheology. We present dynamic two-dimensional models of ridge subduction exploring the dependence of detachment occurrence and resultant surface effects on subducted slab length, distance of the ridge from the trench, spreading rate, and lithospheric yield strength. We compare model results with surface observations in Baja California, where the approach of the East Pacific Rise to the trench may have led to detachment of the Cocos slab.
DE: 4255 Numerical modeling (0545, 0560)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8159 Rheology: crust and lithosphere (8031)
DE: 8162 Rheology: mantle (8033)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting