HR: 12:05h
AN: T32A-08    [Abstracts]
TI: The onset of flat subduction in Central Mexico controlled by a low viscosity wedge.
AU: * Manea, V C
EM: vlad@geociencias.unam.mx
AF: Centro de Geociencias, UNAM,Campus Juriquilla, apdo. postal 1-742, Queretaro, QRO 76001, Mexico
AU: * Manea, V C
EM: vlad@geociencias.unam.mx
AF: Seismological Laboratory, Caltech, 1200E. California Blvd., MS 252-21, Pasadena, CA 91125, United States
AU: Gurnis, M
EM: gurnis@gps.caltech.edu
AF: Seismological Laboratory, Caltech, 1200E. California Blvd., MS 252-21, Pasadena, CA 91125, United States
AB: It is generally accepted that dehydration of subducting lithosphere transport fluids into the mantle wedge, causing a decrease in the viscosity. Such decreasing in viscosity can form a well-defined low viscosity wedge (LVW) or a low viscosity channel (LVC) on top of the subducting slab. Using numerical models we study the effect of low viscosity and channels on time-dependent geodynamic models. The results show a dramatic effect of low viscosity on the slab dip evolution through time. A reduction of the wedge viscosity with an order of magnitude produces the slab dip to increase from an initial 30° to 50° after 10 Ma of convergence. Also, the slab overthickening observed in previous published dynamic models due to slab attachment to the overriding plate, is eliminated by introducing a LVW or LVC for models with or without trench rollback. Our study shows two end member models, depending on the maximum depth extent of the LVW. Models with a LVW extending down to 400 km depth show a steep slab geometry (dip > 50°), whereas shallow LVW produces flat slabs, including perfectly flat slabs (dips = 0°). Assuming that slab and sediments dehydration are responsible for lowering the mantle viscosity, the maximum depth extent of the LVW is controlled by the age of the incoming plate and the convergence rate. Thus, significant variations in LVW geometry and viscosity have significant impact on the slab geometry and volcanic arc evolution through time.
DE: 0545 Modeling (4255)
DE: 0560 Numerical solutions (4255)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Joint Assembly