HR: 1340h
AN: T13B-1364    [Abstracts]
TI: Thermal Models for Southern Mexico and Guatemala and the Position of the Volcanic Belt
AU: * Manea, M
EM: mary@ollin.igeofcu.unam.mx
AF: Instituto de Geofisica, UNAM, IGEF UNAM, Av. Universidad, 3000, Mexico, D.F 04510 Mexico
AU: Manea, V C
EM: vlady@ollin.igeofcu.unam.mx
AF: Instituto de Geofisica, UNAM, IGEF UNAM, Av. Universidad, 3000, Mexico, D.F 04510 Mexico
AU: Kostoglodov, V
EM: vladi@servidor.unam.mx
AF: Instituto de Geofisica, UNAM, IGEF UNAM, Av. Universidad, 3000, Mexico, D.F 04510 Mexico
AB: A finite element method is applied to model the thermal structure of the subducted Cocos plate and overlying mantle wedge beneath the southern part of Mexico and Guatemala. A numerical scheme solves a system of 2D Navier-Stokes equations and a 2D steady state heat transfer equation with strong temperature dependent viscosity. The geometry of the subducting Cocos slab is inferred from seismicity. In Southern Mexico (Chiapas) the modern volcanic front has a remote and tilted position, corresponding to $\sim$200 km depth from the slab surface. In Guatemala the position of the volcanic chain is in good agreement with the high mantle wedge temperature zone ($>$1300$^{o}$ C). On the other hand the remote position of the modern volcanic front in Chiapas does not correspond with maximum temperature zone in mantle wedge predicted by the steady state thermal models. The mantle wedge high temperature zone is situated just below the coast, corresponding to the position of the old Miocene volcanic arc in this region. Recent studies suggest that the Cocos plate just south of Tehuantepec Ridge (TR) has had a non-rigid behaviour, probably acting as a microplate. A tectonic model constrained by the structural and morphological features observed in the bathymetry of the TR and surrounding ocean floor in the Guatemala Basin, shows that the velocity of this microplate decreased down to $\sim$2 cm/yr between 14 to 9 Myr ago. This slowing down would have induced a strong disturbance in the mantle wedge flow beneath Chiapas, and therefore a migration of the volcanic front to the more inland present day position. Since the steady state thermal models are not able to explain the position of the modern volcanic arc in Chiapas, we suggest that a non steady-state thermal model needs to be applied in this region, taking into account a possible variation of the slab geometry and age through the time.
DE: 7220 Oceanic crust
DE: 7223 Seismic hazard assessment and prediction
DE: 8150 Plate boundary--general (3040)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting