HR: 0800h
AN: V41D-0792    [Abstracts]
TI: The Baja California Peninsula During the Last 12.5 Ma as Example of the Role of Plate Stresses in Controlling Active Volcanism
AU: * Negrete-Aranda, R
EM: rnegrete73@yahoo.com.mx
AF: CICESE-Geology Department, PO Box 434843, San Diego, CA 92143, United States
AU: Contreras-Perez, J
EM: jcontreras@cicese.mx
AF: CICESE-Geology Department, PO Box 434843, San Diego, CA 92143, United States
AU: Cañón-Tapia, E
EM: ecanon@cicese.mx
AF: CICESE-Geology Department, PO Box 434843, San Diego, CA 92143, United States
AB: Late Cenozoic volcanism in the Baja California Peninsula records a major plate reorganization between the Farallon and North America plate boundary that started ca.12.5 Ma. A concomitant change in the style and geochemical diversity of volcanic activity during the last 12.5 Ma has been thoroughly documented, although the origin of post-subduction volcanism has remained debatable. In this work we used a finite element model to estimate the role played by stress changes in the evolution of volcanism in the Baja California Peninsula. The model consists of an elastic layer representing the North America plate resting on an incompressible viscous fluid approximating mantle rheology. Deformation in the model is driven by viscous and buoyant forces in the mantle, which in turn depend on the imposed boundary conditions. Our results show that during the active subduction stage a tensional-stress build up was present in the Comondu volcanic arc. By the end of subduction (12.5 to 6.5 Ma) the model indicates that the entire elastic plate experienced tension, therefore promoting the re- activation of old fractures and allowing the trenchward continuation of volcanic activity during this period. For younger times the model shows that tensional stresses increased one order of magnitude along the base of the elastic plate, favoring migration of volcanic activity back to the east. In all cases, the state of stress predicted by the model is in good agreement with the observed geologic record, therefore highlighting the relevance of the local stresses in controlling the location of active volcanism.
DE: 8104 Continental margins: convergent
DE: 8178 Tectonics and magmatism
DE: 8185 Volcanic arcs
DE: 8413 Subduction zone processes (1031, 3060, 3613, 8170)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting