HR: 15:15h
AN: V23C-06 INVITED     [Abstracts]
TI: Post-Subduction Volcanism in the Baja California Peninsula, Mexico: The Effects of Tectonic Reconfiguration in Volcanic Systems.
AU: * Cañón-Tapia, E
EM: ecanon@cicese.mx
AF: CICESE Geology Dept., P.O. Box 434843, San Diego, CA 92143, United States
AU: Negrete-Aranda, R
EM: rnegrete73@yahoo.com.mx
AF: CICESE Geology Dept., P.O. Box 434843, San Diego, CA 92143, United States
AB: Late Cenozoic volcanism in the Baja California Peninsula records the effects of cessation of subduction at a previously convergent plate margin. Prior to 12.5 Ma the predominant volcanic activity had a calcalkaline signature. After 12.5 Ma, during the period of tectonic transition from a convergent to a strike-slip boundary, the style and composition of the magmatic products changed dramatically. It has been proposed that the origin of post-subduction "anomalous" magmas (i.e., adakites, Nb-enriched basalts, Mg-andesites) is linked to regional tectonic events such as the subduction of an active ridge, the break off of the subducted slab or the thermal equilibration of the stalled slab. None of these models, however, included information concerning the spatial- temporal or other physical characteristics of the volcanic products. Here we suggest an alternative model based on the concept of volcanic systems, in which the stress field and the tensile strength of the rock overlying the zones of partial melting plays a much more active role in controlling the occurrence of post-subduction volcanism than previously envisaged. Our model therefore allows us to reconcile the apparent contradictory observations concerning the spatial-temporal distributions of post-subduction volcanism in Baja California, and highlights the role played by tectonic reconfiguration.
DE: 8185 Volcanic arcs
DE: 8413 Subduction zone processes (1031, 3060, 3613, 8170)
DE: 8434 Magma migration and fragmentation
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly