HR: 16:20h
AN: V44A-02 INVITED    [Abstracts]
TI: Numerical modeling of mantle wedge processes and exhumation of UHP mantle in subduction zones
AU: * Gorczyk, W
EM: weronika.gorczyk@erdw.ethz.ch
AU: Gerya, T V
EM: taras.gerya@erdw.ethz.ch
AF: Department of Geosciences, Swiss Federal Institute of Technology, Zurich, CH 8092, Switzerland
AU: Guillot, S
EM: sguillot@ujf-grenoble.fr
AF: LGCA, CNRS, University of Grenoble, 1381 rue de la Piscine, BP53, Grenoble, 3841, France
AU: Connolly, J A
EM: james.connolly@erdw.ethz.ch
AF: Department of Geosciences, Swiss Federal Institute of Technology, Zurich, CH 8092, Switzerland
AU: Yuen, D
EM: daveyuen@gmail.com
AF: Department of Geology and Geophysics, University of Minnesota, Minnesota, 55455-0219, United States
AB: The upwelling of subduction generated partially molten rocks is potentially a mechanism for the exhumation of UHP rocks through the mantle wedge. We investigated this processes using a 2-D coupled petrological- thermomechanical model that incorporates slab dehydration and water transport as well as partial melting of mantle and crustal rocks. This approach allows us to study the dynamics of mantle wedge processes including evolution of partially molten plumes and their interaction with surrounding dry mantle.
To study the internal structure of the plumes we used ultra-high resolution numerical simulations with 10 billion active markers to detail the internal structure of natural plumes originating from the slab. The plumes consist of partially molten hydrated peridotite, dry solid mantle and subducted oceanic crust, which may comprise up to 12 volume % of the plume. As the plumes grow and mature these materials mix chaotically resulting in attenuation and duplication of the original layering on scales of 1-1000 m. Comparison of numerical results with geological observations from the Horoman ultramafic complex in Japan suggests that mixing and differentiation processes related to development of partially molten plumes above slabs may be responsible for strongly layered lithologically mixed (marble cake) structure of asthenospheric mantle wedges.
The recent discovery of garnet bearing peridotites in the subduction zone of the Great Antilles in Hispaniola has raised questions about the process that leads to their exhumation. To evaluate whether upwelling plumes are a plausible exhumation mechanism we investigated the dynamics of subduction of slow spreading ridges. The results show that subduction of strongly serpentinized oceanic plate causes strong dehydration of the slab and leads to a rheological weakening of the interface between subducting and overriding plate. This weakening triggers trench retreat and massive asthenospheric upwelling into the gap between the two plates. The P-T paths computed for this scenario can explain exhumation of UHP (4GPa) rocks.
DE: 0545 Modeling (4255)
DE: 1031 Subduction zone processes (3060, 3613, 8170, 8413)
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 3613 Subduction zone processes (1031, 3060, 8170, 8413)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting