HR: 1400h
AN: T43A-01    [Abstracts]
TI: Deformation Patterns and Subduction Behavior of Continental Lithosphere Entering a Trench
AU: Steedman, C E
EM: steedman@usc.edu
AF: University of Southern California, Department of Earth Sciences 3651 Trousdale Parkway, Zumberge Hall Rm 117, Los Angeles, CA 90089, United States
AU: Kaus, B J
EM: kaus@erdw.ethz.ch
AF: University of Southern California, Department of Earth Sciences 3651 Trousdale Parkway, Zumberge Hall Rm 117, Los Angeles, CA 90089, United States
AU: Kaus, B J
EM: kaus@erdw.ethz.ch
AF: ETH Zurich, Haldenbachstrasse 44, Zurich, 8092, Switzerland
AU: * Becker, T W
EM: twb@usc.edu
AF: University of Southern California, Department of Earth Sciences 3651 Trousdale Parkway, Zumberge Hall Rm 117, Los Angeles, CA 90089, United States
AU: Okaya, D
EM: okaya@usc.edu
AF: University of Southern California, Department of Earth Sciences 3651 Trousdale Parkway, Zumberge Hall Rm 117, Los Angeles, CA 90089, United States
AB: We perform 2-D numerical simulations of continental lithosphere entering a subduction zone, to better understand deformation patterns resulting from subduction of a continental margin. The model consists of a subduction zone in which an attached slab drives subduction of a passive continental margin beneath an oceanic plate. A particle-based 2-D visco-elasto-plastic thermo-mechanical finite element code is employed to study the dynamics of the system. A novel feature of the code is that the resolution of the model can be significantly increased in selected parts of the domain, which allows for self-consistent modelling of mantle-lithosphere interaction. In the present study we employ this feature to study how lithospheric-scale deformation around and within the subduction zone is influenced by surface processes such as erosion, and by flow in the upper mantle. Using systematic 2-D numerical simulations, we explore the parameters that are dominant in controlling near- surface structures, both with regards to changes in topography and trench location, and subsurface features such as Moho undulations. The main parameters that have been varied are: the lithospheric density structure; the lithospheric age and temperature structure; the strength of the lower crust; the presence of a weak zone at the plate interface; the amounts of erosion; the upper boundary condition (free surface versus free slip); rheology (non-Newtonian versus Newtonian, viscous, visco-elasto-plastic); and finally the effect of an imposed slab breakoff. In all cases we track surface uplift, subduction evolution and rock exhumation history. We find that the strength of the overriding plate influences surface uplift and the shape of subsurface deformation, and that the density and thermal structure of the subducting plate affects trench motion. Denser slab roll back, and younger, lighter slabs advance, while neither slab rheology nor the presence of erosion greatly affect trench location. For all cases, we observe some degree of symmetric subduction, but the presence of a weak serpentinite zone between plates helps to decouple subduction.
DE: 8104 Continental margins: convergent
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