Reconstructing of Flat Slab Subduction and Detachment beneath

							Reconstructing of Flat Slab Subduction and Detachment beneath Central Mexico

Vlad Manea1,2 and Michael Gurnis2

1-Computational Geodynamics Laboratory, Centro de Geociencias, Juriquilla, UNAM, Mexico
2-Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125


 Recent tomographic images beneath Central                                        35 Ma                         30 Ma
 Mexico revealed a perfectly flat slab segment
 extending several hundreds of km inland [Perez-
 Campos et al., 2008]. Also, the flat slab in not in
 direct contact with the overlying crust, and a low
 velocity layer decouples the two plates. Here we
 present a 3D geodynamic model tailored to
 realistic paleoreconstruction back to 35 Ma. Using                               25 Ma                         20 Ma
 a tracer technique described in details by Manea
 and Gurnis [2007], the models incorporate a low
 viscosity wedge and channel down to 300 km.
 Time-dependent dynamic models are solved using
 the finite element package CitcomS from CIG. The
 computations are performed within a spherical
 domain (r=1300 km, θ= 57°, ϕ=57°). The position
 of plate boundaries is imposed and set using the G-                              15 Ma                        10 Ma

 Plates software. The modeling results show that
 the subduction system in Central Mexico entered
 into flat slab regime at ~15 Ma. Later, at ~10 Ma,
 the slab started to break off and by ~5 Ma is
 completely detached. In Central Mexico the
 propagation of slab detachment is expressed by a
 short (2–3 m.y.), eastward-migrating pulse of                                     5 Ma                         0 Ma
 mafic volcanism that took place from ca. 11.5 to
 ca. 5 Ma to the North of the present Trans-
 Mexican Volcanic Belt [Ferrari, 2004]. The onset
 of flat slab (from volcanic rock dating, Ferrari et
 al., 1999) took place 17-12 Ma. Our models
 predict both, the onset of flat slab around 15 Ma
 and the slab detachment at ~10 Ma.
 Figure. Temperature evolution and the onset of flat slab (~15 Ma) and slab detachment (~10
 Ma) in Central Mexico.


References
Ferrari, L., López-Martinez, M., Aquirre-Díaz, G., and Carrasco-Núñez, G., Space-time patterns of Cenozoic arc volcanism in central
    México: from the Sierra Madre Occidental to the Mexican Volcanic Belt. Geology, vol. 27, no. 4, pp. 303-306, 1999.
Ferrari, L., Slab detachment control on mafic volcanic pulse and mantle heterogeneity in central Mexico, Geology, vol. 32, no. 1, pp. 77-
    80, 2004.
Manea, V.C., and Gurnis, M., Subduction zone evolution and low viscosity wedges and channels, Earth and Planetary Science Letters,
    vol. 264, issues 1-2, pp. 22 – 45, 2007.
Xyoli Pérez-Campos, YoungHee Kim, Allan Husker, Paul M. Davis, Robert W. Clayton,
Arturo Iglesias, Javier F. Pacheco, Shri K. Singh, Vlad Manea, Micael Gurnis, Flat Slab Subduction in the Vicinity of Mexico City,
    Geophysical Research Letter, doi:10.1029/2008GL035127, 2008.