HR: 08:35h
AN: U51B-03 [Abstracts]
TI: Numerical Study of the Influence of Crustal Rheological Layering and Thermal Perturbation on the Orogenesis of the Andean Fore-arc
AU: * Salazar, E F
EM: essalaza@ing.uchile.cl
AF: Departamento de Geologia, Universidad de Chile, Plaza Ercilla 803, Casilla 13518 correo
21,
Santiago, Santiago, Chile
AU: Gerbault, M
EM: gerbault@lmtg.obs-mip.fr
AF: Departamento de Geologia, Universidad de Chile, Plaza Ercilla 803, Casilla 13518 correo
21,
Santiago, Santiago, Chile
AU: Tassara, A
EM: andres@dgf.uchile.cl
AF: Departamento de GeofÃÂsica, Universidad de Chile, Blanco
Encalada 2002, Santiago, santiago, Chile
AB:
Diverse mechanical processes involved in build-up and segmentation of the Andes have been addressed (i.e.
fore-arc composition, shortening rates, back-arc strength, etc.). In this work we use the 2-D thermo-mechanical
simulation code PARAVOZ to study the effects of rheological differences between the upper and lower crust in the
fore-arc, on localisation of deformation. Results show that a relatively weak lower crust leads to wide and
homogeneous thickening of the crust, associated to an increase of the western component of descendent crustal
flow. A weak lower crust consequently achieves lower topography than the opposite case, and a better
transmission of stress and deformation to the west of the growing topography. Furthermore, testing the thermal
perturbation corresponding to an active-arc, shows an important control over the down-west flow of the lower
crust, at isotherms 400-500'C around 40 km depth. High temperatures rise the brittle-ductile transitions, favor
decoupling of the upper and lower crust, consequently diffusing deformation and smoothing the topography.
Rheology and temperature control the thickness and width of the competent layers, therefore determining the
Eastward or Westward vergence of modeled fault structures. Finally, we propose that a plateau-like deformation
might be controlled by a weak lower crust, independent of the thermal weakening produced by arc-magmatism,
while a stronger lower crust will produce a more Puna-like mountain building.
DE: 8104 Continental margins: convergent
SC: Union [U]
MN: 2007 Joint Assembly