Thermomechanical modeling of slab eduction

Plate eduction is a geodynamic process characterized by normal-sense coherent motion of previously subducted continental plate. This mechanism may occur after slab detachment has separated the negatively buoyant oceanic plate from the positively buoyant orogenic root. Eduction may therefore be partly responsible for exhumation of high pressure rocks and late orogenic extension. We used two-dimensional thermomechanical modeling to investigate the main features of the plate eduction model. The results show that eduction can lead to the quasi adiabatic decompression of the subducted crust (approximate to 2 GPa) in a timespan of 5 My, large localized extensional strain in the former subduction channel, flattening of the slab, and a topographic uplift associated with extension of the orogen. In order to further investigate the forces involved in the eduction process, we ran systematic parametric simulations and compared them to analytic plate velocity estimations. These experiments showed that eduction is a plausible mechanism as long as the viscosity of the asthenospheric mantle is lower than 10(22) Pa.s while subduction channel viscosity does not exceed 10(21) Pa.s. We suggest that eduction can be a viable geodynamic mechanism and discuss its potential role during the orogenic evolution of the Norwegian Caledonides.