  The effects of the hydration mechanism on continental crust recycling are
analyzed through a 2D finite element thermo-mechanical model. Oceanic slab
dehydration and consequent mantle wedge hydration are implemented using a
dynamic method. Hydration is accomplished by lawsonite and serpentine
breakdown; topography is treated as a free surface. Subduction rates of 1, 3,
5, 7.5 and 10 cm/y, slab angles of 30o, 45o and 60o and a mantle rheology
represented by dry dunite and dry olivine flow laws, have been taken into
account during successive numerical experiments. Model predictions pointed out
that a direct relationship exists between mantle rheology and the amount of
recycled crustal material: the larger the viscosity contrast between hydrated
and dry mantle, the larger the percentage of recycled material into the mantle
wedge. Slab dip variation has a moderate impact on the recycling. Metamorphic
evolution of recycled material is influenced by subduction style. TPmax,
generally representative of eclogite facies conditions, is sensitive to changes
in slab dip. A direct relationship between subduction rate and exhumation rate
results for different slab dips that does not depend on the used mantle flow
law. Thermal regimes predicted by different numerical models are compared to PT
paths followed by continental crustal slices involved in ancient and recent
subduction zones, making ablative subduction a suitable pre-collisional
mechanism for burial and exhumation of continental crust.
