Abstract

The exhumation of subducted lithosphere requires a mechanically weak zone at the interface between the subduction plane and the rigid overlying mantle peridotites with a viscosity greater than 10²⁰ Pa.s. At shallow depths (<40-50km) blueschists are exhumed in the accretionary wedge along the interface between the subducting plate and the overriding plate (Platt, 1993). At greater depth, serpentinites plays the role of a mechanically weak layer in cool continental subduction and acts as a lubricant, producing a return flow for the exhumation of eclogitic rocks. The close association of serpentinites and eclogites in the Monviso massif (Western Alps) allow the discussion of the concept of a subduction serpentinite channel. We propose that the Monviso ophiolitic massif corresponds to a section of a 50 km long serpentinite channel along which eclogitic blocks were exhumed between 60 and 45 Ma and ended when the European continental margin was involved in the southeast dipping subduction zone.