Most of the present-day ocean floor is continuously being consumed in subduction zones, but large fragments of oceanic crust (ophiolites) have also been recognized on land. The process by which oceanic crust is separated from the subducting slab remains enigmatic, and several competing hypothesis have been proposed in the past.
Based on numerical experiments we suggest that serpentinized mantle, formed in the outer rise regions of subduction zones, may provide a mechanically weak horizon within which basal detachment of the oceanic crust is feasible. Deformation of this serpentinized layer may lead to decoupling and separation of oceanic crust from the downgoing slab. Fragments of the former oceanic crust can underplate the accretionary wedge or be exposed on continental crust, whereas the skinned lithospheric part of the slab subducts into the mantle.