Amagmatic Subduction Produced by Mantle Serpentinization and Oceanic Crust Delamination

Recycling of oceanic lithosphere and serpentinized peridotites into the mantle leads to dehydration melting and volcanic arcs. However, the mechanism of the occurrence of long-term volcanic gap in subduction zones remains poorly understood. Two-dimensional thermomechanical numerical models focusing on resisting the transport of the major hosts of hydrous minerals to mantle depths, show that thin oceanic crust together with rheologically weak and buoyant serpentinized mantle could result in hydrated lithologies piling up in the accretionary wedge and no or sparse occurrence of arc magmatism. This scenario may occur during subduction of oceanic lithosphere formed at (ultra)slow-spreading margins characterized by thin crust and extensive mantle serpentinization, which is a plausible explanation for the arc gaps in the Alps and southern Tibet.