Along-strike variations in the fossil subduction zone of the Western Alps revealed by the CIFALPS seismic experiments and their implications for exhumation of (ultra-) high-pressure rocks

In complex plate-boundary settings, a reliable 3-D geophysical characterization of the deep tectonic structure is fundamental starting point for breakthrough in analysis processes controlling plate subduction and (U)HP rock exhumation. The Western Alps host one best-studied fossil zones worldwide, with well-defined 2-D based on recent experiments. However, full its still lacking. Here we present series new receiver function cross-sections across northern southern Alps, validated complemented by S-wave velocity model from ambient-noise tomography that provides additional constraints between profiles. We document marked change Moho attitude where eastward-dipping European reaches ∼45 km depth beneath Gran Paradiso dome, to ∼70 equivalent Dora-Maira dome. This takes place over few tens kilometers was likely emphasized deformation slab during subduction. wedge much thicker south than north, mantle-wedge rocks are deeply involved orogeny exclusively south, coesite found continental at several locations. Our detailed information first-order next-generation thermo-mechanical numerical models may help explain lateral variations exhumation style revealed geologic record.