Geological interpretation of the CIFALPS2 seismic tomography data in the Ligurian Alps

In the Western Alps, rocks belonging to the fossil subduction zone are exceptionally well exposed, and structures related to the (U)HP exhumation stage are still preserved. Some recent studies have analyzed the along-strike variations in the deep tectonic structure of the Western Alps, but analysis was not extended southward to the Ligurian Alps, where geodynamic reconstructions have predicted the strongest upper-plate divergent motion that may have favored exhumation of (U)HP metamorphic rocks and associated mantle-wedge rocks. Here we analyze the deep tectonic structure of the Ligurian Alps as revealed by the first receiver-function profile and a new local earthquake tomography model based on data collected during the passive seismic experiments CIFALPS and CIFALPS2. We provide evidence for an exhumed mantle wedge and a former subduction channel preserved at shallow levels beneath the Ligurian Alps, above a shallow-dipping lower-plate Moho. We found that the lower boundary of the exhumed subduction channel is the most evident seismic-velocity interface beneath the Ligurian Alps, which may be easily misinterpreted as a Moho. Similar Moho-like interfaces are found beneath the exhumed (U)HP domes of eastern Papua New Guinea and the Dabie Shan, which suggests that the results of the CIFALPS experiments may be used as a reference case to improve the interpretation of the deep tectonic structure of other (U)HP terranes worldwide.