Kinematics of slab tear faults during subduction segmentation and implications for Italian magmatism

Abstract

Tectonic activity in convergent plate boundaries commonly involves backward migration (rollback) of narrow subducting slabs and segmentation of subduction zones through slab tearing. Here we investigate this process in the Italian region by integrating seismic tomography data with spatiotemporal analysis of magmatic rocks and kinematic reconstructions. Seismic tomography results show gaps within the subducting lithosphere,which are interpreted as deep (100–500 km) subvertical tear faults. The development of such tear faults is consistent with proposed kinematic reconstructions, inwhich different rates of subduction rollback affected different parts of the subduction zone. We further suggest a possible link between the development of tear faults and the occurrence of regional magmatic activity with transitional geochemical signatures between arc type and OIB type, associated with slab tearing and slab breakoff.We conclude that lithospheric-scale tear faults play a fundamental role in the destruction of subduction zones. As such, they should be incorporated into reconstructions of ancient convergent margins, where tear faults are possibly represented by continental lineaments linked with magmatism and mineralization.