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

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.