Mount Etna–Iblean volcanism caused by rollback-induced upper mantle upwelling around the Ionian slab edge: An alternative to the plume model

Abstract

Volcanism in Sicily (Italy) at Mount Etna (0.5 Ma to present) and the Iblean Plateau (ca. 7.0–1.1 Ma) remains enigmatic, because it is located in close proximity to, but is laterally offset from, the Calabrian subduction zone. Previous work suggests that the volcanism results from a plume or from lateral mantle flow from underneath Africa through a slab window across a lithospheric step. Here I propose that Mount Etna and the Iblean volcanics are related to decompression melting of upper mantle material that is flowing around the southern Ionian slab edge to accommodate east-directed rollback of the Ionian slab that resumed in the Late Miocene. New three-dimensional fluid dynamic subduction models demonstrate that rollback-induced mantle return flow occurs in a quasi-toroidal fashion with a component of downwelling directly below and above the slab, and a component of upwelling next to the subduction zone with maximum upwelling observed next to the subslab region. Significant upwelling (≥71% of the maximum) is observed at 90–430 km depth and extends 55–660 km away from the projected distance of inferred arc magmatism above the slab edge. The models can explain the large spatial separation of as much as 430 km between intraplate volcanism in Sicily and arc magmatism during the past ∼7 m.y., and their contemporaneous activity. The maximum upwelling velocity in the models composes 32% of the trench rollback velocity. With rollback velocities up to 10–19 cm/yr during the past ∼8 m.y., the models predict maximum rollback-induced upper mantle upwelling velocities of 3.2–6.1 cm/yr below Sicily.