Lateral flow of African mantle below the nearby Tyrrhenian plate

The Quaternary magmatism of the Southern Tyrrhenian basin represents a rare example of an active volcanic arc system where ocean island basalt (OIB) and island arc basalt (IAB) magmas coexist. Although there is general agreement on the importance of the Ionian oceanic lithosphere subduction in the genesis of the IAB magmatism, the tectono-magmatic processes producing the coexisting OIB magmas are still poorly understood. Here we show that the geochemistry of the Quaternary Southern Tyrrhenian OIB-type magmatism (i.e. Ustica island and Prometeo, a previously unknown submarine lava field) is very similar to that of OIB-type volcanoes situated on the nearby African plate (i.e. Etna and Hyblean Plateau). Among the possible geodynamic scenarios proposed to explain the coexistence of OIB and IAB magmas in arc settings, we consider the development of a tear at the edge of the Ionian plate as the more likely mechanism to favour the flow of African asthenospheric mantle below the Tyrrhenian plate.