Delamination of Continental Mantle Lithosphere driving volcanism at Mount Etna

As one of Europe’s most active volcanoes, Mount Etna poses a significant geohazard, with recurrent eruptive activity directly affecting a population of over a million in eastern Sicily. Accordingly, Mount Etna has been the in the focus of enduring scientific research concerning the relation of the volcano to the subduction of the Ionian Sea beneath the Calabrian Arc. Contrary to its famous neighbors in the Aeolian archipelago like Stromboli or Vulcano, Mount Etna is not a back-arc volcano. However, during the Holocene its overall intraplate-type geochemical composition has increasingly been influenced by subduction-related magma geochemistry. Its location and compositional anomalies have been explained with asthenospheric flows at the Ionian slab edge, slab windows in the region or oceanic slab brake-offs beneath Sicily.

This research is based on a combined inversion of ambient noise and earthquake-derived data to develop a comprehensive 3D shear-wave velocity model for the broader southern Central Mediterranean resolving the crust and upper mantle. The inversion utilizes an extensive dataset comprising 95,000 Rayleigh wave phase velocity dispersion curves and 40,000 Love wave curves from ambient noise and teleseismic earthquake measurements. Azimuthally anisotropic phase velocity maps were generated using a regularized least-squares approach and then inverted for depth using a stochastic inversion.

The resulting radially anisotropic 3D velocity model reveals a segment of delaminated but still attached African continental mantle lithosphere beneath Western and Central Sicily. A vertical tear beneath Mount Etna separates the delaminated lithosphere from the Ionian slab in the East. These two lithospheric units form a funnel allowing asthenospheric mantle to flow towards the crust beneath Mount Etna, picking up the subduction related contamination of its geochemical composition on its way. Where the mantle flow connects to the crust, we can evidence – together with local seismicity – the crustal pathways of magmatic fluids fueling Mount Etna. Our model not only explains the particular geochemical signature of Mount Etna but also relevant tectonic processes in the crust as surface expressions of the delamination and tearing processes like deep-seated thrusting in Central Sicily or observed uplift in northern Sicily.