Magma Channeling and Crustal Structure of a STEP Fault From Integrated Geological and Geophysical Data: The Central Aeolian Volcanoes (Southern Tyrrhenian Sea)

Abstract

Arc volcanism is commonly interpreted as the surface expression of subduction‐related magmatism and its spatial organization is often controlled by lithospheric structures. In arc‐back‐arc systems, slab retreat may promote the transition from compression to extension and the development of Subduction‐Transform Edge Propagator (STEP) faults. These latter accommodate the deformation along slab edges. A representative example of STEP fault is the Aeolian‐Tindari‐Letojanni fault system, a NNW–SSE‐striking shear zone affecting the central Aeolian arc and likely extending southward to the Ionian margin of Sicily. The Vulcano, Lipari, Salina islands form a NNW–SSE elongated Pleistocene volcanic belt emplaced on this shear zone. Here, we integrate and reinterpret available geological and geophysical data with new airborne gravity measurements to assess the structure of the Aeolian‐Tindari–Letojanni fault system and its relationship with volcanism. Our results indicate that the Vulcano–Lipari–Salina volcanoes can not be interpreted simply as the surface expression of aligned intracrustal magma reservoirs. Instead, they reflect a deeper tectonic structure related to a lithospheric‐scale discontinuity. Magnetic and gravity source distributions, basement uplifts, Moho undulations, and geometry of the magma plumbing systems reveal a tectono‐magmatic hierarchy in which lithospheric deformation primarily controls magma ascent and storage. We conclude that the Aeolian‐Tindari–Letojanni fault system acts as a lithospheric shear zone that dislocates both the crust and the Moho by focusing magma transfer along a NNW–SSE pathway. These results highlight the complexity of magma ascent across active shear zones and the broader role of STEP‐related volcanism in arc–back‐arc evolution.