Slab Detachment, Mantle Flow, and Crustal Collision in Eastern Sicily (Southern Italy): Implications on Mount Etna Volcanism

Abstract

New data and interpretations of the geodynamics of eastern Sicily point to deep crustal shortening taking place in the area. Reconstructions of the lithospheric system, seismicity distribution, and stress state in the crust indicate that deformation is expressed by a large thrust-ramp cutting through the entire lower plate. The tectonic structure is propagating directly beneath the Mount Etna volcano, one of the few active volcanoes in Europe. Geostructural interpretation of tomographic sections allows for interpretations of the compressional structure as originating in response to trench-parallel breakoff of the Ionian slab. Following the simple assumption that if a slab retreats, it must either be compensated or alternatively pushed by the fore-arc mantle, we argue that the opening of a gateway in the slab has encouraged the fore-arc mantle to flow toward the Mount Etna region. Mantle mobilization has had a twofold influence on both magmatic source mixing and the inception of underplating processes beneath the Mount Etna. A shortening prevailing over extension in the crust below the volcano seems to have a significant impact on the dynamics of the Mount Etna volcanic system, which manifested through anomalous signals over the last thousands of years. Since a tectonic inversion of previous dilatational magma pathways is expected in such a converging setting, the documented variations are believed to be consistent with a volcano experiencing a declining phase. Comparison with other extinct volcanic systems in the southern Tyrrhenian margin, lying atop a detached slab and involved in contraction, provides insights into the evolution of Mount Etna.

New geochemical and geochronological data on the Cenozoic Veneto Volcanic Province: Geodynamic inferences

“…Noteworthy, the importance of slab tears in controlling a) convective mantle cells around slabs and b) triggering of magmatic occurrences variously influenced (or even not influenced) by subduction related fluids has been convincingly proposed by Faccenna et al (2007). Such process seems to be effective to explain the Cenozoic spatio-temporal association of volcanic products having distinct magmatic affinity in and around the Italian peninsula (e.g., Southern Tyrrhenian, Sicily; Bianchini et al, 2008;De Ritis et al, 2019;Barreca et al, 2020), as well as to explain the occurrence of post-collisional intraplate magmatism in other areas of the world, e.g., in the Western Anatolia (Dilek and Altunkaynak, 2009;Prelević et al, 2015) and East Carpathian (Bracco Gartner et al, 2020).…”

A carbon-rich lithospheric mantle as a source for the large CO2 emissions of Etna volcano (Italy)

“…Recently, Barreca et al (2020) suggested the presence of a slab window in the subducting Ionian plate that allows portions of the shallow mantle wedge to flow in the opposite direction and toward Etna. Such a scenario could explain the presence of a slight subduction signature in the recent alkaline activity but not the high Nb/Ta of Etna magmas.…”

“…Such a scenario could explain the presence of a slight subduction signature in the recent alkaline activity but not the high Nb/Ta of Etna magmas. In fact, the slab window opened after the tholeiitic activity of Etna (Barreca et al, 2020), which possibly explains the decreasing Nb/Ta in the younger alkaline basalts where the older carbonatite-like signature is partially overprinted. Accordingly, CO 2 and volatile fluxes at Etna during its tholeiitic phase were likely even higher than now, as suggested by the postulated increase in H 2 O/CO 2 of the mantle source of Etna through time (Casetta et al, 2019).…”

Transtension at the Northern Termination of the Alfeo-Etna Fault System (Western Ionian Sea, Italy): Seismotectonic Implications and Relation with Mt. Etna Volcanism

“…The tectonic activity of the eastern flank of Mt. Etna must be framed within the geodynamic context of north-eastern Sicily and the western Ionian Sea, where regional processes occur [11,13,14,[23][24][25][26][27][28][29]. In particular, according to Monaco et al [30], the Timpe Fault System connects the transtensional faults characterizing the south-eastern sector of the volcano with a regional shear zone that extends offshore (the Alfeo-Etna Fault System of Polonia et al [9]; the North Alfeo Fault System of Gutscher et al [10]; Figure 1).…”

“…In addition, possible implications with volcanic activity are examined. The interpretation makes use of numerous studies already published by our research group (e.g., [2][3][4][5][9][10][11]18,22,28,30]), integrated by new seismological and marine geology data recently acquired in the offshore.…”