Mantle degassing on a near shore volcano, SE Tyrrhenian Sea

Abstract

The presence of a seamount-like structure, located a few nautical miles offshore the Capo Vaticano Promontory (western Calabria, S Italy), was revealed by combined geophysical and geochemical investigation. The edifice covers~55 km 2 , with a top located at a depth of about 70 m below sea level, and consists mainly of a NW-trending structure orthogonally interrupted by minor ridges, the largest of which is affected by extensional faults. The top of the edifice hosts active vents, injected fluids that have been investigated for dissolved volatiles. Gas analyses revealed high CO 2 and CH 4 contents, several orders of magnitude above the atmospheric-type values expected for shallow, coastal marine waters, and a noteworthy enrichment in mantle-derived 3 He, which is an unambiguous indicator of the mantle origin of the fluids. Our results, combined with available data from the literature, suggest that the edifice is a tectonically controlled volcanic system, which presence near the Calabria region changes the role played by faults in the frame of the subduction process.

Pleistocene volcaniclastic units from North-Eastern Sicily (Italy): new evidence for calc-alkaline explosive volcanism in the Southern Tyrrhenian Sea

“…The results match those of similar deposits spread over the Mesima-Gioia Tauro and Reggio Calabria basins (De Rosa et al 2008) for which a possible explosive centre has been identified offshore from the Capo Vaticano promontory (Loreto et al 2015) while there is no clear correlation with rocks from the subaerial portion of the Aeolian archipelago.…”

“…The volcanic activity is located along the main regional faults and apart from the volcanism of the Aeolian Islands no other recent active volcanic centres were known. Loreto et al (2015) confirmed the existence of a buried volcano offshore Capo Vaticano (Calabrian Arc). That seamount, which is still venting volcanic volatiles, coincides with the volcanic edifice responsible for the nearby Pleistocene volcaniclastic units occurring inside the half-graben depressions of the Mesima-Gioia Tauro and Reggio Calabria basins (De Rosa et al 2001.…”

“…According to De Rosa et al (2008) it could represent the product of explosive activity from one or more volcanic centres active in the Southern Tyrrhenian domain during the last one million years. Such an eruption centre has been identified in the seamount located 6 miles off the western coast of the Calabria region (Loreto et al 2015), (Fig. 9).…”

“…The seamount located offshore from the Capo Vaticano promontory (Loreto et al 2015) looks to be very far away, (about 80 km to the North although compatible in age and chemistry (De Rosa et al 2008;De Ritis et al 2010) with the top located at shallow depth (about 70 m b.s.l.). The grain size characteristics of the pyroclastic material of VU7 and also of VU1, VU2, VU5, VU8 indicate a primary emplacement at a distance of less than 5 km from the vent, on a deep shore environment of the Sicilian continental margin, and subsequently remobilization and final redeposition away towards the northwest and north by means of sea currents.…”

“…The calcareous nannofossil associations with Pseudoemi liania lacunosa, Gephyrocapsa oceanica and Gephyrocapsa sp.3 (MNN19f biozone sensu Rio et al 1990) allowed us to ascribe the clayey formation to the Middle Pleistocene (Di Lentini et al 2000Lentini et al , 2008 Kamenov et al 2009, modified) on the left and geological sketch map of the study area showing the main outcropping formations and the volcaniclastic units (right). Black star -hypothetic volcanic edifice (Kezirian 1992a,b); black triangle -hypothesized volcanic edifice of Capo Vaticano (Loreto et al, 2015); 1 -beach deposits (Holocene); 2 -alluvial deposits (Holocene); 3 -gray-blue marly clay (Middle Pleistocene); 4 -volcaniclastic units; 5 -pre-Pleistocene substratum; 6 -traces of the stratigraphic sections; 7 -faults. al.…”