Kolumbo submarine volcano (Greece): An active window into the Aegean subduction system.
Submarine volcanism represents ~80% of the volcanic activity on Earth and is an important source of mantle-derived gases. These gases are of basic importance for the comprehension of mantle characteristics in areas where subaerial volcanism is missing or strongly modified by the presence of crustal/atmospheric components. Though, the study of submarine volcanism remains a challenge due to their hazardousness and sea-depth. Here, we report (3)He/(4)He measurements in CO2-dominated gases discharged at 500 m below sea level from the high-temperature (~220 °C) hydrothermal system of the Kolumbo submarine volcano (Greece), located 7 km northeast off Santorini Island in the central part of the Hellenic Volcanic Arc (HVA). We highlight that the mantle below Kolumbo and Santorini has a (3)He/(4)He signature of at least 7.0 Ra (being Ra the (3)He/(4)He ratio of atmospheric He equal to 1.39×10(-6)), 3 Ra units higher than actually known for gases-rocks from Santorini. This ratio is also the highest measured across the HVA and is indicative of the direct degassing of a Mid-Ocean-Ridge-Basalts (MORB)-like mantle through lithospheric faults. We finally highlight that the degassing of high-temperature fluids with a MORB-like (3)He/(4)He ratio corroborates a vigorous outgassing of mantle-derived volatiles with potential hazard at the Kolumbo submarine volcano.
Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Italy.
Andrea Luca
AL
Rizzo
Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Italy.
Antonio
A
Caracausi
CNRS, Géosciences Environnement Toulouse, 14 Avenue Edouard Belin, Toulouse, France.
Valèrie
V
Chavagnac
Department of Geology and Geoenvironment, National and Kapodistrian University of Athens, Panepistimiopolis, Zographou, Greece.
Paraskevi
P
Nomikou
Hellenic Centre for Marine Research, Institute of Marine Biology, Biotechnology and Aquaculture, Heraklion Crete, Greece.
Paraskevi N
PN
Polymenakou
Hellenic Centre for Marine Research, Institute of Marine Biology, Biotechnology and Aquaculture, Heraklion Crete, Greece.
Manolis
M
Mandalakis
Hellenic Centre for Marine Research, Institute of Marine Biology, Biotechnology and Aquaculture, Heraklion Crete, Greece.
Georgios
G
Kotoulas
Hellenic Centre for Marine Research, Institute of Marine Biology, Biotechnology and Aquaculture, Heraklion Crete, Greece.
Antonios
A
Magoulas
CNRS, Géosciences Environnement Toulouse, 14 Avenue Edouard Belin, Toulouse, France.
Alain
A
Castillo
Department of Geology and Geoenvironment, National and Kapodistrian University of Athens, Panepistimiopolis, Zographou, Greece.
Danai
D
Lampridou