New insights into hydrothermal vent processes in the unique shallow-submarine arc-volcano, Kolumbo (Santorini), Greece

Abstract

We report on integrated geomorphological, mineralogical, geochemical and biological investigations of the hydrothermal vent field located on the floor of the density-stratified acidic (pH ~ 5) crater of the Kolumbo shallow-submarine arc-volcano, near Santorini. Kolumbo features rare geodynamic setting at convergent boundaries, where arc-volcanism and seafloor hydrothermal activity are occurring in thinned continental crust. Special focus is given to unique enrichments of polymetallic spires in Sb and Tl (±Hg, As, Au, Ag, Zn) indicating a new hybrid seafloor analogue of epithermal-to-volcanic-hosted-massive-sulphide deposits. Iron microbial-mat analyses reveal dominating ferrihydrite-type phases, and high-proportion of microbial sequences akin to "Nitrosopumilus maritimus", a mesophilic Thaumarchaeota strain capable of chemoautotrophic growth on hydrothermal ammonia and CO2. Our findings highlight that acidic shallow-submarine hydrothermal vents nourish marine ecosystems in which nitrifying Archaea are important and suggest ferrihydrite-type Fe3+-(hydrated)-oxyhydroxides in associated low-temperature iron mats are formed by anaerobic Fe2+-oxidation, dependent on microbially produced nitrate.

Renewable chitin from marine sponge as a thermostable biological template for hydrothermal synthesis of hematite nanospheres using principles of extreme biomimetics

“…Iron is highly enriched in high temperature hydrothermal fluids as it is leached from host rocks during hydrothermal circulation of seawater [20]. It is also established that vent-derived iron can rapidly oxidize and precipitate around vents in the form of various oxides and sulfides [21,22]. Moreover, it has been proven that exomicrobiological iron oxide formation occurs also in hydrothermal vents in which bacteria are involved into stabilization of ferrihydride [23].…”

Constraints on the source of Cu in a submarine magmatic-hydrothermal system, Brothers volcano, Kermadec island arc

“…In addition to a magmatic volatile signature, acid-sulphate (advanced argillic) alteration, sulphosalts (e.g., enargite, Cu 3 AsS 4 ) typical for high-sulphidation conditions (Einaudi et al 2003) and high contents of economically important metals (e.g., Cu and Au) in some submarine arc and back-arc hydrothermal systems imply that they may be comparable to epithermal-porphyry deposits on land, such as the worldclass Far Southeast-Lepanto Cu-Au deposits (Philippines; Hedenquist et al 1998). This includes, for example, the magmatic-hydrothermal systems of Brothers volcano (Kermadec arc; de Ronde et al 2005;Berkenbosch et al 2012) and Kolumbo volcano (Hellenic arc; Kilias et al 2013Kilias et al , 2016, as well as SuSu Knolls in the Manus back-arc basin Yeats et al 2014;Thal et al 2016). Hence, arc-hosted hydrothermal systems are characteristically distinct in terms of their chemical and mineralogical composition compared to those along midocean ridges, which were interpreted to be the classic modern analogues of volcanic-hosted massive sulphide (VHMS) deposits mined on land (Hannington et al 1998de Ronde et al 2014;Keith et al 2016b).…”

Numerical simulations of tsunamis generated by underwater volcanic explosions at Karymskoye lake (Kamchatka, Russia) and Kolumbo volcano (Aegean Sea, Greece)

“…To investigate the consequences of an eventual future eruption of Kolumbo, we fix the position of the potential explosion corresponding to actual Kolumbo crater centre and systematically test different initial explosion powers. Assuming a future central eruption is justified by the morphology of the volcano (a well-developed central and no peripheral vents on the flanks of the volcano; Sigurdsson et al, 2006; and presence of active high-temperature fumarolic vents in the crater Kilias et al, 2013). Switching the explosion from the centre to the flanks would not alter significantly our results in terms of wave arrival times and amplitudes of incoming waves.…”

“…The last recorded volcanic activity at Kolumbo took place in 1650 AD and produced ash plumes that perforated the water surface, ash falls and tsunami on the coasts of the neighboring islands, and around 70 fatalities by volcanic gases in Santorini (Fouqué, 1879;Dominey-Howes et al, 2000;Nomikou et al, 2012b). The choice of Kolumbo is motivated by evidences of seismicity beneath the volcano (Bohnhoff et al, 2006;Dimitriadis et al, 2009), the existence of an active crustal magma chamber (Dimitriadis et al, 2010), intense CO 2 degassing from a hydrothermal field (Sigurdsson et al, 2006;Nomikou et al, 2013a;Kilias et al, 2013), and accumulation of acidic water in the crater ).…”