Metal sources in the actively forming seafloor massive sulfide deposit of the Kolumbo volcano: Insight from the basement rocks

The shallow submarine Kolumbo volcano , located in the 5 Ma-to-present Aegean volcanic arc in Greece, hosts an active hydrothermal system currently forming polymetallic seafloor massive sulfide (SMS) mineralization on the seafloor, with high As, Ag, Au, Hg, Sb and Tl contents. It is one of the few known SMS deposits associated with continental margin volcanism. The hydrothermal system of the Kolumbo volcano represents an active hybrid analogue style of epithermal and VMS mineralization. The particular geological setting of the Kolumbo volcano in the Anydros basin makes it a great natural laboratory to investigate the metal flux as the underlying units outcrop on the neighboring islands of Santorini, Ios and Anafi . To this day, it is not clear to which extend the metals in the fluid derive from a magmatic source or if they are leached from the basement rocks by magmatic-hydrothermal fluids. Whole rock geochemistry of the basement and sedimentary rocks allows identifying the potential metal reservoirs in the system. The basement rocks can add metals to the system either by leaching through magmatic-hydrothermal fluids or contamination of the melt by assimilation. Sulfur and Pb isotope analysis allow to track contribution of the basement rocks to the metals/ligands budget of the fluids by comparison with the sulfates and sulfides of the Kolombo SMS. Constraining the metal reservoirs involved in marine magmatic-hydrothermal systems is crucial to understand the formation of SMS and variability in the metal endowment between the deposits.