Hydrothermal Fluid Particle Geochemistry of Submarine Vents in Kos Island, Aegean Sea East Mediterranean

Abstract

The study aims to fill the gap of knowledge in the literature concerning submarine hydrothermal activity on the eastern part of Hellenic Volcanic Arc. Hydrothermal fluids were collected by scuba diving in active shallow hydrothermal venting areas on Kos Island in the Aegean Sea in East Mediterranean. Analysis was carried out in suspended particles for Fe, Mn, Cu, Pb, Cd, Ca, Ba, Sr, Li, Al and Si. During sampling, gas and water flux was measured and gas/water ratios were estimated. The data presented significant time and spatial variability. The gas flux values in Kephalos Bay varied from 2 to 126 L/h and water flux varied from 60 to 122 L/h. In Bros Thermi the gas flux values varied from 4.5 to 60 L/h and the water flux was found to be from 16.5 to 96 L/h. The suspended particulate matter (SPM) flux varied from 0.93 to 8.64 mg/L and between 0.21 and 20.94 mg/L respectively at two sites studied. Metal/Al ratios also varied significantly within a short distance. The pH of hydrothermal waters was from 5.50 to 5.95 in Kephalos Bay and from 6.09 to 6.53 in Bros Thermi suggesting either different mixing of fluids with seawater deeper in the substrate or perhaps that gases CO2 and H2S control pH values. The main scope of this research is to evaluate the fluxes of gas and water and study the main particulate geochemistry of hydrothermal venting fluids. Hydrothermal particles from the submarine vents studied were dominated by Fe, Ca, Si and Al and strongly enriched in Mn, Cu, Pb and Ba. Based on Metal/Al ratios, it is suggested that there are two distinct hydrothermal reservoirs in Kos. The chemistry of the particles emitted from seeps strongly influence both the marine sediment geochemistry and element distribution locally on the sea bottom while subjected to further transportation, hydrothermal particulates could also affect a much greater region.