Geocheminar spring-2013

Shallow-sea hydrothermal vents have been documented on the summits of seamounts, on the flanks of volcanic islands, and in other near-shore environments characterized by high heat flow. Their easy accessibility, relative to deep-sea hydrothermal systems, makes them excellent natural laboratories to study a wide range of chemical, physical, and biological processes. This talk will present my recent investigations of geochemistry and microbiology from the shallow-sea hydrothermal vents off Milos Island (Greece), and will focus on attempts at understanding how the fluids got their unusual geochemistry (e.g., the occurrence of both a high- and low-salinity fluid relative to seawater (11 to 66 per mil), with extreme enrichment in arsenic (up to 78 ?M) in both fluid types), using a combination of elemental analyses and stable and radiogenic isotope data (oxygen, deuterium, and strontium). A follow-up investigation at the site indicated that, as a consequence of subsurface hydrothermal processes, associated seafloor microbial communities at the two sites with nearly equivalent temperature and pH were distinctly different. If time allows, I will discuss some of my upcoming research at two alkaline shallow-sea hydrothermal vents: The Strytan Hydrothermal Cones (Eyjafjordur, Iceland) and the Needle of Prony Hydrothermal System (PHS) (New Caledonia). Because of their unusual characteristics, both systems offer information about the possibility of life on other planets.