Electron microscopy investigation of the genetic link between Fe oxides/oxyhydroxides and nontronite in submarine hydrothermal fields

The two major components most frequently found in sediments near submarine hydrothermal fields are Fe oxides/oxyhydroxides and nontronite. Physico-chemical conditions in these environments vary from site to site and even within sites as the type and intensity of the hydrothermal activity change. The investigation of Fe oxides/oxyhydroxides and nontronite is helpful to constrain the specific conditions in which they formed or evolved, and thus to recreate the history of hydrothermal vents. Microbial activity is also involved in the formation of these mineral phases, which adds the interest of revealing processes at the interface of biological and inorganic phenomena. We investigated sediments from ten seafloor hydrothermal fields, most of them Recent sediments. They are rich in Fe oxides/oxyhydroxides and/or nontronite and/or Fe-talc. SEM analysis with energy-dispersive X-ray spectroscopy revealed many morphological types, among which vermicular habits are common, with chemical composi