The Impact of Microbes for Seafloor Massive Sulfide Formation, Transformation and Dissolution

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Seafloor massive sulfide (SMS) deposits form on the modern ocean floor at active high-temperature hydrothermal vent systems through mixing of mineral-rich, advecting hydrothermal fluids with bottom seawater. They are mainly composed of pyrite and chalcopyrite and contain valuable metals such as copper. When oxygenated seawater penetrates the SMS, the sulfide minerals are exposed to abiotic oxidative weathering. Microbial activity considerably accelerates this process by catalyzing the precipitation of sulfide minerals, metal transport and mineral dissolution. Under certain circumstances iron-rich-silica-caps can be formed, which result in low oxygen concentrations below the caprock, thus sheltering the sulfide deposits from direct oxidative abiotic and biotic weathering and prolonging the lifetime of these deposits. Here we will examine the impact of microbial activity for SMS formation, transformation and dissolution of minerals under oxic and low oxygen conditions. We will combine molecular biological techniques with incubation experiments, microbial enrichment work and physiological studies. We will determine, which microbes are primarily responsible for the mineral transformation and metal mobilization and determine turnover rates and mineral modifications to predict, using adapted geochemical models, how microbial activity affects the lifetime of SMS deposits under different oxygen conditions.