Sulfur biogeochemistry of pore waters and sediments from IODP Expedition 307

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Sediments and pore waters are carriers of biogeochemical signals for present and past microbial activity. The present project deals with diagenetic processes in the deep biogeochemical sulfur-iron cycle of sediments recovered from the coral-bearing Challenger Mound and surrounding sedimentary sites (IODP Expediton 307). We will identify those reactions that characterize the microbial sulfur transformations by means of inorganic and stable isotope geochemical pore water and solid phase investigations. The project will focus on the potential of the contents and sulfur and oxygen isotopic composition of pore water sulfate and sulfide minerals as well as iron speciation to reflect the history of geomicrobial reactions in deeply buried marine sediments. The project will also address the question of the role of the Miocene sediments underlying the carbonate mound for driving ongoing sulfur diagenesis by a deep biosphere via methane as intermediate substrate.