Molybdenum Isotope Geochemistry in Marine Sediments II: Experimental Determinations of Mo Isotope Fractionation Under Sulfidic Conditions

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Transition elements play an essential role in the marine carbon and oxygen cycles, particularly because their stable isotopes offer significant potential for tracing or quantifying past and present chemical processes in the ocean. Molybdenum (Mo), whose marine geochemistry is dominated by the formation of various isotopic signatures, indicates significant potential as a paleoredox indicator.Laboratory experiments quantifying Mo fractionation in oxic environments have been carried out; however, Mo fractionation under reducing conditions have not been empirically investigated. A scientist from Oregon State University proposes a series of experiments to determine the geochemical mechanisms responsible for fractionating Mo isotopes in sulfidic marine environments. It is hypothesized that Mo isotope compositions in reducing continental margin marine sediments are controlled by Mo-sulfide adsorption to pyrite. To test the hypothesis, a suite of experiments would be done to measure sulfide-controlled Mo isotope fractionation. Achieving a quantitative understanding of Mo isotope behavior is needed for interpretating Mo isotope variations in the marine sediment record.In terms of the broader impacts, the principal investigator plans to collaborate with a scientist at Newcastle University. One high school student and one graduate student would be supported and trained as part of this project.