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Oceanic molybdenum isotope fractionation: Diagenesis and hydrothermal ridge-flank alteration

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Title Oceanic molybdenum isotope fractionation: Diagenesis and hydrothermal ridge-flank alteration
Names McManus, James (creator)
Nägler, Thomas F. (creator)
Siebert, Christopher (creator)
Wheat, C. Geoffrey (creator)
Hammond, Douglas E. (creator)
Date Issued 2002-12-19 (iso8601)
Note Copyrighted by American Geophysical Union.
Abstract Isotopic analyses of dissolved molybdenum are presented for sediment pore waters from a reducing
sedimentary basin and for fluids from a low-temperature ridge flank hydrothermal system. δ⁹⁸/⁹⁵Mo in
these fluids range from 0.8 to 3.5%₀ (relative to a laboratory standard), demonstrating that marine
sedimentary reactions significantly fractionate Mo isotopes. Within the upper 3 cm of sediment,
manganese oxide dissolution produces an isotopically light fluid relative to seawater (mean of four
analyses = 2.1 ± 0.1%₀ versus seawater = 2.3 ± 0.1%₀). Below 6 cm depth, authigenic Mo uptake results in
an isotopically heavier fluid (up to 3.5%₀) indicating that reducing sediments are likely to be a net sink for
isotopically light dissolved Mo. In contrast, fluid circulation within a low-temperature ridge-flank
hydrothermal system is a source of isotopically light Mo to the ocean having an end-member fluid of
~0.8%₀.
Genre Article
Topic molybdenum
Identifier McManus, J., T. Nägler, C. Siebert, C. G. Wheat, and D. Hammond, Oceanic molybdenum isotope fractionation: Diagenesis and hydrothermal ridge-flank alteration, Geochem. Geophys. Geosyst., 3(12), 1078, 2002. doi: 10.1029/2002GC000356

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