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Molybdenum behavior during early diagenesis: Insights from Mo isotopes

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Title Molybdenum behavior during early diagenesis: Insights from Mo isotopes
Names Poulson Brucker, Rebecca L. (creator)
McManus, James (creator)
Severmann, Silke (creator)
Berelson, William M. (creator)
Date Issued 2009-06-18 (iso8601)
Note Copyrighted by American Geophysical Union.
Abstract We present molybdenum isotope and concentration data from 14 sites in the eastern Pacific from the
central California to the Peru margin. The environments studied have been chosen to represent a broad
range in oxidation-reduction (redox) potential, which provide a framework for the behavior of this redox-sensitive
element. Manganese-rich hemipelagic sediments from the eastern tropical Pacific have a mean
characteristic Mo isotope signature (δ⁹⁸/⁹⁵Mo = -0.49 ± 0.04%₀, two times the standard deviation of the
mean (2 SDOM) with n = 14) that reflects fractionation between ocean water and authigenic Mo associated
with Mn oxides. Authigenic Fe-Mo-S deposits from reducing continental margin settings also have a
characteristic Mo isotopic signature (δ⁹⁸/⁹⁵Mo = 1.64 ± 0.04%₀, 2 SDOM with n = 136). Both of these
values are in contrast to highly sulfidic (>11 μM H₂Saq) restricted basin environments, which contain Mo
isotope values analytically indistinguishable from seawater. In terms of the Mo isotope composition, the
modern oceanic Mo sink is dominated by continental margin "type" environments where δ⁹⁸/⁹⁵Mo =
~1.6%₀ and Mn-rich sediments where δ⁹⁸/⁹⁵Mo = approximately -0.5%₀, with a minor contribution from
euxinic settings where H₂Saq > 11 μM.
Genre Article
Topic molybdenum
Identifier Poulson Brucker, R. L., J. McManus, S. Severmann, and W. M. Berelson (2009), Molybdenum behavior during early diagenesis: Insights from Mo isotopes, Geochem. Geophys. Geosyst., 10, Q06010. doi: 10.1029/2008GC002180

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