Precise determination of the cerium isotopic compositions of surface seawater in the Northwest Pacific Ocean and Tokyo Bay

We succeeded in determining the Ce isotopic composition ( 138Ce/ 142Ce) in seawater with an error of 2 σ m = 0.3–0.7 of ε unit. In this study, 1000–3000 L of seawater samples were passed through MnO 2 fibers to concentrate Ce and Nd for precise measurement of their isotope ratios. Four surface seawa...

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Bibliographic Details
Published in:Marine chemistry 2007-01, Vol.103 (1), p.1-14
Main Authors: Tazoe, Hirofumi, Obata, Hajime, Amakawa, Hiroshi, Nozaki, Yoshiyuki, Gamo, Toshitaka
Format: Article
Language:English
Subjects:
Cerium isotopic composition
Continental crust
Earth sciences
Earth, ocean, space
Exact sciences and technology
External geophysics
Geochemistry
Marine
Mid-ocean ridge basalt
Mineralogy
Neodymium isotopic composition
Northwest Pacific Ocean
Physical and chemical properties of sea water
Physics of the oceans
Rare earth element
Silicates
Surface seawater
Water geochemistry
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Summary:We succeeded in determining the Ce isotopic composition ( 138Ce/ 142Ce) in seawater with an error of 2 σ m = 0.3–0.7 of ε unit. In this study, 1000–3000 L of seawater samples were passed through MnO 2 fibers to concentrate Ce and Nd for precise measurement of their isotope ratios. Four surface seawater samples of the northwestern Pacific and a coastal sample in Tokyo Bay were analyzed. Most Ce isotope ratios in the surface water showed positive ε Ce values (+ 0.8 to + 1.4) in the northwestern Pacific Ocean. These values indicate that Ce in the surface water originates from the continental crust preferentially over mantle-derived materials. We examined binary mixing model between the continental crust and mid-ocean ridge basalt. However the model could not explain both isotopic compositions and concentrations, which implies that the atmospheric input was a possible pathway for Ce into the ocean. A negative ε Ce value was observed in Tokyo Bay, suggesting mantle-derived sources.
ISSN:0304-4203
1872-7581
DOI:10.1016/j.marchem.2006.05.008