Authors
Yoshio Takahashi, Alain Manceau, Nicolas Geoffroy, Matthew A Marcus, Akira Usui
Publication date
2007/2/15
Journal
Geochimica et cosmochimica acta
Volume
71
Issue
4
Pages
984-1008
Publisher
Pergamon
Description
The oxidation state and mineral phase association of Co, Ce, and Pb in hydrogenetic, diagenetic, and hydrothermal marine ferromanganese oxides were characterized by X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy and chemical extraction. Cobalt is trivalent and associated exclusively with the Mn oxide component (vernadite). Cerium is tetravalent in all genetic-type oxides (detection limit for Ce(III)∼5 at. %), including Fe-rich areas (ferrihydrite) of hydrogenetic oxides, and is associated primarily with vernadite. Thus, the extent of a Ce anomaly does not result from variations in redox conditions, but appears to be kinetically controlled, decreasing when the growth rate increases from hydrogenetic to diagenetic to hydrothermal oxides. Lead is divalent and associated with Mn and Fe oxides in variable proportions. According to EXAFS data, Pb is …
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Scholar articles
Y Takahashi, A Manceau, N Geoffroy, MA Marcus… - Geochimica et Cosmochimica Acta, 2007
Y Takahashi, A Manceau, N Geoffroy, MA Marcus… - Geochimica et Cosmochimica Acta, 2007