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  4. Vertical changes of the Co and Mn speciation along a lateritic regolith developed on peridotites (New Caledonia)
 
research article

Vertical changes of the Co and Mn speciation along a lateritic regolith developed on peridotites (New Caledonia)

Dublet, Gabrielle  
•
Juillot, Farid
•
Brest, Jessica
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2017
Geochimica Et Cosmochimica Acta

Because they can host significant amounts of Co, the Mn-oxides are commonly considered as the major Co-bearing mineral species in lateritic environments. However, little is known about the process leading to the formation and/or the weathering of these Co-rich Mn-oxides. This lack of knowledge is mainly due to the fact that Co concentrations are too low in primary silicates for classical speciation analysis. In this study, we investigated both Co and Mn speciation in a 64 m thick lateritic regolith developed upon peridotites in New Caledonia, by combining High Energy Resolution Fluorescence Detection X-ray absorption Near Edge Structure (HERFD-XANES) spectroscopy at the Co K-edge with classical XANES spectroscopy at the Mn K-edge, bulk chemistry (ICP) and mineralogy (XRD). The results obtained provide new insights into the evolution of Co and Mn speciation as a function of the weathering stages. Co and Mn primarily occur as Co(II) and Mn(II, III) in olivine and serpentine in the bedrock. During the first weathering stage, these forms of Co and Mn are progressively oxidized toward Co(III) and Mn(III, IV), which occur mainly as Co(III)-bearing Mn(III/IV)-oxides in the transition between the saprolite and the laterite. In the uppermost lateritic horizons, long-time weathering resulted in a strong leaching of Co and Mn, and the remaining of these elements occurs as Co(II) and Mn(III) substituting for Fe(III) in goethite. This latter scavenging process emphasizes the importance of Fe-oxides for the long-term stabilization of Co and Mn in such deeply weathered laterites. (C) 2017 Elsevier Ltd. All rights reserved.

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Type
research article
DOI
10.1016/j.gca.2017.07.010
Web of Science ID

WOS:000411362000001

Author(s)
Dublet, Gabrielle  
Juillot, Farid
Brest, Jessica
Noel, Vincent
Fritsch, Emmanuel
Proux, Olivier
Olivi, Luca
Ploquin, Florian
Morin, Guillaume
Date Issued

2017

Publisher

Pergamon-Elsevier Science Ltd

Published in
Geochimica Et Cosmochimica Acta
Volume

217

Start page

1

End page

15

Subjects

Laterite

•

Cobalt

•

Manganese

•

Speciation

•

Weathering

•

X-ray absorption spectroscopy

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
IIE  
Available on Infoscience
October 9, 2017
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/141142
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