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Behaviour of impurity elements during the weathering of ilmenite

Published online by Cambridge University Press:  05 July 2018

I. Grey ,
C. MacRae ,
E. Silvester  and
J. Susini
I. Grey*
Affiliation:
CSIRO Minerals, Bayview Avenue, Clayton, Victoria 3168, Australia
C. MacRae
Affiliation:
CSIRO Minerals, Bayview Avenue, Clayton, Victoria 3168, Australia
E. Silvester
Affiliation:
Latrobe University, Albury-Wodonga Campus, Wodonga, Victoria 3689, Australia
J. Susini
Affiliation:
ESRF, 38043 Grenoble Cedex, France
*
*E-mail: ian.grey@csiro.au
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Abstract

X-ray spectromicroscopy has been applied to the characterization of weathered ilmenite sand samples from Australian localities. X-ray absorption near edge spectroscopy (Xanes) studies were performed at the K-edges of the major elements Fe and Ti and minor impurity elements Mn and Cr. An extended suite of reference samples with crystallite sizes ranging from 1 nm to μm size were measured to establish if the absorption edge characteristics were influenced by crystal size effects. No changes were detected for oxides of Cr3+, Fe3+ or Ti4+, but the mixed Fe2+/Fe3+ oxide, Fe3O4, showed an edge shift to higher energies (by 1.5 eV) in a nanocrystalline sample. The Xanes study of a composite ilmenite grain with an unweathered primary ilmenite core and a highly weathered rim showed that Fe was present as Fe2+ in the core and Fe3+ in the rim whereas Mn was present as Mn2+ in both core and rim. Chromium, which is incorporated into the grains during weathering, is present predominantly as Cr3+, although minor (~15%) Cr6+ also occurs in highly weathered grains. The absorption K-edges of Fe3+ and Mn2+ are shifted markedly (by 2–3 eV) to higher energies in titanate phases relative to the binary oxides Fe2O3 and MnO.

Keywords

weatheringilmeniteAustraliatitanium
Type
Research Article
Information
Mineralogical Magazine , Volume 69 , Issue 4 , August 2005 , pp. 437 - 446
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2005

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