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Fe-Mn cation ordering in fayalite–tephroite (FexMn1−x)2SiO4 olivines: a neutron diffraction study

Published online by Cambridge University Press:  05 July 2018

S. A. T. Redfern ,
K. S. Knight ,
C. M. B. Henderson  and
B. J. Wood
S. A. T. Redfern
Affiliation:
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK
K. S. Knight
Affiliation:
ISIS, Rutherford Appleton Laboratory, Oxon, OX11 0QX, UK
C. M. B. Henderson
Affiliation:
Department of Earth Sciences, University of Manchester, Oxford Road, Manchester, MI3 9PL, UK
B. J. Wood
Affiliation:
Department of Geology, University of Bristol, Queens Road, Bristol, BS8 1RJ, UK
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Abstract

Time-of-flight neutron powder diffraction has been employed to determine precise occupancies of the M1 and M2 metal cation sites in synthetic olivines of compositions (Fe0.3Mn0.7)2SiO4, (Fe0.5Mn0.5)2−SiO4, and (Fe0.7Mn0.3)2SiO4. The distribution coefficient for Fe-Mn exchange in these samples has values of 4.864, 3.976, and 4.078, reflecting the preference of Mn2+ for the M2 site, over Fe2+. These results, and the behaviour of the difference in mean bond lengths of the two sites, indicate that, while showing a tendency towards ordering, the composition-dependence of the solid solution is near ideal.

Keywords

olivinesnetron powder diffractioncation sitesbond length
Type
Research Article
Information
Mineralogical Magazine , Volume 62 , Issue 5 , October 1998 , pp. 607 - 615
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1998

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