Intersite cation partitioning in natural and synthetic alpha-(Fe, Mn)2O3 (bixbyite) solid solutions determined from57Fe Mössbauer spectroscopy
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The partitioning of Fe3+ and Mn3+ between the 8b and 24d crystallographic sites in samples of alpha-(Fe, Mn)2O3 solid solutions was determined from57Fe Mössbauer spectroscopy measurements at 298 K. In the case of synthetically prepared samples, we find that with increasing iron content and temperature of equilibration, Fe3+ preferentially enters the more distorted 24d sites. However, the intersite cation distribution coefficient (KD) is only a function of the temperature of equilibration, and can therefore be used to estimate the temperature of formation of naturally occurring bixbyite. Using this technique, the temperature of formation of bixbyite samples from the Postmasburg manganese field in South Africa was calculated to be between 315 and 370 ‡C. This is in good agreement with values obtained from other techniques, suggesting that it may be possible to use the intersite cation distribution in bixbyite as a geothermometer.
KeywordsIron Spectroscopy Thin Film Manganese Solid Solution
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