A natural olivine sample from a mantle peridotite .xenolith has been studied by in situ high-temperature powder diffractìon, The structure has been successfully refined from powder data at three temperatures (25,600, and 800 °C) using the Rietveld method. The study shows that the full-profìle technique is well suited for the structure artalysis of high-temperature powder diffraction data. The results indicate that, in this temperature range, tbere is no signifìcant ordering of the Fe,Mg cations in the two crystallographically independent octahedrai sites. This has implications for the thermodynamic modeling of olivine at upper mantle condìtions, The present experiments allowed measurement of the lattice thermal expansion of olivine in the temperature range 25-800 •C, and assessment of the temperature dependence of the isotropic atomic displacement parameters.
High temperature in situ Rietveld study of Fe,Mg partitioning in olivine
ARTIOLI, GILBERTO;
1994
Abstract
A natural olivine sample from a mantle peridotite .xenolith has been studied by in situ high-temperature powder diffractìon, The structure has been successfully refined from powder data at three temperatures (25,600, and 800 °C) using the Rietveld method. The study shows that the full-profìle technique is well suited for the structure artalysis of high-temperature powder diffraction data. The results indicate that, in this temperature range, tbere is no signifìcant ordering of the Fe,Mg cations in the two crystallographically independent octahedrai sites. This has implications for the thermodynamic modeling of olivine at upper mantle condìtions, The present experiments allowed measurement of the lattice thermal expansion of olivine in the temperature range 25-800 •C, and assessment of the temperature dependence of the isotropic atomic displacement parameters.
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