High-temperature cation ordering in olivine : an in situ Mossbauer study of synthetic (Mg0.55Fe0.45)(2) SiO4

• High- temperature in situ Mossbauer spectroscopy measurements ( 300 950. C) were done on synthetic olivine of composition ( Mg0.55Fe0.45) 2 SiO4 (= Fa45) in order to study the distribution of Fe2+ over the M1 and M2 octahedral sites. The spectra are fit with two doublets, which are assigned to Fe2+ at the M1 ( smaller splitting) and M2 sites. The Fe2+ site- occupancies at M1 and M2, obtained from the Mossbauer relative areas, suggest that Fe2+ has a slight preference for the M1 site at temperatures below similar to 500. C, with a tendency of disordering around this temperature. At higher temperatures, Fe2+ again prefers to occupy the M1 site, where it shows a considerable order at this site up to 750C. At still higher temperatures, the spectra indicated partial reduction of the Fa- component into metallic iron and the resolution of the doublets was severely deteriorated.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

Mossbauer spectroscopy

Olivine

High-temperature

Cation-ordering

Earth sciences

Geovetenskap

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