Surface energy of fayalite and its effect on Fe-Si-O oxygen buffers and the olivine-spinel transition

Journal Article · 01 October 2018 · American Mineralogist

DOI: https://doi.org/10.2138/am-2018-6531 · OSTI ID:1567001

Lilova, Kristina ^[1]; Angelis, Michael ^[2]; Anovitz, Lawrence M.  ^[3]; Navrotsky, Alexandra ^[1]

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1. Univ. of California, Davis, CA (United States). Peter A. Rock Thermochemistry Lab.
2. Univ. of Arkansas at Little Rock, Little Rock, AR (United States). Dept. of Earth Sciences
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

The surface energy (hydrated surfaces) of fayalite ($$α$$-Fe₂SiO₄) was determined to be 2.47 ± 0.25 J/m² using high-temperature oxide melt solution calorimetry. This is larger than the surface energy of magnetite (Fe₃O₄), but lower than that of forsterite ($$α$$-Mg²SiO₄). The changes in the positions of the quartz-fayalite-magnetite (QFM) and quartz-iron-fayalite (QIF) buffers with particle size reduction were calculated. QFM is lowered in $$f_{O_2}$$ by 3–7 log units as a function of temperature for 30 nm particles while QIF is raised by 1–2 log units. The estimated surface energy difference between olivine and spinel polymorphs decreases the pressure of the olivine-spinel transition in Fe₂SiO₄ by about 1 GPa.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1567001
• Journal Information: American Mineralogist, Journal Name: American Mineralogist Journal Issue: 10 Vol. 103; ISSN 0003-004X
• Publisher: Mineralogical Society of AmericaCopyright Statement
• Country of Publication: United States
• Language: English