2013
Structure and density of molten fayalite at high pressure
Geochimica et Cosmochimica Acta
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- Volume
- 118
- Number
- First page
- 118
- Last page
- 128
- Language
- Publishing type
- Research paper (scientific journal)
- DOI
- 10.1016/j.gca.2013.05.012
The structure of molten fayalite was studied up to 7.5GPa by means of in situ energy-dispersive X-ray diffraction. The pressure-range studied covers the fayalite-spinel-liquid triple point at 6.2GPa. For pure molten fayalite, Fe-O coordination increases gradually from 4.8(2) at ambient pressure (P) to 7.2(3) at 7.5GPa. Compressibility of the melt is derived from the extrapolation of the structure factor to q=0Å-1, enabling the determination of density as a function of P with an unprecedented P-resolution. This is a promising method to extract the equation of state of non-crystalline materials at moderate P. The link between observed structural changes and density increase and the fact that structural changes occur over a broad but limited P-range in silicate melts implies that the equation of state should not be extrapolated at P-values higher than obtained in measurements, and that a single equation of state cannot accurately describe the density evolution over the whole terrestrial mantle P-temperature (T) range. Fe-rich melts are expected to have a higher densification rate than their Mg counterparts in the 0-10GPa range due to the increase of Fe-O coordination number. As a consequence, Fe-rich melts are more likely to be trapped at depth. © 2013 Elsevier Ltd.
- Link information
- ID information
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- DOI : 10.1016/j.gca.2013.05.012
- ISSN : 0016-7037
- ORCID - Put Code : 34976345
- SCOPUS ID : 84879012185