Viscosity of Liquid Fayalite up to 9 GPa
Résumé
The viscosity of liquid fayalite (Fe 2 SiO 4) was determined up to 9.2 GPa and 1850 • C using in situ falling sphere viscometry and X-ray radiography imaging. The viscosity of liquid fayalite was found to decrease with pressure, reducing by a factor of 2.5 between ambient pressure and 9.2 GPa. The results are in contrast with previous studies on depolymerised silicate melts which found viscosity to increase with pressure. In accordance with recent in situ structural measurements on liquid fayalite, the viscosity decrease is likely a result of the increase in Fe-O coordination with pressure. In addition, temperature is found to have little effect on the viscosity at high pressure. The results show that liquid silicate viscosities need to be considered on an individual basis and can be strongly dependent on the melt structure and composition. This has important implications for models of planetary differentiation. In particular, terrestrial bodies with high Fe contents and reducing mantle conditions are likely to have had very mobile melts at depth.
Domaines
Sciences de la Terre
Origine : Fichiers produits par l'(les) auteur(s)
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