P-V-T measurements of iron suicide (ε-FeSi) implications for silicate-metal interactions in the early Earth

F. Guyot (1) , J. Zhang , I. Martinez , J. Matas , Y. Ricard (2) , M. Javoy (3)

1 IMPMC - Institut de minéralogie et de physique des milieux condensés
2 LST - Laboratoire de Sciences de la Terre
3 IPGP - Institut de Physique du Globe de Paris

We have measured the high-pressure high-temperature equation of state of iron suicide (ε-FeSi) by synchrotron X-ray diffraction, in-situ in a multi-anvil apparatus. Analysis of the non-hydrostatic stress-free data yielded the following thermoelastic parameters: V0 = 90.39(4) Å3, K0 = 172(3) GPa, (∂K/∂T)P = -0.043(8) GPaK-1, α = 5.1(4) 10-5 K-1 with fixed K′0=4. Discrepancies with previous ultrasonic measurements could be explained by highly anharmonic effects in this compound. These equation-of-state parameters were included in a thermodynamic model of the reaction between Fe and SiO2, showing that the reduction of the silicates by iron presents a maximum at pressures between 8 and 15 GPa, and could be efficient at high temperatures, depending on the values of the activity coefficient of silicon in Fe-Si alloys. Similar reduction reactions in the Earth's complex system would have profound implications for the compositions of mantle and core, as well as for reactions at the core-mantle boundary.

Domaines: Géophysique [physics.geo-ph]

F. Guyot, J. Zhang, I. Martinez, J. Matas, Y. Ricard, et al.. P-V-T measurements of iron suicide (ε-FeSi) implications for silicate-metal interactions in the early Earth. European Journal of Mineralogy, 1997, 9 (2), pp.277-285. ⟨hal-02046753⟩