P-V-T measurements of iron suicide (ε-FeSi) Implications for silicate-metal interactions in the early Earth
Guyot, Francois; Zhang, Jianzhong; Martinez, Isabelle; Matas, Jan; Ricard, Yanick; Javoy, Marc
European Journal of Mineralogy Volume 9 Number 2 (1997), p. 277 - 286
published: Jun 26, 1997
manuscript accepted: Oct 30, 1996
manuscript received: May 28, 1996
ArtNo. ESP147050902005, Price: 29.00 €
Abstract We have measured the high-pressure high-temperature equation of state of iron silicide (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, (əK/əT)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.