Internally resistive heated diamond anvil cell experiments on Fe-Ni-Si alloy to 200 GPa and 3900 K and its implications for Earth's core
Abstract
Silicon is considered a plausible candidate for the light element in Earth's core, which is a consequence of metal-silicate equilibration during core formation process. Phase relations and equations of state of solid phases in the system Fe-(Fe)Si have extensively been studied by experiment and theory. However, the system Fe-Ni-Si was less studied although the core likely includes 5-10 wt% Ni from cosmochemical observations. We here mapped up the pressure (P)-temperature (T) space in an Fe-Ni-Si alloy as this system is important and relevant to Earth's core.
High-P-T experiments were made in an internally resistive heated diamond anvil cell (DAC) up to 200 GPa and 3900 K with in-situ synchrotron X-ray diffraction. The internally heated DAC heats the sample by its resistance, with an improved accuracy in temperature with respect to conventional laser heated DAC (Komabayashi et al. 2009; 2012; submitted). Results show that a hexagonal close-packed (hcp) structure was observed up to the highest P-T condition studied. We also placed tight constraints on the P-T locations of an important phase relation in the Fe alloys, which is a transition between a face-centred cubic (fcc) and hcp structures. The P-T locations of the boundaries in the Fe-Ni-Si alloy cannot be explained by a simple interpolation of those in Fe (Komabayashi et al., 2009), Fe-Ni (Mao et al., 2005; Komabayashi et al., 2012), and Fe-Si (Tateno et al., 2015; Komabayashi et al., submitted). We will show the experimental data and discuss the location of the triple point of hcp, fcc, and liquid in a compositional range of the system Fe-Ni-Si. Also we will discuss the effect of simultaneous inclusion of Ni and Si on the Fe properties under high P-T condition and propose a new phase diagram for Earth's core.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMMR43B0102K
- Keywords:
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- 3909 Elasticity and anelasticity;
- MINERAL PHYSICSDE: 3919 Equations of state;
- MINERAL PHYSICS