SiO2 exsolution in Fe-Si-O ternary system

The Earth’s core is mainly composed of Fe and Ni, alloyed with lighter elements, as highlighted by the seismologically observed density deficit. Among the list of light elements, Si and O are among the most favoured. However a debate around a possible incompatibility between both light elements has recently been raised (Hirose et al. 2017). In fact, combined presence of both elements alloyed with iron is not possible due to the exsolution in the liquid state of SiO2. Conventional Laser-Heating Diamond Anvil Cell (LH-DAC) experiments have several drawbacks for constraining SiO2 exsolution in the liquid state. In particular, above the eutectic temperature, the different phases are migrating due to thermal gradient related to the laser Gaussian shape (Morard et al. 2017). To overcome this experimental issue, we propose to use laser-driven dynamic compression combined with in situ X-ray absorption spectroscopy.