No liquid immiscibility in the system MgSiO3SiO2 at 5.0 GPa

The purpose of this investigation is to determine the MgSiO3-SiO2 eutectic and extent of the two-liquid field in this system at 5.0 GPa. The liquidus phase relationships were determined using a multianvil apparatus. When compared to phase relationships at 1 atm, the MgSiO3-SiO2 phase diagram at 5.0 GPa is significantly different in a few respects. These differences are examined. It is shown that although the temperature of the solvus critical point is likely to increase with pressure, the dT/dP slope of the SiO2 liquidus is much steeper. As a result, the immiscibility dome has become submerged completely. The reduction in liquid immiscibility in this system at 5.0 GPa implies that in more complex systems relevant to cooling of an initially molten Earth, immiscibility will also be suppressed at high pressures. (AIAA)