High-pressure melting of MgO from (Mg,Fe)O solid solutions

Abstract

Magnesium oxide (MgO) is a significant component of planetary interiors, particularly Earth's mantle and other rocky planets within and beyond our solar system; thus its high-pressure, high-temperature behavior is important to understanding the thermochemical evolution of planets. Laser-heated diamond-anvil cell (DAC) experiments on (Mg,Fe)O ferropericlase up to ~40 GPa show that previous DAC experiments on MgO melting are too low, while previous multi-anvil experiments yield melting temperatures too high. Instead, our quasi-static experimental results are consistent with recent ab initio predictions as well as dynamic shock measurements. Extrapolated to the core-mantle boundary (CMB) of the Earth, MgO is expected to melt at ~8000 ± 500 K, much greater than expected geotherm temperatures.