Chemical equilibrium between ferropericlase and molten iron to 134 GPa and implications for iron content at the bottom of the mantle

Abstract

We have examined the solubility of oxygen in molten iron coexisting with ferropericlase up to 134 GPa and 3200 K by using laser-heated diamond-anvil cell (LHDAC) and analytical transmission electron microscope (TEM). The results demonstrate that the oxygen solubility in liquid iron decreases with pressure to 38 GPa, whereas the pressure effect is small at higher pressures. If the molten outer core is in chemical equilibrium with the bottom thin layer of the mantle, ferropericlase could be significantly depleted in FeO at the core-mantle boundary (CMB). The liquid core containing 8 wt% oxygen, which is high enough to account for the core density deficit, coexists with ferropericlase with Mg#96 when the temperature is 4000 K. The very bottom of the mantle becomes depleted in iron by the consequences of chemical reaction with the core. Copyright 2008 by the American Gephysical Union.