Experimental studies on the viscosity of (Mg,Fe)O melt up to 70 GPa

Abstract:

The viscosity of silicate liquids is crucial to our understanding of the thermochemical evolution of early Earth, e.g., convection within a magma ocean and melt migration. Earth's lower mantle is generally considered to be a mixture of MgO and MgSiO₃, and while the mantle is currently mostly solid, early in Earth’s history, it would have been a molten mixture. Experimental studies, however, are limited to low pressures and low temperatures (i.e., ~20 GPa and < 2000K). First-principles computations have now expanded viscosity estimates in to the P-T range of Earth's lower mantle, but only on the MgSiO₃ end-member. In this study, we determined the viscosity of an (Mg, Fe)O liquid up to 5000 K and pressure up to 70 GPa, using a laser-heated diamond-anvil cell (LHDAC). We will discuss the effect of pressure, temperature and iron on the viscosity of (Mg,Fe)O. These results will help to further constrain the viscosity of a magma ocean at high pressures, thus increasing our understanding of the evolution of early Earth.