Metal-silicate partitioning of cesium: Implications for core formation

The highest D-value for Cs observed in this study is 0.345, which was obtained at nbo/t of 2.7 and a metal phase of pure FeS. This metallic composition has far more S than has been suggested for any credible core-forming metal. We therefore conclude that the depletion of Cs in Earth's mantle is either caused by radically different behavior of Cs at pressures higher than 15 GPa or is not related to core formation. Even so, we have shown that a planet with a sufficient S inventory may incorporate significant amounts of alkali elements into its core.