How much potassium is in the Earthʹs core? New insights from partitioning experiments

The presence of potassium in the core is a vexing issue in Earth Science that is of fundamental concern to the energy budget of the Earth. New experimental data reported here for partitioning of potassium (K) between peridotitic silicate melt and Fe–Ni–S–C–O molten alloy at 1650–2200 °C and 1.0–7.7 GPa reveal a negligible effect of pressure on K partitioning, at least up to 7.7 GPa. No evidence for a systematic increase of K solubility in the alloy with temperature or pressure and S or C contents in the alloy was found. However, there is a possible increase in the K partition coefficient with increasing O content in the molten alloy. Our results, which are appropriate to model core formation in a shallow magma ocean, suggest it is unlikely to sequester more than a few tens of ppm of K into Earthʹs core during a magma ocean event if oxygen is not a major contributor to the light element budget of the core.