The abundance of potassium in the Earth’s core

We studied partitioning of potassium (K) between aluminosilicate (adularia, KAlSi3O8) and metals with and without light elements, oxygen and silicon (Fe–O, Fe–Si, and pure Fe metals). We conducted experiments at pressures up to 50 GPa, temperatures up to 3500 K, and oxygen fugacities (log fO2) between 2.5 and 4.0 log units below the iron-wüstite (IW) buffer using a double-sided laser-heated diamond anvil cell. Our results on pressure, temperature, and compositional effects on partition coefficient of potassium, DK (i.e., the content of potassium in metal [wt%] divided by the content of potassium in silicate [wt%]), revealed that the temperature effect is slightly positive but weaker than that reported previously, whereas the pressure effect is negative. Oxygen in metal increases the potassium content in metal, whereas silicon in metal has the opposite effect. According to the present study on potassium partitioning, we estimated that the amount of potassium in the core is less than 40 ppm and that it generates less than 0.17 TW heat in the core. The amount of heat generated in the core is very small compared with the heat escaping from the core at the core–mantle boundary (5–15 TW).