Fig. 5
The critical water content for the neutral buoyancy at 410 km. The shaded region represents an experimental range for the coefficient of iron portioning between the melt and mineral (\( {K}_D=\frac{{\left(\mathrm{FeO}/\mathrm{MgO}\right)}_{\min \kern0em \mathrm{eral}}}{{\left(\mathrm{FeO}/\mathrm{MgO}\right)}_{\mathrm{melt}}} \)). Results may depend also on the concentrations of other components such as K2O and CO2 (Jing and Karato 2012). According an experimental study \( {K}_D=\frac{{\left(\mathrm{FeO}/\mathrm{MgO}\right)}_{\mathrm{olivine}}}{{\left(\mathrm{FeO}/\mathrm{MgO}\right)}_{\mathrm{melt}}} \) is insensitive to temperature (Mibe et al. 2006), but water content in the melt increases with decreasing temperature. This makes melts buoyant at relatively low temperatures