什么是 Mineral–melt partition coefficient; compatible and incompatible elements？

The mineral–melt partition coefficient of an element in a mineral is the ratio of its concentrations in the mineral and in a silicate melt in equilibrium with it, $D = C_{\mathrm{mineral}}/C_{\mathrm{melt}}$. For a rock of several minerals of mass fractions $x_i$, the bulk partition coefficient is $\bar D = C_{\mathrm{rock}}/C_{\mathrm{melt}}$. An element is a compatible element in a rock if $\bar D > 1$, an incompatible element if $\bar D < 1$.