| Abstract: | A dynamical calculation for melt segregation from a deformable matrix is used as a framework for studying chemical fractionation during melting and melt migration. The chemical aspects of the problem are modelled in terms of modal melting and local diffusive equilibrium, allowing for the use of unchanging distribution coefficients. The chemical properties of the melt segregated is a synthetic data set that is used to test how well simple equations for perfect equilibrium partial melt and perfect fractional partial melt recover the actual degree of melting and original source composition. The general conclusion is that either equation does quite well (to within a factor generally less than 2) even when the physical situation is quite different from that required for deriving these simple relations between degree of melting, distribution coefficient and magma composition. In terms of the apparent source composition as inferred from the properties of the segregated melt, the typical result is to find a source enriched in the more incompatible elements, which could easily be misinterpreted as requiring metasomatic alteration. |
