Melt loss and metamorphism is a mechanism to concentrate magnetite and hematite in the residual rock package.
The specific degree of enrichment is controlled by the melt fertility of the rock.
The concentration of Fe-oxides may increase by > 35 % in fertile, muscovite-rich horizons as a result of melt loss.
Upgrading of these sub-economic horizons adds to the overall grade of the ore system.