The paths followed for liquids which undergo batch fractional crystallization will be dependant on where the individual batches of crystals are removed from the system and the composition of the residual liquid after removal.
For Composition X if fractionation occurs between X and Z, the removal of the Fo crystals will yield a dunite, leaving a residual liquid of composition Z. If this is the only place where fractionation occurs then the last liquid will end up at P, leaving a solid mixture of En and An.
If crystallization continues from Z to Q, Fo and En will be removed producing a peridotite, which is either olivine-rich or enstatite-rich, depending on which phase is dominant.
By fractionating at Q, the liquid now moves off the boundary curve directly away from En, towards A.From Q to A, En crystallizes and the liquid composition moves away from Q. At A, En and An crystallize together and the liquid moves down the boundary curve towards E, where Si joins En and An, giving a solid which has enstatite anorthite and quartz - a quartz norite.
The bulk composition of the final solid is given by point Q, the position where the last batch of crystals were removed.
The paths followed for liquids which undergo pure fractional crystallization will all end at the eutectic, regardless of the initial liquid composition.
For Composition X the final liquid remaining after pure fractional crystallization will have the composition of the eutectic. The final solid will be a mixture of Si + En + An, in the proportions given by E in the En-Si-An triangle.
