hw wl it b dtrmind frm a sampl of ONLY enstatite and silica containing rock if the initial melt had forsterite

Answer 1

Strictly a melt cannot 'contain' forsterite. A melt is a liquid, whereas forsterite is an olivine (i.e. a mineral) - minerals only form when the melt crystallises.

If you want to know if the melt first crystallied forterite (which then reacted with silica in the melt to form enstatite), you could look at the approprate phase diagram, but you would need to know the bulk composition of the rock. Also, the rock itself may contin some sort of textural evidence for the replacement of forsterite by enstatite.