A multianvil apparatus ha been used to determine th pressure-temperature mel ing curve of forsterite from 9.7 to 16.5 GPa. At 10.1 GPa a singular point occurs that marks the change from congruent melting at lower pressures to incongruent melting (forsterite periclase + liquid) at higher pressures. The melting curve also passes through two invariant points. At one (15.6 GPa, 2310øC), the phases ...
