Melting experiments on the enstatite‐pyrope join at 80–152 kbar

Melting temperatures of the assemblage pyroxene + garnet on the enstatite‐pyrope join were experimentally determined at 11 different pressures between 80 and 152 kbar with a split‐sphere anvil apparatus (USSA‐2000). The compositions of pyroxene, garnet, and melt coexisting along the solidus were also determined. Comparison with previous data at lower temperatures revealed a large temperature dependence of the compositions of garnet coexisting with pyroxene. It is proposed that the observed variation in the garnet composition is caused by disorder in garnet. The obtained alumina contents of orthopyroxene coexisting with garnet on the solidus at 80–110 kbar contributed to an improvement of the garnet peridotite thermobarometry. An internally consistent set of thermodynamic parameters was derived, which allows calculation of the temperature‐pressure phase diagram for the enstatite‐pyrope join at 20–260 kbar.