Synthesis of pyrope - grossular garnets: an experimental study at P=2.5 GPa

In order to evaluate the stability of Mg-Ca garnets at P=2.5 GPa / T=800 1500°C, some experiments were performed using both natural and synthetic starting materials. Particular attention was paid to the investigation of the Ca rich side of the pyrope grossular join and the maximum pyrope content in grossular was found to be about 10 mol.%. The addition of Cr to the system only slightly increases the observed pyrope solubility in grossular whereas Na stabilises melilite and merwinite. Clinopyroxene with a composition lying on the diopside Ca Tschermak join appears to be the only stable crystalline phase in the middle part of the pyrope grossular join.