SYNTHESIS OF PYROPE-GROSSULAR GARNETS: AN EXPERIMENTAL STUDY AT P = 2.5 GPA

Abstract

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.