Synthesis of Pyrope Garnet with High Samarium Content at 5 GPa and 1300 °C

Abstract

In natural garnets associated with diamonds, an increased content of "light" rare-earth elements, especially samarium, is often noticed. There are various estimates of the composition of the crystallization medium. Experimental data on the synthesis of Cr-rich garnets containing rare-earth elements are still scarce. The experiments were carried out on a multi-anvil apparatus of the “split-sphere” type (BARS) at a pressure of 5 GPa and a temperature of 1300 °С. The high pressure cell was made of Zr02 and CaO. A tubular graphite element was used as a heater. The measurement error of pressure and temperature was ± 0.2 GPa and ± 25 °С. The starting materials for the experiments were natural serpentine-antigorite, chromium spinel, and corundum. As a result of the experiments, pyrope crystals with a high content of samarium were synthesized in the range of 0.77 to 2.34 wt% Sm2O3. The study demonstrates that the interaction of components in the serpentine-chromite-corundum-Sm system in the presence of fluid leads to crystallization of pyrope garnet with samarium content exceeding the values known for natural garnets associated with diamond.