ELEMENT PARTITIONING BETWEEN OLIVINE AND SILICATE MELT UNDER HIGH-PRESSURE

Element partitioning between olivine and silicate melt has been investigated at pressures 1-14 GPa, by using a 6-8 type multi-anvil high pressure apparatus. In order to observe systematics in the partitioning of trivalent ions, Li was added to the starting materials in order to increase the concentration of trivalent ions in olivine. With increasing pressure, it was found that partition coefficients of most of the elements gradually decreased. Trivalent ions generally showed parabolic pattern on partition coefficient - ionic radius diagram. When pyrolite-like material was used as the starting material, partition coefficient of Al, D-Al, gradually increased with increase in pressure while the partition coefficients of the other elements decreased, and the D-Al deviated from the parabolic pattern of other trivalent ions. The deviation of D-Al from the D pattern of the other trivalent ions was also found when olivine was employed as main component of the starting material. This result may be ascribed to the compositional change of coexisting silicate melt with increase in pressure.