Partitioning of major elements between garnet-structured minerals and silicate melt at pressure of 3-15 GPa

High-pressure melting experiments on primitive mantle composition material (PM1) and thoreiitic basalt (JB2) were performed from 3 to 15 GPa, and garnet (majorite)/silicate melt partition coefficients, D, were measured for major elements. In the case of PM1, garnet was the liquidus phase only at around 15 GPa, where the partitioning experiments were performed. Although experimental time of PM1 was changed from 10 to 120 min, no obvious change was found in the observed D values of major elements. The liquidus phase of JB2 was garnet under the present experimental conditions. With increase in pressure, an obvious increase in D-Na and decrease in D-Ti were found in JB2, but D values of the other elements showed no significant pressure dependence. The observed D values of PM1 and JB2 were compared in partition coefficient (PC)-ionic radius (IR) diagram. Although the absolute D values were different, D profiles of PM1 and JB2 at 15 GPa resembled each other. (C) 2000 Elsevier Science B.V. All rights reserved.