Effects of pressure on paltitioning of trace elements between low{a pyroxene and melt Russnr-r-

In order to better understand magma evolution at depth in the Earth, partition coefficients between low-Ca pyroxene and melt have been experimentally determined at 15 and 20 kbar. Results indicate that partitioning of Sc, Yb, and Ca is little afected by pressure but Al partitioning increases significantly. We conclude that the unique dependence of Al partitioning on pressure results from the stabilization ofAl on octahedral sites in pyroxene. In contrast to results of previous studies, we further conclude that, in most cases, lowpressure partition coefftcients (D : concentration in crystal concentration in melt) are applicable to high-pressure problems and that the strong dependence ofD on cation size observed at low pressure persists at high pressure.