In order to understand the crystallization process of global magma ocean, precise knowledge on the element partitioning at various pressures is essentially important. We have determined PC-IR (partition coefficient, ionic radius) diagram for 32 elements between olivine and peridotite melt at 2, 5, 10, and 14 GPa. Two types of starting materials were prepared from a fertile peridotite KLB-1 [1] with different levels of trace elements. High-pressure melting experiments were performed using a piston-cylinder apparatus and a multi-anvil apparatus at the Magma Factory, Tokyo Inst. of Technology. Chemical analyses were performed using EPMA (JEOL-8800) for major and minor elements and LA-ICP-MS for trace elements (ArF excimer laser and a quadrupole mass spectrometer, 30 μm laser beam, NIST610 glass standard). Partition coefficients were calculated and were plotted on the PC-IR diagram. The results of this study are in general agreement with previous studies on similar compositions (analysis by EPMA [2]; by SIMS [3]) except that the shape of the peaks and pattern of the parabolas were tightly constrained in the present study. PC-IR diagram for trivalent cations between olivine and peridotite melt was tightly constrained for the first time with 14 elements (including 8 REE). The partition coefficient for Al increases with pressure (DAl= 0.012 at 2 GPa, 0.048 at 14 GPa) while that for all other trivalent cations decreases with increasing pressure (e.g., DY=0.0077 at 2 GPa, 0.0019 at 14 GPa). The pressure effect on the PC-IR diagram cannot be explained simply by the lattice strain model [4] but requires some additional factors. Increase in DAl may be explained by the combination of two types of substitutions (Mg, Mg) ↔ (Na, Al) and (Si, Mg) ↔ (Al, Al). Decrease in D values for other trivalent cations implies that the latter type of substitution is the dominant mechanism.
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