Experiments on the element partitioning between olivine and aqueous chloride solution under supercritical conditions

Experiments on the partitioning of Mg²⁺, Ca²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺ and Zn²⁺ between olivine (forsterite and fayalite) and 2N aqueous chloride solutions were performed in the temperature range of 500 to 800°C, 1 kb. The partition coefficient, which is defined as Kpn(Fo)=(X_Me2sio4,/X_Mg2sio4)/(m_MeCl°2aq/m_MgCl°2q) ^or K_PN(Fa)=(X_mesiO4/X_fesiO4)/(m_MeCl°2aq/m_FeCl°2aq), vs. ionic radius (PC-IR) diagrams are drawn based on the experimental results. In the case of forsterite, the PC-IR curve has a local maximum near Ni²⁺ and shows a concave curve in the region of larger ionic size. However Zn²⁺ deviates from such a trend. In the case of fayalite, the PC-IR curve shows a convex curve with a peak near Ni²⁺ except for 500°C. Also in this case, Zn²⁺ deviates from such a trend. The anomaly of Zn²⁺ may be attributable to its tetrahedral site preferency. The K pn value for Ni²⁺ decreases with increasing temperature, whereas those for the other elements except for Ca²⁺ increase. The optimum ionic radius for forsterite and fayalite seem to increase slightly with increasing temperature.