Experiments on the simultaneous partitioning of divalent cations between pyrite or pyrrhotite and 2M aqueous chloride solution under supercritical conditions

The experiments on the simultaneous partitioning of divalent cations (Ni²⁺, Mg²⁺, Co²⁺, Zn²⁺, Fe²⁺, and Mn²⁺) between pyrite or pyrrhotite and 2M aqueous chloride solution were conducted under supercritical hydrothermal conditions of 500, 600, 700, and 800 °C, and 1 kb, using standard cold seal type pressure vessels. The experimental results revealed that the cations are preferentially partitioned into pyrite and pyrrhotite in the following orders, respectively: Co²⁺=Ni²⁺=Fe²⁺ > Zn²⁺ > Mg²⁺=Mn²⁺ for pyrite and Co²⁺ > Ni²⁺≥Fe²⁺ > Zn²⁺ > sMg²⁺=Mn²⁺ for pyrrhotite. If we assume that Mg²⁺ shows a partition behavior according to the ionic radius, the partition coefficient vs. ionic radius (PC-IR) curves for both pyrite and pyrrhotite mark a peak at 0.77 Å. Zn²⁺ shows a negative deviation from the PC-IR curves, but Ni²⁺ shows a positive deviation.