Partitioning of Ni between olivine and silicate melt: The ‘Henry's Law problem’ reexamined

The partitioning of Ni between olivine and silicate melt has been investigated experimentally at atmospheric pressure in air. Beta track autoradiography using ⁶³Ni and direct microprobe analysis of polished run products were employed. At constant temperature and bulk composition, the $\text{olivine}\text{liquid}$ partition coefficient for Ni in the system Di₇₀Fo₂₅Qtz₅ remains independent of concentration from approximately 10 ppm to 40,000 ppm Ni in olivine. Similar experiments by Mysen (1979) in the system Jd₈₀Fo₂₀ utilizing beta track autoradiography alone indicated that Henry's Law was followed only in the concentration interval of approx. 10–1000 ppm Ni in olivine. Above 1000 ppm, olivine/liquid partition coefficients decreased monotonically to about half of the value observed below 1000 ppm. We have performed experiments in the system Jd₈₀Fo₂₀, but are unable to replicate Mysen's results. While in agreement with Mysen below 1000 ppm Ni in olivine, we do not observe the decrease in partition coefficient value at higher concentrations. We conclude from our reversed experiments that, at constant temperature and bulk composition, the $\text{olivine}\text{liquid}$ partition coefficient for Ni in the system Jd₈₀Fo₂₀ remains independent of concentration from approx. 10–60,000 ppm Ni in olivine. Attempts to resolve these differing conclusions by changing experimental techniques have been unsuccessful.