The relative effects of composition and temperature on olivine-liquid Ni partitioning: Statistical deconvolution and implications for petrologic modeling

We have used the results of 300 1-bar experiments on Ni partitioning between olivine and liquid to calibrate a composition- and temperature-dependent equation for DNiOl/melt (wt. ratio). The equation incorporates the simplified thermodynamic formulation proposed by Beattie et al. (1991):lnDNiOl/melt=−0.618×lnXDivmeltXSiO2melt+9250T−4.02,where T is in degrees Kelvin, X is mole fraction, XDivmelt = XMgOmelt + XFeOmelt + XCaOmelt + XMnOmelt + XCoOmelt + XNiOmelt. The average error of prediction for DNiOl/melt is ± 12%. The equation indirectly illustrates the effect of depth (pressure) on olivine Ni contents. It allows more accurate modeling of Ni distribution between olivine and coexisting magma during mantle partial melting and olivine crystallization than temperature-independent empirical equations. Higher Ni contents in primitive olivine phenocrysts (Fo > 90) in OIB compared to those in MORB can be explained by the negative depth effect on DNiOl/melt during mantle partial melting.