The effect of liquid composition on the partitioning of Ni between olivine and silicate melt

Abstract

We report the results of experiments designed to separate the effects of temperature and pressure from liquid composition on the partitioning of Ni between olivine and liquid, . Experiments were performed from 1300 to 1600 °C and 1 atm to 3.0 GPa, using mid-ocean ridge basalt (MORB) glass surrounded by powdered olivine in graphite–Pt double capsules at high pressure and powdered MORB in crucibles fabricated from single crystals of San Carlos olivine at one atmosphere. In these experiments, pressure and temperature were varied in such a way that we produced a series of liquids, each with an approximately constant composition (~12, ~15, and ~21 wt% MgO). Previously, we used a similar approach to show that for a liquid with ~18 wt% MgO is a strong function of temperature. Combining the new data presented here with our previous results allows us to separate the effects of temperature from composition. We fit our data based on a Ni–Mg exchange reaction, which yields Each subset of constant composition experiments displays roughly the same temperature dependence of (i.e.,) as previously reported for liquids with ~18 wt% MgO. Fitting new data presented here (15 experiments) in conjunction with our 13 previously published experiments (those with ~18 wt% MgO in the silicate liquid) to the above expression gives = 3641 ± 396 (K) and = − 1.597 ± 0.229. Adding data from the literature yields = 4505 ± 196 (K) and = − 2.075 ± 0.120, a set of coefficients that leads to a predictive equation for applicable to a wide range of melt compositions. We use the results of our work to model the melting of peridotite beneath lithosphere of varying thickness and show that: (1) a positive correlation between NiO in magnesian olivine phenocrysts and lithospheric thickness is expected given a temperature-dependent and (2) the magnitude of the slope for natural samples is consistent with our experimentally determined temperature dependence. Alternative processes to generate the positive correlation between NiO in magnesian olivines and lithospheric thickness, such as the melting of olivine-free pyroxenite, are possible, but they are not required to explain the observed correlation of NiO concentration in initially crystallizing olivine with lithospheric thickness.Electronic supplementary materialThe online version of this article (doi:10.1007/s00410-016-1319-8) contains supplementary material, which is available to authorized users.

Melt Diversity and Magmatic Evolution in the Dali Picrites, Emeishan Large Igneous Province

“…The original Ni contents in the melt inclusions have been modified by postentrapment olivine crystallization and exchange reequilibration, which is a concomitant phenomenon with Fe‐loss (Danyushevsky et al, ; Sobolev et al, ). We use measured Ni contents in the host olivine together with values from Matzen et al () to recover the original Ni contents in the olivine‐hosted melt inclusions.…”

Magmatism in the North Atlantic Igneous Province; mantle temperatures, rifting and geodynamics

“…For any mafic liquid crystallizing at 0 GPa, the Mg/Fe (cationic ratio of Mg 2+ /Fe 2+ ) of the melt will therefore be 0.3±0.03 times that of the Mg/Fe of an olivine phenocryst in equilibrium with that melt. Toplis (2005) provides a thermodynamically robust model for determining KD(Fe-Mg) Ol-melt at pressures that are likely to be encountered during mantle melting, thus allowing temperatures estimates for the generation of primary magmas at depth to be made (Herzberg and O'Hara, 2002;Matzen et al, 2017;Hole, 2018 Fig. 6a and b) named after its creator, J.…”

Signature of deep mantle melting in South Iceland olivine

“…Besides utilizing the major and trace element composition of magmas, the nature of the mantle source can be probed by analyzing forsteritic olivine macrocrysts. The composition of forsteritic olivine reflects the composition of its near-primary parental magma, and hence the mode (Sobolev et al 2005) and/or melting conditions (Li and Ripley 2010;Matzen et al 2013Matzen et al , 2017a in the mantle source. In Iceland, olivine compositions have been found to be rather consistent with shallow melting of lherzolite (Herzberg et al 2016), although some lavas have olivines with higher Ni than expected by models of fractional crystallization of peridotite-derived melts (Shorttle and Maclennan 2011;Herzberg et al 2016;Neave et al 2018).…”