Partitioning of Ni between olivine and an iron-rich basalt: Experiments, partition models,and planetary implications

摘要

Trace element mineral-magma partitioning models are important in understanding processes bywhich basaltic magmas are generated. Partitioning models for nickel have been extrapolated from theiroriginal applicability for the Earth's mantle to compositions appropriate for other planets, notably theMoon and Mars. Before partitioning models can be extrapolated to explain nickel concentrations inplanetary rocks, these models need to be verified thermodynamically and experimentally using planetarybasaltic compositions. Experiments conducted in this study on the Martian Gusev Adirondack-classbasalt, Humphrey, with 1 wt% nickel in the magma have shown that Ni affects its liquidus phaserelations. By stabilizing olivine to higher temperatures, Ni increases the liquidus temperature. Theseexperiments have shown that the Hart and Davis (1978) model based on iron-free systems cannotbe extrapolated to planetary, iron-rich, basaltic systems. This work verifies the independence of theJones (1984, 1995) and Beattie et al. (1991) models from temperature and pressure effects and sug-gests extrapolation to planetary compositions is justified but needs further verification. Furthermore,these experiments support the Longhi and Walker (2006) hypothesis that at high temperature nickelmay be incompatible.