The Parameterization of Solid Metal-liquid Metal Partitioning of Siderophile Elements

Motivation: The composition of a metallic liquid can significantly affect the partitioning behavior of elements. For example, some experimental solid metal-liquid metal partition coefficients have been shown to increase by three orders of magnitude with increasing S-content of the metallic liquid [e.g. 1]. Along with S, the presence of other light elements, such as P and C, has also been demonstrated to affect trace element partitioning behavior [e.g. 2]. Understanding the effects of metallic composition on partitioning behavior is important for modeling the crystallization of magmatic iron meteorites and the chemical effects of planetary differentiation. It is thus useful to have a mathematical expression that parameterizes the partition coefficient as a function of the composition of the metal. Here we present a revised parameterization method, which builds on the theory of the current parameterization of Jones and Malvin [3] and which better handles partitioning in multi-lightelement systems. Previous parameterization: Jones and Malvin [3] demonstrated that the partitioning between solid and liquid metal is dominantly influenced by the metallic liquid composition, not the temperature or properties of the solid metal. In the parameterization of Jones and Malvin [3], the metallic liquid is modeled as being composed of domains, the calculation of which depends on the speciation of the light element in the metallic liquid. The Jones and Malvin [3] method has had success at parameterizing element partitioning in the Fe-Ni-S, Fe-Ni-P, Fe-Ni-SP, and Fe-Ni-C systems [3, 4]. The large majority of experimental solid metalliquid metal partitioning data is from the Fe-Ni-S system. In this system, by the Jones and Malvin [3] method, the solid metal-liquid metal partition coefficient (D) is expressed as: