Experimental determination of partitioning in the Fe‐Ni system for applications to modeling meteoritic metals

Abstract

Experimental trace element partitioning values are often used to model the chemical evolution of metallic phases in meteorites, but limited experimental data were previously available to constrain the partitioning behavior in the basic Fe-Ni system. In this study, we conducted experiments that produced equilibrium solid metal and liquid metal phases in the Fe-Ni system and measured the partition coefficients of 25 elements. The results are in good agreement with values modeled from IVB iron meteorites and with the limited previous experimental data. Additional experiments with low levels of S and P were also conducted, to help constrain the partitioning behaviors of elements as a function of these light elements. The new experimental results were used to derive a set of parameterization values for element solid metal-liquid metal partitioning behavior in the Fe-Ni-S, Fe-Ni-P, and Fe-Ni-C ternary systems at 0.1 MPa. The new parameterizations require that the partitioning behaviors in the light-element-free Fe-Ni system are those determined experimentally by this study, in contrast to previous parameterizations that allowed this value to be determined as a best-fit parameter. These new parameterizations, with self-consistent values for partitioning in the end-member Fe-Ni system, provide a valuable resource for future studies that model the chemical evolution of metallic phases in meteorites.

Siderophile element characteristics of acapulcoite–lodranites and winonaites: Implications for the early differentiation processes of their parent bodies

“…On the basis of the experimental partitioning data (Chabot et al. ), solid metal/liquid metal D values can be empirically calculated for various melting conditions. Chabot et al.…”

“…Chabot et al. () presented an equation to calculate a D value ( D [ E ]) for a trace element E in a system with a light element i :where D 0 is the solid metal–liquid metal partition coefficient in the light‐element‐free Fe‐Ni system, β i is a constant specific to the element E and the light element i , and Fe Domains is defined as the fraction of free Fe atoms available in the liquid metal. Fe Domains is parameterized as follows:where Xi means molar fraction of the light element i in liquid.…”

“…The D 0 and β i values are referred from Chabot et al. (). Partial melting model calculation is performed according to modal batch partial melting.…”

“…The partition coefficient for each element is calculated from the data of Chabot et al. (). [Color figure can be viewed at wileyonlinelibrary.com]…”

“…Solid metal/liquid metal partition coefficient databases were significantly improved and well parameterized (e.g., Jones and Malvin ; Chabot and Jones ; Chabot et al. , ; Corrigan et al. ), and model calculations became applicable to the discussion of metallic partial melting (Rankenburg et al.…”