ISOTOPIC FRACTIONATION DUE TO MULTI-STAGE PLANETARY CORE FORMATION

Observed chemical and isotopic heterogeneity between Solar System bodies implies that these bodies are sourced from different building blocks or were fractionated by formation processes or both. Metal-silicate equilibration during core formation is frequently proposed as a mechanism that may drive observed isotopic heterogeneities, particularly for Fe and other siderophile elements that segregate to the core of a growing planet (e.g., Poitrasson et al., 2004; Shahar et al., 2016; Ni et al., 2022). However, experimental data of isotopic fractionation at core formation conditions is limited, and existing literature relies on models that use oversimplified single-stage core formation models for interpretation. For computational convenience, single-stage models assert that the entire mantle and core of a planet chemically equilibrate with each other--this is geophysically unlikely but becomes physically impossible at the mid-mantle pressures and temperatures that are often required to match the geochemistry of the mantle (Righter, 2003; Rubie et al., 2003). Instead, we use a model based on Rubie et al. (2011, 2015) that combines astrophysical N-body simulations of Solar System formation and a mass-balanced approach to tracking both the elemental and isotopic composition during multiple stages of core-mantle differentiation and re-equilibration. Here, we present modeling results of the effects of multi-stage core formation and planetary accretion histories on notable stable and radiogenic isotopic systems during the formation of the Earth.