5 The Origin of Compositional and Thermal Heterogeneity within Earth’s Interior

Thursday, 4 May 2023
8:00 AM - 12:00 PM
EC 512

ISOTOPIC FRACTIONATION DUE TO MULTI-STAGE PLANETARY CORE FORMATION

Paper number: 5-9
Program: Theme Sessions
Time: 10:20 AM – 10:40 AM

Authors

Abstract

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.

Geological Society of America Abstracts with Programs. Vol. 55, No. 3

doi: 10.1130/abs/2023NC-386921

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