1. Formation and Composition of Earth’s Core Beyond the Current Paradigms
James Badro
Institut de Physique du Globe de Paris

2. A multidisciplinary problem
Core composition: a problem with geophysical signature and constraints
seismology + experiments → light elements in the core
Core formation: a problem with geochemical signature and constraints
geochemistry + experiments → deep magma ocean

3. Light Elements in the Core
Francis Birch (1952)
Pure iron
after Uchida et al. (2001)

4. Siderophile Elements in the Mantle
Ted Ringwood (1966)
after McDonough (2003)

5. Light Elements in the Core
Use ab initio molecular dynamics to calculate the density and bulk sound velocity of molten Fe and Fe-light element binaries at CMB and ICB conditions Fe
Fe0.92Ni0.08 Fe0.84Ni0.16
Fe0.92C0.08 Fe0.84C0.16
Fe0.92O0.08 Fe0.84O0.16
Fe0.92Si0.08 Fe0.84Si0.16
Fe0.92S0.08 Fe0.84S0.16
CMB 135 GPa – 4300 K
ICB 330 GPa – 6300 K
Badro et al. (PNAS, 2014)

6. Mixing Model Combine the binary data using an ideal mixing model
r and V for any composition
Generate 10 million “samples” mapping Fe-Ni-C-O-Si-S space
Calculate r and V at CMB and ICB, for each composition
Propagate errors: 1% on V – 0.15% on r / 0.2% on V – 0.5% on r
Only keep the ones that satisfy seismology at CMB and ICB

7. Bulk Core Composition
Badro et al. (PNAS, 2014)

8. Siderophile Elements in the Mantle
Ted Ringwood (1966)
after McDonough (2003)

9. “Cook and Look” Experiments
55 GPa
3600 K

10. Diamond Anvil Cell Experiments
P = 35 – 74 GPa
T = 3200 – 4800 K
55 GPa
3600 K

11. Metal-Silicate Equilibrium

12. Ni and Co Partitioning at High Pressures
45 GPa
65 GPa
35 GPa
Log K
Siebert et al. (EPSL, 2012)

13. Vanadium and Chromium Partitioning
Siebert et al.
(Science, 2013)

14. Core Formation Models Parameters Composition (redox) Temperature Depth
Wood et al. (Nature, 2005)

15. Core Formation Models
Badro et al. (PNAS 2015)

16. Core Composition
Badro et al. (PNAS 2015)

17. Core Composition
Badro et al. (PNAS 2015)

18. Core Composition Core composition: 2.5–5 % oxygen and 2–3 % silicon
Core formation: hot Magma Ocean more oxidized than Mantle
Badro et al. (PNAS 2015)