Diffusion of Ga, Mo, and W in Vestan Melts: Implications for Kinetic Control on Element Partitioning During Vestan Core Differentiation

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Yifan Li, Li Zhang, Huaiwei Ni

Journal of Geophysical Research: Planets, First Published: 22 January 2026

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“Key Points:

  • Diffusivities of Ga, Mo and W in vestan melts are similar and are significantly higher than those in rhyolitic melts
  • During core formation in Vesta, Ga, Mo and W reach equilibrium, whereas some highly siderophile elements (HSEs) may remain disequilibrium
  • The disequilibrium of HSEs is inferred to have a minor contribution to their wide abundance ranges observed in HED”

“Siderophile elements tend to transfer from the magma ocean to the metallic core during core formation in Vesta, but kinetic barriers may prevent equilibrium partitioning. To evaluate the kinetic effect requires knowledge of siderophile element diffusivity in silicate melts, which has yet to be experimentally determined in vestan melts. We have performed diffusion experiments for Ga, Mo and W at 0.5–1 GPa and 1,573–1,873 K in synthesized eucritic and diogenitic melts. The diffusivities of Ga, Mo and W in two vestan melts with distinct melt depolymerization are found to be similar and are 2–3 orders of magnitude higher than those in rhyolitic melts. The modeling results reveal that Ga, Mo and W are enriched into the core to the extent that equilibrium partitioning allows, whereas some highly siderophile elements (HSEs) may maintain a disequilibrium state. However, this disequilibrium does not dramatically affect HSE abundances. The significant variability in HSE abundances in Vesta is mostly due to the brecciation effects and contamination from impactors or metals.”

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