Core formation experiments at conditions of a deep magma ocean

Models of core formation involve equilibration of metal and silicate in a deep magma corresponding to pressure and temperature conditions above 50 GPa and 3500 K (e.g. 1, 2). Over the last four decades, core formation experiments have been performed under limited P-T ranges, accessible with large volume presses such as piston cylinder or multi-anvil presses. Therefore, modeling the behaviors of elemental distribution between core and mantle during Earth’s differentiation required thermodynamic extrapolations leading potentially to large errors. However, the last decade has proven the possibility of producing metal-silicate experiments using the Laser Heated Diamond Anvil Cell (LHDAC), the only static pressure device capable of producing the direct P-T conditions of core-mantle equilibration, despite technical hurdles linked to sample recovery, analyses at small spatial scales, and chemical equilibrium. This talk will review recent findings which revealed new processes that were unexpected on the basis of prior experiments or confirmed and precise some existing models. Using the partitioning results of a large number of siderophile elements, the conditions of core formation during accretion, the budget of light elements in the core, and the origin of volatile elements will be discussed.  

(1)   J. Siebert, J. Badro, D. Antonangeli, F.J. Ryerson (2013). Terrestrial accretion under oxidizing conditions. Science, 339, 1194-1197.

(2)   D. Huang, J. Badro, J. Siebert. The niobium and tantalum concentration in Earth’s mantle constrains the initial composition of its primordial magma ocean (2020). Proceedings of the National Academy of Sciences, doi: https://doi.org/10.1073/pnas.2007982117.