Abstract

Isotopic signatures have been used to trace genetic links between planetary bodies, to understand the accretional histories of planets as well as the source and origin of planetary building blocks. As the largest chemical mass transfer process occurring on terrestrial planets, core formation is likely to impart a diagnostic imprint on the isotopic and chemical signatures of planetary mantles and crusts. Understanding these isotopic fractionation processes is paramount in order to (1) quantify the physical and chemical conditions under which core formation occurred on planets as well as to (2) fingerprint the effects of core formation relative to other accretion-related processes (e.g. volatilisation processes, heterogeneous accretion, late accretion). However, the role of core formation in establishing the stable isotopic signatures of planetary mantles is still poorly understood. In this work, a new multianvil technique is calibrated to simulate core formation on planets as large as Mars and synthesise sufficient material for isotopic ratio measurements. This method is used to characterise Fe isotopic fractionation between metal and silicate up to 17 GPa, presenting notable variation with pressure. A new series of S-bearing experiments show a different pattern of the Fe isotopic fractionation at high pressure. Thermal gradients are measured in the experimental set up to ensure their minimisation during metal–silicate equilibration in the multianvil press.