EXPERIMENTAL NON-TRADITIONAL STABLE ISOTOPE FRACTIONATION AT HIGH PRESSURE AND TEMPERATURE

There has been enormous progress in the non-traditional stable isotope community in the past 15 years. Natural samples from almost every setting imaginable have been analysed, along with extra-terrestrial samples, biological samples, and experiments. An ever-increasing database has emerged. However, what is missing is a more systematic understanding of how and why these seen fractionations are formed. Experiments are key to understanding the mechansims behind the fractionations seen in nature and calculated in models. While the experiments are technically challenging as equilibrium and kinetic processes are hard to disentangle in such small samples, an enormous amount has been learned in the past few years. To date, experiments have been conducted to probe the Fe, Si, Mo, Mg, S, Ni, C, V and Ag isotope systems. While some of the results are contradictory, it is clear that stable isotopes can and do fractionate at high pressure and temperature and that experiments are central to figuring out why.

In this study, we aim to study the mechanisms responsible for Fe, Si and S stable isotope fractionation at high pressure and temperature in order to understand more about the formation of the Earth and its differentiation. The motivation for this work is two-fold. Fundamentally, it is important to understand what mechanisms are responsible for the isotope fractionations found in nature. On the other hand, we will also be able to start to systematically independently determine the identity of the light elements in the core and the physical conditions and mechanisms of Earth’s differentiation. We will show that pressure, temperature, composition and oxygen fugactiy all have an influence on the partitioning of isotopes and that determining the way all the variables interact is key to understanding the measured ratios in natural samples.