Pressure-induced structural and electronic changes of iron in peridotitic glasses

Data on the electronic state and local environment of Fe as a function of pressure (P) are scarce because of experimental challenges of synthesising relevant compositions for the early Earth. This proposal aims to measure Fe in peridotitic glasses, synthesised under different oxygen fugacity (fO2), using X-ray Absorption spectroscopy up to 150 GPa in a diamond anvil cell. Using high resolution energy scans at the Fe K-edge, we will measure its pre-edge feature (i.e. redox, spin state), as well as the extended region above the edge (i.e. mean bond length). Combined with our recent high pressure Mössbauer spectroscopy, we will identify the different spin states of Fe in peridotitic glasses and establish a calibration for the absolute proportions of Fe2+ and Fe3+ therein, using the XANES method. Hence, we aim to determine the relative stabilities of Fe2+ and Fe3+ as a function of P, and whether the fO2 at the surface of a planet depends upon its mass, affecting the Earth’ evolution.