Mossbauer and ELNES spectroscopy of (Mg,Fe)(Si,Al)O-3 perovskite: a highly oxidised component of the lower mantle

(Mg,Fe)(Si,Al)O-3 perovskite samples with varying Fe and Al concentration were synthesised at high pressure and temperature at varying conditions of oxygen fugacity using a multianvil press, and were characterised using ex situ X-ray diffraction, electron microprobe, Mossbauer spectroscopy and analytical transmission electron microscopy. The Fe3+/Sigma Fe ratio was determined from Mossbauer spectra recorded at 293 and 80 K, and shows a nearly linear dependence of Fe3+/Sigma Fe with Al composition of (Mg,Fe)(Si,Al)O-3 perovskite. The Fe3+/Sigma Fe values were obtained for selected samples of (Mg,Fe)(Si,Al)O-3 perovskite using electron energy-loss near-edge structure (ELNES) spectroscopy, and are in excellent agreement with Mossbauer data, demonstrating that Fe3+/Sigma Fe can be determined with a spatial resolution on the order of nm. Oxygen concentrations were determined by combining bulk chemical data with Fe3+/Sigma Fe data determined by Mossbauer spectroscopy, and show a significant concentration of oxygen vacancies in (Mg,Fe)(Si,Al)O-3 perovskite.