Preliminary Results of Quantifying Oxygen Fugacity in Solar System Materials with X-Ray Absorption Spectroscopy of Pyroxenes

Introduction: Oxygen fugacity (fO2) is of extreme importance in geology in part due to the sensitivity of stable mineral assemblages on oxidation potential. The fO2 of natural systems has long been established from experimental petrology, where controlling oxidation potential of metal-oxide starting material influences the reaction end-products. Thus, the oxidation environment of a system can be bracketed using composition of the stable mineral assemblage in a rock. Specific values of fO2 are typically related to the ratios of Fe and Fe of Fe-bearing components in a system as Fe is the most common multivalent rock-forming element. Magmatic systems on Earth range to highly oxidizing value, while extraterrestrial bodies like the Moon, Mars, and asteroids display different, more reduced, oxidation states (Figure 1). For these more reducing conditions, analytical methods that can evaluate valence states of transition metals other than Fe are needed to provide the best understanding of fO2 in natural systems [1].