A Pre-Edge Analysis of Mn K-edge XANES Spectra to determine Speciation of Manganese in Minerals and Glasses

International audienceHigh-resolution manganese K-edge XANES spectra were collected on a set of 40 Mn-bearing minerals. The pre-edge feature information (position, area) was investigated to extract as much as possible quantitative valence and symmetry information for manganese in various "test" and "unknown" minerals and glasses. The samples present a range of manganese symmetry environments (tetrahedral, square planar, octahedral and cubic) and valences (II to VII). The extraction of the pre-edge information is based on a previous multiple scattering and multiplet calculations for model compounds. Using the method described in this study, a robust estimation of the manganese valence could be obtained from the pre-edge region at 5% accuracy level. This method applied to twenty "test" compounds (such as hausmannite and rancieite) and to fifteen "unknown" compounds (such as axinite and birnessite) provides a quantitative estimate of the average valence of manganese in complex minerals and silicate glasses