Bordage A. auteur aut IRD Balan Etienne auteur aut IRD de Villiers J. P. R. auteur aut IRD Cromarty R. auteur aut IRD Juhin A. auteur aut IRD Carvallo C. auteur aut IRD Calas G. auteur aut IRD Raju P. V. S. auteur aut IRD Glatzel P. auteur aut IRD text journalArticle eng text/pdf born digital access The oxidation state of vanadium in natural and synthetic Fe-Ti oxides is determined using high-energy resolution fluorescence-detected X-ray absorption spectroscopy (HERFD-XAS). Eleven natural magnetite-bearing samples from a borehole of the Main Magnetite Layer of the Bushveld Complex (South Africa), five synthetic Fe oxide samples, and three natural hematite-bearing samples from Dharwar supergroup (India) are investigated. V K edge spectra were recorded on the ID26 beamline at the European Synchrotron Radiation Facility (Grenoble, France), and the pre-edge features were used to determine the local environment and oxidation state of vanadium. In the case of the magnetite samples (natural and synthetic), we show that vanadium is incorporated in the octahedral site of the spinel structure under two oxidation states: +III and +IV. The variations of the pre-edge area are interpreted as various proportions in V3+ and V4+ (between 9.5 and 16.3% of V4+), V3+ being the main oxidation state. In particular, the variations of the V4+/V3+ ratio along the profile of the Main Magnetite Layer seem to follow the crystallization sequence of the layer. In the case of the hematite samples from India, the pre-edge features indicate that vanadium is substituted to Fe and mainly incorporated as V4+ (between 40 and 72% of V4+). We also demonstrate the potentiality of HERFD-XAS for mineralogical studies, since it can filter out the unwanted fluorescence and give better resolved spectra than conventional XAS. specialized Vanadium Impurity Oxidation state V K edge HERFD-XAS Fe-Ti oxides 064 38 6 449-458 2011 0342-1791 https://www.documentation.ird.fr/hor/fdi:010053495 10.1007/s00269-011-0418-3 0342-1791 [F B010053495] https://www.documentation.ird.fr/hor/fdi:010053495 https://www.documentation.ird.fr/intranet/publi/2011/05/010053495.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2011-05-31 2017-08-23 fdi:010053495 fre