The redox conditions prevailing during the formation of vanadiferous titanomagnetites from three layered intrusions (Bushveld; Koillismaa; Skaergaard) have been estimated from the valence state of vanadium using synchrotron X-ray absorption near edge structure spectroscopy (XANES). Using a high energy-resolution X-ray emission spectrometer, we show that vanadium occurs mostly as V 3+ , with minor V 4+ . The most concentrated samples (up to 2.4 wt% V 2 O 3 ) contain approximately 10% of vanadium as V 4+ . Both V 3+ and V 4+ occur in the octahedral site of the spinel structure. Considering the low magnetite/melt V 4+ partition coefficients, this suggests that vanadium ores crystallized under specific oxidizing conditions.
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Etienne Balan (2006) studied this question.
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