Influence of metasomatism on vanadium-based redox proxies for mantle peridotite

The multi-valence nature of vanadium means that its geochemical behaviour will be ƒO 2 -dependent, so that its concentration or V/Sc (or V/Ga), can serve as proxies for oxidation state in mantle peridotites.Compared to Fe 3+ /Fe 2+ -based equilibria, such trace elements may be less sensitive to metasomatic processes.To investigate these systematics, we have measured V, Sc, Ga and Fe 3+ contents in clinopyroxene from well-characterised spinel peridotite xenoliths from the Massif Central, France.These samples were metasomatised by a variety of agents with different oxidation states.V contents can be modified by metasomatic interactions, and other geochemically similar elements including Sc and Ga can also be added, removed or remain constant.A link between V/Sc and Fe 3+ -Fe 2+ equilibria is apparent.Partial removal of V is caused by different metasomatic agents; the common factor is that all agents were significantly more oxidised than the initial ambient mantle peridotite.This extraction can be understood by a decreasing partition coefficient for V for DlogƒO 2 > ~FMQ-2.Considering that mineral/melt partitioning of V decreases similarly for all peridotite minerals, the bulk-rock V/Sc will also change during relatively oxidising metasomatic interactions and mirror the results obtained for clinopyroxene.