Temperature and System Composition Effects on the Partitioning of V between Clinopyroxene and Silicate Melt and its Application

Vanadium (V), a common multivalent element, is present in minerals mainly at valences +2, +3, +4, and +5. Its partitioning behavior between minerals and melts is mainly controlled by oxygen fugacity. In clinopyroxene, V mainly exists as V2+ and V3+, replacing Fe2+, Mg2+, Al3+, and Fe3+ by isomorphism substitution. In recent years, the dependence of vanadium partitioning behavior on oxygen fugacity has often been used to explore the redox state of the mantle. In this study, the distribution behavior of V between clinopyroxene and melt was explored using a piston cylinder device with Ni-NiO and HM (hematite-magnetite) oxygen fugacity buffer to control the oxygen fugacity of the experimental system. The experimental pressure was 0.5 GPa and temperatures were 1000 ℃ and 1100 ℃. In this experiment, the oxygen fugacity was >FMQ, therefore, V mainly existed in the form of V3+ in clinopyroxene. The previous data and the results of this experiment showed that the distribution of V in clinopyroxene is affected by oxygen fugacity, temperature, and system composition. As the oxygen fugacity increases, the valence state of V changes, resulting in a change from compatible to incompatible in clinopyroxene. As the temperature and the distribution coefficient of Al between minerals and melts increase, the partition coefficient of V between clinopyroxene and the melt decreases. The formula logDCpx/MeltV =−4.19(±0.33)+0.94(±0.15)×DAl+5730(±480)/T−0.24(±0.01)×ΔFMQ (n=71, R2=0.92), obtained by multiple linear regression, can be used to estimate the oxygen fugacity of natural samples that contain clinopyroxene. © 2022 Science Press. All rights reserved.