Magnesium and iron isotopic evidence of inter-mineral diffusion in ultramafic cumulates of the Peridotite Zone, Stillwater Complex

To better understand the role and extent of inter-mineral diffusion during subsolidus processes, we investigated iron magnesium isotopic compositions olivine, orthopyroxene, chromite separates from Peridotite Zone Stillwater Complex. Olivine orthopyroxene show limited Mg variations, with ?26Mg values ranging ?0.40 to ?0.26‰ ?0.29 ?0.22‰, respectively. In contrast, displays extremely large ?0.05 +0.84‰. The ?56Fe olivine range 0.00 +0.17‰ ?0.04 +0.06‰, respectively, whereas those ?0.09 +0.13‰. Most olivine-orthopyroxene pairs in our samples no clear Fe-Mg differences, silicate coexisting plot away theoretically predicted equilibrium lines, indicating disequilibrium fractionation. Higher silicates than significantly higher indicate that re-equilibration is responsible for observed isotope We develop a quantitative model based on reproduce kinetic fractionations. Our results systematic difference between Fe fractionation factors, ?, (?Fe ? 0.27 ?Mg 0.16) (0.03 < ?Fe 0.08 0.05 0.16). This study demonstrates combined investigations cumulus minerals provide more recognizable reliable information among igneous magma chambers elemental analyses alone.