Equilibrium mass-dependent isotope fractionation of antimony between stibnite and Sb secondary minerals: A first-principles study

Antimony (Sb) isotopes are gaining increasing interest for their potential as geochemical tracers in geological, environmental and archaeological studies. However, little is known about the parameters controlling Sb isotope fractionation, which essential to interpret variations of isotopic signature natural systems. In this study, equilibrium mass-dependent fractionation factors (?-factor) were calculated between different Sb-bearing minerals commonly found mining environments including primary sulphide (stibnite Sb2S3) its oxidation products (valentinite Sb2O3, senarmontite cervantite Sb2O4) synthetic antimony pentoxide Sb2O5. First-principles calculations within Density Functional Theory (DFT) performed with functionals test robustness method. Among studied minerals, stibnite has lowest ?-factor (ln(?) = 0.71 ‰ at 22°C), then ?-factors progressively increase from valentinite 1.64 1.80 2.20 22°C) 3.03 22°C). The that most fractionate be i) change state (Sb ratio Sb(V)-bearing higher than Sb(III)-bearing minerals), ii) first neighbour SbO bonds SbS bonds) iii) distortion atomic polyhedrons. negligible differences obtained showed approach calculation ?-factors, despite mineral lattice Raman frequencies. results study provide a theoretical basis variations. suggest significant enrichment heavy could occur during oxidative dissolution subsequent precipitation Sb(III) Sb(V) oxides environments. More generally, work strongly supports may useful tracer transformation processes nature.