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

锑 (Sb) 同位素因其在地质、环境和考古研究中作为地球化学示踪剂的潜力而受到越来越多的关注。然而，关于控制 Sb 同位素分馏的参数知之甚少，这对于解释自然系统中同位素特征的变化至关重要。在这项研究中，计算了采矿环境中常见的不同含锑矿物之间的平衡质量依赖同位素分馏因子（β-因子），包括原生硫化锑（辉锑矿 Sb ₂ S ₃）及其氧化产物（华铁矿 Sb ₂ O ₃ , 锡钠沸石 Sb ₂ O ₃ , 硅钙石 Sb ₂ O ₄) 和合成五氧化二锑 Sb ₂ O ₅。密度泛函理论 (DFT) 中的第一性原理计算使用不同的泛函进行，以测试该方法的稳健性。在所研究的矿物中，辉锑矿的 β 因子最低（ln(β) = 0.71 ‰ at 22°C），然后 β 因子逐渐增加，从华辉石（ln(β) = 1.64 ‰ at 22°C）到蛇钠锰矿（ln(β) = 1.80 ‰ 在 22°C）、硅藻土（ln(β) = 2.20 ‰ 在 22°C）和五氧化二锑（ln(β) = 3.03 ‰ 在 22°C）。发现大多数分馏 Sb 同位素的因素是 i) Sb 氧化态的变化（含 Sb(V) 矿物中的 Sb 同位素比高于含 Sb(III) 矿物中的 Sb 同位素比），ii) 首先Sb 的邻居（Sb O 键中的 Sb 同位素比高于 SbS 键）和 iii）原子 Sb O 多面体的变形。尽管计算的矿物晶格和拉曼频率存在差异，但使用不同泛函获得的 β 因子差异可忽略不计，这表明计算 β 因子的方法具有鲁棒性。本研究结果为解释天然 Sb 同位素变化提供了理论依据。结果表明，在辉锑矿的氧化溶解和随后的硫化物环境中 Sb(III) 和 Sb(V) 氧化物的沉淀过程中，可能会发生重同位素的显着富集。更一般地说，这项工作强烈支持 Sb 同位素可能是自然界中 Sb 转化过程的有用示踪剂。