Abstract The chemical and mineralogical conversion of pyrite to pyrrhotite has been studied in many aspects, but the associated quadruple sulfur isotopic fractionation between these phases has not been investigated previously. In this study, Ruttan pyrite and pyrite from a Neoarchean carbonaceous phyllite drill core were heated to 675 °C, and the released sulfur was reacted with iron metal, forming compact sulfide rims. The products of both desulfidized pyrite and sulfidized iron metal are pyrrhotite, following the equations n(1-x)FeS2 = nFe1-xS + (1-2x)Sn and Sn + n(1-x)Fe = nFe1-xS, respectively. The mean δ34S of the Ruttan pyrite experiment products has shifted slightly with the residue becoming slightly heavier and the sulfidized iron becoming slightly lighter than the starting Ruttan pyrite. However, the shift is small (0.5‰ and 1.2‰, respectively), yet the range of δ34S increases in the pyrrhotite products, suggesting that the evaporation of sulfur during pyrite breakdown is not occurring uniformly. A shift in δ34S between the initial Archean pyrite and resultant pyrrhotite products is likely a real difference in composition of the analyzed pyrite and the pyrite extracted for the experiment. The compositions of the pyrrhotite run products are quite close with the difference in Δ33S and Δ36S being within ca. 0.1‰. They keep constant with the starting Ruttan pyrite while differ slightly from the initial Archean pyrite, which is likely due to heterogeneity in the original pyrite. The experiments indicate that the fractionation in Δ33S and Δ36S during pyrite desulfidation, sulfur evaporation transfer and condensation and iron metal sulfidation is negligible. Therefore the preservation of Δ33S and Δ36S between initial pyrite and released sulfur during pyrite desulfidation is demonstrated, establishing Δ33S and Δ36S as effective tools of tracing sulfur sources of Archean gold deposits and opening up pyrrhotite as an appropriate phase for studying Archean S-MIF.

中文翻译：

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黄铁矿脱硫制磁黄铁矿过程中的四重硫同位素分馏

摘要 黄铁矿向磁黄铁矿的化学和矿物转化已在许多方面进行了研究，但这些相之间相关的四重硫同位素分馏以前尚未研究过。在这项研究中，来自新太古代碳质千枚岩钻芯的 Ruttan 黄铁矿和黄铁矿被加热到 675 °C，释放的硫与铁金属反应，形成致密的硫化物边缘。脱硫黄铁矿和硫化铁金属的产物都是磁黄铁矿，分别遵循方程 n(1-x)FeS2 = nFe1-xS + (1-2x)Sn 和 Sn + n(1-x)Fe = nFe1-xS . Ruttan 黄铁矿实验产品的平均 δ34S 略有变化，残留物变得略重，硫化铁变得比起始 Ruttan 黄铁矿略轻。但是，偏移很小（0.5‰和1.2‰，分别），但磁黄铁矿产品中 δ34S 的范围增加，表明黄铁矿分解过程中硫的蒸发不是均匀发生的。初始太古代黄铁矿和所得磁黄铁矿产品之间 δ34S 的变化可能是分析的黄铁矿和为实验提取的黄铁矿组成的真正差异。磁黄铁矿运行产品的组成非常接近，Δ33S 和 Δ36S 的差异在约 2 以内。0.1‰。它们与起始的 Ruttan 黄铁矿保持一致，而与最初的太古代黄铁矿略有不同，这可能是由于原始黄铁矿的异质性所致。实验表明，黄铁矿脱硫、硫蒸发转移和冷凝以及铁金属硫化过程中Δ33S和Δ36S的分馏可以忽略不计。