Analysis reveals sulfur isotope anomalies in Archean sedimentary sulfides, suggesting an anoxic atmosphere early in Earth’s history.
We report sulfur isotope anomalies with Δ³³S, the deviation from a mass-dependent fractionation line for the three-isotope system (³⁴S/³²S vs. ³³ S/³²S), ranging up to ±2‰ within individual Archean sedimentary sulfides from a variety of localities. Our measurements, which are made in situ by multicollector secondary ion mass spectrometry, unequivocally corroborate prior bulk measurements of mass-independent fractionations (MIF) in sulfur and provide additional evidence for an anoxic atmosphere on the Earth before ∼2 Ga. This technique also offers new opportunities for exploring ancient sulfur metabolisms preserved in the rock record. The presence of MIF sulfur in sulfides from a >3.8-Ga Fe-rich quartzite from Akilia (island), West Greenland, is consistent with a marine sedimentary origin for this rock.
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Mojzsis et al. (2003) studied this question.
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