|Title:||Mass–independent isotope effects in Archean (2.5 to 3.8 Ga) sedimentary sulfides determined by ion microprobe analysis|
|Authors:||S.J. Mojzsis, C.D. Coath, J.P. Greenwood, K.D. McKeegan, and T.M. Harrison|
|Publication:||Geochim. Cosmochim. Acta, v. 67, p. 1635‐1658.|
|Publish Date:||May 2003|
We report sulfur isotope anomalies with Δ33S, the deviation from a mass–dependent fractionation line for the three–isotope system (34S/32S vs. 33S/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.