Mass-independent fractionation of sulfur isotopes in archean sediments: Strong evidence for an anoxic archean atmosphere

A. A. Pavlov, J. F. Kasting

Research output: Contribution to journalArticle

555 Citations (Scopus)

Abstract

Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (>2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO 2 photolysis. We have used a one-dimensional photochemical model to investigate how the isotopic fractionation produced during SO 2 photolysis would have been transferred to other gaseous and particulate sulfur-bearing species in both low-O 2 and high-O 2 atmospheres. We show that in atmospheres with O 2 concentrations <10 -5 times the present atmospheric level (PAL), sulfur would have been removed from the atmosphere in a variety of different oxidation states, each of which would have had its own distinct isotopic signature. By contrast, in atmospheres with O 2 concentrations ≥10 -5 PAL, all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediments, so any signature of MIF would have been lost. We conclude that the atmospheric O 2 concentration must have been <10 -5 PAL prior to 2.3 Ga.

Original languageEnglish (US)
Pages (from-to)27-41
Number of pages15
JournalAstrobiology
Volume2
Issue number1
DOIs
StatePublished - Mar 1 2002

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Sulfur Isotopes
sulfur isotopes
sulfur isotope
Atmosphere
fractionation
Archean
isotopes
sulfur
sediments
Sulfur
atmospheres
atmosphere
Photolysis
photolysis
sediment
signatures
isotopic fractionation
photochemical reactions
isotope fractionation
Sulfates

All Science Journal Classification (ASJC) codes

  • Agricultural and Biological Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

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abstract = "Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (>2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO 2 photolysis. We have used a one-dimensional photochemical model to investigate how the isotopic fractionation produced during SO 2 photolysis would have been transferred to other gaseous and particulate sulfur-bearing species in both low-O 2 and high-O 2 atmospheres. We show that in atmospheres with O 2 concentrations <10 -5 times the present atmospheric level (PAL), sulfur would have been removed from the atmosphere in a variety of different oxidation states, each of which would have had its own distinct isotopic signature. By contrast, in atmospheres with O 2 concentrations ≥10 -5 PAL, all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediments, so any signature of MIF would have been lost. We conclude that the atmospheric O 2 concentration must have been <10 -5 PAL prior to 2.3 Ga.",
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Mass-independent fractionation of sulfur isotopes in archean sediments : Strong evidence for an anoxic archean atmosphere. / Pavlov, A. A.; Kasting, J. F.

In: Astrobiology, Vol. 2, No. 1, 01.03.2002, p. 27-41.

Research output: Contribution to journalArticle

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AB - Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (>2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO 2 photolysis. We have used a one-dimensional photochemical model to investigate how the isotopic fractionation produced during SO 2 photolysis would have been transferred to other gaseous and particulate sulfur-bearing species in both low-O 2 and high-O 2 atmospheres. We show that in atmospheres with O 2 concentrations <10 -5 times the present atmospheric level (PAL), sulfur would have been removed from the atmosphere in a variety of different oxidation states, each of which would have had its own distinct isotopic signature. By contrast, in atmospheres with O 2 concentrations ≥10 -5 PAL, all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediments, so any signature of MIF would have been lost. We conclude that the atmospheric O 2 concentration must have been <10 -5 PAL prior to 2.3 Ga.

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