Document Type




Publication Date



National Academy of Sciences

Source Publication

Proceedings of the National Academy of Sciences

Source ISSN



A hierarchy of isotopically substituted recombination reactions is formulated for production of sulfur allotropes in the anoxic atmosphere of Archean Earth. The corresponding system of kinetics equations is solved analytically to obtain concise expressions for isotopic enrichments, with focus on mass-independent isotope effects due to symmetry, ignoring smaller mass-dependent effects. Proper inclusion of atom-exchange processes is shown to be important. This model predicts significant and equal depletions driven by reaction stoichiometry for all rare isotopes: 33S, 34S, and 36S. Interestingly, the ratio of capital Δ values obtained within this model for 33S and 36S is −1.16, very close to the mass-independent fractionation line of the Archean rock record. This model may finally offer a mechanistic explanation for the striking mass-independent fractionation of sulfur isotopes that took place in the Archean atmosphere of Earth.


Accepted version. "Recombination Reactions as a Possible Mechanism of Mass-Independent Fractionation of Sulfur Isotopes in the Archean Atmosphere of Earth," in Proceedings of the National Academy of Sciences, Vol. 114, No. 12 (2017): 3062-3067. DOI. © 2017 National Academy of Sciences. Used with permission.

babikov_11604acc.docx (108 kB)
ADA Accessible Version

Included in

Chemistry Commons