Publication Date:
2019-01-11
Description:
Sulfur Mass-Independent Fractionation (S-MIF) may provide a clue to understanding Earth's early atmosphere. We examined total pressure dependence of the S-MIF produced by SO 2 photolysis. Isotopic self-shielding is known to produce S-MIF, which could be changed by both the partial pressure of SO 2 (pSO 2 ) and by the total pressure (pTotal). Our experimental results show that both Δ 33 S and Δ 36 S values are constant when total pressure is below 10 kPa at constant pSO 2 , whereas they decrease as total pressure increases. The result suggests that pressure broadening of the SO 2 absorption line is responsible for the S-MIF. The modeled high-resolution isotopologue cross sections can reproduce our experimental results and its changes depending on both pSO 2 and pTotal. Consequently, we conclude that the Archean Δ 33 S and Δ 36 S correlation can only be achieved when the total pressure of the Archean atmosphere was below 100 kPa, or it was produced in the upper atmosphere. ©2018. American Geophysical Union. All Rights Reserved.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
