Tuesday, May 27, 2014

Composition & Density of the Archean Atmosphere Based on 3+ Billion Year old Fuild Inclusions in Hydrothermal Quartz

Nitrogen Isotopic Composition and Density of the Archean Atmosphere


Marty et al


Understanding the atmosphere's composition during the Archean eon is a fundamental issue to unravel ancient environmental conditions. We show from the analysis of nitrogen and argon isotopes in fluid inclusions trapped in 3.0-3.5 Ga hydrothermal quartz that the PN2 of the Archean atmosphere was lower than 1.1 bar, possibly as low as 0.5 bar, and had a nitrogen isotopic composition comparable to the present-day one. These results imply that dinitrogen did not play a significant role in the thermal budget of the ancient Earth and that the Archean PCO2 was probably lower than 0.7 bar.

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