Fig. 5: Mixing correlations between paleo-atmospheric gases and crustal/ hydrothermal gases contained in fluid inclusions of Archean (3.5–3 Ga) hydrothermal quartz from various geological settings.

Note the logarithmic scale on the y-axis. The atmospheric endmember has an estimated ⁴⁰Ar/³⁶Ar ratio of 140 ± 30⁵⁷ (Fig. 2). Uncertainties are shown at 1 sigma. Two points from Marty et al.⁷⁶ plot outside of the displayed abscise range and are therefore given in parenthesis. These data suggest that the partial pressure of nitrogen (pN₂) in the ancient (including Archean) atmosphere was arguably not 2–3 times greater than present-day.