Figure 1.

Relationship between the evolution of the solar EUV flux with time and the progressive isotopic fractionation of atmospheric xenon. (a) Evolution of the solar flux with time. Figure and data are from [39]. The wavelength of ionization of Xe atoms corresponds to the range 920–1200 Å. (b) Progressive isotopic fractionation of atmospheric Xe from cosmochemical components [10] to modern atmosphere [31]. Ancient rocks record intermediate isotopic compositions: 3.5 Ga-old barites [35,36]; quartz samples [37,38]; Proterozoic deep fracture fluids [40].