Fig. 2: Evolution of the isotopic composition of atmospheric argon over time.
From: Fluid inclusions: tiny windows into global paleo-environments
The progressive increase of the atmospheric 40Ar/36Ar ratio is attributed to the outgassing of radiogenic 40Ar from both the Earth’s mantle and crust15. The dashed line represents a recent model published by Zhang et al.58 for the evolution of atmospheric argon. Error bars (1 sigma) are contained within the symbols19,21,109,110,111,112,113. For Pujol et al.57, a possible range of values is indicated in orange. The starting composition (40Ar/36Ar~0) is hypothetical and reflects the original contribution of primordial argon (primarily 36Ar) from chondritic bodies. This inference is also supported by the chondritic-like 38Ar/36Ar ratio of the Earth’s atmosphere.
