Records of mantle geodynamics and atmospheric escape in Archean quartz

Early planetary degassing and atmospheric escape are two major, yet unconstrained, processes that shaped early Earth. Modeling predicts that the atmospheric ²⁰Ne/²²Ne ratio is sensitive to solar-Ne mantle degassing over geological time. Until the Great Oxidation Event, atmospheric escape progressively depletes the atmosphere in Xe, leaving an isotopic imprint. However, the quantity of xenon in the ancient atmosphere remains largely unknown. In this study, we analyzed noble gases in Archean hydrothermal quartz fluid inclusions and show that a modern atmospheric ²⁰Ne/²²Ne ratio was almost reached 2.7 Ga ago, implying intense mantle degassing during the first 1.7 billion years of Earth's history, three orders of magnitude higher than today. Furthermore, we determine an Archean atmospheric Xe/Kr ratio, 2.3 times higher than today, consistent with models of Xe depletion over time through atmospheric escape.