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The origin and degassing history of the Earth’s atmosphere revealed by Archean xenon

Avice, G. ; Marty, B. ; Burgess, R., Nature Communications

The origin and degassing history of the Earth’s atmosphere revealed by Archean xenon

Avice, G. ; Marty, B. ; Burgess, R.

Nature Communications, 2017

Abstract

Xenon (Xe) is an exceptional tracer for investigating the origin and fate of volatile elements on Earth. The initial isotopic composition of atmospheric Xe remains unknown, as do the mechanisms involved in its depletion and isotopic fractionation compared with other reservoirs in the solar system. Here we present high precision analyses of noble gases trapped in fluid inclusions of Archean quartz (Barberton, South Africa) that reveal the isotopic composition of the paleo-atmosphere at E3.3 Ga. The Archean atmospheric Xe is massdependently fractionated by 12.9±2.4%u°/°°1 (±2s, s.d.) relative to the modern atmosphere. The lower than today 129Xe excess requires a degassing rate of radiogenic Xe from the mantle higher than at present. The primordial Xe component delivered to the Earth’s atmosphere is distinct from Solar or Chondritic Xe but similar to a theoretical component called U-Xe. Comets may have brought this component to the Earth’s atmosphere during the last stages of terrestrial accretion.

Voir en ligne : http://dx.doi.org/DOI:10.1038/ncomm...



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publié mardi 30 mai 2017