The appearance of plate tectonics 2.5 billion years ago, favouring the internal dynamics of the Earth, would have allowed a significant release of oxygen in the atmosphere inducing the development of life on our planet, according to a study published by the journal Geochemical Perspectives.
The Earth’s atmosphere remained anoxic for two billion years after the formation of our planet. Then, its oxygen content increased drastically during a well-identified Great Oxygenation Event. It is generally believed that the release of free oxygen was due to the biosphere itself, in relation with the evolution of life on Earth. An international team of researchers from Laboratoire Magmas et Volcans (Université Clermont-Ferrand, CNRS-IRD-OPGC), Géosciences Montpellier (Université de Montpellier, CNRS), the laboratory Conditions Extrêmes et Matériaux: Haute Température et Irradiation (CNRS), and involving five scientists from the ESRF propose a completely different scenario. Based on the experimental observation of a significant amount of ferric iron in the deep Earth’s mantle, they suggest an ascent toward the Earth’s surface of a primordial oxidised-mantle material, inducing the arrival of oxygen into the atmosphere. The upwelling movements would have been hampered during the Archean eon, which was dominated by floating micro-plates at the Earth’s surface. Then, major mantle mixing started when modern plate tectonics and deep slab subduction were established about 2.5 billion years ago, enabling the release of oxygen to the Earth’s surface.