Portrait of Earth's coming of age

An analysis of geochemical data reveals a substantial change in the composition of Earth's magmas about 2.5 billion years ago, just as Earth's atmosphere and climate were also changing drastically. See Letter p.490 A geochemical discontinuity in the Archaean Brenhin Keller and Blaire Schoe...

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Bibliographic Details
Published in:Nature (London) 2012-05, Vol.485 (7399), p.452-453
Main Author: White, William M.
Format: Article
Language:English
Subjects:
704/2151/209
704/2151/598
Cooling
Earth
Geology
Humanities and Social Sciences
multidisciplinary
news-and-views
Photosynthesis
Plate tectonics
Science
Science (multidisciplinary)
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Summary:An analysis of geochemical data reveals a substantial change in the composition of Earth's magmas about 2.5 billion years ago, just as Earth's atmosphere and climate were also changing drastically. See Letter p.490 A geochemical discontinuity in the Archaean Brenhin Keller and Blaire Schoene apply statistical sampling techniques to a geochemical database of about 70,000 samples from continental igneous rocks to produce a record of secular geochemical evolution throughout Earth's history. They find, superimposed on the expected gradual geochemical evolution attributable to secular cooling of Earth, a pervasive geochemical discontinuity approximately 2.5 billion years ago. This discontinuity is indicative of dramatic decreases in mantle melt fraction in basalts and in deep crustal melting/fractionation indicators. The Archaean/Proterozoic geochemical transition revealed by this analysis coincides with sudden atmospheric oxygenation at the end of the Archaean aeon, providing a temporal link between deep Earth geochemistry and the rise of atmospheric oxygen.
ISSN:0028-0836
1476-4687
DOI:10.1038/485452a