Details

Autor(en) / Beteiligte

• Greber, Nicolas D.
• Dauphas, Nicolas
• Bekker, Andrey
• Ptáček, Matouš P.
• Bindeman, Ilya N.
• Hofmann, Axel

Titel

Titanium isotopic evidence for felsic crust and plate tectonics 3.5 billion years ago

Ist Teil von

• Science (American Association for the Advancement of Science), 2017-09, Vol.357 (6357), p.1271-1274

Ort / Verlag

United States: American Association for the Advancement of Science

Erscheinungsjahr

2017

Quelle

American Association for the Advancement of Science

Beschreibungen/Notizen

• Earth exhibits a dichotomy in elevation and chemical composition between the continents and ocean floor. Reconstructing when this dichotomy arose is important for understanding when plate tectonics started and how the supply of nutrients to the oceans changed through time. We measured the titanium isotopic composition of shales to constrain the chemical composition of the continental crust exposed to weathering and found that shales of all ages have a uniform isotopic composition. This can only be explained if the emerged crust was predominantly felsic (silica-rich) since 3.5 billion years ago, requiring an early initiation of plate tectonics. We also observed a change in the abundance of biologically important nutrients phosphorus and nickel across the Archean-Proterozoic boundary, which might have helped trigger the rise in atmospheric oxygen.