Earth’s Oldest Crust-Like Rocks Produced by Impact?

Hadean-age rocks and minerals are very rare on Earth and provide insights into our planet’s early evolution more than four billion years ago. A new study by Tim Johnson and colleagues at Curtin University, based on phase equilibria and trace element modeling, suggests the Earth’s oldest felsic rocks found in the Acasta Gneiss Province of northwest Canada may have formed as a result of large impacts during the Hadean. These impacts were capable of melting portions of an early basaltic crust.

An impact melt origin for Earth’s oldest known evolved rocks

Gneiss exposed on the Canadian Shield. Hadean rocks of the Acasta Gneiss Complex in northwest Canada, similar in appearance to these ones, possibly formed as a result of large impacts on the early Earth more than 4 billion years ago, according to a new study. Image credit: Martin Schmieder/Lunar and Planetary Institute

Gneiss exposed on the Canadian Shield. Hadean rocks of the Acasta Gneiss Complex in northwest Canada, similar in appearance to these ones, possibly formed as a result of large impacts on the early Earth more than 4 billion years ago, according to a new study. Image credit: Martin Schmieder/Lunar and Planetary Institute

 

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