How did the continents appear on Earth? This question, crucial for understanding the emergence of civilizations and life itself, remains one of the great mysteries of the early stages of planetary evolution.
A recent study published in
Science Advances and conducted by scientists from
CNRS-INSU sheds new light on the subject by proposing a very early mechanism for continental crust formation, involving the presence of water through the melting of a serpentinized protocrust.
An international research team (France-USA-Russia), led by scientists from CNRS-INSU, the University of Toulouse, and the University Clermont Auvergne, developed an approach combining experimental petrology, thermodynamic modeling, and geochemistry, which makes it possible
to estimate the mass of continental crust that could have formed through the melting of a serpentinized protocrust. The same process could be
applied to Mars.
Water, the cornerstone of continent formation
Their work shows that
felsic crust (rich in silica) could have formed 4.4 to 4.5 billion years ago through the
melting of serpentinized peridotitesโwater-enriched mantle rocksโin contact with basaltic magmas. This process could explain the Hf isotopic data recorded in zircons dating back to 4.0โ4.4 Ga, the only terrestrial witnesses of the Hadean eon.
ษHf as a function of age for early terrestrial zircons distributed worldwide. Half of today's continents already present in the Hadean
The results indicate that up to
50% of the current mass of continental crust could have been produced by this melting during the Hadean. These findings have significant implications for better understanding the early stages of
mantle-crust differentiation in the Hadean era. This scenario could apply to other water-rich terrestrial planets, such as Mars. It could notably explain the presence of granodioritic rocks on Mars and
estimate the continental mass of the Red Planet.
Diagram of felsic crust and protocrust formation scenarios.
This research was conducted as part of the European project
PLANETAFELSIC and opens
new perspectives on continental crust formation and the conditions favorable for the emergence of life on planets.