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Building Archean cratons from Hadean mafic crust.
Jonathan O'Neil1, Richard W Carlson2
1Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, Canada. jonathan.oneil@uottawa.ca.
Science (New York, N.Y.)
|March 18, 2017
Summary
Ancient Canadian rocks reveal early Earth processes. Neoarchean felsic crust in Hudson Bay formed from older mafic crust, challenging previous ideas about early crustal survival.
Area of Science:
- Geochemistry
- Early Earth geology
- Isotope geology
Background:
- Earth's surface processes have erased most evidence of the planet's first crust.
- The Hudson Bay terrane in northeastern Canada contains Neoarchean felsic crust, part of the Northeastern Superior Province.
- Understanding early crustal formation is key to deciphering Earth's history.
Purpose of the Study:
- To investigate the origin and evolution of the Neoarchean Hudson Bay terrane.
- To determine the age and source of the Archean crust in this region.
- To reconstruct early Earth crustal processes using isotopic data.
Main Methods:
- Analysis of neodymium-142 (142Nd) and neodymium-143 (143Nd) isotopes.
- Utilizing samarium-146 (146Sm) and samarium-147 (147Sm) isotopic data.
- Geochronological dating of ~2.7-billion-year-old rocks.
Main Results:
- Rocks in the Hudson Bay terrane (~2.7 billion years old) show the youngest variability in 142Nd.
- Combined Sm-Nd isotopic data indicate this Archean crust formed from reworking of crust older than 4.2 billion years.
- This reworking occurred over a 1.5-billion-year interval in early Earth history.
Conclusions:
- Mafic crust on early Earth could survive for over a billion years.
- This ancient mafic crust served as a significant source rock for Archean crustal genesis.
- The findings provide new insights into the formation and evolution of Earth's earliest crust.
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