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Published on: June 13, 2015
Neodymium-142 evidence for Hadean mafic crust
Jonathan O'Neil1, Richard W Carlson, Don Francis
1Earth and Planetary Sciences Department, McGill University, 3450 University Street, Montreal, Quebec, H3A 2A7, Canada. oneil_jo@eps.mcgill.ca
Researchers discovered ancient rocks in Canada with unique neodymium isotope signatures. These findings suggest the rocks formed shortly after Earth's formation, potentially representing the planet's oldest crust.
Area of Science:
- Geochemistry
- Isotope Geology
- Early Earth Studies
Background:
- Neodymium-142 (142Nd) isotope anomalies provide insights into early planetary differentiation.
- The Nuvvuagittuq greenstone belt in Quebec, Canada, is a key site for studying ancient crustal rocks.
Purpose of the Study:
- To investigate the isotopic composition of rocks from the Nuvvuagittuq greenstone belt.
- To determine the age and origin of potentially ancient crustal material.
Main Methods:
- Analysis of neodymium (Nd) and samarium (Sm) isotope ratios (142Nd/144Nd and Sm/Nd) in rock samples.
- Radiometric dating using the 146Sm-142Nd isochron method.
Main Results:
- Some Nuvvuagittuq rocks exhibit lower 142Nd/144Nd ratios than the terrestrial standard (epsilon142Nd = -0.07 to -0.15).
- A positive correlation between 142Nd/144Nd and Sm/Nd ratios was observed within a mafic amphibolite unit.
- A 146Sm-142Nd isochron age of 4,280 ± 53 million years was determined for this unit.
Conclusions:
- The analyzed rocks represent incompatible-element-enriched material formed very early in Earth's history.
- These findings suggest the Nuvvuagittuq greenstone belt may preserve the oldest crustal section on Earth.
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