22
May 2003
Earth science: Earth's earliest history
The 35-km-long outcrop at Isua in West Greenland contains some of the oldest rocks on Earth, dated at around 3.8 billion years old. Ultraprecise measurements of the decay product (neodymium-142) of an extinct isotope (samarium-146) in these rocks now provide clear evidence that the Earth's mantle underwent significant chemical differentiation during the first several hundred million years following Earth's accretion some 4,560 million years ago. This work has been made possible now by the precision available with the latest generation of thermal ionization mass spectrometer. The new data are consistent with a mean age of mantle differentiation of about 4,460 million years, probably reflecting differentiation of the Earth's mantle during the final stage of terrestrial accretion.
146Sm–142Nd evidence from Isua
metamorphosed sediments for early differentiation of the Earth's mantle
GUILLAUME CARO, BERNARD BOURDON, JEAN-LOUIS BIRCK & STEPHEN
MOORBATH
Nature 423, 428–432 (2003); doi:10.1038/nature01668
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