Earth Shows Its Age | September 29, 2008 Issue - Vol. 86 Issue 39 | Chemical & Engineering News
Volume 86 Issue 39 | p. 34 | Concentrates
Issue Date: September 29, 2008

Earth Shows Its Age

Department: Science & Technology
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ELDERLY ROCKS
Lanthanide isotope tests indicate these rocks along the eastern shore of Hudson Bay are Earth's oldest, at 4.28 billion years.
Credit: © 2008 SCIENCE
earth
 
ELDERLY ROCKS
Lanthanide isotope tests indicate these rocks along the eastern shore of Hudson Bay are Earth's oldest, at 4.28 billion years.
Credit: © 2008 SCIENCE

Using neodymium-based isotope dating, Jonathan O'Neil of McGill University, in Montreal, and colleagues have identified what could be the oldest rocks ever found on Earth (Science 2008, 321, 1828). The researchers collected the samples from the Nuvvuagittuq greenstone belt, an expanse of exposed bedrock on the eastern shore of Hudson Bay in northern Quebec. The rocks are composed of cummingtonite, plagioclase, biotite, and quartz, and in some cases they also contain garnet. The team measured ratios of 142Nd, 143Nd, and 147Sm to 144Nd in order to date the rock samples. The results indicate that the rocks are 4.28 billion years old, which suggests the formation "may represent the oldest preserved crustal section on Earth," which itself is some 4.6 billion years old, the researchers note. Samples collected at the Acasta gneiss in Canada's Northwest Territories held the former record of 4.03 billion years for whole rocks. However, isolated zircon mineral grains that formed some 4.36 billion years ago have been found in Western Australia.

 
 
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