Rock on, and on and on
The rock's chemical composition resembles that of volcanic rocks
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Friday, 26, Sep 2008 10:04
Canadian bedrock may be the oldest known section of the Earth's crust, scientists have claimed.
Researchers at the Carnegie Institution used geochemical techniques to date the bedrock at 4.28 billion years old, making it 250 million years older than any other discovered rock.
An expanse of bedrock exposed on the eastern shore of Hudson Bay, in northern Quebec, known as the Nuvvuagittuq greenstone belt, was first recognised as potential site for ancient rocks in 2001.
A study published in the journal Science today measured variations in the isotopic composition of the rare elements neodymium and samarium in the rocks and aged the rock samples between 3.8 to 4.28 billion years old.
"There have been older dates from Western Australia for isolated resistant mineral grains called zircons, but these are the oldest whole rocks found so far," Richard Carlson, from the Carnegie Institution said.
The Earth is 4.6 billion years old and remnants of its early crust are extremely rare - most of it has been destroyed by plate tectonics since the planet's formation.
Scientists believe the rocks are significant, not only because of their age, but also due to their chemical composition, which resembles that of volcanic rocks in geologic settings where tectonic plates are crashing together.
"This gives us an unprecedented glimpse of the processes that formed the early crust," Mr Carlson added.