September 28, 2008

Oldest Rocks On Earth Discovered In Canada

A strip of bedrock located in the eastern area of Canada's Hudson Bay was discovered to have the oldest rocks on Earth, said scientists on Thursday. The rocks were formed about 4.28 billion years ago, shortly after the planet was created. It might even contain evidence of movement by ancient creatures.

If these findings are indeed correct, this would definitely be the first proof of life on Earth. However, co-author of the article, Don Francis, warned that this had not been verified as of yet.

"If that were true, then this would be the oldest evidence of life," Francis said. "But if I were to say that, people would yell and scream and say that there is no hard evidence."

Francis, the geology professor at McGill University in Montreal added: "Nobody has found that signal any place else on the Earth."

"Originally, we thought the rocks were maybe 3.8 billion years old. Now we have pushed the Earth's crust back by hundreds of millions of years. That's why everyone is so excited," he continued.

The area of discovery is located northern Quebec and measurers about 4 square miles. It is mainly made up of basalt, an igneous rock. To date the rocks geochemists tried isotopic dating methods.

David Lambert, the program director in the National Science Foundation (NSF)'s Division of Earth Sciences said, "This research highlights the ways in which new instrumentation [a thermal ionization mass spectrometer, or TIMS] enables the collection of new data--data which lead to major scientific discoveries."

The rocks are widely speculated to be surviving parts of Earth's primordial crust, which was created on the Earth's surface as it cooled after the origin of our solar system, said Jonathan O'Neil of McGill University.

"Maybe it was the original crust, and before that there was no stable crust on the Earth. That's a big question," O'Neil stated.

The rocks are deemed important not only for their age, but also for the composition of the rocks. They resemble volcanic rocks in geologic areas where tectonic plates are extremely active.

"This gives us an unprecedented glimpse of the processes that formed the early crust," said Richard Carlson of the Carnegie Institution of Washington.

The Earth is approximately 4.6 billion years old, and the remains of its early crust are tremendously hard to find. The majority of the crust has been reformed into the Earth's interior many times over by plate tectonic activity.

"Regardless of that, or the exact date of the rocks, the exciting thing is that we've seen a chemical signature that's never been seen before. That alone makes this an exciting discovery," Francis also noted.

Prior to the study, the most ancient whole rocks known were from a 4.03 billion-year-old formation called the Acasta Gneiss, located in Canada's Northwest Territories.

The oldest dates of these rocks were termed "faux amphibolites," which the researchers thought to be formed from ancient volcanic deposits. Scientists estimated that these rocks were about 3.8 to 4.28 billion years old.

"There have been older dates from Western Australia for isolated resistant mineral grains called zircons," said Carlson, "but these are the oldest whole rock dates yet."

These historic discoveries are available in the current issue of the journal Science.


Image 1: Bedrock along the northeast coast of Hudson Bay, Canada, has the oldest rock on Earth. Credit: Jonathan O'Neil

Image 2: Earth's oldest known rock is composed of the mineral amphibole, which contains abundant garnet, seen as large round "spots" in the rock. Credit: Jonathan O'Neil


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