Ancient rock found in Quebec

Jan 23, 2003, vol. 26, no. 2
By Carol Thorbes



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When Pierre Nadeau (left) first saw the numbers pop up on an instrument he used to date rocks last summer he knew that he had made a more precious find than he first thought.

The Simon Fraser University master's student, his thesis supervisor, earth sciences assistant professor Laurent Godin, and their colleagues at the Quebec Ministry of Natural Resources had uncovered potentially the oldest known volcanic rock in the world.

They were mapping the rock content of a vast swath of land in Northern Quebec for the province's ministry of natural resources when they struck geological gold.

“We confirmed that the material is 3.825 billion years old. It was formed from volcanic ash compacting and re-melting several times after coming to the Earth's surface,” says Nadeau, whose thesis involves deciphering the rock's history.

Nadeau and Godin are experts in understanding the tale told by ancient rocks about the Earth's formation and evolution.

They knew the cake-like layering of rock they had found in Porpoise Cove on Hudson Bay was old, but not this old.

“It's very humbling when you make a find like this because it's a wealth of geological information,” says Godin. “The Earth's estimated age is 4.56 billion years. Rocks that have an age spanning the first quarter of the Earth's life are extremely rare. They account for a fraction of a per cent of today's Earth's surface. That makes the confirmation of this rock's age particularly important as it increases the scientific rock record of this period.”

Volcanic rock of this age contains sedimentary material formed by chemical and mechanical reactions between the planet's earliest oceans, atmosphere and lands.

“The layers of hardened volcanic ash and sediment may hold clues as to whether and how the earth's water chemistry has changed. It may also have a story to tell about the migration, amalgamation and separation of continents. For example, we know that some parts of eastern Canada and South America were once part of a super-continent.”

Any findings of bacteria traces in the samples could also help scientists understand the birth and evolution of life.

Scientists who've collected volcanic rock in Greenland want to compare their samples to those from Porpoise Cove.

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