Canadian geologists report finding Earth's oldest volcanic rocks

Canadian geologists say they've found Earth's oldest volcanic and sedimentary rocks in northern Quebec. The estimated 3.825-billion-year-old rocks could help scientists to understand the first quarter of the planet's history.

The greyish-white rocks were found in the village of Inukjuak on Purpose Cove on Hudson Bay.

Scientists think during Earth's first billion years, the oceans and moon formed, and the first signs of bacterial life appeared. The planet then quickly separated into its inner core, mantle and crust.

So few rocks have been discovered from this time that every find may offer a wealth of data, said Simon Fraser University Earth Sciences Prof. Laurent Godin.

Godin supervised Pierre Nadeau, a graduate student at SFU, who helped to date the rocks from the Earth's mantle.

He looked at the rate of radioactive decay of uranium in the samples to arrive at the 3.825-billion-year age plus or minus 16 million.

Researchers amazed by age data

Until now, the oldest rocks of this type were thought to be 3.8 billion years old; scientists estimate the Earth is 4.6 billion years old.

Godin said the team was so amazed when the dating results were first revealed that they thought it was a mistake.

"We were expecting 2.8 to 2.9 billion years old," Godin told CBC News Online. "To get 3.825 billion years is like expecting $1 million and winning $1 billion."

To check, dating team leader Jean David of Quebec's Ministry of Natural Resources (MRN) collected more rocks from the four kilometres by 10 kilometres site. They matched.

The oldest rocks of this type were thought to be from western Greenland. Godin said the Quebec rocks offer researchers a chance to test the Greenland find, which was dated using a more indirect method.

UQAM Earth Sciences Prof. Ross Stevenson helped identify where the ancient rocks were likely to be and Martin Parent of MRN was the geologist in the field who lead the five-year mapping project.

The mapping project was funded by the government of Quebec and was presented at an MRN annual meeting.