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The puzzle of 'enigmatic' Sudbury mineral deposits

By: Jonathan Migneault - Sudbury Northern Life

 | Dec 26, 2013 - 10:16 AM |
Graduate students have been busy measuring rocks in the Sudbury basin to find out how the region's offset dykes formed. Supplied photo.

Graduate students have been busy measuring rocks in the Sudbury basin to find out how the region's offset dykes formed. Supplied photo.

Mineral deposits created two billion years ago still poorly understood, says researchers

Around two billion years ago, an asteroid or comet approximately 10 to 15 kilometres in diameter collided with what is now the Sudbury basin.

When it entered Earth's orbit, it was travelling at a speed of around 36,000 km/h. 

The power of the impact when it hit the planet's surface was “off the scale,” according to Gordon Osinski, an associate professor of planetary geology at the University of Western Ontario.

“It's an incredible amount of energy deposited almost instantaneously,” he said.

Geological changes can take millions of years, but that impact altered Sudbury's landscape in a flash.

The heat from the impact was so intense it created a pool of molten rock three kilometres thick.

Geologists have estimated the crater it created – which is no longer visible today – was around 200 kilometres in diameter.

The Chicxulub crater, underneath Mexico's Yucatan Peninsula, is around 180 km in diameter. The asteroid impact that created it 65 million years ago is largely credited for the mass extinction of the dinosaurs.

In Sudbury, the giant pool of molten rock eventually hardened and concentrated the minerals that have made the region one of the most productive mining jurisdictions in the world.

Contrary to popular belief, Sudbury's high nickel concentration was not attached to the meteorite after it collided with the surface. The minerals already existed in the ground, but the extreme heat from the impact fused and concentrated them.

Researchers still do not fully understand how that fusion happened, and how Sudbury's distinct breccia and offset dyke rock-types formed.

Osinksi, who has studied a number of impact sites on Earth and on other planets, has teamed up with Wallbridge Mining Company Limited and the Centre for Excellence in Mining Innovation (CEMI) to figure out exactly how Sudbury's deposits formed.

For Wallbridge, which owns a number of properties in the Sudbury basin, that knowledge could have a direct economic impact.

“We're trying to understand how these structures formed,” said Joshua Bailey, Wallbridge's vice-president of exploration. “And understanding that will help us better explore them for mineral deposits.”

Bailey said the company's land contains about 50 km of offset dykes, which are long fissures of minerals that were concentrated while in a molten state. In the Sudbury basin, they contain platinum group elements, which include platinum and palladium.

They are important components for catalytic converters in vehicles and fuel cells.

“Exploring them, and especially drilling, is very expensive,” Bailey said about the company's offset dykes. “If we can understand how these things formed, we can better prioritize which parts of these dykes are more prospective.”

Osinksi and his team of graduate students have received around $500,000 in funding from Natural Sciences and Engineering Research Council of Canada (NSERC) grants, and their two financial partners, to study the basin's geology.

They were in the field last summer collecting rock samples and making precise measurements. Osinski said they have now reached the stage where they will analyze the data they have collected, along with other rock samples Wallbridge has provided.

A mineral basin he has described as “enigmatic” could be a bit better understood once they compile that data.


Jonathan Migneault

Jonathan Migneault

Staff Writer


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