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BY NILS PETERSON
University of Alberta
Student Contributor
(Geosciences)
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U of A geoscience students find out first-hand what
all the fuss is about as diamond mining in Canada builds momentum.
You won't find many newly married couples in this country
who haven't heard about Canadian diamonds.
One can hardly glance in the direction of a jewelry store
without seeing a giant poster emblazoned with a polar bear
and the frosty tundra, asking you to think patriotically when
you buy your next diamond.
The excitement is justified. In just five years and with only
two producing mines, Canada has rocketed into the top five
of diamond producing nations, and more mines are on the way.
Geologists from Diavik, Canada's second diamond mine, have
provided samples for the research projects of Cristen Krauss
and Hayley McLean, two U of A geology students, who also got
to spend three days at the mine this summer.
At the Earth's surface, pure carbon is stable as graphite,
which is the soft “lead” used in pencils. Diamonds
are chemically identical to graphite, but the intense pressures
and high temperatures deep within the Earth are enough to
turn graphite into these precious gems. This is where they
would remain, were it not for a kind of explosive volcanism
that forms kimberlite pipes at the surface. Kimberlites erupt
from depths of more than 400 kilometres and take mere hours
to reach the surface.
On the way up, these kimberlite magmas trap many materials
— pieces of the mantle and the lower crust.
And, of course, diamonds.
In The Pipe
The pipe being mined at Diavik is about 55 million years old,
and it has been over 30 million years since a kimberlite erupted
on Earth. Kimberlite pipes are carrot-shaped and steep sided,
and can extend several kilometres below the surface.
Canadian pipes are smaller and narrower than others in the
world, at about one or two hectares in surface area, but what
they lack in size they make up for in grade. Canadian kimberlites,
in fact, have the highest diamond grades ever found.
So why did it take so long for the current rush to begin?
The delay in Canada is partially because kimberlites are extremely
difficult to find, especially in the Canadian north where
multiple glaciations have scoured and covered over their traces.
And, despite the value of diamonds, there are very few kimberlites
that have enough of them to mine economically — of the
5,000 kimberlites known in the world, only two dozen have
enough diamonds to warrant production.
Welcome to Nowhere
If there's a nowhere, the Diavik mine is in the middle. It's
300 km from the nearest settlement, and it's only accessible
by air and by ice road in the winter. The treeless landscape
looks alien enough, even without the 24-hour daylight during
the summer.
Cristen and Hayley spent three days at Diavik this summer,
collecting samples for their research projects. “You
definitely know that you're in the wild when you're at the
mine,” said Hayley. “Our room door had a sign
that said, 'Caution: wolverine looking for a friend.'”
The kimberlite pipe currently being mined at Diavik used to
be at the bottom of the nearby lake — a dike had to
be built around it so that it could be mined. “Because
the pit is below lake level, water seeps in and it gets muddy.
You have to have rubber boots on,” said Cristen.
Her project involves rocks from the lower crust, which are
carried to the surface along with diamonds. She hopes to analyze
and date these rocks in order to find out when and under what
conditions the lower crust beneath the area formed.
In Hayley's project, she is collecting round red minerals
called garnets, which are used by field geologists as an indicator
mineral of kimberlites. However, only garnets of certain chemical
compositions indicate kimberlites rich in diamonds.
Hayley hopes to associate garnet colour with composition,
to simplify the way geologists find diamond-rich kimberlite
pipes.
Hayley and Cristen are both enjoying their projects and learned
a lot from their trip to the mine. Other students, too, have
had a taste of the diamond experience — the fourth-year
field school for U of A geology students was at a Diavik exploration
camp this year.
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