The Argyle volcano in Western Australia was once so full of rocks rich in rare pink diamonds that it was almost bursting at the seams. Now, scientists have discovered that it’s these seams that explain one of the diamond’s key mysteries.
We already know that carbon must be present for diamonds to form. And scientists have previously worked out that forces from colliding tectonic plates turn colourless diamonds pink.
However, scientists have not been able to work out why these pink diamonds sit on Argyle’s surface – until now. The answer reveals secrets about how our continents formed.
A new study, published in Nature Communications, shows that ancient land ‘stretching’ during the break-up of the world’s first supercontinent, Nuna, opened gaps in the Earth’s crust. These gaps, created 1,300 million years ago, caused pink diamond-rich magma to shoot up and cool at the surface.
Argyle sits in the middle of two land masses which collided to form Australia – before Nuna broke up. “That sort of collision creates a damaged area or ‘scar’ in the land that will never fully heal,” said the lead researcher Dr Hugo Olierook.
When Nuna split apart, the Australian land mass did not break, but stretched – including along this collision line. With the stretch mark reopened, diamonds could escape from under the volcanic mountain.
The researchers behind the study, from Curtin University, Australia, used laser beams thinner than human hair to analyse minerals in rocks from Argyle. They discovered that Argyle is 1.3 billion years old: 100 million years older than previously thought. This placed Argyle at the heart of a key moment in Earth’s history.
Around 90 per cent of the world’s pink diamonds come from the Argyle volcano. It was also once the world’s largest source of natural diamonds, but the mine was decommissioned in 2020.
However, now that scientists know the key ‘ingredients’ that make pink diamonds, a hunt for more pink diamond treasure troves will begin.
“As long as these three ingredients are present – deep carbon, continental collision and then stretching – then we think it will be possible to find the ‘next Argyle’,” said Olierook.
The edges of ancient continents are often covered by sand and soil. This means there may be similar pink-diamond volcanoes around the world that have not yet been discovered.
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