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Saturday, May 18, 2024

Pink Diamonds Unearthed from One of Earth’s Oldest Geological Separations

The Barbiecore trend is taken to a whole new level with pink diamonds, however this trend is not without its drawbacks. These stones are very uncommon and fetch astronomical prices on the gem market. They also have several flaws.

The extreme pressure used to shape the crystal lattice of the gem produces the hue. Diamonds are formed under pressure, but more pressure is required to impart colour to transparent diamonds. If you give a diamond an extra gentle squeeze, it becomes pink; give it a firm squash, and it turns brown.

Until it closed in November 2020, the Argyle mine in Western Australia was one of the world’s most prolific diamond mines, accounting for more than 90 percent of all pink stones ever discovered. Diamonds from Argyle often have a tawny or brownish colour. However, there would be a handful of pink diamonds out of every thousand.

Dr. Olierook and his team have developed a novel theory to explain how and when these precious stones made their way to Earth. On Tuesday, researchers discovered that the stones were driven through the thin continental boundaries during the death of Nuna, one of Earth’s oldest supercontinents, approximately 1.3 billion years ago. In the event that the findings are verified, it raises the intriguing potential that further colourful jewels are concealed in the old continental junctures.

The Argyle diamonds were created deep inside the earth, close to the solid continental base. Collisions on Australia’s northern border gave the necessary pressure to colour the previously colourless jewels when they crashed together to form Nuna.

Argyle’s diamond-studded volcanic rocks erupted some 1.2 billion years ago, according to research conducted in the late 1980s by a team headed by Robert Pidgeon, now an emeritus professor at Curtin. It seems unlikely that a major tectonic event occurred at that time that would have resulted in an explosive eruption that would have brought Argyle’s diamonds to the surface.

However, Dr. Pidgeon has always had doubts about his own conclusions. The rocks may have been affected by the eruption that produced Argyle’s diamond haul because they were formerly part of an old lake. He raised the issue in passing with Denis Fougerouse, another author of the paper from Curtin University, and Fougerouse quickly gathered a team to investigate.

Using a laser beam thinner than a human hair, the researchers recalculated the age of the Argyle rocks. Based on their findings, the eruption probably occurred approximately 1.3 b.y.a., or about 100 m.y. before Dr. Pidgeon’s estimate.

Dr. Olierook said that the new date corresponds to when Nuna first started to shatter, becoming thinner along geologic sutures where prior continents had clashed. Near the present-day northernmost tip of Australia, this thinned area is where diamond-studded magma most likely erupted.

While it’s not groundbreaking to make the connection between continental rifting and diamond resources, the specifics are still up for discussion. Recent computer simulations have shown that the breakup of supercontinents may set off roiling currents in the Earth’s mantle, leading to the eruption of diamond-rich lava flows.

Most diamond-rich eruptions probably tear through dense continental interiors because these currents bounce onshore over time. However, the Argyle diamonds may stand for an earlier stage of this process, before the eruptions spread inland.

Thomas Gernon, a geologist from the University of Southampton in England, who has researched how diamonds are sculpted by supercontinent splits, praised the new work as a significant step towards understanding the “perfect storm of conditions” that helped generate Argyle’s colourful stones.

There are still open issues. Steve Shirey, an isotope geochemist at Carnegie Science in Washington, D.C., who was not involved in the work, said, “This is the last part of the story.” For instance, he has doubts about the initial accumulation of carbon that resulted in Argyle’s legendary diamond wealth.

University of Melbourne geochemist David Phillips notes that the revised age range for Argyle might be further constrained. It’s possible that the study’s findings are accurate, but whether or not they are is still up for debate in his mind.

A Boyle
A Boyle
I cover Science related topics for The National Era
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