Researchers at Curtin University have discovered a key element in the formation of pink diamonds by studying the Argyle volcano. In addition to requiring deep carbon and tectonic plate collisions, the stretching of continents as they break off also provides pathways for diamond-bearing magma to emerge.
Curtin University researchers studying diamond-rich rocks at Western Australia's Argyle volcano have discovered a third key element needed to bring precious pink diamonds to the Earth's surface for mining, which could significantly aid the global search for new diamond deposits.
It is known that the formation of diamonds requires carbon deep in the Earth, and for these diamonds to turn pink they must be acted upon by forces from colliding tectonic plates. But this new study has discovered a third element required for pink diamonds to appear on the surface - continents that were "stretched" when they broke apart hundreds of millions of years ago.
Lead researcher Dr Hugo Olyroc, from Curtin University's John de Wright Centre, said the "stretching" of the continents created gaps in the crust through which diamond-laden magma could rise to the surface.
Dr Olluk said: "By using a laser beam smaller than the width of a human hair on rocks provided by Rio Tinto, we found that Argyll is 1.3 billion years old, 100 million years older than previously thought, meaning it was likely formed after the breakup of the ancient supercontinent. Argyll is located where the Kimberley region and other parts of northern Australia crashed together many years ago, an impact that created a damaged area or 'scar' in the land that never fully healed."
"While the continent that later became Australia did not break up, the area where Argyll is stretched was stretched, including along scars, which created gaps in the crust through which magma erupted to the surface, bringing pink diamonds with it. As long as these three elements are present - deep carbon, continental collision, and then stretching - then we think it is possible to find the 'next Argyll', which was once the world's largest source of natural diamonds."
Even with these three ingredients in hand, finding another pink diamond deposit would not be without its challenges, Dr. Olluk said. "Most diamond deposits are found in the middle of ancient continents because their main volcanoes are often exposed to the surface for explorers to discover. Argyle is located at the suture of two ancient continents. These edges are usually covered by sand, so it is possible that similar pink diamond volcanoes remain undiscovered, including in Australia."
Co-author Murray Rayner, chief geologist at Rio Tinto, said the Argyle volcano produces more than 90% of the world's pink diamonds, making it an unparalleled source of these rare and coveted gems.
"Knowing the age of Argyle (1.3 billion years) and the location of the breakup of some of Earth's earliest continents gives us a better understanding of how these diamonds were formed," Rayner said.