Curtin University researchers studying diamond-rich rocks from Western Australia\u2019s Argyle volcano have identified the missing third key ingredient needed to bring valuable pink diamonds to the Earth\u2019s surface where they can be mined, which could greatly help in the global hunt for new deposits.<\/p>\n\n\n\n
While it is known that for diamonds to form there needs to be carbon deep in the Earth, and for these diamonds to turn pink they must be subjected to forces from colliding tectonic plates, the new study has found the third ingredient needed for the presence of pink diamonds at surface level, which is continents that were \u2018stretched\u2019 during continental break-up<\/a> hundreds of millions of years ago.<\/p>\n\n\n\n Lead researcher Dr Hugo Olierook, from Curtin\u2019s John de Laeter Centre, said the \u2018stretching\u2019 of landmasses created gaps in the Earth\u2019s crust through which diamond-carrying magma could rise to the surface.<\/p>\n\n\n\n \u201cBy using laser beams smaller than the width of a human hair on rocks supplied by Rio Tinto, we found Argyle to be 1.3 billion years old, which is 100 million years older than previously thought, meaning it would likely have formed as a result of an ancient supercontinent breaking apart,\u201d Dr Olierook said.<\/p>\n\n\n\n \u201cArgyle is located at the point where the Kimberley region and the rest of northern Australia smashed together many years prior, and that sort of collision creates a damaged area or \u2018scar\u2019 in the land that will never fully heal.<\/p>\n\n\n\n \u201cWhile the continent that would become Australia didn\u2019t break up, the area where Argyle is situated was stretched, including along the scar, which created gaps in the Earth\u2019s crust for magma to shoot up through to the surface, bringing with it pink diamonds.<\/p>\n\n\n\n \u201cAs long as these three ingredients are present – deep carbon, continental collision and then stretching – then we think it will be possible to find the \u2018next Argyle\u2019, which was once the world\u2019s largest source of natural diamonds.\u201d<\/p>\n\n\n\n Dr Olierook said even with the knowledge of these three ingredients, finding another trove of pink diamonds will not be without its challenges.<\/p>\n\n\n\n \u201cMost diamond deposits have been found in the middle of ancient continents because their host volcanoes tend to be exposed at the surface for explorers to find,\u201d Dr Olierook said.<\/p>\n\n\n\n \u201cArgyle is at the suture of two of these ancient continents, and these edges are often covered by sand and soil, leaving the possibility that similar pink diamond-bearing volcanoes still sit undiscovered, including in Australia.\u201d<\/p>\n\n\n\n Co-author and principal geologist Murray Rayner, from Rio Tinto, said the Argyle volcano has produced more than 90 percent of the world\u2019s pink diamonds, making it an unparalleled source of these rare and coveted gems<\/p>\n\n\n\n \u201cKnowing the Argyle volcano\u2019s age, at 1.3 billion years old, and situated where some of Earth\u2019s earliest continents fragmented, we have significant further insights into the formation of these diamonds,\u201d Rayner said.<\/p>\n\n\n\n The authors are affiliated with the John de Laeter Centre, the Timescales of Mineral Systems Group and the Earth Dynamics Research Group, which sit within Curtin\u2019s School of Earth and Planetary Sciences. The work was enabled by AuScope<\/a> and the Australian Government via the National Collaborative Research Infrastructure Strategy.<\/p>\n\n\n\n