Two QUT researchers used an ordinary laptop computer and a bit of rock from a diamond mine waste pile to resolve a long-standing geological puzzle about diamond formation within the Earth’s historical continents.
Two researchers from Queensland University of Technology (QUT) have utilized a easy laptop computer laptop and a bit of rock, obtained from a diamond mine’s “waste pile”, to unravel a long-standing geological thriller surrounding the formation of diamonds within the deep roots of the earth’s historical continents.
The lead creator, QUT Ph.D. scholar Carl Walsh, together with QUT Professor Balz Kamber and Emma Tomlinson from Trinity College, Ireland, just lately printed their findings within the prestigious journal Nature.
Mr. Walsh stated the examine, for his MSc analysis, concerned laptop modeling on a rock from the African continent recovered from the underside of the lithosphere, the outer a part of the Earth between about 30km and 250km under the floor. Mr. Walsh stated the dominant a part of a continent was the half that you simply by no means see.
“If you think of an iceberg – the visible part – if you just had an iceberg floating on the ocean surface it would tip over like a boat. This is like the keel of an iceberg,” Mr. Walsh stated.
Carl Walsh, proper, QUT Ph.D. researcher and lead creator of a paper printed in Nature with QUT Professor Balz Kamber. Carl is taking a look at a dice of garnet peridotite. The shade of this garnet exhibits the presence of chromium, which is an indicator of the presence of diamond. Credit: Queensland University of Technology
“We basically had a known starting composition of a rock, which is representative of the earth’s mantle at an early time in the history of the earth before all the continents were formed,” Mr. Walsh stated. “We took that starting composition and modeled what would happen to it if it was progressively melted, and what would be left over. And that material is what forms the bulk of the roots of ancient continents that are still around today.”
Professor Kamber, from QUT’s Faculty of Science, School of Earth and Atmospheric Sciences, stated the intention of this analysis was to make use of a pc mannequin to see how these deep roots may need fashioned.
“The model essentially predicts which minerals and melts will be present as you change the temperature of the mantle. So, it’s a predictive tool you can compare with the composition of actual minerals and rocks,” Prof Kamber stated.
The piece of rock used for the superior laptop modeling was mined someday between 1871 and 1914 and ended up within the “waste pile” of the legendary Kimberley diamond mine, finest often known as ‘The Big Hole’ – a mixture open-pit and underground mine – in Kimberley, Northern Cape in South Africa.
Professor Balz Kamber and QUT Ph.D. scholar Carl Walsh. Credit: Queensland University of Technology
The piece of rock they’ve modeled, garnet harzburgite, was dropped at the floor in a kimberlite pipe. The rock was retrieved by Professor Kamber – who makes a speciality of petrology, a department of geology that research rocks and the situations below which they kind.
He rigorously sledgehammered the rock right down to a measurement that he might efficiently ship house.
“It contains a jumble of minerals that were entrained on the way up as they ripped through the base of the whole continent in a supersonic volcanic eruption – the likes of which we have never seen,” Professor Kamber stated. “The minerals in this rock sample are so badly hurt, they are screaming still today, they were absolutely smashed.”
“It is so exciting to see this preserved, it is extremely old – 3.3 billion years old. Probably the oldest rock most people will ever hold in their hands,” Professor Kamber stated.
Mr. Walsh stated the examine solved the conundrum of diamonds and the temperatures through which they fashioned, given a diamond will flip into graphite if heated up an excessive amount of.
“But yet, when we look at the rocks that contain diamonds, they must have been heated to massive temperatures,” Mr. Walsh stated. “So why is it that it is exactly those rocks that experienced the highest temperatures that ended up having diamonds?”
Their analysis challenges the prevailing two-step shallow “melting and stacking” clarification.
“Previously, it was believed that most of the ancient deep roots of continents would have been host to diamonds and that these diamonds were destroyed over time, because the base of the continent is continually invaded and eroded by volatile-rich melts and fluids,” Mr. Walsh stated. “Our work suggests that actually, this might not be the case, that diamonds are rare today – and were in fact always rare. And that’s because we can for the first time know what is missing from the cradle of the diamond and we can go hunt for it at the surface.”
Professor Kamber stated on the present-day earth the warmth and temperature distribution within the mantle isn’t uniform.
“We have areas of relatively uniform mantle temperature and areas where the mantle is a lot hotter. These are known as mantle plumes. And we have expressions of these in Hawaii and Iceland,” Professor Kamber stated. “What we’re studying is the effect of ancient plumes – when much hotter plumes than we have now would have hit the base of a growing continent.”
Since conducting the analysis, Mr. Walsh has traveled to Canberra to recreate comparable rocks within the lab on the Research School of Earth Sciences on the Australian National University.
Reference: “Deep, ultra-hot-melting residues as cradles of mantle diamond” by Carl Walsh, Balz S. Kamber and Emma L. Tomlinson, 15 March 2023, Nature.
DOI: 10.1038/s41586-022-05665-2
