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Earth’s rarest diamonds form from primordial carbon in the mantle:
Most diamonds are made of carbon recycled over and over again between Earth’s surface and its crust. But diamonds with the deepest origins — such as the famed Hope Diamond[*] — are made of carbon from a separate source: a newly discovered, ancient reservoir hidden in Earth’s lower mantle, scientists report Sept. 10 in Nature.
Chemical clues within these superdeep diamonds suggest that there’s a previously unknown limit to how deep Earth’s carbon cycle goes. Understanding this part of the carbon cycle — how and where carbon moves in and out of the planet’s interior — can help scientists understand changes to the planet’s climate over eons, the researchers say.
Diamonds form at different depths before making their way to the surface where they are unearthed. “Most of the diamonds people are familiar with are from the upper 250 kilometers of the planet,” says Margo Regier, a geochemist at the University of Alberta in Edmonton. “Superdeep” diamonds are from at least 250 kilometers underground, and “they’re really quite rare,” Regier says. But rarest of all are diamonds that form as far as 700 kilometers down, within the lower mantle.
[...] The chemical makeup of diamonds from deeper than 660 kilometers was markedly different from that of the shallower diamonds. Those “form in a different way, from carbon already stored within the mantle,” Regier says. “The very deepest samples must have been [made of] primordial carbon that never escaped from the planet.”
The finding also suggests a limit to how deeply carbon from the surface can be buried within the planet’s interior. One implication of this, Regier says, is that it calls into question whether subduction was able to bury carbon deeply and for long enough to be a driving force behind the Great Oxidation Event.
[*] Wikipedia entry for the Hope Diamond.
Journal Reference:
M. E. Regier, D. G. Pearson, T. Stachel, et al. The lithospheric-to-lower-mantle carbon cycle recorded in superdeep diamonds, Nature (DOI: 10.1038/s41586-020-2676-z)
(Score: 0, Informative) by Anonymous Coward on Monday September 14 2020, @10:11PM
Nuther nutherguy or guy_ another?
(Score: 0) by Anonymous Coward on Monday September 14 2020, @11:27PM (4 children)
Please no! You've just given the diamond merchants a new excuse to increase prices.
(Score: 2, Informative) by Anonymous Coward on Monday September 14 2020, @11:34PM (1 child)
When you have to punch a mine down 661 km, it's not cheap, you know.
(Score: 0) by Anonymous Coward on Tuesday September 15 2020, @04:38AM
They always manage to find some slaves to make it for 100 dolars
(Score: 2) by Grishnakh on Tuesday September 15 2020, @12:07AM (1 child)
They *should* increase prices. Only a fool would buy a diamond, since they have very little resale value, and can now be manufactured industrially, and accordingly, they're only really popular in America, where they really bought into that "2 months' salary" marketing bullshit campaign from DeBeers and still believe it. There's nothing wrong with parting a fool from his money.
(Score: 0) by Anonymous Coward on Tuesday September 15 2020, @11:46PM
Friend, the buyer and the owner of the diamond are 2 different people.
Don't preach to /me/ about how stupid diamonds are. I am not the one who wants it...