From Science News' A mineral found in a diamond’s flaws contains the source of some of Earth’s heat:
A tiny bit of rock trapped inside a diamond is now opening a brand-new window into what the planet’s lower mantle looks like. Inside the diamond is a newly identified silicate mineral dubbed davemaoite that can only have formed in Earth’s lower mantle, researchers report November 12 in Science. It’s the first time that scientists have managed to definitively prove that this type of lower mantle mineral — previously just predicted from laboratory experiments — actually exists in nature. The team named the mineral for well-known experimental high-pressure geophysicist Ho-kwang (Dave) Mao (SN: 3/16/04)
Scientists had previously estimated that about 5 percent to 7 percent of the lower mantle must be made up of this mineral, Tschauner says. But it’s fiendishly difficult to directly observe such deep-Earth minerals. That’s because minerals that are stable in the intense pressures of the lower mantle — which extends all the way to 2,700 kilometers below Earth’s surface — begin to rearrange their crystal structures as soon as the pressure lets up.
Even the planet’s most common mineral, a lower mantle magnesium iron silicate known as bridgmanite, was largely theoretical until 2014, when it was discovered to have naturally occurred within a meteorite that had slammed into Australia with a force that generated crushing, deep mantle-like pressures in the rock (SN: 11/27/14). To date, bridgmanite is the only other high-pressure silicate mineral confirmed to exist in nature.
Diamonds act like time capsules, locking in the original mineral forms on their journey to the surface. The discovery of davemaoite is not only a confirmation of its existence, but it also reveals the location of some sources of heat deep inside Earth.... By identifying the chemical makeup of davemaoite, researchers can now confirm where those elements reside.
That’s because the Botswana diamond also contained a high-pressure form of ice as well as another high-pressure mineral known as wüstite (SN: 3/8/18). The presence of those inclusions helped narrow down the rough pressures at which the davemaoite might have formed: somewhere between 24 billion pascals and 35 billion pascals, Tschauner says. It’s hard to say exactly what depth that corresponds to, he adds. But the discovery directly links heat generation (the radioactive materials), the water cycle (the ice) and the carbon cycle (represented by the formation of the diamond itself), all in the deep mantle, Tschauner says.
From the article I think that I'm being told that the diamond is preserving enough pressure to keep both the "davemaoite" and " a high-pressure form of ice" and the wüstite stable as well.
Am I understanding this correctly?
Question: When diamonds "migrate" from deep underground to the surface, do they maintain pressure inside when there is no more pressure outside? If so, how?
I would think that as the diamond rises to the surface and the pressure relaxes outside it would relax and expand uniformly and the pressure would relax inside as well. If that's not the case, why not?
The tiny gray blobs of mineral embedded in this slice of clear diamond are the first samples of newly named davemaoite, a calcium silicate perovskite mineral that only forms in the lower mantle. AARON CELESTIAN/NATURAL HISTORY MUSEUM OF LOS ANGELES COUNTY