Super deep Diamonds
Channel: Diamond Free Shipping Worldwide
Date: 2020-08-10

We can’t dig to the center of the Earth, and we can’t time travel. But if the universe could grant a consolation prize, it would be a super-deep diamond.

These sturdy, rare minerals travel hundreds of miles from Earth’s mantle, where they form, to the crust, where they are discovered. Along the way, they trap history in microscopic flaws.

“Super-deep diamonds are just time capsules, basically,” said Suzette Timmerman, a geochemist at Australian National University. She and her colleagues recently analyzed a set of super-deep diamonds from Brazil and found, preserved within them, helium from Earth’s primordial past.
Their work, published in Science on Thursday, is a further step toward understanding how the planet evolved since its coalescence from bits of rock and gas some 4.54 billion years ago. The finding also adds to the allure of diamonds: They are forever, and they are made entirely of the past.
Earth’s mantle, some 1,800 miles thick, begins about 25 miles down and is sandwiched between the thin outer crust and the dense, iron core. This ancient rock stuffing makes up more than three-quarters of the planet’s volume. But because it is inaccessible, scientists know little about it.
Seismic studies have revealed how a convection current within the mantle allows its contents to circulate. Ocean island basalts — rocks that cooled after volcanic eruptions of magma from the mantle — have offered hints of the mantle’s chemical composition. But neither source has revealed what the mantle is made of at any particular depth.

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That is partly because basalt is a cooled mixture of elements collected during its molten travels. It cannot be parsed. But a diamond does not change physically or chemically on its journey, and whatever it collects can be studied in isolation.

Diamonds form at different depths. As they do so, they trap minerals and fluids that contain carbon, water and noble gasses, capturing snapshots of those environments. These “inclusions” are the flaws that make diamonds cloudy. For earth scientists, they are precious — microscopic parcels of ancient elements from specific times and places, perfectly preserved and protected.
Most diamonds form 100 miles or so below the surface. But in the region of Brazil where Dr. Timmerman worked, more than 99 percent of diamonds are super-deep, having formed in the mantle’s transition zone, between 254 and 410 miles down.

Dr. Timmerman and her team used a high-tech laser and vacuum to release the fluid trapped in the inclusions of super-deep diamonds. Inside they found trace isotopes of helium, in ratios similar to what has been found in ocean island basalts.

Helium is extremely rare on Earth, so its presence in ocean island basalts suggested that a reservoir of helium existed somewhere below ground, although how far down was unclear.