Super-deep Diamond Contains Earth's Mineral Never Seen Before
Mar 10 2018 by Michele Stevens
Normally, this type of mineral is found deep in the planet's mantle and the surprise came from seeing it appear so very close to the Earth's surface. This is because it is typically buried around 650 kilometers (400 mi.) deep within the Earth. The discovery - described this week in the journal Nature - suggests Earth's deep mantle is hiding more water than previously thought.
"The diamond lattice doesn't relax much, so the volume of the inclusion remains nearly constant whether it's in the Earth's mantle or in your hand", said Oliver Tschauner, a professor of geoscience at the University of Nevada, Las Vegas. The mine is located on a well known diamond-bearing kimberlite pipe in the Gauteng Province of South Africa.
Cullinan Mine is known as the source of some of the world's largest diamonds. "Based on our findings, there could be as much as zettatons [one zetaton is 1,024 kilograms] of this perovskite in deep Earth", Graham Pearson from the University of Alberta, Canada, who coauthored a paper on the matter, said in a statement Wednesday.
Calcium silicate perovskite is one of the most important minerals comprising Earth's lower mantle. In order for them to study this mineral, they had to chemically create it as they could collect a sample from nature.
The rare Earth mineral embedded in the diamond measures only 0.031 millimeters across. They also state that this diamond was formed at around 700 kilometers inside of the Earth. Usually, diamonds form due to the effect of heat and pressure at depths of 150-200 kilometers, but diamonds formed at much lower depths are occasionally found, providing invaluable clues into our planet's interior. The one containing the CaSiO3likely formed at a depth of around 435 miles, where the pressure is approximately 240,000 times greater than the atmospheric pressure at sea level.
Groundbreaking research by UNLV geoscientist Oliver Tschauner and colleagues found diamonds pushed up from the Earth's interior had traces of unique crystallized water called Ice-VII.
Prevented from crystallizing under high pressure, the water froze as geological activity eventually moved the diamonds to the surface.
This diamond is living proof for scientists that oceanic plates do go through a recycling process in the lower mantle of the Earth.
"[The kimberlites] are blasted toward the Earth's surface, preserving these unique pieces of Earth's mantle", Pearson said.
"The specific composition of the perovskite inclusion in this particular diamond. provides fundamental proof of what happens to the fate of oceanic plates as they descend into the depths of the Earth".
The researchers polished the diamond and conducted spectroscopic analysis to confirm that the mineral inside it is indeed the perovskite.
It is true that the history of the planet Earth has been only recorded partially.