Scientists analyzed superdeep diamonds coming from a stable subterranean reservoir which is estimated to be as old as the moon, hinting that Earth’s mantle and area beneath it could be rich in diamonds.
An international team of scientists measured helium isotopes in diamonds that came to the surface through volcanic eruptions. The analysis revealed that there are traces of an ancient reservoir of primordial rock and diamonds. The project will be presented on Friday, Aug. 23 at the Goldschmidt conference in Barcelona, while the results of the study were published in the journal Science on Aug. 15.
After Earth formed, it was shaken by geological activity and impacts from space, which caused a lot of disturbances on the newly-formed planet. For a long time, researchers thought that there were no footprints of Earth’s original structure that remained. Then, during the 1980s scientists studied some basalt lavas from certain locations finding that the ratio of the helium 3 to helium 4 isotope was unexpectedly high, hinting at meteorites that had fallen to Earth long ago.
The results suggested that erupting lava brought up some diamonds from deep below Earth’s mantle, hinting at a reservoir deep beneath the Earth’s mantle.
“This pattern has been observed in ‘Ocean Island Basalts,’ which are lavas coming to the surface from deep in the Earth, and form islands such as Hawaii and Iceland,” research leader Dr. Suzette Timmerman, from the Australian National University said in a statement. “The problem is that although these basalts are brought to the surface, we only see a glimpse of their history. We don’t know much about the mantle where their melts came from.”
Timmerman’s team continued studying the helium isotope ratios in the superdeep diamonds, which formed between 250 and 400 miles beneath Earth’s mantle, and then were carried to the surface through eruptions. Those diamonds have different properties compared to the diamonds we see in jewelry.
“Diamonds are the hardest, most indestructible natural substance known, so they form a perfect time capsule that provides us a window into the deep Earth. We were able to extract helium gas from twenty-three super-deep diamonds from the Juina area of Brazil,” Suzette Timmerman said. “These showed the characteristic isotopic composition that we would expect from a very ancient reservoir, confirming that the gases are remnants of a time at or even before the Moon and Earth collided.”
According to Timmerman, further research is necessary for more information about the superdeep diamonds and Earth’s earliest days. Also the team wants to find out whether the stable reservoir is one large single reservoir or split among smaller ancient reservoirs scattered across Earth’s insides, as well as what is its chemical composition. This study helps understand the oldest undisturbed material on Earth.