Scientists from the Gemological Institute of America, looking into the Earth’s deep water cycle, studied an incredibly rare gem diamond discovered in the Karowe mine in Botswana. The gem, which originated from 410 miles below the surface of the Earth, contains a protected sample of the Earth’s lower mantle.
Analysis of the diamond found that it contained hydrated minerals, ringwoodite, enstatite and ferropericlase. According to findings published in the journal Nature Geoscience, this shows evidence that a water based environment extends into the Earth’s lower mantle.
The Earth’s lower mantle accounts for around 56 percent of its entire volume. It lies 410 to 1,800 miles below the surface of the Earth. But the deepest borehole on Earth measures 7.5 miles, meaning it is difficult for scientists to study what lies below.
The water from the Earth’s oceans is transported by hydrated minerals deep into the Earth. Volcanic activity then returns the water to the surface.
The new findings can help improve scientists’ understanding of this deep water cycle.
The lead author of the study, Tingting Gu from the Gemological Institute of America, told Newsweek that the mantle slivers collected from this diamond provide “factual evidence” of what the Earth’s lower mantle looks like.
“[This] is one of the great datasets for us to understand Earth’s mantle convection and water cycle, and scientists can directly use our result to build their geological models,” Gu said. “Water is quite important for our life, and the existence of liquid water on our planet is also unique. The depth of water that can be stored in Earth’s interior will determine its time scale to cycle back to the surface and influence the inventory of water on Earth’s surface and the distribution of water in Earth’s mantle. Water is important […]as a small proportion of water in the deep will mean a lot to the physical and chemical properties of the mantle and its convection.”
Gu said that the depth of the water that can be stored in Earth’s interior determines its time scale in its cycle back to the surface.
The coexistence of ringwoodite and other minerals within the diamond determine the existence of a water environment.
“[The] deep diamond harbors an interesting inclusion with ringwoodite in equilibrium with ferropericlase and enstatite (retrogressed bridgmanite) […] least shown by this diamond, we didn’t see a chemical block at this transition zone and lower mantle boundary, which means water and peridotite (a common upper mantle rock) can penetrate through this boundary,” Gu said.
