> The subducting slabs also carry deep-sea sediments piggyback into the Earth’s interior. These sediments can hold large quantities of water and CO2. But until now it was unclear just how much enters the transition zone in the form of more stable, hydrous minerals and carbonates – and it was therefore also unclear whether large quantities of water really are stored there.
> The answer has now been provided by an international study. The research team analyzed a diamond from Botswana, Africa. It originated at a depth of 660 kilometers, directly at the interface between the transition zone and the lower mantle, where the dominant mineral is ringwoodite. Diamonds from this location are very rare, even among the extremely rare diamonds of super-deep origin, which account for just 1% of all diamonds. The studies found that the stone had a high water content due to the presence of many ringwoodite inclusions. The study team was also able to establish the chemical composition of the stone.
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