CaSiO3 perovskite in diamond indicates the recycling of oceanic crust into the lower mantle

Sparkling secrets from the Earth’s interior

2 April 2019

Peering into a priceless diamond shines light on the inner workings of the Earth.

Calcium silicate perovskite is thought to be Earth’s fourth most abundant mineral, but it has never been observed in nature because it is unstable at the Earth’s surface.

A team that included University of Cape Town researchers have used X-ray and infrared imaging to peer inside a diamond found in the same South African mine as two of the British crown jewels. They discovered a pocket of calcium silicate perovskite preserved inside the diamond.

The mineral’s structure suggests it started out as oceanic crust, which gradually sank deep into the Earth until it reached the immense pressures required to form calcium silicate perovskite, which resurfaced millions of years later encased in a diamond.

This is the strongest evidence yet that oceanic crust, and hence surface carbon, is recycled deep within the Earth.

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References

1. Nature 555, 237–241 (2018). doi: 10.1038/nature25972