According to new research, most diamonds found at the Earth‘s surface are made of carbon from recycled ancient seabed. It‘s been a theory for a while, since some diamonds have traces of salt trapped in them. The theory goes that long ago, large slabs of seabed were plunged deep into the Earth as one tectonic plate slipped beneath another.
The seabed sank into the Earth‘s mantle, which is the part of the layer of the earth between the crust and the core. There, the seabed, sediments and salty seawater were compressed and began slowly reacting under intense pressure and temperatures to form the fluids from which the diamonds crystallized.
We can‘t go back in time to check whether things actually happened that way, but a team of researchers devised an experiment to test whether it was possible. They placed samples of marine sediment in a container with peridotite, the most common type of rock found in the part of the mantle where diamonds form. Then they turned up the pressure and heat, and found they‘d formed salts with compositions very similar to those found in diamonds.
The experiment also formed minerals that are the necessary ingredients for forming kimberlite magma, a special type of magma that transports diamonds to the Earth‘s surface.
