Most diamonds originate from ancient seabeds: study

Source: Xinhua| 2019-05-30 12:53:51|Editor: Liangyu
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SYDNEY, May 30 (Xinhua) -- The majority of diamonds which are extracted from the earth, most likely began as sediment on the bottom of ancient oceans, according to an Australian study released on Thursday.

Researchers at the University of Macquarie in the State of New South Wales, showed that traces of salt found in the most common types of diamonds, came from ancient seabeds which were driven deep down into the earth, where immense heat and pressure formed them into the precious gems of today.

For this process to have occurred, giant sections of seafloor would have had to sink rapidly deep below the earth's surface in a process known as subduction, in which one tectonic plate slides beneath another.

“There was a theory that the salts trapped inside diamonds came from marine seawater, but it couldn’t be tested,” lead author Doctor Michael Förster from Macquarie University explained.

To test the hypothesis, Förster teamed up with researchers at the Johannes Gutenberg Universität Mainz and Goethe Universität Frankfurt in Germany, where they conducted experiments recreating the conditions 200 km beneath the earth’s surface.

They placed marine sediment samples along with pieces of rock from the earth’s mantle where diamonds form, and then turned the heat up to between 800 degrees centigrade and 1,100 degrees centigrade and increased the pressure to between four and six gigapascals (40,000 times atmospheric pressure).

The experiment showed that under those conditions, salts formed with a balance of sodium and potassium that closely matches the small traces found in diamonds, proving the theory to be valid.

“We knew that some sort of salty fluid must be around while the diamonds are growing, and now we have confirmed that marine sediment fits the bill,” Förster said.

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