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Scientists discover ancient sea salt in diamonds, proving their extraordinary origins



The earth is not one that sits still. For about 3 billion years, our planet has been continually recycling its seabed, devouring old oceanic crusts in some areas and potting new seabed in other areas. Diamonds seem to be the beautiful byproducts of all this restlessness.

Researchers have shown that most diamonds are dipped carbon crystals cooked from recycled seabed crusts deep in the ground.

"There was a theory that the salts enclosed in diamonds come from seawater, but could not be tested," says lead author Michael Förster of the Technical University of Berlin.

"Our research has shown that they originate from marine sediments."

The word "diamond" derives from the Greek term "adamas", which means "invincible". The name is an indication of the hardness of the material, but might as well describe the birthplace of the gemstone.

Apart from those who came here from space, most diamonds form in very old parts of the Earth's mantle, a layer that makes up over 80 percent of the planet's total volume and has never been visited by humanity.

By comparison, the thin crust we currently live on accounts for only one percent of the planet's volume. However, this crust is still about 35 kilometers deep, which is why it is difficult for us to investigate the Earth's mantle directly.

Only this week, a decades-long drill mission to observe these mysterious depths was set after a "continuous six-month nightmare" in which the hole collapsed again and again.

Without access to the mantle, the true formation of diamonds has been an unanswered question for many years. An international team of geoscientists, led by researchers from Macquarie University in Australia, has now sought to govern the debate on the comfort of the earth's surface.

The team has shown that seawater in seabed sediments can absolutely create the balance of saline fluids common in diamonds.

Nowadays most of the diamonds we see in shops or on fingers appear crystal clear and are appreciated for their quality. But there are also "fibrous diamonds" ̵

1; these form so fast that they accidentally include traces of sodium, potassium and other minerals. These inclusions give them a dull appearance, but this contamination also gives us a clear insight into their past.

The team studied the formation of salty diamonds by placing marine sediment samples along with a common type of mantle in a sealed vessel called peridotite. They turned up pressure and heat and tested how different conditions in parts of the mantle could affect these salty liquids.

The most diamond-like equilibrium of sodium and potassium occurred at temperatures between 800 ° C and 1100 ° C, pressures between four and six gigapascals and depths between 120 and 180 kilometers below the Earth's surface.

"If & # 39; most diamonds were created equal, it follows that the reaction between sedimentary rocks and peridotite during subduction is a major mechanism for the formation of lithospheric diamonds and clad carbonates," the authors conclude.

For diamonds like these, they formulate themselves, conditions just have to be that way. For example, a large seabed would have to slide more than 200 kilometers; This tectonic slippage, which is called subduction, would have to happen fairly quickly.

Before this huge plate reaches the top of 800 ° C and begins to melt, it must compress the atmospheric pressure of our planet by 40,000 times. Otherwise, no diamond is born.

During this process, saline fluids from ancient marine environments also slip into the lower mantle and interact with peridotites, creating chlorides. These melt later and form diamond-bearing volcanic rocks, called kimberlites, which eventually erupt on the earth's surface so that we can find and appreciate them.

Subduction Zones, "says Förster.

In other words, this diamond in your jewelry box has seen more of the planet than we humans could ever hope for. It's essentially about hundreds of millions of years of deep-sea history leading to a tiny,

The research was published in Science Advances .


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