Boffins find sign of water existing deep into Earth's mantle by looking at diamonds

How far down does water drip?

earth_mantle

Water covers most of the Earth’s surface and flows deep beneath it as well. But how deep it travels is unknown.

A team of scientists have found evidence that the liquid may exist at depths 400 miles below the crust, and maybe even penetrating within the Earth’s lower mantle. A paper published in Science describes the discovery of tiny, microscopic water molecules crystallized inside diamonds.

Samples extracted from the ground in Africa and China were studied using infrared spectroscopy at Lawrence Berkeley National Laboratory. Traces of water were found trapped in inclusions, small gaps and blemishes measuring a few microns across.

The boffins detected ice VII, a substance formed from the crystallization of water under extreme pressures. It’s estimated that some of these gemstones formed at approximately 24 to 25 gigapascals, a pressure about 224 times greater than the Mariana Trench, the deepest part of the ocean.

Oliver Tschauner, lead author of the study and a professor of geoscience at the University of Nevada, Las Vegas, said: “It's not just a curiosity to have a diamond residing deep in Earth's mantle - this is direct evidence for aqueous fluid in the deep Earth."

About 60 diamonds have been found and confirmed to have formed deep in the Earth at about 190 miles down. The team believe that the inclusions were created from water penetrating to depths of 250 miles to 340 miles beneath Earth’s surface. Some may have been shaped even deeper from 380 miles to 500 miles - near the transition zone between Earth’s upper and lower mantle.

Although the diamonds show water probably exists deep below, it’s unknown how much of it there is. The team hopes that any future studies might help scientists uncover how water is recycled and brought back up to the surface and how deep it goes. ®




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