The diamond formed at a depth of 660 km reveals the water-filled environment in the Earth’s mantle

A study published in the journal Geosciences of nature shows that a recently discovered diamond in Botswana formed in a water-rich environment 660 km deep between the Earth’s upper and lower mantle.

The diamond has traces of ringwoodite, ferropericlase, enstatite and other minerals that reveal the secrets of its formation. “The presence of ringwoodite indicates a humid environment at this boundary,” says the team of scientists led by Tingting Gu of the Gemological Institute of New York and Purdue University.

water in the depths

Most of the earth’s surface is covered by oceans, but all that water is next to nothing considering the thousands of kilometers between the outermost crust and the core of our planet. To give you an idea, the deepest point in the ocean is 11km from the surface, while our core is at an impressive 5150km depth.

However, the earth’s crust is fragmented, with several tectonic plates rubbing against each other and often “sliding” under each other. In these places, called “subduction zones”, ocean water seeps under the crust and can reach the lower mantle.

Over time, this water returns to the surface through volcanic activity. This descent and ascension process is known as the “deep water cycle”, and knowing how it works and how much water there is down there is very important to understanding the geological activity of the Earth. For example, the presence of water can affect the explosive power of a volcanic eruption.

the diamond

Due to the impossibility of reaching such depths, we depend on the evidence that the water reaches us, as happened with the diamond found in Botswana, which has formed a sort of crystal “cage” thanks to the extreme heat and pressure of the water. environment in which it was located.

In this “cage,” Gu’s team found a cluster of ringwoodite (magnesium silicate), ferropericlase (iron / magnesium oxide) and enstatite (another magnesium silicate, but with a different composition).

When exposed to the high pressure of the transition zone between the upper and lower mantle, ringwoodite breaks down into ferropericlase and another mineral called “bridgmanite”. At the points closest to the surface, where the pressure is lowest, the bridgmanite transforms into enstatite. The presence of these minerals in the diamond indicates that it has made a real journey through the interior of the Earth, forming in the depths of the mantle before reaching the crust.

Furthermore, the ringwoodite found in the diamond seems to have formed in the presence of water, as in the case of another mineral that made up the “mixture” of this diamond, brucite.

The scientific community has already found evidence of water in deep geological strata, but it is not yet known how humid these places are. Gu’s research shows there’s a lot of water down there.

The post-formed diamond at a depth of 660 km reveals that a water-filled environment in the Earth’s mantle first appeared on Olhar Digital.

Source: Olhar Digital