Unveiling Secrets: Diamond From 400 Miles Below Earth Sheds Light on Hidden Water-Rich Environments

Deep within the Earth, fascinating processes are constantly at work. Sometimes, these processes reveal secrets from below, like rare diamonds that carry information about our planet’s interior.

Recently, a diamond found in Botswana has captured attention. This unique gem has imperfections filled with traces of minerals like ringwoodite, ferropericlase, and enstatite. These minerals hint that the diamond formed an astonishing 660 kilometers (about 410 miles) beneath Earth’s surface.

This underground environment, known as the transition zone, sits between the upper and lower mantle and seems to have abundant water. According to a study led by mineral physicist Tingting Gu, these findings indicate a moist area at this significant boundary.

While oceans cover most of the Earth’s surface, they only reach a maximum depth of about 11 kilometers (7 miles). In contrast, the distance to the Earth’s core is thousands of kilometers. The crust itself is a patchwork of tectonic plates that can push and pull against each other, allowing water to seep deep into the Earth.

Water that makes its way down does eventually come back up through volcanic eruptions. This process is part of what scientists call the deep water cycle. Understanding this cycle is essential because water influences volcanic activity and seismic movements.

Since we can’t directly access these depths, diamonds often serve as our messengers from deep within the Earth. Gu and her research team examined one of these gems closely, identifying 12 different mineral inclusions. Using advanced techniques like micro-Raman spectroscopy and X-ray diffraction, they learned more about these minerals.

Among the inclusions was ringwoodite, a magnesium silicate, alongside ferropericlase and enstatite. The high pressure in the transition zone causes ringwoodite to break down into other minerals like bridgmanite. This process reveals the diamond’s journey from the depths back to the crust.

Interestingly, the ringwoodite contained characteristics suggesting it was formed with water present. Other minerals found in the diamond also point to a wet environment. While previous studies hinted at water in the transition zone, this research supports the idea that it is moist and possibly filled with water.

Gu and her team noted that their findings represent the presence of water across a broader area in the transition zone rather than just isolated pockets. This could change how we think about water beneath our feet.

This new insight into the Earth’s interior was published in Nature Geoscience.