Scientists name conditions under which diamond eruptions occur on Earth
Tectonic plate faulting, which occurs during the formation of new continents on Earth, is the driving force behind the formation and eruption of diamond-rich magmas from the Earth's interior.
This is stated in a study by an international team of scientists led by the University of Southampton, published in the journal Nature. The scientists' new theory may suggest where to look for new diamond deposits.
Diamonds are known to form under high pressure at a depth of about 150 kilometres over hundreds or even billions of years. They can usually be found in kimberlites, igneous rocks found in the oldest, thickest and strongest parts of continents. But previously, scientists did not understand how and why kimberlites with diamonds appeared on the Earth's surface.
Now, scientists have discovered that the pattern of diamond eruption is cyclical and follows the rhythm of supercontinents, which assemble and disintegrate over time in a repeating pattern.
"Previously, we didn't know what process causes diamonds to suddenly erupt after spending millions - or billions - of years buried 150 kilometres below the Earth's surface," said lead author Tom Gernon, professor of earth sciences and chief scientist at the University of Southampton.
The study found that the majority of kimberlite volcanoes erupted 20-30 million years after the tectonic breakup of the Earth's continents.
They also discovered other interesting aspects. According to Dr Thea Hinks, a senior researcher at the University of Southampton, kimberlite eruptions tend to gradually migrate from the continental margins to the interior at a rate that is the same on all continents.
This discovery prompted scientists to investigate what causes this pattern. It turned out that the Earth's mantle - the layer between the crust and core - is disturbed by faults in the Earth's crust, even at a distance of thousands of kilometres.
"We have found that the domino effect can explain how continental breakup leads to the formation of kimberlite magma," said Dr Stephen Jones, Associate Professor of Earth Systems at the University of Birmingham and co-author of the study.
As tectonic plates move apart, the base of the continental crust thins - just as the crust on top stretches and forms valleys. When hot rock rises from the depths, it comes into contact with this broken boundary, cools and sinks back down again, creating localised circulation zones.
One such unstable region can trigger a similar movement in neighbouring regions, gradually migrating thousands of kilometres into the centre of the continent. This corresponds to the actual pattern of kimberlite eruptions, which start near rift zones and then move inland.
When it comes to diamond eruptions from deep within the Earth's crust, Gernon says it's all about mixing the right materials. Instability causes rocks from the upper mantle and the lower crust to start flowing against each other. This mixes the rock with the large amounts of water and carbon dioxide it contains, along with many of the key minerals in kimberlite, including diamonds.
According to Gernon, the result is an effect similar to shaking a bottle of champagne: an eruption with great explosive potential and buoyancy that brings kimberlites with diamonds to the surface.
The study may be useful not only for finding undiscovered diamond deposits, but also may explain why eruptions occur in regions that are generally stable after the breakup of a supercontinent.
Earlier, OBOZREVATEL also reported that a new supercontinent will appear on Earth in the future.