A recent discovery by international researchers has identified the breakup of tectonic plates as the driving force behind the generation and eruption of magma from deep inside the Earth.
Diamonds are typically found in a type of volcanic rock known as kimberlite, which is found in the oldest and thickest parts of continents; however, how these diamonds reach the surface has remained a mystery.
In a study published in Nature, researchers examined the effects of global tectonic forces on volcanic eruptions spanning the past billion years.
“The pattern of diamond eruptions is cyclical, mimicking the rhythm of the supercontinents, which assemble and break up in a repeated pattern over time,” said Dr. Tom Gernon of the University of Southampton.
“But previously we didn’t know what process causes diamonds to suddenly erupt, having spent millions – or billions – of years stashed away 150 kilometres beneath the Earth’s surface.”
The project used statistical analysis to forensically examine the connection between continental breakup and kimberlite volcanism.
The results showed the eruptions of most kimberlite volcanoes occurred 20 to 30 million years after the tectonic breakup of Earth’s continents. This insight prompted the scientists to explore what geological process could drive this pattern.
They found that the Earth’s mantle is disrupted by a rifting of the crust. During rifting, a patch of the continental root is disrupted and sinks into the mantle below. This triggers a chain of similar flow patterns beneath the nearby continent.
While diamonds are formed under immense pressure deep within the Earth, many are discovered close to the surface.
Perhaps the most notable example of this phenomenon is the 3106-carat Cullinan Diamond. The Cullinan is estimated to have formed in Earth's mantle transition zone at a depth of approximately 410 kilometres.
The diamond was discovered just five metres below the surface at the Premier Mine in 1905.
“Breakup not only reorganises the mantle but may also profoundly impact Earth’s surface environment and climate, so diamonds might be just a part of the story,” Gernon said.
This new research could be used to identify the possible locations and timings of past volcanic eruptions tied to this process, offering valuable insights that could enable the discovery of diamond deposits in the future.
More reading
Diamond reveals new details of Earth’s interior
Did ancient sea creatures help create the Queen’s diamonds?
Strange diamonds found in meteorites