Diamonds form under great pressures in the depths of the Earth and are hundreds, or even billions of years old. They are usually found in types of volcanic rocks called kimberlites, which are located in the oldest, strongest, and thickest parts of the continents, such as in South Africa, where the well-known diamond rush of the 19th century occurred. However, how diamonds reach the Earth’s surface has largely remained a mystery until recently. Now, a team of researchers led by the University of Southampton and the University of Birmingham has found that the breakup of tectonic plates is the main driving force behind the generation and ultimate eruption of diamond-rich magmas from deep inside the Earth.
“We found that a domino effect can explain how continental breakup leads to formation of kimberlite magma. During rifting, a small patch of the continental root is disrupted and sinks into the mantle below, triggering a chain of similar flow patterns beneath the nearby continent,” explained co-author Stephen Jones, an associate professor of Earth Systems at Birmingham.
The experts used statistical analysis and machine learning algorithms to forensically examine the connection between continental breakup and kimberlite volcanism. The investigations revealed that the eruptions of most kimberlite volcanoes occurred 20 to 30 million years after the initial tectonic breakup of our planet’s continents. “Using geospatial analysis, we found that kimberlite eruptions tend to gradually migrate from the continental edges to the interiors over time at rates that are consistent across the continents,” said co-author Thea Hincks, a senior research fellow in Geology at Southampton. These findings prompted the scientists to examine what geological processes may drive this pattern. They discovered that the Earth’s mantle – the convecting layer between the planet’s crust and core – is often disrupted by rifting, or stretching, of the crust, a phenomenon occurring even thousands of kilometers away. The result leads to a domino effect which can help explain how continental breakup causes the formation of kimberlite magma.
