Cleaving of continents: diamonds, AuScope and the deep

Two recent AuScope enabled Nature papers explore the drivers behind the explosive origins of diamonds. Image: AuScope

Diamonds are formed under extreme pressure and temperature in some of Earth’s thickest continents. EarthByte researchers and AuScope geochronologists from Macquarie University have revealed new details about the interaction between plate tectonics, volcanoes and diamonds. Their NCRIS enabled insights have been published in two separate papers: Nature Scientific Reports and Nature.

The edges of continents

Diamonds are found in kimberlites, a volcanic rock from the depths of the Earth. EarthByte’s Ben Mather notes that most kimberlites erupt from beneath stable continental plates, unlike typical volcanoes near the edges of continents. Their explosive ascent, several meters per second, is driven by abundant carbon dioxide, water and the changing underbelly of tectonic plates. He suggests:

“Kimberlites are the Bugatti of volcanic products. They host most of the world’s diamonds and offer rare insights into the composition of Earth’s deep interior.”

GPlately and Kimberlites

In their recently released Nature Scientific Reports paper, Ben Mather, Dietmar Müller, Christopher Alfonso, Maria Seton and Nicky Wright used GPlately to generate deep-time tectonic modelling that revealed how the subducting oceanic plate's angle shapes these volcanic regions' evolution and timing.

Angle of subducting slabs entering the Earth’s mantle overlain with kimberlite eruptions. Source: EarthByte

Pangea

Ben notes that the biggest kimberlite eruption preserved on the Earth coincided with the supercontinent Pangea's break up. Previous studies have suggested that kimberlites form close to large blobs in the lower mantle or are associated with changes in plate motion. In their study, Ben and colleagues suggest that subduction stimulated the upwellings in the Earth’s mantle, leading to kimberlite eruptions in Africa and North America.

“The results of this study have numerous potential applications, including modelling the deep carbon and water cycles and improving the understanding of subduction-related mineral deposits.”
– Ben Mather

Geochemistry and Kimberlites

In the second paper, recently published in Nature, AuScope’s Earth Composition & Evolution project leader Sue O'Reilly and colleagues explored the origins of Kimberlites. Most of the geochronology data crucial to interpreting the geotectonic context of kimberlites and relevant mantle domains in this study were produced by the AuScope instruments at our Macquarie University Earth Composition and Evolution node. Sue notes that:

“Understanding diamond genesis and distribution provides invaluable insight into the 4.56 billion years of evolution of our Earth and the continents on which we live.”

This recent dive into all things diamonds has garnered interest from the New York Times to The Conversation and more.