Analysis of ancient ultra-deep diamonds unearthed in mines in Brazil and West Africa has revealed new evolutionary processes and continental drift during the early evolution of complex life on Earth. These diamonds, which formed at the base of the Gondwana supercontinent between 650 and 450 million years ago, were analyzed by an international team of experts to show how supercontinents like Gondwana were formed, stabilized and moved around the planet.

Dr. from Wits School of Geosciences, who participated in the research. “Ultra-deep diamonds are extremely rare, and we now know that they can tell us a lot about the entire process of continent formation,” says Karen Smith. “We wanted to date these diamonds to try to understand how the oldest continents formed.”

Formed millions and billions of years ago, diamonds can illuminate the darkest and oldest parts of the Earth’s mantle. Continents drift across the Earth’s surface, forming and destroying “supercontinents”. Collectively, these migrations are known as the “supercontinental cycle,” and diamonds are among the few minerals strong enough to survive and record these ancient cycles of creation and destruction.

Supercontinents may concentrate the deep subduction of oceanic plates, which are the driving forces of plate tectonics, in very specific regions. Direct study of such deep geological processes has been very difficult, especially in the past, because the oceanic crust is young and the continental crust provides only a limited view of the deep workings of the Earth. Ancient diamonds offer a direct window into the deep mechanism of plate tectonics and how it may be related to the supercontinent cycle.

Dr. from the University of Bern, Switzerland. A team led by Suzette Timmerman determined the age of the diamonds, which formed 300 to 700 km below the floor of Gondwana, by identifying small traces of silicate and sulfur within the diamonds. The goal was to track how material was added to the supercontinent’s backbone. While doing this, the team noticed a previously unknown geological process. The study was published on: Nature.

“Geochemical analysis and dating of the inclusions in the diamonds, combined with existing tectonic models of continental migration, showed that the diamonds formed at great depths beneath Gondwana between 650 and 450 million years ago, when the supercontinent covered the South Pole,” Smith says. . .

Diamond-bearing rocks became buoyant during diamond formation, carrying buoyant mantle material and diamonds. This material was added to the base of the Gondwana root, essentially “growing” the supercontinent from below.

“About 120 million years ago, Gondwana began to break up and form modern oceans such as the Atlantic. 90 million years ago, diamonds containing small rock debris were brought to the Earth’s surface during powerful volcanic eruptions. “

The modern sites of these volcanic eruptions are on the continental parts of Brazil and West Africa, two major components of Gondwana. Therefore, as the diamonds dispersed to different parts of the former supercontinent, they must have migrated by “sticking” to their bases.

“This complex history of diamonds suggests that they travel exceptionally well within the Earth both vertically and horizontally, tracking both the formation of the supercontinent and the final stages of its evolution. The deposition of relatively young material into continental roots thickens and consolidates these older continental fragments, “It points to a potential new mode of continental growth.”

Smith performed isotopic analysis of sulfide residues at the Carnegie Institution for Science. Smith currently works at the University of the Witwatersrand, where he is part of a team developing a new isotope laboratory and technique so that analysis of diamond inclusions can be carried out at Wits.

“We installed the necessary equipment in 2022 and are looking to bring together highly specialized skills and equipment to be able to do this type of diamond work in South Africa, which could previously only be done abroad,” says Smith.

“We need research like this to understand how continents develop and move. Without continents, there would be no life. This research tells us about how continents form and how life develops, and what makes our planet Earth different from other planets.”