450-million-year-old diamonds reveal secrets of Earth’s evolution

Ancient superdeep diamonds from Brazil and West Africa, which formed beneath the supercontinent Gondwana 650 to 450 million years ago, have provided new insights into the formation, positioning and movement of supercontinents. Studied by an international team, these diamonds serve as lasting records of Earth’s supercontinent cycles. Their analysis uncovers previously unknown geological processes and shows the integral role of diamonds in the development of supercontinents such as Gondwana.

Superdeep diamonds formed between 650 and 450 million years ago show how the continents grew and moved.

Analysis of ancient, ultra-deep diamonds unearthed from mines in Brazil and West Africa has revealed unknown mechanisms behind the evolution and movement of continents during the early evolution of complex life on Earth.

The diamonds, which formed between 650 and 450 million years ago at the base of Gondwana, were analyzed by an international team of experts to show how supercontinents such as Gondwana formed, stabilized and orbited the planet.

Valuable insights from diamonds

„We now know that superdeep diamonds are so rare that they can tell us a lot about the whole process of continent formation,” says Dr Karen Schmidt of the Wits School of Geosciences, who was part of the study. „We wanted to date these diamonds to try to understand how the early continents formed.”

Karen Smith

Dr Karen Smit at the newly created Isotope Laboratory in the School of Earth Sciences at Wits University. Credit: Wits University

Diamonds, formed millions to billions of years ago, can shine light into the darkest and oldest parts of the Earth’s crust. Continents move across Earth’s surface, creating and destroying „supercontinents.” Collectively, these migrations are called the „Supercontinent Cycle,” and diamonds are one of the few minerals strong enough to survive and record these ancient cycles of creation and destruction.

Deep Tectonic Insights

Supercontinents can focus deep-ocean plate subduction in very specific areas—the driver of plate tectonics. Such deep geologic processes have been particularly difficult to study directly, especially in the past, because the oceanic crust is young, and the continental crust provides only a limited view of Earth’s deep activities. Old diamonds provide a direct window into the deep plate tectonic engine and how it may relate to supercontinent rotation.

By dating the tiny silicate and sulphide inclusions within the diamonds, the team led by Dr Suzette Timmerman University of Bern, Switzerland, dated diamonds formed at depths of 300 to 700 km at the base of Gondwana. The goal was to discover how material was added to the supercontinent’s hinge. In doing this, the team recognized a previously unknown geological process. The study was recently published in the journal Nature.

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

The role of diamonds in supercontinent development

The host rocks for the diamonds became buoyant as the diamonds formed, transporting the subducted mantle material and diamonds. This material was added to the base of Gondwana’s root, in essence, 'growing’ the supercontinent from below.

„About 120 million years ago, Gondwana began to break up to form the current oceans like the Atlantic. About 90 million years ago, diamonds, carrying tiny inclusions trapped in the host rock, were brought to Earth’s surface in violent volcanic eruptions.

Diamonds with fine silicate and sulphide inclusions

Diamonds with microscopic silicate and sulfide inclusions revealed new processes for how the continents formed and stabilized, allowing for the early evolution of life on Earth. Credit: Wits University

The current locations for these volcanic eruptions are on the continental shelf of Brazil and West Africa, the two major components of Gondwana. Thus, the diamonds must have dispersed and migrated together with different parts of the former supercontinent „glued” to their base.

„This complex history of diamonds shows that they have traveled remarkably well, both vertically and horizontally, within the Earth – tracing both the formation of the supercontinent and the last stages of its evolution. The accretion of relatively young material to the roots of the continents binds these ancient continental fragments together and suggests a possible new pattern of continental growth. indicates.

Further research and development

Schmidt conducted isotope analyzes of sulfide inclusions Carnegie Institution for Science. Schmidt is now at the University of the Witwatersrand, where he is part of a team developing a new isotope laboratory and methods so that diamond inclusion analyzes can eventually be conducted at Wits.

„We’ve installed the necessary equipment in 2022 and we’re working to get more specialized skills and equipment together so we can do this kind of diamond work in South Africa that previously could only be done overseas,” says Smith.

„We need this kind of research to understand how continents form and move. Without continents, there would be no life. This research gives us insight into how continents form, and it gives us insight into how life evolved and what makes our planet Earth different from other planets.

Note: Suzette Timmerman, Thomas Stachel, John M. Kornnief, Karen V. Schmidt, Ricky Harlow, Geoff M. Nowell, Andrew R. Thompson, Simon C. Cohn, Joshua HFL Davis, „Sublithospheric Diamond Ages and the Supercontinent Cycle” 1999; Gareth R. Davis, Mandy Y. Krebs, Qiu Zhang, Sarah EM Milne, Jeffrey W. Harris, Felix Kaminsky, Dmitry Zetgenisov, Galina Bulanova, Chris B. Smith, Isaac Cabral Neto, Francisco, v. Silvey. Burnham, Fabrizio Nestola, Steven P. Shire, Michael J. Walter, Andrew Steele and D. Graham Pearson. Nature.
DOI: 10.1038/s41586-023-06662-9

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