Science & Technology, South Africa (Commonwealth Union) – Superdeep diamonds, dating back to a period between 650 and 450 million years ago, provide valuable insights into the development and migration of continents. Through the examination of these ancient superdeep diamonds unearthed from mines in Brazil and Western Africa, researchers have unveiled previously unknown processes that shed light on the early stages of complex life on Earth and the evolution of continents.
These diamonds, which took shape at the base of the supercontinent Gondwana during the specified timeframe, have undergone analysis by an international team of experts. Their findings reveal essential information regarding the formation and stabilization of supercontinents like Gondwana, as well as the mechanisms governing their movement across the Earth’s surface.
“Superdeep diamonds are extremely rare and we now know that they can tell us a lot about the whole process of continent formation,” explained Dr Karen Smit from the Wits School of Geosciences, who participated in the research. “We wanted to date these diamonds to try and understand how the earliest continents formed.”
Having originated millions to billions of years ago, diamonds possess a unique ability to illuminate the deepest and most ancient recesses of the Earth’s mantle. The ever-shifting continents on the Earth’s surface undergo a cyclical phenomenon known as the “supercontinent cycle,” during which supercontinents form and disintegrate. Among the limited number of minerals robust enough to endure and chronicle these historic cycles of creation and dissolution, diamonds stand out.
Supercontinents play a pivotal role in concentrating the process of deep oceanic plate subduction, a primary driver of plate tectonics, in specific regions. Examining these deep geological mechanisms, especially from earlier periods, has proven challenging due to the youth of oceanic crust and the limited insights offered by continental crust into the Earth’s profound workings. Ancient diamonds offer a direct window into the inner workings of the planet’s plate tectonic engine and its connection to the supercontinent cycle.
Under the leadership of Dr. Suzette Timmerman from the University of Bern in Switzerland, the research team conducted an investigation involving the dating of tiny silicate and sulfide inclusions within diamonds. These diamonds formed at depths ranging from 300 to 700 kilometers beneath the base of the Gondwana supercontinent. The primary objective was to trace the manner in which materials were incorporated into the foundation of the supercontinent, ultimately leading to the revelation of an hitherto unknown geological process.
As the research, published in Nature on October 18, demonstrates, the geochemical analyses and dating of inclusions within these diamonds, combined with existing models of plate tectonics related to continent migration, unveiled a fascinating narrative. The diamonds took shape deep beneath Gondwana, precisely when this supercontinent blanketed the South Pole, spanning a timeframe of 650 to 450 million years ago according to Smit. During diamond formation, the rocks hosting these precious gemstones became buoyant, effectively carrying mantle material that had undergone subduction, along with the diamonds themselves. This material was subsequently added to the foundation of Gondwana’s keel, contributing to the “growth” of the supercontinent from below.
“Around 120 million years ago, Gondwana started to break apart to form the present oceans such as the Atlantic. At 90 million years ago, the diamonds, carrying trapped tiny inclusions of the host rock, were brought to Earth’s surface in violent volcanic eruptions.”
The present locations of these volcanic eruptions are situated on the continental remnants of Brazil and Western Africa, which represent integral components of the ancient supercontinent, Gondwana. Consequently, it is evident that these diamonds must have undertaken a journey in unison with distinct segments of the former supercontinent as it fragmented, effectively remaining “affixed” to its foundational elements.
