A fascinating journey from deep within the Earth: The Formation of Diamonds
A diamond is widely recognized as a symbol of eternal commitment and unity, thanks to a successful advertising campaign in the 1940s that coined the famous phrase “A diamond is forever.” However, our groundbreaking research, published in the renowned journal Nature, has unveiled a new perspective on diamonds: they may also provide clues about the Earth’s internal structure and the process of tectonic plate movement. Moreover, this knowledge could potentially guide us to discover new diamond mines.
Formed under extreme pressure and high temperatures deep within the Earth, diamonds are the hardest naturally occurring stones. The question arises: how do these precious gems make their way from the depths to the surface? The answer lies in the transportation of diamonds in molten rocks called kimberlites. Until now, the mechanism behind the sudden eruption of kimberlites through the Earth’s crust, after millions or even billions of years beneath the continents, has remained a mystery.
Geologists widely agree that diamond eruptions are closely linked to the formation and breakup of supercontinents, which have shaped Earth’s history for billions of years. However, the exact processes underlying this relationship have been a subject of debate. Two main theories have emerged: one suggests that the eruptions are triggered by fractures in the Earth’s crust during tectonic plate movements, while the other proposes the involvement of mantle plumes—massive upwellings of molten rock from the core-mantle boundary.
Although these theories have their limitations, our study has shed new light on this long-standing conundrum. Through a meticulous statistical analysis, including the application of machine learning—an element of artificial intelligence (AI)—we have uncovered a significant correlation between continental breakup and kimberlite volcanism. Our global study indicated that most kimberlite eruptions occurred 20 to 30 million years after the tectonic breakup of continents, and our regional study specifically focusing on Africa, South America, and North America strongly supported this finding. Additionally, we identified a crucial pattern: kimberlite eruptions gradually migrate from the continental edges to the interiors in a consistent manner across the continents.
This discovery naturally leads us to the following question: what geological process drives these patterns? To address this query, we employed advanced computer models to simulate the complex behavior of continents under stretching conditions, alongside the convective movements within the underlying mantle. As a result, we propose a domino effect: during rifting, a small portion of the continental root—a thick rock layer beneath some continents—disrupts and submerges into the mantle. This process triggers edge-driven convection, characterized by the sinking of colder material and the upwelling of hot mantle. Our models reveal that this convection initiates a series of similar flow patterns beneath the nearby continent. As these disruptive flows sweep along the continental root, they remove a substantial portion of rock from the base of the continental plate, leading to the generation of kimberlite magma through the precise amount of melting required.
Once formed, the buoyant kimberlite magma rises swiftly to the surface, carrying with it the precious diamonds. It is essential to note that our model does not contradict the spatial association between kimberlites and mantle plumes. On the contrary, the breakup of tectonic plates may be influenced by the warming, thinning, and weakening of the plate caused by plumes. However, our research demonstrates that the spatial, temporal, and chemical patterns observed in regions rich in kimberlites cannot be solely explained by the presence of mantle plumes. Instead, the eruption-triggering processes appear to follow a highly systematic pattern, starting at the continental edges and migrating uniformly towards the interior.
This valuable information has significant implications for the identification of potential diamond deposits and the exploration of other rare elements necessary for the advancement of green energy. As we embark on the search for new deposits, it is crucial to consider ethical concerns. Various campaigns are actively working towards eliminating conflict diamonds—those used to fund wars—and diamonds sourced from mines with poor working conditions from the global market.
While diamonds may not last forever, our research demonstrates that they have been consistently formed throughout the long history of our planet. With a deeper understanding of the Earth’s internal processes, we are one step closer to unraveling the mysteries of these extraordinary gemstones.
This article was originally published on The Conversation and has been republished under a Creative Commons license.
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Shambhu Kumar is a science communicator, making complex scientific topics accessible to all. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
