Deep beneath the Earth’s surface, hidden more than 150 kilometers below, lies the fiery crucible from which some of the planet’s most extraordinary gems are born. These are the kimberlites, unique volcanic pipes that act as the primary carriers of diamonds from the lowermost reaches of the mantle to the surface. Despite their global significance in the diamond industry—over 70% of the world’s diamonds originate from kimberlites—scientists have only recently begun to unravel the complex physical and chemical processes that govern their violent eruptions. The mysteries surrounding how these deep-rooted melts ascend so rapidly have long puzzled geologists and petrologists alike.
Kimberlites are remarkable not only for their gem-bearing capacity but also because they provide one of the rare natural windows into Earth’s deep interior. These carrot-shaped volcanic structures erupt explosively, and evidence suggests that their magma ascends through the mantle and crust at extraordinary speeds, estimated in some studies to be as fast as 80 miles per hour. Such rapid ascent is critical: it allows diamonds, which are stable only under immense pressure, to be preserved on their path to the surface rather than transforming into graphite, the more thermodynamically stable form of carbon at shallower depths. Along their journey, the kimberlite magmas also entrain xenoliths and xenocrysts—rock fragments and mineral grains torn from the surrounding rock—which provide further clues about mantle composition and the physical conditions at depth.
In a breakthrough study published recently in the journal Geology, a team of researchers from the University of Oslo has leveraged cutting-edge molecular modeling to shed light on the physicochemical properties that enable kimberlite magmas to ascend so rapidly. Led by Ana Anzulović, a doctoral research fellow at the University’s Centre for Planetary Habitability, the study pioneers a method to quantify the influence of volatile compounds—specifically carbon dioxide (CO₂) and water (H₂O)—on the buoyancy of proto-kimberlite melts. This work represents a crucial advance in understanding the ascent dynamics of kimberlite magmas and explains why certain volatile concentrations are necessary for an eruption to succeed.
Modeling the behavior of kimberlite melts is inherently challenging due to their complex and variable chemistry, compounded by the fact that the original melts cannot be sampled directly. Instead, petrologists have traditionally relied on the study of heavily altered and metamorphosed kimberlite bodies, making it difficult to reconstruct the melt’s pristine composition and properties. To overcome these obstacles, Anzulović’s team adopted a robust computational strategy, focusing on the Jericho kimberlite located within Canada’s remote Slave craton—a geologically ancient and stable region of the crust. By simulating various mixtures of CO₂ and H₂O under realistic pressure and temperature gradients, the team was able to “sample” the kimberlite melt virtually as it would ascend through the mantle and crust.
The researchers employed molecular dynamics simulations—a powerful computational tool that calculates atomic interactions over time—to track how volatile elements influence the structural and physical characteristics of the melt at varying depths. Through these simulations, the team derived density profiles for different melt compositions, crucially determining whether the melt would remain less dense than the surrounding mantle peridotite and thus maintain buoyancy. Their findings conclusively establish that the interplay between water and carbon dioxide is fundamental: water acts to enhance diffusivity, keeping the melt highly fluid and mobile even under extreme conditions, whereas carbon dioxide contributes to the melt’s structural framework at depth but becomes a driving force for eruption upon degassing near the surface.
One of the most groundbreaking conclusions is that the Jericho kimberlite requires a minimum CO₂ concentration of approximately 8.2% by weight to sustain its buoyancy and trigger an eruption. Without sufficient carbon dioxide, the melt’s density surpasses that of the surrounding mantle, causing it to stall and crystallize before it can reach the surface. This quantitative constraint is the first of its kind, harnessing detailed chemical models and physics-based computations to connect microscale melt chemistry with large-scale volcanic phenomena. Furthermore, their most volatile-rich melt models revealed the remarkable capacity to transport as much as 44% mantle peridotite xenoliths, facilitated by the melt’s extremely low viscosity.
This research elegantly links the microscale chemical behavior of volatile components with the macro-scale geological phenomenon of kimberlite eruption. It offers a compelling explanation for how diamonds, among Earth’s hardest and most coveted substances, are ferried from the great depths where they grow—conditions impossible to replicate close to the surface—to accessible locations where mining is viable. Retaining the diamond structure during this journey is heavily contingent on the rapid rise promoted by volatile-driven buoyancy, a process now better understood thanks to these sophisticated simulations.
Importantly, the lessons of this research extend beyond kimberlite pipes alone. They highlight the complex feedback mechanisms between magmatic volatiles, melt structure, and mantle dynamics that are likely relevant for other deep-sourced volcanic systems. By elucidating the role of carbon dioxide and water in modulating magma ascent velocity and density, future studies could refine volcanic hazard predictions and deepen our grasp of mantle geochemistry.
Anzulović reflects on the surprising simplicity behind these complex processes: “To think that the presence or absence of a small percentage of carbon drastically determines whether a kimberlite can erupt is truly fascinating. It shows that even minuscule chemical variations at the atomic scale can control enormous geological processes extending hundreds of kilometers.” Her team’s work underscores the power of modern computational geoscience in peering where direct observation is impossible.
Beyond scientific insight, this study holds significant implications for the diamond industry and economic geology. Understanding the precise volatile conditions that permit kimberlite eruptions not only informs exploration strategies in ancient cratonic regions but may also aid in identifying potential new diamondiferous kimberlite pipes. The ability to predict eruption potential on a geochemical basis represents an invaluable tool for resource assessment and extraction efficiency.
As this research continues to inspire new inquiries, the frontier of deep Earth exploration grows ever more accessible—not through drilling or physical excavation, but through the virtual laboratory of atomic-scale simulations. The fusion of geochemistry, physics, and advanced computing is transforming our understanding of how some of Earth’s rarest treasures find their way to the surface, unraveling enigmas that have captivated scientists and enthusiasts for generations.
Subject of Research: Kimberlite melt buoyancy and magma ascent mechanisms driven by volatile compounds, with implications for diamond transport from Earth’s mantle to the surface.
Article Title: Buoyancy of volatile-rich kimberlite melts, magma ascent, and xenolith transport
News Publication Date: 21-Aug-2025
Web References:
References:
Ana Anzulović, Anne H. Davis, Carmen Gaina, and Razvan Caracas, Geology, 2025.
Keywords: Kimberlite, magma ascent, volatile compounds, carbon dioxide, water, mantle, xenolith transport, diamond formation, molecular dynamics simulation, mantle geochemistry.
