A groundbreaking study, recently published in Geology, has uncovered the vital role of carbon dioxide in the journey of

diamonds from deep within the Earth’s mantle to the surface. The research, led by Ana Anzulović from the University of

Oslo, explores the complex behavior of kimberlite magma, the rare volcanic rock that carries diamonds.

The Crucial Role of Carbon Dioxide in Kimberlite Magma Ascent

One of the most significant discoveries from this study revolves around the amount of carbon dioxide needed to allow

kimberlite to rise from the depths of the Earth. Ana Anzulović and her team found that a minimum of 8.2% carbon dioxide

is required for kimberlite magma to remain buoyant enough to travel upwards. Without sufficient carbon dioxide, the

magma would become denser than the surrounding rock, causing it to stall before reaching the surface. As Anzulović

explains,

“The most important takeaway from this study is that we managed to constrain the amount of CO2 that you need in the

Jericho kimberlite to successfully ascend through the Slave craton.”

In their simulations, the team modeled various mixtures of water and carbon dioxide to determine how they impacted the

buoyancy of the magma. The results revealed that the presence of these volatile compounds is essential in preventing the

magma from sinking back into the Earth. This finding not only enhances our understanding of diamond transport but also

helps geologists better predict which kimberlite pipes are more likely to contain diamonds, thus improving exploration

strategies.

How Kimberlite Magma Carries Diamonds: The Science Behind the Ascent

Kimberlite magma’s ability to transport diamonds is a result of its unique properties and the conditions under which it

forms. Unlike most volcanic rocks, kimberlite originates from the Earth’s mantle, a vast and extremely hot layer of the

planet beneath the crust. This magma is rich in volatiles, including water and carbon dioxide, which play a critical

role in its behavior as it rises through the crust. The process begins when kimberlite magma starts to melt from the

mantle, carrying with it a variety of materials from deep within the Earth, including diamonds.

In their analysis, Anzulović and her team focused on how the presence of dissolved gases like water and carbon dioxide

affected the magma’s movement. Water helps to lower the viscosity of the magma, allowing it to flow more easily, while

carbon dioxide helps strengthen the magma at greater depths. Together, these gases enable the magma to ascend rapidly,

preventing diamonds from turning into graphite, which is a more stable form of carbon at shallow depths. As the magma

rises and cools quickly upon reaching the surface, it traps the diamonds inside, preserving their structure and allowing

them to be collected in kimberlite pipes.

The Jericho Kimberlite Pipe: A Case Study in Diamond Transport

The Jericho kimberlite pipe in northern Canada provided the perfect case study for this research. Located in the Slave

craton, one of the oldest and most stable parts of Earth’s crust, the Jericho pipe has long been known as a source of

diamonds. The study’s focus on this specific kimberlite allowed the researchers to conduct detailed simulations of how

the magma ascended through the Earth’s crust and carried diamonds along the way. According to Anzulović,

“Our most volatile-rich composition can carry up to 44% of mantle peridotite, for example, to the surface, which is

really an impressive number for such a low viscosity melt.”