The Fascinating World of Kimberlites

Kimberlites are volcanic pipes with a carrot-like shape that emerge from the Earth’s mantle at depths exceeding 150 kilometers. These geological phenomena are among the most intriguing for scientists, offering a unique window into the Earth’s depths. As the molten material ascends rapidly through the mantle and crust, it captures fragments of the rocks it passes, allowing the study of these deep-earth rock samples.

Challenges in Studying Kimberlites

Despite significant interest and numerous studies on kimberlites, they remain largely mysterious rocks. Researcher Anna Anzulovich, a research fellow at the University of Oslo, describes this mystery: “They are very interesting rocks, and despite being well-studied, they are still extremely enigmatic.”

In a recent study published in the Journal of Geology, Anzulovich and her colleagues made significant progress in unraveling the mystery of these rocks. They modeled how volatile compounds like carbon dioxide and water affect the relative buoyancy of the initial kimberlite melt compared to surrounding materials, enabling them to measure what is required for a kimberlite eruption to occur.

Kimberlites and Diamonds

Diamonds reach the surface through kimberlites due to their rapid ascent, preventing them from transforming into graphite, which is more stable under lower pressures and temperatures. However, the original composition of the kimberlite melt and how it ascends so quickly remains a puzzling mystery.

Anzulovich notes that “it starts with something we cannot measure directly,” making it extremely challenging to determine the composition of the original melt, or what is known as the parental melt. Almost all knowledge comes from the heavily altered rocks that form eventually.

Experiments on Jericho Kimberlite

The team focused their study on the Jericho kimberlite, which erupted in the Slave Craton in northwest Canada. Using chemical modeling, they tested different mixtures of carbon dioxide and water. The idea was to create a chemical model of the kimberlite and alter the proportions of carbon dioxide and water to observe their effects.

The experiments showed that Jericho kimberlite requires at least 8.2% carbon dioxide to successfully erupt. Without this gas, the diamonds remain trapped in the mantle.

Conclusion

This study highlights the critical role of volatile compounds in kimberlite eruptions, revealing how water and carbon dioxide influence the movement of the melt. Through these findings, scientists can gain a better understanding of the geological processes occurring deep within the Earth and how kimberlites ascend at such high speeds. This understanding can enhance diamond exploration techniques and provide insights into the planet’s geological history.