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What Is Carbonatite?

Andrew Kirmayer
Andrew Kirmayer

Carbonatite is a form of volcanic rock that typically has various minerals embedded within it. Similar to carbonates usually found in the ocean, it can often be spotted in mid-continental seismic zones such as the Great Rift Valley in Africa or the state of Nevada in the United States. Minerals such as iron, barium, calcite, and dolomite are often seen in carbonatite. Small amounts of uranium, titanium, or phosphorus are sometimes contained within it as well.

Lava that flows out onto the surface or molten rock that intrudes into materials underground can form carbonatite. Structures in the ground, such as dikes or sills, which typically solidify as molten rock passes up through older rock layers, often feature carbonatite as well. The volcanic rocks were once thought to be rare, but research has shown that they often form and then wear away once in contact with the atmosphere. Extrusive igneous rocks, which typically erupt or flow onto the surface, can contain carbonatite. These typically melt at relatively low temperatures or become a powder-like material that gets blown away by the wind or washed away by rain or flowing water.

Carbonatite can form from lava that flows onto the Earth's surface during a volcanic eruption.
Carbonatite can form from lava that flows onto the Earth's surface during a volcanic eruption.

Mining operations are often conducted in open pits to get to carbonatite. Minerals contained in the rock as well as others sometimes found nearby are often considered desirable in many industries. In addition to health hazards from dust, acids, or some metals, deposits can include radioactive compounds like uranium or thorium. Chemicals and waste products often used in the process can collect in waste dumps or leak into groundwater, and sometimes become health hazards as well.

Some carbonatite deposits are thought to have formed relatively recently, but they can also be associated with most stages of the Earth’s history. They are typically seen in various types of landscapes, from mountainous terrain to ground that is relatively flat. Also found in land where there are no faults or other types of shear zones, these rock deposits can be located by tracing calcite-rich substances that travel in flowing ground water.

Magnetic as well as gravitational differences may be detected in rock that contains carbonatite deposits. In addition to Africa and the United States, these volcanic rocks are often found in Canada, Brazil, Russia, and India. They are generally associated with specific rock formations in Australia, Norway, and Spain as well. Active carbonite volcanoes are rare, while older ones are sometimes found in geologically active, mid-continental regions.

Frequently Asked Questions

What is carbonatite and how is it formed?

Carbonatite is a rare igneous rock composed predominantly of carbonate minerals, typically formed from the melting of carbon-bearing mantle rocks under lower pressure and temperature conditions than typical for silicate magmas. This process often occurs in continental rift environments, where the Earth's crust is being pulled apart.

Where can carbonatite be found?

Carbonatite occurrences are globally distributed but are relatively rare. Notable locations include the African Rift Valley, with the famous Oldoinyo Lengai volcano in Tanzania, which is the only active carbonatite volcano. Other significant deposits have been found in Canada, Brazil, and Russia, often associated with alkaline igneous complexes.

Why is carbonatite economically important?

Carbonatite is economically significant due to its enrichment in rare earth elements (REEs) and other valuable minerals like niobium and phosphate. These elements are crucial for modern technologies, including smartphones, wind turbines, and electric vehicles. For instance, the Bayan Obo mine in China, a carbonatite-related deposit, is the world's largest source of REEs.

What minerals are typically found in carbonatite?

Carbonatite is primarily composed of carbonate minerals such as calcite, dolomite, and ankerite. Additionally, it may contain minerals like apatite, magnetite, barite, and various rare earth minerals. The exact mineral composition can vary widely between different carbonatite deposits, reflecting the unique geochemical environment of their formation.

How does carbonatite relate to diamond formation?

While carbonatite itself is not a source of diamonds, its formation is sometimes linked to kimberlite, which can contain diamonds. Both rock types can originate from deep within the Earth's mantle and may be emplaced through similar tectonic processes. Kimberlite pipes, which transport diamonds to the surface, are occasionally found near carbonatite complexes.

Can carbonatite affect global climate?

Carbonatite can indirectly affect global climate through its role in the carbon cycle. The release of carbon dioxide (CO2) during the formation and weathering of carbonatite can contribute to atmospheric CO2 levels. However, this is a natural process that occurs over geological timescales and is not a major driver of current climate change.

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    • Carbonatite can form from lava that flows onto the Earth's surface during a volcanic eruption.
      By: R. Sueswit Apriliant
      Carbonatite can form from lava that flows onto the Earth's surface during a volcanic eruption.