Carbonatites and alkaline rocks

Carbonatites are igneous rocks composed of more than 50 weight percent calcium carbonate. Study of the geological record is revealing that carbonatites are more common than previously expected.

Carbonatite magmas that intrude Earth’s crust often form large mineral deposits, such as:

  • Magnet Cove, Arkansas
  • Phalaborwa, South Africa
  • Jacupiranga, Brazil
  • Kovdor, Russia

Most carbonatites are found as rocks that erupted or intruded millions or billions of years in the past. They are often associated spatially and temporally with alkaline igneous rocks.

Carbonatite magmas that erupt at the surface can be explosive, carrying with them fragments of rock from deep within the Earth. These mantle xenoliths reveal more about the origins of carbonatite magmas and processes occurring in the mantle.

Actively forming carbonatites are rare. The only known volcano on Earth that erupts carbonatite magmas is Ol Doinyo Lengai in Tanzania. 

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Glossary

Carbonatite
Carbonatites are rare igneous rocks composed of 50% calcium carbonate. Carbonatites are economically important as they often have high concentrations of rare elements.