Carbonatite

Carbonatites /kɑːrˈbɒnətaɪt/ are intrusive or extrusive igneous rocks defined by mineralogic composition consisting of greater than 50 percent carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification.

Carbonatites usually occur as small plugs within zoned alkalic intrusive complexes, or as dikes, sills, breccias, and veins. They are, almost exclusively, associated with continental rift-related tectonic settings. It seems that there has been a steady increase in the carbonatitic igneous activity through the earth's history, from the Archean Eon to the present.