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Carbonatites are intrusive carbonate-mineral-rich igneous rock structures, many of which contain distinctive abundances of apatite, magnetite, barite, and fluorite, that may contain economic or anomalous concentrations of rare earth elements, phosphorus, niobium, uranium, thorium, copper, iron, titanium, barium, fluorine, zirconium, and other rare or incompatible elements. They may also be sources of mica or vermiculite. Carbonatites may form central plugs within zoned alkalic intrusive complexes, or as dikes, sills, breccias, and veins.
Examples
The only carbonatite volcano known to have erupted in historical time is Ol Doinyo Lengai in Tanzania. It emits the lava with the lowest temperature in the world, at 500-600 degrees Celsius (930-1,100 degrees F).
Deposits exist in
Oka, Quebec; Iron Hill and Gem Park, Colorado;
Magnet Cove, Arkansas; St. Honore, Quebec;
Mountain Pass, California; Phalaborwa, South Africa;
Jacupiranga, Brazil; Kovdor, Russia.
Spatially and (or) genetically related deposit types
Vein deposits of thorium, fluorite, or rare earth elements may be associated with carbonatites.
Carbonatite is typically associated with concentrically zoned complexes of alkaline-igneous rocks, though some deposits may consist of dikes or thick sheets. Associated igneous rocks typically include ijolite, melteigite, pyroxenite, and nepheline syenite. Carbonatites are typically associated with undersaturated igneous rocks that are miaskitic (nearly peralkaline) rather than agpaitic (peralkaline).
References
"Carbonatite Deposits (http://pubs.usgs.gov/of/1995/ofr-95-0831/CHAP6.pdf)." USGS Carbonatite Deposits. Accessed on January 31, 2005.
"DESCRIPTIVE MODEL OF CARBONATITE DEPOSITS (http://pubs.usgs.gov/bul/b1693/html/bull5rsj.htm)." USGS DESCRIPTIVE MODEL OF CARBONATITE DEPOSITS. Accessed on January 31, 2005.
"World's Coolest Lava is in Africa (http://hvo.wr.usgs.gov/volcanowatch/2003/03_04_17.html)." Volcano Watch April 17, 2003. Accessed on January 31, 2005.
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