NationMaster - Encyclopedia: Carbonatites

Carbonatites are intrusive igneous rocks defined by a mineralogy which is greater than than 50% carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification. Pluton redirects here. ... Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Sedimentary, volcanic, plutonic, metamorphic rock types of North America. ... Carbonate is an anion with a charge of -2 and an empirical formula of CO32-. For an aqueous solution, carbonate exists in three forms. ... Marble For the glass spheres, see marbles. ...

Carbonatites are usually intrusions with central plugs within zoned alkalic intrusive complexes, or as dikes, sills, breccias, and veins. The majority of carbonatites are Proterozoic in age, and hosted in Proterozoic fold belts adjacent to Archaean cratons. A dike in geology refers to a tabular intrusive igneous body. ... In geology, a sill is a tabular, often horizontal mass of igneous rock that has been intruded laterally between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. ... Breccia, derived from the Latin word for broken, is a sedimentary rock composed of angular fragments in a matrix that may be of a similar or a different material. ... A lode is the metalliferous ore that fills a fissure in a rock or a vein of ore deposited between layers of rock. ... In geology, the Proterozoic is an eon prior to the first abundant complex life on earth. ... The Archean is a geologic eon; it is a somewhat antiquated term for the time span between 2500 million years before the present and 3800 million years before the present. ... A craton is an old and stable part of the continental crust that has survived the merging and splitting of continents and supercontinents for at least 500 million years. ...

Nearly all carbonatite occurrences are intrusives or subvolcanic intrusives. This is because carbonatite lava flows are unstable and react quickly in the atmosphere. Carbonatite lavas may not be as uncommon as thought, but have been poorly preserved throughout Earth's history.

Only one carbonatite volcano is known to have erupted in historical time, Ol Doinyo Lengai in Tanzania. It erupted the lowest temperature lava in the world, at 500-600 °C (930-1,100 °F). The lava is dominated by natrolite and trona, sodic calcite. Ol Doinyo Lengai is a volcano located in Tanzania. ... Look up lava, Aa, and pahoehoe in Wiktionary, the free dictionary. ... Natrolite is a mineral species belonging to the zeolite group. ... Trona, hydrated sodium bicarbonate carbonate (Na3HCO3CO3·2H2O), is an evaporite mineral. ...

Genesis

Carbonatites are rare, peculiar igneous rocks formed by unusual processes and from unusual source rocks. Three models of their formation exist:

Evidence for each process exists, but the key is that these are unusual phenomenon. Historically, carbonatites were thought to form by melting of limestone or marble by intrusion of magma, however geochemical and mineralogical data discount this. Earth cutaway from core to exosphere. ... In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. ... Limey shale overlaid by limestone. ... Marble For the glass spheres, see marbles. ... Magma is molten rock often located inside a magma chamber beneath the surface of the Earth. ...

Mineralogy

Primary mineralogy is highly variable, but may include natrolite, sodalite, sovite, apatite, magnetite, barite, fluorite, ancylite group minerals, and other rare, peculiar minerals not found in more normal igneous rocks. Recognition of carbonatites may be difficult, especially as their mineralogy and texture may not differ much from marble save for the presence of igneous minerals. They may also be sources of mica or vermiculite. Natrolite is a mineral species belonging to the zeolite group. ... Sodalite is a rare, rich royal blue mineral widely enjoyed as an ornamental stone. ... Apatite is a group of phosphate minerals, usually referring to: hydroxylapatite, fluorapatite, and chlorapatite, named for high concentrations of OH-, F-, or Cl- ions, respectively, in the crystal lattice. ... Magnetite is a ferromagnetic mineral form of iron(II,III) oxide, with chemical formula , one of several iron oxides and a member of the spinel group. ... Baryte with Cerussite from Morocco Baryte with Galena and Hematite from Poland Barite (BaSO4) is a mineral consisting of barium sulfate. ... Fluorite (also called fluor-spar) is a mineral composed of calcium fluoride, CaF2. ... Marble For the glass spheres, see marbles. ... rock with mica Mica sheet mica flakes The mica group of minerals includes several closely related materials having highly perfect basal cleavage. ... Vermiculite is a natural mineral which expands with the application of heat. ...

Natrocarbonatite is made up largely of two minerals, nyerereite (named after Julius Nyerere, the first president of independent Tanzania) and gregoryite (named after John Walter Gregory, one of the first geologists to study the Great Rift Valley and author of the book The Great Rift Valley). These minerals are both carbonates in which sodium and potassium are present in significant quantities. Both are anhydrous and when they come into contact with the moisture of the atmosphere, they begin to react extremely quickly. The black or dark brown lava and ash erupted begins to turn white within a few hours. To meet Wikipedias quality standards, this article or section may require cleanup. ... Northern section of the Great Rift Valley. ... Carbonate is an anion with a charge of -2 and an empirical formula of CO32-. For an aqueous solution, carbonate exists in three forms. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ... An ionic crystal is said to be anhydrous if it contains no water. ...

Geochemistry

Carbonatites 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. Geochemically, carbonatites are dominated by incompatible elements (Ba, Cs, Rb) and depletions in compatible elements (Hf, Zr, Ti). A rare earth is an oxide of a rare earth element. ... This article is about the chemical element. ... General Name, Symbol, Number niobium, Nb, 41 Chemical series transition metals Group, Period, Block 5, 5, d Appearance gray metallic Atomic mass 92. ... General Name, Symbol, Number uranium, U, 92 Chemical series actinides Group, Period, Block n/a, 7, f Appearance silvery gray metallic; corrodes to a spalling black oxide coat in air Atomic mass 238. ... General Name, Symbol, Number thorium, Th, 90 Chemical series Actinides Group, Period, Block n/a, 7, f Appearance silvery white Atomic mass 232. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic brown Atomic mass 63. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Appearance silvery metallic Atomic mass 47. ... General Name, Symbol, Number barium, Ba, 56 Chemical series alkaline earth metals Group, Period, Block 2, 6, s Appearance silvery white Atomic mass 137. ... General Name, Symbol, Number fluorine, F, 9 Chemical series halogens Group, Period, Block 17, 2, p Appearance pale greenish-yellow gas Atomic mass 18. ... General Name, Symbol, Number zirconium, Zr, 40 Chemical series transition metals Group, Period, Block 4, 5, d Appearance silvery white Atomic mass 91. ...

Examples

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, India; Mount Weld, Mud Tank Australia.

Oka may refer to: (cars) Oka is the name of a car produced by Lada (named after the river). ... Motto: Je me souviens (French: I remember) Official languages French Capital Quebec City Largest city Montreal Lieutenant-Governor Lise Thibault Premier Jean Charest (PLQ) Parliamentary representation - House seat - Senate seats 75 24 Area Total â€¢ Land â€¢ Water (% of total) Ranked 2nd 1,542,056 kmÂ² 1,183,128 kmÂ² 176,928... Official language(s) English Capital Denver Largest city Denver Area - Total - Width - Length - % water - Latitude - Longitude Ranked 8th 269 837 kmÂ² 451 km 612 km 0. ... Official language(s) English Capital Little Rock Largest city Little Rock Area - Total - Width - Length - % water - Latitude - Longitude Ranked 29th 137 732 kmÂ² 385 km 420 km 2. ... Motto: Je me souviens (French: I remember) Official languages French Capital Quebec City Largest city Montreal Lieutenant-Governor Lise Thibault Premier Jean Charest (PLQ) Parliamentary representation - House seat - Senate seats 75 24 Area Total â€¢ Land â€¢ Water (% of total) Ranked 2nd 1,542,056 kmÂ² 1,183,128 kmÂ² 176,928... Official language(s) English Capital Sacramento Largest city Los Angeles Area - Total - Width - Length - % water - Latitude - Longitude Ranked 3rd 410,000 kmÂ² 402. ... Phalaborwa is a large town situated at half way up along the length of the Kruger National Park in Limpopo Province of South Africa. ... Jacupiranga is a municipality in the state of São Paulo in Brazil. ...

Spatially and (or) genetically related deposit types

Vein deposits of thorium, fluorite, or rare earth elements may be associated with carbonatites. General Name, Symbol, Number thorium, Th, 90 Chemical series Actinides Group, Period, Block n/a, 7, f Appearance silvery white Atomic mass 232. ... Fluorite (also called fluor-spar) is a mineral composed of calcium fluoride, CaF2. ... A rare earth is an oxide of a rare earth element. ...

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, teschenite, lamprophyres, phonolite, foyaite, shonkinite, pyroxenite (essexite), and nepheline syenite. Carbonatites are typically associated with undersaturated igneous rocks that are miaskitic (nearly peralkaline) rather than agpaitic (peralkaline). Ijolite (derived from the first syllable of the Finnish words Ji-waru, Jijoki, &c. ... Lamprophyres (Greek Lampros, bright, and the terminal part of the word porphyry, meaning rocks containing bright porphyritic crystals) are a group of rocks containing phenocrysts, usually of biotite and hornblende (with bright cleavage surfaces), often also of olivine and augite, but not of feldspar. ... Phonolite is an igneous, volcanic (extrusive) rock, of felsic composition, with aphanitic to porphyritic texture. ... Pyroxenite is a rock consisting essentially of minerals of the pyroxene group, such as augite and diallage, hypersthene, bronzite or enstatite. ... Essexite is a dark gray or black igneous rock. ... Nepheline syenite is a coarse crystalline igneous rock composed primarily of orthoclase alkali-feldspars, nepheline and mafic minerals such as the sodium rich pyroxenes and amphiboles. ...

References

Categories: Igneous rocks | Volcanology | Petrology | Mineral stubs The United States Geological Survey (USGS) is a scientific agency of the United States government. ... January 31 is the 31st day of the year in the Gregorian calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... January 31 is the 31st day of the year in the Gregorian calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... April 17 is the 107th day of the year in the Gregorian calendar (108th in leap years). ... 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... January 31 is the 31st day of the year in the Gregorian calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...

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