Carbonatite

Carbonatite

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Carbonatites are intrusive or extrusive igneous rocks
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

 defined by mineralogic composition consisting of greater than 50 percent carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....

 mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

s. Carbonatites may be confused with marble
Marble
Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.Geologists use the term "marble" to refer to metamorphosed limestone; however stonemasons use the term more broadly to encompass unmetamorphosed limestone.Marble is commonly used for...

, and may require geochemical verification.

Carbonatites usually occur as small plug
Volcanic plug
A volcanic plug, also called a volcanic neck or lava neck, is a volcanic landform created when magma hardens within a vent on an active volcano. When forming, a plug can cause an extreme build-up of pressure if volatile-charged magma is trapped beneath it, and this can sometimes lead to an...

s within zoned alkalic intrusive complexes, or as dike
Dike (geology)
A dike or dyke in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across* planar wall rock structures, such as bedding or foliation...

s, sill
Sill (geology)
In geology, a sill is a tabular sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive sheet...

s, breccia
Breccia
Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....

s, and vein
Vein (geology)
In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation...

s. They are, almost exclusively, associated with continental rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....

-related tectonic settings. The majority of carbonatites are Proterozoic
Proterozoic
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...

 or Phanerozoic
Phanerozoic
The Phanerozoic Eon is the current eon in the geologic timescale, and the one during which abundant animal life has existed. It covers roughly 542 million years and goes back to the time when diverse hard-shelled animals first appeared...

 in age. It seems that there has been a steady increase in the carbonatitic igneous activity through the Earth's history, from Archean
Archean
The Archean , also spelled Archeozoic or Archæozoic) is a geologic eon before the Paleoproterozoic Era of the Proterozoic Eon, before 2.5 Ga ago. Instead of being based on stratigraphy, this date is defined chronometrically...

 to present.

Nearly all carbonatite occurrences are intrusives or subvolcanic
Subvolcanic rock
A subvolcanic rock, also known as a hypabyssal rock, is an igneous rock that originates at medium to shallow depths within the crust and contain intermediate grain size and often porphyritic texture. They have textures between volcanic and plutonic rocks. Subvolcanic rocks include diabase and...

 intrusives. This is because carbonatite lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

 flows are unstable and react quickly in the atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

. Carbonatite lavas may not be as uncommon as thought, but have been poorly preserved throughout Earth's history
History of Earth
The history of the Earth describes the most important events and fundamental stages in the development of the planet Earth from its formation 4.578 billion years ago to the present day. Nearly all branches of natural science have contributed to the understanding of the main events of the Earth's...

.

Only one carbonatite volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 is known to have erupted in historical time, Ol Doinyo Lengai
Ol Doinyo Lengai
Ol Doinyo Lengai is an active volcano located in the north of Tanzania and is part of the volcanic system of the Great Rift Valley in Eastern Africa. It is located in the eastern Rift Valley, south of both Lake Natron and Kenya. It is unique among active volcanoes in that it produces...

 in Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...

. It erupted the lowest temperature lava in the world, at 500-600 °C. The lava is natrocarbonatite
Natrocarbonatite
Natrocarbonatite is a rare carbonatite lava which erupts from the Ol Doinyo Lengai volcano in Tanzania within the Great Rift Valley of eastern Africa. Whereas most lavas are rich in silicate minerals, the natrocarbonatite lavas of Ol Doinyo Lengai are rich in the rare sodium and potassium carbonate...

 dominated by nyerereite
Nyerereite
Nyerereite is a very rare sodium calcium carbonate mineral with formula Na2Ca2. It forms colorless, platey pseudohexagonal orthorhombic crystals that are typically twinned. It has a specific gravity of 2.54 and indices of refraction of nα=1.511, nβ=1.533 and nγ=1.535. Nyerereite is not stable in...

 and gregoryite
Gregoryite
Gregoryite is an anhydrous carbonate that is rich in potasium and sodium...

.

Genesis


Carbonatites are rare, peculiar igneous rocks formed by unusual processes and from unusual source rocks. Three models of their formation exist:
  • direct generation by very low degree partial melts in the mantle and melt differentiation
    Igneous differentiation
    In geology, igneous differentiation is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, emplacement or eruption.-Primary melts:...

  • liquid immiscibility between a carbonate melt and a silicate
    Silicate
    A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...

     melt
  • peculiar, extreme crystal fractionation

Evidence for each process exists, but the key is that these are unusual phenomena. Historically, carbonatites were thought to form by melting of limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 or marble
Marble
Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.Geologists use the term "marble" to refer to metamorphosed limestone; however stonemasons use the term more broadly to encompass unmetamorphosed limestone.Marble is commonly used for...

 by intrusion of magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

, however geochemical and mineralogical data discount this.

Mineralogy


Primary mineralogy is highly variable, but may include natrolite
Natrolite
Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula . The type locality is Hohentwiel, Hegau, Germany....

, sodalite
Sodalite
Sodalite is a rich royal blue mineral widely enjoyed as an ornamental gemstone. Although massive sodalite samples are opaque, crystals are usually transparent to translucent...

, apatite
Apatite
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...

, magnetite
Magnetite
Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...

, barite
Barite
Baryte, or barite, is a mineral consisting of barium sulfate. The baryte group consists of baryte, celestine, anglesite and anhydrite. Baryte itself is generally white or colorless, and is the main source of barium...

, fluorite
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...

, ancylite
Ancylite
Ancylite is a group of hydrous strontium carbonate minerals containing cerium, lanthanum and minor amounts of other rare earth elements. The composition is Sr2· with ancylite-Ce enriched in cerium and ancylite-La in lanthanum....

 group minerals, and other rare minerals not found in more common igneous rocks. Recognition of carbonatites may be difficult, especially as their mineralogy and texture may not differ much from marble
Marble
Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.Geologists use the term "marble" to refer to metamorphosed limestone; however stonemasons use the term more broadly to encompass unmetamorphosed limestone.Marble is commonly used for...

 save for the presence of igneous minerals. They may also be sources of mica
Mica
The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition...

 or vermiculite
Vermiculite
Vermiculite is a natural mineral that expands with the application of heat. The expansion process is called exfoliation and it is routinely accomplished in purpose-designed commercial furnaces. Vermiculite is formed by weathering or hydrothermal alteration of biotite or phlogopite...

.

Carbonatites are classed as calcitic
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...

 sovite
Sovite
Sovite is the coarse grained variety or facies of a carbonatite intrusive. The finer grained variety is known as alvikite. The two varieties are distinguished by minor and trace element compositions. Sovite is often a medium to coarse grained calcite rock with variable accessory amphibole,...

 (coarse textured) and alvikite (finer textured) varieties or facies. The two are also distinguished by minor and trace element
Trace element
In analytical chemistry, a trace element is an element in a sample that has an average concentration of less than 100 parts per million measured in atomic count, or less than 100 micrograms per gram....

 composition. The terms rauhaugite and beforsite refer to dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....

 and ankerite
Ankerite
Ankerite is a calcium, iron, magnesium, manganese carbonate mineral of the group of rhombohedral carbonates with formula: Ca2. In composition it is closely related to dolomite, but differs from this in having magnesium replaced by varying amounts of iron and manganese.The crystallographic and...

 rich occurrences respectively. The alkali-carbonatites are termed lengaite. Examples with 50 - 70% carbonate minerals are termed silico-carbonatites. Additionally carbonatites may be either enriched in magnetite
Magnetite
Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...

 and apatite
Apatite
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...

 or rare earth element
Rare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...

s, fluorine
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...

 and barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...

.

Natrocarbonatite
Natrocarbonatite
Natrocarbonatite is a rare carbonatite lava which erupts from the Ol Doinyo Lengai volcano in Tanzania within the Great Rift Valley of eastern Africa. Whereas most lavas are rich in silicate minerals, the natrocarbonatite lavas of Ol Doinyo Lengai are rich in the rare sodium and potassium carbonate...

is made up largely of two minerals, nyerereite (named after Julius Nyerere
Julius Nyerere
Julius Kambarage Nyerere was a Tanzanian politician who served as the first President of Tanzania and previously Tanganyika, from the country's founding in 1961 until his retirement in 1985....

, the first president of independent Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...

) and gregoryite (named after John Walter Gregory
John Walter Gregory
John Walter Gregory, FRS, was a British geologist and explorer, known principally for his work on glacial geology and on the geography and geology of Australia and East Africa.-Early life:...

, one of the first geologists to study the Great Rift Valley
Great Rift Valley
The Great Rift Valley is a name given in the late 19th century by British explorer John Walter Gregory to the continuous geographic trench, approximately in length, that runs from northern Syria in Southwest Asia to central Mozambique in South East Africa...

 and author of the book The Great Rift Valley). These minerals are both carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....

s in which sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 and potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

 are present in significant quantities. Both are anhydrous
Anhydrous
As a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...

 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.

Geochemistry


Carbonatite is composed predominatly of carbonate minerals and extremely unusual in its major element composition as compared to silicate igneous rocks, obviously because it is composed primarily of Na2O and CaO plus CO2.

Most carbonatites tend to include some silicate mineral fraction; by definition an igneous rock containing >50% carbonate minerals is classified as a carbonatite. Silicate minerals associated with such compositions are pyroxene
Pyroxene
The pyroxenes are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. They share a common structure consisting of single chains of silica tetrahedra and they crystallize in the monoclinic and orthorhombic systems...

, olivine
Olivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....

, and silica-undersaturated minerals such as nepheline
Nepheline
Nepheline, also called nephelite , is a feldspathoid: a silica-undersaturated aluminosilicate, Na3KAl4Si4O16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatites...

 and other feldspathoid
Feldspathoid
The feldspathoids are a group of tectosilicate minerals which resemble feldspars but have a different structure and much lower silica content. They occur in rare and unusual types of igneous rocks....

s.

Geochemically, carbonatites are dominated by incompatible elements (Ba, Cs, Rb) and depletions in compatible elements (Hf, Zr, Ti). This together with their silica-undersaturated composition supports inferences that carbonatites are formed by low degrees of partial melting
Partial melting
Partial melting occurs when only a portion of a solid is melted. For mixed substances, such as a rock containing several different minerals or a mineral that displays solid solution, this melt can be different from the bulk composition of the solid....

.

A specific type of hydrothermal alteration termed fenitization is typically associated with carbonatite intrusions. This alteration assemblage produces a unique rock mineralogy termed a fenite after its type locality, the Fen complex
Fen Complex, Norway
The Fen complex in Nome, Telemark, Norway is a region noted for an unusual suite of igneous rocks. Several varieties of carbonatite are present in the area as well as lamprophyre, ijolite and other highly alkalic rocks...

 in Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

. The alteration consists of metasomatic
Metasomatism
Metasomatism is the chemical alteration of a rock by hydrothermal and other fluids.Metasomatism can occur via the action of hydrothermal fluids from an igneous or metamorphic source. In the igneous environment, metasomatism creates skarns, greisen, and may affect hornfels in the contact...

 halos consisting of sodium rich silicates arfvedsonite
Arfvedsonite
Arfvedsonite is a sodium amphibole mineral with composition: [Na][Na2][4Fe3+][2|Si8O22]. It crystallizes in the monoclinic prismatic crystal system and typically occurs as greenish black to bluish grey fibrous to radiating or stellate prisms....

, barkevikite and glaucophane
Glaucophane
Glaucophane is a mineral belonging to the amphibole group, chemical formula []Na2]Mg3Al2][2|Si8O22].-Name:It is named from its typical blue color . Glaucophane crystallizes in the monoclinic system....

 along with phosphates, hematite
Hematite
Hematite, also spelled as haematite, is the mineral form of iron oxide , one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum...

 and other iron and titanium oxides.

Occurrence


Associated igneous rocks typically include ijolite
Ijolite
Ijolite , is an igneous rock consisting essentially of nepheline and augite. Ijolite is a rare rock type of considerable importance from a mineralogical and petrological standpoint...

, melteigite, teschenite, lamprophyre
Lamprophyre
Lamprophyres are uncommon, small volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks and small intrusions...

s, phonolite
Phonolite
Phonolite is a rare igneous, volcanic rock of intermediate composition, with aphanitic to porphyritic texture....

, foyaite, shonkinite
Shonkinite
Shonkinite is a mafic foidal syenite, an intrusive, holocrystalline rock which in the restricted sense is composed of potassic feldspar in the form of sanidine, nepheline, augite, biotite, and olivine. Shonkinite is also used for mafic nepheline syenite with aegerine-augite as the pyroxene, and...

, silica undersaturated foid-bearing pyroxenite
Pyroxenite
Pyroxenite is an ultramafic igneous rock consisting essentially of minerals of the pyroxene group, such as augite and diopside, hypersthene, bronzite or enstatite. They are classified into clinopyroxenites, orthopyroxenites, and the websterites which contain both pyroxenes...

 (essexite
Essexite
Essexite , also called nepheline monzogabbro , is a dark gray or black holocrystalline plutonic igneous rock. Its name is derived from the type locality in Essex County, MA.Modern petrology identifies rocks according to mineralogical criteria...

), and nepheline syenite
Nepheline syenite
Nephelene syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varieties are also known...

.

Carbonatites are typically associated with undersaturated (low silica) igneous rocks that are either alkali (Na2O and K2O), ferric iron (Fe2O3) and zirconium
Zirconium
Zirconium is a chemical element with the symbol Zr and atomic number 40. The name of zirconium is taken from the mineral zircon. Its atomic mass is 91.224. It is a lustrous, grey-white, strong transition metal that resembles titanium...

-rich agpaitic rocks or alkali-poor, FeO-CaO-MgO-rich and zirconium-poor miaskitic rocks.

The Mount Weld
Mount Weld
Mount Weld is a mountain and a mine site in Western Australia, located about 30 km south of Laverton and 120 km east of Leonora. It ranks as one of the richest major rare earth deposits in the world....

 carbonatite is unassociated with a belt or suite of alkaline igneous rocks, although calc-alkaline magmas are known in the region. The genesis of this Archaean carbonatite remains contentious as it is the sole example of an Archaean carbonatite in Australia.

Intrusive morphology


Carbonatite is known to form in association with concentrically zoned complexes of alkaline-igneous rocks, the typical example of this being Phalaborwa, South Africa.

Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

an carbonatites take the form of sills, lopolith
Lopolith
A lopolith is a large igneous intrusion which is lenticular in shape with a depressed central region. Lopoliths are generally concordant with the intruded strata with dike or funnel-shaped feeder bodies below the body...

s and rare dikes are reported in the Guyana Shield.

The Mud Tank and Mount Weld carbonatites take the form of multi-stage cylindrical intrusive bodies with several distinct phases of carbonatite intrusion. Smaller carbonatite sills and dikes are present in other Proterozoic
Proterozoic
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...

 mobile belts in Australia, typically as dikes and discontinuous pods.

Known examples


Dozens of carbonatites are known including Oka
Oka, Quebec
-References:...

 and St. Honore, Quebec; Gem Park and Iron Hill, Colorado; Magnet Cove igneous complex
Magnet Cove igneous complex
The Magnet Cove igneous complex is a small alkalic ring complex lying to the west of the town of Magnet Cove in Hot Spring County, Arkansas. It and the adjacent town are so named due to the existence of magnetite and the terrain being a cove, a basin-shaped valley.The complex is of Mesozoic age,...

, Arkansas
Arkansas
Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...

;
Mountain Pass, California
Mountain Pass rare earth mine
The Mountain Pass rare earth mine is an open-pit mine of rare earth elements on the south flank of the Clark Mountain Range and just north of the unincorporated community of Mountain Pass, California, United States. The mine, owned by Molycorp Inc., once supplied most of the world's rare earth...

; the Palabora Complex near Phalaborwa
Phalaborwa
Phalaborwa is a town situated in the Mopani district, halfway up along the length of the Kruger National Park in the Limpopo province in South Africa. The Lowveld, also known as Valley of the Olifants, has the highest winter temperatures in South Africa. The rainfall is low and the average winter...

, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

;
Jacupiranga
Jacupiranga
Jacupiranga is a municipality in the state of São Paulo in Brazil. The population in 2004 is 18,380 and the area is 709.98 km². The elevation is 33 m. This place name comes from the Tupi language.-External links:**...

, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

; Ayopaya, Bolivia; Kovdor
Kovdor
Kovdor is a town and the administrative center of Kovdorsky District of Murmansk Oblast, Russia, mostly known by its mining industry. Population: -Economy:...

, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, from India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

; the Mud Tank
Mud tank
A mud tank is an open-top container, typically made of steel, to store drilling fluid on a drilling rig. They are also called mud pits, because they used to be nothing more than pits dug out of the earth....

 and Mount Weld
Mount Weld
Mount Weld is a mountain and a mine site in Western Australia, located about 30 km south of Laverton and 120 km east of Leonora. It ranks as one of the richest major rare earth deposits in the world....

, Australia; the Fen Complex, Norway
Fen Complex, Norway
The Fen complex in Nome, Telemark, Norway is a region noted for an unusual suite of igneous rocks. Several varieties of carbonatite are present in the area as well as lamprophyre, ijolite and other highly alkalic rocks...

; the Basal Complex of Fuerteventura
Fuerteventura
Fuerteventura , a Spanish island, is one of the Canary Islands, in the Atlantic Ocean off the coast of Africa. It is situated at 28°20' north, 14°00' west. At 1,660 km² it is the second largest of the Canary Islands, after Tenerife...

, Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

.

The Ol Doinyo Lengai
Ol Doinyo Lengai
Ol Doinyo Lengai is an active volcano located in the north of Tanzania and is part of the volcanic system of the Great Rift Valley in Eastern Africa. It is located in the eastern Rift Valley, south of both Lake Natron and Kenya. It is unique among active volcanoes in that it produces...

 volcano, in the Great Rift Valley
Great Rift Valley
The Great Rift Valley is a name given in the late 19th century by British explorer John Walter Gregory to the continuous geographic trench, approximately in length, that runs from northern Syria in Southwest Asia to central Mozambique in South East Africa...

, Africa, is the world's only active carbonatite volcano. Other older carbonatite volcanoes are located in the same region, including Homa Mountain.

Economic importance


Carbonatites may contain economic or anomalous concentrations of rare earth
Rare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...

 elements, phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

, niobium
Niobium
Niobium or columbium , is a chemical element with the symbol Nb and atomic number 41. It's a soft, grey, ductile transition metal, which is often found in the pyrochlore mineral, the main commercial source for niobium, and columbite...

 - tantalum
Tantalum
Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as tantalium, the name comes from Tantalus, a character in Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion resistant. It is part of the refractory...

, uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

, thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....

, copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

, iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

, titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....

, vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...

, barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...

, fluorine
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...

, zirconium
Zirconium
Zirconium is a chemical element with the symbol Zr and atomic number 40. The name of zirconium is taken from the mineral zircon. Its atomic mass is 91.224. It is a lustrous, grey-white, strong transition metal that resembles titanium...

, and other rare or incompatible elements. Apatite
Apatite
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...

, barite
Barite
Baryte, or barite, is a mineral consisting of barium sulfate. The baryte group consists of baryte, celestine, anglesite and anhydrite. Baryte itself is generally white or colorless, and is the main source of barium...

 and vermiculite
Vermiculite
Vermiculite is a natural mineral that expands with the application of heat. The expansion process is called exfoliation and it is routinely accomplished in purpose-designed commercial furnaces. Vermiculite is formed by weathering or hydrothermal alteration of biotite or phlogopite...

 are among the industrially important minerals associated with some carbonatites.

Vein deposits of thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....

, fluorite
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...

, or rare earth
Rare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...

 elements may be associated with carbonatites, and may be hosted internal to or within the metasomatized
Metasomatism
Metasomatism is the chemical alteration of a rock by hydrothermal and other fluids.Metasomatism can occur via the action of hydrothermal fluids from an igneous or metamorphic source. In the igneous environment, metasomatism creates skarns, greisen, and may affect hornfels in the contact...

 aureole of a carbonatite.

As an example the Palabora complex of South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

 has produced significant copper (as chalcopyrite
Chalcopyrite
Chalcopyrite is a copper iron sulfide mineral that crystallizes in the tetragonal system. It has the chemical composition CuFeS2. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green tinged black.On exposure to air, chalcopyrite...

, bornite
Bornite
Bornite is a sulfide mineral with chemical composition Cu5FeS4 that crystallizes in the orthorhombic system .-Appearance:Bornite has a brown to copper-red color on fresh surfaces that tarnishes to various iridescent shades of blue to purple in places...

 and chalcocite
Chalcocite
Chalcocite, copper sulfide , is an important copper ore mineral. It is opaque, being colored dark-gray to black with a metallic luster. It has a hardness of 2½ - 3. It is a sulfide with an orthorhombic crystal system....

), apatite, vermiculte along with lesser magnetite, linnaeite
Linnaeite
Linnaeite is a cobalt sulfide mineral with the composition Co+2Co+32S4 . It was discovered in 1845 in Västmanland, Sweden, and was named to honor Carl Linnaeus ....

 (cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....

), baddeleyite
Baddeleyite
Baddeleyite is a rare zirconium oxide mineral , occurring in a variety of monoclinic prismatic crystal forms. It is transparent to translucent, has high indices of refraction, and ranges from colorless to yellow, green, and dark brown. Baddeleyite is a refractory mineral, with a melting point of...

 (zirconium-hafnium), and by-product gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

, silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

, nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

 and platinum
Platinum
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...

.

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