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Phonolite is an uncommon shallow intrusive or extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a variation of the igneous rock trachyte that contains nepheline or leucite rather than quartz. It has an unusually high (12% or more) Na2O + K2O content, defining its position in the TAS classification of igneous rocks. Its coarse grained (phaneritic) intrusive equivalent is nepheline syenite. Phonolite is typically fine grained and compact. The name phonolite comes from the Ancient Greek meaning "sounding stone" due to the metallic sound it produces if an unfractured plate is hit; hence, the English name clinkstone is given as a synonym.
Volcanic rocks are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks. For these reasons, in geology, volcanics and shallow hypabyssal rocks are not always treated as distinct. In the context of Precambrian shield geology, the term "volcanic" is often applied to what are strictly metavolcanic rocks. Volcanic rocks and sediment that form from magma erupted into the air are called "pyroclastics," and these are also technically sedimentary rocks.
The Richat Structure, or Guelb er Richât, is a prominent circular geological feature in the Adrar Plateau of the Sahara. It is located near Ouadane in the Adrar Region of Mauritania. In the local dialect, rīšāt means feathers and it is also known locally in Arabic as tagense, referring to the circular opening of the leather pouch that is used to draw water from local wells.
Nepheline 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. Phonolite is the fine-grained extrusive equivalent.
Phlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates. It is also known as magnesium mica.
Carbonatite is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geochemical verification.
The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma into a more evolved, silica rich end member. Rock types of the tholeiitic magma series include tholeiitic basalt, ferro-basalt, tholeiitic basaltic andesite, tholeiitic andesite, dacite and rhyolite. The variety of basalt in the series was originally called tholeiite but the International Union of Geological Sciences recommends that tholeiitic basalt be used in preference to that term.
A rare-earth mineral contains one or more rare-earth elements as major metal constituents. Rare-earth minerals are usually found in association with alkaline to peralkaline igneous complexes in pegmatites. This would be associated with alkaline magmas or with carbonatite intrusives. Perovskite mineral phases are common hosts to rare-earth elements within the alkaline complexes. Minerals are the solid composer of inorganic substances. They are formed through the atomic movement of fluid which can be derived from evaporation, pressure or any physical change. They are mostly determined through their atomic weight. The minerals that are known as 'rare' earth minerals are considered rare due to their unique geochemical makeup and properties. These substances are not normally found in mining affiliated clusters. Thus an indication of these minerals being short in supply and allocated their title as 'rare' earth minerals. Many rare-earth minerals include rare-earth elements which thus hold the same significant purpose of rare-earth minerals. Earth's rare minerals have a wide range of purposes, including defense technologies and day-to-day uses. This would be associated with alkaline magmas or with carbonatite intrusives. Perovskite mineral phases are common hosts to rare-earth elements within the alkaline complexes. Mantle-derived carbonate melts are also carriers of the rare earths. Hydrothermal deposits associated with alkaline magmatism contain a variety of rare-earth minerals. Rare-earth minerals are usually found in association with alkaline to peralkaline igneous complexes in pegmatites.
Larvikite is an igneous rock, specifically a variety of monzonite, notable for the presence of thumbnail-sized crystals of feldspar. These feldspars are known as ternary because they contain significant components of all three endmember feldspars. The feldspar has partly unmixed on the micro-scale to form a perthite, and the presence of the alternating alkali feldspar and plagioclase layers give its characteristic silver-blue schiller effect on polished surfaces. Olivine can be present along with apatite, and locally quartz. Larvikite is usually rich in titanium, with titanaugite and/or titanomagnetite present.
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.
Sovite is the coarse-grained variety of carbonatite, an intrusive, igneous rock. The fine-grained variety of carbonatite 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, biotite, pyrite, pyrochlore and fluorite.
Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.
Banalsite is a rare barium, sodium aluminium silicate mineral with formula: BaNa2Al4Si4O16. Banalsite is a tectosilicate of the feldspar group.
Rutan Hill is the local name for a hill on the United States Geological Survey Branchville 7.5-minute map. It is located about 2.46 miles (3.96 km) south-southwest of Colesville, New Jersey in Wantage Township, of Sussex County, New Jersey in the United States. Rutan Hill rises about 270 feet (82 m) above the adjacent creek valley to an elevation of just over 1,020 feet (310 m). This hill lies entirely within private, posted property. This nondescript hill is the surface expression of a diatreme that is the northern part of the Late Ordovician Beemerville Alkaline Complex.
Fenite is a metasomatic alteration associated particularly with carbonatite intrusions and created, very rarely, by advanced carbon dioxide alteration (carbonation) of felsic and mafic rocks. It is characterised by the presence of alkali feldspar, sodic pyroxene and sodic amphibole. Fenite alteration is known, but restricted in distribution, around high-temperature metamorphic talc carbonates, generally in the form of an aureole around ultramafic rocks. Such examples include biotite-rich zones, amphibolite-calcite-scapolite alteration and other unusual skarn assemblages. The process is called fenitization.
The geology of Finland is made up of a mix of geologically very young and very old materials. Common rock types are orthogneiss, granite, metavolcanics and metasedimentary rocks. On top of these lies a widespread thin layer of unconsolidated deposits formed in connection to the Quaternary ice ages, for example eskers, till and marine clay. The topographic relief is rather subdued because mountain massifs were worn down to a peneplain long ago.
The Alnö Complex or Alnö Alkaline Complex is a group of carbonatite and alkaline igneous rocks in Alnö in the eastern coast of central Sweden that intruded the basement in Late Ediacaran times. The Alnö Complex is made up by a series of concentric dykes within a radius of 25 km of a main "central complex" of intrusions. In addition the Alnö Complex proper is surrounded by a 500 to 600 m broad zone of metasomatic rock that was formed by metasomatic alteration of the existing Precambrian migmatite gneiss basement. The specific type of metasomatic rock is referred by some authors as "fenite". The dykes of the complex consist of carbonatite and alkaline rocks such melilite and sövite.
The Kola Alkaline Province or Kola Alkaline Carbonatite Province is a discontiguous group of unusual igneous rocks centered in the Kola Peninsula of Russia and with ouliers in nearby areas of Finland and in Arkhangelsk Oblast across the White Sea. The province is made up of alkaline-ultramafic rock complexes often associated to carbonatites and stand-alone dykes and pipes made up of carbonatites, kimberlites and similar rocks. To this it adds the large nepheline syenite bodies of the Lovozero Massif and the Khibiny Mountains. An estimate puts the total volume of the rocks of the Kola Alkaline Province at 15,000 ±2,700 km3.
Wöhlerite, also known as wöehlerite is a member of the amphibole supergroup, and the wöhlerite subgroup within it. It was named after German chemist Friedrich Wöhler. It was first described by Scheerer in 1843, but the crystal structure was later solved by Mellino & Merlino in 1979. Once approved, it was grandfathered by the IMA.
References
- 1 2 http://www.mindat.org/loc-14357.html Mindat location description
- ↑ Faure, Gunter (2000) Origin of Igneous Rocks, Springer, pp. 319-321 ISBN 3-540-67772-0
59°16′04″N9°16′40″E / 59.2677°N 9.2779°E
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