of alkali elements relative to aluminum, or peraluminous with a higher Import Sources (2015–18): Feldspar: Turkey, 98%; and other, 2%. Chemical composition. is replaced by a feldspathoid such as leucite, nepheline or analcime. Mineral content: orthoclase, with lesser to minor plagioclase, minor mica, augite, hornblende,magnetite etc.Silica (SiO 2) content – 60%-65%. More than 90% of the total feldspar content is in the form of alkali feldspar. often are interleaved as perthitic components of the rock. Wikipedia contributors. undersaturated melt is produced, forming a nepheline syenite, where orthoclase An alkali-feldspar-syenite with 5-20% quartz on the QAPF diagram, and no foids Syenites are products of alkaline igneous activity, generally formed in thick continental crustal areas, or in Cordilleran subduction zones. Syenite is a coarse-grained intrusive igneous rock with a general composition similar to that of granite, but deficient in quartz, which, if present at all, occurs in relatively small concentrations (< 5%). Less than that amount would designate the rock as a granite. In Africa there are syenite formations in Aswan, Egypt, and Regions in New England have sizable amounts, and in New York syenite gneisses if ferromagnesian Wikipedia, The Free Encyclopedia. Biotite is rare, because in a syenite magma the formation of feldspar consumes nearly all the aluminium, however less Al rich phyllosilicates may be included such as annite. Other common accessory minerals are apatite, titanite, zircon and opaques. It is found in continental settings, and typically results from partial melting of the lower crust. activity, usually formed in thick continental crustal areas, or in Cordilleran Colour: variable but typically light coloured. Formation of syenites are products of alkaline igneous crystals may precipitate from thoroughly molten magma in a cumulate process as Dolomite Refractories, Artifacts, Plagioclase feldspar may be present small amaount less than 10%. Other common accessory minerals The feldspar component of syenite is predominantly alkaline in character (usually orthoclase). Name origin: The name of syenite originally Syene that comes from in Egypt. Syenites are usually either peralkaline with high proportions of alkali elements relative to aluminum, or peraluminous with a higher concentration of aluminum relative to alkali elements (K, Na, Ca). Syenite. (predominantly K, Na, Ca). Syenite is not a common rock. Different syenitic rock types cover large part of the diagram. More than 90% of the total feldspar content is in the form of alkali feldspar. A true syenite (sensu stricto) is also compositionally resembling granite. The syenite intrusion shows wide variations in texture and modal compositions at outcrop scale. otite, alkali feldspar and Fe-Ti oxide, has a distinctive felted texture and is not seen elsewhere in the igneous complex. Conversely in certain conditions, large volumes of anorthite Accessory Minerals: Apatite, titanite, zircon and opaques. in Malawi in the Mulanje Mountain Forest Reserve. The dominant mineral is alkali feldspar, usually orthoclase. on beginning to cool, a fully molten silica-rich melt might precipitate its silica-containing components, leaving the silica-depleted melt to form a syenite afterwards. In New South Wales, a large syenite intruded during the The syenite is locally cut by quartz-bear-ing (up to 20%) pegmatites with sharp contacts. Less than that amount would designate the rock as a granite. This leaves a drastically reduced concentration of silica in the significant quantities include the following. Rock, South Carolina through Taxahaw, South Carolina to the Brewer and Heinrich. syenites are part of the Kola Alkaline Province. (2020). breakup of Gondwana in the Cretaceous. Homes, Hotels, Interior Decoration, As concentration of aluminum relative to alkali and earth-alkali elements E. Wm. London: DK Publishing. Producing Syenite is necessary to melt a granitic or igneous A special group of alkali syenites is characterized by the presence of a feldspathoid mineral such as nepheline, leucite, cancrinite, or sodalite (see nepheline syenite). subduction zones. Less quartz content would lead to “quartz alkali feldspar syenite”. Aggregate, Landscaping, Making natural cement, Manufacture of Magnesium and Such feldsparsoften are interleaved as perthitic components of the rock. Plagioclase feldspars may be present in small quantities, less than 10%.. Alkali feldspar granite. Plagioclase feldspars may be present in small quantities, less than 10%. https://en.wikipedia.org/w/index.php?title=Syenite&oldid=886262766, Cite this article as: Geology Science. The segregation of the silica from the melt leaves it in Most syenites are either peralkaline with high proportions Group - plutonic . A.G. Werner in 1788 applied the name in its present meaning; the Egyptian rock is a granite containing much quartz. Syenite, any of a class of intrusive igneous rocks essentially composed of an alkali feldspar and a ferromagnesian mineral. Regions where it occurs in significant quantities include the following. Syenite is an igneous rock that solidified slowly in the crust in a similar manner to granite. In Rämö, 1991 ), and could represent the parental composition to the syenites. Syenite is the plutonic equivalent of trachyte. Plagioclase feldspars may be present in small proportions, less than 10%. Most syenites are either peralkaline with high proportions of alkali elements relative to aluminum, or peraluminous with a higher concentration of aluminum relative to alkali and earth-alkali elements (predominantly K, Na, Ca). Plagioclase feldspar (P) is clearly less important than alkali deldspar. The true syenites are rocks that fit into the area annotated in red. Buildings, As if ferromagnesianminerals are present in syenite most of all, they usually occur hornblende,amphibole and clinopyroxene. This is required because nearly every state. The feldspar component of syenite is predominantly alkaline in character (usually orthoclase). Monuments, Sculpture, Small Figurines. The feldspar component of syenite is predominantly alkaline in character (usually orthoclase). A unique group of alkali syenites is characterized by the presence of a feldspathoid mineral inclusive of nepheline, leucite, cancrinite, or sodalite (see nepheline syenite). Microscopic Petrography, McGraw-Hill, 1956, This page was last edited on 10 November 2020, at 18:03. a marginally molten rock mass may retain its unmolten silica-rich components, while the molten, silica-depleted fluid cools to form a syenite. higher degrees of partial melting will liberate more calcium and sodium, which In Europe syenite may be found in parts of Switzerland, [citation needed] The “great syenite dyke” extends from Hanging remainder of the melt. Germany, Norway, Portugal, in Plovdiv, Bulgaria and in Ditrău, Romania. The Burntwood Lake alkali-feldspar syenite revisited, west-central Manitoba (part of NTS 63N8) ... two syenite units is the colour of the feldspar; however, petrographic studies are pending. In the Kola Peninsula of Russia two giant nepheline syenite At very low degrees of partial melting a silica Building Stone, As Facing Stone, Paving Stone, Garden Decoration, Office This is required because potassium is an incompatible element and tends to enter a melt first, whereas higher degrees of partial melting will liberate more calcium and sodium, which produce plagioclase, and hence a granite, adamellite or tonalite. As shown in the QAPF diagram, alkali feldspar granite contains between 20% - 60% quartz. minerals are present in syenite most of all, they usually occur hornblende, These Less quartz content would lead to "quartz alkali feldspar syenite". Syenite rock was used to make Foid syenites contain significant amount of relatively rare silicate minerals known as feldspathoids (F) which are called foids for simplicity. a state that may favour syenite formation.
2020 alkali feldspar syenite composition